Graphics on the Web

Image Dithering

Image dithering occurs when a browser on a 256-color computer can not display a color that is not in its color palette and it tries to approximate the color with available colors. Dithering makes an image appear speckled.
 
Original (24 bit, millions of colors)   Dithered (as seen on a 256-color computer)
Original Image   Dithered Image
 

The dithered image is a screen shot of the original image as viewed in Netscape on a PC with the color depth set to 256 colors.

To avoid dithering, create graphics using colors that are contained in the Web-safe color palette. Also be conscious of the effect that dithering may have on photographs you place on your Web pages.

Note: In most cases, reducing the colors in a 24-bit photo to the Web-safe palette will not give you a usable image.

Graphics Checklist