A Guide to Web Image Compression Software: ColorSafe
Software type: Websafe palette optimisers
function: to create “web-safe” dithered palettes to allow 24 bit sythetic colours from 8 bit
This is not a conventional application to reduce the size of an existing GIF. It's intended to build a "palette" that can be used to make GIFs, using web-safe colours, but yielding a wide range of effective colours. It gives the graphics creator a palette to use that will look the same, no matter how the user has their graphics controls set. It avoids the problem of users with screens set to 8-bit colour (256 colours) seeing a very different result from those using 16-bit, Hi-color or True-color settings. But it doesn't limit the designer to a small palette of ugly or unpredictable colours. The result is GIFs with a big colour range that look the same no matter what the colour depth of the viewing screen.
Normally there are only 216 colours available in a browser on a system set to 8-bit colour, and they're not chosen with the colour response of the human eye in mind to give a useful palette. By combining the regular web-safe colours into blocks of four or more, you can create the impression of many different colours, so far as the eye is concerned, while retaining the ability of the 216 colour palette to reproduce the effect. It's like having your cake and eating it too. The only downside is a slight granularity in the colour, if you have a sharp screen.
What the program does is quite complex. It's a filter plugin for Photoshop (or other compatible graphics editor). It consists of a range of tools to chose colours, and ways to synthesise them using the web-safe colour palette. You can compile sets of colours and save them for later use. If you select portions of a target image you can use ColorSafe to fill them with your synthetic colour.
The program is intended to run with a GIF saving process that doesn't change the palette values (see the Boxtop web site for information on this, if you're using Photoshop, for example).
The operation of the program is straight forward when you know what's going on, and the interface is clean and intuitive.
There's a good deal of information on the Boxtop web site on how to operate the program, to compensate for a lack of local helpfiles. (They say these are coming later).
ColorSafe is not a program you'll use if you just want to reduce GIFs already created (although you can apply it to existing GIFs using the lasso tool or "select colour range" control in the graphics editor). If you want a flexible palette for GIF creation that's not tied to the garish web-safe colours, but one you can rely on to look the same for all viewers (or nearly so - ignoring gamma) then you'll find this a very interesting program.
Links to information about web graphics compression, palettes and related matters of interest.
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