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April 2008
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2008.04.17 21:14 "Re: a question about creating transparency of the image in TIFF", by Chris Cox
There are 2 types of alpha in TIFF: associated (transparency) and unassociated (undefined extra channels). Also, the TIFF spec. states that images with associated alpha (transparency) must be premultiplied. Chris On 4/17/08 8:18 AM, "Gerben Vos" <Gerben@zylab.com> wrote: >> Константин Луцкий wrote: >>> Hi. Can anyone help me ? How can I create transparency of the image in >>> TIFF? > > Frank Warmerdam wrote: >> The conventional approach is to create an alpha sample for each pixel, and >> set it to indicate transparent pixels. > > For example, for RGB images (PhotometricInterpretation = 2) you can set > SamplesPerPixel to 4, and then indicate in the ExtraSamples tag that the > extra (fourth) sample is an alpha channel. Read the TIFF specification for > more info. > > Gerben Vos. > > _______________________________________________ > Tiff mailing list: Tiff@lists.maptools.org > http://lists.maptools.org/mailman/listinfo/tiff > http://www.remotesensing.org/libtiff/