Tested the last signature on the open residual: is it positional? A sub-pixel or
resampling difference makes the residual track local gradient. Rule stated first,
r > 0.5. Got +0.109 and +0.307, and the brightness control settles it -- on
developer_logos brightness correlates more strongly (+0.471) than gradient, so the
gradient signal is not distinguishable from 'content is where things happen'. Not
positional.
The brightness correlation pointed somewhere better. Signed residual by capture
brightness, off-edge: 843025 of 857573 pixels on publisher_logo and 812111 of
850869 on developer_logos sit in the 0-15 band with a residual of -0.00. So 98% of
the off-edge area is exact, and the entire 0.82-1.42 RMSE comes from the ~2% of
pixels that are lit.
Within those the sign is inconsistent across bands and across screens -- publisher
+1.68, -1.09, -2.48, +0.45 against developer +2.19, +0.74, -1.57, -0.96 -- so not
a global gain and not a global curve, consistent with a per-level LUT fitted on its
own pixels improving them by only 1.6%.
Three mechanisms now ruled out with evidence: global tone, texture decode,
positional. Still no mechanism, and naming what it is not four times is not
finding what it is.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF
4924182942