enum ImageTurn

A quarter turn applied to an image as it is decoded.

Clockwise, and stated as a direction rather than an angle because that is what the two buttons on a viewer's bar mean and there is nothing else this is for. It is applied after the orientation the file itself declares, so it composes with what the user is already looking at rather than with how the sensor happened to read out — see render/exif.hpp.

Part of a texture's identity, like maxPixelSize: the same photograph upright and turned is two textures, and a client that asks for one must not be handed the other.