Creating PNG Files 297PNGCreating PNG FilesWeb Design in a Nutshell, eMatter Editionthe Color Table, adding transparency to an 8-bit PNG does not significantly
increase its file size.
Embedded Text
PNGs also have the ability to store strings of text. This is useful in permanently
attaching text to an image, such as a description of what is in the image or copy-
right information. Unfortunately, this is another one of PNG’s finer capabilities that
is not supported by creation tools nor browsers.
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, seehttp://www.cdrom.com/pub/png/pngapps.html.
Figure 16-1: Variable transparency allows PNGs to blend with background
patterns
Table 16-2: Graphics Applications that Support PNG Format
(as of October, 1998)
Application Read/WriteCompressionFilter OptionsAlpha-ChannelTransparency8-bitTransparencyGammaCorrection
Adobe Photoshop 4.0/5.0^1 XXX——
PaintShopPro 4.0^2 X—X——
Adobe ImageReady 1.0 X — X X X
Macromedia Fireworks 1.0^3 X—XX—
Macromedia Freehand 7.0^4 and higher X — X — —