sigma@pawl.rpi.edu (Kevin J Martin) (09/07/90)
dclaar@hpcupt1.HP.COM (Doug Claar) writes: >I noticed that neither the PBMPLUS utilities nor the FBM utilities >handle TIFF images with grey/color response curves. Has anyone >written a TIFF to {something} converter that doesn't just grab the >raw bits? (The grey response curve indicates the actual value of each >level of grey. I believe that this is called 'gamma correction'? For >example, the actual mappings might be 0 10 50 100 for a 4 level grey image). Incidentally, can anyone explain that 'gamma factor' a little better than what I've seen in the TIFF specification? Examples would be good. And how much does it matter on 64-grayscale VGA? -- Kevin Martin ||| sigma@pawl.rpi.edu ||| usergkj1@RPITSMTS.BITNET
bdb@becker.UUCP (Bruce D. Becker) (09/10/90)
In article <TL'%YC*@rpi.edu> sigma@pawl.rpi.edu (Kevin J Martin) writes: |dclaar@hpcupt1.HP.COM (Doug Claar) writes: |>I noticed that neither the PBMPLUS utilities nor the FBM utilities |>handle TIFF images with grey/color response curves. Has anyone |>written a TIFF to {something} converter that doesn't just grab the |>raw bits? (The grey response curve indicates the actual value of each |>level of grey. I believe that this is called 'gamma correction'? For |>example, the actual mappings might be 0 10 50 100 for a 4 level grey image). | |Incidentally, can anyone explain that 'gamma factor' a little better than |what I've seen in the TIFF specification? Examples would be good. gamma refers to the fact that there is a non-linear relationship between excitation and brightness for many diplays, such as CRT's and film. Since the relationship is approximately logarithmic, gamma is an expression of the degree of the equation - for example, a gamma of 2.5 says that output brightness varies with input excitation taken to the 2.5 power. -- ,u, Bruce Becker Toronto, Ontario a /i/ Internet: bdb@becker.UUCP, bruce@gpu.utcs.toronto.edu `\o\-e UUCP: ...!uunet!mnetor!becker!bdb _< /_ "I still have my phil-os-o-phy" - Meredith Monk