Digital Image Formats - A Practical Guide to Video and Audio Compression - page 135

graphic images can be presented in a very appealing way. Several people have offered
improvements since then, and the basic technique is now used all over the world every
day to create high-quality images on systems with limited resources.
Figure 6-13 shows a photograph, followed by a simple threshold mapping from
grayscale to 1 bit and no dither. The third pane uses a pattern dither and the fourth uses
error diffusion.

6.11.7 Albie Dithering

The Albie dithering technique is specially designed to deal with images that are going to
be displayed on an interlaced monitor, which is what is required for TV imagery. The
dithering technique is very similar to the Floyd-Steinberg error diffusion algorithm. Albie
produces slightly better contrast but also exhibits some increased grain and contouring on

Original grayscale 50% threshold

Pattern dither Diffusion dither

Figure 6-13 Error diffusion dithering.

Floyd-Steinberg derived algorithms: http://www.wellesley.edu/CS/pmetaxas/ei99.pdf
Modified Floyd-Steinberg algorithm: http://www.cs.indiana.edu/pub/techreports/TR458.pdf
ACM Digital Library article: http://portal.acm.org / citation.cfm?id=35039.35040