On Mar 11, 2011, at 6:46 AM, Paul M wrote: > > On 11/03/2011, at 8:00 AM, Kyle Sluder wrote: > >> On Thu, Mar 10, 2011 at 10:47 AM, Leonardo <mac.iphone....@gmail.com> wrote: >>> I forgot: if I save the TIF from Photoshop marking the check-box "Save >>> Transparency", on my App I can quite read the alpha channel, and the RGB >>> values are not pre-multiplied. That's fine. >>> Anyway, without the "Save Transparency", on my App I get the RGB values >>> pre-multiplied and the alpha values are all 1.0, so I can't calculate the >>> original RGB values. The weird point is that if I re-open this TIF file with >>> Photoshop, the half-a-transparent pixels are well visible. So the alpha >>> information has been properly stored within the TIF file, somewhere. I would >>> like to know where. >> >> Probably in a custom Photoshop chunk. >> >> TIFF isn't a very well-standardized format. Photoshop sticks a ton of >> stuff in custom chunks. > > > The spec is here: > http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf > > By not 'well-standardised', i guess you mean that some people dont conform to > the spec. > > > paulm > You might also find the custom Photoshop section here : http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm#50577413_pgfId-1039502
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