UPGRADING UNIX USERS: READ THIS FIRST! Modern versions of gd install by default to /usr/local/lib and /usr/local/include. If you already have an older version of gd in /usr/lib and /usr/include, you may wish to use:./configure --prefix=/usrTo ensure that your new installation overwrites the old.GIF support has been restored in gd 2.0.28 and above. The well-known patents on LZW compression held by Unisys have expired in all countries. British Telecom and IBM may hold related patents but have never chosen to require royalties for GIF applications, to the best of my knowledge. I am not a lawyer and cannot give legal advice regarding this issue. PNG remains a superior format especially if lossless truecolor images are needed.
When building from soruce, gd 2.0.33 requires that the following libraries also be installed, in order to produce the related image formats. The win32 binary release (bgd) already contains the appropriate libraries. You may skip libraries associated with formats you do not use:
libpng (see the libpng home page), if you want PNG
zlib (see the info-zip home page), if you want PNG
jpeg-6b or later, if desired (see the Independent JPEG Group home page), if you want JPEG
If you want to use the TrueType font support, you must also install the FreeType 2.x library, including the header files. See the Freetype Home Page, or SourceForge. No, I cannot explain why that site is down on a particular day, and no, I can't send you a copy.
If you want to use the Xpm color bitmap loading support, you must also have the X Window System and the Xpm library installed (Xpm is often included in modern X distributions). Most of the time you won't need Xpm.
Please read the documentation and install the required libraries. Do not send email asking why
png.his not found. Do not send email asking whylibgd.sois not found, either. See the requirements section for more information. Thank you!
Up to the LibGD Homepage
Credits and license terms
In order to resolve any possible confusion regarding the authorship of gd, the following copyright statement covers all of the authors who have required such a statement. If you are aware of any oversights in this copyright notice, please contact Pierre-A. Joye who will be pleased to correct them.
COPYRIGHT STATEMENT FOLLOWS THIS LINE
Portions copyright 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 by Cold Spring Harbor Laboratory. Funded under Grant P41-RR02188 by the National Institutes of Health.Portions copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 by Boutell.Com, Inc.
Portions relating to GD2 format copyright 1999, 2000, 2001, 2002, 2003, 2004 Philip Warner.
Portions relating to PNG copyright 1999, 2000, 2001, 2002, 2003, 2004 Greg Roelofs.
Portions relating to gdttf.c copyright 1999, 2000, 2001, 2002, 2003, 2004 John Ellson (ellson@graphviz.org).
Portions relating to gdft.c copyright 2001, 2002, 2003, 2004 John Ellson (ellson@graphviz.org).
Portions copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Pierre-Alain Joye (pierre@libgd.org).
Portions relating to JPEG and to color quantization copyright 2000, 2001, 2002, 2003, 2004, Doug Becker and copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Thomas G. Lane. This software is based in part on the work of the Independent JPEG Group. See the file README-JPEG.TXT for more information.
Portions relating to GIF compression copyright 1989 by Jef Poskanzer and David Rowley, with modifications for thread safety by Thomas Boutell.
Portions relating to GIF decompression copyright 1990, 1991, 1993 by David Koblas, with modifications for thread safety by Thomas Boutell.
Portions relating to WBMP copyright 2000, 2001, 2002, 2003, 2004 Maurice Szmurlo and Johan Van den Brande.
Portions relating to GIF animations copyright 2004 Jaakko Hyvätti (jaakko.hyvatti@iki.fi)
Permission has been granted to copy, distribute and modify gd in any context without fee, including a commercial application, provided that this notice is present in user-accessible supporting documentation.
This does not affect your ownership of the derived work itself, and the intent is to assure proper credit for the authors of gd, not to interfere with your productive use of gd. If you have questions, ask. "Derived works" includes all programs that utilize the library. Credit must be given in user-accessible documentation.
This software is provided "AS IS." The copyright holders disclaim all warranties, either express or implied, including but not limited to implied warranties of merchantability and fitness for a particular purpose, with respect to this code and accompanying documentation.
Although their code does not appear in the current release, the authors also wish to thank Hutchison Avenue Software Corporation for their prior contributions.
END OF COPYRIGHT STATEMENT
gd is a graphics library. It allows your code to quickly draw images complete with lines, arcs, text, multiple colors, cut and paste from other images, and flood fills, and write out the result as a PNG or JPEG file. This is particularly useful in World Wide Web applications, where PNG and JPEG are two of the formats accepted for inline images by most browsers.
gd is not a paint program. If you are looking for a paint program, you are looking in the wrong place. If you are not a programmer, you are looking in the wrong place, unless you are installing a required library in order to run an application.
gd does not provide for every possible desirable graphics operation. It is not necessary or desirable for gd to become a kitchen-sink graphics package, but version 2.0 does include most frequently requested features, including both truecolor and palette images, resampling (smooth resizing of truecolor images) and so forth.
What if I want to use another programming
language?
Not all of these tools are necessarily up to date and fully compatible
with 2.0.33.
From 2.0.34 and later, please check the ISSUES and ChangeLog as well as the releases announcements.
Version 2.0.33 restores compatibility with older releases of Freetype 2.x in addition to the latest release. Thanks to John Ellson and the graphviz project.
Version 2.0.32 restores correct detection of Unicode character sets for freetype fonts, which repairs a bug that prevented umlauts from displaying properly. Thanks to John Ellson and the graphviz project. Also, version 2.0.32 builds all test programs smoothly in the absence of libpng.
A minor type naming conflict prevented bgd.dll from compiling, and it was left out of the distribution as a result. This has been corrected.
