Bird-Doggin' the Internet ^™

A Primer on Graphics Formats

By Dr. Steve O'Neil, Micro Mo Electronics, Inc.

With the migration of an ever-larger community of engineers, writers, and specifiers to the World Wide Web, expectations of faster communications and instantaneous replies involve increasing levels of sophistication among e-business devotees. One area of this battlefield which I encounter daily is that of graphics formats which are used to move drawings, bidding packages, and product artwork via e-mail. While drawing formats such as .dwg, .dxf, STEP, and IGES are familiar to most engineering types, .bmp, gif, jpeg, eps, and a host of others have historically existed in the realm of graphic artists, printers, and publishers. Nevertheless, these formats are becoming the medium of exchange in the daily process of moving graphic information from one place on the planet to another. They are also the medium of choice for submitting art for publication, for presentations and displays, and for many training, procedural and orientation programs. Here are the very basics.

There are two general categories of graphics formats: vector-based and raster (or bit map). Vector types specify starting and ending points for a graphic and send this information to the output device which produces the end product it is most capable of achieving. Vector-based files can be scaled up or down (enlarged or reduced). Raster files are built with a given resolution comprised of a specific number of dots, or pixels, per inch. These files are fixed in size and resolution and cannot practically be enlarged or reduced from their original size. The most popular professional bitmap graphics program is PhotoShop. Vector applications include Adobe Illustrator, Corel Draw and Macromedia Freehand.

GIF: Stands for Graphic Interchange Format. A compression format developed by CompuServe using Unisys's patented LZW (Lempel-Ziv-Welch) technique, GIF files are bitmaps composed of individual pixels. Its most popular use is to store drawings and illustrations containing large areas of continuous color, maps, and drawings with text. It is limited to 8 bit images (256 colors) which means dithering is a problem when using this format for photos. It uses "lossless" compression (maintains details well) and can also be used for simple animations.

JPEG: Together with GIF, this format is the most popular for Web posting. JPEG, however, is more appropriate for photographs. It supports 24-bit color and maintains a level of detail inversely proportional with compression ("lossy" compression). It is the standard format for color transparency artwork which will be projected, put on a monitor, or backlit. This is a raster format.

TIFF: This is a Tag Image File Format which is the standard for full range black and white and color images for print ("ink on something"). The downside is that compression is "all or nothing" (LZW compressed or uncompressed). JPEGs, on the other hand, have 10 ranges of compression available to the user. This format is most popular for page layout programs. Images are degraded if compression is used. This format is best used if you need CMYK color output (for printing on a page or reflected light medium), versus RGB (color output for light projection) where the JPEG format is better. This is another raster format. TIFF (CMYK) cannot be opened by a browser, so a supplemental utility is needed in order to open CMYK files. Browsers can only open RGB files.

PDF: This is Adobe's Portable Document Format. It is becoming the standard for documentation on the Web because it allows you to download and print out letter-quality documents. It can also enlarge or reduce details for review on your monitor or as a printout. A free viewer from most software download sites is available.

EPS: Encapsulated PostScript is another format used to produce letter-quality documents. It also can be used to combine text and drawings for unified output. It is widely used in desktop publishing and as an intermediate format platform. This is another format that cannot be viewed with your browser. There is a program, however, called "Ghostscript" which will allow you to open these programs on either a Mac or PC. It will also allow you to convert them into several bitmap formats. Get the lowdown at the Ghostscript, Ghostview and Gsview site at http://www.cs.wisc.edu/~ghost/.

For graphics viewers, go to the Netscape Center: Inline Plug-ins at http://home.netscape.com/plugins/image_viewers.html. There are many for Mac, Power Mac, and PC. Formats covered include TIFF, JPEG, BMP and others. IE has a similar offering at microsoft.com. For more on various graphics formats, as well as a peek at what's on the horizon, go toTechTools' Graphics Primer at http://www.techweb.com/tools/proddesign/9807/980701graphics.html. The Graphics File Formats FAQ at http://www.cs.ruu.nl/wais/html/na-dir/graphics/fileformats-faq/.html starts you off with "General Graphics Format Questions. "Parts 2 through 4 provide detailed information on "Image Conversion and Display Programs," "Where to Get File Format Specifications," and "Tips and Tricks of the Trade" respectively. If you want to make graphics formats your life's work, there are two comprehensive sites which offer information, tutorial resources and links, chats and Q&As, and threads on individual graphics programs. i/us is at http://www.i-us.com. Universal Thread, for tracking specific programs and topics, is at http://www.universalthread.com.

Steve O'Neil can be reached on the Internet at Steveo@micromo.com

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