GC_Image_Editor::get_output_format()

	protected function get_output_format( $filename = null, $mime_type = null ) {
		$new_ext = null;

		// By default, assume specified type takes priority.
		if ( $mime_type ) {
			$new_ext = $this->get_extension( $mime_type );
		}

		if ( $filename ) {
			$file_ext  = strtolower( pathinfo( $filename, PATHINFO_EXTENSION ) );
			$file_mime = $this->get_mime_type( $file_ext );
		} else {
			// If no file specified, grab editor's current extension and mime-type.
			$file_ext  = strtolower( pathinfo( $this->file, PATHINFO_EXTENSION ) );
			$file_mime = $this->mime_type;
		}

		// Check to see if specified mime-type is the same as type implied by
		// file extension. If so, prefer extension from file.
		if ( ! $mime_type || ( $file_mime == $mime_type ) ) {
			$mime_type = $file_mime;
			$new_ext   = $file_ext;
		}

		/**
		 * Filters the image editor output format mapping.
		 *
		 * Enables filtering the mime type used to save images. By default,
		 * the mapping array is empty, so the mime type matches the source image.
		 *
		 * @see GC_Image_Editor::get_output_format()
		 *
		 * @since 5.8.0
		 *
		 * @param string[] $output_format {
		 *     An array of mime type mappings. Maps a source mime type to a new
		 *     destination mime type. Default empty array.
		 *
		 *     @type string ...$0 The new mime type.
		 * }
		 * @param string $filename  Path to the image.
		 * @param string $mime_type The source image mime type.
		 * }
		 */
		$output_format = apply_filters( 'image_editor_output_format', array(), $filename, $mime_type );

		if ( isset( $output_format[ $mime_type ] )
			&& $this->supports_mime_type( $output_format[ $mime_type ] )
		) {
			$mime_type = $output_format[ $mime_type ];
			$new_ext   = $this->get_extension( $mime_type );
		}

		// Double-check that the mime-type selected is supported by the editor.
		// If not, choose a default instead.
		if ( ! $this->supports_mime_type( $mime_type ) ) {
			/**
			 * Filters default mime type prior to getting the file extension.
			 *
			 * @see gc_get_mime_types()
			 *
			 * @since 3.5.0
			 *
			 * @param string $mime_type Mime type string.
			 */
			$mime_type = apply_filters( 'image_editor_default_mime_type', $this->default_mime_type );
			$new_ext   = $this->get_extension( $mime_type );
		}

		// Ensure both $filename and $new_ext are not empty.
		// $this->get_extension() returns false on error which would effectively remove the extension
		// from $filename. That shouldn't happen, files without extensions are not supported.
		if ( $filename && $new_ext ) {
			$dir = pathinfo( $filename, PATHINFO_DIRNAME );
			$ext = pathinfo( $filename, PATHINFO_EXTENSION );

			$filename = trailingslashit( $dir ) . gc_basename( $filename, ".$ext" ) . ".{$new_ext}";
		}

		if ( $mime_type && ( $mime_type !== $this->mime_type ) ) {
			// The image will be converted when saving. Set the quality for the new mime-type if not already set.
			if ( $mime_type !== $this->output_mime_type ) {
				$this->output_mime_type = $mime_type;
				$this->set_quality();
			}
		} elseif ( ! empty( $this->output_mime_type ) ) {
			// Reset output_mime_type and quality.
			$this->output_mime_type = null;
			$this->set_quality();
		}

		return array( $filename, $new_ext, $mime_type );
	}