DeScratch

The DeScratch plugin was designed to remove vertical scratches from films. Also it can be used for removing of horizontal noise lines such as drop-outs from analog VHS captures (after image rotation).

The plugin firstly detects scratches, then removes them. It works with every frame, uses spatial information only from current frame. I adapt it to restoration of my old 8 mm films, may be it will be useful to somebody else.

Scratch detecting Apply some vertical blur to frame copy, for suppression of image thin structure, inclined lines and noise. Search for local extremes of luma in every row, with luma difference criterion. Put these extremes in some map (frame). Optional close vertical gaps in extrems by vertical expanding of extreme points. Test extremes map with length and angle criterions, so select real long scratches only. Scratch removing Scratches may be either partially transparent, smooth (with image details), or opaque (with no details or almost destroyed). In the first case, plugin can subtract smooth (blurred) part of luma scratches variation from original image. Image details are kept. In the second case, plugin replaces scratched pixels by mean luma values from some neighbours pixels (in same row). We have also intermediate case by setting some percent of detail to keep. The plugin have some adaptation of keeped value according to pixels luma difference. In all cases, some nearest neighbours may also partially changed for more smoothed transition.