diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/class-wp-image-editor-gd.php
--- a/wp/wp-includes/class-wp-image-editor-gd.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/class-wp-image-editor-gd.php	Tue Dec 15 13:49:49 2020 +0100
@@ -23,7 +23,7 @@
 
 	public function __destruct() {
 		if ( $this->image ) {
-			// we don't need the original in memory anymore
+			// We don't need the original in memory anymore.
 			imagedestroy( $this->image );
 		}
 	}
@@ -41,9 +41,9 @@
 			return false;
 		}
 
-		// On some setups GD library does not provide imagerotate() - Ticket #11536
+		// On some setups GD library does not provide imagerotate() - Ticket #11536.
 		if ( isset( $args['methods'] ) &&
-			in_array( 'rotate', $args['methods'] ) &&
+			in_array( 'rotate', $args['methods'], true ) &&
 			! function_exists( 'imagerotate' ) ) {
 
 				return false;
@@ -146,9 +146,9 @@
 	 *
 	 * @since 3.5.0
 	 *
-	 * @param  int|null $max_w Image width.
-	 * @param  int|null $max_h Image height.
-	 * @param  bool     $crop
+	 * @param int|null $max_w Image width.
+	 * @param int|null $max_h Image height.
+	 * @param bool     $crop
 	 * @return true|WP_Error
 	 */
 	public function resize( $max_w, $max_h, $crop = false ) {
@@ -171,16 +171,18 @@
 	}
 
 	/**
-	 * @param int $max_w
-	 * @param int $max_h
+	 * @param int        $max_w
+	 * @param int        $max_h
 	 * @param bool|array $crop
 	 * @return resource|WP_Error
 	 */
 	protected function _resize( $max_w, $max_h, $crop = false ) {
 		$dims = image_resize_dimensions( $this->size['width'], $this->size['height'], $max_w, $max_h, $crop );
+
 		if ( ! $dims ) {
 			return new WP_Error( 'error_getting_dimensions', __( 'Could not calculate resized image dimensions' ), $this->file );
 		}
+
 		list( $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h ) = $dims;
 
 		$resized = wp_imagecreatetruecolor( $dst_w, $dst_h );
@@ -195,16 +197,24 @@
 	}
 
 	/**
-	 * Resize multiple images from a single source.
+	 * Create multiple smaller images from a single source.
+	 *
+	 * Attempts to create all sub-sizes and returns the meta data at the end. This
+	 * may result in the server running out of resources. When it fails there may be few
+	 * "orphaned" images left over as the meta data is never returned and saved.
+	 *
+	 * As of 5.3.0 the preferred way to do this is with `make_subsize()`. It creates
+	 * the new images one at a time and allows for the meta data to be saved after
+	 * each new image is created.
 	 *
 	 * @since 3.5.0
 	 *
 	 * @param array $sizes {
-	 *     An array of image size arrays. Default sizes are 'small', 'medium', 'medium_large', 'large'.
+	 *     An array of image size data arrays.
 	 *
 	 *     Either a height or width must be provided.
 	 *     If one of the two is set to null, the resize will
-	 *     maintain aspect ratio according to the provided dimension.
+	 *     maintain aspect ratio according to the source image.
 	 *
 	 *     @type array $size {
 	 *         Array of height, width values, and whether to crop.
@@ -217,46 +227,72 @@
 	 * @return array An array of resized images' metadata by size.
 	 */
 	public function multi_resize( $sizes ) {
-		$metadata  = array();
-		$orig_size = $this->size;
+		$metadata = array();
 
 		foreach ( $sizes as $size => $size_data ) {
-			if ( ! isset( $size_data['width'] ) && ! isset( $size_data['height'] ) ) {
-				continue;
-			}
-
-			if ( ! isset( $size_data['width'] ) ) {
-				$size_data['width'] = null;
-			}
-			if ( ! isset( $size_data['height'] ) ) {
-				$size_data['height'] = null;
-			}
-
-			if ( ! isset( $size_data['crop'] ) ) {
-				$size_data['crop'] = false;
-			}
+			$meta = $this->make_subsize( $size_data );
 
-			$image     = $this->_resize( $size_data['width'], $size_data['height'], $size_data['crop'] );
-			$duplicate = ( ( $orig_size['width'] == $size_data['width'] ) && ( $orig_size['height'] == $size_data['height'] ) );
-
-			if ( ! is_wp_error( $image ) && ! $duplicate ) {
-				$resized = $this->_save( $image );
-
-				imagedestroy( $image );
-
-				if ( ! is_wp_error( $resized ) && $resized ) {
-					unset( $resized['path'] );
-					$metadata[ $size ] = $resized;
-				}
+			if ( ! is_wp_error( $meta ) ) {
+				$metadata[ $size ] = $meta;
 			}
-
-			$this->size = $orig_size;
 		}
 
