There are many good plug-ins for web-safe gif preparation. But this one is
completely unique.
First of all, no matter what controls you press, no matter how much you adjust the contrast, brightness, and color values, you will always end up with an image that conforms to the Web Safe palette (216 colors). All the colors, not just the main ones, will be web-safe.
And your GIF will compress better than with any other method, because the web safe colors are arranged in the largest possible areas. Unlike any
other GIF preparation filter, this one gives you non-dithering images every time.
Just as importantly, this is the only plug-in that lets you use web safe
colors early in the design process, rather than forcing your image into the
web-safe palette as an afterthought.
Every other GIF compression utility that works with web safe colors does so after the graphic has been designed. Web Posterize turns this around; it
makes the 216 colors something you can introduce early in the design phase of a web page. Rather than squeezing your final image into something that either takes forever to download or looks cruddy, now you can use the 216 colors as a part of your design. Think about it.
TV art directors design for TV. They take its limits into account from the
very beginning. Newspaper art directors design for the limits of the newspaper medium. Shouldn't we have the same freedom when designing for the web? With Web Posterize, now we do.
Here is the interface:
 
desaturate & invert
The Desaturate control removes all the color from the image. The Invert control inverts the image.
brightness & contrast
These controls work just as you'd expect them to.
Note also how the color ramps are shifted when you adjust the controls. Contrast gives you a more compressed gradiation. This results in a more even shading over a small range of color. Adjust that small range with the brightness control.
the icons
The sphere icon shows a foreground (highlight in red) and a background (shadow in red).
the color bars
The color bars show how the current settings affect the range of colors in a 216 color cube.
The red, green and blue axes are shown. The grayscale ramp is a vector that runs from black to white.
red, green & blue
This is where you can adjust the foreground and background of the image.
You can subtract color from the foreground or add color to the background.
thanks
Thanks to Martin Archer for coming up with the trick for posterizing at 6-levels. And for sharing this trick with others.
For Martin's current home page and e-mail, please visit the Web Posterize page at www.furbo-filters.com