cv::Mat.data 总是返回相同的值

Question

I have a red image - just for testing. The RGB Color is (217/18/36).

I perform the following code:

void QuaterImage(Mat& SrcImage, Mat& DestImage, bool Downsample) {
    int newWidth = 0, newHeight = 0;
    int newOrigWidth = 0, newOrigHeight = 0;

    if (SrcImage.cols % 2 > 0) { newOrigWidth = SrcImage.cols - 1; } else { newOrigWidth = SrcImage.cols; }
    if (SrcImage.rows % 2 > 0) { newOrigHeight = SrcImage.rows - 1; } else { newOrigHeight = SrcImage.rows; }

    if (SrcImage.depth() != CV_8U) { return; }

    newHeight = newOrigHeight / 2;
    newWidth = newOrigWidth / 2;

    DestImage = Mat(newWidth, newHeight, SrcImage.type());
    int r = 0, c = 0;
    uchar* DataPtr = SrcImage.ptr<uchar>(0);

    std::cout << std::to_string(*DataPtr) << std::endl;
    return;
}

It always returns "205".

If I change the image to be complettely yellow, it returns the exact same value. How can that be?

Regards, Jan

Answer 1

Ok, sorry, I got it. You could not see it. I was giving the same image for SrcImage and DestImage , so the line DestImage = Mat(newWidth, newHeight, SrcImage.type()); overwrote the image. Before that line, the values are correct.

Sorry for that...