#include <opencv.hpp>
#include <vector>
using namespace std;
using namespace cv;
void creatAlphaMat(Mat &mat) // 建立一個影象
{
    for (int i = 0; i < mat.rows; i++)
    {
        for (int j = 0; j < mat.cols; j++)
        {
            Vec4b&rgba = mat.at<Vec4b>(i, j);
            rgba[
 
0] = UCHAR_MAX;
            rgba[1] = saturate_cast<uchar>((float(mat.cols - j)) / ((float)mat.cols)*UCHAR_MAX);
            rgba[2] = saturate_cast<uchar>((float(mat.rows - i)) / ((float)mat.rows)*UCHAR_MAX);
            rgba[3] = saturate_cast<uchar>(0.5*(rgba[1] + rgba[2]));
        }
    }
}
 
int main()
{
    //建立帶Alpha通道的 Mat
    Mat mat(480, 640, CV_8UC4);
    creatAlphaMat(mat);
    vector<int>compression_params;
    compression_params.push_back(IMWRITE_PNG_COMPRESSION);
    compression_params.push_back(9);
    try{
        imwrite("透明值圖.png", mat, compression_params);
        imshow(
 
"生成的PNG圖", mat);
        fprintf(stdout, "PNG圖片檔案的資料儲存完畢");
        waitKey(0);
    }
    catch (runtime_error& ex){
        fprintf(stderr, "影象轉換髮生錯誤:%s\n", ex.what());
        return 1;
    }
    return 0;
}

　　執行結果：