像素值读写

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int main() {

Mat m(400, 400, CV_8U, Scalar(0));
for (int col = 0; col < 400; col++)
{
    for (int row = 195; row < 205; row++) {
        cout <<(int)( *(m.data + m.step[0] * row + m.step[1] * col) )<< "==>";
        *(m.data + m.step[0] * row + m.step[1] * col) = 255;
        cout << (int)(*(m.data + m.step[0] * row + m.step[1] * col)) << endl;
    }
}
imshow("test1", m);
cvWaitKey();
return 0;

}

image.png

int main() {

Mat m = imread("C://Users//ely//Desktop//lena.jpg");
int *p_address;
Vec3i color;
for (int col = 20; col < 40; col++)
{
    for (int row = 2; row < 20; row++)
    {
        color[0] = (int)(*(m.data + m.step[0] * row + m.step[1] * col));
        color[0] = (int)(*(m.data + m.step[0] * row + m.step[1] * col+m.elemSize()));
        color[0] = (int)(*(m.data + m.step[0] * row + m.step[1] * col + m.elemSize()*2));
        cout << color[0] << "," << color[1] << "," << color[2] << "==>";
        color[0] = 255;
        color[1] = 0;
        color[2] = 0;
        *(m.data + m.step[0] * row + m.step[1] * col) = color[0];
        *(m.data + m.step[0] * row + m.step[1] * col + m.elemSize()) = color[1];
        *(m.data + m.step[0] * row + m.step[1] * col + m.elemSize() * 2) = color[2];
        cout << (int)(*(m.data + m.step[0] * row + m.step[1] * col)) <<
            (int)*(m.data + m.step[0] * row + m.step[1] * col + 1) <<
            (int)*(m.data + m.step[0] * row + m.step[1] * col + 2) << endl;


    }
}
imshow("canvas", m);
cvWaitKey();
return 0;

}

image.png