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+--[[
+
+Sample script for OverLua
+ - advanced karaoke effect, Prism Ark OP kara effect for Anime-Share Fansubs
+ 
+Given into the public domain.
+(You can do anything you want with this file, with no restrictions whatsoever.
+ You don't get any warranties of any kind either, though.)
+ 
+Originally authored by Niels Martin Hansen.
+
+Not an extremely advanced effect, but showcases improved parsing of ASS files
+and using information from the Style lines for the styling information.
+
+Pretty fast to render at SD resolutions.
+
+As for other effects, please consider that it's not much fun to just re-use
+an effect someone else wrote, especially not verbatim. If you elect to use
+this sample for something, I ask you to do something original with it. I
+can't force you, but please :)
+
+I'm leaving several sections of this script mostly unexplained, because I've
+for a large part copied those from the Gundam 00 OP 1 effect (sample3) I did
+a few days before this one.
+Please see sample3.lua for explanations of those, if you need them.
+
+]]
+
+---- START CONFIGURATION ----
+
+-- Duration of line fade-in/outs, in seconds
+local line_fade_duration = 0.5
+-- Minimum duration of highlights, also seconds
+local syl_highlight_duration = 0.5
+
+---- END CONFIGURATION ----
+
+
+-- Trim spaces from beginning and end of string
+function string.trim(s)
+	return (string.gsub(s, "^%s*(.-)%s*$", "%1"))
+end
+
+
+-- Script and video resolutions
+local sres_x, sres_y
+local vres_x, vres_y
+
+-- Stuff read from style definitions
+local font_name = {}
+local font_size = {}
+local font_bold = {}
+local font_italic = {}
+local pos_v = {}
+local vertical = {}
+local color1, color2, color3, color4 = {}, {}, {}, {}
+
+-- Input lines
+local lines = {}
+
+
+-- Read input file
+function read_field(ass_line, num)
+	local val, rest = ass_line:match("(.-),(.*)")
+	if not rest then
+		return ass_line, ""
+	elseif num > 1 then
+		return val, read_field(rest, num-1)
+	else
+		return val, rest
+	end
+end
+function parsenum(str)
+	return tonumber(str) or 0
+end
+function parse_ass_time(ass)
+	local h, m, s, cs = ass:match("(%d+):(%d+):(%d+)%.(%d+)")
+	return parsenum(cs)/100 + parsenum(s) + parsenum(m)*60 + parsenum(h)*3600
+end
+function parse_style_color(color)
+	local res = {r = 0, g = 0, b = 0, a = 0}
+	local a, b, g, r = color:match("&H(%x%x)(%x%x)(%x%x)(%x%x)")
+	res.r = tonumber(r, 16) / 255
+	res.g = tonumber(g, 16) / 255
+	res.b = tonumber(b, 16) / 255
+	res.a = 1 - tonumber(a, 16) / 255 -- Alpha has inverse meaning in ASS and cairo
+	return res
+end
+
+function parse_k_timing(text, start_time)
+	local syls = {}
+	local cleantext = ""
+	local i = 1
+	local curtime = start_time
+	for timing, syltext in text:gmatch("{\\k(%d+)}([^{]*)") do
+		local syl = {}
+		syl.dur = parsenum(timing)/100
+		syl.text = syltext
+		syl.i = i
+		syl.start_time = curtime
+		syl.end_time = curtime + syl.dur
+		table.insert(syls, syl)
+		cleantext = cleantext .. syl.text
+		i = i + 1
+		curtime = curtime + syl.dur
+	end
+	if cleantext == "" then
+		cleantext = text
+	end
+	return syls, cleantext
+end
+
+function read_input_file(name)
+	for line in io.lines(name) do
