3.3. IplImage Data Structure

With all of that in hand, it is now easy to discuss the IplImage data structure. In essence this object is a CvMat but with some extra goodies buried in it to make the matrix interpretable as an image. This structure was originally defined as part of Intel's Image Processing Library (IPL).^[19] The exact definition of the IplImage structure is shown in Example 3-10.

^[19] IPL was the predecessor to the more modern Intel Performance Primitives (IPP), discussed in Chapter 1. Many of the OpenCV functions are actually relatively thin wrappers around the corresponding IPL or IPP routines. This is why it is so easy for OpenCV to swap in the high-performance IPP library routines when available.

Example 3-10. IplImage header structure

typedef struct _IplImage {
  int                  nSize;
  int                  ID;
  int                  nChannels;
  int                  alphaChannel;
  int                  depth;
  char                 colorModel[4];
  char                 channelSeq[4];
  int                  dataOrder;
  int                  origin;
  int                  align;
  int                  width;
  int                  height;
  struct _IplROI*      roi;
  struct _IplImage*    maskROI;
  void*                imageId;
  struct _IplTileInfo* tileInfo;
  int                  imageSize;
  char*                imageData;
  int                  widthStep;
  int                  BorderMode[4];
  int                  BorderConst[4];
  char*                imageDataOrigin;
} IplImage;