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September 2006

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2006.09.15 12:38 "alpha in Grayscale or Palette", by Anurag Singh
2006.09.15 15:49 "Re: alpha in Grayscale or Palette", by Gerben Vos
2006.09.15 17:37 "Re: alpha in Grayscale or Palette", by Bob Friesenhahn
2006.09.15 17:46 "Re: alpha in Grayscale or Palette", by Ed Grissom
2006.09.15 17:54 "Re: alpha in Grayscale or Palette", by Bob Friesenhahn
2006.09.16 20:01 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.16 20:47 "Re: alpha in Grayscale or Palette", by Bob Friesenhahn
2006.09.16 21:50 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.16 22:00 "Re: alpha in Grayscale or Palette", by Toby Thain
2006.09.16 22:18 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.16 22:20 "Re: alpha in Grayscale or Palette", by Toby Thain
2006.09.16 22:38 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.17 02:07 "Re: alpha in Grayscale or Palette", by Graeme Gill
2006.09.17 08:49 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.17 09:03 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.17 10:39 "Re: alpha in Grayscale or Palette", by Graeme Gill
2006.09.17 17:23 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.18 01:35 "Re: alpha in Grayscale or Palette", by Graeme Gill
2006.09.18 09:40 "Re: alpha in Grayscale or Palette", by Joris Van Damme
2006.09.18 14:39 "Re: alpha in Grayscale or Palette", by Gerben Vos
2006.09.16 09:58 "Re: alpha in Grayscale or Palette", by Anurag Singh
2006.09.18 11:23 "Re: alpha in Grayscale or Palette", by Gerben Vos
2006.09.18 11:06 "Re: alpha in Grayscale or Palette", by Gerben Vos

2006.09.15 17:46 "Re: alpha in Grayscale or Palette", by Ed Grissom

Gerben -  

For palette images, is an alpha channel explicitly forbidden by the spec?  

What I am thinking is an extra data plane, not an extra column in the
color table. 

Transparency and especially translucency are not always tied to the
color of a pixel (which would be the effect of the extra column in the
colortable),  rather, it is often tied to position in the image (i.e.
vignettes around the edges) 

In that case, the advice for palette images would be the same as your
advice for the greyscale images. 

-- 
ed grissom
ed.grissom@intergraph.com