class Color::GrayScale
A colour object representing shades of grey. Used primarily in PDF document creation.
Constants
- 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.
Public Class Methods
Creates a greyscale colour object from fractional values 0..1.
Color::GreyScale.from_fraction(0.5)
# File lib/color/grayscale.rb, line 15 def from_fraction(g = 0, &block) new(g, 1.0, &block) end
Creates a greyscale colour object from percentages 0..100.
Color::GrayScale.from_percent(50)
# File lib/color/grayscale.rb, line 22 def from_percent(g = 0, &block) new(g, &block) end
Creates a greyscale colour object from percentages 0..100.
Color::GrayScale.new(50)
# 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
Public Instance Methods
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.
# File lib/color/grayscale.rb, line 167 def +(other) self.class.from_fraction(g + other.to_grayscale.g) end
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.
# File lib/color/grayscale.rb, line 177 def -(other) self + (-other) end
# File lib/color/grayscale.rb, line 189 def -@ gs = self.dup gs.instance_variable_set(:@g, -g) gs end
Returns the brightness value for this greyscale value; this is the greyscale value itself.
# File lib/color/grayscale.rb, line 135 def brightness @g end
Coerces the other Color object to grayscale.
# File lib/color/grayscale.rb, line 36 def coerce(other) other.to_grayscale end
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.
# File lib/color/grayscale.rb, line 77 def css_hsl to_hsl.css_hsl end
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.
# File lib/color/grayscale.rb, line 84 def css_hsla to_hsl.css_hsla end
Present the colour as an RGB HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%)”).
# File lib/color/grayscale.rb, line 65 def css_rgb "rgb(%3.2f%%, %3.2f%%, %3.2f%%)" % [ gray, gray, gray ] end
Present the colour as an RGBA (with alpha) HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%, 1)”).
# 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 the greyscale colour by the stated percent.
# 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
Returns the grayscale value as a fractional value of white in the range 0.0 .. 1.0.
# File lib/color/grayscale.rb, line 147 def g @g end
Returns the grayscale value as a fractional value of white in the range 0.0 .. 1.0.
# File lib/color/grayscale.rb, line 157 def g=(gg) @g = Color.normalize(gg) end
Returns the grayscale value as a percentage of white (100% gray is white).
# File lib/color/grayscale.rb, line 141 def gray @g * 100.0 end
Sets the grayscale value as a percentage of white.
# File lib/color/grayscale.rb, line 151 def gray=(gg) @g = Color.normalize(gg / 100.0) end
Present the colour as an HTML/CSS colour string.
# File lib/color/grayscale.rb, line 58 def html gs = "%02x" % to_255 "##{gs * 3}" end
# File lib/color/grayscale.rb, line 181 def inspect "Gray [%.2f%%]" % [ gray ] end
Lightens the greyscale colour by the stated percent.
# 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
Present the colour as a DeviceGrey fill colour string for PDF. This will be removed from the default package in color-tools 2.0.
# File lib/color/grayscale.rb, line 42 def pdf_fill PDF_FORMAT_STR % [ @g, "g" ] end
Present the colour as a DeviceGrey stroke colour string for PDF. This will be removed from the default package in color-tools 2.0.
# File lib/color/grayscale.rb, line 48 def pdf_stroke PDF_FORMAT_STR % [ @g, "G" ] end
# File lib/color/grayscale.rb, line 185 def to_a [ g ] end
Convert the greyscale colour to CMYK.
# 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
Reflexive conversion.
# File lib/color/grayscale.rb, line 100 def to_grayscale self end
Returns the HSL colour encoding of the greyscale value.
# File lib/color/grayscale.rb, line 129 def to_hsl Color::HSL.from_fraction(0, 0, @g) end
Convert the greyscale colour to RGB.
# File lib/color/grayscale.rb, line 95 def to_rgb(ignored = true) Color::RGB.from_fraction(g, g, g) end
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.
# 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
Private Instance Methods
# File lib/color/grayscale.rb, line 52 def to_255 [(@g * 255).round, 255].min end