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package ImageUtil
import (
"errors"
"github.com/nfnt/resize"
"golang.org/x/image/bmp"
"image"
"image/gif"
"image/jpeg"
"image/png"
"io"
)
/*
* 图片裁剪
* 入参:
* 规则:如果精度为0则精度保持不变
*
* 返回:error
*/
func Clip(in io.Reader, out io.Writer, x0, y0, x1, y1, quality int) error {
origin, fm, err := image.Decode(in)
if err != nil {
return err
}
switch fm {
case "jpeg":
img := origin.(*image.YCbCr)
subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.YCbCr)
return jpeg.Encode(out, subImg, &jpeg.Options{quality})
case "png":
switch origin.(type) {
case *image.NRGBA:
img := origin.(*image.NRGBA)
subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.NRGBA)
return png.Encode(out, subImg)
case *image.RGBA:
img := origin.(*image.RGBA)
subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.RGBA)
return png.Encode(out, subImg)
}
case "gif":
img := origin.(*image.Paletted)
subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.Paletted)
return gif.Encode(out, subImg, &gif.Options{})
case "bmp":
img := origin.(*image.RGBA)
subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.RGBA)
return bmp.Encode(out, subImg)
default:
return errors.New("ERROR FORMAT")
}
return nil
}
/*
* 缩略图生成
* 入参:
* 规则: 如果width 或 hight其中有一个为0则大小不变 如果精度为0则精度保持不变
* 矩形坐标系起点是左上
* 返回:error
*/
func Scale(in io.Reader, out io.Writer, width, height, quality int) error {
origin, fm, err := image.Decode(in)
if err != nil {
return err
}
if width == 0 || height == 0 {
width = origin.Bounds().Max.X
height = origin.Bounds().Max.Y
}
if quality == 0 {
quality = 100
}
canvas := resize.Thumbnail(uint(width), uint(height), origin, resize.Lanczos3)
switch fm {
case "jpeg":
return jpeg.Encode(out, canvas, &jpeg.Options{quality})
case "png":
return png.Encode(out, canvas)
case "gif":
return gif.Encode(out, canvas, &gif.Options{})
case "bmp":
return bmp.Encode(out, canvas)
default:
return errors.New("ERROR FORMAT")
}
return nil
}