xdisplay

xdisplay (Aug2004)

rjtools

xdisplay (Aug2004)

xdisplay

NAME

xdisplay - flexible task to display an image with sensible defaults

USAGE

xdisplay image [buff] [z1] [z2] [lsig] [hsig] [zmode] [cenx] [ceny] [sizx] [sizy] [zoom] [erase] [verbose]

PARAMETERS

image = "": Image to display

buff = 1: Frame buffer to use for display

z1 = INDEF: Fix minimum level to display to 'z1', unless 'z1' is smaller than the minimum pixel value

z2 = INDEF: Fix maximum level to display to 'z2', unless 'z2' is larger than the maximum pixel value

lsig = 3.: Set minimum level to display to 'lsig' sigma below the background level, unless that would be smaller than the minimum pixel value

hsig = 15.: Set maximum level to display to 'hsig' sigma above the background level, unless that would be larger than the maximum pixel value

zmode = "linear" ["linear"|"log"]: Type of transformation to apply

cenx = 0.5: X center position (fraction of the full image display)

ceny = 0.5: Y center position (fraction of the full image display)

sizx = 1.0: Display window horizontal size

sizy = 1.0: Display window vertical size

zoom = 1.: Default magnification factor

erase = yes: Erase frame before loading image?

verbose = no: Print warnings and messages?

(tz1) [real]: Minimum level actually displayed (after sigma clipping and fuzzy logic)

(tz2) [real]: Maximum level actually displayed (after sigma clipping and fuzzy logic)

(tsig) [real]: Approximate standard deviation after clipping

(tmax) [real]: Maximum pixel value found after clipping in a section with the same center as the full region to display, but 1/4 the size.

(tmin) [real]: Minimum pixel value found after clipping in a section with the same center as the full region to display, but 1/4 the size.

Parameters 'lsig' and 'hsig' define sigma clipping levels that are applied after an initial iteration to determine the image statistics. The resulting range of pixel values is compared to the values specified for 'z1' and/or 'z2' (if they differ from INDEF), and are then further tweaked based on the statistics in a smaller region 1/4 the size centered on the region that is to be displayed. The rationale for this is that usually the object(s) of interest are nearer to the center than to the border of the display region.

This task is mainly used as a 'quick-look' tool. For a large variety of data (be they spectra, biases, stellar images or images of extended objects; at very low [HST UV] or very high [groundbased NIR] signal levels; and with very small or very large dynamic range) this task will display your image such that you actually see you object or feature of interest; once sensible display limits/contrast are determined, native IRAF task 'display' is of course much faster. 'display' also allows you to specify limits that significantly exceed the actual range of pixel values (which this task does not).

EXAMPLES

    rj>  unlearn xdispl
    rj>  xdispl N3795B.fits verbose+
    Displaying image "N3795B.fits":  z1=53.20, z2=261.23

    rj>  xdispl N3795B.fits z1=INDEF z2=INDEF zmode="log" verbose+
    Displaying image "N3795B.fits":  z1=53.20, z2=261.23

    rj>  xdispl N3795B.fits z1=-1000 z2=1000 zmode="log" verbose+
    WARNING: z2 > IMAX = 286.1349! Ignoring requested 'z2'...
    WARNING: z1 < IMIN = 50.38003! Ignoring requested 'z1'...
    Displaying image "N3795B.fits":  z1=50.38, z2=286.13

    rj>  xdispl N3795B.fits z1=-1000 z2=1000 lsig=5. hsig=20. verbose+
    WARNING: z2 > IMAX = 363.2227! Ignoring requested 'z2'...
    WARNING: z1 < IMIN = 12.86221! Ignoring requested 'z1'...
    Displaying image "N3795B.fits":  z1=12.86, z2=363.22

    rj>  unlearn xdispl
    rj>  xdispl N3795B.fits lsig=5. hsig=20. verbose+
    Displaying image "N3795B.fits":  z1=25.18, z2=338.95

REVISIONS

XDISPLAY v2.10, Jul 31 1997 [R.A. Jansen]: First version of this task; IRAF 2.10.4

XDISPLAY v2.11, Jun 14 2000 [RAJ]: Added support for multi-extension FITS images; IRAF 2.11.3

XDISPLAY v2.11, May 11 2001 [RAJ]: Added 'zoom' and 'buff' parameters; IRAF 2.11.3

XDISPLAY v2.12, Jul 18 2003 [RAJ]: Changed imroot->impath//imroot after change to 'chkimg'; added 't*' task parameters to return the display levels actually used after clipping and tweaking; wrote this help file; IRAF 2.12.1

XDISPLAY v2.12, Jul 12 2007 [RAJ]: Fixed bug in call to 'rpbuild' that caused message about "No pixels with values between .. and ..!" to be printed for Multi-Extension FITS images with an extension/plane specifier; IRAF 2.12.2

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PARAMETERS

DESCRIPTION

EXAMPLES

REVISIONS

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