Initial commit

codec/coder.go

@@ -0,0 +1,12 @@
+package codec
+
+import (
+	"bytes"
+	"image"
+	"io"
+)
+
+type Coder interface {
+	Decode(io.Reader) (image.Image, error)
+	Encode(image.Image, int) (bytes.Buffer, error)
+}

codec/jpeg.go

@@ -0,0 +1,23 @@
+package codec
+
+import (
+	"bytes"
+	"image"
+	"image/jpeg"
+	"io"
+)
+
+type JPGCoder struct{}
+
+func (coder JPGCoder) Decode(r io.Reader) (image.Image, error) {
+	i, err := jpeg.Decode(r)
+	if err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (coder JPGCoder) Encode(i image.Image, quality int) (buf bytes.Buffer, err error) {
+	err = jpeg.Encode(&buf, i, &jpeg.Options{Quality: quality})
+	return buf, err
+}

codec/png.go

@@ -0,0 +1,34 @@
+package codec
+
+import (
+	"bytes"
+	"github.com/foobaz/lossypng/lossypng"
+	"image"
+	"image/png"
+	"io"
+)
+
+type PNGCoder struct{}
+
+const qMax = 20
+
+func (coder PNGCoder) Decode(r io.Reader) (image.Image, error) {
+	i, err := png.Decode(r)
+	if err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (coder PNGCoder) Encode(i image.Image, quality int) (buf bytes.Buffer, err error) {
+	c := lossypng.Compress(i, 2, qualityFactor(quality))
+	err = png.Encode(&buf, c)
+	return buf, err
+}
+
+// qualityFactor normalizes the PNG quality factor from a max of 20, where 0 is
+// no conversion.
+func qualityFactor(q int) int {
+	f := q / 100
+	return qMax - (f * qMax)
+}

codec/webp.go

@@ -0,0 +1,26 @@
+package codec
+
+import (
+	"bytes"
+	"image"
+	"io"
+
+	"github.com/chai2010/webp"
+)
+
+type WebpCoder struct{}
+
+func (coder WebpCoder) Decode(r io.Reader) (image.Image, error) {
+	i, err := webp.Decode(r)
+	if err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (coder WebpCoder) Encode(i image.Image, quality int) (buf bytes.Buffer, err error) {
+	if err = webp.Encode(&buf, i, &webp.Options{Lossless: true, Quality: float32(quality)}); err != nil {
+		return buf, err
+	}
+	return buf, nil
+}