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. Although his LZW compression
code no longer appears in gd, the authors wish to thank David Rowley
for the original LZW-based GIF compression code, which has been removed
due to patent concerns.If you are aware of any oversights
in this copyright notice, please contact
Thomas Boutell who will be
pleased to correct them.
COPYRIGHT STATEMENT FOLLOWS THIS LINE
Portions copyright 1994, 1995, 1996, 1997, 1998, by Cold Spring
Harbor Laboratory. Funded under Grant P41-RR02188 by the National
Institutes of Health.
Portions copyright 1996, 1997, 1998, by Boutell.Com, Inc.
GIF decompression code copyright 1990, 1991, 1993, by David Koblas
(koblas@netcom.com).
Permission has been granted to copy and distribute gd in any
context, 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.
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation. This software is provided "as is" without express or
implied warranty.
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 .GIF file. This is particularly
useful in World Wide Web applications, where .GIF is the
format used for inline images.
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.
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 1.3 incorporates
most of the commonly requested features for an 8-bit 2D package.
Support for scalable fonts, and truecolor images, JPEG and PNG
is planned for version 2.0. Version 1.3 was released to correct
longstanding bugs and provide an LZW-free GIF compression routine.
gd can also be used from Perl, courtesy of
Lincoln Stein's
GD.pm library, which uses gd as the basis for a set of
Perl 5.x classes. GD.pm is based on gd 1.1.1 but gd 1.2 should
be compatible.
Any Language
There are, at the moment, at least three simple interpreters that
perform gd operations. You can output the desired commands to a simple
text file from whatever scripting language you prefer to use, then
invoke the interpreter.
These packages are based on gd 1.2 as of this writing but should
be compatible with gd 1.3 with minimal tweaking.
Version 1.3 contains GIF compression code that uses simple Run Length
Encoding instead of LZW compression, while still retaining compatibility
with normal LZW-based GIF decoders (your browser will still like your GIFs).
LZW compression is patented by Unisys. This is why there have
been no new versions of gd for a long time. THANKS to
Hutchison Avenue Software Corporation for contributing
this code. THE NEW CODE PRODUCES LARGER GIFS AND IS NOT WELL
SUITED TO PHOTOGRAPHIC IMAGES. THIS IS A LEGAL ISSUE.
IT IS NOT A QUESTION OF TECHNICAL SKILL. PLEASE DON'T
COMPLAIN ABOUT THE SIZE OF GIF OUTPUT. THANKS!
8-bit fonts, and 8-bit font support
This improves support for European languages. Thanks are due
to Honza Pazdziora and also to
Jan Pazdziora . Also see the provided bdftogd
Perl script if you wish to convert fixed-width X11 fonts
to gd fonts.
16-bit font support (no fonts provided)
Although no such fonts are provided in the distribution,
fonts containing more than 256 characters should work if the
gdImageString16 and gdImageStringUp16 routines are used.
Improvements to the "webgif" example/utility
The "webgif" utility is now a slightly more useful application. Thanks to
Brian Dowling for this code.
Corrections to the color resolution field of GIF output
Thanks to Bruno Aureli.
Fixed polygon fills
A one-line patch for the infamous polygon fill bug, courtesy
of Jim Mason. I believe this fix is sufficient. However, if you
find a situation where polygon fills still fail to behave properly,
please send code that demonstrates the problem, and a fix if
you have one. Verifying the fix is important.
Row-major, not column-major
Internally, gd now represents the array of pixels as
an array of rows of pixels, rather than an array of columns
of pixels. This improves the performance of compression and
decompression routines slightly, because horizontally adjacent
pixels are now next to each other in memory. This should
not affect properly written gd applications, but applications that
directly manipulate the pixels array will require
changes.
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.
You will also want a GIF 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. Any web browser will work, but you might
be happier with a package like Lview Pro for Windows or
xv for X. There are GIF viewers available for every graphics-capable
computer out there, so consult newsgroups relevant to
your particular system.
In order to build gd, you must first unpack the archive you have
downloaded. If you are not familiar with 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.
Unpacking the archive will produce a directory called "gd1.3".
For Unix
cd to the gd1.3 directory and examine the Makefile, which
you will probably need to change slightly depending on your operating
system and your needs.
For Windows, Mac, Et Cetera
Create a project using your favorite programming environment.
Copy all of the gd files to the project directory. Add 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.
Now, to build the demonstration program, just type "make gddemo"
if you are working in a command-line environment, or build a project
that includes gddemo.c if you are using a graphical environment. If all
goes well, the program "gddemo" will be compiled and linked without incident.
Depending on your system you may need to edit the Makefile.
Understanding the basic techniques of compiling and linking
programs on your system is up to you.
