OpenCV 繪制直方圖

和這一篇《OpenCV 數字圖像直方圖》 http://www.linuxidc.com/Linux/2013-10/91707.htm 內容是一樣的，只是使用Mat格式實現~

繪制灰色直方圖

//繪制灰度直方圖
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<bins;i++)
{
float bin_val = hist.at<float>(i);
int intensity = cvRound(bin_val*hist_height/max_val); //要繪制的高度
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;
}

實驗結果：

更多詳情見請繼續閱讀下一頁的精彩內容： http://www.linuxidc.com/Linux/2013-10/91706p2.htm