MagickCore Image API for C

The MagickCore API is a low-level interface between the C programming language and the ImageMagick image processing libraries and is recommended for wizard-level programmers only. Unlike the MagickWand C API which uses only a few opaque types and accessors, with MagickCore you almost exlusively access the structure members directly. A description of the MagickCore public methods are found here:

After you write your MagickCore program, compile it like this:

    cc -o core core.c `pkg-config --cflags --libs MagickWand`

Set the PKG_CONFIG_PATH environment variable if ImageMagick is not in your default system path:

    export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig

Here is a example program that utilizes the MagickCore API to get you started, core.c. It reads a GIF image, creates a thumbnail, and writes it to disk in the PNG image format.

    #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <MagickCore/MagickCore.h>

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

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

  ImageInfo
    *image_info;

  if (argc != 3)
    {
      (void) fprintf(stdout,"Usage: %s image thumbnail\n",argv[0]);
      exit(0);
    }
  /*
    Initialize the image info structure and read an image.
  */
  MagickCoreGenesis(*argv,MagickTrue);
  exception=AcquireExceptionInfo();
  image_info=CloneImageInfo((ImageInfo *) NULL);
  (void) strcpy(image_info->filename,argv[1]);
  images=ReadImage(image_info,exception);
  if (exception->severity != UndefinedException)
    CatchException(exception);
  if (images == (Image *) NULL)
    exit(1);
  /*
    Convert the image to a thumbnail.
  */
  thumbnails=NewImageList();
  while ((image=RemoveFirstImageFromList(&images)) != (Image *) NULL)
  {
    resize_image=ResizeImage(image,106,80,LanczosFilter,exception);
    if (resize_image == (Image *) NULL)
      MagickError(exception->severity,exception->reason,exception->description);
    (void) AppendImageToList(&thumbnails,resize_image);
    DestroyImage(image);
  }
  /*
    Write the image thumbnail.
  */
  (void) strcpy(thumbnails->filename,argv[2]);
  WriteImage(image_info,thumbnails,exception);
  /*
    Destroy the image thumbnail and exit.
  */
  thumbnails=DestroyImageList(thumbnails);
  image_info=DestroyImageInfo(image_info);
  exception=DestroyExceptionInfo(exception);
  MagickCoreTerminus();
  return(0);
}

Now lets perform the same contrast enhancement while taking advantage of our dual or quad-core processing system by running the algorithm in parallel utilizing wand views. The sigmoidal-contrast.c module reads an image, applies sigmoidal non-linearity contrast control, and writes the result to disk just like the previous contrast enhancement program, but now it does its work in parallel (assumes ImageMagick is built with OpenMP support).

    #include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <MagickCore/MagickCore.h>

static MagickBooleanType SigmoidalContrast(ImageView *contrast_view,
  const ssize_t y,const int id,void *context)
{
#define QuantumScale  ((MagickRealType) 1.0/(MagickRealType) QuantumRange)
#define SigmoidalContrast(x) \
  (QuantumRange*(1.0/(1+exp(10.0*(0.5-QuantumScale*x)))-0.0066928509)*1.0092503)

  RectangleInfo
    extent;

  register IndexPacket
    *indexes;

  register PixelPacket
    *pixels;

  register ssize_t
    x;

  extent=GetImageViewExtent(contrast_view);
  pixels=GetImageViewAuthenticPixels(contrast_view);
  for (x=0; x < (ssize_t) (extent.width-extent.x); x++)
  {
    SetPixelRed(pixels,RoundToQuantum(SigmoidalContrast(GetPixelRed(pixels)));
    SetPixelGreen(pixels,RoundToQuantum(SigmoidalContrast(GetPixelGreen(pixels)));
    SetPixelBlue(pixels,RoundToQuantum(SigmoidalContrast(GetPixelBlue(pixels)));
    SetPixelOpacity(pixels,RoundToQuantum(SigmoidalContrast(GetPixelOpacity(pixels)));
    pixels++;
  }
  indexes=GetImageViewAuthenticIndexes(contrast_view);
  if (indexes != (IndexPacket *) NULL)
    for (x=0; x < (ssize_t) (extent.width-extent.x); x++)
      SetPixelIndex(indexes+x,RoundToQuantum(SigmoidalContrast(GetPixelIndex(indexes+x))));
  return(MagickTrue);
}

int main(int argc,char **argv)
{
#define ThrowImageException(image) \
{ \
 \
  CatchException(exception); \
  if (contrast_image != (Image *) NULL) \
    contrast_image=DestroyImage(contrast_image); \
  exit(-1); \
}
#define ThrowViewException(view) \
{ \
  char \
    *description; \
 \
  ExceptionType \
    severity; \
 \
  description=GetImageViewException(view,&severity); \
  (void) fprintf(stderr,"%s %s %lu %s\n",GetMagickModule(),description); \
  description=DestroyString(description); \
  exit(-1); \
}

  ExceptionInfo
    *exception;

  Image
    *contrast_image;

  ImageInfo
    *image_info;

  ImageView
    *contrast_view;

  MagickBooleanType
    status;

  if (argc != 3)
    {
      (void) fprintf(stdout,"Usage: %s image sigmoidal-image\n",argv[0]);
      exit(0);
    }
  /*
    Read an image.
  */
  MagickCoreGenesis(*argv,MagickTrue);
  image_info=AcquireImageInfo();
  (void) CopyMagickString(image_info->filename,argv[1],MaxTextExtent);
  exception=AcquireExceptionInfo();
  contrast_image=ReadImage(image_info,exception);
  if (contrast_image == (Image *) NULL)
    ThrowImageException(contrast_image);
  /*
    Sigmoidal non-linearity contrast control.
  */
  contrast_view=NewImageView(contrast_image);
  if (contrast_view == (ImageView *) NULL)
    ThrowImageException(contrast_image);
  status=UpdateImageViewIterator(contrast_view,SigmoidalContrast,(void *) NULL);
  if (status == MagickFalse)
    ThrowImageException(contrast_image);
  contrast_view=DestroyImageView(contrast_view);
  /*
    Write the image then destroy it.
  */
  status=WriteImages(image_info,contrast_image,argv[2],exception);
  if (status == MagickFalse)
    ThrowImageException(contrast_image);
  contrast_image=DestroyImage(contrast_image);
  exception=DestroyExceptionInfo(exception);
  image_info=DestroyImageInfo(image_info);
  MagickCoreTerminus();
  return(0);
}