Class: Color::CMYK

Inherits:
Data
  • Object
show all
Includes:
Color
Defined in:
lib/color/cmyk.rb,
lib/color.rb

Overview

The CMYK color model is a subtractive color model based on additive percentages of colored inks: cyan, magenta, yellow, and key (most often black).

CMYK [30% 0% 80% 30%] would be mixed from 30% cyan, 0% magenta, 80% yellow, and 30% black.

CMYK colors are immutable Data class instances. Array deconstruction is ‘[cyan, magenta, yellow, key]` and hash deconstruction is `cyan:, m:, magenta:, y:, yellow: k:, key:`. See #c, #cyan, #m, #magenta, #y, #yellow, #k, #key.

Constant Summary

Constants included from Color

EPSILON, TOLERANCE, VERSION

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Color

#==, #css_value, #map, #map_with, normalize, #scale, translate_range, #zip

Constructor Details

#initialize(c:, m:, y:, k:) ⇒ CMYK

Creates a CMYK color object from fractional values (0.0 .. 1.0).

“‘ruby Color::CMYK.from_fraction(0.3, 0, 0.8, 0.3) # => CMYK [30.00% 0.00% 80.00% 30.00%] Color::CMYK.new(0.3, 0, 0.8, 0.3) # => CMYK [30.00% 0.00% 80.00% 30.00%] Color::CMYK[c: 0.3, m: 0, y: 0.8, k: 0.3] # => CMYK [30.00% 0.00% 80.00% 30.00%] “`



98
99
100
 
# File 'lib/color/cmyk.rb', line 98

def initialize(c:, m:, y:, k:)
  super(c: normalize(c), m: normalize(m), y: normalize(y), k: normalize(k))
end

Instance Attribute Details

#c ⇒ Object (readonly)

Returns the value of attribute c

Returns:

  • (Object) —

    the current value of c



45
46
47
 
# File 'lib/color.rb', line 45

def c
  @c
end

#k ⇒ Object (readonly) Also known as: b

Returns the value of attribute k

Returns:

  • (Object) —

    the current value of k



45
46
47
 
# File 'lib/color.rb', line 45

def k
  @k
end

#m ⇒ Object (readonly)

Returns the value of attribute m

Returns:

  • (Object) —

    the current value of m



45
46
47
 
# File 'lib/color.rb', line 45

def m
  @m
end

#y ⇒ Object (readonly)

Returns the value of attribute y

Returns:

  • (Object) —

    the current value of y



45
46
47
 
# File 'lib/color.rb', line 45

def y
  @y
end

Class Method Details

.from_percentage(*args, **kwargs) ⇒ Object Also known as: from_values

Creates a CMYK color object from percentage values (0.0 .. 100.0).

“‘ruby Color::CMYK.from_percentage(30, 0, 80, 30) # => CMYK [30.00% 0.00% 80.00% 30.00%] Color::CMYK.from_values(30, 0, 80, 30) # => CMYK [30.00% 0.00% 80.00% 30.00%] “`

:call-seq:

from_percentage(c, m, y, k)
from_percentage(c:, m:, y:, k:)
from_values(c, m, y, k)
from_values(c:, m:, y:, k:)



69
70
71
72
73
74
75
76
77
78
79
80
81
 
# File 'lib/color/cmyk.rb', line 69

def self.from_percentage(*args, **kwargs)
  c, m, y, k =
    case [args, kwargs]
    in [[_, _, _, _], {}]
      args
    in [[], {c:, m:, y:, k:}]
      [c, m, y, k]
    else
      new(*args, **kwargs)
    end

  new(c: c / 100.0, m: m / 100.0, y: y / 100.0, k: k / 100.0)
end

Instance Method Details

#coerce(other) ⇒ Object

Coerces the other Color object into CMYK.



168
 
# File 'lib/color/cmyk.rb', line 168

def coerce(other) = other.to_cmyk

#components ⇒ Object

:nodoc:



300
 
# File 'lib/color/cmyk.rb', line 300

def components = 4 # :nodoc:

#css(alpha: nil, fallback: true) ⇒ Object

Output a CSS representation of the CMYK color using ‘device-cmyk()`.

If an ‘alpha` value is provided, it will be included in the output.

