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tcl function: readnativeroi -- read native roi
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keyboard equivalent: none

The "R" button reads native resolution ROI from
the file in the entry to the left (tcl filename
variable=$uplabel), registers it to the struct
volume using the matrix specified by option
-regdat (typically register.dat in current
$scandir), and then upsamples it to the current
struct resolution (1mm^3/256^3 or 0.5mm^3/512^3)
for display or smoothing.

Here is the tcl code for the "R" (read) button
function, which calls the tcl-linked-C-functions,
read_native_roi and do_regupsamp_roi:

# read real or complex native stats
proc readnativeroi { } {
  global rawlabel labelflag
  setfile rawlabel [.mri.main.right.fi.roin.cbx subwidget entry get]
  read_native_roi
  do_regupsamp_roi
  set labelflag 1
  redraw
}
