An HPF is a filter that examines a region of an image and boosts the intensity of certain pixels based on the difference in the intensity of the surrounding pixels.
Take, for example, the following kernel:
[[ 0, -0.25, 0 ],[-0.25, 1, -0.25],[ 0, -0.25, 0 ]]
A kernel is a set of weights that are applied to a region in a source image to generate a single pixel in the destination image. For example, if we call an OpenCV function with a parameter to specify a kernel size or ksize of 7, this implies that 49 (7 x 7) source pixels are considered when generating each destination pixel. We can think of a kernel as a piece of frosted glass moving over the source image and letting a diffused blend of the source's light pass through.
