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.
The API is divided into a number of categories. While reading this documentation, please reference the types documentation as required:
Animate: Interactively animate an image sequence
Annotate: Annotate an image with text
Attribute: Access key, value image attributes
Average: Average several images together
ASC CDL : Apply ASC CDL to image
Blob: Read and write images to memory
Channel: Import and export image channels as well as compute channel depth
Color: Methods to deal with image colors
Colormap: Methods to deal with image colormaps
Compare: Compare images
Composite: Composite images
Confirm Access : Confirm access to files and URLs.
Constitute: Read, write, import, and export images
Decorate: Add fancy borders to images
Describe: Describe an image
Display: Interactively display and edit an image
Draw: Convenient methods to draw vectors and text
Effect:Threshold (various), blur, despeckle, edge, emboss, enhance, gaussian blur ...
Enhance: Contrast, equalize, gamma, level, level channel, modulate, negate, and normalize
Error: Error reporting methods
Export : Export image pixels to common representations
FX: Special effects methods
Hald CLUT : Apply Hald CLUT to image
Image: Miscellaneous image methods
Import : Import image pixels from common representations
List: Manage image lists
Log: Event logging support
Magick: Image format support interfaces
Memory: Memory allocation methods
Monitor: Progress monitor callbacks
Montage: Create a montage of image thumbnails
Operator: Methods to apply mathematic or boolean operators to pixels
Paint: Fill pixel regions
Pixel Cache: Low-level access to image pixels
Pixel Iterator: Pixel iterator design pattern support functions
Plasma: Plasma fractal image generator
Profile: Attached profile access
Quantize: Reduce image colors or assign image colors from colormap
Registry: Store and retrieve images in memory by ID
Render: Render vector graphics
Resize: Resize an Image
Resource: Set and get resource limits
Segment: Coalese similar image colors
Shear: Rotate image, shear image, or apply a 2D affine transformation
Signature: Compute an image signature (checksum)
Statistics: Compute image statistics
Texture: Create a tiled texture image or tile an image with a texture.
Transform: Chop, coalesce, deconstruct, flatten, flip, flop, mosiac, roll, or shave image
Here are a few sample programs to get you started.
This example program (convert.c) simply converts from one file name to another (and will automatically change formats based on file extension):
#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;
}
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:
#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);
}
To compile on Unix, the command would look something like this:
gcc -o demo demo.c -O `GraphicsMagick-config --cppflags --ldflags --libs`
As a usage example, with the input files in1.gif, in2.png, and in3.jpg, create the animation file out.miff:
demo in1.gif in2.png in3.jpg out.miff
The resulting animation may be played on an X11 display using 'gm animate out.miff'.
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.
Copyright © GraphicsMagick Group 2002 - 2024