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| package image
|
| import (
| "bytes"
| "errors"
| "github.com/nfnt/resize"
| "image"
| "image/jpeg"
| "image/png"
| "strings"
| )
|
| func CreateThumbnail(fileBytes []byte, side, width, height int) ([]byte, error) {
| img, format, err := image.Decode(bytes.NewReader(fileBytes))
| if err != nil {
| return nil, err
| }
|
| var thumbnailImg image.Image
| if side > 0 {
| var canvas image.Image
| s := side
| sz := img.Bounds().Size()
|
| if sz.X > sz.Y {
| canvas = resize.Thumbnail(uint(sz.X), uint(s), img, resize.Lanczos2)
| } else {
| canvas = resize.Thumbnail(uint(s), uint(sz.Y), img, resize.Lanczos2)
| }
| sz = canvas.Bounds().Size()
| var l, t, r, b int
| if sz.X > s {
| l = (sz.X - s) / 2
| r = l + s
| } else {
| l = 0
| r = sz.X
| }
| if sz.Y > s {
| t = (sz.Y - s) / 2
| b = t + s
| } else {
| t = 0
| b = sz.Y
| }
|
| thumbnailImg = canvas.(*image.YCbCr).SubImage(image.Rect(l, t, r, b)).(*image.YCbCr)
| } else {
| w := width
| h := height
| if w > 0 && h > 0 {
| } else if w > 0 {
| h = img.Bounds().Dy()
| } else {
| w = img.Bounds().Dx()
| }
| thumbnailImg = resize.Thumbnail(uint(w), uint(h), img, resize.Lanczos2)
| }
|
| buffer := new(bytes.Buffer)
| format = strings.ToLower(format)
| if format == "jpg" || format == "jpeg" {
| if err := jpeg.Encode(buffer, thumbnailImg, nil); err != nil {
| return nil, err
| }
| } else if format == "png" {
| if err := png.Encode(buffer, thumbnailImg); err != nil {
| return nil, err
| }
| } else {
| return nil, errors.New("不支持的文件格式")
| }
| return buffer.Bytes(), nil
| }
|
|
