Nota Bene:

You can set the environment variable AFNI_IMAGE_MINTOMAX to YES and then the min-to-max setting will be turned on by default in the image viewers.

You can set environment variable AFNI_IMAGE_GLOBALRANGE to YES to have the grayscale set to run from bottom=dataset min to top=dataset max (overriding 2%-to-98% AND min-to-max, both of which operate on a slicewise basis, not a volumewise basis).

The bad plotting in the Graymap display is because I wrote that in a hurry. A proper version would draw a better histogram, like the Histogram plugin does.

You can determine the current mapping between numerical values and grayscale by enabling hints (Datamode->Misc menu) and then putting the cursor over the grayscale bar to the right of the image subwindow.

For more information on environment variables, see the README.environment text file. You can interactively modify some variables from the Edit Environment control panel (Datamode->Misc menu, or the right-click image popup menu on recent version of AFNI). You can also set them in your ~/.afnirc file, or your shell startup file.

bob cox