WordPress
diff --git a/modules/images/webp-uploads/helper.php b/modules/images/webp-uploads/helper.php
@@ -240,3 +240,35 @@ function webp_uploads_get_attachment_sources( $attachment_id, $size = 'thumbnail
 	// Return an empty array if no sources found.
 	return array();
 }
+
+/**
+ * Check whether the additional image is larger than the original image.
+ *
+ * @since n.e.x.t
+ *
+ * @param array $original   An array with the metadata of the attachment.
+ * @param array $additional An array containing the filename and file size for additional mime.
+ * @return bool True if the additional image is larger than the original image, otherwise false.
+ */
+function webp_uploads_should_discard_additional_image_file( array $original, array $additional ) {
+	$original_image_filesize   = isset( $original['filesize'] ) ? (int) $original['filesize'] : 0;
+	$additional_image_filesize = isset( $additional['filesize'] ) ? (int) $additional['filesize'] : 0;
+	if ( $original_image_filesize > 0 && $additional_image_filesize > 0 ) {
+		/**
+		 * Filter whether WebP images that are larger than the matching JPEG should be discarded.
+		 *
+		 * By default the performance lab plugin will use the mime type with the smaller filesize
+		 * rather than defaulting to `webp`.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @param bool $preferred_filesize Prioritize file size over mime type. Default true.
+		 */
+		$webp_discard_larger_images = apply_filters( 'webp_uploads_discard_larger_generated_images', true );
+
+		if ( $webp_discard_larger_images && $additional_image_filesize >= $original_image_filesize ) {
+			return true;
+		}
+	}
+	return false;
+}
diff --git a/modules/images/webp-uploads/load.php b/modules/images/webp-uploads/load.php
@@ -96,6 +96,11 @@ function webp_uploads_create_sources_property( array $metadata, $attachment_id )
 			continue;
 		}
 
+		if ( webp_uploads_should_discard_additional_image_file( $metadata, $image ) ) {
+			wp_delete_file_from_directory( $destination, $original_directory );
+			continue;
+		}
+
 		$metadata['sources'][ $targeted_mime ] = $image;
 		wp_update_attachment_metadata( $attachment_id, $metadata );
 	}
@@ -156,6 +161,12 @@ function webp_uploads_create_sources_property( array $metadata, $attachment_id )
 				continue;
 			}
 
+			if ( webp_uploads_should_discard_additional_image_file( $properties, $source ) ) {
+				$destination = path_join( $original_directory, $source['file'] );
+				wp_delete_file_from_directory( $destination, $original_directory );
+				continue;
+			}
+
 			$properties['sources'][ $mime ]  = $source;
 			$metadata['sizes'][ $size_name ] = $properties;
 			wp_update_attachment_metadata( $attachment_id, $metadata );
@@ -481,6 +492,7 @@ function webp_uploads_update_image_references( $content ) {
  * for the specified image sizes, the *.webp references are stored inside of each size.
  *
  * @since 1.0.0
+ * @since n.e.x.t Remove `webp_uploads_prefer_smaller_image_file` filter
  *
  * @param string $original_image An <img> tag where the urls would be updated.
  * @param string $context        The context where this is function is being used.
@@ -490,24 +502,11 @@ function webp_uploads_update_image_references( $content ) {
 function webp_uploads_img_tag_update_mime_type( $original_image, $context, $attachment_id ) {
 	$image    = $original_image;
 	$metadata = wp_get_attachment_metadata( $attachment_id );
+
 	if ( empty( $metadata['file'] ) ) {
 		return $image;
 	}
 
-	/**
-	 * Filters whether the smaller image should be used regardless of which MIME type is preferred overall.
-	 *
-	 * This is disabled by default only because it is not part of the current WordPress core feature proposal.
-	 *
-	 * By enabling this, the plugin will compare the image file sizes and prefer the smaller file regardless of MIME
-	 * type.
-	 *
-	 * @since 1.0.0
-	 *
-	 * @param bool $prefer_smaller_image_file Whether to prefer the smaller image file.
-	 */
-	$prefer_smaller_image_file = apply_filters( 'webp_uploads_prefer_smaller_image_file', false );
-
 	/**
 	 * Filters mime types that should be used to update all images in the content. The order of
 	 * mime types matters. The first mime type in the list will be used if it is supported by an image.
@@ -523,58 +522,73 @@ function webp_uploads_img_tag_update_mime_type( $original_image, $context, $atta
 	// Get the original mime type for comparison.
 	$original_mime = get_post_mime_type( $attachment_id );
 
