实现 Sobel 算子

Question

我正在尝试在水平和垂直方向上实现索贝尔运算符。但不知怎的，我得到了相反的输出。我在下面附上了代码。对于水平掩模

char mask [3][3]=  {{-1,-2,-1},{0,0,0},{1,2,1}};

void masking(Mat image){

Mat temImage= image.clone();
for (int i = 1; i < image.rows-1; i++)
{
    for (int j = 1; j < image.cols-1; j++)
    {   
        for(int k=0;k<3;k++)
        {
            int pixel1 = image.at<Vec3b>(i-1,j-1)[k] * -1;
            int pixel2 = image.at<Vec3b>(i,j-1)[k] * -2;
            int pixel3 = image.at<Vec3b>(i+1,j-1)[k] * -1;

            int pixel4 = image.at<Vec3b>(i-1,j)[k] * 0;
            int pixel5 = image.at<Vec3b>(i,j)[k] * 0;
            int pixel6 = image.at<Vec3b>(i+1,j)[k] * 0;

            int pixel7 = image.at<Vec3b>(i-1,j+1)[k] * 1;
            int pixel8 = image.at<Vec3b>(i,j+1)[k] * 2;
            int pixel9 = image.at<Vec3b>(i+1,j+1)[k] * 1;

            int sum = pixel1 + pixel2 + pixel3 + pixel4 + pixel5 + pixel6 + pixel7 + pixel8 + pixel9;
            if(sum < 0)
            {
                sum = 0;
            }

            if(sum > 255)
                sum = 255;

            temImage.at<Vec3b>(i,j)[k] = sum;


        }
    }
}
//printf("conter = %d",counter);
imshow( "Display", temImage );
imwrite("output1.png",temImage);

}

我得到的输出为

垂直遮罩在哪里

char mask [3][3]=  {{-1,0,1},{-2,0,2},{-1,0,1}}; 

void masking(Mat image){

Mat temImage= image.clone();
for (int i = 1; i < image.rows-1; i++)
{
    for (int j = 1; j < image.cols-1; j++)
    {   
        for(int k=0;k<3;k++)
        {
            int pixel1 = image.at<Vec3b>(i-1,j-1)[k] * -1;
            int pixel2 = image.at<Vec3b>(i,j-1)[k] * 0;
            int pixel3 = image.at<Vec3b>(i+1,j-1)[k] * 1;

            int pixel4 = image.at<Vec3b>(i-1,j)[k] * -2;
            int pixel5 = image.at<Vec3b>(i,j)[k] * 0;
            int pixel6 = image.at<Vec3b>(i+1,j)[k] * 2;

            int pixel7 = image.at<Vec3b>(i-1,j+1)[k] * -1;
            int pixel8 = image.at<Vec3b>(i,j+1)[k] * 0;
            int pixel9 = image.at<Vec3b>(i+1,j+1)[k] * 1;

            int sum = pixel1 + pixel2 + pixel3 + pixel4 + pixel5 + pixel6 + pixel7 + pixel8 + pixel9;
            if(sum < 0)
            {
                sum = 0;
            }

            if(sum > 255)
                sum = 255;

            temImage.at<Vec3b>(i,j)[k] = sum;


        }
    }
}
//printf("conter = %d",counter);
imshow( "Display", temImage );
imwrite("output1.png",temImage);

}

我得到的输出为

主要功能附在下面

int main( int argc, char** argv ){
Mat input_image = imread("sobel1.jpg",1);
masking(input_image);
waitKey(0);
return 0;

}

根据指南https://www.tutorialspoint.com/dip/sobel_operator.htm我应该得到反向输出。谁能帮我解决这个问题

原图是

Answer 1

不，教程没有错，它讨论的是蒙版而不是渐变。该教程的弱点在于它没有提到我们正在使用他们所谓的垂直掩模来计算水平梯度。