Regression due to be7259b546e75c0afabcca8f9186fba9156b89ce

[TurboGit]

@andriiryzhkov : It seems that the diff is in the feather part of the drawn path masks. Can you investigate ? Maybe there is nothing broken but I'd like a proper validation before updating the expected output especially since there is big changes and even some visible ones.

So last night there was 6 regressions:

 Errors     6
   - 0004-masks
   - 0073-spot-removal
   - 0074-retouch-clone
   - 0075-retouch-heal
   - 0087-blendif-and-or
   - 0088-blendif-diff-excl

Full log:

Test 0004-masks
      Image mire1.cr2
      Timing cpu 2.58s
      Timing gpu 2.65s
      CPU & GPU version differ by 142 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 2.76747
      Avg dE                   : 0.00003
      Std dE                   : 0.00524
      ----------------------------------
      Pixels below avg + 0 std : 99.99 %
      Pixels below avg + 1 std : 99.99 %
      Pixels below avg + 3 std : 99.99 %
      Pixels below avg + 6 std : 99.99 %
      Pixels below avg + 9 std : 99.99 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 19.35379
      Avg dE                   : 0.01170
      Std dE                   : 0.12738
      ----------------------------------
      Pixels below avg + 0 std : 97.94 %
      Pixels below avg + 1 std : 97.94 %
      Pixels below avg + 3 std : 98.62 %
      Pixels below avg + 6 std : 99.70 %
      Pixels below avg + 9 std : 99.98 %
      ----------------------------------
      Pixels above tolerance   : 0.02 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (57529 pixels changed)

Test 0073-spot-removal
      Image mire1.cr2
      Timing cpu 2.80s
      Timing gpu 3.18s
      CPU & GPU version differ by 156 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 2.19465
      Avg dE                   : 0.00004
      Std dE                   : 0.00585
      ----------------------------------
      Pixels below avg + 0 std : 99.99 %
      Pixels below avg + 1 std : 99.99 %
      Pixels below avg + 3 std : 99.99 %
      Pixels below avg + 6 std : 99.99 %
      Pixels below avg + 9 std : 99.99 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 16.85856
      Avg dE                   : 0.00996
      Std dE                   : 0.10617
      ----------------------------------
      Pixels below avg + 0 std : 98.36 %
      Pixels below avg + 1 std : 98.37 %
      Pixels below avg + 3 std : 98.51 %
      Pixels below avg + 6 std : 99.57 %
      Pixels below avg + 9 std : 99.92 %
      ----------------------------------
      Pixels above tolerance   : 0.01 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (45717 pixels changed)

Test 0074-retouch-clone
      Image mire1.cr2
      Timing cpu 2.76s
      Timing gpu 2.61s
      CPU & GPU version differ by 186 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 2.60948
      Avg dE                   : 0.00004
      Std dE                   : 0.00599
      ----------------------------------
      Pixels below avg + 0 std : 99.99 %
      Pixels below avg + 1 std : 99.99 %
      Pixels below avg + 3 std : 99.99 %
      Pixels below avg + 6 std : 99.99 %
      Pixels below avg + 9 std : 99.99 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 26.30668
      Avg dE                   : 0.01551
      Std dE                   : 0.14221
      ----------------------------------
      Pixels below avg + 0 std : 97.59 %
      Pixels below avg + 1 std : 97.60 %
      Pixels below avg + 3 std : 98.02 %
      Pixels below avg + 6 std : 99.60 %
      Pixels below avg + 9 std : 99.98 %
      ----------------------------------
      Pixels above tolerance   : 0.01 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (67188 pixels changed)

