page_dewarp

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This fork optimizes the original code through several key changes resulting in approximately a 30x speed-up while retaining comparable output quality:

• Using BFGS over Powell
• Reducing the number of spans used
  • This results in a smaller number of parameters requiring optimization
  • Selecting a few spans in an informed way is usually sufficient to capture the dewarped nature
  • Warping profile (i.e., z-displacement as the x-axis is traversed) should be largely the same for most spans
  • Seven (7) spans are selected:
    • Top two spans
    • Three equidistant middle spans
    • Two bottom spans
  • The seven spans are usually adequate to capture the z-displacement and other potential image deformations (e.g., rotated pages, fisheye effects, etc)
• Decreasing the decimate factor

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Page dewarping and thresholding using a "cubic sheet" model - see full writeup at https://mzucker.github.io/2016/08/15/page-dewarping.html

Requirements:

• scipy
• OpenCV 3.0 or greater
• Image module from PIL or Pillow

Usage:

page_dewarp.py IMAGE1 [IMAGE2 ...]