Source

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

protected function _save( $image, $filename = null, $mime_type = null ) {
		list( $filename, $extension, $mime_type ) = $this->get_output_format( $filename, $mime_type );

		if ( ! $filename ) {
			$filename = $this->generate_filename( null, null, $extension );
		}

		try {
			// Store initial format.
			$orig_format = $this->image->getImageFormat();

			$this->image->setImageFormat( strtoupper( $this->get_extension( $mime_type ) ) );
			$this->make_image( $filename, array( $image, 'writeImage' ), array( $filename ) );

			// Reset original format.
			$this->image->setImageFormat( $orig_format );
		} catch ( Exception $e ) {
			return new WP_Error( 'image_save_error', $e->getMessage(), $filename );
		}

		// 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 );

		return array(
			'path'      => $filename,
			/** This filter is documented in wp-includes/class-wp-image-editor-gd.php */
			'file'      => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
			'width'     => $this->size['width'],
			'height'    => $this->size['height'],
			'mime-type' => $mime_type,
		);
	}