TRIAD mixer - mix colours like a painter | v0.1

Scripts & Extensions
1

mix three colours + black and white together.
triad-mixer--01
each slider represents an amount of ‘paint’ in the mix, so the result is ratio of all of them.
that means C1: 23 and C2: 23 will get you same mix as C1: 100 and C2: 100 etc.

note: alpha is ignored

tip: if you want to have wide range of both bright and dark mixes, make the C1 + C2 + C3 mix with lower values, so the w and k sliders can have bigger impact.
i’m thinking about replacing white and black with saturation and value for practical reasons.
we’ll see…

local dlgWin = Dialog{ title = "TRIAD MIXer v0.1" }  

dlgWin
	:color{ id = "c1",
		--label = "c1",
		color = Color{ h=0.0, s=1.0, l=0.5, a=255 } 
	}
	
	:color{ id = "c2",
		--label = "c2",
		color = Color{ h=60.0, s=1.0, l=0.5, a=255 } 
	}
	
	:color{ id = "c3",
		--label = "c3",
		color = Color{ h=210.0, s=1.0, l=0.5, a=255 } 
	}
	
	:slider{ id = "c1_val",
		label = "C1",
		min = 0,
		max = 100,
		value = 0, 
		onchange = function() 
			update( dlgWin ) 
		end
	}
	
	:slider{ id = "c2_val",
		label = "C2",
		min = 0,
		max = 100,
		value = 0, 
		onchange = function() 
			update( dlgWin ) 
		end
	}
	
	:slider{ id = "c3_val",
		label = "C3",
		min = 0,
		max = 100,
		value = 0, 
		onchange = function() 
			update( dlgWin ) 
		end
	}

	:slider{ id = "W",
		label = "w",
		min = 0,
		max = 100,
		value = 0, 
		onchange = function() 
			update( dlgWin ) 
		end
	}
	
	:slider{ id = "K",
		label = "k",
		min = 0,
		max = 100,
		value = 0, 
		onchange = function() 
			update( dlgWin ) 
		end
	}

	:color{ id = "c0",
		--label = "c0",
		color = Color{ h=0.0, s=0.0, l=0.5, a=255 } --app.Color 
	}

-- show dialog window 
dlgWin:show{ wait = false } 


function update( dlgWin ) 
	
	local dlgData = dlgWin.data 
	c1 = dlgData.c1 
	c2 = dlgData.c2 
	c3 = dlgData.c3 
	w = Color{ r=255, g=255, b=255, a=255 }
	k = Color{ r=0, g=0, b=0, a=255 }
	
	c1v2_r = ratio( dlgData.c1_val, dlgData.c2_val ) 
	c12v3_r = ratio( dlgData.c1_val + dlgData.c2_val, dlgData.c3_val ) 
	
	c_w = ratio( dlgData.c1_val + dlgData.c2_val + dlgData.c3_val, dlgData.W ) 
	cw_k = ratio( dlgData.c1_val + dlgData.c2_val + dlgData.c3_val + dlgData.W, dlgData.K ) 
	
	clr_c1v2_r = mix( c1, c2, c1v2_r ) 
	clr_c12v3_r = mix( clr_c1v2_r, c3, c12v3_r ) 
	clr_w = mix( clr_c12v3_r, w, c_w) 
	clrw_k = mix( clr_w, k, cw_k ) 
	
	dlgData.c0 = clrw_k 
	dlgWin.data = dlgData
	app.fgColor = dlgData.c0 
end


function ratio( a, b ) 
	
	local ratio 
	
	if ( a == b ) then 
		-- what if both values are equal to 0, huh? 
		ratio = 0.5 
	elseif ( a == 0 ) then 
		ratio = 1 
	elseif ( b == 0 ) then 
		ratio = 0 
	elseif ( a > b ) then 
		ratio = ( b / a ) / 2 
	elseif ( a < b ) then 
		ratio = 1 - (( a / b ) / 2 )
	end 
	
	return ratio 
	
end 


function mix( clr_1, clr_2, ratio ) 
	
	local newRed
	local newGreen
	local newBlue
	local newAlpha
	
	local mix = {
		red = (clr_1.red - clr_2.red),
		green = (clr_1.green - clr_2.green),
		blue = (clr_1.blue - clr_2.blue),
		alpha = (clr_1.alpha - clr_2.alpha)
	}
	
	newRed = clr_1.red - math.floor(mix.red * ratio) 
	newGreen = clr_1.green - math.floor(mix.green * ratio) 
	newBlue = clr_1.blue - math.floor(mix.blue * ratio) 
	newAlpha = clr_1.alpha - math.floor(mix.alpha * ratio) 
	
	newClr = Color{
		r = newRed, 
		g = newGreen, 
		b = newBlue, 
		a = 255 --newAlpha 
	}
	
	return newClr 
	
end
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