Last modified: December 2022

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AHELP for CIAO 4.15


Context: Tools::Image


Get image values at a specified (RA,DEC)


evalpos  infile ra dec [output] [tmpdir] [verbose]


'evalpos' looks up the pixel value in an image at the input coordinates. A stack of input images can be used and evalpos will iterate through them, printing each value to the screen; only the value from the last file processed is stored in the "output" parameter. If the units are available in the image, they are printed to the screen with the output value.


evalpos img.fits 09:19:09.547 +21:14:31.72
img.fits 09:19:09.547 +21:14:31.72 1.81125e-05 [photon cm^-2 s^-1]

pget evalpos output

Gets the image value from img.fits at the location (RA,Dec)=(09:19:09.547,+21:14:31.72). The value is stored in the parameter file and printed to the screen with the units from the input file ([photon cm^-2 s^-1]) .


name type ftype def min max reqd
infile file input       yes
ra string         yes
dec string         yes
output real          
tmpdir file   /tmp      
verbose integer   0 0 5  

Detailed Parameter Descriptions

Parameter=infile (file required filetype=input)

The input image name

The input image name. Multiple images can be input as a stack.

Parameter=ra (string required)

Right Ascension

Must be a string in sexigesimal format

Parameter=dec (string required)


Must be a string in sexigesimal format

Parameter=output (real)

The output value

The output value from the last image in the stack

Parameter=tmpdir (file default=/tmp)

Temporary directory

Name of the directory for temporary files.

Parameter=verbose (integer default=0 min=0 max=5)

The tool chatter level

Verbose can be from 0 to 5, generating different amounts of debugging output.


Locations picked just outside the image boundary may return incorrect values with method=closest

The wrong value is returned when using method=closest for locations outside the image boundary but within 0.5 of a pixel of the bottom and left side of the image.

All locations outside the image should return a NaN; however, for these locations the closest edge pixel location is returned.

See Also

dmappend, dmcontour, dmellipse, dmfilth, dmimg2jpg, dmimgadapt, dmimgblob, dmimgcalc, dmimgdist, dmimgfilt, dmimghist, dmimghull, dmimglasso, dmimgpick, dmimgpm, dmimgproject, dmimgreproject, dmimgthresh, dmmaskbin, dmmaskfill, dmnautilus, dmregrid, dmregrid2, dmstat, evalpos, imgmoment, mean_energy_map, pileup_map