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  1. <HTML>
  2. <HEAD>
  3. <TITLE>gd 1.2</TITLE>
  4. </HEAD>
  5. <BODY>
  6. <H1>gd 1.2</H1>
  7. <H2>A graphics library for fast GIF creation</H2>
  8. <H2>Follow this link to the
  9. <A HREF="http://www.boutell.com/gd/">latest version
  10. of this document</A>.</H2>
  11. <H3>Table of Contents</H3>
  12. <UL>
  13. <LI><A HREF="#notice">Credits and license terms</A>
  14. <LI><A HREF="#whatsnew1.2">What's new in version 1.2?</A>
  15. <LI><A HREF="#whatsnew1.1.1">What's new in version 1.1.1?</A>
  16. <LI><A HREF="#whatis">What is gd?</A>
  17. <LI><A HREF="#gdperl">What if I want to use Perl instead of C?</A>
  18. <LI><A HREF="#gdtcl">What if I want to use Tcl instead of C?</A>
  19. <LI><A HREF="#gdit">What if I want to use another scripting language?</A>
  20. <LI><A HREF="#required">What else do I need to use gd?</A>
  21. <LI><A HREF="#getgd">How do I get gd?</A>
  22. <LI><A HREF="#buildgd">How do I build gd?</A>
  23. <LI><A HREF="#basics">gd basics: using gd in your program</A>
  24. <LI><A HREF="#webgif">webgif: a useful example</A>
  25. <LI><A HREF="#reference">Function and type reference by category</A>
  26. <LI><A HREF="#gdformat">About the additional .gd image file format</A>
  27. <LI><A HREF="#informing"><strong>Please</strong>
  28.  tell us you're using gd!</A>
  29. <LI><A HREF="#problems">If you have problems</A>
  30. <LI><A HREF="#languages">Using gd from tcl</A></LI>
  31. <LI><A HREF="#index">Alphabetical quick index</A>
  32. </UL>
  33. <P><A HREF="http://www.boutell.com/">
  34. Up to the <EM>boutell.com, Inc. Home Page</EM></A>
  35. <A NAME="notice"><H3>Credits and license terms</A></H3>
  36. <P>
  37. gd 1.2 is copyright 1994, 1995, Quest Protein Database Center,
  38. Cold Spring Harbor Labs. Permission granted to copy and distribute
  39. this work provided that this notice remains intact. Credit
  40. for the library must be given to the Quest Protein Database Center,
  41. Cold Spring Harbor Labs, in all derived works. This does not
  42. affect your ownership of the derived work itself, and the intent
  43. is to assure proper credit for Quest, not to interfere with your
  44. use of gd. If you have questions, ask. ("Derived works"
  45. includes all programs that utilize the library. Credit must
  46. be given in user-visible documentation.)
  47. <p>
  48. gd 1.2 was written by Thomas Boutell and is currently
  49. distributed by boutell.com, Inc.
  50. <P>
  51. If you wish to release modifications to gd,
  52. please clear them first by sending email to
  53. boutell@boutell.com; if this is not done, any modified version of the gd
  54. library must be clearly labeled as such.
  55. <P>
  56. The Quest Protein Database Center is funded under Grant P41-RR02188 by
  57. the National Institutes of Health.
  58. <P>
  59. Written by <A HREF="http://sunsite.unc.edu/boutell/index.html">
  60. Thomas Boutell</A>, 2/94 - 8/95.
  61. <P>
  62. The GIF compression code is based on that found in the pbmplus
  63. utilities, which in turn is based on GIFENCOD by David Rowley. See the
  64. notice below:
  65.  
  66. <PRE>
  67. /*
  68. ** Based on GIFENCOD by David Rowley <mgardi@watdscu.waterloo.edu>.A
  69. ** Lempel-Zim compression based on "compress".
  70. **
  71. ** Modified by Marcel Wijkstra <wijkstra@fwi.uva.nl>
  72. **
  73. ** Copyright (C) 1989 by Jef Poskanzer.
  74. **
  75. ** Permission to use, copy, modify, and distribute this software and its
  76. ** documentation for any purpose and without fee is hereby granted, provided
  77. ** that the above copyright notice appear in all copies and that both that
  78. ** copyright notice and this permission notice appear in supporting
  79. ** documentation.  This software is provided "as is" without express or
  80. ** implied warranty.
  81. **
  82. ** The Graphics Interchange Format(c) is the Copyright property of
  83. ** CompuServe Incorporated.  GIF(sm) is a Service Mark property of
  84. ** CompuServe Incorporated.
  85. */
  86. </PRE>
  87. <P>
  88. <A NAME="koblas">
  89. The GIF decompression is based on that found in the pbmplus
  90. utilities, which in turn is based on GIFDECOD by David Koblas. See the
  91. notice below:
  92. <PRE>
  93. /* +-------------------------------------------------------------------+ */
  94. /* | Copyright 1990, 1991, 1993, David Koblas.  (koblas@netcom.com)    | */
  95. /* |   Permission to use, copy, modify, and distribute this software   | */
  96. /* |   and its documentation for any purpose and without fee is hereby | */
  97. /* |   granted, provided that the above copyright notice appear in all | */
  98. /* |   copies and that both that copyright notice and this permission  | */
  99. /* |   notice appear in supporting documentation.  This software is    | */
  100. /* |   provided "as is" without express or implied warranty.           | */
  101. /* +-------------------------------------------------------------------+ */
  102. </PRE>
  103. </A>
  104. <A NAME="whatis"><H3>What is gd?</H3></A>
  105. <P>
  106. gd is a graphics library. It allows your code to quickly
  107. draw images complete with lines, arcs, text, multiple
  108. colors, cut and paste from other images, and flood fills, and
  109. write out the result as a .GIF file. This is particularly
  110. useful in World Wide Web applications, where .GIF is the
  111. format used for inline images.
  112. <P>
  113. gd is not a paint program.
  114. If you are looking for a paint program, try xpaint by David
  115. Koblas, available by <A HREF="ftp://ftp.netcom.com/pub/ko/koblas">
  116. anonymous FTP</A> from ftp.netcom.com in pub/ko/koblas.
  117. (That package is for the X Window System; for the Mac and the PC, paint
  118. programs are considerably easier to find.)
  119. <P>
  120. gd does not provide for every possible desirable graphics
  121. operation. It is not necessary or desirable for gd to become
  122. a kitchen-sink graphics package, but version 1.2 incorporates
  123. most of the commonly requested features for a 2D package.
  124. Font support does need improvement, and support for the PNG
  125. graphics format will arrive in a forthcoming release.
  126. <P>
  127. <A NAME="gdperl"><H3>What if I want to use Perl instead of C?</H3></A>
  128. gd can also be used from Perl, courtesy of
  129. Lincoln Stein's
  130. <a href="http://www-genome.wi.mit.edu/ftp/pub/software/WWW/GD.html">
  131. GD.pm</a> library, which uses gd as the basis for a set of
  132. Perl 5.x classes. GD.pm is based on gd 1.1.1 but gd 1.2 should
  133. be compatible.
  134. <A NAME="gdtcl"><H3>What if I want to use Tcl instead of C?</H3></A>
  135. gd can also be used from Tcl by way of the
  136. <a href="http://guraldi.hgp.med.umich.edu/gdtcl.html">gdtcl</a>
  137. Tcl extension.
  138. <A NAME="gdit"><H3>What if I want to use another scripting language?</H3></A>
  139. There are, at the moment, at least three simple interpreters that
  140. perform gd operations. You can output the desired commands to a simple
  141. text file from whatever scripting language you prefer to use, then
  142. invoke the interpreter.
  143. <p>
  144. These packages are based on gd 1.1.1 as of this writing but should
  145. be compatible with gd 1.2 with minimal tweaking.
  146. <ul>
  147. <li><a href="http://www.demon.co.uk/3Wiz/gdit/">gdit</a>, by David
  148. Harvey-George
  149. <li><a href="http://s27w007.pswfs.gov/tgd/">tgd</a>, by Bradley K. Sherman
  150. <li><a href="http://www.unimelb.edu.au/fly/fly.html">fly</a>, by Martin Gleeson
  151. </ul>
  152. <P><A NAME="whatsnew1.2"><H3>What's new in version 1.2?</H3></A>
  153. Version 1.2 is another fine-tuning release. The next major release
  154. will after 1.2 will be version 2.0 and will feature support for
  155. the new <a href="http://sunsite.unc.edu/boutell/png.html">PNG</a>
  156. graphics format as well as improved font support. gd 1.2 does
  157. add several new fonts in the meantime.
  158. <p>
  159. Version 1.2 moves gd to ANSI standard C. Non-ANSI C compilers,
  160. such as the old SunOS 4.1.3 cc compiler, will not work. The use
  161. of pre-ANSI C led to several long-standing bugs, and the ANSI C
  162. standard has been with us for nearly ten years now. If your compiler
  163. does not support ANSI, upgrade to a recent release of your compiler,
  164. or get gcc, which is free and does support ANSI C.
  165. <P>
  166. The provided Unix Makefile has been changed to be a bit
  167. more broadly compatible, and to acknowledge the changes that
  168. may be necessary on various systems.
  169. <P>
  170. Version 1.2 also includes the following improvements:
  171. <P>
  172. <ul>
  173. <li><a href="#gdImageCopy">gdImageCopy</a> and
  174. <a href="#gdImageCopyResized">gdImageCopyResized</a> now ignore
  175. pixels which are transparent in the source image. This is allows
  176. easy copying of non-square regions, which could previously be
  177. accomplished only with brushes.
  178. <li><a href="#gdImageFilledPolygon">gdImageFilledPolygon</a>
  179. now draws horizontal edges correctly, correcting a
  180. long-standing bug. In addition, gdImageFilledPolygon copes
  181. with polygons which have several horizontal segments on
  182. the same scan line. There can still be a few pixels of
  183. disagreement between gdImagePolygon and gdImageFilledPolygon
  184. with regard to the borders of the polygon, however.
  185. <li>Several new public-domain fonts are included, courtesy of
  186. Joseph M. Orost at AT&T.
  187. <li>gd now properly recognizes an existing image with a
  188. high color slot number transparent.
  189. <li>Bugs in the <a href="#gdImageCreateFromXbm">gdImageCreateFromXbm</a>
  190. function have been corrected. Previously the function was incorrect
  191. for image widths not evenly divisible by eight.
  192. </ul>
  193. <P>
  194. <A NAME="whatsnew1.1.1"><H3>What's new in version 1.1.1?</H3></A>
  195. A fine-tuning and bug-fixing release.
  196. <P>
  197. <A HREF="#gdImageSetStyle">gdImageSetStyle</A> now copies
  198. the style array to make it easier to take advantage of
  199. the line styling feature; it is now safe to free the memory
  200. associated with your style array after setting a style
  201. (or allocate styles on the stack...).  This should not break
  202. existing code.
  203. <P>
  204. <A HREF="#webgif">webgif</A>, a small but powerful GIF-manipulating
  205. utility program, has been added as an additional code example.
  206. <P>
  207. An access macro to determine
  208. whether an image is interlaced has been added; see
  209. <A HREF="gdImageGetInterlaced">gdImageGetInterlaced</A>.
  210. <P>
  211. A better Unix Makefile, provided by Mark Scott. Note that
  212. an actual library (libgd.a) is now produced; you will want
  213. to link with this library in your own gd apps, in the same
  214. manner that gddemo and giftogd link with it. You no longer
  215. need to explicitly list the standard font files on the link
  216. line. No doubt many users have already made this enhancement
  217. themselves.
  218. <p>
  219. <strong>Important:</strong> depending on your system you may
  220. need to rewrite this Makefile. Basic code-compiling skills
  221. are expected for the use of this library.
  222. <P>
  223. <A HREF="#koblas">David Koblas</A> has been given proper credit
  224. for the original GIF decoding routine; previously I erroneously
  225. credited David Rowley with both the encoder and the decoder.
  226. <P>
  227. <A HREF="#gdImageFill">gdImageFill</A> no longer crashes when
  228. attempting to fill a region with the color it already has.
  229. Also, attempting to fill a region with the special color
  230. <A HREF="#gdTiled">gdTiled</A> no longer crashes.
  231. <P>
  232. However, filling a region with a transparent tile has been
  233. forbidden (gdImageFill simply draws nothing in this case).
  234. Otherwise, gd would not know when to stop drawing
  235. without the use of an additional image to keep track of
  236. which pixels have been visited.
  237. <P>
  238. Invoking <A HREF="#gdImageFillToBorder">gdImageFillToBorder</A>
  239. with a special border color such as <A HREF="#gdTiled">gdTiled</A>
  240. now fails, for similar reasons. However, the color
  241. you are filling <em>with</em> can be <A HREF="#gdTiled">gdTiled</A>,
  242. even if it is transparent. See the discussion of
  243. <A HREF="#gdImageFillToBorder">gdImageFillToBorder</A> for
  244. additional caveats.
