local spr = app.activeSprite

if not spr then
	app.alert("No active sprite")
	return
end

local path = app.fs.filePath(spr.filename)
local name = app.fs.fileTitle(spr.filename)

if path == "" then
	path = app.fs.userDocsPath
end

local out_path = app.fs.joinPath(path, name .. ".ppm")

local img = Image(spr.width, spr.height, ColorMode.RGB)

-- Render visible layers / current frame into one image
img:drawSprite(spr, app.activeFrame.frameNumber)

local file = io.open(out_path, "wb")

if not file then
	app.alert("Could not write file:\n" .. out_path)
	return
end

-- PPM binary format, P6
file:write("P6\n")
file:write(tostring(spr.width) .. " " .. tostring(spr.height) .. "\n")
file:write("255\n")

for y = 0, spr.height - 1 do
	for x = 0, spr.width - 1 do
		local pixel = img:getPixel(x, y)
		local c = Color(pixel)

		file:write(string.char(c.red))
		file:write(string.char(c.green))
		file:write(string.char(c.blue))
	end
end

file:close()

app.alert("Exported PPM:\n" .. out_path)