Fix image uploads being random data when canvas read access is blocked #15180
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Fixes mastodon#15178 PR mastodon#11499 introduced a way to deal with all-white canvas, but newer Firefox versions set random data instead. This PR detects whether canvas operations are reliable by comparing the results on a hardcoded 2×2 pixels image, and memoizing the result. This should be both more reliable and faster than the previous check.
Gargron
approved these changes
Nov 18, 2020
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Fixes #15178
PR #11499 introduced a way to deal with all-white canvas, but newer Firefox versions set random data instead.
This PR detects whether canvas operations are reliable by comparing the results on a hardcoded 2×2 pixels image, and memoizing the result.
This should be both more reliable and faster than the previous check.