== pswarp ==

(Up to the [wiki:IPP_Description IPP Description Page])

pswarp invocation (single input exposure set):

{{{
pswarp -file input.fits output skycell                    : input.fits must define the astrometry of the input pixels, skycell defines target astrometry.
pswarp -file input.fits -astrom astrom.cmf output skycell : astrom.cmf defines astrometry for input.fits
}}}

pswarp invocation (multiple inputs):
{{{
pswarp -input file.mcd output skycell                     : input files are defined in the file.mdc 
}}}

Example of input.mdc:
{{{
INPUT MULTI

INPUT METADATA
  INPUT     STR   RINGS.V3.skycell.1314.011.stk.1033022.fits   # signal image filename
  MASK      STR   RINGS.V3.skycell.1314.011.stk.1033022.mask.fits   # signal image filename
  VARIANCE  STR   RINGS.V3.skycell.1314.011.stk.1033022.wt.fits   # signal image filename
END

INPUT METADATA
  INPUT     STR   RINGS.V3.skycell.1314.012.stk.1033023.fits   # signal image filename
  MASK      STR   RINGS.V3.skycell.1314.012.stk.1033023.mask.fits   # signal image filename
  VARIANCE  STR   RINGS.V3.skycell.1314.012.stk.1033023.wt.fits   # signal image filename
END
}}}

pswarp outline

 * generic initializations
 * pswarpArguments      : parse the command line arguments
 * pswarpParseCamera    : examine the input files and skycell, construct containers for the outputs (do not yet generate pixels)
 * pswarpOptions        : set various options which may depend on the camera and command line arguments
 * pswarpDefineLayout   : load astrometry information (headers only), determine the overlaps between the inputs and the outputs, generate the output pixels
 * pswarpLoop           : loop over inputs & outputs, warp the inputs into the outputs, transform the input sources (if any), measure the new PSF model, convert input metadata to output metadata values
 * pswarpLoopBackground : equivalent to pswarpLoop, transform the background models
 * pswarpCleanup        : write the outputs to disk, free memory

NOTE: as of 2013.05.09 there has been a substantial re-work of pswarp to enable 'inverse warping', that is to say warping from skycells to the original focal plane.  This modification drove a few specific changes:

 * the output format may now represent a full FPA output file (with chips and cells, etc).  
 * there may now be multiple input 'exposures' (more accurately: file sets) so that a group of skycells can be warped to a single output image
 * the astrometric relationships / overlaps are calculated up front (in pswarpDefineLayout) before any pixels are loaded.  This is necessary to avoid generating the output pixels in (for example) a full GPC1 FPA if only a few of the output pixels are needed.
 * the input files may now be specified in a metadata config file as illustrated above (similar to the inputs to ppStack & psphotStack).

There are effectively 3 modes of operation : chip-to-warp (the traditional mode), chip-to-chip, and warp-to-chip.