Salut et bienvenu :)

Quoting Olivier Marie <[EMAIL PROTECTED]>:
> My questions are :
> How can I fill a zone with transparent color ?

First you need to add an alpha channel to your image. Then select the region you
would like to erase, and Edit->Clear.

> An erased zone (transparent) has an alpha value equal to 0. In the same
> image, others pixels can have the same index but with alpha=255. Can I have
> a specific transparent index ?

When you save the image as a GIF, this is what happens. To ensure that you have
space for an indexed palette entry, you should select a 255 colour palette
rather than a 256 color palette during indexing when you want an alpha channel.

PNG indexes differently, in that an index entry may have an alpha value from 0
to 255 associated with it, effectively allowing an RGBA palette. Unfortunately,
the GIMP doesn't really support that properly (yet?).


Dave Neary
Lyon, France
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