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Last modified: 26 October 2016

URL: http://cxc.harvard.edu/ciao/bugs/dmcontour.html

Bugs: dmcontour


Bugs

Problems at the edge of images  (01 Dec 2006)

When a contour intersects the edge of an image, dmcontour draws a frame around the image and creates contours that are marked as "exclude" regions (i.e. have a red line through them when displayed in ds9).

Workaround:

If you are running into this problem, you have to make sure that your contours don't have a value that occurs at the edge of the image. The safest way to do this is to check the max value for the bounding rows/edges and then choose your contour level to be greater than that. It looks tedious, but you could script this if you are doing it often:

unix% dmlist image.fits blocks
 
--------------------------------------------------------------------
Dataset: image.fits
--------------------------------------------------------------------
 
     Block Name                          Type         Dimensions
--------------------------------------------------------------------
Block    1: CONVOLVE                       Image      Real4(263x218)


unix% dmstat image.fits"[#2=1]" median=yes centroid=no |grep max
    max:        2.8171137093e-18              @:        ( 3856.13 4208.04 )

unix% dmstat image.fits"[#1=1]" median=yes centroid=no |grep max
    max:        3.6766300528e-18              @:        ( 3840.33 4214.44 )

unix% dmstat image.fits"[#1=263]" median=yes centroid=no |grep max
    max:        5.2055576098e-18              @:        ( 3866.53 4229.24 )

unix% dmstat image.fits"[#2=218]" median=yes centroid=no |grep max
    max:        7.753583262e-18               @:        ( 3863.73 4229.64 )

So as long as the contour level is > 7.75e-18, you won't get the frame/exclude behavior.

This doesn't mean that you can't choose contours lower than the max value. It just means that by setting your bar above the highest, you know that you will not run into this bug.


Last modified: 26 October 2016
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