leinaD_natipaC's profile - activity

Warning: this answer is a blatant copy of an answer from stackoverflow

This is how a simple convert => substract => convertAndScaleBack application would look like:

input:

and

int main() { cv::Mat input = cv::imread("../inputData/Lenna.png", CV_LOAD_IMAGE_GRAYSCALE); cv::Mat input2 = cv::imread("../inputData/Lenna_edges.png", CV_LOAD_IMAGE_GRAYSCALE);

    cv::Mat input1_16S;
    cv::Mat input2_16S;

    input.convertTo(input1_16S, CV_16SC1);
    input2.convertTo(input2_16S, CV_16SC1);

    // compute difference of 16 bit signed images
    cv::Mat diffImage = input1_16S-input2_16S;

    // now you have a 16S image that has some negative values

    // find minimum and maximum values:
    double min, max;
    cv::minMaxLoc(diffImage, &min, &max);
    std::cout << "min pixel value: " << min<< std::endl;

    cv::Mat backConverted;

    // scale the pixel values so that the smalles value is 0 and the largest one is 255
    diffImage.convertTo(backConverted,CV_8UC1, 255.0/(max-min), -min);

    cv::imshow("backConverted", backConverted);        
    cv::waitKey(0);
}

output:

That doesn't actually resolve my problem. I guess you are suggesting that I convert my matrix to signed? How do I change from 8UC1 to 16SC!(for example) and back again? Or can I use imwrite() without converting the mat back to CV_8UC1?

the problem is i won't be able to tell apart -9 from 9 right?

I have two images that I am subtracting from one another quite simply:

Mat foo, a, b;
...//imread onto a and b or somesuch
foo = a - b;

Now, as I understand it, any pixel value that goes into the negatives will end up being zero. If that is so, I'd like to know if there is any way to permit it to go under zero so that I may adjust the image later without loss of information.