NAME

tvellips - compute and / or overlay ellipses of arbitrary size and orientation

USAGE

tvellips image xcen ycen ellipt posang drad [color] [zlow] [zhigh] [redispl] [calconly] [calcfil] [calcfmt]

PARAMETERS

image = ""

Image to display and overlay ellipses upon

xcen = INDEF

X center position of ellipses in pixels

ycen = INDEF

Y center position of ellipses in pixels

ellipt = 0.

Ellipticity (1 - b/a) of the ellipses, with b/a the ratio of the minor and major axes

posang = 0.

Position angle with respect to the positive x-axis, measured in degrees counter-clockwise

drad = "1."

Comma-separated list of semi-major axis radii in pixels for the ellipses

color = "205"

Comma-separated list of colors to use when overlaying the ellipses on the image display

zlow = INDEF

Lower cut level for displaying 'image'

zhigh = INDEF

Upper cut level for displaying 'image'

redispl = yes

(Re)display 'image' prior to overlaying the ellipses?

calconly = no

Do not display, only compute the ellipses?

calcfil = ""

Name of the output file to store the computed ellipses.

calcfmt = "full" ["basic"|"full"|"tvmark"]

Format to use for the output file 'calcfil'

calcpid = yes

Prepend the image name in the output file (formats "basic" and "full" only)?

DESCRIPTION

Task to compute and/or overlay a set of ellipses of arbitrary ellipticity, orientation and size, as specified by parameters 'ellipt', 'posang' and 'drad', where 'drad' is a comma-separated list of semi-major axis radii. Default is to first display 'image' and then overlay the ellipses, but if 'image' is loaded already, this behavior may be suppressed by setting 'redispl = no'.

When 'calconly = yes', this task only computes the ellipses and stores them in 'calcfil' in one of three formats ("basic", "full" or "tvmark"), but does not display the results. If 'calconly = no' but 'calcfil' is specified, the computed ellipses are not only displayed but also stored.

If 'xcen' and 'ycen' are both INDEF upon input, the center pixel in the current image or image section is taken as the center for the ellipses. If 'zlow' and/or 'zhigh' are set to INDEF while 'calconly = no', auto scaling is used when displaying the image (see task 'rjtools.xdisplay').

The colors in comma-separated list 'color', used when overlaying the ellipses on the image display, are encoded numerically as in task 'tv.tvmark', with 0--200 representing grey levels between black and white and 202--209 representing display graphics colors (202=black, 203=white, 204=red, 205=green, 206=blue, 207=yellow, 208=cyan, and 209=magenta). If more radii than colors are specified, the last color specified is used for the remaining ellipses.

EXAMPLES

1. Draw a green ellipse marking the effective isophote (isophote containing half the total light) and a blue ellipse marking the B=26 mag/arcsec^2 isophote in a galaxy image:

    rj>  tvellips N3795B.fits[128:384,128:384] xcen=257.6 ycen=256.4 \

    >>>    ellipt=0.7391 posang=-37 drad="25.63,124.08" color="205,206"

2. Same as the above example, but now store the resulting ellipses in output file "N3795B.ellips" in format "full" and with the image name prepended to each pixel position on the ellipses:

    rj>  tvellips N3795B.fits[128:384,128:384] xcen=257.6 ycen=256.4 \

    >>>    ellipt=0.7391 posang=-37 drad="25.63,124.08" color="205,206" \

    >>>    calcfil=".ellips" calcfmt="full" calcpid=yes
    rj>  type N3795B.ellips | page
    N3795B.fits[278:278,241:241]
    N3795B.fits[278:278,242:242]
    N3795B.fits[278:278,243:243]
    N3795B.fits[278:278,244:244]
    N3795B.fits[278:278,245:245]
    N3795B.fits[277:277,245:245]
    N3795B.fits[277:277,246:246]
    N3795B.fits[277:277,247:247]
    N3795B.fits[276:276,247:247]
    N3795B.fits[276:276,248:248]

    ...

3. Had we chosen format "tvmark" in the example above, the output file would look as follows:

    278.07 240.98 101 :color 205
    278.07 240.98 101 .
    278.21 241.19 101 s
    278.32 241.44 101 s
    278.40 241.70 101 s
    278.45 241.99 101 s
    278.46 242.29 101 s
    278.45 242.62 101 s
    278.40 242.97 101 s
    278.32 243.34 101 s

    ...

and in this case the ellipses may be overlayed at a later time using 'tvmark':

    cl>   tvmark (1, "", commands="N3795B.ellips")

REVISIONS

TVELLIPS v2.10, Apr 22 1997 [R.A. Jansen]

First 'rjtools' version of this task, adapted from an earlier script by M. Franx; IRAF 2.10.4

TVELLIPS v2.11, Jun 30 2000 [RAJ]

Added support for multi-extension images and image sections; IRAF 2.11.3

TVELLIPS v2.12, Aug 10 2003 [RAJ]

Added support for differently colored ellipses, by making 'color' a comma-separated list of colors (int -> string) and adding a :color statement to the 'tvmark' command file. Cleaned-up code and wrote this help file; IRAF 2.12.1

BUGS

SEE ALSO

tvmark, xdisplay, chkimg, rpparse, rpbuild, cparse