绘制灰色直方图

//绘制灰度直方图
int main( )
{
Mat src,gray;
src=imread("baboon.jpg");
cvtColor(src,gray,CV_RGB2GRAY);
int bins = 256;
int hist_size[] = {bins};
float range[] = { 0, 256 };
const float* ranges[] = { range};
MatND hist;
int channels[] = {0};

calcHist( &gray, 1, channels, Mat(), // do not use mask
hist, 1, hist_size, ranges,
true, // the histogram is uniform
false );

double max_val;
minMaxLoc(hist, 0, &max_val, 0, 0);
int scale = 2;
int hist_height=256;
Mat hist_img = Mat::zeros(hist_height,bins*scale, CV_8UC3);
for(int i=0;i {
float bin_val = hist.at(i);
int intensity = cvRound(bin_val*hist_height/max_val); //要绘制的高度
rectangle(hist_img,Point(i*scale,hist_height-1),
Point((i+1)*scale - 1, hist_height - intensity),
CV_RGB(255,255,255));
}
imshow( "Source", src );
imshow( "Gray Histogram", hist_img );
waitKey(10000000000);
return 0;
}

实验结果：

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