Page 12      Diablo Blue      May, 2001

(Continued from page 11)

graphics. It  supports 24 bits of color information, and is most commonly used for photographs and similar continuous-tone bitmap images. The JPEG file format stores all of the color information in an RGB image, then reduces the file size by compressing it, or saving only the color information that is essential to the image. Most imaging applications and plug-ins let you determine the amount of compression used when saving a graphic in the JPEG format. Unlike GIF, JPEG does not support transparency.
Use JPEG for scanned photographs and naturalistic artwork with highlights, shaded areas, and shadows. The more complex and subtly rendered the image is, the more likely it is that the image should be converted to JPEG. JPEG, like GIF, uses a "lossy" compression technique, which changes the original image by removing color information during the conversion process. The JPEG file format supports millions of colors. In theory, JPEG was designed so that changes made to the original image during conversion to JPEG would not be visible to the human eye. Most imaging applications let the user control the amount of lossy compression performed on an image, so you can trade off image quality for smaller file size and vice versa. Be aware that the chances of image degradation when converting to JPEG increase proportionally with the amount of compression you use. When saving a file in the JPEG format,  add the"*.jpg" file extension to the end of its file name. Use the JPEG file format for images with only a few distinct colors, such as illustrations, cartoons, and images with blocks of color, such as icons, buttons, and horizontal rules.
PICT: The Picture file format is for use primarily on the Macintosh platform; it is the default format for Macintosh image files. The PICT format is most commonly used for bitmap images, but can be used for vector images as well. Avoid using PICT images for print publishing. The PICT format is "lossless," meaning it does not remove information from the original image during the file format conversion process. Because the PICT format supports only limited compression on Macintoshes with QuickTime installed, PICT files are usually large. When saving an image as a PICT, add the file extension ".pct" to the end of its file name. Use the PICT format for images used in video editing, animation, desktop computer presentations, and multimedia authoring.
PNG: The Portable Network Graphics format will likely be the successor to the GIF file format. PNG is not yet widely supported by most Web browsers. Netscape versions 4.04 and later, and Internet Explorer version 4.01 and later, currently support this file format. However, PNG is expected to become a mainstream format for Web images and could replace GIF entirely. It is platform independent and should be used for single images only (not animation.) Compared with GIF, PNG offers greater color support and better compression, gamma correction for brightness control across platforms, better support for transparency, and a better method for displaying progressive images. When saving an image to the PNG format, add the file extension ".png" to the end of its file name.
CGM: The Computer Graphics Metafile is a format developed by several standards organizations.  CGM is supported by many PC Software products. When saving an image to the CGM format, add the file extension ".cgm" to the end of its file name.
DXF: The Data Exchange File is a format developed by Autodesk. Almost all PC-based CAD systems support DXF.
GEM: The graphics file format used by GEM-based applications. GEM is a graphical user interface (GUI) developed by Digital Research.
HPGL: Hewlett-Packard Graphics Language is one of the oldest file formats. Although it is not very sophisticated, it is supported by many PC-based graphics products.
IGES: Initial Graphics Exchange Specification is an ANSI Standard for three-dimensional wire frame models. IGES is supported by most PC-based CAD systems.
PIC: This is a relatively simple file format developed by Lotus for representing graphs generated by Lotus 1-2-3. PIC is supported by a wide variety of PC applications.
PICT: Developed by Apple Computer in 1984 as the standard format for storing and exchanging graphics files. It is supported by all graphics programs that run on a Macintosh.
WMF: The Windows file format is used for exchanging graphics between Microsoft Windows applications. WMF files can also hold bit-mapped images.
The debate over which format is better still surfaces once in a while. My opinion is that each format has its place, just as the native format of the various paint-and-draw programs. One format may be better than others in terms of quality; at other times, another format may be better in terms of size. Best way is to take the time to view and store your images in different formats and select the one optimum for your needs, storage capability, and ease of use.