LibTiff Mailing List
TIFF and LibTiff Mailing List Archive
January 2007
Previous Thread
Next Thread
Previous by Thread
Next by Thread
Previous by Date
Next by Date
Contact
The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems
Thread
2007.01.31 18:49 "Re: 16bit grayscale with colormap", by Ed Grissom
Phillip Crews wrote: > Toby Thain wrote: > > > > On 31-Jan-07, at 2:39 PM, Reinhard Mayr aka Czerwinski wrote: > > > >> Hello, > >> > >> 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? > > Or by 16 1/273 (65535/4095) to preserve white. > Or not at all if you want to use JPEG Compression which is not defined for bit depths greater than 12. Or not at all if your customers want to preserve the 'original' data (however misguided that mat be). How about using SMinSampleValue and SMaxSampleValue to provide hints to the app for choosing reasonable scaling parameters ? It is supported by about as many readers as 16 bit colortables, but at least it seems to be the right solution to the problem. (see http://www.asmail.be/msg0055257514.html for more discussion) -- ed grissom ed.grissom@intergraph.com