+		-- Try PlayResX/PlayResY
+		local playresx = line:match("^PlayResX: (.*)")
+		if playresx then
+			sres_x = parsenum(playresx)
+		end
+		local playresy = line:match("^PlayResY: (.*)")
+		if playresy then
+			sres_y = parsenum(playresy)
+		end
+	
+		-- Try dialogue line
+		-- Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
+		local dialogue_line = line:match("^Dialogue:(.*)")
+		if dialogue_line then
+			local layer, start_time, end_time, style, actor, margin_l, margin_r, margin_v, effect, text = read_field(dialogue_line, 9)
+			local ls = {}
+			ls.layer = parsenum(layer)
+			ls.start_time = parse_ass_time(start_time)
+			ls.end_time = parse_ass_time(end_time)
+			ls.style = style:trim()
+			ls.actor = actor:trim()
+			ls.effect = effect:trim()
+			ls.rawtext = text
+			ls.kara, ls.cleantext = parse_k_timing(text, ls.start_time)
+			
+			table.insert(lines, ls)
+		end
+
+		-- Try style line
+		-- Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
+		local style_line = line:match("^Style:(.*)")
+		if style_line then
+			local name, font, size, c1, c2, c3, c4, bold, italic, underline, overstrike, scalex, scaley, spacing, angle, borderstyle, outline, shadow, alignment, margin_l, margin_r, margin_v, encoding = read_field(style_line, 22)
+			-- Direct data
+			name = name:trim()
+			font_name[name] = font:trim()
+			font_size[name] = parsenum(size)
+			color1[name] = parse_style_color(c1)
+			color2[name] = parse_style_color(c2)
+			color3[name] = parse_style_color(c3)
+			color4[name] = parse_style_color(c4)
+			font_bold[name] = (parsenum(bold) ~= 0) and "bold" or ""
+			font_italic[name] = (parsenum(italic) ~= 0) and "italic" or ""
+
+			-- Derived data
+			if font:match("@") then
+				vertical[name] = true
+			end
+			alignment = parsenum(alignment)
+			if alignment <= 3 then
+				if vertical[name] then
+					pos_v[name] = sres_x - parsenum(margin_v)
+				else
+					pos_v[name] = sres_y - parsenum(margin_v)
+				end
+			elseif alignment <= 6 then
+				if vertical[name] then
+					pos_v[name] = sres_x / 2
+				else
+					pos_v[name] = sres_y / 2
+				end
+			else
+				pos_v[name] = parsenum(margin_v)
+			end
+		end
+	end
+end
+
+function init(f)
+	if inited then return end
+	inited = true
+	
+	vres_x = f.width
+	vres_y = f.height
+	read_input_file(overlua_datastring)
+end
+
+
+-- Mask for noise over background
+local noisemask, noisemaskctx, noisemaskfilled
+-- Additional images to overlay the frame
+local frame_overlays = {}
+
+
+-- Calculate size and position of a line and its syllables
+function calc_line_metrics(ctx, line)
+	if line.pos_x then return end
+
+	assert(font_name[line.style], "No font name for style " .. line.style)
+	ctx.select_font_face(font_name[line.style], font_italic[line.style], font_bold[line.style])
+	ctx.set_font_size(font_size[line.style])
+	
+	line.te = ctx.text_extents(line.cleantext)
+	line.fe = ctx.font_extents()
+	
+	if vertical[line.style] then
+		line.pos_x = pos_v[line.style]
+		line.pos_y = (sres_y - line.te.width) / 2 - line.te.x_bearing
+	else
+		line.pos_x = (sres_x - line.te.width) / 2 - line.te.x_bearing
+		line.pos_y = pos_v[line.style]
+	end
+	
+	if #line.kara < 2 then return end
+	
+	local curx = line.pos_x
+	local cury = line.pos_y
