[Source]

Originally Posted by guidol

For converting Pictures to a e-ink Reader there is a nice page about the topic:
http://www.ebookworm.us/2011/05/31/d...-saver-images/

And here is a 16-Gray-PlugIn for GIMP:
http://www.ebookworm.us/wp-content/u...aysSixteen.zip

Thanks Guidol for the links.
I use Corel Photo-Paint X to manipulate images. It can convert color photos to different formats, bit resolutions, and dithering function is also available.