[quote="Zongpei_Jiang, post:6, topic:4607"] So thats why i want to create a type like `imguint8` that i can also create a `BytesImage.msg` which use the type to deliver image messages like what `Image.msg` does . [/quote] The primitive type should not by specific to what "semantic" data you put in. Therefore `img` is in my opinion a no-go. The same type could also store other binary data. [quote="Zongpei_Jiang, post:6, topic:4607"] Just map all the `uint8[]` to `bytes[]` instead of `list[]` may cause other problems since some algorithms are designed using the `msg.data` as `list` in python . [/quote] That is why I recommended using `byte[]`. --- [Visit Topic](https://discourse.ros.org/t/discussion-about-how-to-add-a-new-primitive-types-to-rosidl-msg/4607/8) or reply to this email to respond. If you do not want to receive messages from ros-users please use the unsubscribe link below. If you use the one above, you will stop all of ros-users from receiving updates. ______________________________________________________________________________ ros-users mailing list ros-users@lists.ros.org http://lists.ros.org/mailman/listinfo/ros-users Unsubscribe: