WARPSTACK

Name

warpstack

Purpose (one Line Only)

Stack a set of images on a given ROI warped to a master image

Description

This tool is designed to build a reference image for a given image of
the sky. The reference image is intended to be subtracted by a later
tool to remove the fixed stellar background. The template is built
by resampling the input reference images to precisely match the
master image, which includes its scale, orientation and any optical
distortions. The input list of reference images should be a reasonble
list of images to be considered but not all of them are required to be
useful for this purpose (ie., no overlap). However, it is up to the
calling program to not propose reference images that contain the object
of interest on or near the location of that object in the master image.
The stack is built from those reference images that have overlap with
the ROI on the master image. The software works to use only the best
data from the reference image list to make the template.
When complete, four files are saved. 1) a log file containg information
about the stacking process, 2) the stacked image in FITS format, 3) the
cube from which the stack was built, also in FITS format, and 4) a screen
shot of the template image saved in .png format
Construction of templates works best where there are lots of images to
work with but this tool strives to make do if the number of files is
small. With 5 or more images, it will do a robust average of the cube.
With 4 or less a straight median is used. If there is only one relevant
file you get that one file, resampled to match but it will still have
all image blemishes, like cosmic ray strikes.

Calling Sequence

warpstack,fnim,fnref,error

Inputs

fnim - File name of the master image that the stack will be built to match
fnref - List of files that may be useful for building a stack

Optional Input Parameters

Keyword Input Parameters

FWHM - Vector of fwhm, in pixels for each image in fnref. If provided,
this can speed up the program significantly. The default
is to determine this on the images internally.
GAIN - Gain of detector, default is 1e-/DN
KEYFILE - Header keyword list (see loadkeys.pro)
OUTPATH - Directory where output files are to be written to. Default is
to write to the current directory.
PATH - Directory where input images (master and reference) can be
found. You can put paths on the inputs in which case use
the default of '' for this keyword.
ROI - Region of interest from master image that stack will be built
to. The default is to do it for the entire image. Provide
a 4-element vector [i0,j0,i1,j1] (lower left hand corner and
upper right hand corner of region) to use this option.
VERBOSE - Flag, if set will turn on a lot of printed output to see what
the program is doing.
MINAREA - minimum fraction of area overlap allowed to keep a template
image. Default = 0.65

Outputs

error - Flag, set to 1 in case of error. The

Keyword Output Parameters

Common Blocks

Side Effects

Restrictions

This tool depends on the presence of WCS information in the image headers
and expects to find my format information in there (see astinfo.pro).

Procedure

Modification History

2016/04/12, Written by Marc W. Buie, Southwest Research Institute
2016/04/21, MWB, slight fixes to logic for output file names when
input files contain their paths.
2016/09/29, MWB, added MINAREA keyword