Convert Gif's to PingPong Gif's

make_gifs.go

package main

import (
	"bytes"
	"image"
	"image/gif"
	"io/ioutil"
	"log"
	"net/http"
	"sort"
	"strconv"
)

var urls = []string{
	"https://j.gifs.com/lOEomr.gif",
	"https://j.gifs.com/k5XnlE.gif",
	"https://j.gifs.com/g5MjG3.gif",
	"https://j.gifs.com/98YwyZ.gif",
	"https://j.gifs.com/Wnoylv.gif",
	"https://j.gifs.com/3lVnpx.gif",
	"https://j.gifs.com/VmnxkW.gif",
	"https://j.gifs.com/Q1gp2L.gif",
	"https://j.gifs.com/LgWk2A.gif",
	"https://media.giphy.com/media/KaMqnPFHqAesw/source.gif",
}

var c = make(chan orderedGifs, 10)
var giferr = make(chan error, 10)

type orderedGifs struct {
	sourceurl string
	destFile  string
	order     int
}

// ByOrder implements the sort.Interface for []orderedGifs based on
// the order field.
type ByOrder []orderedGifs

func (a ByOrder) Len() int           { return len(a) }
func (a ByOrder) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByOrder) Less(i, j int) bool { return a[i].order < a[j].order }

func main() {
	maxLen := len(urls)
	for i := 0; i < maxLen; i++ {
		log.Printf("Processing %d %s", i, urls[i])
		go pingpong(i, urls[i])
	}
	count := 0
	orderedGifs := []orderedGifs{}
	for {
		select {
		case err := <-giferr:
			count++
			log.Printf("Error processing %v", err)
		case s := <-c:
			count++
			orderedGifs = append(orderedGifs, s)
			log.Printf("Finished processing %s", s.destFile)
		}
		if count == maxLen {
			break
		}
	}
	close(c)
	close(giferr)
	sort.Sort(ByOrder(orderedGifs))
	log.Printf("%d urls submitted %d processed", len(urls), len(orderedGifs))
	for i := 0; i < len(orderedGifs); i++ {
		log.Printf("Gif order: %d %s %s", orderedGifs[i].order, orderedGifs[i].sourceurl, orderedGifs[i].destFile)
	}
}

func pingpong(i int, url string) {
	destFile := "dest/" + strconv.Itoa(i) + ".gif"
	sourceFile := "source/" + strconv.Itoa(i) + ".gif"
	resp, err := http.Get(url)
	if err != nil || resp.StatusCode != 200 {
		giferr <- err
		return
	}
	source, err := gif.DecodeAll(resp.Body)
	if err != nil {
		giferr <- err
		return
	}
	buf := new(bytes.Buffer)
	err = gif.EncodeAll(buf, source)
	if err != nil {
		giferr <- err
		return
	}
	err = ioutil.WriteFile(sourceFile, buf.Bytes(), 0644)
	if err != nil {
		giferr <- err
		return
	}
	dest := &gif.GIF{
		BackgroundIndex: source.BackgroundIndex,
		Config: image.Config{
			Width:      source.Config.Width,
			Height:     source.Config.Height,
			ColorModel: source.Config.ColorModel,
		},
		LoopCount: source.LoopCount,
	}

	for i := 0; i < len(source.Image)-1; i++ {
		dest.Image = append(dest.Image, source.Image[i])
		dest.Delay = append(dest.Delay, source.Delay[i])
		dest.Disposal = append(dest.Disposal, source.Disposal[i])
	}
	finalDelay := source.Delay[len(source.Delay)-1]
	for i := len(source.Image) - 2; i > 0; i-- {
		dest.Image = append(dest.Image, source.Image[i])
		dest.Delay = append(dest.Delay, source.Delay[i])
		dest.Disposal = append(dest.Disposal, gif.DisposalPrevious)
	}
	dest.Delay[len(dest.Delay)-1] = finalDelay
	buf = new(bytes.Buffer)
	err = gif.EncodeAll(buf, dest)
	if err != nil {
		giferr <- err
		return
	}
	ioutil.WriteFile(destFile, buf.Bytes(), 0644)
	c <- orderedGifs{destFile: destFile, order: i, sourceurl: url}
}

make_gifs.out

aarti@classyhacker:~/dev/interview/gifs.com$ go run make_gif.go
2016/12/30 16:25:07 Processing 0 https://j.gifs.com/lOEomr.gif
2016/12/30 16:25:07 Processing 1 https://j.gifs.com/k5XnlE.gif
2016/12/30 16:25:07 Processing 2 https://j.gifs.com/g5MjG3.gif
2016/12/30 16:25:07 Processing 3 https://j.gifs.com/98YwyZ.gif
2016/12/30 16:25:07 Processing 4 https://j.gifs.com/Wnoylv.gif
2016/12/30 16:25:07 Processing 5 https://j.gifs.com/3lVnpx.gif
2016/12/30 16:25:07 Processing 6 https://j.gifs.com/VmnxkW.gif
2016/12/30 16:25:07 Processing 7 https://j.gifs.com/Q1gp2L.gif
2016/12/30 16:25:07 Processing 8 https://j.gifs.com/LgWk2A.gif
2016/12/30 16:25:07 Processing 9 https://media.giphy.com/media/KaMqnPFHqAesw/source.gif
2016/12/30 16:25:08 Finished processing dest/9.gif
2016/12/30 16:25:15 Finished processing dest/8.gif
2016/12/30 16:25:15 Error processing gif: too much image data
2016/12/30 16:25:15 Finished processing dest/4.gif
2016/12/30 16:25:16 Finished processing dest/0.gif
2016/12/30 16:25:16 Finished processing dest/5.gif
2016/12/30 16:25:17 Finished processing dest/2.gif
2016/12/30 16:25:17 Finished processing dest/3.gif
2016/12/30 16:25:17 Finished processing dest/6.gif
2016/12/30 16:25:18 Finished processing dest/7.gif
2016/12/30 16:25:18 10 urls submitted 9 processed
2016/12/30 16:25:18 Gif order: 0 https://j.gifs.com/lOEomr.gif dest/0.gif
2016/12/30 16:25:18 Gif order: 2 https://j.gifs.com/g5MjG3.gif dest/2.gif
2016/12/30 16:25:18 Gif order: 3 https://j.gifs.com/98YwyZ.gif dest/3.gif
2016/12/30 16:25:18 Gif order: 4 https://j.gifs.com/Wnoylv.gif dest/4.gif
2016/12/30 16:25:18 Gif order: 5 https://j.gifs.com/3lVnpx.gif dest/5.gif
2016/12/30 16:25:18 Gif order: 6 https://j.gifs.com/VmnxkW.gif dest/6.gif
2016/12/30 16:25:18 Gif order: 7 https://j.gifs.com/Q1gp2L.gif dest/7.gif
2016/12/30 16:25:18 Gif order: 8 https://j.gifs.com/LgWk2A.gif dest/8.gif
2016/12/30 16:25:18 Gif order: 9 https://media.giphy.com/media/KaMqnPFHqAesw/source.gif dest/9.gif