Provided by: libfuntools-dev_1.4.7-2_amd64 
NAME
RegGeometry - Geometric Shapes in Spatial Region Filtering
SYNOPSIS
This document describes the geometry of regions available for spatial filtering in
IRAF/PROS analysis.
DESCRIPTION
Geometric shapes
Several geometric shapes are used to describe regions. The valid shapes are:
shape: arguments:
----- ----------------------------------------
ANNULUS xcenter ycenter inner_radius outer_radius
BOX xcenter ycenter xwidth yheight (angle)
CIRCLE xcenter ycenter radius
ELLIPSE xcenter ycenter xwidth yheight (angle)
FIELD none
LINE x1 y1 x2 y2
PIE xcenter ycenter angle1 angle2
POINT x1 y1
POLYGON x1 y1 x2 y2 ... xn yn
All arguments are real values; integer values are automatically converted to real where
necessary. All angles are in degrees and specify angles that run counter-clockwise from
the positive y-axis.
Shapes can be specified using "command" syntax:
[shape] arg1 arg2 ...
or using "routine" syntax:
[shape](arg1, arg2, ...)
or by any combination of the these. (Of course, the parentheses must balance and there
cannot be more commas than necessary.) The shape keywords are case-insensitive.
Furthermore, any shape can be specified by a three-character unique abbreviation. For
example, one can specify three circular regions as:
"foo.fits[CIRCLE 512 512 50;CIR(128 128, 10);cir(650,650,20)]"
(Quotes generally are required to protect the region descriptor from being processed by
the Unix shell.)
The annulus shape specifies annuli, centered at xcenter, ycenter, with inner and
outer radii (r1, r2). For example,
ANNULUS 25 25 5 10
specifies an annulus centered at 25.0 25.0 with an inner radius of 5.0 and an outer radius
of 10. Assuming (as will be done for all examples in this document, unless otherwise
noted) this shape is used in a mask of size 40x40, it will look like this:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:....................111111111...........
33:...................11111111111..........
32:.................111111111111111........
31:.................111111111111111........
30:................11111111111111111.......
29:...............1111111.....1111111......
28:...............111111.......111111......
27:...............11111.........11111......
26:...............11111.........11111......
25:...............11111.........11111......
24:...............11111.........11111......
23:...............11111.........11111......
22:...............111111.......111111......
21:...............1111111.....1111111......
20:................11111111111111111.......
19:.................111111111111111........
18:.................111111111111111........
17:...................11111111111..........
16:....................111111111...........
15:........................................
14:........................................
13:........................................
12:........................................
11:........................................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The box shape specifies an orthogonally oriented box, centered at xcenter, ycenter, of
size xwidth, yheight. It requires four arguments and accepts an optional fifth argument to
specify a rotation angle. When the rotation angle is specified (in degrees), the box is
rotated by an angle that runs counter-clockwise from the positive y-axis.
The box shape specifies a rotated box, centered at xcenter, ycenter, of size xwidth,
yheight. The box is rotated by an angle specified in degrees that runs counter-clockwise
from the positive y-axis. If the angle argument is omitted, it defaults to 0.
The circle shape specifies a circle, centered at xcenter, ycenter, of radius r. It
requires three arguments.
The ellipse shape specifies an ellipse, centered at xcenter, ycenter, with y-axis width a
and the y-axis length b defined such that:
x**2/a**2 + y**2/b**2 = 1
Note that a can be less than, equal to, or greater than b. The ellipse is rotated the
specified number of degrees. The rotation is done according to astronomical convention,
counter-clockwise from the positive y-axis. An ellipse defined by:
ELLIPSE 20 20 5 10 45
will look like this:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:........................................
33:........................................
32:........................................
31:........................................
30:........................................
29:........................................
28:........................................
27:............111111......................
26:............11111111....................
25:............111111111...................
24:............11111111111.................
23:............111111111111................
22:............111111111111................
21:.............111111111111...............
20:.............1111111111111..............
19:..............111111111111..............
18:...............111111111111.............
17:...............111111111111.............
16:................11111111111.............
15:..................111111111.............
14:...................11111111.............
13:.....................111111.............
12:........................................
11:........................................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The field shape specifies the entire field as a region. It is not usually specified
explicitly, but is used implicitly in the case where no regions are specified, that is, in
cases where either a null string or some abbreviation of the string "none" is input.
