Images with a black and white 1-bit indexed palette should be saved as 1-bit grayscale PNG (#150865 adapted for png)
Submitted by michal maruska
PNG files saved as indexed (w/ pallete) 1-bit depth are larger than "grayscale" 1-bit images. This quick patch is a modification of the patch from bug report #150865. Unfortunately i don't know where to move a common function byte2bit.
Version: git master