fix(🐛): ImageBitmap alpha and options - #434
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Two snapshot-based suites covering createImageBitmap and copyExternalImageToTexture, with baselines validated against Chrome (yarn test:ref) and the dawn.node client (yarn test:node): - ImageBitmapAlpha.spec.ts: full matrix of premultiplyAlpha x destination premultipliedAlpha x flipY, over both the blob and the ArrayBuffer overload, plus exact-value checks where losslessness is guaranteed. The alpha baselines encode the reference integer conversion math; native platforms pass once straight-alpha support lands (issue #432 / PR #433). - ImageBitmapOptions.spec.ts: crop-rect overload, resizeWidth/Height, imageOrientation, and colorSpaceConversion (Display-P3 fixture generated by Chrome). Native currently ignores these options, so on iOS/Android each case asserts today's identity behavior and flips to the reference snapshot once the option is implemented. setup.ts: the node client polyfills now implement premultiplyAlpha, crop, bilinear resize, flipY orientation, close(), and alpha-aware copyExternalImageToTexture with the same integer math as the native ImageBitmap, so reference results can be generated and cross-checked locally. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…remultipliedAlpha createImageBitmap ignored the premultiplyAlpha option and copyExternalImageToTexture ignored the destination's premultipliedAlpha, so an ImageBitmap always came through premultiplied regardless of what was requested. This diverged from the web API and failed the new ImageBitmapAlpha suite on device. - Track the alpha representation on ImageData (premultiplied flag) and expose it on ImageBitmap. - Add a shared convertAlpha helper that matches the reference client's integer rounding, so native results stay bit-exact with dawn.node. - Parse premultiplyAlpha (from both the (source, options) and crop-rect overloads) and convert the decoded pixels to the requested representation before wrapping them in an ImageBitmap. - Convert to the destination's premultipliedAlpha (default false) in copyExternalImageToTexture, composing with the existing flipY. - Decode straight (non-premultiplied) RGBA on Apple via vImage so premultiplyAlpha "none" preserves the decoded bytes exactly; CGBitmapContext cannot target a non-premultiplied layout. Link Accelerate for vImage. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This was referenced Jul 24, 2026
wcandillon
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fixes #432
Two snapshot-based suites covering createImageBitmap and copyExternalImageToTexture, with baselines validated against Chrome (yarn test:ref) and the dawn.node client (yarn test:node):
setup.ts: the node client polyfills now implement premultiplyAlpha, crop, bilinear resize, flipY orientation, close(), and alpha-aware copyExternalImageToTexture with the same integer math as the native ImageBitmap, so reference results can be generated and cross-checked locally.