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January 2007
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2007.01.31 17:06 "Re: 16bit grayscale with colormap", by Bob Friesenhahn
On Wed, 31 Jan 2007, Toby Thain wrote: >> >> 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 ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/