You have now built a demonstration program which shows off
the capabilities of gd. To see it in action, type
"gddemo".
gddemo should execute without incident, creating the file
demoout.gif. (Note there is also a file named demoin.gif,
which is provided in the package as part of the demonstration.)
Display demoout.gif in your GIF 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.gif file, the other items
should appear anyway.)
Look at demoin.gif to see the original space shuttle
image which was scaled and copied into the output image.
gd lets you create GIF images on the fly. To use gd in your
program, include the file gd.h, and link with the libgd.a
library produced by "make libgd.a", under Unix. Under other
operating systems you will add gd.c to your own project.
If you want to use the provided fonts, include
gdfontt.h, gdfonts.h, gdfontmb.h, gdfontl.h and/or gdfontg.h. 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!)
/* Bring in gd library functions */
#include "gd.h"
/* Bring in standard I/O so we can output the GIF to a file */
#include <stdio.h>
int main() {
/* Declare the image */
gdImagePtr im;
/* Declare an output file */
FILE *out;
/* 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. */
out = fopen("test.gif", "wb");
/* Output the image to the disk file. */
gdImageGif(im, out);
/* Close the file. */
fclose(out);
/* 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 a GIF file, and
destroys the image.
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.
Webgif is a simple utility program to manipulate GIFs from the
command line. It is written for Unix and similar command-line
systems, but should be easily adapted for other environments.
Webgif allows you to set transparency and interlacing and
output interesting information about the GIF in question.
webgif.c is provided in the distribution. Unix users can
simply type "make webgif" to compile the program. Type
"webgif" with no arguments to see the available options.
The data structure in which gd stores images.
gdImageCreate returns
a pointer to this type, and the other functions expect to receive
a pointer to this type as their first argument. You may
read the members sx (size on X axis),
sy (size on Y axis), colorsTotal
(total colors), red (red component of colors;
an array of 256 integers between 0 and 255), green
(green component of colors, as above), blue
(blue component of colors, as above), and transparent
(index of transparent color, -1 if none); please do so
using the macros provided. Do NOT set the members directly
from your code; use the functions provided.
typedef struct {
unsigned char ** pixels;
int sx;
int sy;
int colorsTotal;
int red[gdMaxColors];
int green[gdMaxColors];
int blue[gdMaxColors];
int open[gdMaxColors];
int transparent;
} gdImage;
A font structure. Used to declare the characteristics of a font.
Plese see the files gdfontl.c and gdfontl.h for an example of the
proper declaration of this structure. You can provide your
own font data by providing such a structure and the associated
pixel array. You can determine the width and height of a single
character in a font by examining the w and h members of the
structure. If you will not be creating your own fonts, you will
not need to concern yourself with the rest of the components of this
structure.
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;
A pointer to a font structure. Text-output functions expect these
as their second argument, following the
gdImagePtr argument. Two such pointers are declared in the
provided include files gdfonts.h and gdfontl.h.
gdImageCreate is called to create images. Invoke gdImageCreate
with the x and y dimensions of the desired image. gdImageCreate
returns a gdImagePtr to the new image, or
NULL if unable to
allocate the image. The image must eventually be destroyed
using gdImageDestroy().
... inside a function ...
gdImagePtr im;
im = gdImageCreate(64, 64);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromGif is called to load images from GIF format files.
Invoke gdImageCreateFromGif with an already opened pointer to a file
containing the desired image.
gdImageCreateFromGif
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 GIF image). gdImageCreateFromGif 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().
gdImagePtr im;
... inside a function ...
FILE *in;
in = fopen("mygif.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromGd is called to load images from gd format files.
Invoke gdImageCreateFromGd
with an already opened pointer to a file containing the desired image
in the gd file format, which is specific to
gd and intended for very fast loading. (It is not intended for
compression; for compression, use GIF.)
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().
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("mygd.gd", "rb");
im = gdImageCreateFromGd(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageCreateFromXbm is called to load images from X bitmap format
files. Invoke gdImageCreateFromXbm
with an already opened pointer to a file containing the desired image.
gdImageCreateFromXbm
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 an X bitmap format image). gdImageCreateFromXbm 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().
... inside a function ...
gdImagePtr im;
FILE *in;
in = fopen("myxbm.xbm", "rb");
im = gdImageCreateFromXbm(in);
fclose(in);
/* ... Use the image ... */
gdImageDestroy(im);
gdImageDestroy is used to free the memory associated with
an image. It is important to invoke gdImageDestroy before
exiting your program or assigning a new image to
a gdImagePtr variable.
gdImageGif outputs the specified image to the specified
file in GIF format. The file must be open for writing. Under MSDOS,
it is important to use "wb" as opposed to simply "w"
as the mode when opening the file, and under Unix there
is no penalty for doing so. gdImageGif does not
close the file; your code must do so.
