Find text lines on oriented page

[kolhizin]

Algorithm

1. Calculate total variance across row
2. Find periodic patterns:
   • DCT transform
   • Autocorrelation
   • Distance between local maximas
   • 2d chart: distance between maximas and slack. For each pair calculate ratio at "Best points dst apart +-slack" to other points

DoD

• offsets of lines

[kolhizin]

Tested 3 options:

• FFT -- again, too noisy
• np.correlate(x, x, mode='full') -- good
• L1 distance between shifted variance-vector -- good

Two last approaches produce very similar results. Seem robust.

Tested identifying suspicious local maximas -- works on flat photo, but with disturbances only will lead to decreased coverage. Should solve later.