Comment 6 for bug 494754

I don't see these as big issues:
- If your scanner doesn't support the requested DPI then the largest possible is used
- If your scanner doesn't support color then grayscale is used (which will not suprise the user as they surely know their scanner doesn't do color)
- If your scanner doesn't do LineArt, then we just need to post-process the image so it looks similar to LineArt.

My assumption is the vast majority of consumer scanners out there will support all 3, if not, you need to use xsane or similar.