-	$target_mime = null;
-	foreach ( $target_mimes as $mime ) {
-		if ( isset( $metadata['sources'][ $mime ] ) ) {
-			$target_mime = $mime;
-			break;
+	foreach ( $target_mimes as $target_mime ) {
+
+		if ( $target_mime === $original_mime ) {
+			continue;
 		}
-	}
 
-	if ( null === $target_mime ) {
-		return $image;
-	}
+		if ( ! isset( $metadata['sources'][ $target_mime ]['file'] ) ) {
+			continue;
+		}
 
-	// Replace the full size image if present.
-	if ( isset( $metadata['sources'][ $target_mime ]['file'] ) ) {
-		// Initially set the target mime as the replacement source.
-		$replacement_source = $metadata['sources'][ $target_mime ]['file'];
+		/**
+		 * Filter to replace additional image source file, by locating the original
+		 * mime types of the file and return correct file path in the end.
+		 *
+		 * Altering the $image tag through this filter effectively short-circuits the default replacement logic using the preferred MIME type.
+		 *
+		 * @since 1.1.0
+		 *
+		 * @param string $image         An <img> tag where the urls would be updated.
+		 * @param int    $attachment_id The ID of the attachment being modified.
+		 * @param string $size          The size name that would be used to create this image, out of the registered subsizes.
+		 * @param string $target_mime   The target mime in which the image should be created.
+		 * @param string $context       The context where this is function is being used.
+		 */
+		$filtered_image = (string) apply_filters( 'webp_uploads_pre_replace_additional_image_source', $image, $attachment_id, 'full', $target_mime, $context );
 
-		// Check for the smaller image file.
-		if (
-			$prefer_smaller_image_file &&
-			! empty( $metadata['sources'][ $target_mime ]['filesize'] ) &&
-			! empty( $metadata['sources'][ $original_mime ]['filesize'] ) &&
-			$metadata['sources'][ $original_mime ]['filesize'] < $metadata['sources'][ $target_mime ]['filesize']
-		) {
-			// Set the original source file as the replacement if smaller.
-			$replacement_source = $metadata['sources'][ $original_mime ]['file'];
+		// If filtered image is same as the image, run our own replacement logic, otherwise rely on the filtered image.
+		if ( $filtered_image === $image ) {
+			$basename = wp_basename( $metadata['file'] );
+			$image    = str_replace(
+				$basename,
+				$metadata['sources'][ $target_mime ]['file'],
+				$image
+			);
+		} else {
+			$image = $filtered_image;
+		}
+	}
+
+	// Replace sub sizes for the image if present.
+	foreach ( $metadata['sizes'] as $size => $size_data ) {
+		if ( empty( $size_data['file'] ) ) {
+			continue;
 		}
 
-		$basename = wp_basename( $metadata['file'] );
-		if ( $basename !== $replacement_source ) {
+		foreach ( $target_mimes as $target_mime ) {
 
-			/**
-			 * Filter to replace additional image source file, by locating the original
-			 * mime types of the file and return correct file path in the end.
-			 *
-			 * Altering the $image tag through this filter effectively short-circuits the default replacement logic using the preferred MIME type.
-			 *
-			 * @since 1.1.0
-			 *
-			 * @param string $image         An <img> tag where the urls would be updated.
-			 * @param int    $attachment_id The ID of the attachment being modified.
-			 * @param string $size          The size name that would be used to create this image, out of the registered subsizes.
-			 * @param string $target_mime   The target mime in which the image should be created.
-			 * @param string $context       The context where this is function is being used.
-			 */
-			$filtered_image = (string) apply_filters( 'webp_uploads_pre_replace_additional_image_source', $image, $attachment_id, 'full', $target_mime, $context );
+			if ( $target_mime === $original_mime ) {
+				continue;
+			}
+
+			if ( ! isset( $size_data['sources'][ $target_mime ]['file'] ) ) {
+				continue;
+			}
+
+			if ( $size_data['file'] === $size_data['sources'][ $target_mime ]['file'] ) {
+				continue;
+			}
+
+			/** This filter is documented in modules/images/webp-uploads/load.php */
+			$filtered_image = (string) apply_filters( 'webp_uploads_pre_replace_additional_image_source', $image, $attachment_id, $size, $target_mime, $context );
 
 			// If filtered image is same as the image, run our own replacement logic, otherwise rely on the filtered image.
 			if ( $filtered_image === $image ) {
 				$image = str_replace(
-					$basename,
-					$metadata['sources'][ $target_mime ]['file'],
+					$size_data['file'],
+					$size_data['sources'][ $target_mime ]['file'],
 					$image
 				);
 			} else {
@@ -583,53 +597,21 @@ function webp_uploads_img_tag_update_mime_type( $original_image, $context, $atta
 		}
 	}
 
