bw.close()   // flush to e.w
}

// Options are the encoding parameters.
type Options struct {
	// NumColors is the maximum number of colors used in the image.
	// It ranges from 1 to 256.
	NumColors int

	// Quantizer is used to produce a palette with size NumColors.
	// palette.Plan9 is used in place of a nil Quantizer.
	Quantizer draw.Quantizer

			return
		}
		img, typ, err := image.Decode(bytes.NewReader(b))
		if err != nil || typ != "gif" {
			return
		}
		for q := 1; q <= 256; q++ {
			var w bytes.Buffer
			err := Encode(&w, img, &Options{NumColors: q})
			if err != nil {
				t.Fatalf("failed to encode valid image: %s", err)
			}
			img1, err := Decode(&w)
			if err != nil {
				t.Fatalf("failed to decode roundtripped image: %s", err)
			}

	}
}

func (s *StackSet) assignColors() {
	// Assign different color indices to different packages.
	const numColors = 1048576
	for i, src := range s.Sources {
		pkg := packageName(src.FullName)
		h := sha256.Sum256([]byte(pkg))
		index := binary.LittleEndian.Uint32(h[:])
		s.Sources[i].Color = int(index % numColors)
	}

	if err != nil {
		t.Fatal(err)
	}
	img, err := Decode(bytes.NewReader(data))
	if err != nil {
		t.Fatal(err)
	}
	err = Encode(io.Discard, img, &Options{NumColors: 1})
	if err != nil {
		t.Fatal(err)
	}

		{"GIF.Delay", Field, 0},
		{"GIF.Disposal", Field, 5},
		{"GIF.Image", Field, 0},
		{"GIF.LoopCount", Field, 0},
		{"Options", Type, 2},
		{"Options.Drawer", Field, 2},
		{"Options.NumColors", Field, 2},
		{"Options.Quantizer", Field, 2},
	},
	"image/jpeg": {
		{"(FormatError).Error", Method, 0},
		{"(UnsupportedError).Error", Method, 0},
		{"Decode", Func, 0},
		{"DecodeConfig", Func, 0},

pkg image/gif, func EncodeAll(io.Writer, *GIF) error
pkg image/gif, type Options struct
pkg image/gif, type Options struct, Drawer draw.Drawer
pkg image/gif, type Options struct, NumColors int
pkg image/gif, type Options struct, Quantizer draw.Quantizer
pkg log/syslog (freebsd-386-cgo), const LOG_ALERT Priority
pkg log/syslog (freebsd-386-cgo), const LOG_AUTH Priority