PNG with No Alpha Channel?
Trevor DeVore
lists at mangomultimedia.com
Wed Jun 11 10:01:19 EDT 2008
On Jun 11, 2008, at 9:50 AM, Luis wrote:
> Ok, if you look at a 32 bit png in ascii near the start of the file
> then you'll spot the bKGD chunk, this defines the background and it
> looks like it also contains the alpha value. On a 24 bit png (no
> alpha) this value is not present...
> The bKGD chunk may not be honoured in all viewers.
> I don't know how this change may reflect on the final image but it
> might be worth a shot!
The bKGD chunk can be useful for decoders that ignore transparency so
that they will display an appropriate background color. A 24-bit PNG
would have no need of setting this property since all pixels have a
known color and no transparency. I imagine this is why you don't see
it in the 24-bit PNG.
Regards,
--
Trevor DeVore
Blue Mango Learning Systems
www.bluemangolearning.com - www.screensteps.com
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