用Opencv 显示直方图

void ShowHistogram(float ** patchFeature, int patchNum)
{
 IplImage *HistImg = cvCreateImage(cvSize(4000,600),IPL_DEPTH_8U,3);
 cvZero(HistImg);
 int binNum = patchNum*16;
 int bin_w = HistImg->width/binNum;
 int i,j,binnum=0;
 float value;
 

 for(i=0;i<patchNum;i++)
 {
  for(j=0;j<16;j++,binnum++)
  {
  value = patchFeature[i][j]*600;
  CvScalar color = CV_RGB(255,255,255);
  cvRectangle( HistImg, cvPoint(binnum*bin_w,HistImg->height),
            cvPoint((binnum+1)*bin_w,(float)(HistImg->height - value)),
            color, 1, 8, 0 );

  }
 }
 cvSaveImage("apple3.jpg",HistImg);
 cvReleaseImage(&HistImg);

}