The PNG image file format is not new to the web. It originally developed in the mid-90s as a solution to the shortcomings of the traditional GIF image file format. However, because early browser applications offered only spotty support for the PNG's advanced features, web designers, developers were limited in its use.



One large hurdle in particular faced by PNG's was Microsoft Internet Explorer (IE). Far and away the most popular browser, IE offered particularly poor support for the file format. However, with the release of IE 7 as well as several JavaScript hacks, this has all changed, and PNGs are more popular than ever.

But who cares!? And besides being one letter short of my favorite 1972 video game, what makes a PNG so great? Below, are three reasons why PNGs are the best image format since the Polaroid.

They’re See-Through! (Alpha Transparency):
As compared to the GIF, PNG offers a far less basic form of transparency. With GIFs, a particular color (or colors) is able to be saved as transparent, leaving colors either entirely opaque or transparent. There is no in-between.

PNGs have a distinct advantage in this area. The PNG file format supports "semi-transparent pixels," meaning a PNG can be saved with a soft drop shadow and floated over any background. It can be used as a watermark on a textured or gradiented background. It can even be smoothly faded from fully opaque to transparent, revealing the web page contents beneath.

Summerour.net features a logo which demonstrates this function. The homepage layout called for a logo with a soft drop shadow over a textured background of architectural sketches that regularly change. Using a GIF or JPG would be highly impractical, because every time the image changed, the logo’s background would need to be edited. A PNG, however, is floated over the image with a faded drop shadow, making the task quick, simple and dynamic. PNGs make the look and feel of your page flexible.

They Look Great! (Lossless Compression ):
Every time a JPEG is saved and compressed, it loses some of the original file's information and the image quality degrades. The GIF file format offers lossless compression (so the file can be saved and resaved without losing image quality), but it only supports a limited 256 color palette, making it useless for full-color photography and other such complex images.

PNG offers the best of both worlds. It displays full color photographic images, like the JPEG, but it also supports a managed color palette, like the GIF format. While the PNG will typically have a larger file size than the JPEG for photographic images, it does have a distinct advantage: its compression is lossless, meaning images never degrade in quality or suffer from "compression artifacting" which affects many JPEG images.

The results are crisper, brighter images that will “pop� on your pages unlike ever before.

They’re Self Optimizing! (Gamma Correction ):
Adjusting the brightness and contrast of images to look correct on a wide variety of monitors and operating systems is a common problem facing web designers. This problem is primarily related to different monitor Gamma settings.

Gamma is a method monitors use to distribute their luminance evenly across the display. Unfortunately, different operating systems (in particular the Mac and Windows) use different Gamma settings. So an image that is color-corrected for the Macintosh operating system may look too dark on the Windows operating system and vice-versa.

The PNG file format offers a solution for this problem. The image can be saved with built-in Gamma correction, enabling it to anticipate the operating system's Gamma settings and automatically adjust its brightness and contrast. By using a PNG, designers can simply color-correct the image for their personal operating systems and let the PNG do the rest.

This article was co-authored by Mike Bradbury and Mike Harvey. Both are employees of Objectware, Inc, an Atlanta web development and Atlanta web design company with an active branch in Washington DC. Mike Harvey is a graphic designer, with expert knowledge of web design and usability.