2.0.29 did not compile correctly when freetype was not available. This has been corrected. Thanks to Alessandro Ranellucci.
The actual resolved font filename can be returned in the gdFTStringExtra structure as the fontpath element if the gdFTEX_RETURNFONTPATHNAME flag is set. Also, a vector of character position advances can be retrieved if gdFTEX_XSHOW is set in the flags element. .afm files (font metrics) are now used to adjust size calculations when available. When fontconfig is not available, gd falls back to its usual behavior and requires a specific font file name. One can still fetch fonts by filename when gdFTUseFontConfig(1) is in effect, by setting the gdFTEX_FONTPATHNAME flag in the flag element of the gdFTStringExtra structure. Thanks to Dag Lem and John Ellson.
The following enhancements and fixes:
gdlib-config, which has been installed by
make install for some time now, has gained
a --features option. This option produces a space-separated
list of optional features with which the gd library was compiled.
Typical usage looks like this:
% gdlib-config --features GD_XPM GD_JPEG GD_FREETYPE GD_PNG GD_GIFOther
configure scripts can conveniently define
preprocessor symbols based on this list in order to conditionally
compile code. For instance, if
GD_PNG is not reported by --features, then gdImagePng is not
included in the library.
Thanks to Lars Hecking and Lincoln Stein for their advice on implementing this feature. Any blame for the actual implementation is entirely due to me (TBB).
Owing to an oversight while making changes to better accommodate the use of gd as a DLL, the extern qualifier was dropped from the declarations of font pointers in 2.0.24. This has been corrected. Thanks to Richard ("OpenMacNews").
Windows DLL now uses __stdcall calling convention. Existing applications will require a recompile, using the new version of gd.h, in order to use this version of the DLL. However, Visual BASIC and other non-C programmers will now be able to use the DLL, which is an enormous benefit and justifies the one-time inconvenience to existing DLL users.
The elaborate #ifdef test for older versions of Freetype without FT_ENCODING_MS_SYMBOL was needed in a second place also. Thanks to David R. Morrison.
An off-by-one error in gdImageToPalette caused transparency to be applied to the wrong pixels. Thanks to "Super Pikeman."
Output dpi specification option added to the
gdFTStringExtra structure, thanks to
Mark Shackelford. See gdImageStringFTEx.
gdFontPtr.
Direct use of gdFontLarge, etc. is strongly deprecated
for users of bgd.dll; use these new functions instead.
circletexttest if
PNG support is missing.
gdImageCreateFrom*Ptr family
of functions which make it convenient to load an image in any
GD-supported format directly from memory.
gdNewDynamicCtxEx function was added to
support the easy implementation of the above functions and to
correct a design problem which made life unpleasant for those passing
in memory not originally allocated by gd to the
gdNewDynamicCtx function by provoding a way to specify
that gd should never free or reallocate a particular block of memory.
The gdNewDynamicCtx function and its relatives, although
still exported for ABI compatibility, are now deprecated except
for internal use, in favor of gdImageCreateFromPngPtr
and its relatives.
gdFreeFontCache function,
an undocumented function added in an earlier release which now simply
calls gdFontCacheShutdown for backwards compatibility.
This repairs build problems when compiling PHP against the latest gd.
gdFreeFontCache function,
an undocumented function added in an earlier release which now simply
calls gdFontCacheShutdown for backwards compatibility.
This repairs build problems when compiling PHP against the latest gd.
extern declarations for the
gd font pointers inadvertently removed in 2.0.18.
Minor compilation and packaging problems with 2.0.16 were corrected. If 2.0.16 compiled without errors for you, then you don't need to upgrade to 2.0.17.
main() function of one of the test programs
was accidentally included in the gd shared library, causing problems
on some platforms. This has been corrected. Thanks to many people
who pointed this out.
gd2 file format routines
were fixed by Steven Brown. These problems were due to the
incorrect use of a signed integer.
gd file format correctly
for truecolor images. Truecolor gd files created with
earlier releases in the 2.0 series must be written again. The gd
file format is used to quickly load an entire uncompressed image, typically
an existing background to which additional material will be added; it is not a
general purpose file format. More advanced capabilities are also available
via the gd2 format. Thanks to Andreas Pfaller for reporting
the problem.
configure improvements by Lars Hecking.
configure fixes from Lars Hecking. Thanks, Lars.
Version 2.0.7 corrects a problem which caused 'configure' to complain that the directory NONE was not found, in various places, causing the configuration process to stop. There are no code changes.
-Wall, -ansi
and -pedantic options enabled.
configure time using this syntax:
./configure --prefix=/usr
configure script should be compatible with all standard
GNU configure options and will figure out the correct settings for a
much wider range of operating systems. Many, many thanks to
Lars Hecking for taking care of this.
What's new in version 2.0.4?
The following contributions from John Ellson:
configure now correctly detects and provides
support for the Xpm library and its dependencies (Len Makin)
configure script has been extensively modified
to work properly in tests with both Solaris and Linux. Other platforms
should also work based on feedback received and integrated to date.
--prefix option to configure
works properly.
annotate utility has been added. This is a
very handy tool for adding freetype text to existing JPEGs. After
make install, type annotate -h for more
information. Thanks to Joel Dubiner.
readme.jpn file.
pixels array
will fail only if it encounters an existing truecolor image, which may
happen if the code attempts to open and modify an existing JPEG or
truecolor PNG. Such code should be modified to check the
trueColor flag of the gdImage structure, and
refer to the tpixels array instead when it is set.
