Correct (fast) way to convert `Array2<RGBA8>` into `Array3<u8>`?

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
20/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
rust
Domain
data

Research direction

Start by reproducing the .to_pyarray() failure with an Array2<RGBA8> and inspect the existing ndarray-to-NumPy conversion entry points. Determine whether a zero-copy or one-copy conversion is supported, then document or implement the accepted approach and verify its performance and resulting shape.

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Description

enhancement

Hi thanks for the lib!

Context: I have a color image Array2<RGBA8>, and want to visualize it using rust-numpy lib (a binding to python numpy). However, .to_pyarray() complains, so I should convert it into Array3<u8>.

Question: How can I do that - what is the correct/fast way to do so? IMHO the fastest way should even have no memory copy at all, since RGBA8 is compact 4-byte data. But one memory copy is also acceptable.

I have come up with a very slow method but I hope there are other ways: extract Array2<RGBA8> into four Array<u8> for each of 4 channels, and stack! them together. Its performance seems to be quite slow.

Dominant language
Rust
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