1、Mat像素的读取：
指针读取像素运行效率高。如果Mat是CV_32F，也只需要将里面的uchar改成float就行了。
//设置灰度图像素for(int i = 0; i < grayFrame.rows; ++i){uchar *p = grayFrame.ptr<uchar>(i);for(int j = 0; j < grayFrame.cols; ++j){p[j] = 255;//白色}}//设置彩色图像素for(int i = 0; i < colorFrame.rows; ++i){Vec3b *p3 = colorFrame.ptr<Vec3b>(i);for(int j = 0; j < colorFrame.cols; ++j){p3[j][0] = 255;//蓝色p3[j][1] = 0;p3[j][2] = 0;}}
2、逐像素比较两幅图像，将不同之处设为红色
#include<opencv2/core/core.hpp>#include<opencv2/highgui/highgui.hpp>#include<iostream>#include <stdlib.h> // c function absusing namespace std;using namespace cv;Point2i compete_pixe1(Mat& src1, Mat& src2, int i, int j) {Vec3b *pixel1 = src1.ptr<Vec3b>(i);Vec3b *pixel2 = src2.ptr<Vec3b>(i);int threshold = 60;Point2i p = Point2i(-1, -1);if (abs(int(pixel1[j][0]) - int(pixel2[j][0])) > threshold && abs(int(pixel1[j][1]) - int(pixel2[j][1])) > threshold && abs(int(pixel1[j][2]) - int(pixel2[j][2])) > threshold){p.x = i;p.y = j;}return p;}int main() {Mat Image1 = imread("1.jpg");Mat Image2 = imread("0.jpg");Mat show_Image = Image1.clone();int rowNumber = show_Image.rows;int colNumber = show_Image.cols;Point2d diff_p;double time0 = static_cast<double>(getTickCount());//逐像素进行比较（RGB）for (int i = 0; i < rowNumber; ++i) {for (int j = 0; j < colNumber; ++j) {diff_p = compete_pixe1(Image1, Image2, i, j);if (diff_p.x != -1 && diff_p.y != -1) {show_Image.ptr<uchar>(i, j)[0] = 0;show_Image.ptr<uchar>(i, j)[1] = 0;show_Image.ptr<uchar>(i, j)[2] = 255;}}}time0 = ((double)getTickCount() - time0) / getTickFrequency();cout << "运行时间为：" << time0 << "秒" << endl;imshow("效果图", show_Image);waitKey(0);return 0;}
