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XMM-Newton Science Analysis System Page: 1
immask
July 9, 2007
Abstract
This task makes a mask image which includes only those pixels whose values obey
the specied selection expression.
1 Instruments/Modes
The task is not XMM-specic.
2 Description
The task is designed to make a mask image (ie an image of boolean values) by applying a selection
expression to the pixel values of an input image. These pixel values are assigned to a variable named
`VAL' in the selection expression. Hence for example if one wished to mark as TRUE all pixels of the
input which exceeded 7.3 in value, one would call immask with expression=`VAL > 7.3'. All the syntax
provided by selectlib is available for this selection expression.
The output mask image is the same size as the input image. All attributes (keywords), including WCS
keywords, but excluding keywords related to any data subspace (DSS) in the input image, are copied to
the output image. The input image is expected to be in the primary array extension of the input dataset
and only this extension is written to the output.
The data type of the output is not actually boolean, but 8-bit integer: the values are either 0 or 1.
3 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
imageset yes dataset dummy default
The input image dataset.
maskset no dataset mask.ds
The output mask dataset.
xmmsas 20070708 1801-7.1.0

XMM-Newton Science Analysis System Page: 2
tempset no dataset tempset.ds
Name of temporary dataset used during the ltering operation.
tempimageset no dataset tempimage.ds
Name of a temporary cloned image dataset used while writing the output.
expression no string
The expression used to generate the boolean output.
4 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
badArrayDataType (error)
The data type of the input image was not accepted.
5 Input Files
1. A FITS dataset containing a 2-dimensional image array in the primary extension. The
datatype of the image may be 8-bit integer, 16-bit integer, 32-bit integer, 32-bit real or
64-bit real.
6 Output Files
1. A FITS dataset containing a 2-dimensional image array in the primary extension, the same
size as the input array and containing all of the keywords (except those pertaining to DSS)
of the input. The datatype of this image is 8-bit integer but its values are restricted to 0
and 1.
7 Algorithm
References
xmmsas 20070708 1801-7.1.0