Embedded graphics transformations

This crate provides generic implementations of simple transformations - rotate by 90 degree increments, mirroring and transposing.

These are intended to adapt generic graphics code to a particular display dimensions and orientation. It provides fixed transformation types which have no space overhead and minimal time overhead to adjust coordinates and dimensions. It also provides runtime-configurable rotations with minimal additional space and time overheads.

Because this is generic, it cannot take advantage of any hardware support for image rotation. In particular, DrawTarget::fill_contiguous will not use any specialized implementation.

This crate is no-std and has minimal additional dependencies.

lib.rs:

Add simple coordinate transforms for embedded graphics displays

This crate adds DrawTarget implementations which apply various simple transformations to coordinates as they're being written. This allows graphics output to be rotated or mirrored to display correctly on a specific display device.

Specifically, it implements:

• rotation by 90/180/270 degrees (and 0, for consistency)
• mirroring
• transposition

Note that these transformations can be composed if needed.

Because this is a completely generic implementation, it cannot take advantage of any hardware or driver specific specializations. In particular, DrawTarget::fill_contiguous must fall back to a generic implementation using draw_iter. (fill_solid and clear can use specialized implementations, however.)

All the transforms implement AsRef<D>/AsMut<D> to get access to the underlying display object so that its inherent functions can be called.