1 #include <iostream>
 2 #include <opencv2/core/core.hpp>
 3 #include <opencv2/highgui/highgui.hpp>
 4 
 5 using namespace std;
 6 using namespace cv;
 7 
 8 Mat src;
 9 Mat image;
10 string str = "./";
11 
12 /*创建alpha表，整体偏红色，左上角到右下角呈现从完全透明到完全不透明变化趋势*/
13 void createAlphaMat(Mat &mat)
14 {
15     for (int i = 0; i < mat.rows; ++i) {
16         for (int j = 0; j < mat.cols; ++j) {
17             Vec4b& rgba = mat.at<Vec4b>(i, j);
18             rgba[0] = UCHAR_MAX;    //r分量一直最大，所以整体偏红
19             rgba[1] = saturate_cast<uchar>((float(mat.cols - j)) / ((float)mat.cols) * UCHAR_MAX);
20             rgba[2] = saturate_cast<uchar>((float(mat.rows - i)) / ((float)mat.rows) * UCHAR_MAX);
21             rgba[3] = saturate_cast<uchar>(0.5 * (rgba[1] + rgba[2]));
22         }
23     }
24 }
25 
26 int main()
27 {
28 
29     /*采用自己设置的参数来保存图片*/
30     Mat mat(480, 640, CV_8UC4);
31     createAlphaMat(mat);
32     vector<int> compression_params;
33     compression_params.push_back(IMWRITE_PNG_COMPRESSION);
34     compression_params.push_back(9);    //png格式下，默认的参数为3.
35     try {
36         imwrite("alpha.png", mat, compression_params);
37     }
38     catch (runtime_error& ex) {
39         fprintf(stderr, "Exception converting image to PNG format: %s\n", ex.what());
40         return 1;
41         for (int i = 0; i < mat.rows; ++i) {
42             for (int j = 0; j < mat.cols; ++j) {
43                 mat.at<Vec4b>(i, j)[0] = 0;
44                 mat.at<Vec4b>(i, j)[1] = 0;
45                 mat.at<Vec4b>(i, j)[2] = 0;
46             }
47         }
48     }
49     imshow("as", mat);
50     if (waitKey(1) == 27){
51 
52     }
53     fprintf(stdout, "Saved PNG file with alpha data.\n");
54 
55     waitKey(0);
56     return 0;
57 }