#include <gd.h> corrected to #include "gd.h" in gd_wbmp.c
What's new in version 1.7.3?
Another attempt at Makefile fixes to permit
linking with all libraries required on platforms with order-
dependent linkers. Perhaps it will work this time.
What's new in version 1.7.2?
An uninitialized-pointer bug in gdtestttf.c was corrected.
This bug caused crashes at the end of each call to gdImageStringTTF on
some platforms. Thanks to Wolfgang Haefelinger.
Documentation fixes. Thanks to Dohn Arms.
Makefile fixes to permit linking with all libraries required on platforms with order- dependent linkers.
What's new in version 1.7.1?
A minor buglet in the Makefile was corrected, as well as an inaccurate
error message in gdtestttf.c. Thanks to Masahito Yamaga.
What's new in version 1.7?
Version 1.7 contains the following changes:
autoconf and configure have been removed, in favor of a
carefully designed Makefile which produces and properly installs
the library and the binaries. System-dependent variables are
at the top of the Makefile for easy modification. I'm sorry,
folks, but autoconf generated many, many confused email
messages from people who didn't have things where autoconf
expected to find them. I am not an autoconf/automake wizard, and
gd is a simple, very compact library which does not need to
be a shared library. I did make many improvements
over the old gd 1.3 Makefile, which were directly inspired by the
autoconf version found in the 1.6 series (thanks to John Ellson).
-pedantic-errors
flag of gcc. Several pieces of not-quite-ANSI-C code were causing problems
for those with non-gcc compilers.
gdttf.c patched to allow the use of Windows symbol
fonts, when present (thanks to Joseph Peppin).
extern "C" wrappers added to gd.h and the
font header files for the convenience of C++ programmers.
bdftogd was also modified to automatically insert these
wrappers into future font header files. Thanks to John Lindal.
SEEK_SET.
Thanks to Robert Bonomi.
gdImageCreateFromXpm
function, if the Xpm library is available. Thanks to Caolan McNamara.
What's new in version 1.6.3?
Version 1.6.3 corrects a memory leak in gd_png.c. This leak caused
a significant amount of memory to be allocated and not freed when
writing a PNG image.
Also in this release the build process has been converted to
GNU autoconf/automake/libtool conventions so that both (or either)
static and shared libraries can be built.
Unlike gd 1.6, users should have no trouble linking with
gd 1.6.1 if they follow the instructions and install all of
the pieces. However, If you get undefined symbol errors,
be sure to check for older versions of libpng in your
library directories!
Support for 8-bit palette PNG images has been added.
Support for GIF has been removed. This step was taken
to completely avoid the legal controversy regarding the LZW
compression algorithm used in GIF. Unisys holds a patent which
is relevant to LZW compression. PNG is a superior image format
in any case. Now that PNG is supported by both Microsoft
Internet Explorer and Netscape (in their recent releases),
we highly recommend that GD users upgrade in order to get
well-compressed images in a format which is legally unemcumbered.
This format also supports version numbers and rudimentary validity
checks, so it should be more 'supportable' than the previous GD format.
To use gd, you will need an ANSI C compiler. All popular
Windows 95 and NT C compilers are ANSI C compliant. Any
full-ANSI-standard C compiler should be adequate. The cc
compiler released with SunOS 4.1.3 is not an ANSI C compiler.
Most Unix users who do not already have gcc should get it.
gcc is free, ANSI compliant and a de facto industry standard.
Ask your ISP why it is missing.
As of version 1.6, you also need the zlib compression library,
and the libpng library. As of version 1.6.2, you can draw text
using antialiased TrueType fonts if you also have the libttf
library installed, but this is not mandatory.
zlib is available for a variety of platforms from
the zlib web site.
libpng is available for a variety of platforms from
the PNG web site.
You will also want a PNG viewer, if you do not already have
one for your system, since you will need a good way to check the
results of your work. Netscape 4.04 and higher, and Microsoft
Internet Explorer 4.0 or higher, both support PNG.
Not every PNG-compatible viewer supports alpha channel
transparency, which is why gd 2.0.2 and above do alpha
blending in the library by default; it is possible to turn on the
saving of alpha channel information to the file instead.
In order to build gd, you must first unpack the archive you have
downloaded. If you are not familiar with
Unpacking the archive will produce a directory called "gd-2.0.33".
If all goes well, this will create a Makefile. If all does not go well --
for instance, if neither the the JPEG nor the PNG and ZLIB libraries
are found -- you will need to install those libraries, then come back
and run
If necessary, make changes to the resulting Makefile. Then,
type "make". If there are no errors, follow this with "make install".
Because gd 2.0 and above installs as a shared library, it is necessary to
install the library properly before running gd-based programs.
If you get errors, type
Create a project using your favorite programming environment.
Copy all of the gd files to the project directory. Add
If you wish to test the library, type "make test" AFTER you have
successfully executed "make install". This will build
several test programs, including "gddemo". (Not all of these
programs are expected to print completely successful messages,
depending on the nature of the image formats with which some of
the tests are tried; for instance, WBMP is a black and white
format, so loss of color information is expected there.)
Run gddemo to see some of the capabilities of gd. Run
gdtestft to play with the freetype support, if you have built
gd with it and have access to truetype fonts.
gddemo should execute without incident, creating the file
demoout.png. (Note there is also a file named demoin.png,
which is provided in the package as part of the demonstration.)
Display demoout.png in your PNG viewer. The image should
be 128x128 pixels and should contain an image of the
space shuttle with quite a lot of graphical elements drawn
on top of it.
