colorizer_hsgd.lua

--[[
	Custom colorizer: Sine wave gradient with desaturation on \k event
	VSFilterMod v1.1 lua example

	Ass tag: {\blur5\fs40\hsvgrad(0,1)\t(\hsvgrad(1,0))\kf500}Custom colorizer
]]
require("karalib_color")
require("drawing")

function init()

end

function hsvgradient(line, rend)
	local x, y
	local cx = line.width / 2
	local cy = line.height / 2

	for x = 0, line.width - 1 do
	    for y = 0, line.height - 1 do
		local c
		if(line.layer == 1)then
			local t = math.cos(math.pi * (x / line.width + line.user.time / line.user.length))
			c = color.create_hsv(t,1,1)

			local dist = math.abs(x - line.gran)

				if(x < line.gran)then
					if(dist < 50)then
						c:desaturate(1 - dist / 50)
					end
				else
				    c:desaturate(1)
				end


			c = c:get_color()
		else
			c = line.c1
		end

	        rend:mix(x, y, c, 0xff)
	    end
	end
end

-- animable through \t
function hsvgrad(line,a,b)
	a = tonumber(a)
	b = tonumber(b)
	local r = {}
	r.renderer = "hsvgradient"
	if(line.animate == nul) then
		-- Save start coordinates
		r.user = line.user
		if(r.user == nul) then r.user = {time=line.time, length=line.length} end
		r.user.hsvgrad = { a = a, b = b }
	else
		assert(type(line.user)=="table", "hsvgrad(line,a,b): no valid argument 'line.user'")
		local t = line.animate

		r.user = line.user
		if(r.user.hsvgrad == nul) then r.user.hsvgrad = {a = 0, b = 0 } end

		r.user.hsvgrad.a = a * t + r.user.hsvgrad.a * (1 - t)
		r.user.hsvgrad.b = b * t + r.user.hsvgrad.b * (1 - t)
	end

	return r
end