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Mark Rogers wrote:
Bill Hill wrote:
Replace "output.jpg" with "-transparent #FFE000 output.gif" (Might be -transparent-color ???) Where #RRGGBB is the same as the background.
Think it's -transparency
What I don't want to do is change any part of the existing image, though, just make sure the surrounding area created by extending the canvas is transparent.
GIF transparency is supported by stealing one of the available palette entries (IIRC), out of the up-to 256 available. Therefore, I used to set the "background" to some hideous colour (like a lime green or bright purple) which was unlikely to occur in the rest of the image, and set that to to be the transparent colour.
If you convert to PNG, this isn't an issue as it supports proper alpha channels (i.e. variable opacity) thus transparency is simply a pixel of any colour with an alpha-value of 0x00, rather than one of its palette members being assigned "transparent" (or something vaguely like that).
Cheers, Simon
- -- - --------------------------------------------------------------------- Simon Ransome http://nosher.net
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