Web Design in a Nutshell, 2nd Edition

Graphics on the Web

Print designers need to adapt their graphics production skills for the Web to take into account the peculiarities of graphics that are distributed over a network and displayed on computer monitors.

Graphics File Formats

As of this writing, nearly all the graphics that you see on the Web are in one of two formats: GIF and JPEG. A third worthy contender, the PNG file, is struggling for browser support and attention. What follows is a very brief introduction to each of these online graphic formats. More detailed descriptions are provided in the chapters dedicated to each format.

The ubiquitous GIF

The GIF (Graphic Interchange Format) file format is the traditional darling of the Web. It was the first file format to be supported by web browsers, and it continues to be the format for the vast majority of graphics on the Web today.

GIFs are indexed color files with a maximum 8-bit palette capacity, which means that a GIF can contain a maximum of 256 pixel colors. Because they compress color information by rows of pixels, GIF files are most appropriate for graphics that contain areas of flat color.

See Chapter 19 for complete information on the GIF file format.

The handy JPEG

The second most popular graphics format on the Web today is the JPEG ( Joint Photographic Experts Group) format. JPEGs contain 24-bit color information—that’s millions of colors, as opposed to GIF’s 256. They use what is called a “lossy” compression scheme, which means that some image information ...