Mat對象遍歷像素值

使用at<Vec3b>結構來獲取Mat中的像素值

例如

 1 #include <iostream>
 2 #include <opencv2/opencv.hpp>
 3 using namespace cv;
 4 using namespace std;
 5 
 6 int main(int args,char** argv)
 7 {
 8     Mat src = imread("E:/OpenCV/bin/Resource/lena.jpg",IMREAD_UNCHANGED);
 9     if (src.empty()) {
10         printf("could not find image");
11         return -1;
12     }
13     namedWindow("input", WINDOW_FULLSCREEN);
14     imshow("input", src);
15     imwrite("D:/test.png", src);
16 
17     //visit each pixel
18     int height = src.rows;       //高度
19     int width = src.cols;        //寬度
20     int ch = src.channels();     //通道數
21     for (int row = 0; row < height; row++) {
22         for (int col = 0; col < width; col++) {
23             if (ch == 3) {
24                 Vec3b pixel = src.at<Vec3b>(row, col);
25                 int blue = pixel[0];
26                 int green = pixel[1];
27                 int red = pixel[2];
28                 src.at<Vec3b>(row, col)[0] = 255 - blue;
29                 src.at<Vec3b>(row, col)[1] = 255 - green;
30                 src.at<Vec3b>(row, col)[2] = 255 - red;
31             }
32 
33             if (ch == 1) {
34                 int pv=src.at<uchar>(row, col);
35                 src.at<uchar>(row, col) = (255 - pv);
36             }
37         }
38     }   
39     imshow("after_mod", src);
40 
41     while (waitKey(50) != 27)
42     {
43 
44     }
45     destroyAllWindows();
46     return 0;
47 }

顯示爲：

對圖片進行反色。 

 

使用指針來獲取Mat中的像素值

將上面代碼at<Vec3b>用指針代替如下

 1 Mat result = Mat::zeros(src.size(), src.type());
 2     for (int row = 0; row < height; row++) {
 3         uchar* cur_row = src.ptr<uchar>(row);
 4         uchar* result_row = result.ptr<uchar>(row);
 5         for (int col = 0; col < width; col++) {
 6             if (ch == 3) {
 7                 int blue = *cur_row++;
 8                 int green = *cur_row++;
 9                 int red = *cur_row++;
10 
11                 *result_row++ = blue;
12                 *result_row++ = green;
13                 *result_row++ = red;
14             }
15             if (ch == 1) {
16                 int pv = *cur_row++;
17                 *result_row++ = pv;
18             }
19         }
20     }
21     imshow("after_mod", result);

可以獲得原圖的一個拷貝