2007.01.31 16:39 "[Tiff] 16bit grayscale with colormap", by Reinhard Mayr aka Czerwinski

2007.01.31 17:06 "Re: [Tiff] 16bit grayscale with colormap", by Bob Friesenhahn

I deal with 16bit grayscale TIFFs. The files originate from a 12bit CCD, so the linear conversion 16bit->8bit turns my image almost black.

Maybe I'm missing something, but why don't you just multiply by 16 before storing in TIFF?

It is worth mentioning that some companies dealing with these 12bit CCDs write TIFFs using 12-bit samples. This is pretty rare in TIFF but seems acceptable if you have control over the reader. I have been provided with a number of sample files. GraphicsMagick 1.2 can read/write them.

Converting from 16-bits (or 12-bits) to 8 bits is very bad since even though the image may appear 'black' upon initial viewing, there is actually far more detail in the image than could be represented in 8 bits and converting to fewer bits loses the original levels (which may have some scientific value).

Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/