PNG Encoder and Raster Toolkit for Lua / LuaJIT

• High-performance PNG encoder written in pure Lua with optional LuaJIT FFI backend.

LuaJIT is much faster and Lua is not recommended for production usage.

• Provides a lightweight raster pipeline (geometry, shapes).
• Supports RGB and RGBA color modes.
• Only requires bit library.
• This library does not perform any compression. Output files are uncompressed PNGs.

Usage

• Check examples folder for more examples.

luaPNG selects the default runner based on (require("luaPNG.init")).UsingJIT variable.

--- Encoding standart PNG.
local Image = require("luaPNG.init")

local png = Image.new(256, 256, "rgb")

for i = 1, 256*256*3 do
    png.Data[i] = math.random(0,255)
end

print(Image.UsingJIT)

png:save("Example256x256.png")
print("Done in: ", os.clock())

--- Encoding standart PNG and drawing rectangle.
local Image = require("luaPNG.init")
local img = Image.new(800, 600, "rgba")

img:add(Geometry.Rectangle{
    x = 0, y = 0,
    w = 300, h = 300,
    color = {220, 60, 60, 180}, -- RGBA
    mode = "fill"
})

img:save("Example800x600.png")
print("Done in:", os.clock())

Benchmark

• Check benchmark\output\log folder for benchmark results.
• LuaJIT is the default runner for benchmark but you can also use Lua which is very slow and not recommended.

Runned benchmark with: ffipng.lua using LuaJIT 2.1.1753364724

LIB	W	H	MODE	ENCODE SEC	WRITE MB/s	STATUS
FFI	1000	1000	RGB	0.030	95.41	OK
FFI	1000	1000	RGBA	0.037	103.14	OK
FFI	1500	1500	RGB	0.067	96.11	OK
FFI	1500	1500	RGBA	0.101	85.00	OK
FFI	2000	2000	RGB	0.183	62.55	OK
FFI	2000	2000	RGBA	0.181	84.32	OK
FFI	2500	2500	RGB	0.244	73.30	OK
FFI	2500	2500	RGBA	0.286	83.38	OK

Runned benchmark with: png.lua using LuaJIT 2.1.1753364724

LIB	W	H	MODE	ENCODE SEC	WRITE MB/s	STATUS
LUA	1000	1000	RGB	0.059	48.51	OK
LUA	1000	1000	RGBA	0.088	43.36	OK
LUA	1500	1500	RGB	0.121	53.22	OK
LUA	1500	1500	RGBA	0.183	46.91	OK
LUA	2000	2000	RGB	0.225	50.88	OK
LUA	2500	2500	RGB	0.370	48.34	OK

Runned benchmark with: png.lua using Lua 5.4.6

LIB	W	H	MODE	ENCODE SEC	WRITE MB/s	STATUS
LUA	1000	1000	rgb	1.165	2.46	OK
LUA	1000	1000	rgba	2.063	1.85	OK
LUA	1000	1500	rgb	1.688	2.54	OK
LUA	1000	1500	rgba	2.875	1.99	OK
LUA	1000	2000	rgb	2.503	2.29	OK
LUA	1000	2000	rgba	4.533	1.68	OK
LUA	1000	2500	rgb	2.950	2.43	OK
LUA	1000	2500	rgba	4.223	2.26	OK
LUA	1500	1500	rgb	3.126	2.06	OK
LUA	1500	1500	rgba	4.278	2.01	OK
LUA	2000	2000	rgb	4.821	2.37	OK
LUA	2000	2000	rgba	7.222	2.11	OK
LUA	2500	2500	rgb	7.492	2.39	OK
LUA	2500	2500	rgba	10.933	2.18	OK

Known Issues

png.lua

• png.lua slows down or crashes when encoding large RGBA images.

LUA,2000,1000,rgba,8000000,61.04,0.0000,0,0.00,0.00,ERROR: .\lib\png.lua:56: too many results to unpack

License

• MIT License