Quote:..My GIMP doesn't allow me to create a black+white (1-bit) image. Minimum is 8-bit...
Not true, just the way IM reports. You can always compare file sizes. This the same image, exported as a 1bit indexed file and then exported as 8bit RGBA.
Edit: If you want IM to report as 1 bit then the same indexed - 1 bit image exported as a tiff.
That is me out, best of luck