On Mar 10, 2011, at 12:47 PM, Leonardo 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.
TIFF file formats can include a wide range of tags, including "private use" ones that would be used by Photoshop to store whatever they want, up to, and probably including, the Ark of the Covenant (or in this case, some variation on a .psd file) But bottom line is, if you are saving the file without transparency, that is what you are getting in the publicly documented parts of the file - it would be wrong for NSImage to use those private tags to give you anything other than what the file publicly presents (i.e., attempting to reading alpha from a file that has tags declaring it to not have alpha would be non-conformant with the TIFF spec). Glenn Andreas gandr...@gandreas.com The most merciful thing in the world ... is the inability of the human mind to correlate all its contents - HPL _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
