Disable AVIF when ImageMagick does not support AVIF transparency

[b1ink0]

Summary

Fixes #2237

Relevant technical choices

This PR adds a helper function to detect whether the installed ImageMagick version is older than 6.9.12-68.

If the ImageMagick version does not fully support AVIF transparency, the AVIF option is disabled and a warning notice is shown on the settings screen.

See #2245 (comment) for why 6.9.12-68 was chosen, and see the discussion in PR #2245 for additional context.

Screenshots

Use of AI Tools

Used Codex to review the code and tests.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.92%. Comparing base (4fdf1e9) to head (d76f49b).

Files with missing lines	Patch %	Lines
plugins/webp-uploads/helper.php	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #2540      +/-   ##
==========================================
+ Coverage   69.64%   69.92%   +0.27%     
==========================================
  Files          90       90              
  Lines        7736     7753      +17     
==========================================
+ Hits         5388     5421      +33     
+ Misses       2348     2332      -16     

Flag	Coverage Δ
multisite	69.92% <90.90%> (+0.27%)	⬆️
single	35.36% <0.00%> (-0.08%)	⬇️

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[westonruter]

The -68 here. Is that compared right? In looking at https://www.php.net/manual/en/function.version-compare.php it seems this would cause the version to be considered less than 6.9.12-dev.

[westonruter]

Well, it seems to work: https://3v4l.org/5NVBB

[b1ink0]

Added tests for different version strings in d76f49b.

[westonruter]

I think this should actually be returning false if webp_uploads_imagick_avif_transparency_supported() is returning false.

This is because the plugin will still default to AVIF otherwise at present, even when it is not fully supported:

performance/plugins/webp-uploads/helper.php

Lines 30 to 38 in 4fdf1e9

	// Check the selected output format.
	$output_format = webp_uploads_mime_type_supported( 'image/avif' ) ? webp_uploads_get_image_output_format() : 'webp';
	$default_transforms = array(
	'image/jpeg' => array( 'image/' . $output_format ),
	'image/webp' => array( 'image/' . $output_format ),
	'image/avif' => array( 'image/avif' ),
	'image/png' => array( 'image/' . $output_format ),
	);

[b1ink0]

If webp_uploads_mime_type_supported() returns false for AVIF when webp_uploads_imagick_avif_transparency_supported() fails, showing a separate settings warning specifically for AVIF transparency support would make the notice logic more complex.

If we are okay with showing the existing generic message that AVIF support is not available, then I think this is fine.

@westonruter you can take over the PR if we want to release today.

[westonruter]

I was thinking of something like "AVIF is supported, but not fully: transparency support is lacking."