... 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);
gdImageGd outputs the specified image to the specified
file in the gd image format. The file must
be open for writing. Under MSDOS, it is important to use "wb" as
opposed to simply "w" as the mode when opening the file, and under
Unix there is no penalty for doing so. gdImageGif does not
close the file; your code must do so.
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.
... 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);
gdImageSetPixel sets a pixel to a particular color index. Always use
this function or one of the other drawing functions to access pixels;
do not access the pixels of the gdImage structure
directly.
... 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);
gdImageLine is used to draw a line between two endpoints (x1,y1 and x2, y2).
The line is drawn using the color index specified. Note that the color
index can be an actual color returned by
gdImageColorAllocate or one of gdStyled,
gdBrushed or
gdStyledBrushed.
... 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);
gdImageDashedLine is provided solely for backwards compatibility
with gd 1.0. New programs should draw dashed lines using
the normal gdImageLine function and the
new gdImageSetStyle function.
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.
... 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);
gdImagePolygon is used to draw a polygon with the verticies
(at least 3) specified, using the color index specified.
See also gdImageFilledPolygon.
... 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);
gdImageRectangle is used to draw a rectangle with the two corners
(upper left first, then lower right) specified, using the
color index specified.
... 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);
gdImageFilledPolygon is used to fill a polygon with the verticies
(at least 3) specified, using the color index specified.
See also gdImagePolygon.
... 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 */
gdImageDestroy(im);
gdImageFilledRectangle is used to draw a solid rectangle with the two corners
(upper left first, then lower right) specified, using the
color index specified.
... 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 = int gdImageColorAllocate(im, 255, 255, 255);
/* Draw a filled rectangle occupying the central area. */
gdImageFilledRectangle(im, 25, 25, 74, 74, white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageArc is used to draw a partial ellipse centered at the given point,
with the specified width and height in pixels. The arc begins at
the position in degrees specified by s and ends at
the position specified by e. The arc is drawn in
the color specified by the last argument. A circle can be drawn
by beginning from 0 degrees and ending at 360 degrees, with
width and height being equal. e must be greater than s. Values greater
than 360 are interpreted modulo 360.
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 50);
/* 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);
/* Inscribe an ellipse in the image. */
gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
The border color cannot be a special color
such as gdTiled; it must be a proper
solid color. The fill color can be, however.
Note that gdImageFillToBorder is recursive. It is not the most
naive implementation possible, and the implementation is
expected to improve, but there will always be degenerate
cases in which the stack can become very deep. This can be
a problem in MSDOS and MS Windows environments. (Of course,
in a Unix or NT environment with a proper stack, this is
not a problem at all.)
... inside a function ...
gdImagePtr im;
int black;
int white;
int red;
im = gdImageCreate(100, 50);
/* 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);
/* Inscribe an ellipse in the image. */
gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
/* Flood-fill the ellipse. Fill color is red, border color is
white (ellipse). */
gdImageFillToBorder(im, 50, 50, white, red);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
The fill color can be gdTiled, resulting
in a tile fill using another image as the tile. However,
the tile image cannot be transparent. If the image you wish
to fill with has a transparent color index, call
gdImageTransparent on the
tile image and set the transparent color index to -1
to turn off its transparency.
Note that gdImageFill is recursive. It is not the most
naive implementation possible, and the implementation is
expected to improve, but there will always be degenerate
cases in which the stack can become very deep. This can be
a problem in MSDOS and MS Windows environments. (Of course,
in a Unix or NT environment with a proper stack, this is
not a problem at all.)
... inside a function ...
gdImagePtr im;
int black;
int white;
int red;
im = gdImageCreate(100, 50);
/* 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);
/* Inscribe an ellipse in the image. */
gdImageArc(im, 50, 25, 98, 48, 0, 360, white);
/* Flood-fill the ellipse. Fill color is red, and will replace the
black interior of the ellipse. */
gdImageFill(im, 50, 50, red);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
A "brush" is an image used to draw wide, shaped strokes in another image. Just
as a paintbrush is not a single point, a brush image need not be
a single pixel. Any gd image can be used as a brush, and by
setting the transparent color index of the brush image with
gdImageColorTransparent,
a brush of any shape can be created. All line-drawing functions,
such as gdImageLine and
gdImagePolygon, will use the
current brush if the special "color"
gdBrushed or gdStyledBrushed
is used when calling them.
gdImageSetBrush is used to specify the brush to be used in a
particular image. You can set any image to be the brush.
