typedef struct _IplImage
{int  nSize;         /* sizeof(IplImage) */int  ID;            /* version (=0)*/int  nChannels;     /* Most of OpenCV functions support 1,2,3 or 4 channels */int  alphaChannel;  /* ignored by OpenCV */int  depth;         /* pixel depth in bits: IPL_DEPTH_8U, IPL_DEPTH_8S, IPL_DEPTH_16S,IPL_DEPTH_32S, IPL_DEPTH_32F and IPL_DEPTH_64F are supported */char colorModel[4]; /* ignored by OpenCV */char channelSeq[4]; /* ditto */int  dataOrder;     /* 0 - interleaved color channels, 1 - separate color channels.cvCreateImage can only create interleaved images */int  origin;        /* 0 - top-left origin,1 - bottom-left origin (Windows bitmaps style) */int  align;         /* Alignment of image rows (4 or 8).OpenCV ignores it and uses widthStep instead */int  width;         /* image width in pixels */int  height;        /* image height in pixels */struct _IplROI *roi;/* image ROI. if NULL, the whole image is selected */struct _IplImage *maskROI; /* must be NULL */void  *imageId;     /* ditto */struct _IplTileInfo *tileInfo; /* ditto */int  imageSize;     /* image data size in bytes(==image->height*image->widthStepin case of interleaved data)*/char *imageData;  /* pointer to aligned image data */int  widthStep;   /* size of aligned image row in bytes */int  BorderMode[4]; /* ignored by OpenCV */int  BorderConst[4]; /* ditto */char *imageDataOrigin; /* pointer to very origin of image data(not necessarily aligned) -needed for correct deallocation */
}
IplImage;

#define IPL_DEPTH_1U     1
#define IPL_DEPTH_8U     8
#define IPL_DEPTH_16U   16
#define IPL_DEPTH_32F   32

        cvSetImageROI(pImgROI,cvRect(x,y,w,h)); //cvSetImageROI的功能是基于给定的矩形设置图像的ROI（感兴趣区域）