(If you are missing the demoin.png file, the other items
should appear anyway.)
Look at demoin.png to see the original space shuttle
image which was scaled and copied into the output image.
If you want to use the provided simple fonts, include
gdfontt.h, gdfonts.h, gdfontmb.h, gdfontl.h and/or gdfontg.h. For
more impressive results, install FreeType 2.x and use the
gdImageStringFT
function. If you are not using the provided Makefile and/or a
library-based approach, be sure to include the source modules as well in your
project. (They may be too large for 16-bit memory models,
that is, 16-bit DOS and Windows.)
Here is a short example program. (For a more advanced example,
see gddemo.c, included in the distribution. gddemo.c is NOT the same program;
it demonstrates additional features!)
The above example program should
give you an idea of how the package works.
gd provides many additional functions, which are listed
in the following reference chapters, complete with code
snippets demonstrating each. There is also an
alphabetical index.
webpng.c is provided in the distribution. Unix users can
simply type "make webpng" to compile the program. Type
"webpng" with no arguments to see the available options.
The
The order of the structure members may appear confusing, but was chosen
deliberately to increase backwards compatibility with existing gd 1.x-based
binary code that references particular structure members.
Truecolor images are always filled with black at creation time.
There is no concept of a "background" color index.
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromJpegPtr, which is otherwise identical
to gdImageCreateFromJpeg.
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromPngPtr, which is otherwise identical
to gdImageCreateFromPng.
If the PNG image being loaded is a truecolor image, the resulting
gdImagePtr will refer to a truecolor image. If the PNG image
being loaded is a palette or grayscale image, the resulting
gdImagePtr will refer to a palette image. gd retains only 8 bits
of resolution for each of the red, green and blue channels, and
only 7 bits of resolution for the alpha channel. The former
restriction affects only a handful of very rare 48-bit color
and 16-bit grayscale PNG images. The second restriction affects
all semitransparent PNG images, but the difference is essentially
invisible to the eye. 7 bits of alpha channel resolution is,
in practice, quite a lot.
gdImageCreateFromPngSource is called to load a PNG from
a data source other than a file. Usage is very similar to
the gdImageCreateFromPng function,
except that the programmer provides a custom data source.
The programmer must write an input function which accepts
a context pointer, a buffer, and a number of bytes to be
read as arguments. This function must read the number of
bytes requested, unless the end of the file has been reached,
in which case the function should return zero, or an error
has occurred, in which case the function should return
The example below
implements gdImageCreateFromPng
by creating a custom data source and invoking gdImageCreateFromPngSource.
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromGifPtr, which is otherwise identical
to gdImageCreateFromGif.
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromGdPtr, which is otherwise identical
to gdImageCreateFromGd.
gdImageCreateFromGd
returns a gdImagePtr to the new image, or NULL
if unable to load the image (most often because the file is corrupt or
does not contain a gd format image). gdImageCreateFromGd does not
close the file. You can inspect the sx and sy members of the
image to determine its size. The image must eventually be destroyed
using gdImageDestroy().
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromGd2Ptr, which is otherwise identical
to gdImageCreateFromGd2.
gdImageCreateFromGd2
returns a gdImagePtr to the new image, or NULL
if unable to load the image (most often because the file is corrupt or
does not contain a gd format image). gdImageCreateFromGd2 does not
close the file. You can inspect the sx and sy members of the
image to determine its size. The image must eventually be destroyed
using gdImageDestroy().
If you already have the image file in memory, you may use
gdImageCreateFromGd2PartPtr. Pass the size of the image file,
in bytes, as the first argument and the pointer to the image file data
as the second argument.
If you already have the
image file in memory, pass the size of the file and a pointer to the
file's data to gdImageCreateFromWBMPPtr, which is otherwise identical
to gdImageCreateFromWBMP.
If quality is negative, the default IJG JPEG quality value (which
should yield a good general quality / size tradeoff for most
situations) is used. Otherwise, for practical purposes, quality
should be a value in the range 0-95, higher quality values usually
implying both higher quality and larger image sizes.
If you have set image interlacing using
gdImageInterlace, this function will
interpret that to mean you wish to output a progressive JPEG. Some
programs (e.g., Web browsers) can display progressive JPEGs
incrementally; this can be useful when browsing over a relatively slow
communications link, for example. Progressive JPEGs can also be
slightly smaller than sequential (non-progressive) JPEGs.
GIF does not support true color; GIF images can contain a maximum
of 256 colors. If the image to be written is a
truecolor image, such as those created with
gdImageCreateTrueColor or loaded
from a JPEG or a truecolor PNG image file, a palette-based
temporary image will automatically be created internally using the
gdImageCreatePaletteFromTrueColor function. The original image pixels are not modified. This conversion
produces high quality palettes but does require some CPU time. If you are
regularly converting truecolor to palette in this way, you should consider
creating your image as a palette-based image in the first place.
The GlobalCM flag indicates if a global color map (or palette) is used
in the GIF89A header. A nonzero value specifies that a global color
map should be used to reduce the size of the animation.
Of course, if the color maps of
individual frames differ greatly, a global color map may not be a good idea.
GlobalCM=1 means write global color map, GlobalCM=0 means do not, and
GlobalCM=-1 means to do the default, which currently is to use a global
color map.
If Loops is 0 or greater, the Netscape 2.0 extension for animation
loop count is written. 0 means infinite loop count. -1 means that
the extension is not added which results in no looping. -1 is the
default.
Setting the LocalCM flag to 1 adds a local palette for this image to the
animation. Otherwise the global palette is assumed and the user must make
sure the palettes match. Use gdImagePaletteCopy to do that.
