How does the GaussianBlur -Function in OpenCV works

Question

I wanted to ask where i can find how the GaussianBlur-function in OpenCV is implemented. While looking through the sourcecode i could only find this file but i´m looking for the code where the convolution is done. E.g something like this:

 for x to picture.rows
    for y to picture.cols
       for r to mask.width
         for c to mask.cols 
            do convolution

Does the OpenCV GaussianBlur calculates the Convolution for every Pixel or something like every second Pixel to speed it up?

The implementation contains certain details from the computer vision field, which may not be on-topic for SO. — E_net4, Jun 23 '17 at 23:44

Shyam Vishwakarma · Answer 1 · 2017-06-23T10:56:22.390

Below are few links where the Gaussian Filter has been implemented I hope it helps you.

Sample Code -

int main( int argc, char** argv )
{
    //create 2 empty windows
    namedWindow( "Original Image" , CV_WINDOW_AUTOSIZE );
    namedWindow( "Smoothed Image" , CV_WINDOW_AUTOSIZE );

    // Load an image from file
    Mat src = imread( "MyPic.JPG", CV_LOAD_IMAGE_UNCHANGED );

    //show the loaded image
    imshow( "Original Image", src );

    Mat dst;
    char zBuffer[35];

    for ( int i = 1; i  <  31; i = i + 2 )
    {
        //copy the text to the "zBuffer"
        _snprintf_s(zBuffer, 35,"Kernel Size : %d x %d", i, i);

        //smooth the image using Gaussian kernel in the "src" and save it to "dst"
        GaussianBlur( src, dst, Size( i, i ), 0, 0 );

        //put the text in the "zBuffer" to the "dst" image
        putText( dst, zBuffer, Point( src.cols/4, src.rows/8), CV_FONT_HERSHEY_COMPLEX, 1, Scalar(255, 255, 255), 2 );

        //show the blurred image with the text
        imshow( "Smoothed Image", dst );

        //wait for 2 seconds
        int c = waitKey(2000);

        //if the "esc" key is pressed during the wait, return
        if (c == 27)
        {
            return 0;
        }
    }

    //make the "dst" image, black
    dst = Mat::zeros( src.size(), src.type() );

    //copy the text to the "zBuffer"
    _snprintf_s(zBuffer, 35,"Press Any Key to Exit");

    //put the text in the "zBuffer" to the "dst" image
    putText( dst, zBuffer, Point( src.cols/4,  src.rows / 2), CV_FONT_HERSHEY_COMPLEX, 1, Scalar(255, 255, 255) );

    //show the black image with the text
    imshow( "Smoothed Image", dst );

    //wait for a key press infinitely
    waitKey(0);

    return 0;
}

Links-

Link 1

Link2

While the links might answer the question, please consider copying the relevant contents from them into the answer. — E_net4, Jun 23 '17 at 10:48
This is not the implementation of the Gaussian filter... it's just some code that uses it. — Miki, Jun 23 '17 at 11:29
Thanks for the answer. But my question was what kind of logic is hiding behind this : GaussianBlur( src, dst, Size( i, i ), 0, 0 ); — Drian, Jun 23 '17 at 12:24

How does the GaussianBlur -Function in OpenCV works

1 Answers1