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<div class="document" id="graphicsmagick-core-c-api">
<h1 class="title">GraphicsMagick Core C API</h1>
<!-- -*- mode: rst -*- -->
<!-- This text is in reStucturedText format, so it may look a bit odd. -->
<!-- See http://docutils.sourceforge.net/rst.html for details. -->
<p>The GraphicsMagick core C library constitutes the implementation of
GraphicsMagick and provides the lowest-level C language programming
interface for GraphicsMagick. The core C API provides many functions
to read, manipulate, write, or display an image. To invoke the
functions, write your program in C (or C++) language while making
calls to the core library functions and link with libGraphicsMagick.a,
libGraphicsMagick.so, or GraphicsMagick.dll depending on your system.</p>
<p>The API is divided into a number of categories. While reading this
documentation, please reference the <a class="reference external" href="types.html">types</a> documentation as required:</p>
<blockquote>
<ul class="simple">
<li><p><a class="reference external" href="animate.html">Animate</a>: Interactively animate an image sequence</p></li>
<li><p><a class="reference external" href="annotate.html">Annotate</a>: Annotate an image with text</p></li>
<li><p><a class="reference external" href="attribute.html">Attribute</a>: Access key, value image attributes</p></li>
<li><p><a class="reference external" href="average.html">Average</a>: Average several images together</p></li>
<li><p><a class="reference external" href="cdl.html">ASC CDL</a> : Apply ASC CDL to image</p></li>
<li><p><a class="reference external" href="blob.html">Blob</a>: Read and write images to memory</p></li>
<li><p><a class="reference external" href="channel.html">Channel</a>: Import and export image channels as well as compute channel depth</p></li>
<li><p><a class="reference external" href="color.html">Color</a>: Methods to deal with image colors</p></li>
<li><p><a class="reference external" href="colormap.html">Colormap</a>: Methods to deal with image colormaps</p></li>
<li><p><a class="reference external" href="compare.html">Compare</a>: Compare images</p></li>
<li><p><a class="reference external" href="composite.html">Composite</a>: Composite images</p></li>
<li><p><a class="reference external" href="confirm_access.html">Confirm Access</a> : Confirm access to files and URLs.</p></li>
<li><p><a class="reference external" href="constitute.html">Constitute</a>: Read, write, import, and export images</p></li>
<li><p><a class="reference external" href="decorate.html">Decorate</a>: Add fancy borders to images</p></li>
<li><p><a class="reference external" href="describe.html">Describe</a>: Describe an image</p></li>
<li><p><a class="reference external" href="display.html">Display</a>: Interactively display and edit an image</p></li>
<li><p><a class="reference external" href="draw.html">Draw</a>: Convenient methods to draw vectors and text</p></li>
<li><p><a class="reference external" href="effect.html">Effect</a>:Threshold (various), blur, despeckle, edge, emboss, enhance,
gaussian blur ...</p></li>
<li><p><a class="reference external" href="enhance.html">Enhance</a>: Contrast, equalize, gamma, level, level channel, modulate, negate,
and normalize</p></li>
<li><p><a class="reference external" href="error.html">Error</a>: Error reporting methods</p></li>
<li><p><a class="reference external" href="export.html">Export</a> : Export image pixels to common representations</p></li>
<li><p><a class="reference external" href="fx.html">FX</a>: Special effects methods</p></li>
<li><p><a class="reference external" href="hclut.html">Hald CLUT</a> : Apply Hald CLUT to image</p></li>
<li><p><a class="reference external" href="image.html">Image</a>: Miscellaneous image methods</p></li>
<li><p><a class="reference external" href="import.html">Import</a> : Import image pixels from common representations</p></li>
<li><p><a class="reference external" href="list.html">List</a>: Manage image lists</p></li>
<li><p><a class="reference external" href="log.html">Log</a>: Event logging support</p></li>
<li><p><a class="reference external" href="magick.html">Magick</a>: Image format support interfaces</p></li>
<li><p><a class="reference external" href="memory.html">Memory</a>: Memory allocation methods</p></li>
<li><p><a class="reference external" href="monitor.html">Monitor</a>: Progress monitor callbacks</p></li>
<li><p><a class="reference external" href="montage.html">Montage</a>: Create a montage of image thumbnails</p></li>
<li><p><a class="reference external" href="operator.html">Operator</a>: Methods to apply mathematic or boolean operators to pixels</p></li>
<li><p><a class="reference external" href="paint.html">Paint</a>: Fill pixel regions</p></li>
<li><p><a class="reference external" href="pixel_cache.html">Pixel Cache</a>: Low-level access to image pixels</p></li>
<li><p><a class="reference external" href="pixel_iterator.html">Pixel Iterator</a>: Pixel iterator design pattern support functions</p></li>
<li><p><a class="reference external" href="plasma.html">Plasma</a>: Plasma fractal image generator</p></li>
<li><p><a class="reference external" href="profile.html">Profile</a>: Attached profile access</p></li>