  245. <P>
  246. Many documentation fixes.
  247. <P>
  248. <A NAME="whatsnew1.1"><H3>What's new in version 1.1?</H3></A>
  249. <P>
  250. <UL>
  251. <LI><A HREF="#gdImageFilledPolygon">Polygon fills</A></LI>
  252. <LI><A HREF="#gdImageSetStyle">Line styling</A></LI>
  253. <LI><A HREF="#gdImageSetBrush">"Brushing" of lines with a brush image</A></LI>
  254. <LI><A HREF="#gdImageSetTile">Tiling of polygon, rectangle and flood-fills</A>
  255. <LI><A HREF="#gdImageInterlace">Interlaced GIFs for gradual fade-in</A></LI>
  256. </LI>
  257. <LI>Macros to access <A HREF="#gdImageSX">image size</A>, etc.</LI>
  258. </UL>
  259. <P>
  260. <A NAME="required"><H3>What else do I need to use gd?</H3></A>
  261. <P>
  262. To use gd, you will need an ANSI C compiler. Any full-ANSI-standard
  263. C compiler should be adequate, although those with PCs will need to replace
  264. the Makefile with one of their own. <strong>The cc compiler released
  265. with SunOS 4.1.3 is not an ANSI C compiler. Get gcc, which is freely
  266. available. See the Sun-related newsgroups for more information.</strong>
  267. <P>
  268. You will also want a GIF viewer, if you do not already have
  269. one for your system, since you will need a good way to check the
  270. results of your work. lview is a good package for
  271. Windows PCs; xv is a good package for X11. There are
  272. GIF viewers available for every graphics-capable
  273. computer out there, so consult newsgroups relevant to
  274. your particular system.
  275. <P>
  276. <A NAME="getgd"><H3>How do I get gd?</H3></A>
  277. <P>
  278. You can
  279. <A HREF="http://www.boutell.com/gd/gd1.2.tar.Z">
  280. fetch gd as a compressed tar file</A> from www.boutell.com.
  281. <A NAME="buildgd"><H3>How do I build gd?</H3></A>
  282. <P>
  283. In order to build gd, first uncompress and untar the gd.tar file with the
  284. following commands:
  285. <P>
  286. <em>Note:</em> if you have a non-Unix system, you will need
  287. to acquire versions of "uncompress" and "tar" suitable for
  288. your system. Both have been ported to PC and Mac
  289. environments. Consult newsgroups relevant to your
  290. particular system.
  291. <PRE>
  292. uncompress gd1.2.tar.Z
  293. tar -xf gd1.2.tar
  294. </PRE>
  295. This will create the directory "gd1.2" beneath the current
  296. directory.
  297. <P>
  298. cd to this directory and examine the Makefile, which you may need
  299. to change slightly depending on your installation (or more than
  300. slightly for a Windows or Mac environment).
  301. <P>
  302. Now, to build the demonstration program, just type "make gddemo"
  303. if you are working in a command-line environment. If all goes well,
  304. the program "gddemo" will be compiled and linked without incident.
  305. Depending on your system you may need to edit the Makefile.
  306. Understanding the basic techniques of compiling and linking
  307. programs on your system is up to you.
  308. <P>
  309. You have now built a demonstration program which shows off
  310. the capabilities of gd. To see it in action, type
  311. "gddemo".
  312. <P>
  313. gddemo should execute without incident, creating the file
  314. demoout.gif. (Note there is also a file named demoin.gif,
  315. which is provided in the package as part of the demonstration.)
  316. <P>
  317. Display demoout.gif in your GIF viewer. The image should
  318. be 128x128 pixels and should contain an image of the
  319. space shuttle with the word "hi" written in the upper
  320. left corner twice (once across and once upwards),
  321. an arc in the middle and an oval intersecting the arc
  322. (these are somewhat faint).
  323. <p>
  324. In addition, a diagonal line made up of tiny space shuttle
  325. images should appear from the lower left to the upper
  326. right corner.   A blue frame with green interior trim should
  327. surround the picture.
  328. <P>
  329. (If you are missing the demoin.gif file, the other items
  330. should appear anyway.)
  331. <P>
  332. Look at demoin.gif to see the original space shuttle
  333. image which was scaled and copied into the output image.
  334. <P>
  335. <A NAME="basics"><H3>gd basics: using gd in your program</H3></A>
  336. gd lets you create GIF images on the fly. To use gd in your
  337. program, include the file gd.h, and link with the libgd.a
  338. library produced by "make libgd.a", under Unix. You will
  339. need to adapt the makefile for your needs if you are using
  340. a non-Unix operating system, but this is very straightforward.
  341. <P>
  342. If you want to use the provided fonts, include
  343. gdfontt.h, gdfonts.h, gdfontmb.h, gdfontl.h and/or gdfontg.h. If you
  344. are not using the provided Makefile and/or a library-based approach, be
  345. sure to include the source modules as well in your
  346. project. (They may be too large for 16-bit memory models,
  347. that is, 16-bit DOS and Windows.)
  348. <P>
  349. Here is a short example program. <strong>(For a more advanced example,
  350. see gddemo.c, included in the distribution. gddemo.c is NOT the same program;
  351. it demonstrates additional features!)</strong>
  352. <P>
  353. <PRE>
  354. /* Bring in gd library functions */
  355. #include "gd.h"
  356.  
  357. /* Bring in standard I/O so we can output the GIF to a file */
  358. #include &lt;stdio.h&gt;
  359.  
  360. int main() {
  361.         /* Declare the image */
  362.         <A HREF="#gdImagePtr">gdImagePtr</A> im;
  363.         /* Declare an output file */
  364.         FILE *out;
  365.         /* Declare color indexes */
  366.         int black;
  367.         int white;
  368.  
  369.         /* Allocate the image: 64 pixels across by 64 pixels tall */
  370.         im = <A HREF="#gdImageCreate">gdImageCreate</A>(64, 64);
  371.  
  372.         /* Allocate the color black (red, green and blue all minimum).
  373.                 Since this is the first color in a new image, it will
  374.                 be the background color. */
  375.         black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  376.  
  377.         /* Allocate the color white (red, green and blue all maximum). */
  378.         white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  379.        
  380.         /* Draw a line from the upper left to the lower right,
  381.                 using white color index. */
  382.         <A HREF="#gdImageLine">gdImageLine</A>(im, 0, 0, 63, 63, white);       
  383.  
  384.         /* Open a file for writing. "wb" means "write binary", important
  385.                 under MSDOS, harmless under Unix. */
  386.         out = fopen("test.gif", "wb");
  387.  
  388.         /* Output the image to the disk file. */
  389.         <A HREF="#gdImageGif">gdImageGif</A>(im, out); 
  390.  
  391.         /* Close the file. */
  392.         fclose(out);
  393.  
  394.         /* Destroy the image in memory. */
  395.         <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  396. }
  397. </PRE>
  398. When executed, this program creates an image, allocates
  399. two colors (the first color allocated becomes the background
  400. color), draws a diagonal line (note that 0, 0 is the upper
  401. left corner), writes the image to a GIF file, and
  402. destroys the image.
  403. <P>
  404. The above example program should
  405. give you an idea of how the package works.
  406. gd provides many additional functions, which are listed
  407. in the following reference chapters, complete with code
  408. snippets demonstrating each. There is also an
  409. <A HREF="#index">alphabetical index</A>.
  410. <H3><A NAME="webgif">Webgif: a more powerful gd example</A></H3>
  411. Webgif is a simple utility program to manipulate GIFs from the
  412. command line. It is written for Unix and similar command-line
  413. systems, but should be easily adapted for other environments.
  414. Webgif allows you to set transparency and interlacing and
  415. output interesting information about the GIF in question.
  416. <P>
  417. webgif.c is provided in the distribution. Unix users can
  418. simply type "make webgif" to compile the program. Type
  419. "webgif" with no arguments to see the available options.
  420. A discussion of the code follows.
  421. <PRE>
  422. /* Bring in the gd library functions */
  423. #include "gd.h"
  424.  
  425. /* Bring in standard I/O and string manipulation functions */
  426. #include <stdio.h>
  427. #include <string.h>
  428.  
  429. int main(argc, argv)
  430.         int argc;
  431.         char *argv[];
  432. {
  433.         FILE *in;
  434.         FILE *out;
  435.         /* Declare our image pointer */
  436.         <A HREF="#gdImagePtr">gdImagePtr</A> im = 0;
  437.         int i;
  438.       /* We'll clear 'no' once we know the user has made a
  439.                 reasonable request. */
  440.         int no = 1;
  441.         /* We'll set 'write' once we know the user's request
  442.                 requires that the image be written back to disk. */
  443.         int write = 0;
  444.         /* C programs always get at least one argument; we want at
  445.                 least one more (the image), more in practice. */
  446.         if (argc < 2) {
  447.                 no = 1;
  448.                 goto usage;
  449.         }
  450.         /* The last argument should be the image. Open the file. */
  451.         in = fopen(argv[argc-1], "rb");
  452.         if (!in) {
  453.                 fprintf(stderr,
  454.                         "Error: can't open file %s.\n", argv[argc-1]);
  455.         }
  456.         /* Now load the image. */      
  457.         im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  458.         fclose(in);
  459.         /* If the load failed, it must not be a GIF file. */
  460.         if (!im) {
  461.                 fprintf(stderr,
  462.                         "Error: %s is not a valid gif file.\n", argv[1]);
  463.                 exit(1);       
  464.         }
  465.         /* Consider each argument in turn. */
  466.         for (i=1; (i < (argc-1)); i++) {
  467.                 /* -i turns on and off interlacing. */
  468.                 if (!strcmp(argv[i], "-i")) {
  469.                         if (i == (argc-2)) {
  470.                                 fprintf(stderr,
  471.                                 "Error: -i specified without y or n.\n");
  472.                                 no = 1;
  473.                                 goto usage;
  474.                         }
  475.                         if (!strcmp(argv[i+1], "y")) {
  476.                                 /* Set interlace. */
  477.                                 <A HREF="#gdImageInterlace">gdImageInterlace</A>(im, 1);
  478.                         } else if (!strcmp(argv[i+1], "n")) {
  479.                                 /* Clear interlace. */
  480.                                 <A HREF="#gdImageInterlace">gdImageInterlace</A>(im, 0);
  481.                         } else {
  482.                                 fprintf(stderr,
  483.                                 "Error: -i specified without y or n.\n");
  484.                                 no = 1;
  485.                                 goto usage;
  486.                         }
  487.                         i++;
  488.                         no = 0;
  489.                         write = 1;
  490.                 } else if (!strcmp(argv[i], "-t")) {
  491.                         /* Set transparent index (or none). */
  492.                         int index;
  493.                         if (i == (argc-2)) {
  494.                                 fprintf(stderr,
  495.                 "Error: -t specified without a color table index.\n");
  496.                                 no = 1;
  497.                                 goto usage;
  498.                         }
  499.                         if (!strcmp(argv[i+1], "none")) {
  500.                                 /* -1 means not transparent. */
  501.                                 <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A>(im, -1);
  502.                         } else {
  503.                                 /* OK, get an integer and set the index. */
  504.                                 index = atoi(argv[i+1]);
  505.                                 <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A>(im, index);
  506.                         }
  507.                         i++;
  508.                         write = 1;
  509.                         no = 0;
  510.                 } else if (!strcmp(argv[i], "-l")) {
  511.                         /* List the colors in the color table. */
  512.                         int j;
  513.                         /* Tabs used below. */
  514.                         printf("Index   Red     Green   Blue\n");
  515.                         for (j=0; (j < <A HREF="#gdImageColorsTotal">gdImageColorsTotal</A>(im)); j++) {
  516.                                 /* Use access macros to learn colors. */
  517.                                 printf("%d      %d      %d      %d\n",
  518.                                         j,
  519.                                         <A HREF="#gdImageRed">gdImageRed</A>(im, j),
  520.                                         <A HREF="#gdImageGreen">gdImageGreen</A>(im, j),
  521.                                         <A HREF="#gdImageBlue">gdImageBlue</A>(im, j));
  522.                         }
  523.                         no = 0;
  524.                 } else if (!strcmp(argv[i], "-d")) {
  525.                         /* Output dimensions, etc. */
  526.                         int t;
  527.                         printf("Width: %d Height: %d Colors: %d\n",
  528.                                 <A HREF="#gdImageSX">gdImageSX</A>(im), <A HREF="#gdImageSY">gdImageSY</A>(im),
  529.                                 <A HREF="#gdImageColorsTotal">gdImageColorsTotal</A>(im));
  530.                         t = <A HREF="#gdImageGetTransparent">gdImageGetTransparent</A>(im);
  531.                         if (t != (-1)) {
  532.                                 printf("Transparent index: %d\n", t);
  533.                         } else {
  534.                                 /* -1 means the image is not transparent. */
  535.                                 printf("Transparent index: none\n");
  536.                         }
  537.                         if (<A HREF="#gdImageGetInterlaced">gdImageGetInterlaced</A>(im)) {
  538.                                 printf("Interlaced: yes\n");   
  539.                         } else {
  540.                                 printf("Interlaced: no\n");    
  541.                         }
  542.                         no = 0;
  543.                 } else {
  544.                         fprintf(stderr, "Unknown argument: %s\n", argv[i]);
  545.                         break; 
  546.                 }
  547.         }
  548. usage:
  549.         if (no) {
  550.                 /* If the command failed, output an explanation. */
  551.                 fprintf(stderr,
  552.         "Usage: webgif [-i y|n ] [-l] [-t index|off ] [-d] gifname.gif\n");
  553.                 fprintf(stderr,
  554.         "Where -i controls interlace (specify y or n for yes or no),\n");
  555.                 fprintf(stderr,
  556.         "-l outputs a table of color indexes, -t sets the specified\n");
  557.                 fprintf(stderr,
  558.         "color index (0-255 or none) to be the transparent color, and\n");
  559.                 fprintf(stderr,
  560.         "-d reports the dimensions and other characteristics of the image.\n");
  561.                 fprintf(stderr,
  562.         "Note: you may wish to pipe to \"more\" when using the -l option.\n");
  563.         }
  564.         if (write) {
  565.                 /* Open a temporary file. */
  566.                 out = fopen("temp.tmp", "wb");
  567.                 if (!out) {
  568.                         fprintf(stderr,
  569.                                 "Unable to write to temp.tmp -- exiting\n");
  570.                         exit(1);
  571.                 }
  572.                 /* Write the new gif. */
  573.                 <A HREF="#gdImageGif">gdImageGif</A>(im, out);
  574.                 fclose(out);
  575.                 /* Erase the old gif. */
  576.                 unlink(argv[argc-1]);
  577.                 /* Rename the new to the old. */
  578.                 rename("temp.tmp", argv[argc-1]);
  579.         }
  580.         /* Delete the image from memory. */
  581.         if (im) {
  582.                 <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  583.         }
  584.         /* All's well that ends well. */
  585.         return 0;
  586. }
  587. </PRE>
  588. <H2><A NAME="reference">Function and type reference</A></H2>
  589. <UL>
  590. <LI><A HREF="#types">Types</A></LI>
  591. <LI><A HREF="#creating">Image creation, destruction, loading and saving</A></LI>
  592. <LI><A HREF="#drawing">Drawing, styling, brushing, tiling and
  593. filling functions</A></LI>
  594. <LI><A HREF="#query">Query functions (not color-related)</A></LI>
  595. <LI><A HREF="#fonts">Font and text-handling functions</A></LI>
  596. <LI><A HREF="#colors">Color handling functions</A></LI>
  597. <LI><A HREF="#copying">Copying and resizing functions</A></LI>
  598. <LI><A HREF="#misc">Miscellaneous Functions</A></LI>
  599. <LI><A HREF="#constants">Constants</A></LI>
  600. </UL>
  601. <H3><A NAME="types">Types</A></H3>
  602. <DL>
  603. <DT><A NAME="gdImage"><code>gdImage</code><strong>(TYPE)</strong></A>
  604. <DD>
  605. The data structure in which gd stores images. <A HREF="#gdImageCreate">
  606. gdImageCreate</A> returns
  607. a pointer to this type, and the other functions expect to receive
  608. a pointer to this type as their first argument. You may
  609. read the members <code>sx</code> (size on X axis),
  610. <code>sy</code> (size on Y axis), <code>colorsTotal</code>
  611. (total colors), <code>red</code> (red component of colors;
  612. an array of 256 integers between 0 and 255), <code>green</code>
  613. (green component of colors, as above), <code>blue</code>
  614. (blue component of colors, as above), and <code>transparent</code>
  615. (index of transparent color, -1 if none); please do so
  616. using the macros provided. Do NOT set the members directly
  617. from your code; use the functions provided.