+	for i, syl in pairs(line.kara) do
+		syl.te = ctx.text_extents(syl.text)
+		if vertical[line.style] then
+			syl.pos_x = line.pos_x
+			syl.pos_y = cury
+			syl.center_x = syl.pos_x + syl.te.x_bearing + syl.te.width/2
+			syl.center_y = cury - line.fe.ascent/2 + line.fe.descent/2
+		else
+			syl.pos_x = curx
+			syl.pos_y = line.pos_y
+			syl.center_x = curx + syl.te.x_bearing + syl.te.width/2
+			syl.center_y = syl.pos_y - line.fe.ascent/2 + line.fe.descent/2
+		end
+		curx = curx + syl.te.x_advance
+		cury = cury + syl.te.x_advance
+	end
+end
+
+
+-- Style handling functions
+local stylefunc = {}
+
+function stylefunc.generic(t, line)
+	if not line.textsurf then
+		line.textsurf = cairo.image_surface_create(sres_x, sres_y, "argb32")
+		local c = line.textsurf.create_context()
+
+		c.select_font_face(font_name[line.style], font_italic[line.style], font_bold[line.style])
+		c.set_font_size(font_size[line.style])
+		
+		if vertical[line.style] then
+			c.translate(line.pos_x, line.pos_y)
+			c.rotate(math.pi/2)
+			c.move_to(0,0)
+		else
+			c.move_to(line.pos_x, line.pos_y)
+		end
+		c.text_path(line.cleantext)
+		
+		local c1, c3 = color1[line.style], color3[line.style]
+		c.set_source_rgba(c1.r, c1.g, c1.b, c1.a)
+		c.set_line_join("round")
+		c.set_line_width(4)
+		c.stroke_preserve()
+		c.set_source_rgba(c3.r, c3.g, c3.b, c3.a)
+		c.fill()
+	end
+	
+	-- Fade-factor (alpha for line)
+	local fade = 0
+	
+	if t < line.start_time and t >= line.start_time - line_fade_duration then
+		fade = 1 - (line.start_time - t) / line_fade_duration
+	elseif t >= line.end_time and t < line.end_time + line_fade_duration then
+		fade = 1 - (t - line.end_time) / line_fade_duration
+	elseif t >= line.start_time and t < line.end_time then
+		fade = 1
+	else
+		fade = 0
+	end
+	
+	if fade > 0 then
+		local lo = {} -- line overlay
+		lo.surf = line.textsurf
+		lo.x, lo.y = 0, 0
+		lo.alpha = 0.85 * fade
+		lo.operator = "over"
+		lo.name = "line"
+		table.insert(frame_overlays, lo)
+		
+		noisemaskctx.set_source_surface(line.textsurf, 0, 0)
+		noisemaskctx.paint_with_alpha(fade)
+		noisemaskfilled = true
+	end
+	
+	for i, syl in pairs(line.kara) do
+		if syl.end_time < syl.start_time + syl_highlight_duration then
+			syl.end_time = syl.start_time + syl_highlight_duration
+		end
+		
+		if t >= syl.start_time and t < syl.end_time then
+			local sw, sh = syl.te.width*3, line.fe.height*3
+			if vertical[line.style] then
+				sw, sh = sh, sw
+			end
+			
+			local fade = (syl.end_time - t) / (syl.end_time - syl.start_time)
+			
+			local surf = cairo.image_surface_create(sw, sh, "argb32")
+			local ctx = surf.create_context()
+			
+			ctx.select_font_face(font_name[line.style], font_italic[line.style], font_bold[line.style])
+			ctx.set_font_size(font_size[line.style]*2)
+			
+			local te, fe = ctx.text_extents(syl.text), ctx.font_extents()
+			
+			local rx, ry = (sw - te.width) / 2 + te.x_bearing, (sh - fe.height) / 2 + fe.ascent
+			assert(not vertical[line.style], "Can't handle vertical kara in syllable highlight code - poke jfs if you need this")
+			
+			ctx.move_to(rx, ry)
+			ctx.text_path(syl.text)
+			
+			local path = ctx.copy_path()
+			local function modpath(x, y)
+				local cx = math.sin(y/sh*math.pi)
