wg_engine: alpha premultiplied bug fix#4070
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Pull request overview
This PR fixes an alpha premultiplication bug in the WebGPU engine by introducing a texture preprocessing stage using compute shaders. The preprocessing handles alpha premultiplication for non-premultiplied textures and channel shuffling for ARGB format textures to convert them to the universal RGBA format.
Key changes:
- Added compute shaders for texture preprocessing (premultiplication and channel shuffling)
- Modified fragment shader to remove redundant alpha premultiplication
- Updated texture handling to track premultiplication and shuffle state
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| tvgWgShaderSrc.h | Added declaration for compute shader source |
| tvgWgShaderSrc.cpp | Implemented three compute shader variants and fixed fragment shader alpha handling |
| tvgWgRenderData.h | Added metadata fields to track texture state |
| tvgWgRenderData.cpp | Updated texture initialization to detect format and premultiplication needs |
| tvgWgPipelines.h | Added compute pipeline declarations and release method |
| tvgWgPipelines.cpp | Implemented compute pipeline initialization and cleanup |
| tvgWgCompositor.h | Added staging texture and preprocessing queue |
| tvgWgCompositor.cpp | Implemented texture preprocessing logic in flush operation |
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Fixes an alpha premultiplication bug in the WebGPU engine by introducing a texture preprocessing stage using compute shaders. The preprocessing handles alpha premultiplication for non-premultiplied textures and channel shuffling for ARGB format textures to convert them to the universal RGBA format. Added compute shaders for texture preprocessing (premultiplication and channel shuffling) Modified fragment shader to remove redundant alpha premultiplication Updated texture handling to track premultiplication and shuffle state #4041
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| WGPURenderPipeline tint_effect{}; | ||
| WGPURenderPipeline tritone_effect{}; | ||
| // compute shaders | ||
| WGPUComputePipeline compute_alpha_premult_shuffle{}; |
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nit: since we have multiple *_shuffle names, is it possible for you to consider a more descriptive suffix for these specific cases (like _bgr / _swizzle) to make the intent a bit clearer at call sites? Totally optional.
wenjieshen
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Thank you for the contribution.
I tested this on Windows, and none of the examples showed any regressions. The Lottie example also runs at the same FPS as the previous version.
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Fixes an alpha premultiplication bug in the WebGPU engine by introducing
a texture preprocessing stage using compute shaders.
The preprocessing handles alpha premultiplication for non-premultiplied textures and
channel shuffling for ARGB format textures to convert them to the universal RGBA format.
Added compute shaders for texture preprocessing (premultiplication and channel shuffling)
Modified fragment shader to remove redundant alpha premultiplication
Updated texture handling to track premultiplication and shuffle state
#4041