Source

File: wp-includes/class-wp-image-editor-imagick.php

protected function update_size( $width = null, $height = null ) {
		$size = null;
		if ( ! $width || ! $height ) {
			try {
				$size = $this->image->getImageGeometry();
			} catch ( Exception $e ) {
				return new WP_Error( 'invalid_image', __( 'Could not read image size.' ), $this->file );
			}
		}

		if ( ! $width ) {
			$width = $size['width'];
		}

		if ( ! $height ) {
			$height = $size['height'];
		}

		return parent::update_size( $width, $height );
	}