  618. <PRE>
  619. typedef struct {
  620.         unsigned char ** pixels;
  621.         int sx;
  622.         int sy;
  623.         int colorsTotal;
  624.         int red[gdMaxColors];
  625.         int green[gdMaxColors];
  626.         int blue[gdMaxColors];
  627.         int open[gdMaxColors];
  628.         int transparent;
  629. } gdImage;
  630. </PRE>
  631. <DT><A NAME="gdImagePtr">gdImagePtr</A> <strong>(TYPE)</strong>
  632. <DD>
  633. A pointer to an image structure. <A HREF="#gdImageCreate">gdImageCreate</A>
  634. returns this type, and the other functions expect it as the first
  635. argument.
  636. <DT><A NAME="gdFont">gdFont</A> <strong>(TYPE)</strong>
  637. <DD>
  638. A font structure. Used to declare the characteristics of a font.
  639. Plese see the files gdfontl.c and gdfontl.h for an example of the
  640. proper declaration of this structure. You can provide your
  641. own font data by providing such a structure and the associated
  642. pixel array. You can determine the width and height of a single
  643. character in a font by examining the w and h members of the
  644. structure. If you will not be creating your own fonts, you will
  645. not need to concern yourself with the rest of the components of this
  646. structure.
  647. <PRE>
  648. typedef struct {
  649.         /* # of characters in font */
  650.         int nchars;
  651.         /* First character is numbered... (usually 32 = space) */
  652.         int offset;
  653.         /* Character width and height */
  654.         int w;
  655.         int h;
  656.         /* Font data; array of characters, one row after another.
  657.                 Easily included in code, also easily loaded from
  658.                 data files. */
  659.         char *data;
  660. } gdFont;
  661. </PRE>
  662. <DT><A NAME="gdFontPtr">gdFontPtr</A> <strong>(TYPE)</strong>
  663. <DD>
  664. A pointer to a font structure. Text-output functions expect these
  665. as their second argument, following the <A HREF="#gdImagePtr">
  666. gdImagePtr</A> argument. Two such pointers are declared in the
  667. provided include files gdfonts.h and gdfontl.h.
  668. <DT><A NAME="gdPoint">gdPoint</A> <strong>(TYPE)</strong>
  669. <DD>
  670. Represents a point in the coordinate space of the image; used
  671. by <A HREF="#gdImagePolygon">gdImagePolygon</A> and
  672. <A HREF="#gdImageFilledPolygon">gdImageFilledPolygon</A>.
  673. <PRE>
  674. typedef struct {
  675.        int x, y;
  676. } gdPoint, *gdPointPtr;
  677. </PRE>
  678. <DT><A NAME="gdPointPtr">gdPointPtr</A> <strong>(TYPE)</strong>
  679. <DD>
  680. A pointer to a <A HREF="#gdPoint">gdPoint</A> structure; passed
  681. as an argument to <A HREF="#gdImagePolygon">gdImagePolygon</A>
  682. and <A HREF="#gdImageFilledPolygon">gdImageFilledPolygon</A>.
  683. </DL>
  684. <H3><A NAME="creating">Image creation, destruction, loading and saving</A></H3>
  685. <DL>
  686. <DT><A NAME="gdImageCreate">gdImageCreate(sx, sy)</A>
  687. <strong>(FUNCTION)</strong>
  688. <DD>
  689. gdImageCreate is called to create images. Invoke gdImageCreate
  690. with the x and y dimensions of the desired image. gdImageCreate
  691. returns a <A HREF="#gdImagePtr">gdImagePtr</A> to the new image, or
  692. NULL if unable to
  693. allocate the image. The image must eventually be destroyed
  694. using <A HREF="#gdImageDestroy">gdImageDestroy()</A>.
  695. <PRE>
  696. ... inside a function ...
  697. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  698. im = gdImageCreate(64, 64);
  699. /* ... Use the image ... */
  700. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  701. </PRE>
  702. <DT><A NAME="gdImageCreateFromGif">gdImageCreateFromGif(FILE *in)</A>
  703. <strong>(FUNCTION)</strong>
  704. <DD>
  705. gdImageCreateFromGif is called to load images from GIF format files.
  706. Invoke gdImageCreateFromGif with an already opened pointer to a file
  707. containing the desired image.
  708. gdImageCreateFromGif
  709. returns a <A HREF="#gdImagePtr">gdImagePtr</A> to the new image, or NULL
  710. if unable to load the image (most often because the file is corrupt or
  711. does not contain a GIF image). gdImageCreateFromGif does <em>not</em>
  712. close the file. You can inspect the sx and sy members of the
  713. image to determine its size. The image must eventually be destroyed
  714. using <A HREF="#gdImageDestroy">gdImageDestroy()</A>.
  715. <PRE>
  716. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  717. ... inside a function ...
  718. FILE *in;
  719. in = fopen("mygif.gif", "rb");
  720. im = gdImageCreateFromGif(in);
  721. fclose(in);
  722. /* ... Use the image ... */
  723. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  724. </PRE>
  725. <DT><A NAME="gdImageCreateFromGd">gdImageCreateFromGd(FILE *in)</A>
  726. <strong>(FUNCTION)</strong>
  727. <DD>
  728. gdImageCreateFromGd is called to load images from gd format files.
  729. Invoke gdImageCreateFromGd
  730. with an already opened pointer to a file containing the desired image
  731. in the <A HREF="#gdformat">gd file format</A>, which is specific to
  732. gd and intended for very fast loading. (It is <em>not</em> intended for
  733. compression; for compression, use GIF.)
  734. gdImageCreateFromGd
  735. returns a <A HREF="#gdImagePtr">gdImagePtr</A> to the new image, or NULL
  736. if unable to load the image (most often because the file is corrupt or
  737. does not contain a gd format image). gdImageCreateFromGd does <em>not</em>
  738. close the file. You can inspect the sx and sy members of the
  739. image to determine its size. The image must eventually be destroyed
  740. using <A HREF="#gdImageDestroy">gdImageDestroy()</A>.
  741. <PRE>
  742. ... inside a function ...
  743. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  744. FILE *in;
  745. in = fopen("mygd.gd", "rb");
  746. im = gdImageCreateFromGd(in);
  747. fclose(in);
  748. /* ... Use the image ... */
  749. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  750. </PRE>
  751. <DT><A NAME="gdImageCreateFromXbm">gdImageCreateFromXbm(FILE *in)</A>
  752. <strong>(FUNCTION)</strong>
  753. <DD>
  754. gdImageCreateFromXbm is called to load images from X bitmap format
  755. files. Invoke gdImageCreateFromXbm
  756. with an already opened pointer to a file containing the desired image.
  757. gdImageCreateFromXbm
  758. returns a <A HREF="#gdImagePtr">gdImagePtr</A> to the new image, or NULL
  759. if unable to load the image (most often because the file is corrupt or
  760. does not contain an X bitmap format image). gdImageCreateFromXbm does
  761. <em>not</em> close the file. You can inspect the sx and sy members of the
  762. image to determine its size. The image must eventually be destroyed
  763. using <A HREF="#gdImageDestroy">gdImageDestroy()</A>.
  764. <PRE>
  765. ... inside a function ...
  766. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  767. FILE *in;
  768. in = fopen("myxbm.xbm", "rb");
  769. im = gdImageCreateFromXbm(in);
  770. fclose(in);
  771. /* ... Use the image ... */
  772. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  773. </PRE>
  774. <DT><A NAME="gdImageDestroy">gdImageDestroy(gdImagePtr im)</A> <STRONG>(FUNCTION)</STRONG>
  775. <DD>gdImageDestroy is used to free the memory associated with
  776. an image. It is important to invoke gdImageDestroy before
  777. exiting your program or assigning a new image to
  778. a <A HREF="#gdImagePtr">gdImagePtr</A> variable.
  779. <PRE>
  780. ... inside a function ...
  781. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  782. im = <A HREF="#gdImageCreate">gdImageCreate</A>(10, 10);
  783. /* ... Use the image ... */
  784. /* Now destroy it */
  785. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  786. </PRE>
  787. <DT><A NAME="gdImageGif">
  788. void gdImageGif(gdImagePtr im, FILE *out)</A>
  789. <STRONG>(FUNCTION)</STRONG>
  790. <DD>
  791. gdImageGif outputs the specified image to the specified
  792. file in GIF format. The file must be open for writing. Under MSDOS,
  793. it is important to use "wb" as opposed to simply "w"
  794. as the mode when opening the file, and under Unix there
  795. is no penalty for doing so. gdImageGif does <em>not</em>
  796. close the file; your code must do so.
  797. <PRE>
  798. ... inside a function ...
  799. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  800. int black, white;
  801. FILE *out;
  802. /* Create the image */
  803. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  804. /* Allocate background */
  805. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);
  806. /* Allocate drawing color */
  807. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0);
  808. /* Draw rectangle */
  809. <A HREF="#gdImageRectangle">gdImageRectangle</A>(im, 0, 0, 99, 99, black);
  810. /* Open output file in binary mode */
  811. out = fopen("rect.gif", "wb");
  812. /* Write GIF */
  813. gdImageGif(im, out);
  814. /* Close file */
  815. fclose(out);
  816. /* Destroy image */
  817. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  818. </PRE>
  819. <DT><A NAME="gdImageGd">
  820. void gdImageGd(gdImagePtr im, FILE *out)</A>
  821. <STRONG>(FUNCTION)</STRONG>
  822. <DD>
  823. gdImageGd outputs the specified image to the specified
  824. file in the <A HREF="#gdformat">gd image format</A>. The file must
  825. be open for writing. Under MSDOS, it is important to use "wb" as
  826. opposed to simply "w" as the mode when opening the file, and under
  827. Unix there is no penalty for doing so. gdImageGif does <em>not</em>
  828. close the file; your code must do so.
  829. <P>
  830. The gd image format is intended for fast reads and writes of
  831. images your program will need frequently to build other
  832. images. It is <em>not</em> a compressed format, and is not intended
  833. for general use.
  834. <PRE>
  835. ... inside a function ...
