Hi Marty, A picture is data from a sensor. In this case, the sensor is a camera. The sensor is far from perfect. A picture that is supposed to have 3 colors could easily be more than 15,000 colors. The data that has value from any picture is call the signal and everything else is called noise. For example, if we are trying to see an animal in the forest, the dots belonging to the animal contain the data (and a lot of noise), and all other dots are called noise. I'm not speaking down to you, I'm just giving you some background information.
Color grouping (aka color segmentation) and shape grouping are noise suppression techniques that eliminate most of the noise in an image. When the noise is reduced, SVG becomes much more efficient. No information (signal) can be extracted from a picture unless two or more dots are constellated into a group. In graphics (from machine vision I think), this is called a blob. It is immaterial whether the dots in a blob have different colors. As humans, we group by colors. In other words, if the data is not constellated by color, then we can't see it. Each group has one color. In SVG, a path is closed around a blob and filled with a single color. When a photograph is converted to SVG, everyone does color grouping. Most color groupers rely on frequency analysis or averaging techniques. These techniques produce file sizes that are about 15 times larger than a JPG, and they look much worse. It is all about signal to noise extraction. At our company, we use a much more involved color grouping process, and for that effort we can color group well enough that our files are about 1.5 times larger than SVG and they are somewhat comparable to JPG. We haven't added shape grouping, yet, but that would reduce the noise further which would allow us to produce SVG which has a smaller file size than JPG. Shape grouping is explained in my previous E-mail. When shape grouping uses geographic shapes as the objective (we call this entropic compression), then we can do about 10 times better than JPG, and the quality is higher than JPG. More compression can be obtained by organizing the mathematical representation, but I will leave that for later. ------------------------------------ ----- To unsubscribe send a message to: [email protected] -or- visit http://groups.yahoo.com/group/svg-developers and click "edit my membership" ----Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