-	// Replace sub sizes for the image if present.
-	foreach ( $metadata['sizes'] as $size => $size_data ) {
-		if ( empty( $size_data['file'] ) ) {
-			continue;
-		}
-
-		if ( empty( $size_data['sources'][ $target_mime ]['file'] ) ) {
-			continue;
-		}
+	foreach ( $target_mimes as $target_mime ) {
 
-		if ( $size_data['file'] === $size_data['sources'][ $target_mime ]['file'] ) {
+		if ( $target_mime === $original_mime ) {
 			continue;
 		}
 
-		// Do not update image URL if the target image is larger than the original.
 		if (
-			$prefer_smaller_image_file &&
-			! empty( $size_data['sources'][ $target_mime ]['filesize'] ) &&
-			! empty( $size_data['sources'][ $original_mime ]['filesize'] ) &&
-			$size_data['sources'][ $original_mime ]['filesize'] < $size_data['sources'][ $target_mime ]['filesize']
+			! has_action( 'wp_footer', 'webp_uploads_wepb_fallback' ) &&
+			$image !== $original_image &&
+			'the_content' === $context &&
+			'image/jpeg' === $original_mime &&
+			'image/webp' === $target_mime
 		) {
-			continue;
+			add_action( 'wp_footer', 'webp_uploads_wepb_fallback' );
 		}
-
-		/** This filter is documented in modules/images/webp-uploads/load.php */
-		$filtered_image = (string) apply_filters( 'webp_uploads_pre_replace_additional_image_source', $image, $attachment_id, $size, $target_mime, $context );
-
-		// If filtered image is same as the image, run our own replacement logic, otherwise rely on the filtered image.
-		if ( $filtered_image === $image ) {
-			$image = str_replace(
-				$size_data['file'],
-				$size_data['sources'][ $target_mime ]['file'],
-				$image
-			);
-		} else {
-			$image = $filtered_image;
-		}
-	}
-
-	if (
-		! has_action( 'wp_footer', 'webp_uploads_wepb_fallback' ) &&
-		$image !== $original_image &&
-		'the_content' === $context &&
-		'image/jpeg' === $original_mime &&
-		'image/webp' === $target_mime
-	) {
-		add_action( 'wp_footer', 'webp_uploads_wepb_fallback' );
 	}
 
 	return $image;

diff --git a/tests/modules/images/webp-uploads/helper-tests.php b/tests/modules/images/webp-uploads/helper-tests.php
@@ -410,4 +410,48 @@ function () {
 		$this->assertIsArray( $transforms );
 		$this->assertSame( array( 'image/jpeg' => array( 'image/jpeg', 'image/webp' ) ), $transforms );
 	}
+
+	/**
+	 * @dataProvider data_provider_image_filesize
+	 *
+	 * @test
+	 */
+	public function it_should_discard_additional_image_if_larger_than_the_original_image( $original_filesize, $additional_filesize, $expected_status ) {
+		add_filter( 'webp_uploads_discard_larger_generated_images', '__return_true' );
+
+		$output = webp_uploads_should_discard_additional_image_file( $original_filesize, $additional_filesize );
+		$this->assertSame( $output, $expected_status );
+	}
+
+	public function data_provider_image_filesize() {
+		return array(
+			array(
+				array( 'filesize' => 120101 ),
+				array( 'filesize' => 100101 ),
+				false,
+			),
+			array(
+				array( 'filesize' => 100101 ),
+				array( 'filesize' => 120101 ),
+				true,
+			),
+			array(
+				array( 'filesize' => 10101 ),
+				array( 'filesize' => 10101 ),
+				true,
+			),
+		);
+	}
+
+	/**
+	 * @dataProvider data_provider_image_filesize
+	 *
+	 * @test
+	 */
+	public function it_should_never_discard_additional_image_if_filter_is_false( $original_filesize, $additional_filesize ) {
+		add_filter( 'webp_uploads_discard_larger_generated_images', '__return_false' );
+
+		$output = webp_uploads_should_discard_additional_image_file( $original_filesize, $additional_filesize );
+		$this->assertFalse( $output );
+	}
 }
diff --git a/tests/modules/images/webp-uploads/image-edit-tests.php b/tests/modules/images/webp-uploads/image-edit-tests.php
@@ -10,6 +10,12 @@
 
 class WebP_Uploads_Image_Edit_Tests extends ImagesTestCase {
 
+	public function set_up() {
+		parent::set_up();
+
+		add_filter( 'webp_uploads_discard_larger_generated_images', '__return_false' );
+	}
+
 	/**
 	 * Backup the sources structure alongside the full size
 	 *