Module: Guardrails::HexNormalizer

Defined in:
lib/guardrails/hex_normalizer.rb

Class Method Summary collapse

Class Method Details

.distance(a, b) ⇒ Object

Maximum per-channel (R / G / B) difference between two normalized hex colors, on a 0..255 scale. Returns nil if either value isn’t a 7-char hex after normalization. Distance 0 = identical color.



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# File 'lib/guardrails/hex_normalizer.rb', line 33

def distance(a, b)
  a_norm = normalize(a)
  b_norm = normalize(b)
  return nil unless a_norm.length == 7 && a_norm.start_with?("#")
  return nil unless b_norm.length == 7 && b_norm.start_with?("#")

  diffs = [
    (a_norm[1..2].to_i(16) - b_norm[1..2].to_i(16)).abs,
    (a_norm[3..4].to_i(16) - b_norm[3..4].to_i(16)).abs,
    (a_norm[5..6].to_i(16) - b_norm[5..6].to_i(16)).abs
  ]
  diffs.max
end

.normalize(value) ⇒ Object

Normalize a hex color literal for equality comparison:

  • lowercase

  • expand 3-char shorthand (#fa3 -> #ffaa33)

  • strip alpha channel (#ffaa3380 -> #ffaa33)

  • return non-hex input unchanged (after lowercasing)



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# File 'lib/guardrails/hex_normalizer.rb', line 12

def normalize(value)
  v = value.to_s.downcase.strip
  return v unless v.start_with?("#")

  case v.length
  when 4 # #fa3 -> #ffaa33
    "#" + v[1..].chars.map { |c| c * 2 }.join
  when 5 # #fa3a -> #ffaa33 (drop alpha)
    ("#" + v[1..].chars.map { |c| c * 2 }.join)[0..6]
  when 7 # #ffaa33 (canonical)
    v
  when 9 # #ffaa3380 -> #ffaa33
    v[0..6]
  else
    v
  end
end