opencv我的单通道阈值分割

IplImage* imgSource = cvLoadImage("C:\\Users\\Administrator\\Desktop\\no2.jpg",0);
cvNamedWindow("Image", CV_WINDOW_AUTOSIZE);
cvShowImage("Image", imgSource);

if(imgSource != 0)//imgSource为IplImage*
{
for (int j = 0; j < imgSource->width; ++j)
{
for (int i = 0; i < imgSource->height; ++i)
{
//获取(i, j)处的单道图像像素值
double dPixelVal = cvGetReal2D(imgSource, i, j);
if (dPixelVal>51 && dPixelVal <= 102)
{
//设定(i, j)处的单通道图像像素值
cvSetReal2D(imgSource, i, j, 51);
}
}
}
}
cvSaveImage("C:\\Users\\Administrator\\Desktop\\no2.jpg", imgSource);
cvWaitKey(0);
cvDestroyWindow("Image");
cvReleaseImage(&imgSource);