Field takes no arguments.
The pie shape specifies an angular wedge of the entire field, centered at xcenter,
ycenter. The wedge runs between the two specified angles. The angles are given in
degrees, running counter-clockwise from the positive x-axis. For example,
PIE 20 20 90 180
defines a region from 90 degrees to 180 degrees, i.e., quadrant 2 of the Cartesian plane.
The display of such a region looks like this:
1234567890123456789012345678901234567890
----------------------------------------
40:11111111111111111111....................
39:11111111111111111111....................
38:11111111111111111111....................
37:11111111111111111111....................
36:11111111111111111111....................
35:11111111111111111111....................
34:11111111111111111111....................
33:11111111111111111111....................
32:11111111111111111111....................
31:11111111111111111111....................
30:11111111111111111111....................
29:11111111111111111111....................
28:11111111111111111111....................
27:11111111111111111111....................
26:11111111111111111111....................
25:11111111111111111111....................
24:11111111111111111111....................
23:11111111111111111111....................
22:11111111111111111111....................
21:11111111111111111111....................
20:........................................
19:........................................
18:........................................
17:........................................
16:........................................
15:........................................
14:........................................
13:........................................
12:........................................
11:........................................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The pie slice specified is always a counter-clockwise sweep between the angles, starting
at the first angle and ending at the second. Thus:
PIE 10 15 30 60
describes a 30 degree sweep from 2 o'clock to 1 o'clock, while:
PIE 10 15 60 30
describes a 330 degree counter-clockwise sweep from 1 o'clock to 2 o'clock passing through
12 o'clock (0 degrees). Note in both of these examples that the center of the slice can be
anywhere on the plane. The second mask looks like this:
1234567890123456789012345678901234567890
----------------------------------------
40:111111111111111111111111................
39:11111111111111111111111.................
38:11111111111111111111111.................
37:1111111111111111111111..................
36:1111111111111111111111..................
35:111111111111111111111...................
34:11111111111111111111....................
33:11111111111111111111....................
32:1111111111111111111....................1
31:1111111111111111111..................111
30:111111111111111111.................11111
29:111111111111111111................111111
28:11111111111111111...............11111111
27:1111111111111111..............1111111111
26:1111111111111111.............11111111111
25:111111111111111............1111111111111
24:111111111111111..........111111111111111
23:11111111111111.........11111111111111111
22:11111111111111........111111111111111111
21:1111111111111.......11111111111111111111
20:111111111111......1111111111111111111111
19:111111111111....111111111111111111111111
18:11111111111....1111111111111111111111111
17:11111111111..111111111111111111111111111
16:1111111111.11111111111111111111111111111
15:1111111111111111111111111111111111111111
14:1111111111111111111111111111111111111111
13:1111111111111111111111111111111111111111
12:1111111111111111111111111111111111111111
11:1111111111111111111111111111111111111111
10:1111111111111111111111111111111111111111
9:1111111111111111111111111111111111111111
8:1111111111111111111111111111111111111111
7:1111111111111111111111111111111111111111
6:1111111111111111111111111111111111111111
5:1111111111111111111111111111111111111111
4:1111111111111111111111111111111111111111
3:1111111111111111111111111111111111111111
2:1111111111111111111111111111111111111111
1:1111111111111111111111111111111111111111
The pie slice goes to the edge of the field. To limit its scope, pie usually is is
combined with other shapes, such as circles and annuli, using boolean operations. (See
below and in "help regalgebra").
Pie Performance Notes:
Pie region processing time is proportional to the size of the image, and not the size of
the region. This is because the pie shape is the only infinite length shape, and we
essentially must check all y rows for inclusion (unlike other regions, where the y limits
can be calculated beforehand). Thus, pie can run very slowly on large images. In
particular, it will run MUCH more slowly than the panda shape in image-based region
operations (such as funcnts). We recommend use of panda over pie where ever possible.
