Mastering OpenCV 4 - Third Edition

Reducing the random pepper noise from the sketch image

Most of the tiny cameras in smartphones, Raspberry Pi Camera Modules, and some webcams have significant image noise. This is normally acceptable, but it has a big effect on our 5 x 5 Laplacian edge filter. The edge mask (shown as the sketch mode) will often have thousands of small blobs of black pixels called pepper noise, made of several black pixels next to each other on a white background. We are already using a median filter, which is usually strong enough to remove pepper noise, but in our case it may not be strong enough. Our edge mask is mostly a pure white background (value of 255) with some black edges (value of 0) and the dots of noise (also value of 0). We could use a standard ...