Reorder image axes
PARAMETER SUMMARY
imagename Name of the input image
outfile Name of output CASA image. If blank, no disk image is written.
order Output axes mapping
wantreturn Return an image tool referencing the transposed image?
This task reorders (transposes) the axes in the input image to the specified
order. The associated pixel values and coordinate system are transposed.
If the outfile parameter is empty, only a temporary image is created; no output image
is written to disk. The temporary image can be captured in the returned value (assuming
wantreturn is true).
The order parameter describes the mapping of the input axes to the output axes.
It can be one of three types: a non-negative integer, a string, or a list of
strings. If a string or non-negative integer, it should contain
zero-based digits describing the new order of the input axes. It must
contain the same number of (unique) digits as the number of input axes. For example,
specifying reorder="1032" or reorder=1032 for a four axes image maps input axes
1, 0, 3, 2 to output axes 0, 1, 2, 3. In the case of order being a nonnegative integer
and the zeroth axis in the input being mapped to zeroth axis in the output, the zeroth
digit is implicitly understood to be 0 so that to transpose an image where one would
use a string order="0321", one could equivalently specify an int order=321.
Because of ambiguity for axes numbers greater than nine, using string or integer order
specifications cannot handle images containing more than 10 axes.
The order parameter can also be specified as a list of strings which uniquely match,
ignoring case, the first characters of the image axis names (ia.coordsys().names()).
So to reorder an image with right ascension, declination, and frequency axes, one could
specify order=["d", "f", "r"] or equivalently ["decl", "frequ", "right a"]. Note that
specifying "ra" for the right ascension axis will result in an error because "ra" does
not match the first two characters of right ascension.
Axes can be simultaneously inverted in cases where order is a string or an array of
strings by specifying negative signs in front of the axis/axes to be inverted. So,
in a 4-D image, order="-10-3-2" maps input axes 1, 0, 3, 2 to output axes 0, 1, 2, 3
and reverses the direction and values of input axes 1, 3, and 2.
EXAMPLE:
# Swap the stokes and spectral axes in an RA-Dec-Stokes-Frequency image
imagename = "myim.im"
outfile = "outim.im"
order = "0132"
imtrans()
# or
outfile = "myim_2.im"
order = 132
imtrans()
# or
outfile = "myim_3.im"
order = ["r", "d", "f", "s"]
imtrans()
# or
utfile = "myim_4.im"
order = ["rig", "declin", "frequ", "stok"]
imtrans()
1.8.0
