iprocess_mask

This IDL facility provides an interface to F90 'process_mask' facility. For a given input binary mask, it can determine the angular distance in Radians of each valid (1 valued) pixel to the closest invalid (0 valued) pixel, with the option of ignoring small clusters of invalid pixels. The distance map can then be used to generate an apodized mask.

Location in HEALPix directory tree: src/idl/interfaces/iprocess_mask.pro 

FORMAT

IDL> IPROCESS_MASK, mask_in, distance_map,[ binpath=, filled_mask=, /help, hole_arcmin2=, hole_pixels=, keep_tmp_files=, /nested, ordering=, /ring, /silent, tmpdir=]

QUALIFIERS

mask_in

required input: input binary mask. It can be a FITS file, or a memory array containing the mask to process.

distance_map

optional output: double precision angular distance map in Radians. It can be a FITS file, or a memory array. It will have the same ordering as the input mask.

KEYWORDS

binpath=

full path to back-end routine default:$HEXE/process_mask, then $HEALPIX/bin/process_mask
– a binpath starting with / (or $\backslash$),   or $ is interpreted as absolute
– a binpath starting with ./ is interpreted as relative to current directory
– all other binpaths are relative to $HEALPIX

filled_mask=

optional output mask with holes smaller than hole_arcmin2 or hole_pixels filled in. Will have the same ordering as the input mask

/help

if set, prints extended help

hole_arcmin2

Minimal size (in arcmin²) of invalid regions to be kept (can be used together with hole_pixels, the result will be the largest of the two). default:0.0

hole_pixels

Minimal size (in pixels) of invalid regions to be kept (can be used together with hole_arcmin2, the result will be the largest of the two). default:0

/keep_tmp_files

if set, temporary files are not discarded at the end of the run

/nested

if set, signals that the mask read online is in NESTED scheme (does not apply to FITS file), see also /ring and Ordering

ordering=

either 'RING' or 'NESTED', ordering of online mask, see /ring and /nested

/ring

see /nested and Ordering above

/silent

if set, works silently

tmpdir=

directory in which are written temporary files default:IDL_TMPDIR (see IDL documentation)

DESCRIPTION

iprocess_mask is an interface to 'process_mask' F90 facility. It requires some disk space on which to write the parameter file and the other temporary files. Most data can be provided/generated as an external FITS file, or as a memory array.

RELATED ROUTINES

This section lists the routines related to iprocess_mask

idl

version 6.4 or more is necessary to run iprocess_mask.

process_mask

F90 facility called by iprocess_mask.

ialteralm

IDL Interface to F90 alteralm

ianafast

IDL Interface to F90 anafast and C++ anafast_cxx

ismoothing

IDL Interface to F90 smoothing

isynfast

IDL Interface to F90 synfast

EXAMPLE:

npix = nside2npix(256)

mask = replicate(1, npix) & mask[randomu(seed,100)*npix] = 0

iprocess_mask, mask, distance, /ring, /silent

mollview, distance

A binary mask in which 100 randomly located pixels are 0-valued (=invalid) is generated. Then the distance (in Radians) of the valid pixels to the closest invalid pixels is computed and plotted.