webp

README

webp

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

Based on libwebp 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)

Benchmark

goos: linux
goarch: amd64
pkg: github.com/gen2brain/webp
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz

BenchmarkDecodeStd-8                             157	   7639585 ns/op	  473683 B/op	      13 allocs/op
BenchmarkDecodeWasm-8                            156	   7799653 ns/op	 2614793 B/op	     316 allocs/op
BenchmarkDecodeDynamic-8                         344	   3497863 ns/op	  943356 B/op	      58 allocs/op
BenchmarkDecodeTranspiled-8 (1)                  138	   8562133 ns/op	 1335622 B/op	      52 allocs/op
BenchmarkDecodeCGo1-8 (2)                        300	   3897300 ns/op	 1333630 B/op	      21 allocs/op
BenchmarkDecodeCGo2-8 (3)                        314	   3801195 ns/op	 1334020 B/op	      22 allocs/op

BenchmarkEncodeWasm-8                             12	  96123599 ns/op	 4857356 B/op	     298 allocs/op
BenchmarkEncodeDynamic-8                          55	  19022243 ns/op	   19888 B/op	      42 allocs/op
BenchmarkEncodeTranspiled-8 (1)                   18	  60042805 ns/op	   76104 B/op	      36 allocs/op
BenchmarkEncodeCGo1-8 (2)                         31	  32538122 ns/op	 3213497 B/op	  524294 allocs/op
BenchmarkEncodeCGo2-8 (3)                         52	  22482704 ns/op	   26043 B/op	       5 allocs/op

• (1) git.sr.ht/~jackmordaunt/go-libwebp
• (2) github.com/chai2010/webp
• (3) github.com/kolesa-team/go-webp

Documentation

Overview

Package webp implements an WEBP image decoder based on libwebp 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 Init()
• type Options
• type WEBP
  • func DecodeAll(r io.Reader) (*WEBP, error)

Constants

const DefaultMethod = 4

DefaultMethod is the default method encoding parameter.

const DefaultQuality = 75

DefaultQuality is the default quality encoding parameter.

Variables

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

Errors .

Functions

func Decode

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

Decode reads a WEBP 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 WEBP 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 Init

func Init()

Init 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/Encode will initialize the runtime.

Types

type Options

type Options struct {
	// Quality in the range [0,100]. Quality of 100 implies Lossless. Default is 75.
	Quality int
	// Lossless indicates whether to use the lossless compression. Lossless will ignore quality.
	Lossless bool
	// Method is quality/speed trade-off (0=fast, 6=slower-better). Default is 4.
	Method int
	// Exact preserve the exact RGB values in transparent area.
	Exact bool
}

Options are the encoding parameters.

type WEBP

type WEBP struct {
	// Decoded images.
	Image []image.Image
	// Delay times, one per frame, in milliseconds.
	Delay []int
}

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

func DecodeAll

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

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