If you must use pie, always try to put it last in a boolean && expression. The reason for
this is that the filter code is optimized to exit as soon as the result is know. Since pie
is the slowest region, it is better to avoid executing it if another region can decide the
result. Consider, for example, the difference in time required to process a Chandra ACIS
file when a pie and circle are combined in two different orders:
time ./funcnts nacis.fits "circle 4096 4096 100 && pie 4096 4096 10 78"
2.87u 0.38s 0:35.08 9.2%
time ./funcnts nacis.fits "pie 4096 4096 10 78 && circle 4096 4096 100 "
89.73u 0.36s 1:03.50 141.8%
Black-magic performance note:
Panda region processing uses a quick test pie region instead of the normal pie region when
combining its annulus and pie shapes. This qtpie shape differs from the normal pie in that
it utilizes the y limits from the previous region with which it is combined. In a panda
shape, which is a series of annuli combined with pies, the processing time is thus reduced
to that of the annuli.
You can use the qtpie shape instead of pie in cases where you are combining pie with
another shape using the && operator. This will cause the pie limits to be set using limits
from the other shape, and will speed up the processing considerably. For example, the
above execution of funcnts can be improved considerably using this technique:
time ./funcnts nacis.fits "circle 4096 4096 100 && qtpie 4096 4096 10 78"
4.66u 0.33s 0:05.87 85.0%
We emphasize that this is a quasi-documented feature and might change in the future. The
qtpie shape is not recognized by ds9 or other programs.
The line shape allows single pixels in a line between (x1,y1) and (x2,y2) to be included
or excluded. For example:
LINE (5,6, 24,25)
displays as:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:........................................
33:........................................
32:........................................
31:........................................
30:........................................
29:........................................
28:........................................
27:........................................
26:........................................
25:.......................1................
24:......................1.................
23:.....................1..................
22:....................1...................
21:...................1....................
20:..................1.....................
19:.................1......................
18:................1.......................
17:...............1........................
16:..............1.........................
15:.............1..........................
14:............1...........................
13:...........1............................
12:..........1.............................
11:.........1..............................
10:........1...............................
9:.......1................................
8:......1.................................
7:.....1..................................
6:....1...................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The point shape allows single pixels to be included or excluded. Although the (x,y)
values are real numbers, they are truncated to integer and the corresponding pixel is
included or excluded, as specified.
Several points can be put in one region declaration; unlike the original IRAF
implementation, each now is given a different region mask value. This makes it easier,
for example, for funcnts to determine the number of photons in the individual pixels. For
example,
POINT (5,6, 10,11, 20,20, 35,30)
will give the different region mask values to all four points, as shown below:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:........................................
33:........................................
32:........................................
31:........................................
30:..................................4.....
29:........................................
28:........................................
27:........................................
26:........................................
25:........................................
24:........................................
23:........................................
22:........................................
21:........................................
20:...................3....................
19:........................................
18:........................................
17:........................................
16:........................................
15:........................................
14:........................................
13:........................................
12:........................................
11:.........2..............................
10:........................................
9:........................................
8:........................................
7:........................................
6:....1...................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The polygon shape specifies a polygon with vertices (x1, y1) ... (xn, yn). The polygon is
closed automatically: one should not specify the last vertex to be the same as the first.
Any number of vertices are allowed. For example, the following polygon defines a right
triangle as shown below:
POLYGON (10,10, 10,30, 30,30)
looks like this:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:........................................
33:........................................
32:........................................
31:........................................
30:..........11111111111111111111..........
29:..........1111111111111111111...........
28:..........111111111111111111............
27:..........11111111111111111.............
26:..........1111111111111111..............
25:..........111111111111111...............
24:..........11111111111111................
23:..........1111111111111.................
22:..........111111111111..................
21:..........11111111111...................
20:..........1111111111....................
19:..........111111111.....................
18:..........11111111......................
17:..........1111111.......................
16:..........111111........................
15:..........11111.........................
14:..........1111..........................
13:..........111...........................
12:..........11............................
11:..........1.............................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
Note that polygons can get twisted upon themselves if edge lines cross. Thus:
POL (10,10, 20,20, 20,10, 10,20)
will produce an area which is two triangles, like butterfly wings, as shown below:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:........................................
33:........................................
32:........................................
31:........................................
30:........................................
29:........................................
28:........................................
27:........................................
26:........................................
25:........................................
24:........................................
23:........................................
22:........................................
21:........................................
20:........................................
19:..........1........1....................
18:..........11......11....................
17:..........111....111....................
16:..........1111..1111....................
15:..........1111111111....................
14:..........1111..1111....................
13:..........111....111....................
12:..........11......11....................
