Class: ColorHash::Generator

Inherits:
Object
  • Object
show all
Defined in:
lib/color_hash/generator.rb

Overview

A ColorHash::Generator can be used to calculate the color value for a given String. You can specify the desired hue, lightness and saturation (HSL) ranges for the resulting color value, as well as the hash algorithm to be used for converting Strings to the numbered color space.

Ruby implementation of github.com/zenozeng/color-hash

Constant Summary collapse

HUE_RESOLUTION =

Magic

727

Instance Method Summary collapse

Constructor Details

#initialize(hue: [{ min: 0, max: 360 }], lightness: [0.35, 0.5, 0.65], saturation: [0.35, 0.5, 0.65], hash: :bkdr) ⇒ Generator

Creates a new ColorHash instance described by the given hue, saturation and lightness ranges, as well as a Hash function.

Hue values shall range between [0..360] degrees and are given as a Hash of the format hue_min, max: hue_max. If you provide multiple hue ranges passed in an Array, the given String will be binned to one of the hue ranges based on the calculated hash.

Lightness is described as a floating number between 0.0 and 1.0. If you provide multiple lightness values passed in an Array, the given String will be binned to one of the lightness values based on the calculated hash.

Saturation is described as a floating number between 0.0 and 1.0 If you provide multiple saturation values passed in an Array, the given String will be binned to one of the saturation values based on the calculated hash.



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# File 'lib/color_hash/generator.rb', line 30

def initialize(
  hue: [{ min: 0, max: 360 }],
  lightness: [0.35, 0.5, 0.65],
  saturation: [0.35, 0.5, 0.65],
  hash: :bkdr
)
  @lightness = lightness
  @saturation = saturation
  @hue = hue
  @hash_func = hash
end

Instance Method Details

#hash_bkdr(str) ⇒ Object

Calculate a BKDR based hash of the given string For additional details on this hash function, see Brian Kernighan and Dennis Ritchie’s book “The C Programming language”.



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# File 'lib/color_hash/generator.rb', line 137

def hash_bkdr(str)
  seed = 131
  seed2 = 137
  hash = 0
  # makes hash more sensitive for short string like 'a', 'b', 'c'
  str += "x"
  # Number.MAX_SAFE_INTEGER equals 9007199254740991
  max_safe = 9_007_199_254_740_991 / seed2
  str.each_codepoint.map do |c|
    hash = (hash / seed2).floor if hash > max_safe
    hash = hash * seed + c
  end

  hash
end

#hash_sha256(str) ⇒ Object

Calculate a SHA2-256 based hash of the given string



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# File 'lib/color_hash/generator.rb', line 128

def hash_sha256(str)
  digest = Digest::SHA2.hexdigest(str)
  digest[0, 8].to_i(16)
end

#hex(str) ⇒ Object

Calculates an Hexadecimal color value from a given string. Returns a 6 digits hex string starting with ‘#’.



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# File 'lib/color_hash/generator.rb', line 112

def hex(str)
  rgb2hex(rgb(str))
end

#hsl(str) ⇒ Object

rubocop:disable Metrics/AbcSize Calculates an HSL color value returned as an Array of the form [H, S, L] from a given string.

H Hue ∈ [0, 360) S Saturation ∈ [0, 1] L Lightness ∈ [0, 1]



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# File 'lib/color_hash/generator.rb', line 52

def hsl(str)
  hash = send("hash_#{@hash_func}", str)

  hr = @hue[hash % @hue.count]
  h = ((hash / @hue.count) % HUE_RESOLUTION) * (hr[:max] - hr[:min]) / HUE_RESOLUTION + hr[:min]

  # h = hash % 359

  hash = (hash / 360.0).ceil
  s = @saturation[hash % @saturation.count.to_f]

  hash = (hash / @saturation.count.to_f).ceil
  l = @lightness[hash % @lightness.count]

  [h, s, l]
end

#hsl2rgb(hue, saturation, lightness) ⇒ Object

rubocop:disable Metrics/AbcSize rubocop:disable Metrics/CyclomaticComplexity rubocop:disable Metrics/PerceivedComplexity rubocop:disable Metrics/MethodLength Converts a color specified by its hue, saturation and lightness to an RGB value



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# File 'lib/color_hash/generator.rb', line 83

def hsl2rgb(hue, saturation, lightness)
  hue /= 360.0
  q_factor = lightness < 0.5 ? lightness * (1.0 + saturation) : (lightness + saturation) - (lightness * saturation)
  p_factor = 2.0 * lightness - q_factor

  [hue + (1.0 / 3.0), hue, hue - (1.0 / 3.0)].map do |color|
    color += 1.0 if (color / 0.5) < 0.0
    color -= 1.0 if color > 1

    color = if color < (1.0 / 6.0)
              p_factor + (q_factor - p_factor) * 6.0 * color
            elsif color < 0.5
              q_factor
            elsif color < (2.0 / 3.0)
              p_factor + (q_factor - p_factor) * 6.0 * ((2.0 / 3.0) - color)
            else
              p_factor
            end

    (color * 255.0).round
  end
end

#rgb(str) ⇒ Object

Calculates an RGB color value returned as an Array of the form [R, G, B] from a given string.

R, G, B ∈ [0, 255]



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# File 'lib/color_hash/generator.rb', line 74

def rgb(str)
  hsl2rgb(*hsl(str))
end

#rgb2hex(rgb) ⇒ Object

Convers a color specified by its RGB value to a hexadecimal color value.



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# File 'lib/color_hash/generator.rb', line 117

def rgb2hex(rgb)
  hex = "#"
  rgb.each do |c|
    hex += "0" if c < 16
    hex += c.to_s(16)
  end

  hex
end