深入理解直方图

#include <opencv2/opencv.hpp> #include<vector>using namespace std;using namespace cv;//绘制直方图void showHistCallback(Mat img){vector<Mat> bgr;split(img, bgr);int numbins = 256;float range[] = { 0, 256 };const float* histRange = { range };Mat b_hist, g_hist, r_hist;calcHist(&bgr[0], 1, 0, Mat(), b_hist, 1, &numbins, &histRange);calcHist(&bgr[1], 1, 0, Mat(), g_hist, 1, &numbins, &histRange);calcHist(&bgr[2], 1, 0, Mat(), r_hist, 1, &numbins, &histRange);int width = 512;int height = 256;Mat histImage(height, width, CV_8UC3, Scalar(20, 20, 20));normalize(b_hist, b_hist, 0, height, NORM_MINMAX);normalize(g_hist, g_hist, 0, height, NORM_MINMAX);normalize(r_hist, r_hist, 0, height, NORM_MINMAX);int binStep = cvRound((float)width / (float)numbins);for (int i = 1; i < numbins; i++){line(histImage, Point(binStep*(i - 1), height - cvRound(b_hist.at<float>(i - 1))),Point(binStep * (i), height - cvRound(b_hist.at<float>(i))), Scalar(255, 0, 0));line(histImage, Point(binStep*(i - 1), height - cvRound(g_hist.at<float>(i - 1))),Point(binStep * (i), height - cvRound(g_hist.at<float>(i))), Scalar(0, 255, 0));line(histImage, Point(binStep*(i - 1), height - cvRound(r_hist.at<float>(i - 1))),Point(binStep * (i), height - cvRound(r_hist.at<float>(i))), Scalar(0, 0, 255));}imshow("histImage", histImage);}//图像色彩均衡化void equalizeCallback(Mat img){Mat equalize;Mat ycrcb;cvtColor(img, ycrcb, COLOR_BGR2YCrCb);vector<Mat> channels;split(ycrcb, channels);//只均衡Y通道equalizeHist(channels[0], channels[0]);merge(channels, ycrcb);cvtColor(ycrcb, equalize, COLOR_YCrCb2BGR);imshow("equlized", equalize);}//LOMO效果void lomoCallBack(Mat img){Mat lomo;const double expeonential_e = exp(1.0);Mat lut(1, 256, CV_8UC1);for (int i = 0; i < 256; i++){float x = (float)i / 256.0;lut.at<uchar>(i) = cvRound(256 * (1 / (1 + pow(expeonential_e, -((x - 0.5) / 0.1)))));}//只对红色通道应用值变换vector<Mat> bgr;split(img, bgr);//LUT(bgr[0], lut, bgr[0]);//LUT(bgr[1], lut, bgr[1]);LUT(bgr[2], lut, bgr[2]);merge(bgr, lomo);//创建昏暗的图像Mat halo(img.rows, img.cols, CV_32FC3, Scalar(0.3, 0.3, 0.3));//创建圆circle(halo, Point(img.cols / 2, img.rows / 2), img.cols / 3, Scalar(1, 1, 1), -1);blur(halo, halo, Size(img.cols / 3, img.cols / 3));//将结果转为浮点型Mat lomof;lomo.convertTo(lomof, CV_32FC3);//将结果和halo相乘multiply(lomof, halo, lomof);//转为8位图像lomof.convertTo(lomo, CV_8UC3);imshow("lomo", lomo);}int main(){Mat src = imread("1.jpg",1);imshow("src", src);showHistCallback(src);equalizeCallback(src);lomoCallBack(src);waitKey(0);return 0;}