无法在 OpenCV 中获取直方图图像

Unable to get histogram image in OpenCV

本文关键字：获取 直方图 图像 OpenCV      更新时间：2023-10-16

我是OpenCV的新手，正在学习绘制单通道图像的直方图。当我运行程序时，我只得到一条白线。请告诉我这段代码有什么问题。

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;
}

对于单通道（这也来自色调通道），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() );    
}

#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);
}

您在第二行中声明了错误的色调通道范围

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

这是错误的，色调通道范围是 0 到 180。因此，由于色调通道范围是 0 到 180，因此如果您采用更少/或等于 180 个箱（即"histSize"）会很好。

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