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jpeg.go
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jpeg.go
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// Package jpeg provides a JPEG Encoder.
package jpeg
import (
"image"
"image/jpeg"
"io"
"github.com/pierrre/imageserver"
imageserver_image "github.com/pierrre/imageserver/image"
)
// Encoder encodes an Image to JPEG.
type Encoder struct {
DefaultQuality int
}
// Encode implements Encoder.
func (enc *Encoder) Encode(w io.Writer, nim image.Image, params imageserver.Params) error {
opts, err := enc.getOptions(params)
if err != nil {
return err
}
return jpeg.Encode(w, nim, opts)
}
func (enc *Encoder) getOptions(params imageserver.Params) (*jpeg.Options, error) {
opts := &jpeg.Options{}
var err error
opts.Quality, err = enc.getQuality(params)
if err != nil {
return nil, err
}
return opts, nil
}
func (enc *Encoder) getQuality(params imageserver.Params) (int, error) {
if !params.Has("quality") {
if enc.DefaultQuality != 0 {
return enc.DefaultQuality, nil
}
return jpeg.DefaultQuality, nil
}
quality, err := params.GetInt("quality")
if err != nil {
return 0, err
}
if quality < 1 {
return 0, &imageserver.ParamError{Param: "quality", Message: "must be greater than or equal to 1"}
}
if quality > 100 {
return 0, &imageserver.ParamError{Param: "quality", Message: "must be less than or equal to 100"}
}
return quality, nil
}
// Change implements Encoder.
func (enc *Encoder) Change(params imageserver.Params) bool {
if params.Has("quality") {
return true
}
return false
}
func init() {
imageserver_image.RegisterEncoder("jpeg", &Encoder{})
}