11:..........1........1....................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
The following are combinations of pie with different shapes (called "panda" for "Pie AND
Annulus") allow for easy specification of radial sections:
shape: arguments:
----- ---------
PANDA xcen ycen ang1 ang2 nang irad orad nrad # circular
CPANDA xcen ycen ang1 ang2 nang irad orad nrad # circular
BPANDA xcen ycen ang1 ang2 nang xwlo yhlo xwhi yhhi nrad (ang) # box
EPANDA xcen ycen ang1 ang2 nang xwlo yhlo xwhi yhhi nrad (ang) # ellipse
The panda (Pies AND Annuli) shape can be used to create combinations of pie and annuli
markers. It is analogous to a Cartesian product on those shapes, i.e., the result is
several shapes generated by performing a boolean AND between pies and annuli. Thus, the
panda and cpanda specify combinations of annulus and circle with pie, respectively and
give identical results. The bpanda combines box and pie, while epanda combines ellipse and
pie.
Consider the example shown below:
PANDA(20,20, 0,360,3, 0,15,4)
Here, 3 pie slices centered at 20, 20 are combined with 4 annuli, also centered at 20, 20.
The result is a mask with 12 regions (displayed in base 16 to save characters):
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:..............44444444444...............
33:............444444444444444.............
32:...........88444444444444444............
31:.........888844443333344444444..........
30:........88888833333333333444444.........
29:........88888733333333333344444.........
28:.......8888877733333333333344444........
27:......888887777332222233333344444.......
26:......888877777622222222333334444.......
25:.....88887777766622222222333334444......
24:.....88887777666622222222233334444......
23:.....88887777666651111222233334444......
22:.....88877776666551111122223333444......
21:.....88877776666555111122223333444......
20:.....888777766665559999aaaabbbbccc......
19:.....888777766665559999aaaabbbbccc......
18:.....888777766665599999aaaabbbbccc......
17:.....88887777666659999aaaabbbbcccc......
16:.....888877776666aaaaaaaaabbbbcccc......
15:.....888877777666aaaaaaaabbbbbcccc......
14:......8888777776aaaaaaaabbbbbcccc.......
13:......888887777bbaaaaabbbbbbccccc.......
12:.......88888777bbbbbbbbbbbbccccc........
11:........888887bbbbbbbbbbbbccccc.........
10:........888888bbbbbbbbbbbcccccc.........
9:.........8888ccccbbbbbcccccccc..........
8:...........88ccccccccccccccc............
7:............ccccccccccccccc.............
6:..............ccccccccccc...............
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
Several regions with different mask values can be combined in the same mask. This
supports comparing data from the different regions. (For information on how to combine
different shapes into a single region, see "help regalgebra".) For example, consider the
following set of regions:
ANNULUS 25 25 5 10
ELLIPSE 20 20 5 10 315
BOX 15 15 5 10
The resulting mask will look as follows:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........................................
35:........................................
34:....................111111111...........
33:...................11111111111..........
32:.................111111111111111........
31:.................111111111111111........
30:................11111111111111111.......
29:...............1111111.....1111111......
28:...............111111.......111111......
27:...............11111.222222..11111......
26:...............111112222222..11111......
25:...............111112222222..11111......
24:...............111112222222..11111......
23:...............111112222222..11111......
22:...............111111222222.111111......
21:..............211111112222.1111111......
20:............322211111111111111111.......
19:............32222111111111111111........
18:............22222111111111111111........
17:............222222211111111111..........
16:............22222222111111111...........
15:............222222222...................
14:............22222222....................
13:............222222......................
12:............33333.......................
11:............33333.......................
10:........................................
9:........................................
8:........................................
7:........................................
6:........................................
5:........................................
4:........................................
3:........................................
2:........................................
1:........................................
Note that when a pixel is in 2 or more regions, it is arbitrarily assigned to a one of the
regions in question (often based on how a give C compiler optimizes boolean expressions).
Region accelerators
Two types of \fBaccelerators, to simplify region specification, are provided as natural
extensions to the ways shapes are described. These are: extended lists of parameters,
specifying multiple regions, valid for annulus, box, circle, ellipse, pie, and points; and
n=, valid for annulus, box, circle, ellipse, and pie (not point). In both cases, one
specification is used to define several different regions, that is, to define shapes with
different mask values in the region mask.
