Module:Color contrast
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 | This Lua module is used on approximately 561,000 pages. To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Consider discussing changes on the talk page before implementing them. |
 | This module depends on the following other modules: |
This module is used primarily by
- {{Color contrast ratio}}
- {{RGBColorToLum}}
- {{Color contrast conformance}}
- {{Ensure AAA contrast ratio}}
- {{Ensure AA contrast ratio}}
- {{Greater color contrast ratio}}
It is also used for tracking within
and for documentation in
The formulas used are stated in WCAG 2.x specifications. WCAG is the main guideline for creating accessible interfaces on the web.
Usage
[edit]To use this module, you may use one of the above listed templates or invoke the module directly
- To compute relative luminescence:
{{RGBColorToLum|color}}or{{#invoke:Color contrast|lum|color}} - To compute a contrast ratio between two colors:
{{Color contrast ratio|color1|color2|error=?}}or{{#invoke:Color contrast|ratio|color1|color2|error=?}} - To determine which of two colors (color2a and color2b) has the greater contrast ratio with a particular color (color1):
{{Greater color contrast ratio|color1|color2a|color2b}}or{{#invoke:Color contrast|greatercontrast|color1|color2a|color2b}} - To compute the contrast ratio between the background and text colors specified in a css style string:
{{#invoke:Color contrast|styleratio|css style statement string|default background color|default text color}}
--
-- This module implements
-- {{Color contrast ratio}}
-- {{Greater color contrast ratio}}
-- {{ColorToLum}}
-- {{RGBColorToLum}}
--
local p = {}
local HTMLcolor = mw.loadData( 'Module:Color contrast/colors' )
local function sRGB (v)
if (v <= 0.03928) then
v = v / 12.92
else
v = math.pow((v+0.055)/1.055, 2.4)
end
return v
end
local function rgbdec2lum(R, G, B)
if ( 0 <= R and R < 256 and 0 <= G and G < 256 and 0 <= B and B < 256 ) then
return 0.2126 * sRGB(R/255) + 0.7152 * sRGB(G/255) + 0.0722 * sRGB(B/255)
else
return ''
end
end
local function hsl2lum(h, s, l)
if ( 0 <= h and h < 360 and 0 <= s and s <= 1 and 0 <= l and l <= 1 ) then
local c = (1 - math.abs(2*l - 1))*s
local x = c*(1 - math.abs( math.fmod(h/60, 2) - 1) )
local m = l - c/2
local r, g, b = m, m, m
if( 0 <= h and h < 60 ) then
r = r + c
g = g + x
elseif( 60 <= h and h < 120 ) then
r = r + x
g = g + c
elseif( 120 <= h and h < 180 ) then
g = g + c
b = b + x
elseif( 180 <= h and h < 240 ) then
g = g + x
b = b + c
elseif( 240 <= h and h < 300 ) then
r = r + x
b = b + c
elseif( 300 <= h and h < 360 ) then
r = r + c
b = b + x
end
return rgbdec2lum(255*r, 255*g, 255*b)
else
return ''
end
end
local function color2lum(c)
if (c == nil) then
return ''
end
-- html '#' entity
c = c:gsub("#", "#")
-- whitespace
c = c:match( '^%s*(.-)[%s;]*$' )
-- unstrip nowiki strip markers
c = mw.text.unstripNoWiki(c)
-- lowercase
c = c:lower()
-- first try to look it up
local L = HTMLcolor[c]
if (L ~= nil) then
return L
end
-- convert from hsl
if mw.ustring.match(c,'^hsl%([%s]*[0-9][0-9%.]*[%s]*,[%s]*[0-9][0-9%.]*%%[%s]*,[%s]*[0-9][0-9%.]*%%[%s]*%)$') then
local h, s, l = mw.ustring.match(c,'^hsl%([%s]*([0-9][0-9%.]*)[%s]*,[%s]*([0-9][0-9%.]*)%%[%s]*,[%s]*([0-9][0-9%.]*)%%[%s]*%)$')
return hsl2lum(tonumber(h), tonumber(s)/100, tonumber(l)/100)
end
-- convert from rgb
if mw.ustring.match(c,'^rgb%([%s]*[0-9][0-9]*[%s]*,[%s]*[0-9][0-9]*[%s]*,[%s]*[0-9][0-9]*[%s]*%)$') then
local R, G, B = mw.ustring.match(c,'^rgb%([%s]*([0-9][0-9]*)[%s]*,[%s]*([0-9][0-9]*)[%s]*,[%s]*([0-9][0-9]*)[%s]*%)$')
return rgbdec2lum(tonumber(R), tonumber(G), tonumber(B))
end
-- convert from rgb percent
if mw.ustring.match(c,'^rgb%([%s]*[0-9][0-9%.]*%%[%s]*,[%s]*[0-9][0-9%.]*%%[%s]*,[%s]*[0-9][0-9%.]*%%[%s]*%)$') then
local R, G, B = mw.ustring.match(c,'^rgb%([%s]*([0-9][0-9%.]*)%%[%s]*,[%s]*([0-9][0-9%.]*)%%[%s]*,[%s]*([0-9][0-9%.]*)%%[%s]*%)$')
return rgbdec2lum(255*tonumber(R)/100, 255*tonumber(G)/100, 255*tonumber(B)/100)
end
-- remove leading # (if there is one) and whitespace
c = mw.ustring.match(c, '^[%s#]*([a-f0-9]*)[%s]*$')
-- split into rgb
local cs = mw.text.split(c or '', '')
if( #cs == 6 ) then
local R = 16*tonumber('0x' .. cs[1]) + tonumber('0x' .. cs[2])
local G = 16*tonumber('0x' .. cs[3]) + tonumber('0x' .. cs[4])
local B = 16*tonumber('0x' .. cs[5]) + tonumber('0x' .. cs[6])
return rgbdec2lum(R, G, B)
elseif ( #cs == 3 ) then
local R = 16*tonumber('0x' .. cs[1]) + tonumber('0x' .. cs[1])
local G = 16*tonumber('0x' .. cs[2]) + tonumber('0x' .. cs[2])
local B = 16*tonumber('0x' .. cs[3]) + tonumber('0x' .. cs[3])
return rgbdec2lum(R, G, B)
end
-- failure, return blank
return ''
end
-- This exports the function for use in other modules.
