=========================
GraphicsMagick Core C API
=========================

.. _Animate : animate.html
.. _Annotate : annotate.html
.. _Attribute : attribute.html
.. _`ASC CDL` : cdl.html
.. _Blob : blob.html
.. _Channel : channel.html
.. _Color : color.html
.. _Compare : compare.html
.. _Composite : composite.html
.. _Confirm Access : confirm_access.html
.. _Constitute : constitute.html
.. _Decorate : decorate.html
.. _Display : display.html
.. _Draw : draw.html
.. _Effect : effect.html
.. _Enhance : enhance.html
.. _Error : error.html
.. _FX : fx.html
.. _`Hald CLUT` : hclut.html
.. _Image : image.html
.. _List : list.html
.. _Magick : magick.html
.. _Memory : memory.html
.. _Monitor : monitor.html
.. _Montage : montage.html
.. _Operator : operator.html
.. _Paint : paint.html
.. _Pixel Cache : pixel_cache.html
.. _Pixel Iterator : pixel_iterator.html
.. _Profile : profile.html
.. _Quantize : quantize.html
.. _Registry : registry.html
.. _Resize : resize.html
.. _Resource : resource.html
.. _Segment : segment.html
.. _Shear : shear.html
.. _Signature : signature.html
.. _Transform : transform.html
.. _types: types.html

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
  * `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
  * 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
  * 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
  * FX_: Special effects methods
  * `Hald CLUT`_ : Apply Hald CLUT to image
  * Image_: Miscellaneous image methods
  * List_: Manage image lists
  * 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
  * Profile_: Attached profile access
  * Quantize_: Reduce image colors or assign image colors from colormap
  * Registry_: Store and retrieve images in memory by ID
  * 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)
  * Transform_: Chop, coalesce, deconstruct, flatten, flip, flop, mosiac, roll,
    or shave image

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.

Here is a full example of a 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]);
        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);
  }

Now we need 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.

Another example is smile.c. Compile and execute it to display a smiley face on
your X server.

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Copyright |copy| GraphicsMagick Group 2002 - 2009

