Question

I have a question about the Convolve function in OpenCV using GPU acceleration.
The speed of the convolutions are roughly 3.5 faster using GPU

when running:

convolve(src_32F, kernel, cresult, false, cbuffer);

However the image borders are missing (in cresult)

The result is excellent otherwise though (kernel size is 60×60)

thanks

Answer 1

This is the way convolution works.

It calculates the value of every pixel as a weighted average of the surrounding ones. So, if you take into account 30 pixels each side, for all the pixels that are closer to the image border than 30 pixels, convolution is not defined.

In the CPU implementation of filtering functions, those missing pixels are supplemented with bogus values based on a given strategy (copy, mirror, blank, etc).

What you can do is to manually pad your matrix with the desired values in a bigger matrix, filter the big one, and then crop it back. For that you can use the gpu::copyMakeBorder() func.