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Ensure that GD can convert a palette image to WebP correctly #9368

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Ensure that GD can convert a palette image to WebP correctly #9368

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998f2d8
Tests that GD can convert a pallete image to WebP correctly
adamsilverstein Jul 31, 2025
9f6b775
Fix spelling of palette
adamsilverstein Jul 31, 2025
6e5d64e
Add test image
adamsilverstein Jul 31, 2025
9e3861b
phpcbf
adamsilverstein Jul 31, 2025
73b5cb2
Ensure GD can handle WebP/AVIF output of palette based images.
adamsilverstein Jul 31, 2025
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11 changes: 11 additions & 0 deletions src/wp-includes/class-wp-image-editor-gd.php
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Original file line number Diff line number Diff line change
Expand Up @@ -517,6 +517,17 @@ protected function _save( $image, $filename = null, $mime_type = null ) {
imageinterlace( $image, apply_filters( 'image_save_progressive', false, $mime_type ) );
}

// Ensure GD can handle WebP/AVIF output of palette based images.
if (
in_array( $mime_type, array( 'image/webp', 'image/avif' ), true ) &&
! imageistruecolor( $image )
) {
// Preserve transparence and prepare for conversion.
imagealphablending( $image, false );
imagesavealpha( $image, true );
imagepalettetotruecolor( $image );
}

if ( 'image/gif' === $mime_type ) {
if ( ! $this->make_image( $filename, 'imagegif', array( $image, $filename ) ) ) {
return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
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Binary file added tests/phpunit/data/images/png-tests/dice-palette.png
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35 changes: 35 additions & 0 deletions tests/phpunit/tests/image/editorGd.php
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Original file line number Diff line number Diff line change
Expand Up @@ -670,4 +670,39 @@ public function test_image_non_existent_extension() {

$this->assertTrue( $loaded );
}

/**
* Tests that GD can convert a palette image to WebP.
*
* @ticket 63773
*/
public function test_convert_palette_image_to_webp() {
if ( ! ( imagetypes() & IMG_WEBP ) ) {
$this->markTestSkipped( 'This test requires WEBP support.' );
}

$file = DIR_TESTDATA . '/images/png-tests/dice-palette.png';

// Use the `image_editor_output_format` filter to set the output to WebP.
add_filter(
'image_editor_output_format',
function () {
return array(
'image/png' => 'image/webp',
);
}
);

$gd_image_editor = new WP_Image_Editor_GD( $file );

$gd_image_editor->load();

$save_to_file = tempnam( get_temp_dir(), '' ) . '.webp';

$gd_image_editor->save( $save_to_file );

$this->assertFileExists( $save_to_file );

unlink( $save_to_file );
}
}
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