Web Posterize

As we all know, on the web, an image is only as good as its download time. 1 MB Picassos languish, while 18k Leroy Neimans thrive.
          Particularly with gifs, the more areas of flat color you have, the better the compression. And that's where Web Posterize comes in

Web Posterize reduces any image to the 216 web-safe colors (aka Netscape palette, aka Netscape CLUT, aka 216 color cube), so that it looks as good on low-end machines as it does on a 32-bit powerhouse. Admittedly, other plug-ins (like Boxtop Software's PhotoGif) can do that as well.
          But Web Posterize takes the process one step farther by recreating your image with the largest possible areas of flat color, and no other plug-in does that.
          These large color areas enable the gif format's LZW compression do really do its thing – resulting in tiny file sizes and zippy downloads. Your images will fly into the browser window, even if your site is housed on a less-than-powerful server.
          No matter how you adjust the brightness, contrast, and other controls, you will always be inside the "web-safe" color palette. Yet your image is anything but limited, thanks to a wide range of controls:

Desaturate & invert

Desaturate removes all color from the image. Invert does just what you think it does (black is white, etc.)

Brightness & contrast

These work just as you'd expect them to. You'll also notice how the color ramps shift as you adjust the controls. Contrast gives you a more compressed gradation, resulting in a more even shading over a smaller range of color. (Adjust that small range with the brightness control.)

Icons

The sphere icon shows you foreground (highlight in red) and background (shadow in red).

Color bars

These show how current settings affect the range of colors in the 216 color cube. Red, green and blue axes are shown. The grayscale ramp is a vector which runs from black to white.

Red, green and blue

Here you can adjust your image's foreground and background. You may subtract color from the foreground, or add color to the background.

Tour top

Download now!

Thanks!

This filter would not be possible without the brilliant Martin "Arch" Archer, who first conceived the trick of posterizing at 6 levels to achieve web-safe images, and who generously shared the concept with this site's authors.

Extracurricular

For additional info on web graphics, color palettes and file size reduction, see Jeffrey's Ask Dr Web. It will give you something to read while downloading the Webmaster Pack.