(PECL ps >= 1.1.0)
ps_restore — Restore previously save context
$psdoc): boolRestores a previously saved graphics context. Any call of ps_save() must be accompanied by a call to ps_restore(). All coordinate transformations, line style settings, color settings, etc. are being restored to the state before the call of ps_save().
成功时返回 true， 或者在失败时返回 false。