-- The colour is passed as a string.
function p._lum(color)
return color2lum(color)
end
function p._greatercontrast(args)
local bias = tonumber(args['bias'] or '0') or 0
local css = (args['css'] and args['css'] ~= '') and true or false
local v1 = color2lum(args[1] or '')
local c2 = args[2] or 'white'
local v2 = color2lum(c2)
local c3 = args[3] or 'black'
local v3 = color2lum(c3)
local ratio1 = -1;
local ratio2 = -1;
if (type(v1) == 'number' and type(v2) == 'number') then
ratio1 = (v2 + 0.05)/(v1 + 0.05)
ratio1 = (ratio1 < 1) and 1/ratio1 or ratio1
end
if (type(v1) == 'number' and type(v3) == 'number') then
ratio2 = (v3 + 0.05)/(v1 + 0.05)
ratio2 = (ratio2 < 1) and 1/ratio2 or ratio2
end
if css then
local c1 = args[1] or ''
if mw.ustring.match(c1, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') or
mw.ustring.match(c1, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') then
c1 = '#' .. c1
end
if mw.ustring.match(c2, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') or
mw.ustring.match(c2, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') then
c2 = '#' .. c2
end
if mw.ustring.match(v3, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') or
mw.ustring.match(v3, '^[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]$') then
c3 = '#' .. c3
end
return 'background-color:' .. c1 .. '; color:' .. ((ratio1 > 0) and (ratio2 > 0) and ((ratio1 + bias > ratio2) and c2 or c3) or '') .. ';'
end
return (ratio1 > 0) and (ratio2 > 0) and ((ratio1 + bias > ratio2) and c2 or c3) or ''
end
function p._ratio(args)
local v1 = color2lum(args[1])
local v2 = color2lum(args[2])
if (type(v1) == 'number' and type(v2) == 'number') then
-- v1 should be the brighter of the two.
if v2 > v1 then
v1, v2 = v2, v1
end
return (v1 + 0.05)/(v2 + 0.05)
else
return args['error'] or '?'
end
end
function p._styleratio(args)
local style = (args[1] or ''):lower()
local bg, fg = 'white', 'black'
local lum_bg, lum_fg = 1, 0
if args[2] then
local lum = color2lum(args[2])
if lum ~= '' then bg, lum_bg = args[2], lum end
end
if args[3] then
local lum = color2lum(args[3])
if lum ~= '' then fg, lum_fg = args[3], lum end
end
local slist = mw.text.split(mw.ustring.gsub(mw.ustring.gsub(style or '', '&#[Xx]23;', '#'), '#', '#'), ';')
for k = 1,#slist do
local s = slist[k]
local k,v = s:match( '^[%s]*([^:]-):([^:]-)[%s;]*$' )
k = k or ''
v = v or ''
if (k:match('^[%s]*(background)[%s]*$') or k:match('^[%s]*(background%-color)[%s]*$')) then
local lum = color2lum(v)
if( lum ~= '' ) then bg, lum_bg = v, lum end
elseif (k:match('^[%s]*(color)[%s]*$')) then
local lum = color2lum(v)
if( lum ~= '' ) then bg, lum_fg = v, lum end
end
end
if lum_bg > lum_fg then
return (lum_bg + 0.05)/(lum_fg + 0.05)
else
return (lum_fg + 0.05)/(lum_bg + 0.05)
end
end
--[[
Use {{#invoke:Color contrast|somecolor}} directly or
{{#invoke:Color contrast}} from a wrapper template.
Parameters:
-- |1= — required; A color to check.
--]]
function p.lum(frame)
local color = frame.args[1] or frame:getParent().args[1]
return p._lum(color)
end
function p.ratio(frame)
local args = frame.args[1] and frame.args or frame:getParent().args
return p._ratio(args)
end
function p.styleratio(frame)
local args = frame.args[1] and frame.args or frame:getParent().args
return p._styleratio(args)
end
function p.greatercontrast(frame)
local args = frame.args[1] and frame.args or frame:getParent().args
return p._greatercontrast(args)
end
return p