<li><p><a class="reference external" href="quantize.html">Quantize</a>: Reduce image colors or assign image colors from colormap</p></li>
<li><p><a class="reference external" href="registry.html">Registry</a>: Store and retrieve images in memory by ID</p></li>
<li><p><a class="reference external" href="render.html">Render</a>: Render vector graphics</p></li>
<li><p><a class="reference external" href="resize.html">Resize</a>: Resize an Image</p></li>
<li><p><a class="reference external" href="resource.html">Resource</a>: Set and get resource limits</p></li>
<li><p><a class="reference external" href="segment.html">Segment</a>: Coalese similar image colors</p></li>
<li><p><a class="reference external" href="shear.html">Shear</a>: Rotate image, shear image, or apply a 2D affine transformation</p></li>
<li><p><a class="reference external" href="signature.html">Signature</a>: Compute an image signature (checksum)</p></li>
<li><p><a class="reference external" href="statistics.html">Statistics</a>: Compute image statistics</p></li>
<li><p><a class="reference external" href="texture.html">Texture</a>: Create a tiled texture image or tile an image with a texture.</p></li>
<li><p><a class="reference external" href="transform.html">Transform</a>: Chop, coalesce, deconstruct, flatten, flip, flop, mosiac, roll,
or shave image</p></li>
</ul>
</blockquote>
<p>Here are a few sample programs to get you started.</p>
<p>This example program (convert.c) simply converts from one file name to
another (and will automatically change formats based on file
extension):</p>
<pre class="literal-block">#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <magick/api.h>
int main ( int argc, char **argv )
{
Image
*image = (Image *) NULL;
char
infile[MaxTextExtent],
outfile[MaxTextExtent];
int
arg = 1,
exit_status = 0;
ImageInfo
*imageInfo;
ExceptionInfo
exception;
InitializeMagick(NULL);
imageInfo=CloneImageInfo(0);
GetExceptionInfo(&exception);
if (argc != 3)
{
(void) fprintf ( stderr, "Usage: %s infile outfile\n", argv[0] );
(void) fflush(stderr);
exit_status = 1;
goto program_exit;
}
(void) strncpy(infile, argv[arg], MaxTextExtent-1 );
arg++;
(void) strncpy(outfile, argv[arg], MaxTextExtent-1 );
(void) strcpy(imageInfo->filename, infile);
image = ReadImage(imageInfo, &exception);
if (image == (Image *) NULL)
{
CatchException(&exception);
exit_status = 1;
goto program_exit;
}
(void) strcpy(image->filename, outfile);
if (!WriteImage (imageInfo,image))
{
CatchException(&image->exception);
exit_status = 1;
goto program_exit;
}
program_exit:
if (image != (Image *) NULL)
DestroyImage(image);
if (imageInfo != (ImageInfo *) NULL)
DestroyImageInfo(imageInfo);
DestroyMagick();
return exit_status;
}</pre>
<p>This example program (demo.c) which reads multiple input files
(possibly animation files) specified on the command line, resizes the
image frames to 106x80, and writes the resulting animation to disk:</p>
<pre class="literal-block">#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <magick/api.h>
int main(int argc,char **argv)
{
ExceptionInfo
exception;
Image
*image,
*images,
*resize_image,
*thumbnails;
ImageInfo
*image_info;
int
i;
/*
Initialize the image info structure and read the list of files
provided by the user as a image sequence
*/
InitializeMagick(*argv);
GetExceptionInfo(&exception);
image_info=CloneImageInfo((ImageInfo *) NULL);
images=NewImageList();
for (i=1; i< argc-1; i++)
{
(void) strcpy(image_info->filename,argv[i]);
printf("Reading %s ...", image_info->filename);
image=ReadImage(image_info,&exception);
printf(" %lu frames\n", GetImageListLength(image));
if (exception.severity != UndefinedException)
CatchException(&exception);
if (image)
(void) AppendImageToList(&images,image);
}
if (!images)
{
printf("Failed to read any images!\n");
exit(1);
}
/*
Create a thumbnail image sequence
*/
thumbnails=NewImageList();
while ((image=RemoveFirstImageFromList(&images)) != (Image *) NULL)
{
resize_image=ResizeImage(image,106,80,LanczosFilter,1.0,&exception);
DestroyImage(image);
if (resize_image == (Image *) NULL)
{
CatchException(&exception);
continue;
}
(void) AppendImageToList(&thumbnails,resize_image);
}
/*
Write the thumbnail image sequence to file
*/
if (thumbnails)
{
(void) strcpy(thumbnails->filename,argv[argc-1]);
image_info->adjoin=MagickTrue;
printf("Writing %s ... %lu frames\n", thumbnails->filename,
GetImageListLength(thumbnails));
WriteImage(image_info,thumbnails);
}
/*
Release resources
*/
DestroyImageList(thumbnails);
DestroyImageInfo(image_info);
DestroyExceptionInfo(&exception);
DestroyMagick();
return(0);
}</pre>
<p>To compile on Unix, the command would look something like this:</p>
<pre class="literal-block">gcc -o demo demo.c -O `GraphicsMagick-config --cppflags --ldflags --libs`</pre>
<p>As a usage example, with the input files in1.gif, in2.png, and in3.jpg, create
the animation file out.miff:</p>
<pre class="literal-block">demo in1.gif in2.png in3.jpg out.miff</pre>
<p>The resulting animation may be played on an X11 display using 'gm animate
out.miff'.</p>
<p>The GraphicsMagick-config script reproduces the options which were used to
compile the GraphicsMagick utilities. Using compatible options ensures that
your program will compile and run.</p>
</div>
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