If the brush image does not have the same color map as the
first image, any colors missing from the first image
will be allocated. If not enough colors can be allocated,
the closest colors already available will be used. This
allows arbitrary GIFs to be used as brush images. It also
means, however, that you should not set a brush unless you
will actually use it; if you set a rapid succession of
different brush images, you can quickly fill your color map,
and the results will not be optimal.
You need not take any special action when you are finished
with a brush. As for any other image, if you will not
be using the brush image for any further purpose,
you should call gdImageDestroy.
You must not use the color gdBrushed
if the current brush has been destroyed; you can of
course set a new brush to replace it.
... inside a function ...
gdImagePtr im, brush;
FILE *in;
int black;
im = gdImageCreate(100, 100);
/* Open the brush GIF. For best results, portions of the
brush that should be transparent (ie, not part of the
brush shape) should have the transparent color index. */
in = fopen("star.gif", "rb");
brush = gdImageCreateFromGif(in);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
gdImageSetBrush(im, brush);
/* Draw a line from the upper left corner to the lower right corner
using the brush. */
gdImageLine(im, 0, 0, 99, 99, gdBrushed);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
/* Destroy the brush image */
gdImageDestroy(brush);
A "tile" is an image used to fill an area with a repeated pattern.
Any gd image can be used as a tile, and by
setting the transparent color index of the tile image with
gdImageColorTransparent,
a tile that allows certain parts of the underlying area to shine
through can be created. All region-filling functions,
such as gdImageFill and
gdImageFilledPolygon, will use the
current tile if the special "color"
gdTiled is used when calling them.
gdImageSetTile is used to specify the tile to be used in a
particular image. You can set any image to be the tile.
If the tile image does not have the same color map as the
first image, any colors missing from the first image
will be allocated. If not enough colors can be allocated,
the closest colors already available will be used. This
allows arbitrary GIFs to be used as tile images. It also
means, however, that you should not set a tile unless you
will actually use it; if you set a rapid succession of
different tile images, you can quickly fill your color map,
and the results will not be optimal.
You need not take any special action when you are finished
with a tile. As for any other image, if you will not
be using the tile image for any further purpose,
you should call gdImageDestroy.
You must not use the color gdTiled
if the current tile has been destroyed; you can of
course set a new tile to replace it.
... inside a function ...
gdImagePtr im, tile;
FILE *in;
int black;
im = gdImageCreate(100, 100);
/* Open the tile GIF. For best results, portions of the
tile that should be transparent (ie, allowing the
background to shine through) should have the transparent
color index. */
in = fopen("star.gif", "rb");
tile = gdImageCreateFromGif(in);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
gdImageSetTile(im, tile);
/* Fill an area using the tile. */
gdImageFilledRectangle(im, 25, 25, 75, 75, gdTiled);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
/* Destroy the tile image */
gdImageDestroy(tile);
It is often desirable to draw dashed lines, dotted lines, and other
variations on a broken line. gdImageSetStyle can be used to set
any desired series of colors, including a special color that
leaves the background intact, to be repeated during the drawing
of a line.
To use gdImageSetStyle, create an array of integers and assign
them the desired series of color values to be repeated.
You can assign the special color value
gdTransparent to indicate that the existing color should
be left unchanged for that particular pixel (allowing a dashed
line to be attractively drawn over an existing image).
Then, to draw a line using the style, use the normal
gdImageLine function with the
special color value gdStyled.
As of version 1.1.1, the style
array is copied when you set the style, so you need not
be concerned with keeping the array around indefinitely.
This should not break existing code that assumes styles
are not copied.
You can also combine styles and brushes to draw the brush
image at intervals instead of in a continuous stroke.
When creating a style for use with a brush, the
style values are interpreted differently: zero (0) indicates
pixels at which the brush should not be drawn, while one (1)
indicates pixels at which the brush should be drawn.
To draw a styled, brushed line, you must use the
special color value
gdStyledBrushed. For an example of this feature
in use, see gddemo.c (provided in the distribution).
gdImagePtr im;
int styleDotted[2], styleDashed[6];
FILE *in;
int black;
int red;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
red = gdImageColorAllocate(im, 255, 0, 0);
/* Set up dotted style. Leave every other pixel alone. */
styleDotted[0] = red;
styleDotted[1] = gdTransparent;
/* Set up dashed style. Three on, three off. */
styleDashed[0] = red;
styleDashed[1] = red;
styleDashed[2] = red;
styleDashed[3] = gdTransparent;
styleDashed[4] = gdTransparent;
styleDashed[5] = gdTransparent;
/* Set dotted style. Note that we have to specify how many pixels are
in the style! */
gdImageSetStyle(im, styleDotted, 2);
/* Draw a line from the upper left corner to the lower right corner. */
gdImageLine(im, 0, 0, 99, 99, gdStyled);
/* Now the dashed line. */
gdImageSetStyle(im, styleDashed, 6);
gdImageLine(im, 0, 99, 0, 99, gdStyled);
/* ... Do something with the image, such as saving it to a file ... */
/* Destroy it */
gdImageDestroy(im);
gdImageBlue is a macro which returns the blue component of
the specified color index. Use this macro rather than accessing the
structure members directly.
gdImageGetPixel() retrieves the color index of a particular
pixel. Always use this function to query pixels;
do not access the pixels of the gdImage structure
directly.
