reducing the effect of smudges and highlight the fingerprint ridges. One way to achieve this is by operating in the frequency domain and apply a Butterworth highpass filter to the image. /* 1. Read, pad and display fingerprint pix */ pixt = pixRead("images/original.png"); pixs = pixAddPadding(pixt); pixWrite("padded.png", pixs, IFF_PNG); pixDestroy(&pixt); /*