OpenCV获取和设置图像的平均亮度

double get_avg_gray(IplImage *img)
{
IplImage *gray = cvCreateImage(cvGetSize(img),IPL_DEPTH_8U,1);
cvCvtColor(img,gray,CV_RGB2GRAY);
CvScalar scalar = cvAvg(gray);
cvReleaseImage(&gray);
return scalar.val[0];
}

void set_avg_gray(IplImage *img,IplImage *out,double avg_gray)
{
double prev_avg_gray = get_avg_gray(img);
cvConvertScale(img,out,avg_gray/prev_avg_gray);
}