jpeg

Documentation

Overview

Package jpeg implements a JPEG image decoder and encoder.

JPEG is defined in ITU-T T.81: http://www.w3.org/Graphics/JPEG/itu-t81.pdf.

Index

• Constants
• func Decode(r io.Reader) (image.Image, os.Error)
• func DecodeConfig(r io.Reader) (image.Config, os.Error)
• func Encode(w io.Writer, m image.Image, o *Options) os.Error
• type FormatError
  • func (e FormatError) String() string
• type Options
• type Reader
• type UnsupportedError
  • func (e UnsupportedError) String() string

Constants

const DefaultQuality = 75

DefaultQuality is the default quality encoding parameter.

Functions

func Decode

func Decode(r io.Reader) (image.Image, os.Error)

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

func DecodeConfig

func DecodeConfig(r io.Reader) (image.Config, os.Error)

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

func Encode

func Encode(w io.Writer, m image.Image, o *Options) os.Error

Encode writes the Image m to w in JPEG 4:2:0 baseline format with the given options. Default parameters are used if a nil *Options is passed.

Types

type FormatError

type FormatError string

A FormatError reports that the input is not a valid JPEG.

func (FormatError) String

func (e FormatError) String() string

type Options

type Options struct {
	Quality int
}

Options are the encoding parameters. Quality ranges from 1 to 100 inclusive, higher is better.

type Reader

type Reader interface {
	io.Reader
	ReadByte() (c byte, err os.Error)
}

If the passed in io.Reader does not also have ReadByte, then Decode will introduce its own buffering.

type UnsupportedError

type UnsupportedError string

An UnsupportedError reports that the input uses a valid but unimplemented JPEG feature.

func (UnsupportedError) String

func (e UnsupportedError) String() string