Crate png

Expand description

§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::IDENTITY`.
let decoder = png::Decoder::new(File::open("tests/pngsuite/basi0g01.png").unwrap());
let mut reader = decoder.read_info().unwrap();
// Allocate the output buffer.
let mut buf = vec![0; reader.output_buffer_size()];
// Read the next frame. An APNG might contain multiple frames.
let info = reader.next_frame(&mut buf).unwrap();
// Grab the bytes of the image.
let bytes = &buf[..info.buffer_size()];
// Inspect more details of the last read frame.
let in_animation = reader.info().frame_control.is_some();

§Encoder

§Using the encoder

// For reading and opening files
use std::path::Path;
use std::fs::File;
use std::io::BufWriter;

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_color(png::ColorType::Rgba);
encoder.set_depth(png::BitDepth::Eight);
encoder.set_source_gamma(png::ScaledFloat::from_scaled(45455)); // 1.0 / 2.2, scaled by 100000
encoder.set_source_gamma(png::ScaledFloat::new(1.0 / 2.2));     // 1.0 / 2.2, unscaled, but rounded
let source_chromaticities = png::SourceChromaticities::new(     // Using unscaled instantiation here
    (0.31270, 0.32900),
    (0.64000, 0.33000),
    (0.30000, 0.60000),
    (0.15000, 0.06000)
);
encoder.set_source_chromaticities(source_chromaticities);
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
text_metadata: Text chunks (tEXt/zTXt/iTXt) structs and functions

Structs§

Adam7Info: Describes which stage of the Adam7 algorithm applies to a decoded row.
AnimationControl: Animation control information
CodingIndependentCodePoints: Coding-independent code points (cICP) specify the color space (primaries), transfer function, matrix coefficients and scaling factor of the image using the code points specified in ITU-T-H.273.
ContentLightLevelInfo: Content light level information of HDR content.
DecodeOptions: Decoder configuration options
Decoder: PNG Decoder
Encoder: PNG Encoder.
FrameControl: Frame control information
Info: PNG info struct
InterlacedRow: A row of data with interlace information attached.
Limits: Limits on the resources the Decoder is allowed too use
MasteringDisplayColorVolume: Mastering Display Color Volume (mDCV) used at the point of content creation, as specified in SMPTE-ST-2086.
OutputInfo: Output info.
ParameterError
PixelDimensions: Pixel dimensions information
Reader: PNG reader (mostly high-level interface)
ScaledFloat: An unsigned integer scaled version of a floating point value, equivalent to an integer quotient with fixed denominator (100_000)).
SourceChromaticities: Chromaticities of the color space primaries
StreamWriter: Streaming PNG writer
StreamingDecoder: PNG StreamingDecoder (low-level interface)
Transformations: Output transformations
Writer: PNG writer

Enums§

AdaptiveFilterType: Adaptive filtering tries every possible filter for each row and uses a heuristic to select the best one. This improves compression ratio, but makes encoding slightly slower.
BitDepth: Bit depth of the PNG file. Specifies the number of bits per sample.
BlendOp: How pixels are written into the buffer.
ColorType: Describes how a pixel is encoded.
Compression: The type and strength of applied compression.
Decoded: Result of the decoding process
DecodingError: Any kind of error during PNG decoding.
DisposeOp: How to reset buffer of an animated png (APNG) at the end of a frame.
EncodingError
FilterType: The byte level filter applied to scanlines to prepare them for compression.
InterlaceInfo: Describes which interlacing algorithm applies to a decoded row.
SrgbRenderingIntent: The rendering intent for an sRGB image.
Unit: Physical unit of the pixel dimensions

Functions§

expand_interlaced_row: Copies pixels from interlaced_row into the right location in img.

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