AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Daniel Glen
May 07, 2015 06:06PM
Hi Filip,

Thanks for being a great host in Tubingen. AFNI doesn't allow saving those values because the operation happens in the rendering of the RGB display values. If you get the source code, you can see this in imseq.c. The gamma value calculation occurs after the range selection, LUT mapping, and then brightness and contrast computations. Still you can do something like this yourself with a simple 3dcalc command.


1dcount -digits 1 1 100 > i0.1D
1deval -a i0.1D\' -expr '100*(a/100)^0.5' | 1dplot -stdin

You would have to scale by the maximum and set the gamma value to what you want.

set gamma = 2.0
set max = `3dBrickStat -max -slow $dset`
3dcalc -a $dset -prefix $outdset -expr "$max*(a/$max)^$gamma"
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Subject Author Posted

Gamma correction - intensity value change ?

Filip Sobczak May 07, 2015 08:34AM

Re: Gamma correction - intensity value change ?

Daniel Glen May 07, 2015 06:06PM

Re: Gamma correction - intensity value change ?

Filip Sobczak May 08, 2015 10:52AM