... inside a function ...
FILE *in;
gdImagePtr im;
int c;
in = fopen("mygif.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
c = gdImageGetPixel(im, gdImageSX(im) / 2, gdImageSY(im) / 2);
printf("The value of the center pixel is %d; RGB values are %d,%d,%d\n",
c, im->red[c], im->green[c], im->blue[c]);
gdImageDestroy(im);
gdImageBoundsSafe returns true (1) if the specified point is within the bounds
of the image, false (0) if not. This function is intended primarily for
use by those who wish to add functions to gd. All of the gd drawing
functions already clip safely to the edges of the image.
... inside a function ...
gdImagePtr im;
int black;
int white;
im = gdImageCreate(100, 100);
if (gdImageBoundsSafe(im, 50, 50)) {
printf("50, 50 is within the image bounds\n");
} else {
printf("50, 50 is outside the image bounds\n");
}
gdImageDestroy(im);
gdImageGreen is a macro which returns the green component of
the specified color index. Use this macro rather than accessing the
structure members directly.
gdImageRed is a macro which returns the red component of
the specified color index. Use this macro rather than accessing the
structure members directly.
gdImageChar is used to draw single characters on the image.
(To draw multiple characters, use
gdImageString or
gdImageString16.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts.
The character specified by the fifth
argument is drawn from left to right in the specified
color. (See gdImageCharUp for a way
of drawing vertical text.) Pixels not
set by a particular character retain their previous color.
#include "gd.h"
#include "gdfontl.h"
... 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 character. */
gdImageChar(im, gdFontLarge, 0, 0, 'Q', white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageCharUp is used to draw single characters on the image,
rotated 90 degrees.
(To draw multiple characters, use
gdImageStringUp or
gdImageStringUp16.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts. The character specified by
the fifth argument is drawn
from bottom to top, rotated at a 90-degree angle, in the specified
color. (See gdImageChar for a way
of drawing horizontal text.) Pixels not
set by a particular character retain their previous color.
#include "gd.h"
#include "gdfontl.h"
... 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 character upwards so it rests against the top of the image. */
gdImageCharUp(im, gdFontLarge,
0, gdFontLarge->h, 'Q', white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageString is used to draw multiple characters on the image.
(To draw single characters, use
gdImageChar.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts.
The null-terminated C string specified
by the fifth argument is drawn from left to right in the specified
color. (See gdImageStringUp for a way
of drawing vertical text.) Pixels not
set by a particular character retain their previous color.
#include "gd.h"
#include "gdfontl.h"
#include <string.h>
... inside a function ...
gdImagePtr im;
int black;
int white;
/* String to draw. */
char *s = "Hello.";
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 centered string. */
gdImageString(im, gdFontLarge,
im->w / 2 - (strlen(s) * gdFontLarge->w / 2),
im->h / 2 - gdFontLarge->h / 2,
s, white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageString is used to draw multiple 16-bit characters on the image.
(To draw single characters, use
gdImageChar.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts.
The null-terminated string of characters represented as 16-bit unsigned
short integers specified by the fifth argument is drawn from left to right
in the specified
color. (See gdImageStringUp16 for a way
of drawing vertical text.) Pixels not
set by a particular character retain their previous color.
This function was added in gd1.3 to provide a means of rendering
fonts with more than 256 characters for those who have them. A
more frequently used routine is gdImageString.
gdImageStringUp is used to draw multiple characters on the image,
rotated 90 degrees.
(To draw single characters, use
gdImageCharUp.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts.The null-terminated C string specified
by the fifth argument is drawn from bottom to top (rotated
90 degrees) in the specified color. (See
gdImageString for a way
of drawing horizontal text.) Pixels not
set by a particular character retain their previous color.
