8. 图像直方图

image.png
image.png

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

using namespace cv;
using namespace std;

int main(int argc, char** argv) {

    Mat src = imread("D:/HUANGHAI_WORK/tools/opencv4/opencv/sources/samples/data/home.jpg");


    namedWindow("input", WINDOW_AUTOSIZE);
    imshow("input", src);
    

    vector<Mat> mv;
    split(src, mv);

    //计算直方图
    int histSize = 256;
    float range[] = { 0,255 };
    const float* histRange = { range };
    Mat b_hist, g_hist, r_hist;
    calcHist(&mv[0], 1, 0, Mat(), b_hist, 1, &histSize, &histRange, true, false);
    calcHist(&mv[1], 1, 0, Mat(), g_hist, 1, &histSize, &histRange, true, false);
    calcHist(&mv[2], 1, 0, Mat(), r_hist, 1, &histSize, &histRange, true, false);

    Mat result = Mat::zeros(Size(600, 400), CV_8UC3);
    int margin = 50;
    int nm = result.rows;
    normalize(b_hist, b_hist, 0, nm,NORM_MINMAX,-1,Mat());
    normalize(g_hist, g_hist, 0, nm, NORM_MINMAX, -1, Mat());
    normalize(r_hist, r_hist, 0, nm, NORM_MINMAX, -1, Mat());
    float step = 500.0 / 256.0;
    for (int i = 0; i < 255; i++)
    {
        float f1 = b_hist.at<float>(i, 0);
        float f2 = b_hist.at<float>(i+1, 0);
        line(result, Point(step*i+50, 50 + nm - b_hist.at<float>(i, 0)),Point(step*i+50+1,50+nm- b_hist.at<float>(i + 1, 0)),Scalar(255,0,0),1,8,0);
        line(result, Point(step*i+50, 50 + nm - g_hist.at<float>(i, 0)), Point(step*i+50 + 1, 50 + nm - g_hist.at<float>(i + 1, 0)), Scalar(0, 255, 0), 1, 8, 0);
        line(result, Point(step*i+50, 50 + nm - r_hist.at<float>(i, 0)), Point(step*i+50 + 1, 50 + nm - r_hist.at<float>(i + 1, 0)), Scalar(0, 0, 255), 1, 8, 0);

    }
    imshow("result", result);


    waitKey(0);
    destroyAllWindows();
    return 0;
}

image.png
image.png

//直方图均衡化
void test2() {
    Mat src = imread("D:/HUANGHAI_WORK/tools/opencv4/opencv/sources/samples/data/home.jpg");


    namedWindow("input", WINDOW_AUTOSIZE);
    imshow("input", src);

    Mat gray, dst;
    cvtColor(src, gray, COLOR_BGR2GRAY);
    imshow("gray", gray);
    equalizeHist(gray, dst);
    imshow("eq", dst);

    //计算直方图
    int histSize = 256;
    float range[] = { 0,255 };
    const float* histRange = { range };
    Mat b_hist, g_hist;
    calcHist(&gray, 1, 0, Mat(), b_hist, 1, &histSize, &histRange, true, false);
    calcHist(&dst, 1, 0, Mat(), g_hist, 1, &histSize, &histRange, true, false);


    Mat result = Mat::zeros(Size(600, 400), CV_8UC3);
    int margin = 50;
    int nm = result.rows;
    normalize(b_hist, b_hist, 0, nm, NORM_MINMAX, -1, Mat());
    normalize(g_hist, g_hist, 0, nm, NORM_MINMAX, -1, Mat());
    float step = 500.0 / 256.0;
    for (int i = 0; i < 255; i++)
    {
        float f1 = b_hist.at<float>(i, 0);
        float f2 = b_hist.at<float>(i + 1, 0);
        line(result, Point(step*i + 50, 50 + nm - b_hist.at<float>(i, 0)), Point(step*i + 50 + 1, 50 + nm - b_hist.at<float>(i + 1, 0)), Scalar(0, 0, 255), 1, 8, 0);
        line(result, Point(step*i + 50, 50 + nm - g_hist.at<float>(i, 0)), Point(step*i + 50 + 1, 50 + nm - g_hist.at<float>(i + 1, 0)), Scalar(0, 255, 255), 1, 8, 0);

    }
    imshow("result", result);
}

image.png
image.png

void test3() {
    Mat src1 = imread("D:/HUANGHAI_WORK/tools/opencv4/opencv/sources/samples/data/aloeL.jpg");
    Mat src2 = imread("D:/HUANGHAI_WORK/tools/opencv4/opencv/sources/samples/data/aloeR.jpg");
    
    //计算直方图
    int histSize[] = {256,256,256};
    float range[] = { 0,255 };
    float c1[] = { 0,255 };
    float c2[] = { 0,255 };
    float c3[] = { 0,255 };
    const float* histRange[] = { c1,c2,c3 };
    int channels[] = { 0,1,2 };
    Mat hist1, hist2;
    calcHist(&src1, 1, channels, Mat(), hist1, 3, histSize, histRange, true, false);
    calcHist(&src2, 1, channels, Mat(), hist2, 3, histSize, histRange, true, false);

    //归一化
    normalize(hist1, hist1, 0, 1.0, NORM_MINMAX, -1, Mat());
    normalize(hist2, hist2, 0, 1.0, NORM_MINMAX, -1, Mat());

    //巴氏距离比较
    double b12 = compareHist(hist1, hist2, HISTCMP_BHATTACHARYYA);
    double b11 = compareHist(hist1, hist1, HISTCMP_BHATTACHARYYA);
    printf("巴氏距离：%.2f,%.2f \n", b12, b11);

    //相关性比较
    double c12 = compareHist(hist1, hist2, HISTCMP_CORREL);
    double c11 = compareHist(hist1, hist1, HISTCMP_CORREL);

    printf("相关性：%.2f,%.2f \n",c12,c11);
}