 		return $metadata;
 	}
 
 	/**
+	 * Create an image sub-size and return the image meta data value for it.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param array $size_data {
+	 *     Array of size data.
+	 *
+	 *     @type int  $width  The maximum width in pixels.
+	 *     @type int  $height The maximum height in pixels.
+	 *     @type bool $crop   Whether to crop the image to exact dimensions.
+	 * }
+	 * @return array|WP_Error The image data array for inclusion in the `sizes` array in the image meta,
+	 *                        WP_Error object on error.
+	 */
+	public function make_subsize( $size_data ) {
+		if ( ! isset( $size_data['width'] ) && ! isset( $size_data['height'] ) ) {
+			return new WP_Error( 'image_subsize_create_error', __( 'Cannot resize the image. Both width and height are not set.' ) );
+		}
+
+		$orig_size = $this->size;
+
+		if ( ! isset( $size_data['width'] ) ) {
+			$size_data['width'] = null;
+		}
+
+		if ( ! isset( $size_data['height'] ) ) {
+			$size_data['height'] = null;
+		}
+
+		if ( ! isset( $size_data['crop'] ) ) {
+			$size_data['crop'] = false;
+		}
+
+		$resized = $this->_resize( $size_data['width'], $size_data['height'], $size_data['crop'] );
+
+		if ( is_wp_error( $resized ) ) {
+			$saved = $resized;
+		} else {
+			$saved = $this->_save( $resized );
+			imagedestroy( $resized );
+		}
+
+		$this->size = $orig_size;
+
+		if ( ! is_wp_error( $saved ) ) {
+			unset( $saved['path'] );
+		}
+
+		return $saved;
+	}
+
+	/**
 	 * Crops Image.
 	 *
 	 * @since 3.5.0
@@ -271,8 +307,8 @@
 	 * @return bool|WP_Error
 	 */
 	public function crop( $src_x, $src_y, $src_w, $src_h, $dst_w = null, $dst_h = null, $src_abs = false ) {
-		// If destination width/height isn't specified, use same as
-		// width/height from source.
+		// If destination width/height isn't specified,
+		// use same as width/height from source.
 		if ( ! $dst_w ) {
 			$dst_w = $src_w;
 		}
@@ -379,10 +415,10 @@
 	}
 
 	/**
-	 * @param resource $image
+	 * @param resource    $image
 	 * @param string|null $filename
 	 * @param string|null $mime_type
-	 * @return WP_Error|array
+	 * @return array|WP_Error
 	 */
 	protected function _save( $image, $filename = null, $mime_type = null ) {
 		list( $filename, $extension, $mime_type ) = $this->get_output_format( $filename, $mime_type );
@@ -391,12 +427,12 @@
 			$filename = $this->generate_filename( null, null, $extension );
 		}
 
-		if ( 'image/gif' == $mime_type ) {
+		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' ) );
 			}
-		} elseif ( 'image/png' == $mime_type ) {
-			// convert from full colors to index colors, like original PNG.
+		} elseif ( 'image/png' === $mime_type ) {
+			// Convert from full colors to index colors, like original PNG.
 			if ( function_exists( 'imageistruecolor' ) && ! imageistruecolor( $image ) ) {
 				imagetruecolortopalette( $image, false, imagecolorstotal( $image ) );
 			}
@@ -404,7 +440,7 @@
 			if ( ! $this->make_image( $filename, 'imagepng', array( $image, $filename ) ) ) {
 				return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
 			}
-		} elseif ( 'image/jpeg' == $mime_type ) {
+		} elseif ( 'image/jpeg' === $mime_type ) {
 			if ( ! $this->make_image( $filename, 'imagejpeg', array( $image, $filename, $this->get_quality() ) ) ) {
 				return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
 			}
@@ -412,20 +448,20 @@
 			return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
 		}
 
-		// Set correct file permissions
+		// Set correct file permissions.
 		$stat  = stat( dirname( $filename ) );
-		$perms = $stat['mode'] & 0000666; //same permissions as parent folder, strip off the executable bits
-		@ chmod( $filename, $perms );
+		$perms = $stat['mode'] & 0000666; // Same permissions as parent folder, strip off the executable bits.
+		chmod( $filename, $perms );
 
-		/**
-		 * Filters the name of the saved image file.
-		 *
-		 * @since 2.6.0
-		 *
-		 * @param string $filename Name of the file.
-		 */
 		return array(
 			'path'      => $filename,
+			/**
+			 * Filters the name of the saved image file.
+			 *
+			 * @since 2.6.0
+			 *
+			 * @param string $filename Name of the file.
+			 */
 			'file'      => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
 			'width'     => $this->size['width'],
 			'height'    => $this->size['height'],
@@ -463,8 +499,8 @@
 	 * @since 3.5.0
 	 *
 	 * @param string|stream $filename
-	 * @param callable $function
-	 * @param array $arguments
+	 * @param callable      $function
+	 * @param array         $arguments
 	 * @return bool
 	 */
 	protected function make_image( $filename, $function, $arguments ) {