Test 0075-retouch-heal
      Image mire1.cr2
      Timing cpu 6.47s
      Timing gpu 6.32s
      CPU & GPU version differ by 644 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 2.19465
      Avg dE                   : 0.00012
      Std dE                   : 0.00855
      ----------------------------------
      Pixels below avg + 0 std : 99.98 %
      Pixels below avg + 1 std : 99.98 %
      Pixels below avg + 3 std : 99.98 %
      Pixels below avg + 6 std : 99.98 %
      Pixels below avg + 9 std : 99.98 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 18.00226
      Avg dE                   : 0.24041
      Std dE                   : 0.84345
      ----------------------------------
      Pixels below avg + 0 std : 85.30 %
      Pixels below avg + 1 std : 92.94 %
      Pixels below avg + 3 std : 97.63 %
      Pixels below avg + 6 std : 99.39 %
      Pixels below avg + 9 std : 99.83 %
      ----------------------------------
      Pixels above tolerance   : 3.21 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (413519 pixels changed)

Test 0087-blendif-and-or
      Image mire1.cr2
      Timing cpu 2.70s
      Timing gpu 2.74s
      CPU & GPU version differ by 232 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 3.65853
      Avg dE                   : 0.00005
      Std dE                   : 0.00674
      ----------------------------------
      Pixels below avg + 0 std : 99.99 %
      Pixels below avg + 1 std : 99.99 %
      Pixels below avg + 3 std : 99.99 %
      Pixels below avg + 6 std : 99.99 %
      Pixels below avg + 9 std : 99.99 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 5.13905
      Avg dE                   : 0.00554
      Std dE                   : 0.06017
      ----------------------------------
      Pixels below avg + 0 std : 98.89 %
      Pixels below avg + 1 std : 98.90 %
      Pixels below avg + 3 std : 98.93 %
      Pixels below avg + 6 std : 99.28 %
      Pixels below avg + 9 std : 99.67 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (30926 pixels changed)

Test 0088-blendif-diff-excl
      Image mire1.cr2
      Timing cpu 2.67s
      Timing gpu 2.52s
      CPU & GPU version differ by 200 pixels
      CPU vs. GPU report :
      ----------------------------------
      Max dE                   : 9.24185
      Avg dE                   : 0.00005
      Std dE                   : 0.00902
      ----------------------------------
      Pixels below avg + 0 std : 99.99 %
      Pixels below avg + 1 std : 99.99 %
      Pixels below avg + 3 std : 99.99 %
      Pixels below avg + 6 std : 99.99 %
      Pixels below avg + 9 std : 99.99 %
      ----------------------------------
      Pixels above tolerance   : 0.00 %
 
      Expected CPU vs. current CPU report :
      ----------------------------------
      Max dE                   : 47.93922
      Avg dE                   : 0.00983
      Std dE                   : 0.16100
      ----------------------------------
      Pixels below avg + 0 std : 98.09 %
      Pixels below avg + 1 std : 98.12 %
      Pixels below avg + 3 std : 99.38 %
      Pixels below avg + 6 std : 99.92 %
      Pixels below avg + 9 std : 99.97 %
      ----------------------------------
      Pixels above tolerance   : 0.01 %
 
  FAILS: image visually changed
         see diff.png for visual difference
         (53235 pixels changed)

Total test 6
Errors     6
   - 0004-masks
   - 0073-spot-removal
   - 0074-retouch-clone
   - 0075-retouch-heal
   - 0087-blendif-and-or
   - 0088-blendif-diff-excl

As an example take 0075-retouch-heal :

Diff:

Expected:

Output:

We do see that the brown next to the yellow brush is a bit lighter than expected.

[andriiryzhkov]

Fixed regression by applying that change conditionally. Checked all mentioned integration test - they pass "Expected CPU vs. current CPU".

There's a bigger underlying problem with path-mask feathering that I found while working on this. On dense potrace-generated paths (100+ nodes) the border pipeline in path.c produces visible artifacts: phantom near-full circles at some corners (wrong-way arc-fill), criss-crossing shortcut lines during drag (cairo drawing across self-intersection cuts), tiny alternating bumps at every near-collinear corner, and perpendicular stripes when the per-node tangent noise gets amplified by a large feather width.

I am working on the fix for that, but my main worry is that it changes feather rendering a bit and it may not pass this integration test where threshold is very high. But that would be a discussion for the separate PR later.