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XMM-Newton Science Analysis System Page: 1
imcrop
July 9, 2007
Abstract
The task clips out a rectangular subregion of an image and returns this.
1 Instruments/Modes
The task is not XMM-specic.
2 Description
The task cuts out a rectangular subset of the input image and returns this as an output image. This is
done in two stages:
1. If the trimborder parameter is set, the task rst constructs the smallest possible rectangle
such that no pixel outside the rectangle has a value other than zero. If trimborder=`no',
this rst-stage rectangle is taken to be identical with the border of the input image.
2. The task then constructs a second, smaller, inner rectangle. The fractional relations between
the occurrence of the sides of this inner rectangle and the dimensions of the rst rectangle
are given via the parameters xfraclo, xfrachi, yfraclo and yfrachi.
Note that, if WCS keywords are present in the input image, these are adjusted to re ect the transforma-
tions performed on the output.
3 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
inset yes dataset dummy default
The dataset containing the input image.
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outset no dataset cropped image.ds
The dataset to contain the (cropped) output image.
trimborder no boolean yes yes|no
Whether to trim o the any blank (zero-valued) border.
xfraclo no real 0.0 0:0 xfraclo 1:0
Position of the left-hand edge of the cropping rectangle expressed as a fraction of the image width (after
removal of the blank border, if trimborder was set to `yes').
xfrachi no real 1.0 0:0 xfrachi 1:0
Position of the right-hand edge of the cropping rectangle expressed as a fraction of the image width (after
removal of the blank border, if trimborder was set to `yes').
yfraclo no real 0.0 0:0 yfraclo 1:0
Position of the lower edge of the cropping rectangle expressed as a fraction of the image height (after
removal of the blank border, if trimborder was set to `yes').
yfrachi no real 1.0 0:0 yfrachi 1:0
Position of the upper edge of the cropping rectangle expressed as a fraction of the image height (after
removal of the blank border, if trimborder was set to `yes').
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.
imageAllZero (error)
The user request trimborder=yes (the default), but imcrop can't trim away the zero-valued
bits as requested because there would be nothing left of the image - it is all zero-valued.
sizelessImageArray (error)
The dimensions of the input image array are zero.
badXclipValues (error)
xfraclo must be less than xfrachi.
badYclipValues (error)
yfraclo must be less than yfrachi.
badArrayDataType (error)
The data type of the input image was not recognized.
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
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64-bit real.
6 Output Files
1. A FITS dataset containing a 2-dimensional image array in the primary extension, of the same
datatype as the input array but NOT generally the same size. The output dataset and array
headers contain all of the keywords (except those pertaining to DSS) of the corresponding
inputs. WCS keywords, where present in the input array header, are adjusted in the output
to re ect the eect of the cropping process.
7 Algorithm
References
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