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package png
import (
"bytes"
"github.com/foobaz/lossypng/lossypng"
"image"
"image/png"
"io"
)
const qMax = 20
// Options represent PNG encoding options.
type Options struct {
Quality int `json:"quality"`
}
// DecodePNG decodes a PNG file and return an image.
func DecodePNG(r io.Reader) (image.Image, error) {
i, err := png.Decode(r)
if err != nil {
return nil, err
}
return i, nil
}
// EncodePNG encodes an image into PNG and returns a buffer.
func EncodePNG(i image.Image, o *Options) (buf bytes.Buffer, err error) {
c := lossypng.Compress(i, 2, qualityFactor(o.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)
}