Paint Shop Pro would be the obvious pick, but it only supports 5x5 ordered dithering and a bunch of other not-so-neat noisy methods. I'd like more control over dithering, like a 2x2 dithering block or more options like that.
Do Photoshop or GIMP do what you need? Gimp is OpenSource and Free, so that would be my first pick. Especially since Adobe is trying to migrate CS to "the cloud".
ImageMagick should do it.
convert -ordered-dither threshold_map{,level...}
You can choose from these standard threshold maps:threshold 1x1 Threshold 1x1 (non-dither)checks 2x1 Checkerboard 2x1 (dither)o2x2 2x2 Ordered 2x2 (dispersed)o3x3 3x3 Ordered 3x3 (dispersed)o4x4 4x4 Ordered 4x4 (dispersed)o8x8 8x8 Ordered 8x8 (dispersed)h4x4a 4x1 Halftone 4x4 (angled)h6x6a 6x1 Halftone 6x6 (angled)h8x8a 8x1 Halftone 8x8 (angled)h4x4o Halftone 4x4 (orthogonal)h6x6o Halftone 6x6 (orthogonal)h8x8o Halftone 8x8 (orthogonal)h16x16o Halftone 16x16 (orthogonal)c5x5b c5x5 Circles 5x5 (black)c5x5w Circles 5x5 (white)c6x6b c6x6 Circles 6x6 (black)c6x6w Circles 6x6 (white)c7x7b c7x7 Circles 7x7 (black)c7x7w Circles 7x7 (white)
