sw_engine: improved blending quality #3617
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enhanced anti-aliasing in image blending by properly applying unpremultiply/premultiply computations during blending operations.
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Pull Request Overview
This PR enhances image blending by applying proper unpremultiply steps before blending and simplifies the rasterClear API.
- Always unpremultiply source pixels before invoking the blender in polygon, scaled, direct, and matted blending paths
- Removed the color parameter from
rasterClear, defaulting to a zero clear value - Optimized
BLEND_PREwith an early exit when alpha is 255
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/renderer/sw_engine/tvgSwRenderer.cpp | Updated calls to rasterClear to match the new signature |
| src/renderer/sw_engine/tvgSwRasterTexmap.h | Added rasterUnpremultiply before blending in polygon loops |
| src/renderer/sw_engine/tvgSwRaster.cpp | Applied rasterUnpremultiply in all blending pipelines |
| src/renderer/sw_engine/tvgSwCommon.h | Removed default clear value from rasterClear and optimized BLEND_PRE |
Comments suppressed due to low confidence (1)
src/renderer/sw_engine/tvgSwRenderer.cpp:669
- Removing the dynamic clear color here changes behavior: previously we cleared to either white or black based on blending state. You should preserve that logic by passing the appropriate color to
rasterClear(or extend the new API) to maintain visual consistency.
rasterClear(cmp, bbox.x(), bbox.y(), bbox.w(), bbox.h());
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enhanced anti-aliasing in image blending by properly applying unpremultiply/premultiply computations during blending operations.