Name
collapse - collapse an image along X or Y
Synopsis
collapse [options] <in> [out]
Description
collapse is used to create a 1D signal from an input image, collapsing
pixels along the X or Y direction. The default collapsing method is a
simple sum of all pixels along lines or columns. A median collapse (-m
option) is done by keeping only the median value for each processed
line or column. A number of lowest/highest pixels can be rejected
before the median is computed, see the -r option.
The output is an ASCII file containing two columns. The first column
contains the X or Y pixel position, and the second column contains the
collapsed value. The output file name is either provided on the com-
mand-line as the last argument, or will be built as:
If the input name is inputname.fits, the output name is inputname_line.
You can also request the output to be a FITS file, i.e. a FITS image
with a single line. See the -f or --fits option.
Options
-d or --dir x | y
Collapse along the X or Y direction. Default is to collapse
along the Y direction, i.e. the output is a line of pixels, each
pixel being computed as a collapse of the column it belongs to.
-f or --fits
Save the result to a FITS file containing a single line, instead
of an ASCII file. This is useful as input if you want to ’uncol-
lapse’ the image.
-g or --gnuplot
Activate a gnuplot output. This option will only work if gnuplot
is installed for your user account and accessible from the com-
mand-line.
-m or --median
Collapse the image with a median method, rather than a simple
sum.
-r or --reject ’lo hi’
Rejects the ’lo’ lowest and ’hi’ highest pixel values before
applying a median collapse. Default for these rejection parame-
ters is zero.
-u or --uncollapse width
This option actually performs a "reverse" collapse and will cre-
ate a 2d image from a single line or column. This is useful to
subtract out from the initial image some row or column-specific
defects. With this option, the input file must be a FITS file,
which means that you should have used the -f or --fits option
previously to save the collapsed image to a one-row or one-col-
umn FITS image. The specified width indicates the size you want
to give to this new image, in the newly created direction. This
option is incompatible with all others.
Examples
Collapse the image ’im.fits’ along Y, with simple sum. Keep default
output name ’im_line’.
collapse im.fits
Collapse the image ’im.fits’ along X, with median collapse without
rejection, keep default output name ’im_line’:
collapse -d x -m im.fits
Collapse the image ’im.fits’ along X, with median collapse rejecting
the 80 low and 90 high pixels, naming the output ’coll_line’:
collapse -d x -m -r ’80 90’ im.fits coll_line