apng

README

APNG golang library

APNG decoder with frame-hook for golang
Instead of storing every frame of the apng in memory, you can run any function you like on every frame. Forked from github.com/kettek/apng

Example

package main

import (
	"fmt"
	"os"
	"github.com/nexryai/apng"
)

func main() {
	// Open our animated PNG file
	f, err := os.Open("input.png")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	_, err = apng.DecodeAll(f, func(f *apng.FrameHookArgs) error {
		fmt.Printf("Frame %d | Delay:%v\n", f.Num, f.Delay)
		return nil
	})

	if err != nil {
		panic(err)
	}
}

Documentation

Overview

Package apng implements an APNG image decoder.

The PNG specification is at https://www.w3.org/TR/PNG/. The APNG specification is at https://wiki.mozilla.org/APNG_Specification

Index

• Constants
• func DecodeConfig(r io.Reader) (image.Config, error)
• type APNG
  • func DecodeAll(r io.Reader, hook func(*FrameHookArgs) error) (APNG, error)
• type FormatError
  • func (e FormatError) Error() string
• type Frame
  • func (f *Frame) GetDelay() float64
• type FrameHookArgs
• type UnsupportedError
  • func (e UnsupportedError) Error() string

Constants

const (
	DISPOSE_OP_NONE       = 0
	DISPOSE_OP_BACKGROUND = 1
	DISPOSE_OP_PREVIOUS   = 2
)

dispose_op values, as per the APNG spec.

const (
	BLEND_OP_SOURCE = 0
	BLEND_OP_OVER   = 1
)

blend_op values, as per the APNG spec.

Functions

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.

Types

type APNG

type APNG struct {
	Frames []Frame
	// LoopCount defines the number of times an animation will be
	// restarted during display.
	// A LoopCount of 0 means to loop forever
	LoopCount uint
}

func DecodeAll

func DecodeAll(r io.Reader, hook func(*FrameHookArgs) error) (APNG, error)

DecodeAll reads an APNG file from r and returns it as an APNG Type. If the first frame returns true for IsDefault(), that frame should not be part of the result. The type of Image returned depends on the PNG contents.

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 Frame

type Frame struct {
	XOffset, YOffset int
	DelayNumerator   uint16
	DelayDenominator uint16
	DelayTime        float32
	DisposeOp        byte
	BlendOp          byte
	// IsDefault indicates if the Frame is a default image that
	// should not be used in the animation. IsDefault can only
	// be true on the first frame.
	IsDefault bool
	// contains filtered or unexported fields
}

func (*Frame) GetDelay

func (f *Frame) GetDelay() float64

GetDelay returns the number of seconds in the frame.

type FrameHookArgs

type FrameHookArgs struct {
	Buffer    *image.Image
	Num       int
	Delay     float32
	Width     int
	OffsetX   int
	Height    int
	OffsetY   int
	BlendOp   int
	DisposeOp int
}

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