API: Inversed grayscale image format
API: Inversed grayscale image format

To be used for scanners returning white lines images.

Signed-off-by: Pawel Moll <54329ff2dc18fbe9d024c289c55c3d14a8ff27ff@pawelmoll.com>

pawelmoll/scannerAPI,pawelmoll/scannerAPI,pawelmoll/scannerAPI