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