[External] Decoding HDR AVIF image consumes huge amounts of RAM

[benstevens48]

Describe the bug

Windows 11 24H2 added support in WIC for decoding HDR AVIF images, which decode to a 64bpp floating point pixel format. However, the decoding process seems to consume a huge amount of RAM. I tested a 20 mega-pixel HDR AVIF exported from Lightroom (which uses the PQ HDR curve I think) and decoding it (in a C++ component) consumes about 2.7GB of RAM (peak in the Visual Studio debugger). The decoded image itself should only consume about 160MB of RAM, and I would expect 2 times or maybe 3 times this at most to be used during decoding. Also, maybe this is inevitable, but it's quite slow. It's much quicker to take a 64bpp PNG with PQ transfer curve, decode that to WIC without color management then use Diret2D to apply the PQ transfer curve.

Steps to reproduce the bug

See description.

Expected behavior

At most ~500MB of RAM used for decoding a 20MP HDR AVIF image, not 2.7GB.

Screenshots

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NuGet package version

None

Packaging type

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Windows version

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IDE

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Additional context

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