forked from go/golangs_learn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
40 lines
811 B
40 lines
811 B
3 years ago
|
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)
|
||
|
}
|