无法在OpenCV中获得直方图图像

I am new to OpenCV and learning to draw the histogram of a single channel image. When I run the program, I only get a white line. Please tell me what's wrong with this code.

我是OpenCV的新手，学习绘制单个通道图像的直方图。当我运行程序时，我只得到一条白线。请告诉我这密码有什么问题。

int histSize[1] = {256};
float hranges[2] = {0.0, 255.0};
const float* ranges[1] = {hranges};
int channels[1] = {0};

cv::MatND getHistogram(const cv::Mat &image) {
    cv::MatND hist;

    cv::calcHist(&image,1,channels,cv::Mat(),hist,1,histSize,ranges);

    return hist;
}

cv::Mat getHistogramImage(const cv::Mat &image) {
    cv::MatND hist = getHistogram(image);

    double minVal = 0;
    double maxVal = 0;

    cv::minMaxLoc(hist,&minVal,&maxVal,0,0);

    cv::Mat histImg(histSize[0],histSize[0],CV_8U,cv::Scalar(255));

    int hpt = static_cast<int>(0.9*histSize[0]);

    for(int h=0; h<256; ++h){
        float binVal = hist.at<float>(h);

        int intensity = static_cast<int>(binVal*hpt/maxVal);

        cv::line(histImg,cv::Point(h,histSize[0]),
                         cv::Point(h,histSize[0]-intensity),
                         cv::Scalar::all(0));
    }
    return histImg;
}

3 个解决方案

#1

For single channel (and thats too from hue channel), the following code can be used:

对于单个通道(这也来自于顺化通道)，可以使用以下代码:

{
    Mat input("filepath/image.jpg", 1);
    Mat hsv_input;

cvtColor( input, hsv_input, CV_BGR2HSV );

int h_bins = 5; 
int histSize[] = { h_bins}; 
float h_ranges[] = { 0, 180 };

const float* ranges[] = { h_ranges};
int channels[] = { 0 };

MatND original_hist_input;
calcHist( &hsv_input, 1, channels, Mat(), original_hist_input, 1, histSize, ranges, true, false );
normalize( original_hist_input, original_hist_input, 0, 1, NORM_MINMAX, -1, Mat() );    

}

#2

#include <opencv2/opencv.hpp>
#include <iostream>


    using namespace cv;
   using namespace std;



    class Histogram1D
{


   public:

        int hitsize[1];
        float hrange[2];
        const float *ranges[1];
        int channel[1];


    Histogram1D()
    {
        hitsize[0]=256;
        hrange[0]=0.0;
        hrange[1]=256.0;
        ranges[0]=hrange;
        channel[0]=0;

    }

    MatND gethistogram(Mat &image)
    {
        MatND hist;

        calcHist(&image,1,channel,Mat(),hist,1,hitsize,ranges);
        return hist;
    }
};


int main()


{

        Mat image = imread("1.jpg",0);
        Histogram1D h;
        double minval=0;
    double maxval=0;


    MatND result= h.gethistogram(image);

    for (int i=0;i<256;i++)
    {
        cout << "value" << i << "=" << result.at<float>(i)<< endl;

    }

    minMaxLoc(result,&minval,&maxval,0,0);

    Mat histImg(h.hitsize[0],h.hitsize[0],CV_8U,Scalar(255));

    int hpt=static_cast<int>(0.9*h.hitsize[0]);

        for(int i=0;i<h.hitsize[0];i++)
        {
            float binval=result.at<float>(i);
            int intensity=static_cast<int>(binval*hpt/maxval);

            line(histImg,Point(i,h.hitsize[0]),Point (i,h.hitsize[0]-intensity),Scalar::all(0));


        }

        namedWindow("Histogram");
        imshow("Histogram", histImg);
        waitKey(0);
}

#3

you have declared the wrong range for hue channel in your second line

您在第二行中声明了色调通道的错误范围

float hranges[2] = {0.0, 255.0};

It is wrong, the hue-channel range is 0 to 180. So, as the hue-channel range is 0 to 180 therefore it would be good if you take less/or equal to 180 bins i.e. "histSize".

错误的是，hue-channel的范围是0到180。因此，由于颜色通道的范围是0到180，所以如果你取更小的/或等于180个箱子就好了。“histSize”。

#1