#include "gd.h"
#include "gdfontl.h"
#include <string.h>
... inside a function ...
gdImagePtr im;
int black;
int white;
/* String to draw. */
char *s = "Hello.";
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 centered string going upwards. Axes are reversed,
and Y axis is decreasing as the string is drawn. */
gdImageStringUp(im, gdFontLarge,
im->w / 2 - gdFontLarge->h / 2,
im->h / 2 + (strlen(s) * gdFontLarge->w / 2),
s, white);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageString is used to draw multiple 16-bit characters vertically on
the image. (To draw single characters, use
gdImageChar.) The second argument is a
pointer to a font definition structure; five fonts are
provided with gd, gdFontTiny, gdFontSmall, gdFontMediumBold,
gdFontLarge, and gdFontGiant. You must
include the files "gdfontt.h", "gdfonts.h", "gdfontmb.h",
"gdfontl.h" and "gdfontg.h" respectively
and (if you are not using a library-based approach) link with the
corresponding .c files to use the provided fonts.
The null-terminated string of characters represented as 16-bit unsigned
short integers specified by the fifth argument is drawn from bottom to top
in the specified color.
(See gdImageStringUp16 for a way
of drawing horizontal text.) Pixels not
set by a particular character retain their previous color.
This function was added in gd1.3 to provide a means of rendering
fonts with more than 256 characters for those who have them. A
more frequently used routine is gdImageStringUp.
gdImageColorAllocate finds the first available color index in
the image specified, sets its RGB values to those requested
(255 is the maximum for each),
and returns the index of the new color table entry. When
creating a new image, the first time you invoke this function,
you are setting the background color for that image.
In the event that all gdMaxColors colors
(256) have already been allocated, gdImageColorAllocate will
return -1 to indicate failure. (This is not uncommon when
working with existing GIF files that already use 256 colors.)
Note that gdImageColorAllocate
does not check for existing colors that match your request;
see gdImageColorExact
and gdImageColorClosest
for ways to locate existing colors that approximate the
color desired in situations where a new color is not available.
... inside a function ...
gdImagePtr im;
int black;
int red;
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color red. */
red = gdImageColorAllocate(im, 255, 0, 0);
/* Draw a dashed line from the upper left corner to the lower right corner. */
gdImageDashedLine(im, 0, 0, 99, 99, red);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageColorClosest searches the colors which have been
defined thus far in the image specified and returns the
index of the color with RGB values closest to those of the
request. (Closeness is determined by Euclidian distance,
which is used to determine the distance in three-dimensional color
space between colors.)
If no colors have yet been allocated in the image,
gdImageColorClosest returns -1.
This function is most useful as a backup method for choosing
a drawing color when an image already contains
gdMaxColors (256) colors and
no more can be allocated. (This is not uncommon when
working with existing GIF files that already use many colors.)
See gdImageColorExact
for a method of locating exact matches only.
... inside a function ...
gdImagePtr im;
FILE *in;
int red;
/* Let's suppose that photo.gif is a scanned photograph with
many colors. */
in = fopen("photo.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* Try to allocate red directly */
red = gdImageColorAllocate(im, 255, 0, 0);
/* If we fail to allocate red... */
if (red == (-1)) {
/* Find the closest color instead. */
red = gdImageColorClosest(im, 255, 0, 0);
}
/* Draw a dashed line from the upper left corner to the lower right corner */
gdImageDashedLine(im, 0, 0, 99, 99, red);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageColorExact searches the colors which have been
defined thus far in the image specified and returns the
index of the first color with RGB values which exactly
match those of the request. If no allocated color matches the
request precisely, gdImageColorExact returns -1.
See gdImageColorClosest
for a way to find the color closest to the color requested.
... inside a function ...
gdImagePtr im;
int red;
in = fopen("photo.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* The image may already contain red; if it does, we'll save a slot
in the color table by using that color. */
/* Try to allocate red directly */
red = gdImageColorExact(im, 255, 0, 0);
/* If red isn't already present... */
if (red == (-1)) {
/* Second best: try to allocate it directly. */
red = gdImageColorAllocate(im, 255, 0, 0);
/* Out of colors, so find the closest color instead. */
red = gdImageColorClosest(im, 255, 0, 0);
}
/* Draw a dashed line from the upper left corner to the lower right corner */
gdImageDashedLine(im, 0, 0, 99, 99, red);
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageColorsTotal is a macro which returns the number of
colors currently allocated in the image. Use this macro
to obtain this information; do not access the structure
directly.
gdImageColorRed is a macro which returns the red portion
of the specified color in the image. Use this macro
to obtain this information; do not access the structure
directly.
gdImageColorGreen is a macro which returns the green portion
of the specified color in the image. Use this macro
to obtain this information; do not access the structure
directly.
gdImageColorBlue is a macro which returns the green portion
of the specified color in the image. Use this macro
to obtain this information; do not access the structure
directly.
gdImageGetInterlaced is a macro which returns true (1)
if the image is interlaced, false (0) if not.
Use this macro to obtain this information; do not
access the structure directly.
