Orientation API

[kaedroho]

Split from: #52 (comment)

This API would add support for rotations (in 90 degree increments), flipping and transposition of images.

The Orientation class.

This class represents a particular orientation. Orientations can be added or subtracted.

They can be constructed using one of the following methods:

Orientation.default()
Orientation.rotate(angle)  # angle must be in increments of 90
Orientation.flip_horizontal()
Orientation.flip_vertical()

The .get_exif_orientation() operation

Orientation can also be taken from the image's EXIF data using a new get_exif_orientation operation.

The .orient() operation

This takes an orientation object and applies it to the image.

transformed_image = image.orient(image.get_exif_orientation() + Orientation.flip_vertical() + Orientation.rotate(90))