Add txqr-gif command

cmd/txqr-gif/.gitignore

@@ -0,0 +1 @@
+txqr-ascii

cmd/txqr-gif/main.go

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+package main
+
+import (
+	"encoding/base64"
+	"flag"
+	"image"
+	"image/gif"
+	"io/ioutil"
+	"log"
+	"os"
+	"time"
+
+	"github.com/divan/txqr/protocol"
+	"github.com/divan/txqr/qr"
+)
+
+func main() {
+	splitSize := flag.Int("split", 100, "Chunk size for data split per frame")
+	size := flag.Int("size", 300, "QR code size")
+	delay := flag.Duration("delay", 100*time.Millisecond, "Delay between frames")
+	output := flag.String("o", "out.gif", "Output animated gif file")
+	flag.Parse()
+
+	if len(flag.Args()) != 1 {
+		log.Fatalf("Usage: %s file", os.Args[0])
+	}
+
+	filename := flag.Args()[0]
+
+	data, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Fatalf("Read input file failed: %v", err)
+	}
+
+	str := base64.StdEncoding.EncodeToString(data)
+	log.Println("Base64 encoded size:", len(str), "bytes")
+	chunks, err := protocol.NewEncoder(*splitSize).Encode(str)
+	if err != nil {
+		log.Fatalf("Encode failed: %v", err)
+	}
+
+	out := &gif.GIF{
+		Image: make([]*image.Paletted, len(chunks)),
+		Delay: make([]int, len(chunks)),
+	}
+	for i, chunk := range chunks {
+		qr, err := qr.Encode(chunk, *size)
+		if err != nil {
+			log.Fatalf("[ERROR] QR: %v", err)
+		}
+		out.Image[i] = qr.(*image.Paletted)
+		out.Delay[i] = int(*delay / (10 * time.Millisecond)) // yeah, delays are in 100th of a second
+	}
+
+	fd, err := os.Create(*output)
+	if err != nil {
+		log.Fatalf("[ERROR] Create file: %v", err)
+	}
+	err = gif.EncodeAll(fd, out)
+	if err != nil {
+		log.Fatalf("[ERROR] Generate gif: %v", err)
+	}
+	log.Printf("Saved %d frames into %s\n", len(chunks), *output)
+
+}