Module fits 

FITS file reading and data extraction.

This module provides functions for reading HEALPix astronomical data from FITS files. It supports both:

• Dense maps: Complete sky coverage (standard NSIDE² pixels)
• Sparse maps: Partial sky coverage with explicit PIXEL column indexing

FITS Format Support

• Binary table format (.fits files)
• HEALPix RING or NEST pixel ordering
• Sparse maps with IMPLICIT or EXPLICIT indexing schemes via the INDXSCHM keyword

Sparse Map Handling

For sparse maps with EXPLICIT indexing, this module automatically expands the data to a full dense array with UNSEEN values for omitted pixels.

Tier 4.2b Optimization: Sparse map column extraction is parallelized via rayon for efficient multi-core processing of large sparse catalogs.

Examples

use map2fig::read_healpix_column;

let data = read_healpix_column("map.fits", 0);
println!("Loaded {} pixels", data.len());

Functions

read_healpix_column

Read a HEALPix column from a FITS binary table.

read_healpix_column_cached

Read a HEALPix column with caching support (Tier 5.2.1 optimization)

read_healpix_column_mmap

Read a HEALPix column from a FITS file using memory-mapped I/O

read_healpix_meta_cached

Read FITS metadata with caching support This function attempts to use cached metadata to avoid expensive header parsing When MAP2FIG_PROFILE environment variable is set, outputs diagnostic timing info

read_healpix_meta_cached_mmap

Read FITS metadata using memory-mapped I/O (mmap variant of read_healpix_meta_cached)