See gdImageInterlace for
a means of interlacing images.
gdImageGetTransparent is a macro which returns the
current transparent color index in the image.
If there is no transparent color, gdImageGetTransparent
returns -1. Use this macro to obtain this information; do not
access the structure directly.
gdImageColorDeallocate marks the specified color as being
available for reuse. It does not attempt to determine whether
the color index is still in use in the image. After a call
to this function, the next call to
gdImageColorAllocate
for the same image will set new RGB values for that
color index, changing the color of any pixels which
have that index as a result. If multiple calls to
gdImageColorDeallocate are made consecutively, the lowest-numbered
index among them will be reused by the next
gdImageColorAllocate call.
... inside a function ...
gdImagePtr im;
int red, blue;
in = fopen("photo.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* Look for red in the color table. */
red = gdImageColorExact(im, 255, 0, 0);
/* If red is present... */
if (red != (-1)) {
/* Deallocate it. */
gdImageColorDeallocate(im, red);
/* Allocate blue, reusing slot in table.
Existing red pixels will change color. */
blue = gdImageColorAllocate(im, 0, 0, 255);
}
/* ... Do something with the image, such as saving it to a file... */
/* Destroy it */
gdImageDestroy(im);
gdImageColorTransparent sets the transparent color index
for the specified image to the specified index. To indicate
that there should be no transparent color, invoke
gdImageColorTransparent with a color index of -1.
The color index used should be an index
allocated by gdImageColorAllocate,
whether explicitly invoked by your code or implicitly
invoked by loading an image.
In order to ensure that your image has a reasonable appearance
when viewed by users who do not have transparent background
capabilities, be sure to give reasonable RGB values to the
color you allocate for use as a transparent color,
even though it will be transparent on systems
that support transparency.
... inside a function ...
gdImagePtr im;
int black;
FILE *in, *out;
in = fopen("photo.gif", "rb");
im = gdImageCreateFromGif(in);
fclose(in);
/* Look for black in the color table and make it transparent. */
black = gdImageColorExact(im, 0, 0, 0);
/* If black is present... */
if (black != (-1)) {
/* Make it transparent */
gdImageColorTransparent(im, black);
}
/* Save the newly-transparent image back to the file */
out = fopen("photo.gif", "wb");
gdImageGif(im, out);
fclose(out);
/* Destroy it */
gdImageDestroy(im);
The dst argument is the destination image to which the
region will be copied. The src argument is the source
image from which the region is copied. The dstX
and dstY arguments specify the point in the destination
image to which the region will be copied. The srcX
and srcY arguments specify the upper left corner
of the region in the source image. The w
and h arguments specify the width and height
of the region.
When you copy a region from one location in an image to another
location in the same image, gdImageCopy will perform as expected
unless the regions overlap, in which case the result is
unpredictable.
Important note on copying between images: since
different images do
not necessarily have the same color tables, pixels are not simply set to the
same color index values to copy them. gdImageCopy will attempt
to find an identical RGB value in the destination image for
each pixel in the copied portion of the source image by
invoking gdImageColorExact. If
such a value is not found, gdImageCopy will attempt to
allocate colors as needed using
gdImageColorAllocate. If both of these methods fail,
gdImageCopy will invoke
gdImageColorClosest to find the color in the destination
image which most closely approximates the color of the
pixel being copied.
... Inside a function ...
gdImagePtr im_in;
gdImagePtr im_out;
int x, y;
FILE *in;
FILE *out;
/* Load a small gif to tile the larger one with */
in = fopen("small.gif", "rb");
im_in = gdImageCreateFromGif(in);
fclose(in);
/* Make the output image four times as large on both axes */
im_out = gdImageCreate(im_in->sx * 4, im_in->sy * 4);
/* Now tile the larger image using the smaller one */
for (y = 0; (y < 4); y++) {
for (x = 0; (x < 4); x++) {
gdImageCopy(im_out, im_in,
x * im_in->sx, y * im_in->sy,
0, 0,
im_in->sx, im_in->sy);
}
}
out = fopen("tiled.gif", "wb");
gdImageGif(im_out, out);
fclose(out);
gdImageDestroy(im_in);
gdImageDestroy(im_out);
The dst argument is the destination image to which the
region will be copied. The src argument is the source
image from which the region is copied. The dstX
and dstY arguments specify the point in the destination
image to which the region will be copied. The srcX
and srcY arguments specify the upper left corner
of the region in the source image. The dstW
and dstH arguments specify the width and height
of the destination region. The srcW
and srcH arguments specify the width and height
of the source region and can differ from the destination size,
allowing a region to be scaled during the copying process.
