提取颜色信息

RGB转为灰度图是为了丢掉图片的颜色信息，而保留亮度信息

#include <opencv2/opencv.hpp>
#include<opencv2/imgproc/imgproc.hpp>
using namespace cv;

// 显示灰度直方图
Mat getHistImg(const MatND& hist)
{
    double maxVal=0;
    double minVal=0;

    //找到直方图中的最大值和最小值
    minMaxLoc(hist,&minVal,&maxVal,0,0);
    int histSize=hist.rows;
    Mat histImg(histSize,histSize,CV_8U,Scalar(255));
    // 设置最大峰值为图像高度的90%
    int hpt=static_cast<int>(0.9*histSize);

    for(int h=0;h<histSize;h++)
    {
        float binVal=hist.at<float>(h);
        int intensity=static_cast<int>(binVal*hpt/maxVal);
        line(histImg,Point(h,histSize),Point(h,histSize-intensity),Scalar::all(0));
    }
    return histImg;
}

// 主函数
int main()
{
    Mat Image=imread("I:\\work\\挑战杯\\颜色直方图原图.jpg");
    imshow("原图", Image);
    cvtColor(Image,Image,CV_BGR2GRAY);

    const int channels[1]={0};
    const int histSize[1]={256};
    float hranges[2]={0,255};
    const float* ranges[1]={hranges};
    MatND hist;
    calcHist(&Image,1,channels,Mat(),hist,1,histSize,ranges);
	hist = getHistImg(hist);
	imshow("颜色直方图", hist);
	waitKey(0);
    return 0;

}