OpenCv 017---图像直方图

1 前备知识

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2 所用到的主要OpenCv API

skip

3 程序代码

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

using namespace cv;
using namespace std;

const int bins = 256;
Mat src;
const char* winTitle = "input image";
void showHistogram();
void drawHistogram(Mat &image);

int main(int argc, char** argv)
{
    src = imread("G:\\CVworkstudy\\program_wwx\\Research society140\\ZhaiZhigang140\\colormap.png");
    if (src.empty())
    {
        printf("Could not load image..\n");
        return 0;
    }
    namedWindow(winTitle, WINDOW_AUTOSIZE);
    imshow(winTitle, src);
    drawHistogram(src);
    waitKey(0);
    return 0;
}

void drawHistogram(Mat &image)
{
    //定义参数变量
    const int channels[1] = { 0 };
    const int bins[1] = { 256 };
    float hranges[2] = { 0,255 };
    const float* ranges[1] = { hranges };
    int dims = image.channels();
    if (dims == 3)
    {
        vector<Mat> bgr_plane;
        split(src, bgr_plane);
        Mat b_hist;
        Mat g_hist;
        Mat r_hist;
        //计算Blue，Green，Red通道的直方图
        calcHist(&bgr_plane[0], 1, 0, Mat(), b_hist, 1, bins, ranges);
        calcHist(&bgr_plane[1], 1, 0, Mat(), g_hist, 1, bins, ranges);
        calcHist(&bgr_plane[2], 1, 0, Mat(), r_hist, 1, bins, ranges);
        //显示直方图
        int hist_w = 512;
        int hist_h = 400;
        int bin_w = cvRound((double)hist_w / bins[0]);
        Mat histImage = Mat::zeros(hist_h, hist_w, CV_8UC3);
        //归一化直方图数据
        normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
        normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
        normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
        // 绘制直方图曲线
        for (int i = 1; i < bins[0]; i++) {
            line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(b_hist.at<float>(i - 1))),
                Point(bin_w*(i), hist_h - cvRound(b_hist.at<float>(i))), Scalar(255, 0, 0), 2, 8, 0);
            line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(g_hist.at<float>(i - 1))),
                Point(bin_w*(i), hist_h - cvRound(g_hist.at<float>(i))), Scalar(0, 255, 0), 2, 8, 0);
            line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(r_hist.at<float>(i - 1))),
                Point(bin_w*(i), hist_h - cvRound(r_hist.at<float>(i))), Scalar(0, 0, 255), 2, 8, 0);
        }
        // 显示直方图
        namedWindow("Histogram Demo", WINDOW_AUTOSIZE);
        imshow("Histogram Demo", histImage);
    }
    else {
        Mat hist;
        // 计算Blue, Green, Red通道的直方图
        calcHist(&image, 1, 0, Mat(), hist, 1, bins, ranges);
        // 显示直方图
        int hist_w = 512;
        int hist_h = 400;
        int bin_w = cvRound((double)hist_w / bins[0]);
        Mat histImage = Mat::zeros(hist_h, hist_w, CV_8UC3);
        // 归一化直方图数据
        normalize(hist, hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
        // 绘制直方图曲线
        for (int i = 1; i < bins[0]; i++) {
            line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(hist.at<float>(i - 1))),
                Point(bin_w*(i), hist_h - cvRound(hist.at<float>(i))), Scalar(0, 255, 0), 2, 8, 0);
        }
        // 显示直方图
        namedWindow("Histogram Demo", WINDOW_AUTOSIZE);
        imshow("Histogram Demo", histImage);
    }
}

void showHistogram() {
    // 三通道分离
    vector<Mat> bgr_plane;
    split(src, bgr_plane);
    // 定义参数变量
    const int channels[1] = { 0 };
    const int bins[1] = { 256 };
    float hranges[2] = { 0,255 };
    const float* ranges[1] = { hranges };
    Mat b_hist;
    Mat g_hist;
    Mat r_hist;
    // 计算Blue, Green, Red通道的直方图
    calcHist(&bgr_plane[0], 1, 0, Mat(), b_hist, 1, bins, ranges);
    calcHist(&bgr_plane[1], 1, 0, Mat(), g_hist, 1, bins, ranges);
    calcHist(&bgr_plane[2], 1, 0, Mat(), r_hist, 1, bins, ranges);
    // 显示直方图
    int hist_w = 512;
    int hist_h = 400;
    int bin_w = cvRound((double)hist_w / bins[0]);
    Mat histImage = Mat::zeros(hist_h, hist_w, CV_8UC3);
    // 归一化直方图数据
    normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
    normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
    normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
    // 绘制直方图曲线
    for (int i = 1; i < bins[0]; i++) {
        line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(b_hist.at<float>(i - 1))),
            Point(bin_w*(i), hist_h - cvRound(b_hist.at<float>(i))), Scalar(255, 0, 0), 2, 8, 0);
        line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(g_hist.at<float>(i - 1))),
            Point(bin_w*(i), hist_h - cvRound(g_hist.at<float>(i))), Scalar(0, 255, 0), 2, 8, 0);
        line(histImage, Point(bin_w*(i - 1), hist_h - cvRound(r_hist.at<float>(i - 1))),
            Point(bin_w*(i), hist_h - cvRound(r_hist.at<float>(i))), Scalar(0, 0, 255), 2, 8, 0);
    }
    // 显示直方图
    namedWindow("Histogram Demo", WINDOW_AUTOSIZE);
    imshow("Histogram Demo", histImage);
}

4 运行结果

5 扩展及注意事项

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