Crate png

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§PNG encoder and decoder

This crate contains a PNG encoder and decoder. It supports reading of single lines or whole frames.

§The decoder

The most important types for decoding purposes are Decoder and Reader. They both wrap a std::io::Read. Decoder serves as a builder for Reader. Calling Decoder::read_info reads from the Read until the image data is reached.

§Using the decoder

use std::fs::File;

// The decoder is a build for reader and can be used to set various decoding options
// via `Transformations`. The default output transformation is `Transformations::EXPAND
// | Transformations::STRIP_ALPHA`.
let decoder = png::Decoder::new(File::open("tests/pngsuite/basi0g01.png").unwrap());
let (info, mut reader) = decoder.read_info().unwrap();
// Allocate the output buffer.
let mut buf = vec![0; info.buffer_size()];
// Read the next frame. Currently this function should only called once.
// The default options
reader.next_frame(&mut buf).unwrap();


§Using the encoder

    // For reading and opening files
    use std::path::Path;
    use std::fs::File;
    use std::io::BufWriter;
    // To use encoder.set()
    use png::HasParameters;

    let path = Path::new(r"/path/to/image.png");
    let file = File::create(path).unwrap();
    let ref mut w = BufWriter::new(file);

    let mut encoder = png::Encoder::new(w, 2, 1); // Width is 2 pixels and height is 1.
     let mut writer = encoder.write_header().unwrap();

    let data = [255, 0, 0, 255, 0, 0, 0, 255]; // An array containing a RGBA sequence. First pixel is red and second pixel is black.
    writer.write_image_data(&data).unwrap(); // Save


  • Chunk types and functions