Purpose

LuaLodePNG is a Lua binding to lodepng (https://github.com/lvandeve/lodepng)

Examples

local llp=require "lodepng"
print("Use lualodepng version", llp.version)
print("Use lodepng version", llp.lodepng.version)
local image=llp.readfile("demo.png")
print("demo.png:", image)

print "type\toffset\tlen\tdetails"
for _,chunk in ipairs(llp.chunklist("demo.png")) do
    local P=chunk.props
    local details=string.format("essential='%s', copyable=%s, crc_ok=%s, visible='%s'", P.essential, P.copyable, P.crc_ok, P.visible)
    print(chunk.type,chunk.offset,chunk.len,details)
end

Requirements

• C++ 20
• Lua 5.4

Submodules

• Lodepng
• LuaAide
• ulutest

How to build: First ...

git submodule init
git submodule update

then on Linux ...

make

creates lodepng.so and executes unit test. Copy the shared object to where Lua will find it with require "lodepng".

else on Windows ...

Edit buildsys/VS17/Lua.props to point to your installation of Lua. Build with Visual Studio 2022 (VS17).
Execute unit test with

lua unittest.lua

The Release build (32 bit) will create lodepng.dll in the repository root directory, the Debug build in buildsys/VS17/Debug. Copy the DLL to where Lua will find it with require "lodepng".

Status

Version 0.1 Preliminary - under development

readfile(filename)      reads a png-file, returns image object
chunklist(filename)     returns a list of items, that contain information about the chunks in the file.
                        Example:
                        IHDR    13      0       {essential='critical', copyable=false, crc_ok=true, visible='public'}
                        gAMA    4       25      {essential='ancillary', copyable=false, crc_ok=true, visible='public'}
                        IDAT    4255    41      {essential='critical', copyable=false, crc_ok=true, visible='public'}
                        IEND    0       4308    {essential='critical', copyable=false, crc_ok=true, visible='public'}