Class: Color::GrayScale

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

Overview

A colour object representing shades of grey. Used primarily in PDF document creation.

Constant Summary collapse

PDF_FORMAT_STR =

The format of a DeviceGrey colour for PDF. In color-tools 2.0 this will be removed from this package and added back as a modification by the PDF::Writer package.

"%.3f %s"

Constants included from Color

COLOR_EPSILON, COLOR_TOLERANCE, COLOR_VERSION, GreyScale

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Color

#==, coerce, const_missing, equivalent?, #name, #names, #names=, near?, near_one?, near_one_or_more?, near_zero?, near_zero_or_less?, new, normalize, normalize_byte, normalize_to_range, normalize_word

Constructor Details

#initialize(g = 0, radix = 100.0, &block) ⇒ GrayScale

Creates a greyscale colour object from percentages 0..100.

Color::GrayScale.new(50)



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# File 'lib/color/grayscale.rb', line 30

def initialize(g = 0, radix = 100.0, &block) # :yields self:
  @g = Color.normalize(g / radix)
  block.call if block
end

Class Method Details

.from_fraction(g = 0, &block) ⇒ Object

Creates a greyscale colour object from fractional values 0..1.

Color::GreyScale.from_fraction(0.5)



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# File 'lib/color/grayscale.rb', line 15

def from_fraction(g = 0, &block)
  new(g, 1.0, &block)
end

.from_percent(g = 0, &block) ⇒ Object

Creates a greyscale colour object from percentages 0..100.

Color::GrayScale.from_percent(50)



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# File 'lib/color/grayscale.rb', line 22

def from_percent(g = 0, &block)
  new(g, &block)
end

Instance Method Details

#+(other) ⇒ Object

Adds another colour to the current colour. The other colour will be converted to grayscale before addition. This conversion depends upon a #to_grayscale method on the other colour.

The addition is done using the grayscale accessor methods to ensure a valid colour in the result.



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# File 'lib/color/grayscale.rb', line 167

def +(other)
  self.class.from_fraction(g + other.to_grayscale.g)
end

#-(other) ⇒ Object

Subtracts another colour to the current colour. The other colour will be converted to grayscale before subtraction. This conversion depends upon a #to_grayscale method on the other colour.

The subtraction is done using the grayscale accessor methods to ensure a valid colour in the result.



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# File 'lib/color/grayscale.rb', line 177

def -(other)
  self + (-other)
end

#-@ ⇒ Object 



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# File 'lib/color/grayscale.rb', line 189

def -@
  gs = self.dup
  gs.instance_variable_set(:@g, -g)
  gs
end

#brightness ⇒ Object

Returns the brightness value for this greyscale value; this is the greyscale value itself.



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# File 'lib/color/grayscale.rb', line 135

def brightness
  @g
end

#coerce(other) ⇒ Object

Coerces the other Color object to grayscale.



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# File 'lib/color/grayscale.rb', line 36

def coerce(other)
  other.to_grayscale
end

#css_hsl ⇒ Object

Present the colour as an HSL HTML/CSS colour string (e.g., “hsl(180, 25%, 35%)”). Note that this will perform a #to_hsl operation.



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# File 'lib/color/grayscale.rb', line 77

def css_hsl
  to_hsl.css_hsl
end

#css_hsla ⇒ Object

Present the colour as an HSLA (with alpha) HTML/CSS colour string (e.g., “hsla(180, 25%, 35%, 1)”). Note that this will perform a #to_hsl operation.



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# File 'lib/color/grayscale.rb', line 84

def css_hsla
  to_hsl.css_hsla
end

#css_rgb ⇒ Object

Present the colour as an RGB HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%)”).



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# File 'lib/color/grayscale.rb', line 65

def css_rgb
  "rgb(%3.2f%%, %3.2f%%, %3.2f%%)" % [ gray, gray, gray ]
end

#css_rgba(alpha = 1) ⇒ Object

Present the colour as an RGBA (with alpha) HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%, 1)”).



