AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2003.12.03 06:20 "[Tiff] Double Precision TIFF images", by Chris Cox
2004.01.23 20:30 "Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Bob Friesenhahn
2004.01.23 17:16 "Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Joris
2004.01.23 20:52 "Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Chris Cox
[...]

2004.01.23 20:52 "Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Chris Cox

On Fri, 23 Jan 2004, Chris Cox wrote:

> >
> >I am by no means an authority on the TIFF specification. My interpretation

> >of the file in question is that a sensible application should render the > >first band in greyscale and ignore the 2nd and 3rd since they are

> >extra samples
> >with no meaning attached.
>
> Or load the 2nd and 3rd channels as alpha (not transparency) channels
> -- as Photoshop does.
>

> It would be incorrect to interpret this image as RGB.

How does Photoshop treat a second alpha channel? Does it actually get used for anything?

Alpha channels are just alpha channels - they get loaded and the user can do what they want with them.

Only transparency (associated alpha) has any special meaning.

Chris