Initial commit

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)
+}