OpenCV中获取图像某一像素值

This is a basic example for the OpenCV.

First we must know the structure of IplImage:

• IPL image:

  IplImage
    |-- int  nChannels;     // Number of color channels (1,2,3,4)
    |-- int  depth;         // Pixel depth in bits: 
    |                       //   IPL_DEPTH_8U, IPL_DEPTH_8S, 
    |                       //   IPL_DEPTH_16U,IPL_DEPTH_16S, 
    |                       //   IPL_DEPTH_32S,IPL_DEPTH_32F, 
    |                       //   IPL_DEPTH_64F
    |-- int  width;         // image width in pixels
    |-- int  height;        // image height in pixels
    |-- char* imageData;    // pointer to aligned image data
    |                       // Note that color images are stored in BGR order
    |-- 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  widthStep;     // size of aligned image row in bytes
    |-- int  imageSize;     // image data size in bytes = height*widthStep
    |-- struct _IplROI *roi;// image ROI. when not NULL specifies image
    |                       // region  to be processed.
    |-- char *imageDataOrigin; // pointer to the unaligned origin of image data
    |                          // (needed for correct image deallocation)
    |
    |-- int  align;         // Alignment of image rows: 4 or 8 byte alignment
    |                       // OpenCV ignores this and uses widthStep instead
    |-- char colorModel[4]; // Color model - ignored by OpenCV
  //------------------------------------------------------------------------------

  int  main( int  argc,  char *  argv[])
  { 
  
      IplImage *img=cvLoadImage("c://fruitfs.bmp",1);
      CvScalar s;
      for(int i=0;i<img->height;i++){
          for(int j=0;j<img->width;j++){
          s=cvGet2D(img,i,j); // get the (i,j) pixel value
          printf("B=%f, G=%f, R=%f ",s.val[0],s.val[1],s.val[2]);
          s.val[0]=111;
          s.val[1]=111;
          s.val[2]=111;
          cvSet2D(img,i,j,s);//set the (i,j) pixel value
          }
      }
      cvNamedWindow("Image",1); 
  
      cvShowImage("Image",img);
      cvWaitKey(0); //等待按键 
  
      cvDestroyWindow( "Image" );//销毁窗口
      cvReleaseImage( &img ); //释放图像 
  
      return 0;
  }  
  
   
  
  
   其实还有更好的方法，例如将其封装成类，调用起来更加方便，效率也很高。