Automatic optimization is activated by giving the previous image as a
parameter. This function then compares the images and only writes the changed
pixels to the new frame in animation. The Disposal parameter for
optimized animations must be set to 1, also for the first frame.
LeftOfs and TopOfs parameters are ignored for optimized frames. To
achieve good optimization, it is usually best to use a single global
color map. To allow gdImageGifAnimAdd to compress unchanged pixels via
the use of a transparent color, the image must include a transparent color.
For more information, see gdImagePng.
For more information, see gdImagePngPtr.
The programmer must write an output function which accepts
a context pointer, a buffer, and a number of bytes to be
written as arguments. This function must write the number of
bytes requested and return that number, unless an error
has occurred, in which case the function should return
The example below
implements gdImagePng
by creating a custom data source and invoking gdImagePngFromSink.
WBMP file support is black and white only. The color index
specified by the fg argument is the "foreground," and only pixels
of this color will be set in the WBMP file. All other pixels
will be considered "background."
The gd image format is intended for fast reads and writes of
images your program will need frequently to build other
images. It is not a compressed format, and is not intended
for general use.
The gd2 image format is intended for fast reads and writes of
parts of images.
It is a compressed format, and well suited to retrieving smll sections of
much larger images.
The third and fourth parameters are the 'chunk size' and format resposectively.
The file is stored as a series of compressed subimages, and the
Chunk Size determines the sub-image size - a value of
zero causes the GD library to use the default.
It is also possible to store GD2 files in an uncompressed format, in which case the
fourth parameter should be GD2_FMT_RAW.
The function converts a truecolor image to a palette-based image,
using a high-quality two-pass quantization routine.
If ditherFlag is set, the image will be
dithered to approximate colors better, at the expense
of some obvious "speckling." colorsWanted can be
anything up to 256. If the original source image
includes photographic information or anything that
came out of a JPEG, 256 is strongly recommended.
100% transparency of a single transparent color in the
original truecolor image will be preserved. There is no other
support for preservation of alpha channel or transparency in
the destination image.
For best results, don't use this function -- write real
truecolor PNGs and JPEGs. The disk space gain of
conversion to palette is not great (for small images
it can be negative) and the quality loss is ugly. However,
the version of this function included in version 2.0.12 and later does
do a better job than the version included prior to 2.0.12.
gdImageDashedLine is used to draw a dashed line between two endpoints
(x1,y1 and x2, y2).
The line is drawn using the color index specified. The portions of the line
that are not drawn are left transparent so the background is visible.
What's new in version 1.6.2?
Version 1.6.2 from John Ellson
if ((color=gdImageColorExact(im,R,G,B)) < 0)
if ((color=gdImageColorAllocate(im,R,G,B)) < 0)
color=gdImageColorClosest(im,R,G,B);
What's new in version 1.6.1?
Version 1.6.1 incorporates superior PNG reading and writing code
from Greg Roelofs, with minor modifications by Tom Boutell.
Specifically, I altered his code to read non-palette images
(converting them to palette images badly, by dithering them),
and to tolerate palette images with types of transparency that
gd doesn't actually support (it just ignores the advanced
transparency features). Any bugs in this area are therefore my
fault, not Greg's.
What's new in version 1.6?
Version 1.6 features the following changes:
What's new in version 1.5?
Version 1.5 featured the following changes:
NOTE: In fairness to Thomas Boutell, any bug/problems with any of the above features should
probably be reported to Philip Warner.
gdImagePaletteCopy - Copies a palette from one image to another, doing it's best to match the colors in the target image to the colors in the source palette.
gdImageGd2, gdImageCreateFromGd2 - Support for new format
gdImageCopyMerge - Merges two images (useful to highlight part of an image)
gdImageCopyMergeGray - Similar to gdImageCopyMerge, but tries to preserve source image hue.
gdImagePngPtr, gdImageJpegPtr, gdImageWBMPPtr, gdImageGdPtr, gdImageGd2Ptr - return memory blocks for each type of image.
gdImageCreateFromPngCtx, gdImageCreateFromGdCtx, gdImageCreateFromGd2Ctx, gdImageCreateFromGd2PartCtx - Support for new I/O context.
What's new in version 1.4?
Version 1.4 features the following changes:
What's new in version 1.3?
Version 1.3 features the following changes:
pixels array will require
changes.
What else do I need to use gd?
Binaries (DLL for Windows programmers):
Source Code:
Win32 DLL users: if you are using MSVC, use the provided batch file
Building gd From the Source
makemsvcimport.bat to make a bgd.lib import library
corresponding to the provided bgd.dll. Copy bgd.dll to your
application directory, or to your Windows sytem directory. In the
settings of your MSVC project, you MUST choose the
"multithreaded DLL" library option under "code generation."
mingw32 and cygwin users can simply link with the provided libbgd.a
stub library in order to use the DLL.
tar and
gunzip (Unix) or ZIP (Windows), please
consult with an experienced user of your system. Sorry, we cannot
answer questions about basic Internet skills.
For Unix
cd to the 2.0.33 directory and type:
./configure
NOTE: BY DEFAULT, THE LIBRARY IS INSTALLED IN
/usr/local/lib and the include files are
installed in /usr/local/include. IF YOU ARE
UPGRADING, you may wish to use:
./configure --prefix=/usr
Rather than just ./configure, before typing
make and make install.
configure again.
./configure --help for more
information about the available options. In the unlikely event
that the GNU autoconf-produced configure script does not work well
for you, you may wish to try configure.pl, a
simple Perl script with similar but less complete capabilities.