The following regions accept accelerator syntax:
shape arguments
----- ------------------------------------------
ANNULUS xcenter ycenter radius1 radius2 ... radiusn
ANNULUS xcenter ycenter inner_radius outer_radius n=[number]
BOX xcenter ycenter xw1 yh1 xw2 yh2 ... xwn yhn (angle)
BOX xcenter ycenter xwlo yhlo xwhi yhhi n=[number] (angle)
CIRCLE xcenter ycenter r1 r2 ... rn # same as annulus
CIRCLE xcenter ycenter rinner router n=[number] # same as annulus
ELLIPSE xcenter ycenter xw1 yh1 xw2 yh2 ... xwn yhn (angle)
ELLIPSE xcenter ycenter xwlo yhlo xwhi yhhi n=[number] (angle)
PIE xcenter ycenter angle1 angle2 (angle3) (angle4) (angle5) ...
PIE xcenter ycenter angle1 angle2 (n=[number])
POINT x1 y1 x2 y2 ... xn yn
Note that the circle accelerators are simply aliases for the annulus accelerators.
For example, several annuli at the same center can be specified in one region expression
by specifying more than two radii. If N radii are specified, then N-1 annuli result, with
the outer radius of each preceding annulus being the inner radius of the succeeding
annulus. Each annulus is considered a separate region, and is given a separate mask
value. For example,
ANNULUS 20 20 0 2 5 10 15 20
specifies five different annuli centered at 20 20, and is equivalent to:
ANNULUS 20.0 20.0 0 2
ANNULUS 20.0 20.0 2 5
ANNULUS 20.0 20.0 5 10
ANNULUS 20.0 20.0 10 15
ANNULUS 20.0 20.0 15 20
The mask is shown below:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:.............5555555555555..............
38:...........55555555555555555............
37:.........555555555555555555555..........
36:........55555555555555555555555.........
35:......555555555555555555555555555.......
34:.....55555555544444444444555555555......
33:....5555555544444444444444455555555.....
32:....5555555444444444444444445555555.....
31:...555555444444444444444444444555555....
30:..55555544444444444444444444444555555...
29:..55555544444443333333334444444555555...
28:.5555554444444333333333334444444555555..
27:.5555544444433333333333333344444455555..
26:555555444444333333333333333444444555555.
25:555554444443333333333333333344444455555.
24:555554444433333332222233333334444455555.
23:555554444433333322222223333334444455555.
22:555554444433333222222222333334444455555.
21:555554444433333222111222333334444455555.
20:555554444433333222111222333334444455555.
19:555554444433333222111222333334444455555.
18:555554444433333222222222333334444455555.
17:555554444433333322222223333334444455555.
16:555554444433333332222233333334444455555.
15:555554444443333333333333333344444455555.
14:555555444444333333333333333444444555555.
13:.5555544444433333333333333344444455555..
12:.5555554444444333333333334444444555555..
11:..55555544444443333333334444444555555...
10:..55555544444444444444444444444555555...
9:...555555444444444444444444444555555....
8:....5555555444444444444444445555555.....
7:....5555555544444444444444455555555.....
6:.....55555555544444444444555555555......
5:......555555555555555555555555555.......
4:........55555555555555555555555.........
3:.........555555555555555555555..........
2:...........55555555555555555............
1:.............5555555555555..............
For boxes and ellipses, if an odd number of arguments is specified, then the last argument
is assumed to be an angle. Otherwise, the angle is assumed to be zero. For example:
ellipse 20 20 3 5 6 10 9 15 12 20 45
specifies an 3 ellipses at a 45 degree angle:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:........................................
38:........................................
37:........................................
36:........33333333........................
35:......333333333333......................
34:.....3333333333333333...................
33:....333333333333333333..................
32:....33333332222233333333................
31:...3333332222222222333333...............
30:...33333222222222222233333..............
29:...333332222222222222223333.............
28:...3333222222211112222223333............
27:...33332222211111111222223333...........
26:...333322222111111111122223333..........
25:...3333222211111111111122223333.........
24:....3332222111111..1111122223333........
23:....333322211111.....11112222333........
22:....33332222111.......11112223333.......
21:.....33322221111.......11122223333......
20:.....33332221111.......11112223333......
19:.....33332222111.......11112222333......
18:......33332221111.......11122223333.....
17:.......33322221111.....111112223333.....
16:.......3333222211111..1111112222333.....
15:........3333222211111111111122223333....
14:.........333322221111111111222223333....
13:..........33332222211111111222223333....
12:...........3333222222111122222223333....
