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November 2005
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2005.11.03 15:53 "Re: Writing bilevel and transparent TIFFs efficiently", by Gerben Vos
Rupali Holmes wrote: > > I'm trying to write a bilevel image as a transparent TIFF. So one of > the colors is always transparent, and the other is opaque. What is the > best way to do this? I can't use G3 or G4 because the colors are not > necessarily black and white. The one option I see is to write an RGB > image with an associated alpha but that doesn't seem very efficient. > Is there a better way to do this? What type of compression should be > used? I guess it depends mostly on what is supported by the application which will receive the TIFF. One other thing you could try is to have a G3/G4 transparency mask (Photometric = 4, NewSubfileType has bit 2 set), and another image in the TIFF file containing a single coloured pixel, with the resolutions matched so that the images are the same size. However, I can't find anything in the spec about how the two images are to be associated with each other, and I doubt this format is supported widely, or at all. Gerben Vos.