Provided by: montage_6.0+dfsg-6_amd64 bug


       mDiff - Calculates the difference between a pair of overlapping images


       mDiff [-d level] [-n(o-areas)] [-s statusfile] in1.fits in2.fits out.fits template.hdr


       mDiff  calculates a simple difference between a single pair of overlapping images. This is
       meant for use on reprojected images where  the  pixels  already  line  up  exactly.  mDiff
       analyzes an image metadata table to determine a list of overlapping images.  Each image is
       compared with every other image to determine all  overlapping  image  pairs.   A  pair  of
       images  are  deemed to overlap if any pixel around the perimeter of one image falls within
       the boundary of the other image.


       -d level
              Turns on debugging to the specified level (1-4).

       -n     No-area-images flag. Creates difference image without  requiring  pixel  area  FITS

       -z factor
              Scale second image by factor before subtracting.

       -s statusfile
              Output and errors are sent to statusfile instead of to stdout


              First input FITS file.  (Also needs area image in1_area.fits, or use -n flag)

              Second input FITS file.(Also needs area image in2_area.fits, or use -n flag)

              Difference FITS image to be generated.

              FITS header template used to generate output image.


       FITS image and area image representing the difference in the overlap region.


       OK     [struct stat="OK"]

       ERROR  Cannot open status file: statusfile

       ERROR  Images don't overlap

       ERROR  All pixels are blank

       ERROR  Template file not found

       ERROR  FITS library error

       ERROR  general error


       $ mDiff proj/in1.fits proj/in2.fits output/diff.fits template.hdr
              [struct stat="OK"]


       The drizzle algorithm has been implemented but has not been tested in this release.

       If  a  header  template  contains  carriage  returns  (i.e., created/modified on a Windows
       machine), the cfitsio library will be unable to read it properly, resulting in the  error:
       [struct stat="ERROR", status=207, msg="illegal character in keyword"]

       It  is  best  for the background correction algorithms if the area described in the header
       template completely encloses all of the input images in their entirety. If parts of  input
       images  are  "chopped  off"  by  the  header  template,  the background correction will be
       affected. We recommend you use an expanded header  for  the  reprojection  and  background
       modeling  steps, returning to the originally desired header size for the final coaddition.
       The default background matching assumes that there are no non-linear background variations
       in  the  individual  images  (and  therefore  in the overlap differences). If there is any
       uncertainty in this regard, it is safer to turn on the "level  only"  background  matching
       (the "-l" flag in mBgModel.


       2001-2015 California Institute of Technology, Pasadena, California

       If  your  research  uses  Montage,  please  include  the  following acknowledgement: "This
       research made use of Montage. It is funded by the National Science Foundation under  Grant
       Number  ACI-1440620,  and  was  previously  funded  by  the National Aeronautics and Space
       Administration's Earth Science Technology Office, Computation Technologies Project,  under
       Cooperative  Agreement  Number  NCC5-626  between  NASA  and  the  California Institute of

       The Montage distribution includes an adaptation of the MOPEX algorithm  developed  at  the
       Spitzer Science Center.