The Care and Feeding of PNG
By Kevin Savetz
In 1998, Portable Network Graphics, or PNG, was gaining popularity on the Web, but keeping a low profile. At that time, it was supported by more than three dozen graphic development programs and served by approximately 2800 Web sites.
Today, PNG has moved closer to becoming a mainstream graphics format. It's supported by hundreds of graphics programs and all of the major Web browsers, and is used on more than half a million Web pages, according to AltaVista. PNG is more popular than ever. However, it still isn't a household word, even among people who work with Web graphics on a daily basis.
PNG vs. GIF and JPEG
PNG isn't a panacea for all graphics format woes, but it does offer distinct advantages compared to the Web's two mainstay graphics formats, GIF and JPEG—especially GIF. From technical and legal standpoints, PNG is superior to GIF. However, PNG won't replace JPEG. For photographic images that can tolerate loss, JPEG usually produces smaller, more easily transferrable files.
PNG produces "lossless" images—that is, images that don't lose any quality in compression. JPEG, on the other hand, is "lossy"—it throws away some image information, reducing image quality and file size. PNG supports millions of colors, transparency, and interlacing. It also has better compression than GIF. But perhaps its best quality is that PNG is an open standard.
PNG has gained popularity because of its technical advantages and freedom from pesky litigation. Unisys owns the patent to the LZW compression system used in the GIF file format, and over the years it has bullied graphics-program developers, online service providers, and even individual Web sites into paying royalties for using GIFs.
