On Fri, Apr 07, 2000 at 06:27:27AM +0100, Nick Lamb wrote:
> Instead, I propose to change Export to recommend "Flatten" when it
> notices that the bottom layer has no alpha channel AND is visible,
> when it would current recommend "Merge Visible".
> This will improve compression ratios for PNG, TGA etc., as well as
> increasing available colors for GIF and colormapped PNG.
I have made the changes you proposed (only in my tree) and I think they
should go into CVS. However the current system makes it difficult to
get a background layer w/o alpha-channel. The only way you end up with
a non-alpha background is by creating the image from ground up. As soon
as you add the background layer later (which is something I do frequently),
it will be added with alpha-channel. What we'd really need is a way to 
determine if the composition contains pixels with transparency. That would
however be a lot more complicated (especially doing it in libgimp). 

The export facility was never meant to produce the optimal result, but 
should give people a way to save to any format quickly without loosing 
too much information (like whole layers...). However, the changes Nick
proposes are simple and decrease filesize in some cases, so I'd say we
go for it.

Salut, Sven

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