Class: Color::GrayScale

Inherits:
Object
  • Object
show all
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"

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(g = 0) ⇒ GrayScale

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

Color::GrayScale.new(50)



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# File 'lib/color/grayscale.rb', line 40

def initialize(g = 0)
  @g = g / 100.0
end

Class Method Details

.from_fraction(g = 0) ⇒ 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 24

def self.from_fraction(g = 0)
  color = Color::GrayScale.new
  color.g = g
  color
end

.from_percent(g = 0) ⇒ 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 33

def self.from_percent(g = 0)
  Color::GrayScale.new(g)
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 184

def +(other)
  other = other.to_grayscale
  ng = self.dup
  ng.g += other.g
  ng
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 197

def -(other)
  other = other.to_grayscale 
  ng = self.dup
  ng.g -= other.g
  ng
end

#==(other) ⇒ Object

Compares the other colour to this one. The other colour will be converted to GreyScale before comparison, so the comparison between a GreyScale colour and a non-GreyScale colour will be approximate and based on the other colour’s #to_greyscale conversion. If there is no #to_greyscale conversion, this will raise an exception. This will report that two GreyScale values are equivalent if they are within COLOR_TOLERANCE of each other.



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# File 'lib/color/grayscale.rb', line 51

def ==(other)
  other = other.to_grayscale
  other.kind_of?(Color::GrayScale) and
  ((@g - other.g).abs <= Color::COLOR_TOLERANCE)
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 152

def brightness
  @g
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 94

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 101

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 82

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

#css_rgba ⇒ 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 88

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

#darken_by(percent) ⇒ Object

Darken the greyscale colour by the stated percent.



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

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 164

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 174

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 158

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 168

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 75

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

#inspect ⇒ Object 



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# File 'lib/color/grayscale.rb', line 204

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 123

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 59

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 65

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

#to_cmyk ⇒ Object

Convert the greyscale colour to CMYK.



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

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 117

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 146

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 112

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 138

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