Web Design in a Nutshell

Creating PNG Files

The good news is that there are quite a few tools out there for both PCs and Macs that can save files in PNG format. The bad news is that a precious few support special features such as alpha channel transparency or gamma correction (and even then, it’s a struggle finding a browser to view them). Furthermore, some programs that create PNG files do not compress them as well as they could (including Adobe Photoshop 4.0 and PaintShop Pro).

Table 16.2 lists PNG feature support in a number of popular graphics tools. For a more comprehensive list of image editing tools and graphics file converters that support PNG compression, see http://www.cdrom.com/pub/png/pngapps.html.

Table 16-2. Graphics Applications that Support PNG Format (as of October, 1998)

Application	Read/Write	Compression Filter Options	Alpha-Channel Transparency	8-bit Transparency	Gamma Correction
Adobe Photoshop 4.0/5.0[a]	X	X	X	—	—
PaintShopPro 4.0[b]	X	—	X	—	—
Adobe ImageReady 1.0	X	—	X	X	X
Macromedia Fireworks 1.0[c]	X	—	X	X	—
Macromedia Freehand 7.0[d] and higher	X	—	X	—	—
Adobe Illustrator 7.0 and higher	X	—	—	—	—
CorelDRAW	X	—	—	—	—
[a] Photoshop’s inclusion of individual filter options is not necessarily a beneficial feature, since only two are useful and the rest are confusing. Photoshop stores both gamma and chrominance information, although gamma is only correct in 4.0 if the ambient is “medium”; in 5.0, gamma is reportedly always incorrect. ...