[wp-trac] [WordPress Trac] #63773: Palette-based PNG cause failure attempting AVIF/WebP conversion under GD

[WordPress Trac]

#63773: Palette-based PNG cause failure attempting AVIF/WebP conversion under GD
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 Reporter:  adamsilverstein  |       Owner:  (none)
     Type:  defect (bug)     |      Status:  new
 Priority:  normal           |   Milestone:  Awaiting Review
Component:  Media            |     Version:  5.8
 Severity:  normal           |  Resolution:
 Keywords:                   |     Focuses:
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Description changed by adamsilverstein:

Old description:

> When uploading a palette based PNG image and attempting to use core's
> `image_editor_output_format` to output WebP or AVIF images, conversion
> fails with a fatal error when using GD. GD cannot convert palette-based
> PNG to WebP/AVIF formats so to fix the issue, a palette image is first
> converted to truecolor (`imagepalettetotruecolor`). Testing shows the
> fatal is resolved and the resulting images are still significantly
> smaller than their PNG counterparts.
>

> This issue was originally reported in the Performance Lab Modern Images
> plugin - https://github.com/WordPress/performance/issues/1561. The issue
> is fixed by this PR in the plugin:
> https://github.com/WordPress/performance/pull/2024. The purpose of this
> ticket is to bring that fix directly into core, into WP_Image_Editor_GD.
>
> We can start by adding a unit test to demonstrate the issue.

New description:

 When uploading a palette based PNG image and attempting to use core's
 `image_editor_output_format` to output WebP or AVIF images, conversion
 fails with a PHP error when using GD. GD cannot convert palette-based PNG
 to WebP/AVIF formats so to fix the issue, a palette image is first
 converted to truecolor (`imagepalettetotruecolor`). Testing shows the PHP
 error is resolved and the resulting images are still significantly smaller
 than their PNG counterparts.


 This issue was originally reported in the Performance Lab Modern Images
 plugin - https://github.com/WordPress/performance/issues/1561. The issue
 is fixed by this PR in the plugin:
 https://github.com/WordPress/performance/pull/2024. The purpose of this
 ticket is to bring that fix directly into core, into WP_Image_Editor_GD.

 We can start by adding a unit test to demonstrate the issue.

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Ticket URL: <https://core.trac.wordpress.org/ticket/63773#comment:1>
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