I'm trying to write an image with Mahotas and finding it strangely difficult.
img = mahotas.imread('foo.png', True)
mahotas.imsave('bar.png', img)
the error I'm gettings is:
ValueError: mahotas.freeimage: cannot write arrays of given type and shape.
I'm on OS X and used brew to install freeimage.
Author of mahotas here. The error message is not ideal (will fix it), but here's what's happening.
The greyscale image is a floating point image (i.e., img.dtype == numpy.float64) and you cannot save floating point images as PNGs.
Convert to numpy.uint8:
mahotas.imsave('test.png', img.astype(numpy.uint8))
and it will work as expected.