Class: AstroSubframeOrganizer::Utils::FitsStripper

Inherits:
Object
  • Object
show all
Defined in:
lib/astro_subframe_organizer/utils/fits_stripper.rb

Overview

Strips image data and identifying location information from FITS files. The resulting file is valid FITS with NAXIS set to 0, meaning no data array follows the header block.

Location headers stripped: SITELAT, SITELONG, SITEELEV, RA, DEC, OBJCTRA, OBJCTDEC, CRVAL1, CRVAL2, CRPIX1, CRPIX2, and WCS keywords.

Constant Summary collapse

BLOCK_SIZE = 
2880
CARD_SIZE = 
80
CARDS_PER_BLOCK = 
BLOCK_SIZE / CARD_SIZE
LOCATION_HEADERS = 
%w[
  SITELAT
  SITELONG
  SITEELEV
  RA
  DEC
  OBJCTRA
  OBJCTDEC
].freeze
WCS_PREFIXES =

WCS (World Coordinate System) headers that encode pointing information

%w[CRVAL CRPIX CD1_ CD2_ A_ B_ AP_ BP_ CTYPE CUNIT].freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(input_path, output_path = nil) ⇒ FitsStripper

Returns a new instance of FitsStripper.



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# File 'lib/astro_subframe_organizer/utils/fits_stripper.rb', line 33

def initialize(input_path, output_path = nil)
  @input_path  = input_path
  @output_path = output_path || input_path # default to in-place
end

Class Method Details

.strip(input_path, output_path = nil) ⇒ Object 



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# File 'lib/astro_subframe_organizer/utils/fits_stripper.rb', line 29

def self.strip(input_path, output_path = nil)
  new(input_path, output_path).strip
end

Instance Method Details

#already_stripped? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/astro_subframe_organizer/utils/fits_stripper.rb', line 38

def already_stripped?
  File.open(@input_path, 'rb') do |f|
    loop do
      block = f.read(BLOCK_SIZE)
      return false unless block&.length == BLOCK_SIZE

      cards = block.scan(/.{#{CARD_SIZE}}/mo)
      naxis_card = cards.find { |c| c.start_with?('NAXIS   =') }
      return naxis_card.match?(/=\s+0\b/) if naxis_card

      return false if header_end?(block)
    end
  end
  false
end

#strip ⇒ Object 



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# File 'lib/astro_subframe_organizer/utils/fits_stripper.rb', line 54

def strip
  header_blocks = read_header_blocks
  patched       = patch_naxis(header_blocks)
  patched       = strip_location_headers(patched)
  File.binwrite(@output_path, patched)
  @output_path
end