linebender / linebender/velato

Alpha should apply to layer as a whole, not every element in layer

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bug good first issue
Dominant language
Rust
Stars
158
Forks
26
Avg merge
22h 56m
Merged PRs (30d)
18

Description

When modifying the with_winit example to render with a non-unity alpha, such as

renderer.render(lottie, frame, Affine::IDENTITY, 0.5)

the result looks like
image
with each component of the tiger having alpha applied to it individually. Instead, the alpha should apply to the rendered image as a whole.

I suspect, but haven't confirmed, that the same issue exists for layers specified by the lottie file.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the with_winit example and the renderer.render call shown in the report, reproducing the non-unity alpha case. Trace how the rendered image and any Lottie layers are composited, then verify that alpha is applied once to the complete rendered image rather than separately to each component.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
computer-graphics
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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