Module: Trackplot::ColorScale

Defined in:
lib/trackplot/color_scale.rb

Class Method Summary collapse

Class Method Details

.categorical(hex, count: 8) ⇒ Object

Evenly-spaced hues, preserving base color’s saturation and lightness.



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# File 'lib/trackplot/color_scale.rb', line 46

def categorical(hex, count: 8)
  validate_hex!(hex)
  return [] if count == 0

  h, s, l = hex_to_hsl(hex)
  step = 360.0 / count

  (0...count).map do |i|
    hue = (h + step * i) % 360
    hsl_to_hex(hue, s, l)
  end
end

.diverging(hex1, hex2, count: 8) ⇒ Object

Two-color gradient with parabolic lightness curve peaking at 0.95 at midpoint.



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# File 'lib/trackplot/color_scale.rb', line 23

def diverging(hex1, hex2, count: 8)
  validate_hex!(hex1)
  validate_hex!(hex2)
  return [] if count == 0

  h1, s1, _ = hex_to_hsl(hex1)
  h2, s2, _ = hex_to_hsl(hex2)

  if count == 1
    return [hsl_to_hex(lerp_hue(h1, h2, 0.5), lerp(s1, s2, 0.5), 0.95)]
  end

  (0...count).map do |i|
    t = i.to_f / (count - 1)
    h = lerp_hue(h1, h2, t)
    s = lerp(s1, s2, t)
    # Parabolic curve: l = 0.95 at t=0.5, dropping to ~0.35 at edges
    l = 0.95 - 2.4 * (t - 0.5)**2
    hsl_to_hex(h, s, l)
  end
end

.sequential(hex, count: 8) ⇒ Object

Light-to-dark palette from a single base color. Extracts hue + saturation, varies lightness from 0.90 to 0.25.



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# File 'lib/trackplot/color_scale.rb', line 7

def sequential(hex, count: 8)
  validate_hex!(hex)
  return [] if count == 0

  h, s, _ = hex_to_hsl(hex)
  if count == 1
    return [hsl_to_hex(h, s, 0.5)]
  end

  (0...count).map do |i|
    l = lerp(0.90, 0.25, i.to_f / (count - 1))
    hsl_to_hex(h, s, l)
  end
end