This filter is broken Not sure about its purpose either. As you say it progressively darken the top of the image. So the luma goes from black (at the top) to the luma of the image (at thebottom). It has two defects though:
1) It is broken when you apply it to an image with height > 255 pixels. You will see a repetitive gradient, because of the line
p[x*2] = max(0, BYTE(p[x*2]-subtract));
p[x*2]-subtract can get negative, and p[x*2] won't be zero in that case.
2) It results in a crash if intercept > height of the image. It either should throw an error or use min(height, intercept) instead.
No wonder nobody uses this filter. Please file a bugreport at sf. Admin 20:30, 17 January 2016 (CET)
- Yes, this thing should be retired; MaskTools can do a better job. --Raffriff42 02:06, 18 January 2016 (CET)