Class: Color::Palette::MonoContrast
- Inherits:
-
Object
- Object
- Color::Palette::MonoContrast
- Defined in:
- lib/color/palette/monocontrast.rb
Overview
Generates a monochromatic constrasting colour palette for background and foreground. What does this mean?
Monochromatic: A single colour is used to generate the base palette, and this colour is lightened five times and darkened five times to provide eleven distinct colours.
Contrasting: The foreground is also generated as a monochromatic colour palettte; however, all generated colours are tested to see that they are appropriately contrasting to ensure maximum readability of the foreground against the background.
Instance Attribute Summary collapse
-
#background ⇒ Object
Hash of CSS background colour values.
-
#foreground ⇒ Object
Hash of CSS foreground colour values.
-
#minimum_brightness_diff ⇒ Object
The minimum brightness difference between the background and the foreground.
-
#minimum_color_diff ⇒ Object
The minimum colour difference between the background and the foreground.
Instance Method Summary collapse
-
#brightness_diff(c1, c2) ⇒ Object
Returns the absolute difference between the brightness levels of two colours.
-
#calculate_foreground(background, foreground) ⇒ Object
Given a background colour and a foreground colour, modifies the foreground colour so that it will have enough contrast to be seen against the background colour.
-
#color_diff(c1, c2) ⇒ Object
Returns the contrast between to colours, a decimal value between 0 and 3.
-
#initialize(background, foreground = nil) ⇒ MonoContrast
constructor
Generate the initial palette.
-
#regenerate(background, foreground = nil) ⇒ Object
Generate the colour palettes.
Constructor Details
#initialize(background, foreground = nil) ⇒ MonoContrast
Generate the initial palette.
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# File 'lib/color/palette/monocontrast.rb', line 58 def initialize(background, foreground = nil) @minimum_brightness_diff = 125 / 255.0 @minimum_color_diff = 500 / 765.0 regenerate(background, foreground) end |
Instance Attribute Details
#background ⇒ Object
Hash of CSS background colour values.
This is always 11 values:
- 0
-
The starting colour.
- 1..5
-
Lighter colours.
- -1..-5
-
Darker colours.
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# File 'lib/color/palette/monocontrast.rb', line 29 def background @background end |
#foreground ⇒ Object
Hash of CSS foreground colour values.
This is always 11 values:
- 0
-
The starting colour.
- 1..5
-
Lighter colours.
- -1..-5
-
Darker colours.
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# File 'lib/color/palette/monocontrast.rb', line 37 def foreground @foreground end |
#minimum_brightness_diff ⇒ Object
The minimum brightness difference between the background and the foreground. Setting this value will regenerate the palette based on the base colours. The default value for this is 125 / 255.0.
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# File 'lib/color/palette/monocontrast.rb', line 42 def minimum_brightness_diff @minimum_brightness_diff end |
#minimum_color_diff ⇒ Object
The minimum colour difference between the background and the foreground. Setting this value will regenerate the palette based on the base colours.
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# File 'lib/color/palette/monocontrast.rb', line 51 def minimum_color_diff @minimum_color_diff end |
Instance Method Details
#brightness_diff(c1, c2) ⇒ Object
Returns the absolute difference between the brightness levels of two colours. This will be a decimal value between 0 and 1. W3C accessibility guidelines for colour contrast suggest that this value be at least approximately 0.49 (125 / 255.0) for proper contrast.
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# File 'lib/color/palette/monocontrast.rb', line 136 def brightness_diff(c1, c2) (c1.brightness - c2.brightness).abs end |
#calculate_foreground(background, foreground) ⇒ Object
Given a background colour and a foreground colour, modifies the foreground colour so that it will have enough contrast to be seen against the background colour.
Uses #mininum_brightness_diff and #minimum_color_diff.
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# File 'lib/color/palette/monocontrast.rb', line 104 def calculate_foreground(background, foreground) nfg = nil # Loop through brighter and darker versions of the foreground color. # The numbers here represent the amount of foreground color to mix # with black and white. [100, 75, 50, 25, 0].each do |percent| dfg = foreground.darken_by(percent) lfg = foreground.lighten_by(percent) dbd = brightness_diff(background, dfg) lbd = brightness_diff(background, lfg) if lbd > dbd nfg = lfg nbd = lbd else nfg = dfg nbd = dbd end ncd = color_diff(background, nfg) break if nbd >= @minimum_brightness_diff and ncd >= @minimum_color_diff end nfg end |
#color_diff(c1, c2) ⇒ Object
Returns the contrast between to colours, a decimal value between 0 and
-
W3C accessibility guidelines for colour
contrast suggest that this value be at least approximately 1.96 (500 / 765.0) for proper contrast.
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# File 'lib/color/palette/monocontrast.rb', line 144 def color_diff(c1, c2) r = (c1.r - c2.r).abs g = (c1.g - c2.g).abs b = (c1.b - c2.b).abs r + g + b end |
#regenerate(background, foreground = nil) ⇒ Object
Generate the colour palettes.
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# File 'lib/color/palette/monocontrast.rb', line 66 def regenerate(background, foreground = nil) foreground ||= background background = background.to_rgb foreground = foreground.to_rgb @background = {} @foreground = {} @background[-5] = background.darken_by(10) @background[-4] = background.darken_by(25) @background[-3] = background.darken_by(50) @background[-2] = background.darken_by(75) @background[-1] = background.darken_by(85) @background[ 0] = background @background[+1] = background.lighten_by(85) @background[+2] = background.lighten_by(75) @background[+3] = background.lighten_by(50) @background[+4] = background.lighten_by(25) @background[+5] = background.lighten_by(10) @foreground[-5] = calculate_foreground(@background[-5], foreground) @foreground[-4] = calculate_foreground(@background[-4], foreground) @foreground[-3] = calculate_foreground(@background[-3], foreground) @foreground[-2] = calculate_foreground(@background[-2], foreground) @foreground[-1] = calculate_foreground(@background[-1], foreground) @foreground[ 0] = calculate_foreground(@background[ 0], foreground) @foreground[+1] = calculate_foreground(@background[+1], foreground) @foreground[+2] = calculate_foreground(@background[+2], foreground) @foreground[+3] = calculate_foreground(@background[+3], foreground) @foreground[+4] = calculate_foreground(@background[+4], foreground) @foreground[+5] = calculate_foreground(@background[+5], foreground) end |