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
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