  836. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  837. int black, white;
  838. FILE *out;
  839. /* Create the image */
  840. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  841. /* Allocate background */
  842. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);
  843. /* Allocate drawing color */
  844. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0);
  845. /* Draw rectangle */
  846. <A HREF="#gdImageRectangle">gdImageRectangle</A>(im, 0, 0, 99, 99, black);
  847. /* Open output file in binary mode */
  848. out = fopen("rect.gd", "wb");
  849. /* Write gd format file */
  850. gdImageGd(im, out);
  851. /* Close file */
  852. fclose(out);
  853. /* Destroy image */
  854. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  855. </PRE>
  856. </DL>
  857. <H3><A NAME="drawing">Drawing Functions</A></H3>
  858. <DL>
  859. <DT><A NAME="gdImageSetPixel">void gdImageSetPixel(gdImagePtr im, int x, int y, int color)</A> <STRONG>(FUNCTION)</STRONG>
  860. <DD>gdImageSetPixel sets a pixel to a particular color index. Always use
  861. this function or one of the other drawing functions to access pixels;
  862. do not access the pixels of the <A HREF="#gdImage">gdImage</A> structure
  863. directly.
  864. <PRE>
  865. ... inside a function ...
  866. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  867. int black;
  868. int white;
  869. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  870. /* Background color (first allocated) */
  871. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  872. /* Allocate the color white (red, green and blue all maximum). */
  873. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  874. /* Set a pixel near the center. */
  875. gdImageSetPixel(im, 50, 50, white);
  876. /* ... Do something with the image, such as saving it to a file... */
  877. /* Destroy it */
  878. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  879. </PRE>
  880. <DT><A NAME="gdImageLine">void gdImageLine(gdImagePtr im, int x1, int y1, int x2, int y2, int color)</A>
  881. <STRONG>(FUNCTION)</STRONG>
  882. <DD>
  883. gdImageLine is used to draw a line between two endpoints (x1,y1 and x2, y2).
  884. The line is drawn using the color index specified. Note that the color
  885. index can be an actual color returned by <A HREF="#gdImageColorAllocate">
  886. gdImageColorAllocate</A> or one of <A HREF="#gdStyled">gdStyled</A>,
  887. <A HREF="#gdBrushed">gdBrushed</A> or <A HREF="#gdStyledBrushed">
  888. gdStyledBrushed</A>.
  889. <PRE>
  890. ... inside a function ...
  891. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  892. int black;
  893. int white;
  894. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  895. /* Background color (first allocated) */
  896. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  897. /* Allocate the color white (red, green and blue all maximum). */
  898. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  899. /* Draw a line from the upper left corner to the lower right corner. */
  900. gdImageLine(im, 0, 0, 99, 99, white);
  901. /* ... Do something with the image, such as saving it to a file... */
  902. /* Destroy it */
  903. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  904. </PRE>
  905. <DT><A NAME="gdImageDashedLine">void gdImageDashedLine(gdImagePtr im, int x1, int y1, int x2, int y2, int color)</A>
  906. <STRONG>(FUNCTION)</STRONG>
  907. <DD>
  908. gdImageDashedLine is provided <strong>solely for backwards compatibility
  909. </strong> with gd 1.0. New programs should draw dashed lines using
  910. the normal <A HREF="#gdImageLine">gdImageLine</A> function and the
  911. new <A HREF="#gdImageSetStyle">gdImageSetStyle</A> function.
  912. <P>
  913. gdImageDashedLine is used to draw a dashed line between two endpoints
  914. (x1,y1 and x2, y2).
  915. The line is drawn using the color index specified. The portions of the line
  916. that are not drawn are left transparent so the background is visible.
  917. <PRE>
  918. ... inside a function ...
  919. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  920. int black;
  921. int white;
  922. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  923. /* Background color (first allocated) */
  924. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  925. /* Allocate the color white (red, green and blue all maximum). */
  926. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  927. /* Draw a dashed line from the upper left corner to the lower right corner. */
  928. gdImageDashedLine(im, 0, 0, 99, 99);
  929. /* ... Do something with the image, such as saving it to a file... */
  930. /* Destroy it */
  931. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  932. </PRE>
  933. <DT><A NAME="gdImagePolygon">void gdImagePolygon(gdImagePtr im, gdPointPtr points, int pointsTotal, int color)</A>
  934. <STRONG>(FUNCTION)</STRONG>
  935. <DD>
  936. gdImagePolygon is used to draw a polygon with the verticies
  937. (at least 3) specified, using the color index specified.
  938. See also <A HREF="#gdImageFilledPolygon">gdImageFilledPolygon</A>.
  939. <PRE>
  940. ... inside a function ...
  941. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  942. int black;
  943. int white;
  944. /* Points of polygon */
  945. <A HREF="#gdPoint">gdPoint</A> points[3];
  946. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  947. /* Background color (first allocated) */
  948. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  949. /* Allocate the color white (red, green and blue all maximum). */
  950. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  951. /* Draw a triangle. */
  952. points[0].x = 50;
  953. points[0].y = 0;
  954. points[1].x = 99;
  955. points[1].y = 99;
  956. points[2].x = 0;
  957. points[2].y = 99;
  958. gdImagePolygon(im, points, 3, white);
  959. /* ... Do something with the image, such as saving it to a file... */
  960. /* Destroy it */
  961. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  962. </PRE>
  963. <DT><A NAME="gdImageRectangle">void gdImageRectangle(gdImagePtr im, int x1, int y1, int x2, int y2, int color)</A>
  964. <STRONG>(FUNCTION)</STRONG>
  965. <DD>
  966. gdImageRectangle is used to draw a rectangle with the two corners
  967. (upper left first, then lower right) specified, using the
  968. color index specified.
  969. <PRE>
  970. ... inside a function ...
  971. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  972. int black;
  973. int white;
  974. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  975. /* Background color (first allocated) */
  976. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  977. /* Allocate the color white (red, green and blue all maximum). */
  978. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  979. /* Draw a rectangle occupying the central area. */
  980. gdImageRectangle(im, 25, 25, 74, 74, white);
  981. /* ... Do something with the image, such as saving it to a file... */
  982. /* Destroy it */
  983. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  984. </PRE>
  985. <DT><A NAME="gdImageFilledPolygon">void gdImageFilledPolygon(gdImagePtr im, gdPointPtr points, int pointsTotal, int color)</A>
  986. <STRONG>(FUNCTION)</STRONG>
  987. <DD>
  988. gdImageFilledPolygon is used to fill a polygon with the verticies
  989. (at least 3) specified, using the color index specified.
  990. See also <A HREF="#gdImageFilledPolygon">gdImagePolygon</A>.
  991. <PRE>
  992. ... inside a function ...
  993. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  994. int black;
  995. int white;
  996. int red;
  997. /* Points of polygon */
  998. <A HREF="#gdPoint">gdPoint</A> points[3];
  999. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1000. /* Background color (first allocated) */
  1001. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1002. /* Allocate the color white (red, green and blue all maximum). */
  1003. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1004. /* Allocate the color red. */
  1005. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1006. /* Draw a triangle. */
  1007. points[0].x = 50;
  1008. points[0].y = 0;
  1009. points[1].x = 99;
  1010. points[1].y = 99;
  1011. points[2].x = 0;
  1012. points[2].y = 99;
  1013. /* Paint it in white */
  1014. gdImageFilledPolygon(im, points, 3, white);
  1015. /* Outline it in red; must be done second */
  1016. <A HREF="#gdImagePolygon">gdImagePolygon</A>(im, points, 3, red);
  1017. /* ... Do something with the image, such as saving it to a file... */
  1018. /* Destroy it */
  1019. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1020. </PRE>
  1021. <DT><A NAME="gdImageFilledRectangle">void gdImageFilledRectangle(gdImagePtr im, int x1, int y1, int x2, int y2, int color)</A>
  1022. <STRONG>(FUNCTION)</STRONG>
  1023. <DD>
  1024. gdImageFilledRectangle is used to draw a solid rectangle with the two corners
  1025. (upper left first, then lower right) specified, using the
  1026. color index specified.
  1027. <PRE>
  1028. ... inside a function ...
  1029. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1030. int black;
  1031. int white;
  1032. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1033. /* Background color (first allocated) */
  1034. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1035. /* Allocate the color white (red, green and blue all maximum). */
  1036. white = <A HREF="#gdImageColorAllocate">int gdImageColorAllocate</A>(im, 255, 255, 255);       
  1037. /* Draw a filled rectangle occupying the central area. */
  1038. gdImageFilledRectangle(im, 25, 25, 74, 74, white);
  1039. /* ... Do something with the image, such as saving it to a file... */
  1040. /* Destroy it */
  1041. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1042. </PRE>
  1043. <DT><A NAME="gdImageArc">void gdImageArc(gdImagePtr im, int cx, int cy, int w, int h, int s, int e, int color)</A>
  1044. <STRONG> (FUNCTION)</STRONG>
  1045. <DD>
  1046. gdImageArc is used to draw a partial ellipse centered at the given point,
  1047. with the specified width and height in pixels. The arc begins at
  1048. the position in degrees specified by <code>s</code> and ends at
  1049. the position specified by <code>e</code>. The arc is drawn in
  1050. the color specified by the last argument. A circle can be drawn
  1051. by beginning from 0 degrees and ending at 360 degrees, with
  1052. width and height being equal. e must be greater than s. Values greater
  1053. than 360 are interpreted modulo 360.
  1054. <PRE>
  1055. ... inside a function ...
  1056. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1057. int black;
  1058. int white;
  1059. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 50);
  1060. /* Background color (first allocated) */
  1061. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1062. /* Allocate the color white (red, green and blue all maximum). */
  1063. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1064. /* Inscribe an ellipse in the image. */
  1065. gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
  1066. /* ... Do something with the image, such as saving it to a file... */
  1067. /* Destroy it */
  1068. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1069. </PRE>
  1070. <DT><A NAME="gdImageFillToBorder">void gdImageFillToBorder(gdImagePtr im, int x, int y, int border, int color)
  1071. <STRONG> (FUNCTION)</STRONG>
  1072. <DD>
  1073. gdImageFillToBorder floods a portion of the image with the specified
  1074. <code>color</code>, beginning at the specified point and stopping at
  1075. the specified <code>border</code> color. For a way of flooding an
  1076. area defined by the color of the starting point, see
  1077. <A HREF="#gdImageFill">gdImageFill</A>.
  1078. <P>
  1079. The border color <em>cannot</em> be a special color
  1080. such as <A HREF="#gdTiled">gdTiled</A>; it must be a proper
  1081. solid color. The fill color can be, however.
  1082. <P>
  1083. Note that gdImageFillToBorder is recursive. It is not the most
  1084. naive implementation possible, and the implementation is
  1085. expected to improve, but there will always be degenerate
  1086. cases in which the stack can become very deep. This can be
  1087. a problem in MSDOS and MS Windows environments. (Of course,
  1088. in a Unix or NT environment with a proper stack, this is
  1089. not a problem at all.)
  1090. <PRE>
  1091. ... inside a function ...
  1092. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1093. int black;
  1094. int white;
  1095. int red;
  1096. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 50);
  1097. /* Background color (first allocated) */
  1098. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1099. /* Allocate the color white (red, green and blue all maximum). */
  1100. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1101. /* Allocate the color red. */
  1102. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1103. /* Inscribe an ellipse in the image. */
  1104. gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
  1105. /* Flood-fill the ellipse. Fill color is red, border color is
  1106.         white (ellipse). */
  1107. gdImageFillToBorder(im, 50, 50, white, red);
  1108. /* ... Do something with the image, such as saving it to a file... */
  1109. /* Destroy it */
  1110. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1111. </PRE>
  1112. <DT><A NAME="gdImageFill">void gdImageFill(gdImagePtr im, int x, int y, int color)
  1113. <STRONG> (FUNCTION)</STRONG>
  1114. <DD>
  1115. gdImageFill floods a portion of the image with the specified
  1116. <code>color</code>, beginning at the specified point and flooding the
  1117. surrounding region of the same color as the starting point.
  1118. For a way of flooding a region defined by a specific border
  1119. color rather than by its interior color, see
  1120. <A HREF="#gdImageFillToBorder">gdImageFillToBorder</A>.
  1121. <P>
  1122. The fill color can be <A HREF="#gdTiled">gdTiled</A>, resulting
  1123. in a tile fill using another image as the tile. However,
  1124. the tile image cannot be transparent. If the image you wish
  1125. to fill with has a transparent color index, call
  1126. <A HREF="#gdImageTransparent">gdImageTransparent</A> on the
  1127. tile image and set the transparent color index to -1
  1128. to turn off its transparency.
  1129. <P>
  1130. Note that gdImageFill is recursive. It is not the most
  1131. naive implementation possible, and the implementation is
  1132. expected to improve, but there will always be degenerate
  1133. cases in which the stack can become very deep. This can be
  1134. a problem in MSDOS and MS Windows environments. (Of course,
  1135. in a Unix or NT environment with a proper stack, this is
  1136. not a problem at all.)
  1137. <PRE>
  1138. ... inside a function ...
