darktable-org / darktable-org/rawspeed

IiqDecoder/PhaseOneDecompressor might be doing something wrong/unsufficient

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Dominant language
C++
Stars
456
Forks
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Description

https://github.com/darktable-org/rawspeed/commit/865c5e4682ef58c28c2aa28c32352ae1d4a08ffd

Not sure about this.
Somehow, the decoded image dump does not change if the predictor is instead properly clampBits()ed.
Although, dcraw would consider this as an error, so it is possible that something larger in the decoding is wrong/missing.

Contributor guide

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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 commit 865c5e4682ef58c28c2aa28c32352ae1d4a08ffd and inspect IiqDecoder/PhaseOneDecompressor, focusing on the predictor and clampBits() behavior. Compare the decoded image dump with dcraw's error handling to determine whether the predictor or a larger decoding step is wrong. Done means the decoding discrepancy is explained and the required correction is supported by reproducible output.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
computer-vision
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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