+				local cy = math.sin(x/sw*math.pi)
+				cx = cx * x + (1-cx)/2*sw
+				cy = cy * y + (1-cy)/2*sh
+				return fade*x+(1-fade)*cx, fade*y+(1-fade)*cy
+			end
+			path.map_coords(modpath)
+			ctx.new_path()
+			ctx.append_path(path)
+			
+			local c2, c3 = color2[line.style], color3[line.style]
+			
+			for b = 8, 1, -3 do
+				local bs = cairo.image_surface_create(sw, sh, "argb32")
+				local bc = bs.create_context()
+				bc.set_source_rgba(c2.r, c2.g, c2.b, c2.a)
+				bc.append_path(path)
+				bc.fill()
+				raster.gaussian_blur(bs, b)
+				local bo = {}
+				bo.surf = bs
+				bo.x = syl.center_x - sw/2
+				bo.y = syl.center_y - sh/2
+				bo.alpha = fade
+				bo.operator = "add"
+				bo.name = "blur " .. b
+				table.insert(frame_overlays, bo)
+			end
+			
+			ctx.set_source_rgba(c3.r, c3.g, c3.b, c3.a)
+			ctx.set_line_join("round")
+			ctx.set_operator("over")
+			ctx.set_line_width(3*fade)
+			ctx.stroke_preserve()
+			ctx.set_operator("dest_out")
+			ctx.fill()
+			raster.box_blur(surf, 3, 2)
+			
+			local so = {}
+			so.surf = surf
+			so.x = syl.center_x - sw/2
+			so.y = syl.center_y - sh/2
+			so.alpha = 1
+			so.operator = "over"
+			so.name = string.format("bord %s %.1f %.1f (%.1f,%.1f)", syl.text, sw, sh, rx, ry)
+			table.insert(frame_overlays, so)
+		end
+	end
+end
+
+stylefunc.Romaji = stylefunc.generic
+stylefunc.Kanji = stylefunc.generic
+stylefunc.English = stylefunc.generic
+
+
+-- Main rendering function
+function render_frame(f, t)
+	init(f)
+	
+	local surf = f.create_cairo_surface()
+	local ctx = surf.create_context()
+	ctx.scale(vres_x/sres_x, vres_y/sres_y)
+	
+	-- The line rendering functions add the mask of the line they rendered to
+	-- this image. It will be used to draw the glow around all lines.
+	-- It has to be done in this way to avoid the glows from nearby lines to
+	-- interfere and produce double effect.
+	noisemask = cairo.image_surface_create(sres_x, sres_y, "argb32")
+	noisemaskctx = noisemask.create_context()
+	-- Set to true as soon as anything is put into the noise mask
+	-- This is merely an optimisation to avoid doing anything when there aren't
+	-- any lines on screen.
+	noisemaskfilled = false
+	-- List of images to overlay on the video frame, after the noise mask.
+	frame_overlays = {}
+	
+	for i, line in pairs(lines) do
+		if stylefunc[line.style] then
+			calc_line_metrics(ctx, line)
+			stylefunc[line.style](t, line)
+		end
+	end
+	
+	if noisemaskfilled then
+		-- Greenish and jittery version of the frame
+		local noiseimg = f.create_cairo_surface()
+		raster.box_blur(noiseimg, 5, 2)
+		raster.pixel_value_map(noiseimg, "G rand 0.4 * + =G G 1 - 1 G ifgtz =G")
+		-- Blurred version of the noisemask
+		raster.gaussian_blur(noisemask, 8)
+		-- Mask additive paint the noise mask: only show the area near the text
+		-- and have it do interesting things with the video.
+		ctx.set_source_surface(noiseimg, 0, 0)
+		ctx.set_operator("add")
+		ctx.mask_surface(noisemask, 0, 0)
+	end
+	
+	-- Paint generated overlays onto the video.
+	for i, o in pairs(frame_overlays) do
+		ctx.set_source_surface(o.surf, o.x, o.y)
+		ctx.set_operator(o.operator)
+		ctx.paint_with_alpha(o.alpha)
+	end
+	
+	f.overlay_cairo_surface(surf, 0, 0)
+end
+