If all else fails, try renaming makefile.sample
to Makefile. However, ./configure is
almost always your best bet.
For Windows
Use the DLL version! See the paragraph at the beginning of this sectino.
If you really want to compile it yourself for some strange reason, read on.
gd.c
to your project. Add other source files as appropriate. Learning the
basic skills of creating projects with your chosen C environment
is up to you. Alternatively, use the free mingw32
or cygwin tools, which may prove to be compatible
with the provided configure script.
gd basics: using gd in your program
gd lets you create PNG or JPEG images on the fly. To use gd in your
program, include the file gd.h, and link with the gd
library and the other required libraries; the syntax for
most Unix flavors is:
-lgd -lpng -lz -ljpeg -lfreetype -lm
Assuming that all of these libraries are available.
/* Bring in gd library functions */
#include "gd.h"
/* Bring in standard I/O so we can output the PNG to a file */
#include <stdio.h>
int main() {
/* Declare the image */
gdImagePtr im;
/* Declare output files */
FILE *pngout, *jpegout;
/* Declare color indexes */
int black;
int white;
/* Allocate the image: 64 pixels across by 64 pixels tall */
im = gdImageCreate(64, 64);
/* Allocate the color black (red, green and blue all minimum).
Since this is the first color in a new image, it will
be the background color. */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a line from the upper left to the lower right,
using white color index. */
gdImageLine(im, 0, 0, 63, 63, white);
/* Open a file for writing. "wb" means "write binary", important
under MSDOS, harmless under Unix. */
pngout = fopen("test.png", "wb");
/* Do the same for a JPEG-format file. */
jpegout = fopen("test.jpg", "wb");
/* Output the image to the disk file in PNG format. */
gdImagePng(im, pngout);
/* Output the same image in JPEG format, using the default
JPEG quality setting. */
gdImageJpeg(im, jpegout, -1);
/* Close the files. */
fclose(pngout);
fclose(jpegout);
/* Destroy the image in memory. */
gdImageDestroy(im);
}
When executed, this program creates an image, allocates
two colors (the first color allocated becomes the background
color), draws a diagonal line (note that 0, 0 is the upper
left corner), writes the image to PNG and JPEG files, and
destroys the image.
Webpng: a more powerful gd example
Webpng is a simple utility program to manipulate PNGs from the
command line. It is written for Unix and similar command-line
systems, but should be easily adapted for other environments.
Webpng allows you to set transparency and interlacing and
output interesting information about the PNG in question.
Function and type reference
Types
gdImage(TYPE)
pixels
or tpixels arrays. If the trueColor flag
is set, the tpixels array is valid; otherwise the
pixels array is valid.
colorsTotal, red, green,
blue, alpha and open arrays
manage the palette. They are valid only when the trueColor
flag is not set.
The transparent value contains the palette index of the first
transparent color as read-only information for backwards compatibility;
gd 2.0 stores this information in the alpha array so that
variable transparency can be supported for each palette entry. However,
for truecolor images, transparent represents a single
RGB color which is always 100% transparent, and this
feature is generally supported by browsers which do not support
full alpha channels.
typedef struct {
/* Palette-based image pixels */
unsigned char ** pixels;
int sx;
int sy;
/* These are valid in palette images only. See also
/* 'alpha', which appears later in the structure to
preserve binary backwards compatibility */
int colorsTotal;
int red[gdMaxColors];
int green[gdMaxColors];
int blue[gdMaxColors];
int open[gdMaxColors];
/* For backwards compatibility, this is set to the
first palette entry with 100% transparency,
and is also set and reset by the
gdImageColorTransparent function. Newer
applications can allocate palette entries
with any desired level of transparency; however,
bear in mind that many viewers, notably
many web browsers, fail to implement
full alpha channel for PNG and provide
support for full opacity or transparency only. */
int transparent;
int *polyInts;
int polyAllocated;
struct gdImageStruct *brush;
struct gdImageStruct *tile;
int brushColorMap[gdMaxColors];
int tileColorMap[gdMaxColors];
int styleLength;
int stylePos;
int *style;
int interlace;
/* New in 2.0: alpha channel for palettes. Note that only
Macintosh Internet Explorer and (possibly) Netscape 6
really support multiple levels of transparency in
palettes, to my knowledge, as of 2/15/01. Most
common browsers will display 100% opaque and
100% transparent correctly, and do something
unpredictable and/or undesirable for levels
in between. TBB */
int alpha[gdMaxColors];
/* Truecolor flag and pixels. New 2.0 fields appear here at the
end to minimize breakage of existing object code. */
int trueColor;
int ** tpixels;
/* Should alpha channel be copied, or applied, each time a
pixel is drawn? This applies to truecolor images only.
No attempt is made to alpha-blend in palette images,
even if semitransparent palette entries exist.