  1139. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1140. int black;
  1141. int white;
  1142. int red;
  1143. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 50);
  1144. /* Background color (first allocated) */
  1145. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1146. /* Allocate the color white (red, green and blue all maximum). */
  1147. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1148. /* Allocate the color red. */
  1149. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1150. /* Inscribe an ellipse in the image. */
  1151. gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
  1152. /* Flood-fill the ellipse. Fill color is red, and will replace the
  1153.         black interior of the ellipse. */
  1154. gdImageFill(im, 50, 50, red);
  1155. /* ... Do something with the image, such as saving it to a file... */
  1156. /* Destroy it */
  1157. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1158. </PRE>
  1159. <DT><A NAME="gdImageSetBrush">void gdImageSetBrush(gdImagePtr im, gdImagePtr brush)</A>
  1160. <STRONG>(FUNCTION)</STRONG>
  1161. <DD>
  1162. A "brush" is an image used to draw wide, shaped strokes in another image. Just
  1163. as a paintbrush is not a single point, a brush image need not be
  1164. a single pixel. <em>Any</em> gd image can be used as a brush, and by
  1165. setting the transparent color index of the brush image with
  1166. <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A>,
  1167. a brush of any shape can be created. All line-drawing functions,
  1168. such as <A HREF="#gdImageLine">gdImageLine</A> and
  1169. <A HREF="#gdImagePolygon">gdImagePolygon</A>, will use the
  1170. current brush if the special "color" <A HREF="#gdBrushed">
  1171. gdBrushed</A> or <A HREF="#gdStyledBrushed">gdStyledBrushed</A>
  1172. is used when calling them.
  1173. <P>
  1174. gdImageSetBrush is used to specify the brush to be used in a
  1175. particular image. You can set any image to be the brush.
  1176. If the brush image does not have the same color map as the
  1177. first image, any colors missing from the first image
  1178. will be allocated. If not enough colors can be allocated,
  1179. the closest colors already available will be used. This
  1180. allows arbitrary GIFs to be used as brush images. It also
  1181. means, however, that you should not set a brush unless you
  1182. will actually use it; if you set a rapid succession of
  1183. different brush images, you can quickly fill your color map,
  1184. and the results will not be optimal.
  1185. <P>
  1186. You need not take any special action when you are finished
  1187. with a brush. As for any other image, if you will not
  1188. be using the brush image for any further purpose,
  1189. you should call <A HREF="#gdImageDestroy">gdImageDestroy</A>.
  1190. You must not use the color <A HREF="#gdBrushed">gdBrushed</A>
  1191. if the current brush has been destroyed; you can of
  1192. course set a new brush to replace it.
  1193. <PRE>
  1194. ... inside a function ...
  1195. <A HREF="#gdImagePtr">gdImagePtr</A> im, brush;
  1196. FILE *in;
  1197. int black;
  1198. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1199. /* Open the brush GIF. For best results, portions of the
  1200.         brush that should be transparent (ie, not part of the
  1201.         brush shape) should have the transparent color index. */
  1202. in = fopen("star.gif", "rb");
  1203. brush = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1204. /* Background color (first allocated) */
  1205. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1206. gdImageSetBrush(im, brush);
  1207. /* Draw a line from the upper left corner to the lower right corner
  1208.         using the brush. */
  1209. <A HREF="#gdImageLine">gdImageLine</A>(im, 0, 0, 99, 99, <A HREF="#gdBrushed">gdBrushed</A>);
  1210. /* ... Do something with the image, such as saving it to a file... */
  1211. /* Destroy it */
  1212. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1213. /* Destroy the brush image */
  1214. <A HREF="#gdImageDestroy">gdImageDestroy</A>(brush);
  1215. </PRE>
  1216. <DT><A NAME="gdImageSetTile">void gdImageSetTile(gdImagePtr im, gdImagePtr tile)</A>
  1217. <STRONG>(FUNCTION)</STRONG>
  1218. <DD>
  1219. A "tile" is an image used to fill an area with  a repeated pattern.
  1220. <em>Any</em> gd image can be used as a tile, and by
  1221. setting the transparent color index of the tile image with
  1222. <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A>,
  1223. a tile that allows certain parts of the underlying area to shine
  1224. through can be created. All region-filling functions,
  1225. such as <A HREF="#gdImageFill">gdImageFill</A> and
  1226. <A HREF="#gdImageFilledPolygon">gdImageFilledPolygon</A>, will use the
  1227. current tile if the special "color" <A HREF="#gdTiled">
  1228. gdTiled</A> is used when calling them.
  1229. <P>
  1230. gdImageSetTile is used to specify the tile to be used in a
  1231. particular image. You can set any image to be the tile.
  1232. If the tile image does not have the same color map as the
  1233. first image, any colors missing from the first image
  1234. will be allocated. If not enough colors can be allocated,
  1235. the closest colors already available will be used. This
  1236. allows arbitrary GIFs to be used as tile images. It also
  1237. means, however, that you should not set a tile unless you
  1238. will actually use it; if you set a rapid succession of
  1239. different tile images, you can quickly fill your color map,
  1240. and the results will not be optimal.
  1241. <P>
  1242. You need not take any special action when you are finished
  1243. with a tile. As for any other image, if you will not
  1244. be using the tile image for any further purpose,
  1245. you should call <A HREF="#gdImageDestroy">gdImageDestroy</A>.
  1246. You must not use the color <A HREF="#gdBrushed">gdTiled</A>
  1247. if the current tile has been destroyed; you can of
  1248. course set a new tile to replace it.
  1249. <PRE>
  1250. ... inside a function ...
  1251. <A HREF="#gdImagePtr">gdImagePtr</A> im, tile;
  1252. FILE *in;
  1253. int black;
  1254. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1255. /* Open the tile GIF. For best results, portions of the
  1256.         tile that should be transparent (ie, allowing the
  1257.         background to shine through) should have the transparent
  1258.         color index. */
  1259. in = fopen("star.gif", "rb");
  1260. tile = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1261. /* Background color (first allocated) */
  1262. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1263. gdImageSetTile(im, tile);
  1264. /* Fill an area using the tile. */
  1265. <A HREF="#gdImageFilledRectangle">gdImageFilledRectangle</A>(im, 25, 25, 75, 75, <A HREF="#gdTiled">gdTiled</A>);
  1266. /* ... Do something with the image, such as saving it to a file... */
  1267. /* Destroy it */
  1268. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1269. /* Destroy the tile image */
  1270. <A HREF="#gdImageDestroy">gdImageDestroy</A>(tile);
  1271. </PRE>
  1272. <DT><A NAME="gdImageSetStyle">void gdImageSetStyle(gdImagePtr im, int *style, int styleLength)</A>
  1273. <STRONG>(FUNCTION)</STRONG>
  1274. <DD>
  1275. It is often desirable to draw dashed lines, dotted lines, and other
  1276. variations on a broken line. gdImageSetStyle can be used to set
  1277. any desired series of colors, including a special color that
  1278. leaves the background intact, to be repeated during the drawing
  1279. of a line.
  1280. <P>
  1281. To use gdImageSetStyle, create an array of integers and assign
  1282. them the desired series of color values to be repeated.
  1283. You can assign the special color value <A HREF="#gdTransparent">
  1284. gdTransparent</A> to indicate that the existing color should
  1285. be left unchanged for that particular pixel (allowing a dashed
  1286. line to be attractively drawn over an existing image).
  1287. <P>
  1288. Then, to draw a line using the style, use the normal
  1289. <A HREF="#gdImageLine">gdImageLine</A> function with the
  1290. special color value <A HREF="#gdStyled">gdStyled</A>.
  1291. <P>
  1292. As of <A HREF="#whatsnew1.1.1">version 1.1.1</A>, the style
  1293. array is copied when you set the style, so you need not
  1294. be concerned with keeping the array around indefinitely.
  1295. This should not break existing code that assumes styles
  1296. are not copied.
  1297. <P>
  1298. You can also combine styles and brushes to draw the brush
  1299. image at intervals instead of in a continuous stroke.
  1300. When creating a style for use with a brush, the
  1301. style values are interpreted differently: zero (0) indicates
  1302. pixels at which the brush should not be drawn, while one (1)
  1303. indicates pixels at which the brush should be drawn.
  1304. To draw a styled, brushed line, you must use the
  1305. special color value <A HREF="#gdStyledBrushed">
  1306. gdStyledBrushed</A>. For an example of this feature
  1307. in use, see gddemo.c (provided in the distribution).
  1308. <PRE>
  1309. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1310. int styleDotted[2], styleDashed[6];
  1311. FILE *in;
  1312. int black;
  1313. int red;
  1314. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1315. /* Background color (first allocated) */
  1316. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1317. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1318. /* Set up dotted style. Leave every other pixel alone. */
  1319. styleDotted[0] = red;
  1320. styleDotted[1] = gdTransparent;
  1321. /* Set up dashed style. Three on, three off. */
  1322. styleDashed[0] = red;
  1323. styleDashed[1] = red;
  1324. styleDashed[2] = red;
  1325. styleDashed[3] = gdTransparent;
  1326. styleDashed[4] = gdTransparent;
  1327. styleDashed[5] = gdTransparent;
  1328. /* Set dotted style. Note that we have to specify how many pixels are
  1329.         in the style! */
  1330. gdImageSetStyle(im, styleDotted, 2);
  1331. /* Draw a line from the upper left corner to the lower right corner. */
  1332. <A HREF="#gdImageLine">gdImageLine</A>(im, 0, 0, 99, 99, <A HREF="#gdStyled">gdStyled</A>);
  1333. /* Now the dashed line. */
  1334. gdImageSetStyle(im, styleDashed, 6);
  1335. <A HREF="#gdImageLine">gdImageLine</A>(im, 0, 99, 0, 99, <A HREF="#gdStyled">gdStyled</A>);
  1336.  
  1337. /* ... Do something with the image, such as saving it to a file ... */
  1338.  
  1339. /* Destroy it */
  1340. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1341. </PRE>
  1342. </DL>
  1343. <H3><A NAME="query">Query Functions</A></H3>
  1344. <DL>
  1345. <DT><A NAME="gdImageBlue">
  1346. int gdImageBlue(gdImagePtr im, int color)</A>
  1347. <STRONG>(MACRO)</STRONG>
  1348. <DD>
  1349. gdImageBlue is a macro which returns the blue component of
  1350. the specified color index. Use this macro rather than accessing the
  1351. structure members directly.
  1352. <DT><A NAME="gdImageGetPixel">int gdImageGetPixel(gdImagePtr im, int x, int y)</A>
  1353. <STRONG>(FUNCTION)</STRONG>
  1354. <DD>
  1355. gdImageGetPixel() retrieves the color index of a particular
  1356. pixel. Always use this function to query pixels;
  1357. do not access the pixels of the <A HREF="#gdImage">gdImage</A> structure
  1358. directly.
  1359. <PRE>
  1360. ... inside a function ...
  1361. FILE *in;
  1362. gdImagePtr im;
  1363. int c;
  1364. in = fopen("mygif.gif", "rb");
  1365. im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1366. fclose(in);
  1367. c = gdImageGetPixel(im, gdImageSX(im) / 2, gdImageSY(im) / 2);
  1368. printf("The value of the center pixel is %d; RGB values are %d,%d,%d\n",
  1369.         c, im->red[c], im->green[c], im->blue[c]);
  1370. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1371. </PRE> 
  1372. <DT><A NAME="gdImageBoundsSafe">
  1373. int gdImageBoundsSafe(gdImagePtr im, int x, int y)</A>
  1374. <STRONG>(FUNCTION)</STRONG>
  1375. <DD>
  1376. gdImageBoundsSafe returns true (1) if the specified point is within the bounds
  1377. of the image, false (0) if not. This function is intended primarily for
  1378. use by those who wish to add functions to gd. All of the gd drawing
  1379. functions already clip safely to the edges of the image.
  1380. <PRE>
  1381. ... inside a function ...
  1382. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1383. int black;
  1384. int white;
  1385. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1386. if (gdImageBoundsSafe(im, 50, 50)) {
  1387.         printf("50, 50 is within the image bounds\n");
  1388. } else {
  1389.         printf("50, 50 is outside the image bounds\n");
  1390. }
  1391. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1392. </PRE>
  1393. <DT><A NAME="gdImageGreen">
  1394. int gdImageGreen(gdImagePtr im, int color)</A>
  1395. <STRONG>(MACRO)</STRONG>
  1396. <DD>
  1397. gdImageGreen is a macro which returns the green component of
  1398. the specified color index. Use this macro rather than accessing the
  1399. structure members directly.
  1400. <DT><A NAME="gdImageRed">
  1401. int gdImageRed(gdImagePtr im, int color)</A>
  1402. <STRONG>(MACRO)</STRONG>
  1403. <DD>
  1404. gdImageRed is a macro which returns the red component of
  1405. the specified color index. Use this macro rather than accessing the
  1406. structure members directly.
  1407. <DT><A NAME="gdImageSX">
  1408. int gdImageSX(gdImagePtr im)</A>
  1409. <STRONG>(MACRO)</STRONG>
  1410. <DD>
  1411. gdImageSX is a macro which returns the width of the image
  1412. in pixels. Use this macro rather than accessing the
  1413. structure members directly.
