f8abb56bc4
The port agent produced a genuine second witness for the pixel-cost claim: it
re-checked GP_TITLE entry 12 in Godot, which shares no code with compose,
swapping only paint_order. 59 530 px ink with the rule, exactly 0 without it.
The strong form -- the screen ceasing to exist, not merely changing a lot --
now has two real renderers behind it on that entry.
Its figures did not match ours, so I counted the same composite every way:
RGB > 0 ours 49 771 Godot 59 530 16 % apart
RGB > 1 ours 48 043 Godot 48 368 0.68 % apart
The entire disagreement lives in pixels whose value is exactly 1. That is a
1-LSB sampling artefact between two samplers, not a different set of inked
pixels. So '>0' is not a portable ink convention between renderers on a
mostly-dark frame and '>1' is; any future cross-renderer ink figure should say
which it used.
Also worth recording: our 49 771 was never a threshold figure. It is exact RGBA
inequality between the two paint orders, which over a black backdrop coincides
with ink>0 -- so it belongs against the port's 59 530, not its 48 368. Matching
it to the 48 368 would have made the two renderers look like they agreed for
the wrong reason.
The without-the-rule column is 0 at every threshold here too, matching Godot:
the strong form is not threshold-sensitive in either renderer.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v
62 lines
3.8 KiB
Plaintext
62 lines
3.8 KiB
Plaintext
# Reconciling two ink counts for GP_TITLE entries 12/15 that were never
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# counting the same pixels.
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#
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# Produced by: cargo run -p sylpheed-formats --example forced_backdrop_ink_thresholds
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# 2026-08-30, SYLPHEED_DISC=/disc, 1280x720, black backdrop.
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#
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# The port agent's Godot second witness for entry 12 (build_12, --pose=rest):
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# >0 59 530 px >1 48 368 px without the rule: 0 at both
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#
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# This crate, same entry, primitives-on (the convention the cost run used):
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# >0 49 771 px >1 48 043 px without the rule: 0 at every threshold
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#
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# CONCLUSION: the >1 counts agree to 0.68 % (325 px). The >0 counts differ by
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# 16 %. So the disagreement lives entirely in pixels whose value is exactly 1 --
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# a 1-LSB artefact of a different sampler, not a different set of inked pixels.
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# >0 is NOT portable between these two renderers on a mostly-dark frame; >1 is.
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#
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# Note also: our reported 49 771 was never an ink THRESHOLD figure. It is exact
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# RGBA inequality between the two paint orders, which over a black backdrop
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# coincides with ink>0 -- so it belongs against the port's 59 530, not its 48 368.
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#
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== GP_TITLE entry 12 — primitives on (what the cost run used) (1280x720)
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threshold | RGB>t with rule | A>t with rule | RGB>t WITHOUT | A>t WITHOUT
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>0 | 49771 | 921600 | 0 | 921600
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>1 | 48043 | 921600 | 0 | 921600
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>2 | 44884 | 921600 | 0 | 921600
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>4 | 41946 | 921600 | 0 | 921600
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>8 | 38409 | 921600 | 0 | 921600
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>16 | 32760 | 921600 | 0 | 921600
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exact-RGBA changed pixels between the two orders: 49771
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== GP_TITLE entry 12 — primitives+focus+animated (1280x720)
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threshold | RGB>t with rule | A>t with rule | RGB>t WITHOUT | A>t WITHOUT
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>0 | 54968 | 921600 | 0 | 921600
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>1 | 52058 | 921600 | 0 | 921600
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>2 | 48171 | 921600 | 0 | 921600
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>4 | 44396 | 921600 | 0 | 921600
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>8 | 40064 | 921600 | 0 | 921600
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>16 | 33791 | 921600 | 0 | 921600
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exact-RGBA changed pixels between the two orders: 54968
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== GP_TITLE entry 15 — primitives on (what the cost run used) (1280x720)
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threshold | RGB>t with rule | A>t with rule | RGB>t WITHOUT | A>t WITHOUT
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>0 | 49771 | 921600 | 0 | 921600
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>1 | 48043 | 921600 | 0 | 921600
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>2 | 44884 | 921600 | 0 | 921600
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>4 | 41946 | 921600 | 0 | 921600
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>8 | 38409 | 921600 | 0 | 921600
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>16 | 32760 | 921600 | 0 | 921600
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exact-RGBA changed pixels between the two orders: 49771
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== GP_TITLE entry 15 — primitives+focus+animated (1280x720)
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threshold | RGB>t with rule | A>t with rule | RGB>t WITHOUT | A>t WITHOUT
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>0 | 54968 | 921600 | 0 | 921600
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>1 | 52058 | 921600 | 0 | 921600
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>2 | 48171 | 921600 | 0 | 921600
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>4 | 44396 | 921600 | 0 | 921600
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>8 | 40064 | 921600 | 0 | 921600
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>16 | 33791 | 921600 | 0 | 921600
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exact-RGBA changed pixels between the two orders: 54968
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