To do that, build your image as a truecolor image,
then quantize down to 8 bits. */
int alphaBlendingFlag;
/* Should the alpha channel of the image be saved? This affects
PNG at the moment; other future formats may also
have that capability. JPEG doesn't. */
int saveAlphaFlag;
} gdImage;
gd2 file format, which supports quick loading of
partial images. The gd_free function will not be invoked when
calling the standard Ctx functions; it is an implementation
convenience when adding new data types to gd. For examples,
see gd_png.c, gd_gd2.c, gd_jpeg.c, etc., all of which rely
on gdIOCtx to implement the standard image read and write functions.
typedef struct gdIOCtx
{
int (*getC) (struct gdIOCtx *);
int (*getBuf) (struct gdIOCtx *, void *, int wanted);
void (*putC) (struct gdIOCtx *, int);
int (*putBuf) (struct gdIOCtx *, const void *, int wanted);
/* seek must return 1 on SUCCESS, 0 on FAILURE. Unlike fseek! */
int (*seek) (struct gdIOCtx *, const int);
long (*tell) (struct gdIOCtx *);
void (*gd_free) (struct gdIOCtx *);
} gdIOCtx;
typedef struct {
/* # of characters in font */
int nchars;
/* First character is numbered... (usually 32 = space) */
int offset;
/* Character width and height */
int w;
int h;
/* Font data; array of characters, one row after another.
Easily included in code, also easily loaded from
data files. */
char *data;
} gdFont;
typedef struct {
int x, y;
} gdPoint, *gdPointPtr;
typedef struct {
int (*source) (void *context, char *buffer, int len);
void *context;
} gdSource, *gdSourcePtr;
Represents a source from which a PNG can be read.
Programmers who do not wish to read PNGs from a file can provide
their own alternate input mechanism, using the
gdImageCreateFromPngSource function.
See the documentation of that function for an example of the
proper use of this type.
typedef struct {
int (*sink) (void *context, char *buffer, int len);
void *context;
} gdSink, *gdSinkPtr;
Represents a "sink" (destination) to which a PNG can be written.
Programmers who do not wish to write PNGs to a file can provide
their own alternate output mechanism, using the
gdImagePngToSink function.
See the documentation of that function for an example of the
proper use of this type.
Image creation, destruction, loading and saving
... inside a function ...
gdImagePtr im;
im = gdImageCreate(64, 64);
/* ... Use the image ... */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
im = gdImageCreateTrueColor(64, 64);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromJpegPtr(int size, void *data)
(FUNCTION)
gdImageCreateFromJpegCtx(gdIOCtx *in)
(FUNCTION)
gdImagePtr im;
... inside a function ...
FILE *in;
in = fopen("myjpeg.jpg", "rb");
im = gdImageCreateFromJpeg(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromPngPtr(int size, void *data)
(FUNCTION)
gdImageCreateFromPngCtx(gdIOCtx *in)
(FUNCTION)
gdImagePtr im;
... inside a function ...
FILE *in;
in = fopen("mypng.png", "rb");
im = gdImageCreateFromPng(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
-1. The programmer then creates a
gdSource structure and sets
the source pointer to the input function and
the context pointer to any value which is useful to the
programmer.
static int freadWrapper(void *context, char *buf, int len);
gdImagePtr gdImageCreateFromPng(FILE *in)
{
gdSource s;
s.source = freadWrapper;
s.context = in;
return gdImageCreateFromPngSource(&s);
}
static int freadWrapper(void *context, char *buf, int len)
{
int got = fread(buf, 1, len, (FILE *) context);
return got;
}
gdImageCreateFromGifPtr(int size, void *data)
(FUNCTION)
gdImageCreateFromGifCtx(gdIOCtx *in)
(FUNCTION)
gdImagePtr im;
... inside a function ...
FILE *in;
in = fopen("mygif.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromGdCtx(gdIOCtx *in)
(FUNCTION)
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("mygd.gd", "rb");
im = gdImageCreateFromGd(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromGd2Ptr(int size, void *data)
(FUNCTION)
gdImageCreateFromGd2Ctx(gdIOCtx *in)
(FUNCTION)
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("mygd.gd2", "rb");
im = gdImageCreateFromGd2(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromGd2PartPtr(int size, void *data, int srcX, int srcY, int w, int h)
(FUNCTION)
gdImageCreateFromGd2PartCtx(gdIOCtx *in)
(FUNCTION)
gdImageCreateFromWBMPPtr(int size, void *data)
(FUNCTION)
gdImageCreateFromWBMPCtx(gdIOCtx *in)
(FUNCTION)
gdImagePtr im;
... inside a function ...
FILE *in;
in = fopen("mywbmp.wbmp", "rb");
im = gdImageCreateFromWBMP(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("myxbm.xbm", "rb");
im = gdImageCreateFromXbm(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("myxpm.xpm", "rb");
im = gdImageCreateFromXpm(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
im = gdImageCreate(10, 10);
/* ... Use the image ... */
/* Now destroy it */
gdImageDestroy(im);
void gdImageJpegCtx(gdImagePtr im, gdIOCtx *out, int quality)
(FUNCTION)
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.jpg", "wb");
/* Write JPEG using default quality */
gdImageJpeg(im, out, -1);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
void gdImageGifCtx(gdImagePtr im, gdIOCtx *out)
(FUNCTION)
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.gif", "wb");
/* Write GIF */
gdImageGif(im, out);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
void gdImageGifAnimBeginCtx(gdImagePtr im, gdIOCtx *out, int GlobalCM, int Loops)
(FUNCTION)
void gdImageGifAnimAddCtx(gdImagePtr im, gdIOCtx *out, int LocalCM, int LeftOfs, int TopOfs, int Delay, int Disposal, gdImagePtr previm)
(FUNCTION)
gdDisposalNone, meaning that the pixels changed by this
frame should remain on the display when the next frame begins to render, but
can also be gdDisposalUnknown (not recommended),
gdDisposalRestoreBackground (restores the first
allocated color of the global palette), or
gdDisposalRestorePrevious (restores the appearance of the
affected area before the frame was rendered). Only
gdDisposalNone is a sensible choice for the first frame.
