png

package
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Published: Nov 23, 2020 License: BSD-3-Clause Imports: 11 Imported by: 0

Documentation

Overview

Package png implements a PNG image decoder and encoder. Only 1-bit images can be decoded (grayscale or paletted).

The PNG specification is at https://www.w3.org/TR/PNG/.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func Decode

func Decode(r io.Reader) (*img1b.Image, error)

Decode reads a PNG image from r and returns it as an img1b.Image.

func DecodeConfig

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

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

func Encode

func Encode(w io.Writer, m *img1b.Image) error

Encode writes the Image m to w in PNG format.

Types

type CompressionLevel

type CompressionLevel int
const (
	DefaultCompression CompressionLevel = 0
	NoCompression      CompressionLevel = -1
	BestSpeed          CompressionLevel = -2
	BestCompression    CompressionLevel = -3
)

type Encoder

type Encoder struct {
	CompressionLevel CompressionLevel

	// BufferPool optionally specifies a buffer pool to get temporary
	// EncoderBuffers when encoding an image.
	BufferPool EncoderBufferPool
}

Encoder configures encoding PNG images.

func (*Encoder) Encode

func (enc *Encoder) Encode(w io.Writer, m *img1b.Image) error

Encode writes the Image m to w in PNG format.

type EncoderBuffer

type EncoderBuffer encoder

EncoderBuffer holds the buffers used for encoding PNG images.

type EncoderBufferPool

type EncoderBufferPool interface {
	Get() *EncoderBuffer
	Put(*EncoderBuffer)
}

EncoderBufferPool is an interface for getting and returning temporary instances of the EncoderBuffer struct. This can be used to reuse buffers when encoding multiple images.

type FormatError

type FormatError string

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

func (FormatError) Error

func (e FormatError) Error() string

type UnsupportedError

type UnsupportedError string

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

func (UnsupportedError) Error

func (e UnsupportedError) Error() string

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