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.
Attributes
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 23 def self.from_fraction(g = 0) color = Color::GrayScale.new color.g = g color end
Creates a greyscale colour object from percentages 0..100.
Color::GrayScale.new(50)
# File lib/color/grayscale.rb, line 32 def initialize(g = 0) @g = g / 100.0 end
Public Instance Methods
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 1e-4 (0.0001) of each other.
# File lib/color/grayscale.rb, line 43 def ==(other) other = other.to_grayscale other.kind_of?(Color::GrayScale) and ((@g - other.g).abs <= 1e-4) end
Returns the brightness value for this greyscale value; this is the greyscale value.
# File lib/color/grayscale.rb, line 119 def brightness @g end
Darken the RGB hue by the stated percent.
# File lib/color/grayscale.rb, line 96 def darken_by(percent) g = [@g - (@g * (percent / 100.0)), 0.0].max Color::GrayScale.from_fraction(g) end
Present the colour as an HTML/CSS colour string.
# File lib/color/grayscale.rb, line 67 def html gs = "%02x" % to_255 "##{gs * 3}" end
Lightens the greyscale colour by the stated percent.
# File lib/color/grayscale.rb, line 90 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 51 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 57 def pdf_stroke PDF_FORMAT_STR % [ @g, "G" ] end
Convert the greyscale colour to CMYK.
# File lib/color/grayscale.rb, line 73 def to_cmyk k = 1.0 - @g.to_f Color::CMYK.from_fraction(0, 0, 0, k) end
# File lib/color/grayscale.rb, line 84 def to_grayscale self end
Returns the HSL colour encoding of the greyscale value.
# File lib/color/grayscale.rb, line 113 def to_hsl Color::HSL.from_fraction(0, 0, @g) end
Convert the greyscale colour to RGB.
# File lib/color/grayscale.rb, line 79 def to_rgb(ignored = true) g = to_255 Color::RGB.new(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 105 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 61 def to_255 [(@g * 255).round, 255].min end