cmd/gopngquant: initial crush functionality

cmd/gopngquant/main.go

@@ -3,13 +3,100 @@ package main
 import (
 	"flag"
 	"fmt"
+	"image"
+	"image/png"
 	"os"
 
 	"code.ivysaur.me/imagequant"
 )
 
+func GoImageToRgba32(im image.Image) []byte {
+	w := im.Bounds().Max.X
+	h := im.Bounds().Max.Y
+	ret := make([]byte, w*h*4)
+
+	for y := 0; y < h; y += 1 {
+		for x := 0; x < w; x += 1 {
+			r16, g16, b16, a16 := im.At(x, y).RGBA() // Each value ranges within [0, 0xffff]
+
+			ret[y*h+x+0] = uint8(r16 >> 8)
+			ret[y*h+x+1] = uint8(g16 >> 8)
+			ret[y*h+x+2] = uint8(b16 >> 8)
+			ret[y*h+x+3] = uint8(a16 >> 8)
+		}
+	}
+
+	return ret
+}
+
+func Crush(sourcefile, destfile string) error {
+
+	fh, err := os.OpenFile(sourcefile, os.O_RDONLY, 0444)
+	if err != nil {
+		return fmt.Errorf("os.OpenFile: %s", err.Error())
+	}
+	defer fh.Close()
+
+	img, err := png.Decode(fh)
+	if err != nil {
+		return fmt.Errorf("png.Decode: %s", err.Error())
+	}
+
+	attr, err := imagequant.NewAttributes()
+	if err != nil {
+		return fmt.Errorf("NewAttributes: %s", err.Error())
+	}
+	defer attr.Release()
+
+	rgba32data := GoImageToRgba32(img)
+
+	iqm, err := imagequant.NewImage(attr, string(rgba32data), img.Bounds().Max.X, img.Bounds().Max.Y, 0)
+	if err != nil {
+		return fmt.Errorf("NewImage: %s", err.Error())
+	}
+	defer iqm.Release()
+
+	res, err := iqm.Quantize(attr)
+	if err != nil {
+		return fmt.Errorf("Quantize: %s", err.Error())
+	}
+	defer res.Release()
+
+	rgb8data, err := res.WriteRemappedImage()
+	if err != nil {
+		return fmt.Errorf("WriteRemappedImage: %s", err.Error())
+	}
+
+	rect := image.Rectangle{Max: image.Point{X: res.GetImageWidth(), Y: res.GetImageHeight()}}
+	pal := res.GetPalette()
+	im2 := image.NewPaletted(rect, pal)
+	for y := 0; y < rect.Max.Y; y += 1 {
+		for x := 0; x < rect.Max.X; x += 1 {
+			im2.Set(x, y, pal[rgb8data[y*rect.Max.Y+x]])
+		}
+	}
+
+	fh2, err := os.OpenFile(destfile, os.O_WRONLY|os.O_CREATE, 0644)
+	if err != nil {
+		return fmt.Errorf("os.OpenFile: %s", err.Error())
+	}
+	defer fh2.Close()
+
+	penc := png.Encoder{
+		CompressionLevel: png.BestCompression,
+	}
+	err = penc.Encode(fh2, im2)
+	if err != nil {
+		return fmt.Errorf("png.Encode: %s", err.Error())
+	}
+
+	return nil
+}
+
 func main() {
 	ShouldDisplayVersion := flag.Bool("Version", false, "")
+	Infile := flag.String("In", "", "Input filename")
+	Outfile := flag.String("Out", "", "Output filename")
 
 	flag.Parse()
 
@@ -17,4 +104,12 @@ func main() {
 		fmt.Printf("libimagequant '%s' (%d)\n", imagequant.GetLibraryVersionString(), imagequant.GetLibraryVersion())
 		os.Exit(1)
 	}
+
+	err := Crush(*Infile, *Outfile)
+	if err != nil {
+		fmt.Println(err.Error())
+		os.Exit(1)
+	}
+
+	os.Exit(0)
 }