We'd like to support Gio using a different renderer binding than
the builtin. A first step is to define the Functions interface
in package gl, and extract the concrete implementations to a
separate package.
Updates #26
Signed-off-by: Elias Naur <mail@eliasnaur.com>
The origin of image.Images is the upper left corner. Convert the
ReadPixels result by flipping the image the y-direction.
Signed-off-by: Elias Naur <mail@eliasnaur.com>