Allow implicit conversion from gray8_ptr_t to gray8_step_ptr_t

[huangqinjin]

In this case, the memunit step is just sizeof(pixel).

[mloskot]

It would be helpful if you could explain rationale behind your suggestion, what's the use case.

[huangqinjin]

Such that gray8_view_t can convert to gray8_step_view_t implicitly.

[mloskot]

If there was one type of pixel/view/image available in GIL, such 'convenience' would make sense - wherever you see it missing - but it is a generic library...
Unless, you present an actual problem or use case in form of a minimum working example, then it will be very hard to see what you really mean.