Prevent transparency loss in AVIF by falling back to WebP on older ImageMagick

plugins/webp-uploads/class-webp-uploads-image-editor-imagick.php

@@ -0,0 +1,138 @@
+<?php
+/**
+ * WordPress Image Editor Class for Image Manipulation through Imagick
+ * for transparency detection
+ *
+ * @package webp-uploads
+ *
+ * @since n.e.x.t
+ */
+
+// @codeCoverageIgnoreStart
+if ( ! defined( 'ABSPATH' ) ) {
+	exit; // Exit if accessed directly.
+}
+// @codeCoverageIgnoreEnd
+
+if ( class_exists( 'WebP_Uploads_Image_Editor_Imagick_Base' ) ) {
+
+	/**
+	 * WordPress Image Editor Class for Image Manipulation through Imagick
+	 * for transparency detection.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @see WP_Image_Editor
+	 */
+	class WebP_Uploads_Image_Editor_Imagick extends WebP_Uploads_Image_Editor_Imagick_Base {
+		/**
+		 * The current instance of the image editor.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @var WebP_Uploads_Image_Editor_Imagick|null $current_instance The current instance.
+		 */
+		public static $current_instance = null;
+
+		/**
+		 * Stores already checked images for transparency.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @var array<string, bool> Associative array with file paths as keys and transparency detection results as values.
+		 */
+		private static $checked_images = array();
+
+		/**
+		 * Load the image and set the current instance.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @return WP_Error|true True on success, WP_Error on failure.
+		 */
+		public function load() {
+			// @phpstan-ignore-next-line -- Parent class is created via class_alias at runtime.
+			$result = parent::load();
+			if ( ! is_wp_error( $result ) ) {
+				self::$current_instance = $this;
+			}
+			return $result;
+		}
+
+		/**
+		 * Get the file path of the image.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @return string The file path of the image.
+		 */
+		public function get_file(): string {
+			if ( property_exists( $this, 'file' ) && is_string( $this->file ) ) {
+				return $this->file;
+			}
+			return '';
+		}
+
+		/**
+		 * Looks for transparent pixels in the image.
+		 * If there are none, it returns false.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @return bool|WP_Error True or false based on whether there are transparent pixels, or an error on failure.
+		 */
+		public function has_transparency() {
+			if ( ! property_exists( $this, 'image' ) ) {
+				return false;
+			}
+
+			if ( ! (bool) $this->image ) {
+				return new WP_Error( 'image_editor_has_transparency_error_no_image', __( 'Transparency detection no image found.', 'webp-uploads' ) );
+			}
+
+			$file_path = $this->get_file();
+			if ( isset( self::$checked_images[ $file_path ] ) ) {
+				return self::$checked_images[ $file_path ];
+			}
+
+			if ( ! $this->image instanceof Imagick ) {
+				return false;
+			}
+
+			try {
+				/*
+				* Check if the image has an alpha channel if false, then it can't have transparency so return early.
+				*
+				* Note that Imagick::getImageAlphaChannel() is only available if Imagick
+				* has been compiled against ImageMagick version 6.4.0 or newer.
+				*/
+				if ( is_callable( array( $this->image, 'getImageAlphaChannel' ) ) ) {
+					if ( Imagick::ALPHACHANNEL_UNDEFINED === $this->image->getImageAlphaChannel() ) {
+						self::$checked_images[ $file_path ] = false;
+						return false;
+					}
+				}
+
+				// Walk through the pixels and look transparent pixels.
+				$w = $this->image->getImageWidth();
+				$h = $this->image->getImageHeight();
+				for ( $x = 0; $x < $w; $x++ ) {
+					for ( $y = 0; $y < $h; $y++ ) {
+						$pixel = $this->image->getImagePixelColor( $x, $y );
+						$color = $pixel->getColor( 2 );
+						if ( $color['a'] > 0 && $color['a'] < 255 ) {
+							self::$checked_images[ $file_path ] = true;
+							return true;
+						}
+					}
+				}
+				self::$checked_images[ $file_path ] = false;
+				return false;
+
+			} catch ( Exception $e ) {
+				/* translators: %s is the error message */
+				return new WP_Error( 'image_editor_has_transparency_error', sprintf( __( 'Transparency detection failed: %s', 'webp-uploads' ), $e->getMessage() ) );
+			}
+		}
+	}
+}

plugins/webp-uploads/helper.php

@@ -21,12 +21,18 @@
  * @since 2.0.0 Added support for AVIF.
  * @since 2.2.0 Added support for PNG.
  *
+ * @param string|null $filename Optional. The filename. Default null.
  * @return array<string, array<string>> An array of valid mime types, where the key is the mime type and the value is the extension type.
  */
-function webp_uploads_get_upload_image_mime_transforms(): array {
+function webp_uploads_get_upload_image_mime_transforms( ?string $filename = null ): array {
+	$avif_support = webp_uploads_mime_type_supported( 'image/avif' );
+
+	if ( $avif_support && webp_uploads_check_image_transparency( $filename ) ) {
+		$avif_support = false;
+	}
 
 	// Check the selected output format.
-	$output_format = webp_uploads_mime_type_supported( 'image/avif' ) ? webp_uploads_get_image_output_format() : 'webp';
+	$output_format = $avif_support ? webp_uploads_get_image_output_format() : 'webp';
 
 	$default_transforms = array(
 		'image/jpeg' => array( 'image/' . $output_format ),
@@ -512,3 +518,71 @@ function webp_uploads_get_attachment_file_mime_type( int $attachment_id, string
 	$mime_type = $filetype['type'] ?? get_post_mime_type( $attachment_id );
 	return is_string( $mime_type ) ? $mime_type : '';
 }
+
+/**
+ * Checks if Imagick has AVIF transparency support.
+ *
+ * @since n.e.x.t
+ *
+ * @return bool True if Imagick has AVIF transparency support, false otherwise.
+ */
+function webp_uploads_imagick_avif_transparency_supported(): bool {
+	if ( extension_loaded( 'imagick' ) && class_exists( 'Imagick' ) ) {
+		$imagick_version = Imagick::getVersion();
+		if ( (bool) preg_match( '/\d+(?:\.\d+)+(?:-\d+)?/', $imagick_version['versionString'], $matches ) ) {
+			$imagick_version = $matches[0];
+		} else {
+			$imagick_version = $imagick_version['versionString'];
+		}
+		return version_compare( $imagick_version, '7.0.25', '>=' );
+	}
+
+	return false;
+}
+
+/**
+ * Checks if an AVIF image has transparency
+ *
+ * @since n.e.x.t
+ *
+ * @param string|null $filename The uploaded file name.
+ * @return bool Whether the image has transparency.
+ */
+function webp_uploads_check_image_transparency( ?string $filename ): bool {
+	static $processed_images = array();
+
+	if ( 'avif' !== webp_uploads_get_image_output_format() || webp_uploads_imagick_avif_transparency_supported() || ! class_exists( 'WebP_Uploads_Image_Editor_Imagick' ) ) {
+		return false;
+	}
+
+	if ( null === $filename ) {
+		if ( null === WebP_Uploads_Image_Editor_Imagick::$current_instance ) {
+			return false;
+		}
+		$file = WebP_Uploads_Image_Editor_Imagick::$current_instance->get_file();
+		if ( '' === $file ) {
+			return false;
+		}
+		$filename = $file;
+	}
+
+	if ( ! is_string( $filename ) || ! file_exists( $filename ) ) {
+		return false;
+	}
+
+	if ( isset( $processed_images[ $filename ] ) ) {
+		return $processed_images[ $filename ];
+	}
+	$processed_images[ $filename ] = false;
+
+	$editor = wp_get_image_editor( $filename );
+
+	if ( is_wp_error( $editor ) || ! $editor instanceof WebP_Uploads_Image_Editor_Imagick ) {
+		return false;
+	}
+
+	$has_transparency              = $editor->has_transparency();
+	$processed_images[ $filename ] = is_wp_error( $has_transparency ) ? false : $has_transparency;
+
+	return $processed_images[ $filename ];
+}

plugins/webp-uploads/hooks.php

@@ -65,8 +65,7 @@ function webp_uploads_create_sources_property( array $metadata, int $attachment_
 		return $metadata;
 	}
 
