pngpack: lossless image compression for a series of screen shots
Copyright (C) 2005-2009 Carsten Gnoerlich.

pngpack is a specialized archival format for distributing screen
shots (which are typically shipped with on-line documentation).

pngpack provides lossless compression which exploits redundancy 
in a series of images. For example, if you have a collection of 
screen shots which all contain a "Quit" button, the image of the 
"Quit" button is stored once and will then be re-used in all other 
images. 

In a typical scenario, a single image compresses about
30-40% better than PNG, and a series of 10 similar images
can save upto 90% of the storage if PNG had been used.

However, no offense is intended against PNG - PNG is a great
general purpose format and it is actually used as input and
output format for pngpack.

In order to get the best compression out of pngpack, 
use images with a regular structure and very few colors.

pngpack works best with screen shots of user interfaces 
and simple computer generated charts and slides.
Avoid including color gradients, background patterns and
photorealistic backgrounds. For screen shots, do not use
theming and use a single color for your window and desktop
background.


