Saving images requires C-contiguous data, but this is not checked

Created by: siebenkopf

When writing (color) images that are not C-contiguous, the written images are garbage (mis-aligned), while C-contiguous data works fine:

import bob.io.base
import bob.io.image
import numpy
image = bob.io.base.load("image.png")
bob.io.base.save(image[:, 10:50, 10:50], "garbage.png")
bob.io.base.save(numpy.array(image[:, 10:50, 10:50]), "good.png")

I think, we need at least to check for C-contiguity before writing images.