Fix legacy 0-255 Bodymovin colours and clamp colour narrowing - #601
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Fix legacy 0-255 Bodymovin colours and clamp colour narrowing#601gindemit wants to merge 1 commit into
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Bodymovin exporters older than 4.1.9 emit colours in the 0-255 range instead of the normalized 0-1 range the Lottie schema mandates. The parser stored those raw values, and Color::toColor() then evaluated uint8_t(255 * r) on them - an out-of-range float->integer conversion, which is undefined behaviour. The two toolchains materialized that UB differently, so the same file rendered different colours per platform: the Android NDK build truncated mod 256 (giving an inverted palette, since v*255 mod 256 == 256-v), while the Apple clang build optimized the narrowing away and let each channel's high byte bleed into the next. Neither matched the intended artwork. Detect the legacy encoding in getValue(model::Color) and normalize it, matching what lottie-web and lottie-android do. Additionally clamp in toColor() so any remaining out-of-range value degrades identically and deterministically on every target instead of diverging by compiler. Verified against the bundled body_movin.json (Bodymovin 4.0.0): the banner now renders RGB(88,214,112) with RGB(255,219,67) lettering, matching lottie-web 5.12.2 exactly; before the fix it was (168,42,144) on Android and (168,127,213) on macOS. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Test file
body_movin.json
Legacy 0-255 Bodymovin colours
Bodymovin exporters older than 4.1.9 emit colour components in the 0-255 range instead of the normalized 0-1 range the schema mandates.
LottieParserImpl::getValue(model::Color&)stored those values raw, andColor::toColor()then narrowed values such as255 * 88.0ftouint8_t. That out-of-range float-to-integer conversion is undefined behaviour and renders differently across toolchains.The bundled
body_movin.jsonsample demonstrates the problem: its banner fill is[88, 214, 112, 255]. Before this fix it renders magenta on Android and purple on Apple platforms instead of the intended green.This change:
1.0;uint8_t, including deterministic handling of NaN and out-of-range values.Verified against
body_movin.json: the banner renders RGB(88, 214, 112) with RGB(255, 219, 67) lettering, matching lottie-web 5.12.2.Gradient stops are not covered by this change because no tested sample combines legacy 0-255 colours with gradients.
The shape-content-budget fix previously included in this draft has been moved into a separate pull request so the two independent changes can be reviewed independently.