Sunday, May 15, 2011

Image processing

After many, many years, my sister and I have convinced my mother that all those decades of old photographs need to be scanned and curated. My sister being a CPA, she has a nice document-feeding scanner. So I ran a few test runs, and it turns out that at 600 pixel full-color resolution, any dust at all inside the scanner leaves vertical stripes on the scanned image that are ... not really monochromatic, but sort of a transparency of a monochromatic stripe.

Naturally, I figure there must be software out there to help me remove those stripes. My best strategy so far is to scan each picture twice, once upside down, so that the stripes will be in different places - then do something to recognize the stripes and eliminate them using the corresponding places on the other image.

So far this is a Hard Problem. Here is a link dump of some of the things I've run across while researching it:
  • The CImg library - and here I thought ImageMagick was all there was!
  • The hdrprep script - a Perl script to manipulate imagesets prior to stitching them together to average out their light levels (HDR = High Dynamic Range, a very neat technique)
  • ALE, which is a tool that works magic on images of such refined scope that I can't even truly understand the explanatory blurb - except that I know what registration is, and it's Good Stuff. This only runs on Linux, as a command-line utility, so it's going to take some actual effort to use it because I'm lazy and my Linux box is downstairs and thus requires ssh to hit.

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