-	$valid_mime_transforms = webp_uploads_get_upload_image_mime_transforms();
-
+	$valid_mime_transforms = webp_uploads_get_upload_image_mime_transforms( $file );
 	// Not a supported mime type to create the sources property.
 	if ( ! isset( $valid_mime_transforms[ $mime_type ] ) ) {
 		return $metadata;
@@ -334,7 +333,7 @@ function webp_uploads_filter_image_editor_output_format( $output_format, ?string
 	}
 
 	// Use the original mime type if this type is allowed.
-	$valid_mime_transforms = webp_uploads_get_upload_image_mime_transforms();
+	$valid_mime_transforms = webp_uploads_get_upload_image_mime_transforms( $filename );
 	if (
 		! isset( $valid_mime_transforms[ $mime_type ] ) ||
 		in_array( $mime_type, $valid_mime_transforms[ $mime_type ], true )
@@ -970,3 +969,50 @@ function webp_uploads_convert_palette_png_to_truecolor( $file ): array {
 }
 add_filter( 'wp_handle_upload_prefilter', 'webp_uploads_convert_palette_png_to_truecolor' );
 add_filter( 'wp_handle_sideload_prefilter', 'webp_uploads_convert_palette_png_to_truecolor' );
+
+/**
+ * Overloads wp_image_editors() to load the extended class when AVIF transparency is not supported.
+ *
+ * @since n.e.x.t
+ *
+ * @param string[] $editors Array of available image editor class names. Defaults are 'WP_Image_Editor_Imagick', 'WP_Image_Editor_GD'.
+ * @return string[] Registered image editors class names.
+ */
+function webp_uploads_set_image_editors( array $editors ): array {
+	if ( 'avif' !== webp_uploads_get_image_output_format() || webp_uploads_imagick_avif_transparency_supported() ) {
+		return $editors;
+	}
+
+	if ( 0 === count( $editors ) || false === array_search( WP_Image_Editor_Imagick::class, $editors, true ) ) {
+		return $editors;
+	}
+
+	if ( ! class_exists( $editors[0] ) ) {
+		return $editors;
+	}
+
+	if ( ! class_exists( 'WebP_Uploads_Image_Editor_Imagick_Base' ) ) {
+		if ( WP_Image_Editor_Imagick::class !== $editors[0] ) {
+			if ( ! is_subclass_of( WP_Image_Editor_Imagick::class, $editors[0] ) ) {
+				return $editors;
+			} else {
+				$reflection = new ReflectionClass( $editors[0] );
+				if ( $reflection->isFinal() ) {
+					return $editors;
+				}
+				class_alias( $editors[0], 'WebP_Uploads_Image_Editor_Imagick_Base' );
+			}
+		} else {
+			class_alias( WP_Image_Editor_Imagick::class, 'WebP_Uploads_Image_Editor_Imagick_Base' );
+		}
+	}
+
+	if ( ! class_exists( 'WebP_Uploads_Image_Editor_Imagick' ) ) {
+		require_once __DIR__ . '/class-webp-uploads-image-editor-imagick.php'; // @codeCoverageIgnore
+	}
+
+	array_unshift( $editors, WebP_Uploads_Image_Editor_Imagick::class );
+
+	return $editors;
+}
+add_filter( 'wp_image_editors', 'webp_uploads_set_image_editors' );

plugins/webp-uploads/image-edit.php

@@ -127,7 +127,7 @@ function webp_uploads_update_image_onchange( $override, string $file_path, WP_Im
 		return (bool) $override;
 	}
 