A ‘fallback` may be provided or included automatically depending on the value provided, which may be `true`, `false`, a Color object, or a Hash with `:color` and/or `:alpha` keys. The default value is `true`.

When ‘fallback` is:

  • ‘true`: this CMYK color will be converted to RGB and this will be provided as the fallback color. If an `alpha` value is provided, it will be used for the fallback.

  • ‘false`: no fallback color will be included.

  • a Color object will be used to produce the ‘fallback` value.

  • a Hash will be checked for ‘:color` and/or `:alpha` keys:

    • if ‘:color` is present, it will be used for the fallback color; if not present, the CMYK color will be converted to RGB.

    • if ‘:alpha` is present, it will be used for the fallback color; if not present, the fallback color will be presented without alpha.

Examples:

“‘ruby cmyk = Color::CMYK.from_percentage(30, 0, 80, 30) cmyk.css # => device-cmyk(30.00% 0 80.00% 30.00%, rgb(49.00% 70.00% 14.00%))

cmyk.css(alpha: 0.5) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50, rgb(49.00% 70.00% 14.00% / 0.50))

cmyk.css(fallback: false) # => device-cmyk(30.00% 0 80.00% 30.00%)

cmyk.css(alpha: 0.5, fallback: false) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50)

cmyk.css(fallback: Color::RGB::Blue) # => device-cmyk(30.00% 0 80.00% 30.00%, rgb(0.00% 0.00% 100.00%))

cmyk.css(alpha: 0.5, fallback: Color::RGB::Blue) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50, rgb(0.00% 0.00% 100.00% / 0.50))

cmyk.css(alpha: 0.5, fallback: { color: Color::RGB::Blue }) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50, rgb(0.00% 0.00% 100.00%))

cmyk.css(alpha: 0.5, fallback: { color: Color::RGB::Blue, alpha: 0.3 }) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50, rgb(0.00% 0.00% 100.00% / 0.30))

cmyk.css(alpha: 0.5, fallback: { alpha: 0.3 }) # => device-cmyk(30.00% 0 80.00% 30.00% / 0.50, rgb(49.00% 70.00% 14.00% / 0.30)) “‘



154
155
156
157
158
159
160
161
162
163
164
 
# File 'lib/color/cmyk.rb', line 154

def css(alpha: nil, fallback: true)
  if fallback.is_a?(Color)
    device_cmyk(alpha, fallback, alpha)
  elsif fallback.is_a?(Hash)
    device_cmyk(alpha, fallback.fetch(:color) { to_rgb }, fallback[:alpha])
  elsif fallback == true
    device_cmyk(alpha, to_rgb, alpha)
  else
    device_cmyk(alpha, nil, nil)
  end
end

#cyan ⇒ Object

:nodoc:



270
 
# File 'lib/color/cmyk.rb', line 270

def cyan = c * 100.0 # :nodoc:

#deconstruct_keys(_keys) ⇒ Object

:nodoc:



294
 
# File 'lib/color/cmyk.rb', line 294

def deconstruct_keys(_keys) = {c:, m:, y:, k:, cyan:, magenta:, yellow:, key:} # :nodoc:

#inspect ⇒ Object

:nodoc:



251
 
# File 'lib/color/cmyk.rb', line 251

def inspect = "CMYK [%.2f%% %.2f%% %.2f%% %.2f%%]" % [cyan, magenta, yellow, key] # :nodoc:

#key ⇒ Object Also known as: black

:nodoc:



282
 
# File 'lib/color/cmyk.rb', line 282

def key = k * 100.0 # :nodoc:

#magenta ⇒ Object

:nodoc:



273
 
# File 'lib/color/cmyk.rb', line 273

def magenta = m * 100.0 # :nodoc:

#pretty_print(q) ⇒ Object

:nodoc:



254
255
256
257
258
259
260
261
262
263
264
265
266
267
 
# File 'lib/color/cmyk.rb', line 254

def pretty_print(q) # :nodoc:
  q.text "CMYK"
  q.breakable
  q.group 2, "[", "]" do
    q.text ".2f%%" % cyan
    q.fill_breakable
    q.text ".2f%%" % magenta
    q.fill_breakable
    q.text ".2f%%" % yellow
    q.fill_breakable
    q.text ".2f%%" % key
    q.fill_breakable
  end
end

#to_a ⇒ Object Also known as: deconstruct

:nodoc:



288
 
# File 'lib/color/cmyk.rb', line 288

def to_a = [cyan, magenta, yellow, key] # :nodoc:

#to_cmyk ⇒ Object 



171
 
# File 'lib/color/cmyk.rb', line 171

def to_cmyk(...) = self

#to_grayscale ⇒ Object

Converts CMYK to Color::Grayscale.