  1414. <DT><A NAME="gdImageSY">
  1415. int gdImageSY(gdImagePtr im)</A>
  1416. <STRONG>(MACRO)</STRONG>
  1417. <DD>
  1418. gdImageSY is a macro which returns the height of the image
  1419. in pixels. Use this macro rather than accessing the
  1420. structure members directly.
  1421. </DL>
  1422. <H3><A NAME="fonts">Fonts and text-handling functions</A></H3>
  1423. <DL>
  1424. <DT><A NAME="gdImageChar">
  1425. void gdImageChar(gdImagePtr im, gdFontPtr font, int x, int y,
  1426.         int c, int color)</A>
  1427. <STRONG>(FUNCTION)</STRONG>
  1428. <DD>
  1429. gdImageChar is used to draw single characters on the image.
  1430. (To draw multiple characters, use <A HREF="#gdImageString">
  1431. gdImageString</A>.) The second argument is a
  1432. pointer to a font definition structure; five fonts are
  1433. provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
  1434. gdFontLarge, and gdFontGiant. You must
  1435. include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
  1436. "gdfontl.h" and "gdfontg.h" respectively
  1437. and (if you are not using a library-based approach) link with the
  1438. corresponding .c files to use the provided fonts.
  1439. The character specified by the fifth
  1440. argument is drawn from left to right in the specified
  1441. color. (See <A HREF="#gdImageCharUp">gdImageCharUp</A> for a way
  1442. of drawing vertical text.) Pixels not
  1443. set by a particular character retain their previous color.
  1444. <PRE>
  1445. #include "gd.h"
  1446. #include "gdfontl.h"
  1447. ... inside a function ...
  1448. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1449. int black;
  1450. int white;
  1451. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1452. /* Background color (first allocated) */
  1453. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1454. /* Allocate the color white (red, green and blue all maximum). */
  1455. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1456. /* Draw a character. */
  1457. gdImageChar(im, gdFontLarge, 0, 0, 'Q', white);
  1458. /* ... Do something with the image, such as saving it to a file... */
  1459. /* Destroy it */
  1460. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1461. </PRE>
  1462. <DT><A NAME="gdImageCharUp">
  1463. void gdImageCharUp(gdImagePtr im, gdFontPtr font, int x, int y,
  1464. int c, int color)</A>
  1465. <STRONG>(FUNCTION)</STRONG>
  1466. <DD>
  1467. gdImageCharUp is used to draw single characters on the image,
  1468. rotated 90 degrees.
  1469. (To draw multiple characters, use <A HREF="#gdImageStringUp">
  1470. gdImageStringUp</A>.) The second argument is a
  1471. pointer to a font definition structure; five fonts are
  1472. provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
  1473. gdFontLarge, and gdFontGiant. You must
  1474. include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
  1475. "gdfontl.h" and "gdfontg.h" respectively
  1476. and (if you are not using a library-based approach) link with the
  1477. corresponding .c files to use the provided fonts. The character specified by
  1478. the fifth argument is drawn
  1479. from bottom to top, rotated at a 90-degree angle,  in the specified
  1480. color.  (See <A HREF="#gdImageChar">gdImageChar</A> for a way
  1481. of drawing horizontal text.)  Pixels not
  1482. set by a particular character retain their previous color.
  1483. <PRE>
  1484. #include "gd.h"
  1485. #include "gdfontl.h"
  1486. ... inside a function ...
  1487. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1488. int black;
  1489. int white;
  1490. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1491. /* Background color (first allocated) */
  1492. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1493. /* Allocate the color white (red, green and blue all maximum). */
  1494. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1495. /* Draw a character upwards so it rests against the top of the image. */
  1496. gdImageCharUp(im, gdFontLarge,
  1497.         0, gdFontLarge->h, 'Q', white);
  1498. /* ... Do something with the image, such as saving it to a file... */
  1499. /* Destroy it */
  1500. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1501. </PRE>
  1502. <DT><A NAME="gdImageString">
  1503. void gdImageString(gdImagePtr im, gdFontPtr font, int x, int y,
  1504. char *s, int color)</A>
  1505. <STRONG>(FUNCTION)</STRONG>
  1506. <DD>
  1507. gdImageString is used to draw multiple characters on the image.
  1508. (To draw single characters, use <A HREF="#gdImageChar">
  1509. gdImageChar</A>.) The second argument is a
  1510. pointer to a font definition structure; five fonts are
  1511. provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
  1512. gdFontLarge, and gdFontGiant. You must
  1513. include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
  1514. "gdfontl.h" and "gdfontg.h" respectively
  1515. and (if you are not using a library-based approach) link with the
  1516. corresponding .c files to use the provided fonts.
  1517. The null-terminated C string specified
  1518. by the fifth argument is drawn from left to right in the specified
  1519. color.  (See <A HREF="#gdImageStringUp">gdImageStringUp</A> for a way
  1520. of drawing vertical text.)  Pixels not
  1521. set by a particular character retain their previous color.
  1522. <PRE>
  1523. #include "gd.h"
  1524. #include "gdfontl.h"
  1525. #include &lt;string.h&gt;
  1526. ... inside a function ...
  1527. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1528. int black;
  1529. int white;
  1530. /* String to draw. */
  1531. char *s = "Hello.";
  1532. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1533. /* Background color (first allocated) */
  1534. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1535. /* Allocate the color white (red, green and blue all maximum). */
  1536. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1537. /* Draw a centered string. */
  1538. gdImageString(im, gdFontLarge,
  1539.         im->w / 2 - (strlen(s) * gdFontLarge->w / 2),
  1540.         im->h / 2 - gdFontLarge->h / 2,
  1541.         s, white);
  1542. /* ... Do something with the image, such as saving it to a file... */
  1543. /* Destroy it */
  1544. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1545. </PRE>
  1546. <DT><A NAME="gdImageStringUp">
  1547. void gdImageStringUp(gdImagePtr im, gdFontPtr font, int x, int y,
  1548. char *s, int color)</A>
  1549. <STRONG>(FUNCTION)</STRONG>
  1550. <DD>
  1551. gdImageStringUp is used to draw multiple characters on the image,
  1552. rotated 90 degrees.
  1553. (To draw single characters, use <A HREF="#gdImageCharUp">
  1554. gdImageCharUp</A>.) The second argument is a
  1555. pointer to a font definition structure; five fonts are
  1556. provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
  1557. gdFontLarge, and gdFontGiant. You must
  1558. include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
  1559. "gdfontl.h" and "gdfontg.h" respectively
  1560. and (if you are not using a library-based approach) link with the
  1561. corresponding .c files to use the provided fonts.The null-terminated C string specified
  1562. by the fifth argument is drawn from bottom to top (rotated
  1563. 90 degrees) in the specified color.  (See
  1564. <A HREF="#gdImageString">gdImageString</A> for a way
  1565. of drawing horizontal text.)  Pixels not
  1566. set by a particular character retain their previous color.
  1567. <PRE>
  1568. #include "gd.h"
  1569. #include "gdfontl.h"
  1570. #include &lt;string.h&gt;
  1571. ... inside a function ...
  1572. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1573. int black;
  1574. int white;
  1575. /* String to draw. */
  1576. char *s = "Hello.";
  1577. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1578. /* Background color (first allocated) */
  1579. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1580. /* Allocate the color white (red, green and blue all maximum). */
  1581. white = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 255, 255);   
  1582. /* Draw a centered string going upwards. Axes are reversed,
  1583.         and Y axis is decreasing as the string is drawn. */
  1584. gdImageStringUp(im, gdFontLarge,
  1585.         im->w / 2 - gdFontLarge->h / 2,
  1586.         im->h / 2 + (strlen(s) * gdFontLarge->w / 2),
  1587.         s, white);
  1588. /* ... Do something with the image, such as saving it to a file... */
  1589. /* Destroy it */
  1590. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1591. </PRE>
  1592. </DL>
  1593. <H3><A NAME="colors">Color-handling functions</A></H3>
  1594. <DL>
  1595. <DT><A NAME="gdImageColorAllocate">
  1596. int gdImageColorAllocate(gdImagePtr im, int r, int g, int b)</A>
  1597. <STRONG>(FUNCTION)</STRONG>
  1598. <DD>
  1599. gdImageColorAllocate finds the first available color index in
  1600. the image specified, sets its RGB values to those requested
  1601. (255 is the maximum for each),
  1602. and returns the index of the new color table entry. When
  1603. creating a new image, the first time you invoke this function,
  1604. you are setting the background color for that image.
  1605. <P>
  1606. In the event that all <A HREF="#gdMaxColors">gdMaxColors</A> colors
  1607. (256) have already been allocated, gdImageColorAllocate will
  1608. return -1 to indicate failure. (This is not uncommon when
  1609. working with existing GIF files that already use 256 colors.)
  1610. Note that gdImageColorAllocate
  1611. does not check for existing colors that match your request;
  1612. see <A HREF="#gdImageColorExact">gdImageColorExact</A>
  1613. and <A HREF="#gdImageColorClosest">gdImageColorClosest</A>
  1614. for ways to locate existing colors that approximate the
  1615. color desired in situations where a new color is not available.
  1616. <PRE>
  1617. ... inside a function ...
  1618. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1619. int black;
  1620. int red;
  1621. im = <A HREF="#gdImageCreate">gdImageCreate</A>(100, 100);
  1622. /* Background color (first allocated) */
  1623. black = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 0, 0, 0); 
  1624. /* Allocate the color red. */
  1625. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1626. /* Draw a dashed line from the upper left corner to the lower right corner. */
  1627. gdImageDashedLine(im, 0, 0, 99, 99, red);
  1628. /* ... Do something with the image, such as saving it to a file... */
  1629. /* Destroy it */
  1630. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1631. </PRE>
  1632. <DT><A NAME="gdImageColorClosest">
  1633. int gdImageColorClosest(gdImagePtr im, int r, int g, int b)</A>
  1634. <STRONG>(FUNCTION)</STRONG>
  1635. <DD>
  1636. gdImageColorClosest searches the colors which have been
  1637. defined thus far in the image specified and returns the
  1638. index of the color with RGB values closest to those of the
  1639. request. (Closeness is determined by Euclidian distance,
  1640. which is used to determine the distance in three-dimensional color
  1641. space between colors.)
  1642. <P>
  1643. If no colors have yet been allocated in the image,
  1644. gdImageColorClosest returns -1.
  1645. <P>
  1646. This function is most useful as a backup method for choosing
  1647. a drawing color when an image already contains
  1648. <A HREF="#gdMaxColors">gdMaxColors</A> (256) colors and
  1649. no more can be allocated. (This is not uncommon when
  1650. working with existing GIF files that already use many colors.)
  1651. See <A HREF="#gdImageColorExact">gdImageColorExact</A>
  1652. for a method of locating exact matches only.
  1653. <PRE>
  1654. ... inside a function ...
  1655. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1656. FILE *in;
  1657. int red;
  1658. /* Let's suppose that photo.gif is a scanned photograph with
  1659.         many colors. */
  1660. in = fopen("photo.gif", "rb");
  1661. im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1662. fclose(in);
  1663. /* Try to allocate red directly */
  1664. red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1665. /* If we fail to allocate red... */
  1666. if (red == (-1)) {
  1667.         /* Find the <em>closest</em> color instead. */
  1668.         red = gdImageColorClosest(im, 255, 0, 0);
  1669. }
  1670. /* Draw a dashed line from the upper left corner to the lower right corner */
  1671. gdImageDashedLine(im, 0, 0, 99, 99, red);
  1672. /* ... Do something with the image, such as saving it to a file... */
  1673. /* Destroy it */
  1674. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1675. </PRE>
  1676. <DT><A NAME="gdImageColorExact">
  1677. int gdImageColorExact(gdImagePtr im, int r, int g, int b)</A>
  1678. <STRONG>(FUNCTION)</STRONG>
  1679. <DD>
  1680. gdImageColorExact searches the colors which have been
  1681. defined thus far in the image specified and returns the
  1682. index of the first color with RGB values which exactly
  1683. match those of the request. If no allocated color matches the
  1684. request precisely, gdImageColorExact returns -1.
  1685. See <A HREF="#gdImageColorClosest">gdImageColorClosest</A>
  1686. for a way to find the color closest to the color requested.
  1687. <PRE>
  1688. ... inside a function ...
  1689. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1690. int red;
  1691. in = fopen("photo.gif", "rb");
  1692. im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1693. fclose(in);
  1694. /* The image may already contain red; if it does, we'll save a slot
  1695.         in the color table by using that color. */
  1696. /* Try to allocate red directly */
  1697. red = gdImageColorExact(im, 255, 0, 0);
  1698. /* If red isn't already present... */
  1699. if (red == (-1)) {
  1700.         /* Second best: try to allocate it directly. */
  1701.         red = <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>(im, 255, 0, 0); 
  1702.         /* Out of colors, so find the <em>closest</em> color instead. */
  1703.         red = gdImageColorClosest(im, 255, 0, 0);
  1704. }
  1705. /* Draw a dashed line from the upper left corner to the lower right corner */
  1706. gdImageDashedLine(im, 0, 0, 99, 99, red);
  1707. /* ... Do something with the image, such as saving it to a file... */
  1708. /* Destroy it */
  1709. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1710. </PRE>
  1711. <DT><A NAME="gdImageColorsTotal">
  1712. int gdImageColorsTotal(gdImagePtr im)</A>
  1713. <STRONG>(MACRO)</STRONG>
  1714. <DD>
  1715. gdImageColorsTotal is a macro which returns the number of
  1716. colors currently allocated in the image. Use this macro
  1717. to obtain this information; do not access the structure
  1718. directly.