-	$transforms = webp_uploads_get_upload_image_mime_transforms();
+	$transforms = webp_uploads_get_upload_image_mime_transforms( $file_path );
 	if ( ! isset( $transforms[ $mime_type ] ) || ! is_array( $transforms[ $mime_type ] ) || 0 === count( $transforms[ $mime_type ] ) ) {
 		return null;
 	}

plugins/webp-uploads/load.php

@@ -36,3 +36,4 @@
 require_once __DIR__ . '/picture-element.php';
 require_once __DIR__ . '/hooks.php';
 require_once __DIR__ . '/deprecated.php';
+require_once __DIR__ . '/site-health/load.php';

plugins/webp-uploads/site-health/imagick-avif-transparency-support/helper.php

@@ -0,0 +1,51 @@
+<?php
+/**
+ * Helper functions used for checking Imagick AVIF transparency support.
+ *
+ * @package webp-uploads
+ * @since n.e.x.t
+ */
+
+// @codeCoverageIgnoreStart
+if ( ! defined( 'ABSPATH' ) ) {
+	exit; // Exit if accessed directly.
+}
+// @codeCoverageIgnoreEnd
+
+/**
+ * Callback for Imagick AVIF transparency support test.
+ *
+ * @since n.e.x.t
+ *
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string} Result.
+ */
+function webp_uploads_imagick_avif_transparency_supported_test(): array {
+	$result = array(
+		'label'       => __( 'Your site supports AVIF image format transparency with ImageMagick', 'webp-uploads' ),
+		'status'      => 'good',
+		'badge'       => array(
+			'label' => __( 'Performance', 'webp-uploads' ),
+			'color' => 'blue',
+		),
+		'description' => sprintf(
+			'<p>%s</p>',
+			__( 'Older versions of ImageMagick do not support transparency in AVIF images, which can result in loss of transparency when uploading AVIF files.', 'webp-uploads' )
+		),
+		'actions'     => sprintf(
+			'<p><strong>%s</strong></p>',
+			__( 'Your ImageMagick installation supports AVIF transparency.', 'webp-uploads' )
+		),
+		'test'        => 'is_imagick_avif_transparency_supported_enabled',
+	);
+
+	if ( ! webp_uploads_imagick_avif_transparency_supported() ) {
+		$result['status']  = 'recommended';
+		$result['label']   = __( 'Your site does not support AVIF transparency', 'webp-uploads' );
+		$result['actions'] = sprintf(
+			'<p>%s</p>',
+			__( 'Update ImageMagick to the latest version by contacting your hosting provider.', 'webp-uploads' )
+		);
+	}
+
+	return $result;
+}

plugins/webp-uploads/site-health/imagick-avif-transparency-support/hooks.php

@@ -0,0 +1,30 @@
+<?php
+/**
+ * Hook callbacks used for checking Imagick AVIF transparency support.
+ *
+ * @package webp-uploads
+ * @since n.e.x.t
+ */
+
+// @codeCoverageIgnoreStart
+if ( ! defined( 'ABSPATH' ) ) {
+	exit; // Exit if accessed directly.
+}
+// @codeCoverageIgnoreEnd
+
+/**
+ * Adds tests to site health.
+ *
+ * @since n.e.x.t
+ *
+ * @param array{direct: array<string, array{label: string, test: string}>} $tests Site Health Tests.
+ * @return array{direct: array<string, array{label: string, test: string}>} Amended tests.
+ */
+function webp_uploads_add_imagick_avif_transparency_supported_test( array $tests ): array {
+	$tests['direct']['imagick_avif_transparency_supported'] = array(
+		'label' => __( 'Imagick AVIF Transparency Support', 'webp-uploads' ),
+		'test'  => 'webp_uploads_imagick_avif_transparency_supported_test',
+	);
+	return $tests;
+}
+add_filter( 'site_status_tests', 'webp_uploads_add_imagick_avif_transparency_supported_test' );