Play grayscale image as audio (really?)

conf.lua

--[[
Some notice:
1. This code is compatible with LOVE 0.10.0, and LOVE 11.0 (probably later version too)
2. Audio must have sample rate of 28224Hz
3. Audio is encoded to 8bit PCM (128 denotes 0) then converted to PNG
]]
local ffi = require("ffi")

function love.conf(t)
	t.window = nil
	t.modules.joystick = false
	t.modules.math = false
	t.modules.physics = false
	t.modules.system = false
	t.modules.thread = false
	t.modules.touch = false
	t.modules.video = false
end

local getChannelCount
if love._version >= "11.0" then
	function getChannelCount(sd)
		return sd:getChannelCount()
	end
else
	function getChannelCount(sd)
		return sd:getChannels()
	end
end

local astr = "Drag & drop grayscale image here\nImage audio must have sample rate of 28224"
local audiofile

function love.load(arg)
	-- if it's not fused, that means the first arg is the project name
	if love.filesystem.isFused() == false then table.remove(arg, 1) end
	-- If arg is 1, that means load directly
	if #arg == 1 then
		local luafile = assert(io.open(arg[1], "rb"))
		local f = love.filesystem.newFileData(luafile:read("*a"), "")
		luafile:close()
		local image = love.image.newImageData(f)
		local width, height = image:getDimensions()
		local sounddata = love.sound.newSoundData(width * height, 28224, 8, 1)
		local ptr = ffi.cast("uint8_t*", sounddata:getPointer())
		for i = 0, width * height - 1 do
			ptr[i] = image:getPixel(i % width, math.floor(i / width)) * 255
		end

		if audiofile then audiofile:stop() end
		audiofile = love.audio.newSource(sounddata)
		audiofile:setLooping(true)
		audiofile:play()
		
		astr = string.format("Playing %s", arg[1]:match(".-([^\\/]-%.?[^%.\\/]*)$"))
	-- If arg is 2, that mean encode audio to image
	elseif #arg >= 2 then
		local luafile = assert(io.open(arg[1], "rb"))
		local f = love.filesystem.newFileData(luafile:read("*a"), arg[1]:match(".-([^\\/]-%.?[^%.\\/]*)$"))
		luafile:close()
		luafile = assert(io.open(arg[2], "wb"))
		local sounddata = love.sound.newSoundData(f)
		local stereo = getChannelCount(sounddata) == 2
		local ratio = sounddata:getSampleRate() / 28224
		local imagesize = math.floor(math.sqrt(sounddata:getSampleCount() / ratio)) -- losing few samples is okay
		local image = love.image.newImageData(imagesize, imagesize)
		local iptr = ffi.cast("uint32_t*", image:getPointer())
		for i = 0, imagesize*imagesize-1 do
			local smpidx = i * ratio
			local i1, i2 = math.floor(smpidx), math.ceil(smpidx)
			local ifract = math.sin((smpidx - i1) * math.pi/2)
			local v
			
			if stereo then
				local sl = math.min(math.max((1 - ifract) * sounddata:getSample(i1 * 2) + ifract * sounddata:getSample(i2 * 2), -1), 1)
				local sr = math.min(math.max((1 - ifract) * sounddata:getSample(i1*2+1) + ifract * sounddata:getSample(i2*2+1), -1), 1)
				v = (sl + sr) * 0.5
			else
				v = math.min(math.max((1 - ifract) * sounddata:getSample(i1, 1) + ifract * sounddata:getSample(i2, 1), -1), 1)
			end
			
			-- 128 is 0, 255 is 1, 1 is 0
			v = math.floor(v * 127 + 128)
			iptr[i] = 4278190080 + v * 65536 + v * 256 + v
		end
		
		luafile:write(image:encode("png"):getString())
		luafile:close()
		love.event.quit()
		return
	end
	
	love.window.setMode(450, 50, {
		resizable = true
	})
	love.window.setTitle(string.format("ImagePlayer - LÖVE %s (%s)", love._version, love._version_codename))
end

function love.filedropped(file)
	local basename = file:getFilename():match(".-([^\\/]-%.?[^%.\\/]*)$")
	local s, image = pcall(love.image.newImageData, file)
	if s then
		local width, height = image:getDimensions()
		local sounddata = love.sound.newSoundData(width * height, 28224, 8, 1)
		local ptr = ffi.cast("uint8_t*", sounddata:getPointer())
		for i = 0, width * height - 1 do
			ptr[i] = image:getPixel(i % width, math.floor(i / width)) * 255
		end

		if audiofile then audiofile:stop() end
		audiofile = love.audio.newSource(sounddata)
		audiofile:setLooping(true)
		audiofile:play()
		
		astr = string.format("Playing %s", basename)
	else
		astr = string.format("%s\n%s", basename, image)
	end
end

function love.draw()
	collectgarbage()
	love.graphics.print(astr, 2, 2)
end

function love.keyreleased(key)
	if key == "space" and audiofile then
		if audiofile:isPlaying() then
			audiofile:pause()
		else
			audiofile:play()
		end
	end
end