Complete solution for arbitrary Sobel kernel sizes and angles tl;dr: skip down to section ‘Examples’ To add another solution, expanding on this document (it’s not particularly high quality, but it shows some usable graphics and matrices starting at the bottom of page 2). Goal What we’re trying to do is estimate the local gradient of … Read more
I have played a bit with your input Normalization of lighting + dynamic range normalization helps a bit to obtain much better results but still far away from needed one. I would like to try sharpening of partial derivations to boost the letters from background and treshold out small bumps before integrate back and recolor … Read more
Very nice work on boundary detection. I used to work on similar segmentation problems. Theory: Once you obtained your edge map where e(i,j) indicates the “edge-iness” degree of pixel i,j you would like a segmentation of the image that would respect the edge map as possible. In order to formulate this “respect the edge map” … Read more
This is a big subject. You might find Depixelizing Pixel Art1 by Johannes Kopf & Dani Lischinski useful: it’s readable, recent, includes a summary of previous work, and explains their approach in detail. See also slides covering similar background and video(!). Here are some screenshots from the document of ‘nearest neighbor’ vs. ‘their technique’.