Opencv 卷积矩阵给出不寻常的结果

Question

所以我有一个程序试图将一个简单的 3x3 卷积矩阵应用于图像。

这是正在执行工作的函数：

Mat process(Mat image) {

    int x = 2;
    int y = 2;
    Mat nimage(image); //just a new mat to put the resulting image on

    while (y < image.rows-2) {

        while (x < image.cols-2) {

            nimage.at<uchar>(y,x) = //apply matrix to pixel
            image.at<char>(y-1,x-1)*matrix[0]+
            image.at<char>(y-1,x)*matrix[1]+
            image.at<char>(y-1,x+1)*matrix[2]+
            image.at<char>(y,x-1)*matrix[3]+
            image.at<char>(y,x)*matrix[4]+
            image.at<char>(y,x+1)*matrix[5]+
            image.at<char>(y+1,x-1)*matrix[6]+
            image.at<char>(y+1,x)*matrix[7]+
            image.at<char>(y+1,x+1)*matrix[8];

            //if (total < 0) total = 0;
            //if (total > 255) total = 255;

            //cout << (int)total << ": " << x << "," << y << endl;

            x++;
        }

        x = 0;
        y++;
    }

    cout << "done" << endl;

    return nimage;

}

矩阵看起来像这样

double ar[9] = {-1,0,0,
                0,2,0,
                0,0,0};

用作输入的图像如下所示：

所需的输出（我运行 GIMP中输入图像上的相同矩阵）：

结果是……很奇怪：

我认为这与我在设置新图像 (nimage.at<uchar>(y,x) = ...) 的像素时使用的数据类型有关，因为每当我更改它时，我都会得到不同但仍然不正确的结果。

Answer 1

来自关于 Mat 的复制构造函数的 OpenCV 文档，强调我的：

m – Array that (as a whole or partly) is assigned to the constructed matrix. No data is copied by these constructors. Instead, the header pointing to m data or its sub-array is constructed and associated with it. The reference counter, if any, is incremented. So, when you modify the matrix formed using such a constructor, you also modify the corresponding elements of m. If you want to have an independent copy of the sub-array, use Mat::clone().

所以

Mat nimage(image); //just a new mat to put the resulting image on

实际上并没有创建新矩阵；它创建了一个新的 Mat 对象，但该对象仍然引用同一个矩阵。从那时起 nimage.at(y,x) 就像 image.at(y,x).

要复制图像，请使用

Mat nimage(image.clone()); //just a new mat to put the resulting image on

Opencv 卷积矩阵给出不寻常的结果

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