2008.04.18 12:53 "Re: [Tiff] a question about creating transparency of the image in TIFF", by Edward Lam
Also, the TIFF spec. states that images with associated alpha (transparency) must be premultiplied.
The TIFF specification does not prevent a colormapped file with transparency but the colors in the colormap would then need to be premultiplied, which could be a challenge to surmount. As a result, no one does this.
Sorry, I don't understand this. We output TIFFs with premultiplied RGB colors and associated alpha. How is this a "challenge"?