When you copy a region from one location in an image to another
location in the same image, gdImageCopy will perform as expected
unless the regions overlap, in which case the result is
unpredictable. If this presents a problem, create a scratch image
in which to keep intermediate results.
Important note on copying between images: since images
do not necessarily have the same color tables, pixels are not simply set
to the same color index values to copy them. gdImageCopy will attempt
to find an identical RGB value in the destination image for
each pixel in the copied portion of the source image by
invoking gdImageColorExact. If
such a value is not found, gdImageCopy will attempt to
allocate colors as needed using
gdImageColorAllocate. If both of these methods fail,
gdImageCopy will invoke
gdImageColorClosest to find the color in the destination
image which most closely approximates the color of the
pixel being copied.
... Inside a function ...
gdImagePtr im_in;
gdImagePtr im_out;
int x, y;
FILE *in;
FILE *out;
/* Load a small gif to expand in the larger one */
in = fopen("small.gif", "rb");
im_in = gdImageCreateFromGif(in);
fclose(in);
/* Make the output image four times as large on both axes */
im_out = gdImageCreate(im_in->sx * 4, im_in->sy * 4);
/* Now copy the smaller image, but four times larger */
gdImageCopyResized(im_out, im_in, 0, 0, 0, 0,
im_out->sx, im_out->sy,
im_in->sx, im_in->sy);
out = fopen("large.gif", "wb");
gdImageGif(im_out, out);
fclose(out);
gdImageDestroy(im_in);
gdImageDestroy(im_out);
gdImageInterlace is used to determine whether an image should be stored
in a linear fashion, in which lines will appear on the display from
first to last, or in an interlaced fashion, in which the image
will "fade in" over several passes. By default, images are not
interlaced.
A nonzero value for the interlace argument turns on interlace;
a zero value turns it off. Note that interlace has no effect
on other functions, and has no meaning unless you save the
image in GIF format; the gd and xbm formats do not support
interlace.
When a GIF is loaded with gdImageCreateFromGif
, interlace will be set according to the setting in the GIF file.
Note that many GIF viewers and web browsers do not support
interlace. However, the interlaced GIF should still display; it
will simply appear all at once, just as other images do.
gdImagePtr im;
FILE *out;
/* ... Create or load the image... */
/* Now turn on interlace */
gdImageInterlace(im, 1);
/* And open an output file */
out = fopen("test.gif", "wb");
/* And save the image */
gdImageGif(im, out);
fclose(out);
gdImageDestroy(im);
Used in place of a color when invoking a line-drawing
function such as gdImageLine
or gdImageRectangle.
When gdBrushed is used as the color, the brush
image set with gdImageSetBrush
is drawn in place of each pixel of the line (the brush is
usually larger than one pixel, creating the effect
of a wide paintbrush). See also
gdStyledBrushed for a way
to draw broken lines with a series of distinct copies of an image.
Used in place of a color when invoking a line-drawing
function such as gdImageLine
or gdImageRectangle.
When gdStyled is used as the color, the colors of the pixels are
drawn successively from the style that has been
set with gdImageSetStyle.
If the color of a pixel is equal to
gdTransparent, that pixel
is not altered. (This mechanism is completely unrelated
to the "transparent color" of the image itself; see
gdImageColorTransparent
gdImageColorTransparent for that mechanism.) See also
gdStyledBrushed.
Used in place of a color when invoking a line-drawing
function such as gdImageLine
or gdImageRectangle.
When gdStyledBrushed is used as the color, the brush
image set with gdImageSetBrush
is drawn at each pixel of the line, providing that the
style set with gdImageSetStyle
contains a nonzero value (OR gdTransparent, which
does not equal zero but is supported for consistency)
for the current pixel. (Pixels are drawn successively from the style as the
line is drawn, returning to the beginning when the
available pixels in the style are exhausted.) Note that
this differs from the behavior of gdStyled,
in which the values in the style are used as actual
pixel colors, except for gdTransparent.
Used in place of a normal color in a style to be set with
gdImageSetStyle.
gdTransparent is not the transparent
color index of the image; for that functionality please
see gdImageColorTransparent.
In addition to reading and writing the GIF format and reading the
X Bitmap format, gd has the capability to read and write its
own ".gd" format. This format is not intended for
general purpose use and should never be used to distribute
images. It is not a compressed format. Its purpose is solely to
allow very fast loading of images your program needs often in
order to build other images for output. If you are experiencing
performance problems when loading large, fixed GIF images your
program needs to produce its output images, you may wish
to examine the functions
gdImageCreateFromGd and gdImageGd,
which read and write .gd format images.
The program "giftogd.c" is provided as a simple way of converting
.gif files to .gd format. I emphasize again that you will not
need to use this format unless you have a need for high-speed loading
of a few frequently-used images in your program.