avif

README

avif

Go encoder/decoder for AV1 Image File Format (AVIF) with support for animated AVIF images (decode only).

Based on libavif and aom compiled to WASM and used with wazero runtime (CGo-free).

The library will first try to use a dynamic/shared library (if installed) via purego and will fall back to WASM.

Build tags

• nodynamic - do not use dynamic/shared library (use only WASM)

Documentation

Overview

Package avif implements an AVIF image decoder based on libavif compiled to WASM.

Index

• Constants
• Variables
• func Decode(r io.Reader) (image.Image, error)
• func DecodeConfig(r io.Reader) (image.Config, error)
• func Dynamic() error
• func Encode(w io.Writer, m image.Image, o ...Options) error
• func InitDecoder()
• func InitEncoder()
• type AVIF
  • func DecodeAll(r io.Reader) (*AVIF, error)
• type Options

Constants

const DefaultQuality = 60

DefaultQuality is the default quality encoding parameter.

const DefaultSpeed = 10

DefaultSpeed is the default speed encoding parameter.

Variables

var (
	ErrMemRead  = errors.New("avif: mem read failed")
	ErrMemWrite = errors.New("avif: mem write failed")
	ErrDecode   = errors.New("avif: decode failed")
	ErrEncode   = errors.New("avif: encode failed")
)

Errors .

Functions

func Decode

func Decode(r io.Reader) (image.Image, error)

Decode reads a AVIF image from r and returns it as an image.Image.

func DecodeConfig

func DecodeConfig(r io.Reader) (image.Config, error)

DecodeConfig returns the color model and dimensions of a AVIF image without decoding the entire image.

func Dynamic

func Dynamic() error

Dynamic returns error (if there was any) during opening dynamic/shared library.

func Encode

func Encode(w io.Writer, m image.Image, o ...Options) error

Encode writes the image m to w with the given options.

func InitDecoder

func InitDecoder()

InitDecoder initializes wazero runtime and compiles the module. This function does nothing if a dynamic/shared library is used and Dynamic() returns nil. There is no need to explicitly call this function, first Decode will initialize the runtime.

func InitEncoder

func InitEncoder()

InitEncoder initializes wazero runtime and compiles the module. This function does nothing if a dynamic/shared library is used and Dynamic() returns nil. There is no need to explicitly call this function, first Encode will initialize the runtime.

Types

type AVIF

type AVIF struct {
	// Decoded images, NRGBA or NRGBA64.
	Image []image.Image
	// Delay times, one per frame, in seconds.
	Delay []float64
}

AVIF represents the possibly multiple images stored in a AVIF file.

func DecodeAll

func DecodeAll(r io.Reader) (*AVIF, error)

DecodeAll reads a AVIF image from r and returns the sequential frames and timing information.

type Options

type Options struct {
	// Quality in the range [0,100]. Quality of 100 implies lossless. Default is 60.
	Quality int
	// Quality in the range [0,100].
	QualityAlpha int
	// Speed in the range [0,10]. Slower should make for a better quality image in less bytes.
	Speed int
	// Chroma subsampling, 444|422|420.
	ChromaSubsampling image.YCbCrSubsampleRatio
}

Options are the encoding parameters.