# Module:Color contrast

---
-- This module implements
---
---
---
---
---
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("&#35;", "#")  
-- 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;', '#'), '&#35;', '#'), ';')
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  
--1= — required; A color to check.
---
function p.lum
local color = .args[1] or :getParent.args[1]
return p._lum(color)
end  
function p.ratio
local args = .args[1] and .args or :getParent.args
return p._ratio(args)
end  
function p.styleratio
local args = .args[1] and .args or :getParent.args
return p._styleratio(args)
end  
function p.greatercontrast
local args = .args[1] and .args or :getParent.args
return p._greatercontrast(args)
end  
return p