Is PNG Transparency Really a Big Deal?

The short answer is yes. The long answer is about why it’s a big deal. I’ve been searching the few available resources on PNG transparency lately and I’ve found that most of them are impossibly difficult to understand. But I’m trying. I think I’ve finally figured out why PNG transparency is so longed for, while GIF transparency is regarded as inadequate.

With IE7 about to be released, the future for PNG transparency is suddenly brighter. The possibility of IE7’s release has driven all of us to extremes of relearning, and PNG has been my interest lately.

A GIF can be transparent. True. It uses what is called index transparency. This means that a color is either completely visible (opaque) or completely invisible (transparent.) A PNG can do that, too. But it goes several steps better. A PNG also can handle alpha transparency. This means that up to 254 different colors can be set to varying degrees of transparency in a single image. You can imagine the fancy effects you could get layering a transparent PNG over a background image. Or piling up a bunch of transparent PNGs using z-index to achieve all sorts of interesting effects. Or sliding transparent PNGs over each other with a technique like the sliding doors effect.

I’m shaking my head yes, because I finally figured out what the big deal was all about. I know the great designers have already known this for a long time. Not being a great designer, I just got it. The great designers have whipped up ways to make IE5/6 work with PNG transparency, in spite of the fact that it doesn’t want to, just so they can play with this marvelous toy. Well, I’m on the bandwagon now, and I say this is a big deal!

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