tool for making twitter appropriate gifs

twitterify.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"image"
+	"image/gif"
+	"os"
+
+	"golang.org/x/image/draw"
+)
+
+var (
+	width       = flag.Int("width", 506, "target min width")
+	height      = flag.Int("height", 0, "target min height")
+	repeat      = flag.Int("repeat", 3, "repeat count")
+	transparent = flag.Bool("transparent", false, "transparent background")
+	duplicate   = flag.Bool("duplicate", false, "use duplication instead of repeating animation")
+)
+
+func main() {
+	flag.Parse()
+
+	if flag.Arg(0) == "" || flag.Arg(1) == "" {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	srcfile, err := os.Open(flag.Arg(0))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	defer srcfile.Close()
+
+	targetfile, err := os.Create(flag.Arg(1))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	defer targetfile.Close()
+
+	source, err := gif.DecodeAll(srcfile)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+
+	size := image.Pt(source.Config.Width, source.Config.Height)
+	if size.X < *width {
+		size.X = *width
+	}
+	if size.Y < *height {
+		size.Y = *height
+	}
+
+	var target gif.GIF
+	target.Config = source.Config
+	target.Config.Width = size.X
+	target.Config.Height = size.Y
+
+	target.LoopCount = source.LoopCount
+	target.BackgroundIndex = source.BackgroundIndex
+
+	offset := image.Pt(
+		size.X/2-source.Config.Width/2,
+		size.Y/2-source.Config.Height/2,
+	)
+
+	for i, m := range source.Image {
+		d := image.NewPaletted(image.Rectangle{image.ZP, size}, m.Palette)
+		if !*transparent {
+			for k := range d.Pix {
+				d.Pix[k] = m.Pix[0]
+			}
+		}
+		draw.Draw(d, m.Bounds().Add(offset), m, image.ZP, draw.Src)
+
+		if *duplicate {
+			target.Image = append(target.Image, d)
+			target.Delay = append(target.Delay, source.Delay[i]/2)
+			if len(source.Disposal) > 0 {
+				target.Disposal = append(target.Disposal, source.Disposal[i])
+			}
+			if i != len(source.Image)-1 {
+				target.Image = append(target.Image, d)
+				target.Delay = append(target.Delay, source.Delay[i]/2)
+				if len(source.Disposal) > 0 {
+					target.Disposal = append(target.Disposal, source.Disposal[i])
+				}
+			}
+		} else {
+			target.Image = append(target.Image, d)
+			target.Delay = append(target.Delay, source.Delay[i])
+			if len(source.Disposal) > 0 {
+				target.Disposal = append(target.Disposal, source.Disposal[i])
+			}
+		}
+	}
+
+	if !*duplicate {
+		n := len(source.Image)
+		for k := 1; k < *repeat; k++ {
+			for i := 0; i < n; i++ {
+				target.Image = append(target.Image, target.Image[i])
+				target.Delay = append(target.Delay, target.Delay[i])
+				if len(target.Disposal) > 0 {
+					target.Disposal = append(target.Disposal, target.Disposal[i])
+				}
+			}
+		}
+	}
+
+	err = gif.EncodeAll(targetfile, &target)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to encode: %v\n", err)
+		os.Exit(1)
+	}
+}