The PNG (Portable Network Graphics) format was designed to succeed GIF formatted images. This losslessy format does not require a patent license for use, unlike the GIF format. There are many programs available, some free, that can view, manage and edit .PNG image files. Whether you want a simple viewer or something that can edit your PNG images in any way you can imagine, there are PNG reading programs to suit everybody.
Along with a huge list of other features, PhotoShop can view and edit .PNG files. In April 2010 you could buy the full-featured Adobe PhotoShop CS4 for around $700. While the price is obviously pretty high, Adobe also offers PhotoShop Elements 8 for anywhere from $50 to $100, depending on where you buy. Elements isn't as feature-rich as CS4, but it is designed more for the home user, whereas CS4 is more useful for graphic designers and editors.
If you want a simple, free and reliable program with the ability to read multiple image file formats, including PNG, check out IrfanView. IrfanView offers all the basic features you'd expect from a compact, free image viewer such as basic editing, email and printing options. IrfanView's available plug-ins help make it a well-rounded program by adding much more file support and integrating the program better with Windows and other common programs. There are even audio and video plug-ins to allow IrfanView to play MP3, AVI, MPEG, MOV and other audio and video formats.
According to its website, GIMP is a free program designed to retouch, create and author photos. With support for Windows and Mac, one of the many things GIMP can do is read and edit .PNG files. With easily over 100 available user-created plug-ins, GIMP is also highly customizable. Most of the plug-ins for GIMP allow for new editing effects, but others add more file and program support.
Photo Pos Pro
Another freeware offering, Photo Pos Pro is a powerful image editing program that provides a free alternative to Adobe's PhotoShop software. According to CNET.com, Photo Pos Pro is a feature-rich program made for the professional image editors and graphic artists. CNET also highly recommends reading the tutorials if you plan on using Photo Pos Pro for more than just a PNG viewer. With a CNET editors rating of five out of five stars, Photo Pos Pro may be worth checking out.
FastStone Image Viewer
Another five star rated program from the editors at CNET.com, FastStone Image Viewer is yet another free image viewer and editor. Obviously capable of reading and edit PNG image files, FastStone can also batch-convert PNG and other image files. According to CNET, FastStone doesn't offer all of the advanced bells and whistles of PhotoShop, but still offers your basic photo editing tools. With a number of available skins, you can even customize FastStone's user interface to suit your style.