OpenCV Integral Test source code

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int main(int, char)
{
    
    Mat img = Mat(10, 10, CV_8UC1);
    randu(img, 0, 10);

    cout << "origin" << endl << img << endl;

    //int x=3, y=4, w=4, h=4;
    int x = 1, y = 1, w = 2, h = 2;

    int sum = 0;
    for (int i = 0; i < w; ++i)
    {
        for (int j = 0; j < h; ++j)
        {
            sum = sum + img.at<unsigned char>((y + j), (x + i));
        }
    }

    printf("for loop : sum = %d \n", sum);


    ///////////////////////////////////////////////////////////////////////

    Mat integralImg;
    integral(img, integralImg, CV_64F);

    cout << endl << "integral" << endl << integralImg << endl;

    double p1 = integralImg.at<double>((y), (x));
    double p2 = integralImg.at<double>((y), (x + w));
    double p3 = integralImg.at<double>((y + h), (x));
    double p4 = integralImg.at<double>((y + h), (x + w));

    printf("\n p1:%lf, p2:%lf, p3:%lf, p4:%lf\n", p1, p2, p3, p4);
    printf("integral : sum = %lf \n", (p1 + p4) - (p2 + p3));

    //////////////////////////////////////////////////////////////////////////
    

}

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result