11:............333322222222222222233333....
10:.............33333222222222222233333....
9:..............3333332222222222333333....
8:...............33333333222223333333.....
7:.................333333333333333333.....
6:..................3333333333333333......
5:.....................333333333333.......
4:.......................33333333.........
3:........................................
2:........................................
1:........................................
Note in the above example that the lower limit is not part of the region for boxes,
circles, and ellipses. This makes circles and annuli equivalent, i.e.:
circle 20 20 5 10 15 20
annulus 20 20 5 10 15 20
both give the following region mask:
1234567890123456789012345678901234567890
----------------------------------------
40:........................................
39:.............3333333333333..............
38:...........33333333333333333............
37:.........333333333333333333333..........
36:........33333333333333333333333.........
35:......333333333333333333333333333.......
34:.....33333333322222222222333333333......
33:....3333333322222222222222233333333.....
32:....3333333222222222222222223333333.....
31:...333333222222222222222222222333333....
30:..33333322222222222222222222222333333...
29:..33333322222221111111112222222333333...
28:.3333332222222111111111112222222333333..
27:.3333322222211111111111111122222233333..
26:333333222222111111111111111222222333333.
25:333332222221111111111111111122222233333.
24:33333222221111111.....11111112222233333.
23:3333322222111111.......1111112222233333.
22:333332222211111.........111112222233333.
21:333332222211111.........111112222233333.
20:333332222211111.........111112222233333.
19:333332222211111.........111112222233333.
18:333332222211111.........111112222233333.
17:3333322222111111.......1111112222233333.
16:33333222221111111.....11111112222233333.
15:333332222221111111111111111122222233333.
14:333333222222111111111111111222222333333.
13:.3333322222211111111111111122222233333..
12:.3333332222222111111111112222222333333..
11:..33333322222221111111112222222333333...
10:..33333322222222222222222222222333333...
9:...333333222222222222222222222333333....
8:....3333333222222222222222223333333.....
7:....3333333322222222222222233333333.....
6:.....33333333322222222222333333333......
5:......333333333333333333333333333.......
4:........33333333333333333333333.........
3:.........333333333333333333333..........
2:...........33333333333333333............
1:.............3333333333333..............
As a final example, specifying several angles in one pie slice expression is equivalent to
specifying several separate slices with the same center. As with the annulus, if N angles
are specified, then N-1 slices result, with the ending angle of each preceding slice being
the starting angle of the succeeding slice. Each slice is considered a separate region,
and is given a separate mask value. For example,
PIE 12 12 315 45 115 270
specifies three regions as shown below:
1234567890123456789012345678901234567890
----------------------------------------
40:2222222222222222222222222222222222222222
39:2222222222222222222222222222222222222221
38:2222222222222222222222222222222222222211
37:2222222222222222222222222222222222222111
36:2222222222222222222222222222222222221111
35:3222222222222222222222222222222222211111
34:3222222222222222222222222222222222111111
33:3322222222222222222222222222222221111111
32:3322222222222222222222222222222211111111
31:3332222222222222222222222222222111111111
30:3332222222222222222222222222221111111111
29:3333222222222222222222222222211111111111
28:3333222222222222222222222222111111111111
27:3333322222222222222222222221111111111111
26:3333322222222222222222222211111111111111
25:3333322222222222222222222111111111111111
24:3333332222222222222222221111111111111111
23:3333332222222222222222211111111111111111
22:3333333222222222222222111111111111111111
21:3333333222222222222221111111111111111111
20:3333333322222222222211111111111111111111
19:3333333322222222222111111111111111111111
18:3333333332222222221111111111111111111111
17:3333333332222222211111111111111111111111
16:3333333333222222111111111111111111111111
15:3333333333222221111111111111111111111111
14:3333333333322211111111111111111111111111
13:3333333333322111111111111111111111111111
12:33333333333.1111111111111111111111111111
11:3333333333331111111111111111111111111111
10:333333333333.111111111111111111111111111
9:333333333333..11111111111111111111111111
8:333333333333...1111111111111111111111111
7:333333333333....111111111111111111111111
6:333333333333.....11111111111111111111111
5:333333333333......1111111111111111111111
4:333333333333.......111111111111111111111
3:333333333333........11111111111111111111
2:333333333333.........1111111111111111111
1:333333333333..........111111111111111111
The annulus, box, circle, ellipse, and pie shapes also accept an n=[int] syntax for
specifying multiple regions. The n=[int]syntax interprets the previous (shape-dependent)
arguments as lower and upper limits for the region and creates n shapes with evenly spaced
boundaries. For example, if n=[int] is specified in an annulus, the two immediately
preceding radii (rn and rm) are divided into int annuli, such that the inner radius of the
first is rn and the outer radius of the last is rm. For example,
ANNULUS 20 20 5 20 n=3
is equivalent to:
ANNULUS 20 20 5 10 15 20
If this syntax is used with an ellipse or box, then the two preceding pairs of values are
taken to be lower and upper limits for a set of ellipses or boxes. A circle uses the two
preceding arguments for upper and lower radii. For pie, the two preceding angles are
divided into n wedges such that the starting angle of the first is the lower bound and the
ending angle of the last is the upper bound. In all cases, the n=[int] syntax allows any
single alphabetic character before the "=", i.e, i=3, z=3, etc. are all equivalent.
