da - Define an area of an image
da po:[20,20 -20,20 -20,-20 20,-20] an:1 Area 1 is a square with 40
arcmin sides centered on the origin
da p: List the vertices of area 1.
ro "areas.da";da an:1 p:;da an:3 p: List the vertices of areas 1 and 3
in the file areas.da in a form for comb to
ri "areas.da" Re-define areas 1 and 3 from the listing
in the file areas.da. The area number is
in the file. Ths file could, of course,
have been edited using your favorite editor.
da cr: Define area 1 using the cursor on a graphics
display. If you are using a 5620 with a
TEK4014 window see the note below.
da po:[20,20 -20,20 -20,-20 20,-20 .DR,.DR 2,2 -2,2 -2,-2 2,-2] an:2
Area 2 is a square with 40 arcmin sides centered
on the origin with a 4 arcmin hole in the
cp ;da pl: lt:0 Make a contour plot of 'old' image and overlay
an outline of area 1, using a dotted line.
Da defines the vertices of a polygonal area. The coordinates are given
in current offset units. The vertices may be given as either numbers or with a
graphics cursor (see note). When using the cursor, move the cursor to
each vertex in turn and hit the space bar for all but the last vertex.
The last vertex is indicated using the special character
(e) which you will be told about when the cursor comes on.
The area is closed with a line from the last vertex
back to the first. A vertex with x = .DR ends the current sequence
(automatic closure), allowing a second separate part of the area. If
sub areas are nested, points which can be reached with an odd number of
boundary crossings from the outside are inside the area and others
outside. An area is needed in sp and vm to delineate the area of
interest. The maximum number of areas which can be defined is 10 (0 thru 9).
When using the cursor in an xterm window it is necessary to type return
after either space or e so that xterm will pass the character on to comb.
I haven't found any way to adjust xterm so that it behaves like a real
tek4014 in this regard.
NOTE FOR 5620 USERS (or other users of a separate graphics window): If
you want to use the graphics cursor in a tek4014 window on a 5620, you
should run 'sleep 1000000' IN THE TEK4014 WINDOW. This keeps the shell
from getting some of the characters which comb needs when reading the
cursor value, (at least for 1000000 seconds). I have found that if I
forget to run sleep and try to read the cursor, I usually have to
delete the window, reload tek4014, and restart comb to get
To use the cursor in a tek4014 window you must first click the
mouse to select that window, then move the mouse cursor to a vertex and
click button 1 again to move the crosshairs to that spot. Then hit the
space bar (or 'e'). At the end of that sequence you will have to click
the mouse on the comb window to get in touch with comb again.
This document was last updated on
Tue Oct 17 16:24:05 EDT 2000
by Marc W. Pound.