Rust version of LodePNG

This is a pure Rust PNG image decoder and encoder. Allows easy reading and writing of PNG files without any system dependencies.

The easiest way to use LodePNG is to include the lodepng crate. To do so, add this to your Cargo.toml:

[dependencies]
lodepng = "2.0.0"

See API reference for details. Requires Rust 1.21 or later.

Loading image example

let image = lodepng::decode32_file("in.png")?;

returns image of type lodepng::Bitmap<lodepng::RGBA<u8>> with fields .width, .height, and .buffer (the buffer is a Vec).

The RGB/RGBA pixel types are from the RGB crate, which you can import separately to use the same pixel struct throughout the program, without casting. But if you want to read the image buffer as bunch of raw bytes, ignoring the RGB(A) pixel structure, use:

[dependencies]
rgb = "0.8"

extern crate rgb;
use rgb::*;
…
let bytes: &[u8] = image.buffer.as_bytes();

Saving image example

lodepng::encode32_file("out.png", &buffer, width, height)

The buffer can be a slice of any type as long as it has 4 bytes per element (e.g. struct RGBA or (u8,u8,u8,u8)).

Advanced

let mut state = lodepng::State::new();
state.remember_unknown_chunks(true);

match state.decode("in.png") {
    Ok(lodepng::Image::RGB(image)) => {…}
    Ok(lodepng::Image::RGBA(image)) => {…}
    Ok(lodepng::Image::RGBA16(image)) => {…}
    Ok(lodepng::Image::Gray(image)) => {…}
    Ok(_) => {…}
    Err(err) => {…}
}

for chunk in state.info_png().unknown_chunks() {
    println!("{:?} = {:?}", chunk.name(), chunk.data());
}

// Color profile (to be used with e.g. LCMS2)
let icc_data = state.info_png().get_icc();

Upgrading from 1.x

• CVec has been replaced with a regular Vec. Delete extra .as_ref() that the compiler may complain about.
• LCT_* constants have been changed to ColorType::*.
• Chunk/Chunks renamed to ChunkRef/ChunksIter
• auto_convert is a boolean
• bitdepth has a getter/setter
• There is no C any more!

Origin of Rust version

This codebase is derived from C LodePNG by Lode Vandevenne. It has been converted to Rust using Citrus C to Rust converter and manual refactorings.