Fixed setup.py when missing libjpeg

[vfdev-5]

This PR fixes the error when installing torchvision from source on a system without libjpeg (e.g. GH Codespaces)

/workspaces/vision/torchvision/csrc/io/image/cpu/decode_jpeg.cpp:159:10: error: 'JPEG_LIB_VERSION' was not declared in this scope; did you mean 'PSTL_VERSION'?
  159 |   return JPEG_LIB_VERSION;
      |          ^~~~~~~~~~~~~~~~
      |          PSTL_VERSION
error: command '/usr/bin/gcc' failed with exit code 1

[pytorch-bot]

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❌ 13 New Failures, 1 Unrelated Failure

As of commit f5ca062 with merge base 69220e0 ():

NEW FAILURES - The following jobs have failed:

• macos (macos-12) / macos-job (gh)
• macos (macos-m1-12) / macos-job (gh)
• python-source-and-configs / linux-job (gh)
• unittests-macos (3.10, macos-12) / macos-job (gh)
• unittests-macos (3.11, macos-12) / macos-job (gh)
• unittests-macos (3.8, macos-12) / macos-job (gh)
• unittests-macos (3.8, macos-m1-12) / macos-job (gh)
• unittests-macos (3.9, macos-12) / macos-job (gh)
• unittests-windows (3.10, windows.4xlarge, cpu) / windows-job (gh)
• unittests-windows (3.11, windows.4xlarge, cpu) / windows-job (gh)
• unittests-windows (3.8, windows.4xlarge, cpu) / windows-job (gh)
• unittests-windows (3.9, windows.4xlarge, cpu) / windows-job (gh)
• windows (windows.4xlarge, cpu) / windows-job (gh)

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pytorch/vision / wheel-py3_8-cpu-aarch64 (gh)

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[NicolasHug]

Thanks @vfdev-5 , LGTM if green with a few comments. Maybe we should just merge it and completely re-write that part of the readme in another PR. We should remove mentions of accimage and also be clear that jpeg-turbo is preferred now.

[NicolasHug]

I don't think we should say that. It depends on whether the user installed them.

[vfdev-5]

Can you detail what is incorrect here?

[NicolasHug]

We don't know whether those libraries can be found on the standard library locations. If users didn't install them, then they won't be found there.

[vfdev-5]

OK, I think I need to rephrase the sentence I wrote: "libpng and libjpeg are first searched on the standard library locations"

[NicolasHug]

It's good to clarify that libjpeg and libpng are optional, but I don't think we need to remove that sentence:

libpng and libjpeg must be available at compilation time in order to be available.

[vfdev-5]

Sorry, I do not understand what you ask. Libs are optional and this sentence "libpng and libjpeg must be available at compilation time in order to be available." does not make sense (without speaking that it is unclear what it is exactly "in order be available")

[NicolasHug]

I think the sentence means

libjpeg and libpng need to be available at compile time when you build from source.

We don't need to remove it

[github-actions]

Hey @NicolasHug!

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[NicolasHug]

Thanks for the fix @vfdev-5 , I'll submit a PR soon to rework our README a bit, as other parts of it also need an update