You can adjust the grayscale interactively in an AFNI image window using the "c" and "b" (contrast and brightness) arrows at the right edge of the image. Also, in the latest release, you can click-and-hold Button 1 in the image, then drag it around to adjust the contrast and brightness interactively. This method becomes intuitively easy to use after a couple of trials. Finally, the "g" button at the right edge of the image lets you adjust the gamma factor for the grayscale map.
You can see a graph of the mapping between data values and grayscale values by using the Button 3 popup on the intensity bar (just right of the image), and then choosing the option "Display Graymap Plot". This is kind of fun.
If you like bizarreness, you can switch from grayscale to a colorscale with the "Colr" button at the top right corner of the image viewer window.
bob cox
