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* Some thoughts on the patternmatcher...
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- textarea_binarization:
  muster-buch page 71: weight gray-value of a pixel with laplace function:
    directly -> gray-values with lots of changes are the peaks (good for text)
    1/1+x    -> gray-values which are constant are the peaks (good for bg)
  consider a threshold for laplace to decide whether to count a pixel at all

- call qsort(samples) in an init routine, not at the end of each reset_data()