Also note that for boxes and ellipses, the optional angle argument is always specified
after the n=[int] syntax. For example:
ellipse 20 20 4 6 16 24 n=3 45
specifies 3 elliptical regions at an angle of 45 degrees:
1234567890123456789012345678901234567890
----------------------------------------
40:........33333333........................
39:.....33333333333333.....................
38:....33333333333333333...................
37:...33333333333333333333.................
36:..33333333333333333333333...............
35:.3333333333222223333333333..............
34:3333333322222222222233333333............
33:33333332222222222222223333333...........
32:333333222222222222222222333333..........
31:3333322222222222222222222333333.........
30:33333222222222111122222222333333........
29:333332222222111111112222222333333.......
28:3333222222211111111111222222333333......
27:3333222222111111111111112222233333......
26:33332222221111111111111112222233333.....
25:33332222211111111.111111112222233333....
24:333322222111111......111111222223333....
23:333322222111111.......111112222233333...
22:33333222221111.........11111222223333...
21:333332222211111.........11112222233333..
20:.33332222211111.........11111222223333..
19:.33333222221111.........111112222233333.
18:..33332222211111.........11112222233333.
17:..333332222211111.......111111222233333.
16:...333322222111111......111111222223333.
15:...333332222211111111.111111112222233333
14:....333332222211111111111111122222233333
13:.....33333222221111111111111122222233333
12:.....33333322222211111111111222222233333
11:......3333332222222111111112222222333333
10:.......333333222222221111222222222333333
9:........33333322222222222222222222333333
8:.........333333222222222222222222333333.
7:..........33333332222222222222223333333.
6:...........3333333322222222222233333333.
5:.............3333333333222223333333333..
4:..............33333333333333333333333...
3:................33333333333333333333....
2:..................33333333333333333.....
1:....................33333333333333......
Both the variable argument syntax and the n=[int] syntax must occur alone in a region
descriptor (aside from the optional angle for boxes and ellipses). They cannot be
combined. Thus, it is not valid to precede or follow an n=[int] accelerator with more
angles or radii, as in this example:
# INVALID -- one too many angles before a=5 ...
# and no angles are allowed after a=5
PIE 12 12 10 25 50 a=5 85 135
Instead, use three separate specifications, such as:
PIE 12 12 10 25
PIE 12 12 25 50 a=5
PIE 12 12 85 135
The original (IRAF) implementation of region filtering permitted this looser syntax, but
we found it caused more confusion than it was worth and therefore removed it.
NB: Accelerators may be combined with other shapes in a boolean expression in any order.
(This is a change starting with funtools v1.1.1. Prior to this release, the accelerator
shape had to be specified last). The actual region mask id values returned depend on the
order in which the shapes are specified, although the total number of pixels or rows that
pass the filter will be consistent. For this reason, use of accelerators in boolean
expressions is discouraged in programs such as funcnts, where region mask id values are
used to count events or image pixels.
[All region masks displayed in this document were generated using the fundisp routine and
the undocumented "mask=all" argument (with spaced removed using sed ):
fundisp "funtools/funtest/test40.fits[ANNULUS 25 25 5 10]" mask=all ⎪\
sed 's/ //g'
Note that you must supply an image of the appropriate size -- in this case, a FITS image
of dimension 40x40 is used.]
SEE ALSO
See funtools(7) for a list of Funtools help pages