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Re: CSS Opacity

From: David Hyatt <hyatt@apple.com>
Date: Sat, 28 Apr 2007 20:54:13 -0700
Message-Id: <44FFAF93-0A40-4E36-80BD-328C094F031F@apple.com>
Cc: www-style@w3.org
To: Daniel Beardsmore <public@telcontar.net>

Sure, but using opacity is much worse, since you'll force the Web  
engine to make an offscreen buffer to render the image into before  
then blending it with the destination.  One transparent image buffer  
from a PNG is going to be way more efficient than having a non- 
transparent image buffer + an entire offscreen buffer just to do the  
blend.

dave
(hyatt@apple.com)

On Apr 28, 2007, at 8:45 PM, Daniel Beardsmore wrote:

> Yes, this is what I tried to do. I suppose that now that IE 7  
> supports RGBA PNG, there is no excuse for CSS to work around it. My  
> only objection is that PNG isn't very efficient on continuous-tone  
> images and the alpha channel bloats the format more. (The Web image  
> formats leave so much to be desired. Imagine, for example, if you  
> could assign multiple GIF image colours to varying transparency  
> levels to get, say, 250 colours plus alpha in a mere 8 bpp for logo  
> edge anti-aliasing? Or DCT lossless alpha channels on JPEGs, or all  
> sorts :)
>
Received on Sunday, 29 April 2007 03:54:15 GMT

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