There are multiple methods for grayscale conversion, but this implements a variant of the Adobe PDF conversion method with higher precision:

“‘ g = 1.0 - min(1.0, 0.299 * c + 0.587 * m + 0.114 * y + k) “`

The default Adobe conversion uses lower precision conversion constants (0.3, 0.59, and 0.11) instead of the more precise NTSC/YIQ values.



185
186
187
188
189
190
191
 
# File 'lib/color/cmyk.rb', line 185

def to_grayscale(...)
  gc = 0.299 * c
  gm = 0.587 * m
  gy = 0.114 * y
  g = 1.0 - [1.0, gc + gm + gy + k].min
  Color::Grayscale.from_fraction(g)
end

#to_hsl ⇒ Object

Converts CMYK to Color::HSL via Color::RGB.



240
 
# File 'lib/color/cmyk.rb', line 240

def to_hsl(...) = to_rgb(...).to_hsl(...)

#to_internal ⇒ Object

:nodoc:



297
 
# File 'lib/color/cmyk.rb', line 297

def to_internal = [c, m, y, k] # :nodoc:

#to_lab ⇒ Object

Converts CMYK to Color::CIELAB via Color::RGB.



244
 
# File 'lib/color/cmyk.rb', line 244

def to_lab(...) = to_rgb(...).to_lab(...)

#to_rgb(*args, **kwargs) ⇒ Object

Converts CMYK to Color::RGB.

Most color experts strongly suggest that this is not a good idea (some suggesting that it’s a very bad idea). CMYK represents additive percentages of inks on white paper, whereas RGB represents mixed color intensities on an unlit (black) screen.

The color conversion can be done and there are two different methods (standard and Adobe PDF) that provide slightly different results. Using CMYK [33% 66% 83% 25%], the standard method provides an approximate RGB color of (128, 65, 33) or #804121. The Adobe PDF method provides an approximate RGB color of (107, 23, 0) or #6b1700.

Which is correct? The colors may seem to be drastically different in the RGB color space, they differ mostly in intensity. The Adobe PDF conversion is a darker, slightly redder brown; the standard conversion is a lighter brown. Because of this subtlety, both methods are offered for conversion. The Adobe PDF method is not used by default; to use it, pass ‘rgb_method: :adobe` to #to_rgb.

# Adobe PDF CMYK -> RGB Conversion
r = 1.0 - min(1.0, c + k)
g = 1.0 - min(1.0, m + k)
b = 1.0 - min(1.0, y + k)

# Standard CMYK -> RGB Conversion
r = 1.0 - (c * (1.0 - k) + k)
g = 1.0 - (m * (1.0 - k) + k)
b = 1.0 - (y * (1.0 - k) + k)

:call-seq:

to_rgb(rgb_method: :standard)



227
228
229
230
231
232
233
234
235
236
 
# File 'lib/color/cmyk.rb', line 227

def to_rgb(*args, **kwargs)
  values =
    if kwargs[:rgb_method] == :adobe || args.first == :adobe
      adobe_cmyk_rgb
    else
      standard_cmyk_rgb
    end

  Color::RGB.from_fraction(*values)
end

#to_xyz ⇒ Object

Converts CMYK to Color::XYZ via Color::RGB.



248
 
# File 'lib/color/cmyk.rb', line 248

def to_xyz(...) = to_rgb(...).to_xyz(...)

#to_yiq ⇒ Object

Converts CMYK to Color::YIQ via Color::RGB.



195
 
# File 'lib/color/cmyk.rb', line 195

def to_yiq(...) = to_rgb(...).to_yiq(...)

#yellow ⇒ Object

:nodoc:



276
 
# File 'lib/color/cmyk.rb', line 276

def yellow = y * 100.0 # :nodoc: