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Media: Fix GD editor leaking WebP-lossless quality into other output formats #13300

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Media: Fix GD editor leaking WebP-lossless quality into other output formats #13300

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5371dcd
Test: reproduce WebP-lossless quality leaking into other output forma…
irozum Aug 27, 2026
d12896a
Media: Fix GD editor leaking a WebP-lossless quality value into other…
irozum Aug 27, 2026
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6 changes: 4 additions & 2 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 @@ -612,13 +612,15 @@ public function set_quality( $quality = null, $dims = array() ) {
$quality = $this->get_quality();
}

// Use the output mime type if present, matching the fallback parent::set_quality() uses.
$mime_type = ! empty( $this->output_mime_type ) ? $this->output_mime_type : $this->mime_type;

// Handle setting the quality for WebP lossless images, see https://php.watch/versions/8.1/gd-webp-lossless.
try {
if ( 'image/webp' === $this->mime_type && defined( 'IMG_WEBP_LOSSLESS' ) ) {
if ( 'image/webp' === $mime_type && defined( 'IMG_WEBP_LOSSLESS' ) ) {
$webp_info = wp_get_webp_info( $this->file );
if ( ! empty( $webp_info['type'] ) && 'lossless' === $webp_info['type'] ) {
$quality = IMG_WEBP_LOSSLESS;
parent::set_quality( $quality, $dims );
}
}
} catch ( Exception $e ) {
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22 changes: 22 additions & 0 deletions tests/phpunit/tests/image/editorGd.php
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Expand Up @@ -674,4 +674,26 @@ public function test_image_non_existent_extension() {

$this->assertTrue( $loaded );
}

/**
* A lossless WebP source's quality should not leak into other output formats.
*
* @ticket 65977
*
* @requires function imagecreatefromwebp
* @requires function imagejpeg
*/
public function test_set_quality_does_not_leak_webp_lossless_quality_into_other_formats() {
$gd_image_editor = new WP_Image_Editor_GD( DIR_TESTDATA . '/images/webp-lossless.webp' );
$loaded = $gd_image_editor->load();

$this->assertNotWPError( $loaded );

$saved = $gd_image_editor->save( null, 'image/jpeg' );

$this->assertNotWPError( $saved );
$this->assertSame( 82, $gd_image_editor->get_quality(), 'Quality for a JPEG output should use the JPEG default, not the WebP lossless sentinel value.' );

unlink( $saved['path'] );
}
}
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