OpenCV 3.x with Python By Example - Second Edition

2D convolution

Convolution is a fundamental operation in image processing. We basically apply a mathematical operator to each pixel, and change its value in some way. To apply this mathematical operator, we use another matrix called a kernel. The kernel is usually much smaller in size than the input image. For each pixel in the image, we take the kernel and place it on top so that the center of the kernel coincides with the pixel under consideration. We then multiply each value in the kernel matrix with the corresponding values in the image, and then sum it up. This is the new value that will be applied to this position in the output image.

Here, the kernel is called the image filter and the process of applying this kernel to the given image ...