35 lines
652 B
Go
35 lines
652 B
Go
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)
|
|
}
|