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# File 'lib/color/grayscale.rb', line 71

def css_rgba(alpha = 1)
  "rgba(%3.2f%%, %3.2f%%, %3.2f%%, %1.2f)" % [ gray, gray, gray, alpha ]
end

#darken_by(percent) ⇒ Object

Darken the greyscale colour by the stated percent.



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# File 'lib/color/grayscale.rb', line 112

def darken_by(percent)
  g = [@g - (@g * (percent / 100.0)), 0.0].max
  Color::GrayScale.from_fraction(g)
end

#g ⇒ Object

Returns the grayscale value as a fractional value of white in the range 0.0 .. 1.0.



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# File 'lib/color/grayscale.rb', line 147

def g
  @g
end

#g=(gg) ⇒ Object

Returns the grayscale value as a fractional value of white in the range 0.0 .. 1.0.



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# File 'lib/color/grayscale.rb', line 157

def g=(gg)
  @g = Color.normalize(gg)
end

#gray ⇒ Object Also known as: grey

Returns the grayscale value as a percentage of white (100% gray is white).



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# File 'lib/color/grayscale.rb', line 141

def gray
  @g * 100.0
end

#gray=(gg) ⇒ Object Also known as: grey=

Sets the grayscale value as a percentage of white.



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# File 'lib/color/grayscale.rb', line 151

def gray=(gg)
  @g = Color.normalize(gg / 100.0)
end

#html ⇒ Object

Present the colour as an HTML/CSS colour string.



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# File 'lib/color/grayscale.rb', line 58

def html
  gs = "%02x" % to_255
  "##{gs * 3}"
end

#inspect ⇒ Object 



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# File 'lib/color/grayscale.rb', line 181

def inspect
  "Gray [%.2f%%]" % [ gray ]
end

#lighten_by(percent) ⇒ Object

Lightens the greyscale colour by the stated percent.



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# File 'lib/color/grayscale.rb', line 106

def lighten_by(percent)
  g = [@g + (@g * (percent / 100.0)), 1.0].min
  Color::GrayScale.from_fraction(g)
end

#pdf_fill ⇒ Object

Present the colour as a DeviceGrey fill colour string for PDF. This will be removed from the default package in color-tools 2.0.



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# File 'lib/color/grayscale.rb', line 42

def pdf_fill
  PDF_FORMAT_STR % [ @g, "g" ]
end

#pdf_stroke ⇒ Object

Present the colour as a DeviceGrey stroke colour string for PDF. This will be removed from the default package in color-tools 2.0.



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# File 'lib/color/grayscale.rb', line 48

def pdf_stroke
  PDF_FORMAT_STR % [ @g, "G" ]
end

#to_a ⇒ Object 



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# File 'lib/color/grayscale.rb', line 185

def to_a
  [ g ]
end

#to_cmyk ⇒ Object

Convert the greyscale colour to CMYK.



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# File 'lib/color/grayscale.rb', line 89

def to_cmyk
  k = 1.0 - @g.to_f
  Color::CMYK.from_fraction(0, 0, 0, k)
end

#to_grayscale ⇒ Object Also known as: to_greyscale

Reflexive conversion.



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# File 'lib/color/grayscale.rb', line 100

def to_grayscale
  self
end

#to_hsl ⇒ Object

Returns the HSL colour encoding of the greyscale value.



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# File 'lib/color/grayscale.rb', line 129

def to_hsl
  Color::HSL.from_fraction(0, 0, @g)
end

#to_rgb(ignored = true) ⇒ Object

Convert the greyscale colour to RGB.



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# File 'lib/color/grayscale.rb', line 95

def to_rgb(ignored = true)
  Color::RGB.from_fraction(g, g, g)
end

#to_yiq ⇒ Object

Returns the YIQ (NTSC) colour encoding of the greyscale value. This is an approximation, as the values for I and Q are calculated by treating the greyscale value as an RGB value. The Y (intensity or brightness) value is the same as the greyscale value.



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# File 'lib/color/grayscale.rb', line 121

def to_yiq
  y = @g
  i = (@g * 0.596) + (@g * -0.275) + (@g * -0.321)
  q = (@g * 0.212) + (@g * -0.523) + (@g *  0.311)
  Color::YIQ.from_fraction(y, i, q)
end