racket / racket/draw

Determine if source image has alpha channel

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Dominant language
Racket
Stars
19
Forks
24
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No merged PRs in 30d

Description

The procedure (send a-bitmap has-alpha-channel?) led me to believe that it would report whether the loaded image has an alpha channel, but apparently it only says whether the bitmap has been created with an alpha channel or not. I would like to request a feature that determines whether a source image has an alpha channel.

I was told that 'unknown/mask would only produce a mask if the source image had an alpha channel, but that is not the case - 'unknown/mask always produces a mask, it's just the mask will be completely black if there is no alpha.

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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 by reading the implementation or documentation for (send a-bitmap has-alpha-channel?) and the 'unknown/mask behavior described in the issue. Determine how source-image alpha differs from bitmap creation settings, then add coverage for images with and without alpha and verify that the new result distinguishes those cases.

Written by the indexing model from the issue text.

Assessment

Domain
computer-graphics
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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