Crate png

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 `TRANSFORM_EXPAND
// | TRANSFORM_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();

Encoder

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.
    encoder.set(png::ColorType::RGBA).set(png::BitDepth::Eight);
     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

Modules

chunk

Chunk types and functions

Structs

AnimationControl	Animation control information
Decoder	PNG Decoder
Encoder	PNG Encoder
FrameControl	Frame control information
Info	PNG info struct
OutputInfo	Output info
PixelDimensions	Pixel dimensions information
Reader	PNG reader (mostly high-level interface)
StreamingDecoder	PNG StreamingDecoder (low-level interface)
Transformations
Writer	PNG writer

Enums

BitDepth	Bit depth of the png file
ColorType
Decoded	Result of the decoding process
DecodingError
EncodingError
Unit	Physical unit of the pixel dimensions

Constants

TRANSFORM_BGR	Flip RGB to BGR, RGBA to BGRA
TRANSFORM_EXPAND	Expand paletted images to RGB, expand grayscale images of less than 8-bit depth to 8-bit depth, and expand tRNS chunks to alpha channels.
TRANSFORM_EXPAND_16
TRANSFORM_GRAY_TO_RGB
TRANSFORM_IDENTITY	No transformation
TRANSFORM_INVERT_ALPHA	Change alpha from opacity to transparency
TRANSFORM_INVERT_MONO	Invert monochrome images
TRANSFORM_PACKING	Expand 1, 2 and 4-bit samples to bytes
TRANSFORM_PACKSWAP	Change order of packed pixels to LSB first
TRANSFORM_SCALE_16
TRANSFORM_SHIFT	Normalize pixels to the sBIT depth
TRANSFORM_STRIP_16	Strip 16-bit samples to 8 bits
TRANSFORM_STRIP_ALPHA	Discard the alpha channel
TRANSFORM_STRIP_FILLER
TRANSFORM_STRIP_FILLER_AFTER
TRANSFORM_STRIP_FILLER_BEFORE
TRANSFORM_SWAP_ALPHA	Flip RGBA to ARGB or GA to AG
TRANSFORM_SWAP_ENDIAN	Byte-swap 16-bit samples

Traits

HasParameters	Object has parameters
Parameter	Configuration parameter trait