ImageMagick - C Application Programming Interface
Description: ImageMagick is a robust collection of tools and libraries to read, write, and manipulate an image in many image formats including popular formats like TIFF, JPEG, PNG, PDF, PhotoCD, and GIF. With ImageMagick you can create images dynamically, making it suitable for Web applications. You can also resize, rotate, sharpen, color reduce, or add special effects to an image or image sequence and save your completed work in the same or differing image format. Image processing operations are available from the command line, as well as through C, C++, Perl, or Java programming interfaces.
Keywords: ImageMagick,PerlMagick,GraphicsMagick,Magick++,Image,Magick,Magic,Pixel,Graphics,Perl,Wand

ImageMagick has a number of functions that allow you to read, manipulate, write, or display an image. These functions are accessible through the various tools or the object-oriented Perl interface, PerlMagick. However, you can also access the functions directly from your program through the Magick Application Programmer Interface. To invoke the functions, write your program in your favorite language while making calls to the Magick image functions and link with `libMagick.a`, `libMagick.so`, or `Magick.dll` depending on your system. The Magick Wand API is a new high level interface to the ImageMagick. The Wand API is recommended over the core API below. Magick Wand Pixel Iterator Pixel Wand Drawing Wand The low level core ImageMagick API, follows. Constitute an Image Composite an Image Image Methods Count the Colors in an Image Dealing with Image Colorspaces Dealing with Image Profiles Reduce the Number of Unique Colors in an Image Segment an Image with Thresholding Fuzzy c-Means Resize an Image Transform an Image Shear or Rotate an Image by an Arbitrary Angle Enhance an Image Add an Effect Add a Special Effect Decorate an Image Set Text Attributes Annotate an Image Paint on an Image Draw on an Image Create an Image Thumbnail Interactively Display and Edit an Image Interactively Animate an Image Sequence Get or Set Image Pixels Working with Image Lists Working with Cache Views The Pixel FIFO Read or Write Binary Large OBjects Read or List ImageMagick Image formats Compute a Message Digest for an Image The Registry Dealing with Errors Memory Allocation Monitor or Limit Resource Consumption Monitor the Progress of an Image Operation Deprecated Methods Here is a sample program to get you started. To find out about all the functions that are available, read the source code. Each function is delineated with a full rows of percent signs with comments describing the parameters required for the function and what it does. For ease in finding a function, they are sorted in alphabetical order. Most of the image functions are found in `image.c` and `effects.c`. Here is a full example of a program, `demo.c`, that reads a GIF image, creates a thumbnail, and writes it to disk in the MIFF image format.
        #include <stdio.h>
        #include <stdlib.h>
        #include <string.h>
        #include <magick/api.h>

        int main(int argc,char **argv)
        {
          ExceptionInfo
            exception;

          Image
            *image,
            *images,
            *resize_image,
            *thumbnails;

          ImageInfo
            *image_info;

          /*
            Initialize the image info structure and read an image.
          */
          InitializeMagick(*argv);
          GetExceptionInfo(&exception);
          image_info=CloneImageInfo((ImageInfo *) NULL);
          (void) strcpy(image_info->filename,"image.gif");
          images=ReadImage(image_info,&exception);
          if (exception.severity != UndefinedException)
            CatchException(&exception);
          if (images == (Image *) NULL)
            exit(1);
          /*
            Turn the images into a thumbnail sequence.
          */
          thumbnails=NewImageList();
          while ((image=RemoveFirstImageFromList(&images)) != (Image *) NULL)
          {
            resize_image=ResizeImage(image,106,80,LanczosFilter,1.0,&exception);
            if (resize_image == (Image *) NULL)
              MagickError(exception.severity,exception.reason,exception.description);
            (void) AppendImageToList(&thumbnails,resize_image);
            DestroyImage(image);
          }
          /*
            Write the image as MIFF and destroy it.
          */
          (void) strcpy(thumbnails->filename,"image.miff");
          WriteImage(image_info,thumbnails);
          DestroyImageList(thumbnails);
          DestroyImageInfo(image_info);
          DestroyExceptionInfo(&exception);
          DestroyMagick();
          return(0);
        }
Now we need to compile. On Unix, the command would look something like this:
        setenv LD_LIBRARY_PATH /usr/local/lib
        gcc `Magick-config --cflags --cppflags` demo.c `Magick-config --ldflags --libs`
Another example is smile.c. Compile and excute it to display a smiley face on your X server. Now lets port the above program to use the Magick Wand API:
        #include <stdio.h>
        #include <stdlib.h>
        #include <string.h>
        #include <wand/magick_wand.h>

        int main(int argc,char **argv)
        {
        #define ThrowWandException(wand) \
        { \
          char \
            *description; \
         \
          ExceptionType \
            severity; \
         \
          description=MagickGetException(wand,&severity); \
          (void) fprintf(stderr,"%s %s %ld %s\n",GetMagickModule(),description); \
          MagickRelinquishMemory(description); \
          exit(-1); \
        }

          MagickBooleanType
            status;

          MagickWand
            *magick_wand;

          /*
            Read an image.
          */
          magick_wand=NewMagickWand();
          status=MagickReadImage(magick_wand,"image.gif");
          if (status == MagickFalse)
            ThrowWandException(magick_wand);
          /*
            Turn the images into a thumbnail sequence.
          */
          MagickResetIterator(magick_wand);
          while (MagickNextImage(magick_wand) != MagickFalse)
            MagickResizeImage(magick_wand,106,80,LanczosFilter,1.0);
          /*
            Write the image as MIFF and destroy it.
          */
          status=MagickWriteImages(magick_wand,"image.miff",True);
          if (status == False)
            ThrowWandException(magick_wand);
          return(0);
        }
To compile, type:
        cc `Wand-config --cflags --cppflags` demo.c `Wand-config --ldflags --libs`
For C++, use:
        c++ `Magick++-config --cxxflags --cppflags` demo.cpp `Magick++-config --ldflags --libs`
"Image manipulation software that works like magick"