  1719. <DT><A NAME="gdImageColorRed">
  1720. int gdImageColorRed(gdImagePtr im, int c)</A>
  1721. <STRONG>(MACRO)</STRONG>
  1722. <DD>
  1723. gdImageColorRed is a macro which returns the red portion
  1724. of the specified color in the image. Use this macro
  1725. to obtain this information; do not access the structure
  1726. directly.
  1727. <DT><A NAME="gdImageColorGreen">
  1728. int gdImageColorGreen(gdImagePtr im, int c)</A>
  1729. <STRONG>(MACRO)</STRONG>
  1730. <DD>
  1731. gdImageColorGreen is a macro which returns the green portion
  1732. of the specified color in the image. Use this macro
  1733. to obtain this information; do not access the structure
  1734. directly.
  1735. <DT><A NAME="gdImageColorBlue">
  1736. int gdImageColorBlue(gdImagePtr im, int c)</A>
  1737. <STRONG>(MACRO)</STRONG>
  1738. <DD>
  1739. gdImageColorBlue is a macro which returns the green portion
  1740. of the specified color in the image. Use this macro
  1741. to obtain this information; do not access the structure
  1742. directly.
  1743. <DT><A NAME="gdImageGetInterlaced">
  1744. int gdImageGetInterlaced(gdImagePtr im)</A>
  1745. <STRONG>(MACRO)</STRONG>
  1746. <DD>
  1747. gdImageGetInterlaced is a macro which returns true (1)
  1748. if the image is interlaced, false (0) if not.
  1749. Use this macro to obtain this information; do not
  1750. access the structure directly.
  1751. See <A NAME="gdImageInterlace">gdImageInterlace</A> for
  1752. a means of interlacing images.
  1753. <DT><A NAME="gdImageGetTransparent">
  1754. int gdImageGetTransparent(gdImagePtr im)</A>
  1755. <STRONG>(MACRO)</STRONG>
  1756. <DD>
  1757. gdImageGetTransparent is a macro which returns the
  1758. current transparent color index in the image.
  1759. If there is no transparent color, gdImageGetTransparent
  1760. returns -1. Use this macro to obtain this information; do not
  1761. access the structure directly.
  1762. <DT><A NAME="gdImageColorDeallocate">
  1763. void gdImageColorDeallocate(gdImagePtr im, int color)</A>
  1764. <STRONG>(FUNCTION)</STRONG>
  1765. <DD>
  1766. gdImageColorDeallocate marks the specified color as being
  1767. available for reuse. It does not attempt to determine whether
  1768. the color index is still in use in the image. After a call
  1769. to this function, the next call to
  1770. <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>
  1771. for the same image will set new RGB values for that
  1772. color index, changing the color of any pixels which
  1773. have that index as a result. If multiple calls to
  1774. gdImageColorDeallocate are made consecutively, the lowest-numbered
  1775. index among them will be reused by the next
  1776. <A HREF="#gdImageColorAllocate"> gdImageColorAllocate</A> call.
  1777. <PRE>
  1778. ... inside a function ...
  1779. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1780. int red, blue;
  1781. in = fopen("photo.gif", "rb");
  1782. im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1783. fclose(in);
  1784. /* Look for red in the color table. */
  1785. red = gdImageColorExact(im, 255, 0, 0);
  1786. /* If red is present... */
  1787. if (red != (-1)) {
  1788.         /* Deallocate it. */
  1789.         gdImageColorDeallocate(im, red);
  1790.         /* Allocate blue, reusing slot in table.
  1791.                 Existing red pixels will change color. */
  1792.         blue = gdImageColorAllocate(im, 0, 0, 255);
  1793. }
  1794. /* ... Do something with the image, such as saving it to a file... */
  1795. /* Destroy it */
  1796. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1797. </PRE>
  1798. <DT><A NAME="gdImageColorTransparent">
  1799. void gdImageColorTransparent(gdImagePtr im, int color)</A>
  1800. <STRONG>(FUNCTION)</STRONG>
  1801. <DD>
  1802. gdImageColorTransparent sets the transparent color index
  1803. for the specified image to the specified index. To indicate
  1804. that there should be <em>no</em> transparent color, invoke
  1805. gdImageColorTransparent with a color index of -1.
  1806. <P>
  1807. The color index used should be an index
  1808. allocated by <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A>,
  1809. whether explicitly invoked by your code or implicitly
  1810. invoked by loading an image.
  1811. In order to ensure that your image has a reasonable appearance
  1812. when viewed by users who do not have transparent background
  1813. capabilities, be sure to give reasonable RGB values to the
  1814. color you allocate for use as a transparent color,
  1815. <em>even though it will be transparent on systems
  1816. that support transparency</em>.
  1817. <PRE>
  1818. ... inside a function ...
  1819. <A HREF="#gdImagePtr">gdImagePtr</A> im;
  1820. int black;
  1821. FILE *in, *out;
  1822. in = fopen("photo.gif", "rb");
  1823. im = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1824. fclose(in);
  1825. /* Look for black in the color table and make it transparent. */
  1826. black = <A HREF="#gdImageColorExact">gdImageColorExact</A>(im, 0, 0, 0);
  1827. /* If black is present... */
  1828. if (black != (-1)) {
  1829.         /* Make it transparent */
  1830.         gdImageColorTransparent(im, black);
  1831. }
  1832. /* Save the newly-transparent image back to the file */
  1833. out = fopen("photo.gif", "wb");
  1834. <A HREF="#gdImageGif">gdImageGif</A>(im, out);
  1835. fclose(out);
  1836. /* Destroy it */
  1837. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  1838. </PRE>
  1839. </DL>
  1840. <H3><A NAME="copying">Copying and resizing functions</A></H3>
  1841. <DL>
  1842. <DT><A NAME="gdImageCopy">void gdImageCopy(gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int srcX, int srcY, int w, int h)
  1843. <STRONG> (FUNCTION)</STRONG>
  1844. <DD>
  1845. gdImageCopy is used to copy a rectangular portion of one image to
  1846. another image. (For a way of stretching or shrinking the image
  1847. in the process, see <A HREF="#gdImageCopyResized">
  1848. gdImageCopyResized</A>.)
  1849. <P>
  1850. The <code>dst</code> argument is the destination image to which the
  1851. region will be copied. The <code>src</code> argument is the source
  1852. image from which the region is copied. The <code>dstX</code>
  1853. and <code>dstY</code> arguments specify the point in the destination
  1854. image to which the region will be copied. The <code>srcX</code>
  1855. and <code>srcY</code> arguments specify the upper left corner
  1856. of the region in the source image. The <code>w</code>
  1857. and <code>h</code> arguments specify the width and height
  1858. of the region.
  1859. <P>
  1860. When you copy a region from one location in an image to another
  1861. location in the same image, gdImageCopy will perform as expected
  1862. unless the regions overlap, in which case the result is
  1863. unpredictable.
  1864. <P>
  1865. <strong>Important note on copying between images:</strong> since
  1866. different images do
  1867. not necessarily have the same color tables, pixels are not simply set to the
  1868. same color index values to copy them. gdImageCopy will attempt
  1869. to find an identical RGB value in the destination image for
  1870. each pixel in the copied portion of the source image by
  1871. invoking <A HREF="#gdImageColorExact">gdImageColorExact</A>. If
  1872. such a value is not found, gdImageCopy will attempt to
  1873. allocate colors as needed using <A HREF="#gdImageColorAllocate">
  1874. gdImageColorAllocate</A>. If both of these methods fail,
  1875. gdImageCopy will invoke <A HREF="#gdImageColorClosest">
  1876. gdImageColorClosest</A> to find the color in the destination
  1877. image which most closely approximates the color of the
  1878. pixel being copied.
  1879. <PRE>
  1880. ... Inside a function ...
  1881. <A HREF="#gdImagePtr">gdImagePtr</A> im_in;
  1882. <A HREF="#gdImagePtr">gdImagePtr</A> im_out;
  1883. int x, y;
  1884. FILE *in;
  1885. FILE *out;
  1886. /* Load a small gif to tile the larger one with */
  1887. in = fopen("small.gif", "rb");
  1888. im_in = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1889. fclose(in);
  1890. /* Make the output image four times as large on both axes */
  1891. im_out = <A HREF="#gdImageCreate">gdImageCreate</A>(im_in->sx * 4, im_in->sy * 4);
  1892. /* Now tile the larger image using the smaller one */
  1893. for (y = 0; (y < 4); y++) {
  1894.         for (x = 0; (x < 4); x++) {
  1895.                 gdImageCopy(im_out, im_in,
  1896.                         x * im_in->sx, y * im_in->sy,
  1897.                         0, 0,
  1898.                         im_in->sx, im_in->sy);
  1899.         }
  1900. }
  1901. out = fopen("tiled.gif", "wb");
  1902. <A HREF="#gdImageGif">gdImageGif</A>(im_out, out);
  1903. fclose(out);
  1904. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im_in);
  1905. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im_out);
  1906. </PRE>
  1907. <DT><A NAME="gdImageCopyResized">void gdImageCopyResized(gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int srcX, int srcY, int destW, int destH, int srcW, int srcH)
  1908. <STRONG> (FUNCTION)</STRONG>
  1909. <DD>
  1910. gdImageCopyResized is used to copy a rectangular portion of one image to
  1911. another image. The X and Y dimensions of the original region and the
  1912. destination region can vary, resulting in stretching or shrinking of
  1913. the region as appropriate. (For a simpler version of this function
  1914. which does not deal with resizing, see <A HREF="#gdImageCopy">
  1915. gdImageCopy</A>.)
  1916. <P>
  1917. The <code>dst</code> argument is the destination image to which the
  1918. region will be copied. The <code>src</code> argument is the source
  1919. image from which the region is copied. The <code>dstX</code>
  1920. and <code>dstY</code> arguments specify the point in the destination
  1921. image to which the region will be copied. The <code>srcX</code>
  1922. and <code>srcY</code> arguments specify the upper left corner
  1923. of the region in the source image. The <code>dstW</code>
  1924. and <code>dstH</code> arguments specify the width and height
  1925. of the destination region. The <code>srcW</code>
  1926. and <code>srcH</code> arguments specify the width and height
  1927. of the source region and can differ from the destination size,
  1928. allowing a region to be scaled during the copying process.
  1929. <P>
  1930. When you copy a region from one location in an image to another
  1931. location in the same image, gdImageCopy will perform as expected
  1932. unless the regions overlap, in which case the result is
  1933. unpredictable. If this presents a problem, create a scratch image
  1934. in which to keep intermediate results.
  1935. <P>
  1936. <strong>Important note on copying between images:</strong> since images
  1937. do not necessarily have the same color tables, pixels are not simply set
  1938. to the same color index values to copy them. gdImageCopy will attempt
  1939. to find an identical RGB value in the destination image for
  1940. each pixel in the copied portion of the source image by
  1941. invoking <A HREF="#gdImageColorExact">gdImageColorExact</A>. If
  1942. such a value is not found, gdImageCopy will attempt to
  1943. allocate colors as needed using <A HREF="#gdImageColorAllocate">
  1944. gdImageColorAllocate</A>. If both of these methods fail,
  1945. gdImageCopy will invoke <A HREF="#gdImageColorClosest">
  1946. gdImageColorClosest</A> to find the color in the destination
  1947. image which most closely approximates the color of the
  1948. pixel being copied.
  1949. <PRE>
  1950. ... Inside a function ...
  1951. <A HREF="#gdImagePtr">gdImagePtr</A> im_in;
  1952. <A HREF="#gdImagePtr">gdImagePtr</A> im_out;
  1953. int x, y;
  1954. FILE *in;
  1955. FILE *out;
  1956. /* Load a small gif to expand in the larger one */
  1957. in = fopen("small.gif", "rb");
  1958. im_in = <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A>(in);
  1959. fclose(in);
  1960. /* Make the output image four times as large on both axes */
  1961. im_out = <A HREF="#gdImageCreate">gdImageCreate</A>(im_in->sx * 4, im_in->sy * 4);
  1962. /* Now copy the smaller image, but four times larger */
  1963. gdImageCopyResized(im_out, im_in, 0, 0, 0, 0,
  1964.         im_out->sx, im_out->sy,
  1965.         im_in->sx, im_in->sy);   
  1966. out = fopen("large.gif", "wb");
  1967. <A HREF="#gdImageGif">gdImageGif</A>(im_out, out);
  1968. fclose(out);
  1969. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im_in);
  1970. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im_out);
  1971. </PRE>
  1972. </DL>
  1973. <H3><A NAME="misc">Miscellaneous Functions</A></H3>
  1974. <DL>
  1975. <DT><A NAME="gdImageInterlace">gdImageInterlace(gdImagePtr im, int interlace)</A> <strong>(FUNCTION)</strong>
  1976. <DD>
  1977. gdImageInterlace is used to determine whether an image should be stored
  1978. in a linear fashion, in which lines will appear on the display from
  1979. first to last, or in an interlaced fashion, in which the image
  1980. will "fade in" over several passes. By default, images are not
  1981. interlaced.