If previm is
passed, the built-in GIF optimizer will always use gdDisposalNone
regardless of the Disposal parameter.
... inside a function ...
gdImagePtr im, im2, im3;
int black, white, trans;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate transparent color for animation compression */
trans = gdImageColorAllocate(im, 1, 1, 1);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 10, 10, black);
/* Open output file in binary mode */
out = fopen("anim.gif", "wb");
/* Write GIF header. Use global color map. Loop a few times */
gdImageGifAnimBegin(im, out, 1, 3);
/* Write the first frame. No local color map. Delay = 1s */
gdImageGifAnimAdd(im, out, 0, 0, 0, 100, 1, NULL);
/* construct the second frame */
im2 = gdImageCreate(100, 100);
/* Allocate background to make it white */
(void)gdImageColorAllocate(im2, 255, 255, 255);
/* Make sure the palette is identical */
gdImagePaletteCopy (im2, im);
/* Draw something */
gdImageRectangle(im2, 0, 0, 15, 15, black);
/* Allow animation compression with transparent pixels */
gdImageColorTransparent (im2, trans);
/* Add the second frame */
gdImageGifAnimAdd(im2, out, 0, 0, 0, 100, 1, im);
/* construct the second frame */
im3 = gdImageCreate(100, 100);
/* Allocate background to make it white */
(void)gdImageColorAllocate(im3, 255, 255, 255);
/* Make sure the palette is identical */
gdImagePaletteCopy (im3, im);
/* Draw something */
gdImageRectangle(im3, 0, 0, 15, 20, black);
/* Allow animation compression with transparent pixels */
gdImageColorTransparent (im3, trans);
/* Add the third frame, compressing against the second one */
gdImageGifAnimAdd(im3, out, 0, 0, 0, 100, 1, im2);
/* Write the end marker */
/* gdImageGifAnimEnd(out); is the same as the following: */
putc (';', out);
/* Close file */
fclose(out);
/* Destroy images */
gdImageDestroy(im);
gdImageDestroy(im2);
gdImageDestroy(im3);
void gdImageGifAnimEndCtx(gdIOCtx *out)
(FUNCTION)
void gdImagePngCtx(gdImagePtr im, gdIOCtx *out)
(FUNCTION)
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.png", "wb");
/* Write PNG */
gdImagePng(im, out);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
void gdImagePngCtxEx(gdImagePtr im, gdIOCtx *out, int level)
(FUNCTION)
-1. The programmer then creates a
gdSink structure and sets
the sink pointer to the output function and
the context pointer to any value which is useful to the
programmer.
static int stdioSink(void *context, char *buffer, int len)
{
return fwrite(buffer, 1, len, (FILE *) context);
}
void gdImagePng(gdImagePtr im, FILE *out)
{
gdSink mySink;
mySink.context = (void *) out;
mySink.sink = stdioSink;
gdImagePngToSink(im, &mySink);
}
gdImageWBMPCtx(gdIOCtx *out)
(FUNCTION)(FUNCTION)
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.wbmp", "wb");
/* Write WBMP, with black as foreground */
gdImageWBMP(im, black, out);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.gd", "wb");
/* Write gd format file */
gdImageGd(im, out);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
void gdImageGd2Ctx(gdImagePtr im, gdIOCtx *out, int chunkSize, int fmt)
(FUNCTION)
... inside a function ...
gdImagePtr im;
int black, white;
FILE *out;
/* Create the image */
im = gdImageCreate(100, 100);
/* Allocate background */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate drawing color */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Draw rectangle */
gdImageRectangle(im, 0, 0, 99, 99, black);
/* Open output file in binary mode */
out = fopen("rect.gd", "wb");
/* Write gd2 format file */
gdImageGd2(im, out, 0, GD2_FMT_COMPRESSED);
/* Close file */
fclose(out);
/* Destroy image */
gdImageDestroy(im);
gdImagePtr gdImageCreatePaletteFromTrueColor(gdImagePtr im, int ditherFlag, int colorsWanted)
(FUNCTION)
gdImageCreatePaletteFromTrueColor returns a new
image. gdImageTrueColorToPalette permanently converts the
existing image. The two functions are otherwise identical.
Drawing Functions
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Set a pixel near the center. */
gdImageSetPixel(im, 50, 50, white);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green
and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a line from the upper left corner to the
lower right corner. */
gdImageLine(im, 0, 0, 99, 99, white);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue
all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a dashed line from the upper left corner
to the lower right corner. */
gdImageDashedLine(im, 0, 0, 99, 99);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black;
int white;
/* Points of polygon */
gdPoint points[3];
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and
blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a triangle. */
points[0].x = 50;
points[0].y = 0;
points[1].x = 99;
points[1].y = 99;
points[2].x = 0;
points[2].y = 99;
gdImagePolygon(im, points, 3, white);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a rectangle occupying the central area. */
gdImageRectangle(im, 25, 25, 74, 74, white);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
... inside a function ...
gdImagePtr im;
int black;
int white;
int red;
/* Points of polygon */
gdPoint points[3];
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Allocate the color red. */
red = gdImageColorAllocate(im, 255, 0, 0);
/* Draw a triangle. */
points[0].x = 50;
points[0].y = 0;
points[1].x = 99;
points[1].y = 99;
points[2].x = 0;
points[2].y = 99;
/* Paint it in white */
gdImageFilledPolygon(im, points, 3, white);
/* Outline it in red; must be done second */
gdImagePolygon(im, points, 3, red);
/* ... Do something with the image, such as
saving it to a file... */
/* Destroy it */
gdImageDestr