Image Processing

Creating Reliable Web Graphics

You need to design your graphics to be viewable on lots of different computers, with lots of different display characteristicss -- not everyone has a display capable of millions of colors (in fact we don't in this presentation) so you must design your graphics to allow for this fact. Most computers can only display 256 different colors, a tight limit that requires planning to use effectively.

The general rules are:

1. For icons, use as few colors as possible -- This makes the image files as small as possible, and frees colors for other images.
2. Don't waste colors -- If you use a color in the background or an icon, try and reuse it in another icon or image.
3. Use sufficient text contrast-- Make sure, if you use a background image or color, that the text is still easy to read against this background.
4. To avoid color substitution, or color dithering -- Use the Windows default colormap when you create the images. This is the default set of colors supported by Microsoft and many other systems,
5. Test - test - test -- Test your documents on several different browsers, to make sure they look as intended.