  1982. <P>
  1983. A nonzero value for the interlace argument turns on interlace;
  1984. a zero value turns it off. Note that interlace has no effect
  1985. on other functions, and has no meaning unless you save the
  1986. image in GIF format; the gd and xbm formats do not support
  1987. interlace.
  1988. <P>
  1989. When a GIF is loaded with <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif
  1990. </A>, interlace will be set according to the setting in the GIF file.
  1991. <P>
  1992. Note that many GIF viewers and web browsers do <em>not</em> support
  1993. interlace. However, the interlaced GIF should still display; it
  1994. will simply appear all at once, just as other images do.
  1995. <PRE>
  1996. gdImagePtr im;
  1997. FILE *out;
  1998. /* ... Create or load the image... */
  1999.  
  2000. /* Now turn on interlace */
  2001. gdImageInterlace(im, 1);
  2002. /* And open an output file */
  2003. out = fopen("test.gif", "wb");
  2004. /* And save the image */
  2005. <A HREF="#gdImageGif">gdImageGif</A>(im, out);
  2006. fclose(out);
  2007. <A HREF="#gdImageDestroy">gdImageDestroy</A>(im);
  2008. </PRE>
  2009. </DL>
  2010. <H3><A NAME="constants">Constants</A></H3>
  2011. <DL>
  2012. <DT><A NAME="gdBrushed">gdBrushed</A> <strong>(CONSTANT)</strong>
  2013. <DD>
  2014. Used in place of a color when invoking a line-drawing
  2015. function such as <A HREF="#gdImageLine">gdImageLine</A>
  2016. or <A HREF="#gdImageRectangle">gdImageRectangle</A>.
  2017. When gdBrushed is used as the color, the brush
  2018. image set with <A HREF="#gdImageSetBrush">gdImageSetBrush</A>
  2019. is drawn in place of each pixel of the line (the brush is
  2020. usually larger than one pixel, creating the effect
  2021. of a wide paintbrush). See also
  2022. <A HREF="#gdStyledBrushed">gdStyledBrushed</A> for a way
  2023. to draw broken lines with a series of distinct copies of an image.
  2024. <DT><A NAME="gdMaxColors"><code>gdMaxColors</code><strong>(CONSTANT)</strong>
  2025. <DD>
  2026. The constant 256. This is the maximum number of colors in a GIF file
  2027. according to the GIF standard, and is also the maximum number of
  2028. colors in a gd image.
  2029. <DT><A NAME="gdStyled">gdStyled</A> <strong>(CONSTANT)</strong>
  2030. <DD>
  2031. Used in place of a color when invoking a line-drawing
  2032. function such as <A HREF="#gdImageLine">gdImageLine</A>
  2033. or <A HREF="#gdImageRectangle">gdImageRectangle</A>.
  2034. When gdStyled is used as the color, the colors of the pixels are
  2035. drawn successively from the style that has been
  2036. set with <A HREF="#gdImageSetStyle">gdImageSetStyle</A>.
  2037. If the color of a pixel is equal to
  2038. <A HREF="#gdTransparent">gdTransparent</A>, that pixel
  2039. is not altered. (This mechanism is completely unrelated
  2040. to the "transparent color" of the image itself; see
  2041. <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A>
  2042. gdImageColorTransparent for that mechanism.) See also
  2043. <A NAME="#gdStyledBrushed"> gdStyledBrushed</A>.
  2044. <DT><A NAME="gdStyledBrushed">gdStyledBrushed</A> <strong>(CONSTANT)</strong>
  2045. <DD>
  2046. Used in place of a color when invoking a line-drawing
  2047. function such as <A HREF="#gdImageLine">gdImageLine</A>
  2048. or <A HREF="#gdImageRectangle">gdImageRectangle</A>.
  2049. When gdStyledBrushed is used as the color, the brush
  2050. image set with <A HREF="#gdImageSetBrush">gdImageSetBrush</A>
  2051. is drawn at each pixel of the line, providing that the
  2052. style set with <A HREF="#gdImageSetStyle">gdImageSetStyle</A>
  2053. contains a nonzero value (OR gdTransparent, which
  2054. does not equal zero but is supported for consistency)
  2055. for the current pixel. (Pixels are drawn successively from the style as the
  2056. line is drawn, returning to the beginning when the
  2057. available pixels in the style are exhausted.) Note that
  2058. this differs from the behavior of <A HREF="#gdStyled">gdStyled</A>,
  2059. in which the values in the style are used as actual
  2060. pixel colors, except for gdTransparent.
  2061. <DT><A NAME="gdDashSize">gdDashSize</A> <strong>(CONSTANT)</strong>
  2062. <DD>
  2063. The length of a dash in a dashed line. Defined to be 4 for
  2064. backwards compatibility with programs that use
  2065. <A NAME="gdImageDashedLine">gdImageDashedLine</A>. New
  2066. programs should use <A NAME="gdImageSetStyle">
  2067. gdImageSetStyle</A> and call the standard
  2068. <A NAME="gdImageLine">gdImageLine</A> function
  2069. with the special "color" <A NAME="gdStyled">
  2070. gdStyled</A> or <A NAME="gdStyledBrushed">gdStyledBrushed</A>.
  2071. <DT><A NAME="gdTiled">gdTiled</A> <strong>(CONSTANT)</strong>
  2072. <DD>
  2073. Used in place of a normal color in <A HREF="#gdImageFilledRectangle">
  2074. gdImageFilledRectangle</A>, <A HREF="#gdImageFilledPolygon">
  2075. gdImageFilledPolygon</A>,
  2076. <A HREF="#gdImageFill">gdImageFill</A>, and <A HREF="#gdImageFillToBorder">
  2077. gdImageFillToBorder</A>. gdTiled selects a pixel from the
  2078. tile image set with <A HREF="#gdImageSetTile">gdImageSetTile</A>
  2079. in such a way as to ensure that the filled area will be
  2080. tiled with copies of the tile image. See the discussions of
  2081. <A HREF="#gdImageFill">gdImageFill</A> and
  2082. <A HREF="#gdImageFillToBorder">gdImageFillToBorder</A> for special
  2083. restrictions regarding those functions.
  2084. <DT><A NAME="gdTransparent">gdTransparent</A> <strong>(CONSTANT)</strong>
  2085. <DD>
  2086. Used in place of a normal color in a style to be set with
  2087. <A HREF="#gdImageSetStyle">gdImageSetStyle</A>.
  2088. gdTransparent is <strong>not</strong> the transparent
  2089. color index of the image; for that functionality please
  2090. see <A HREF="gdImageColorTransparent">gdImageColorTransparent</A>.
  2091. </DL>
  2092. <A NAME="gdformat"><H3>About the additional .gd image file format</H3></A>
  2093. In addition to reading and writing the GIF format and reading the
  2094. X Bitmap format, gd has the capability to read and write its
  2095. own ".gd" format. This format is <em>not</em> intended for
  2096. general purpose use and should never be used to distribute
  2097. images. It is not a compressed format. Its purpose is solely to
  2098. allow very fast loading of images your program needs often in
  2099. order to build other images for output. If you are experiencing
  2100. performance problems when loading large, fixed GIF images your
  2101. program needs to produce its output images, you may wish
  2102. to examine the functions <A HREF="#gdImageCreateFromGd">
  2103. gdImageCreateFromGd</A> and <A HREF="#gdImageGd">gdImageGd</A>,
  2104. which read and write .gd format images.
  2105. <P>
  2106. The program "giftogd.c" is provided as a simple way of converting
  2107. .gif files to .gd format. I emphasize again that you will not
  2108. need to use this format unless you have a need for high-speed loading
  2109. of a few frequently-used images in your program.
  2110. <A NAME="informing"><H3>Please tell us you're using gd!</H3>
  2111. When you contact us and let us know you are using gd,
  2112. you help us justify the time spent in maintaining and improving
  2113. it. So please let us know. If the results are publicly
  2114. visible on the web, a URL is a wonderful thing to receive, but
  2115. if it's not a publicly visible project, a simple note is just
  2116. as welcome.
  2117. <A NAME="languages"><H3>Using gd with TCL</H3></A>
  2118. If you prefer TCL to C, you can use gd from your tcl program
  2119. thanks to the <A HREF="http://guraldi.hgp.med.umich.edu/gdtcl.html">
  2120. TCL gd extension</A> by Spencer W. Thomas, available at the link
  2121. above or by anonymous FTP to guraldi.hgp.med.umich.edu
  2122. in the directory pub/gdtcl.shar.
  2123. <A NAME="problems"><H3>If you have problems</H3></A>
  2124. If you have any difficulties with gd, feel free to contact
  2125. the author, <A HREF="http://sunsite.unc.edu/boutell/index.html">
  2126. Thomas Boutell</A>. Be sure to read this manual
  2127. carefully first.
  2128. <H3><A NAME="index">Alphabetical quick index</A></H3>
  2129. <A HREF="#gdBrushed">gdBrushed</A> |
  2130. <A HREF="#gdDashSize">gdDashSize</A> |
  2131. <A HREF="#gdFont">gdFont</A> |
  2132. <A HREF="#gdFontPtr">gdFontPtr</A> |
  2133. <A HREF="#gdImage">gdImage</A> |
  2134. <A HREF="#gdImageArc">gdImageArc</A> |
  2135. <A HREF="#gdImageBlue">gdImageBlue</A> |
  2136. <A HREF="#gdImageBoundsSafe">gdImageBoundsSafe</A> |
  2137. <A HREF="#gdImageChar">gdImageChar</A> |
  2138. <A HREF="#gdImageCharUp">gdImageCharUp</A> |
  2139. <A HREF="#gdImageColorAllocate">gdImageColorAllocate</A> |
  2140. <A HREF="#gdImageColorClosest">gdImageColorClosest</A> |
  2141. <A HREF="#gdImageColorDeallocate">gdImageColorDeallocate</A> |
  2142. <A HREF="#gdImageColorExact">gdImageColorExact</A> |
  2143. <A HREF="#gdImageColorTransparent">gdImageColorTransparent</A> |
  2144. <A HREF="#gdImageCopy">gdImageCopy</A> |
  2145. <A HREF="#gdImageCopyResized">gdImageCopyResized</A> |
  2146. <A HREF="#gdImageCreate">gdImageCreate</A> |
  2147. <A HREF="#gdImageCreateFromGd">gdImageCreateFromGd</A> |
  2148. <A HREF="#gdImageCreateFromGif">gdImageCreateFromGif</A> |
  2149. <A HREF="#gdImageCreateFromXbm">gdImageCreateFromXbm</A> |
  2150. <A HREF="#gdImageDashedLine">gdImageDashedLine</A> |
  2151. <A HREF="#gdImageDestroy">gdImageDestroy</A> |
  2152. <A HREF="#gdImageFill">gdImageFill</A> |
  2153. <A HREF="#gdImageFillToBorder">gdImageFillToBorder</A> |
  2154. <A HREF="#gdImageFilledRectangle">gdImageFilledRectangle</A> |
  2155. <A HREF="#gdImageGd">gdImageGd</A> |
  2156. <A HREF="#gdImageGetInterlaced">gdImageGetInterlaced</A> |
  2157. <A HREF="#gdImageGetPixel">gdImageGetPixel</A> |
  2158. <A HREF="#gdImageGetTransparent">gdImageGetTransparent</A> |
  2159. <A HREF="#gdImageGif">gdImageGif</A> |
  2160. <A HREF="#gdImageGreen">gdImageGreen</A> |
  2161. <A HREF="#gdImageInterlace">gdImageInterlace</A> |
  2162. <A HREF="#gdImageLine">gdImageLine</A> |
  2163. <A HREF="#gdImageFilledPolygon">gdImageFilledPolygon</A> |
  2164. <A HREF="#gdImagePolygon">gdImagePolygon</A> |
  2165. <A HREF="#gdImagePtr">gdImagePtr</A> |
  2166. <A HREF="#gdImageRectangle">gdImageRectangle</A> |
  2167. <A HREF="#gdImageRed">gdImageRed</A> |
  2168. <A HREF="#gdImageSetBrush">gdImageSetBrush</A> |
  2169. <A HREF="#gdImageSetPixel">gdImageSetPixel</A> |
  2170. <A HREF="#gdImageSetStyle">gdImageSetStyle</A> |
  2171. <A HREF="#gdImageSetTile">gdImageSetTile</A> |
  2172. <A HREF="#gdImageString">gdImageString</A> |
  2173. <A HREF="#gdImageStringUp">gdImageStringUp</A> |
  2174. <A HREF="#gdMaxColors">gdMaxColors</A> |
  2175. <A HREF="#gdPoint">gdPoint</A> |
  2176. <A HREF="#gdStyled">gdStyled</A> |
  2177. <A HREF="#gdStyledBrushed">gdStyledBrushed</A> |
  2178. <A HREF="#gdTiled">gdTiled</A> |
  2179. <A HREF="#gdTransparent">gdTransparent</A>
  2180. <P>
  2181. <em><A HREF="http://sunsite.unc.edu/boutell/index.html">
  2182. Thomas Boutell, boutell@netcom.com</A></em>
  2183. </BODY>
  2184. </HTML>
  2185.