generator.go

package main

import (
	"bytes"
	"image"
	"image/gif"
	"io/ioutil"
	"github.com/james4k/terminal"
	"os"
)

// GifGenerator type
type GifGenerator struct {
	Speed      float64
	Col        int
	Row        int
	NoLoop     bool
	ScreenInfo *ScreenInfo
}

// NewGifGenerator returns GifGenerator instance
func NewGifGenerator() *GifGenerator {
	return &GifGenerator{
		Speed:      1.0,
		Col:        80,
		Row:        24,
		NoLoop:     false,
		ScreenInfo: NewScreenInfo(),
	}
}

// Generate writes to outFile an animated GIF
func (g *GifGenerator) Generate(input string, output string) (err error) {
	// virtual terminal
	var state = terminal.State{}
	vt, err := terminal.Create(&state, ioutil.NopCloser(bytes.NewBuffer([]byte{})))
	if err != nil {
		return
	}
	defer vt.Close()
	vt.Resize(g.Col, g.Row)

	// play and capture
	var (
		images  []*image.Paletted
		delays  []int
		ttyTime int64
		gifTime int64
	)
	err = g.TtyPlay(input, vt, func(diff int32) (err error) {
		ttyTime += int64(float64(diff) / g.Speed)
		delay := int((ttyTime-gifTime)/10000/10) * 10
		gifTime += int64(delay) * 10000
		if delay > 0 {
			var img *image.Paletted
			img, err = g.Capture(&state)
			if err != nil {
				return
			}
			images = append(images, img)
			delays = append(delays, delay)
		}
		return nil
	})
	if err != nil {
		return
	}

	// generate gif file
	outFile, err := os.Create(output)
	if err != nil {
		return
	}
	defer outFile.Close()
	opts := gif.GIF{
		Image: images,
		Delay: delays,
	}
	if g.NoLoop {
		opts.LoopCount = 1
	}
	err = gif.EncodeAll(outFile, &opts)
	if err != nil {
		return
	}
	return nil
}