Web Design in a Nutshell

Creating JPEGs

Because JPEG is a standard file format, it is supported by all the popular graphics tools. Adobe Photoshop, JASC Paint Shop Pro, Adobe ImageReady, and Macromedia Fireworks all provide similar options for saving JPEGs.

Each tool provides sliders for controlling quality/compression ratios, although they use different numbering systems. Adobe products use a 0-10 compression scale, with the lowest setting corresponding to around 30 on the standard scale of 1-100. Paint Shop Pro uses a scale from 1 to 100; however, it works as the inverse of the standard scale with lower numbers corresponding to higher image quality and less compression. Fireworks uses a percentage value from 1 to 100%.

All of these products provide the ability to save images in Progressive JPEG format with a checkbox control. Special features for optimizing JPEGs for web delivery are discussed in Section 15.7.

There are also plug-in utilities especially for JPEG creation, such as ProJPEG from Boxtop Software (http://www.boxtopsoft.com/) and HVS JPEG 2.1 from Digital Frontiers (http://www.digfrontiers.com/). These plug-ins work with all of the programs mentioned here and are discussed further in the following section.

Regardless of the tool you use, the following guidelines apply:

• Make sure your file is in RGB or grayscale format. You can apply JPEG compression to CMYK files in some applications, but these files are not compatible with web browsers.

• If you are working in Adobe Photoshop, whether with ...