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entry variable: $prad -- edit brush radius
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keyboard equiv Linux: <Alt-b,B>
keyboard equiv Mac: <Cmd-b,B>

Radius of white (middle-mouse) and black
(right-mouse) editing brush.  3D button toggles
between within-slice brush (default) and 3D brush
($inplaneflag=0). Brush radius=0 is 1x1x1 mm (one
pixel).  Alt-b (Mac:Cmd-b) returns radius to
this.  Increasing to radius=1 increases brush to
3x3x1 mm (or 3x3x3 if 3D button clicked), and so
on.  Alt-B (Mac:Cmd-B) increases radius by 1.
Write edited images with SAVEIMG (or "W" on the
"im:" line to Save As).

To see black edits: contr: ($bwslope) = 255
                    midpt: ($bwmid) = 0.001

Finally, to get a square/cubical brush (e.g., to
delete whole slice), click the "rad:" label to
toggle between circular/spherical and
square/cubical (toggles $circleflag).
