golang 图片裁切功能

package controllers

import (
    "errors"
    "image"
    "image/gif"
    "image/jpeg"
    "image/png"
    "log"
    "os"
    "path/filepath"
    "strings"
)

type ImageControl struct {
}

func (this *ImageControl) Trimming(before_filename string, after_filename string, x, y, w, h int) {
    src, err := this.LoadImage(before_filename)
    if err != nil {
        log.Println("load image fail..")
    }

    img, err := this.ImageCopy(src, x, y, w, h)
    if err != nil {
        log.Println("image copy fail...")
    }
    saveErr := this.SaveImage(after_filename, img)
    if saveErr != nil {
        log.Println("save image fail..")
    }
}

func (this *ImageControl) LoadImage(path string) (img image.Image, err error) {
    file, err := os.Open(path)
    if err != nil {
        return
    }
    defer file.Close()
    img, _, err = image.Decode(file)
    return
}

func (this *ImageControl) SaveImage(p string, src image.Image) error {
    f, err := os.OpenFile(p, os.O_SYNC|os.O_RDWR|os.O_CREATE, 0666)

    if err != nil {
        return err
    }
    defer f.Close()
    ext := filepath.Ext(p)

    if strings.EqualFold(ext, ".jpg") || strings.EqualFold(ext, ".jpeg") {

        err = jpeg.Encode(f, src, &jpeg.Options{Quality: 80})

    } else if strings.EqualFold(ext, ".png") {
        err = png.Encode(f, src)
    } else if strings.EqualFold(ext, ".gif") {
        err = gif.Encode(f, src, &gif.Options{NumColors: 256})
    }
    return err
}

func (this *ImageControl) ImageCopy(src image.Image, x, y, w, h int) (image.Image, error) {

    var subImg image.Image

    if rgbImg, ok := src.(*image.YCbCr); ok {
        subImg = rgbImg.SubImage(image.Rect(x, y, x+w, y+h)).(*image.YCbCr) //图片裁剪x0 y0 x1 y1
    } else if rgbImg, ok := src.(*image.RGBA); ok {
        subImg = rgbImg.SubImage(image.Rect(x, y, x+w, y+h)).(*image.RGBA) //图片裁剪x0 y0 x1 y1
    } else if rgbImg, ok := src.(*image.NRGBA); ok {
        subImg = rgbImg.SubImage(image.Rect(x, y, x+w, y+h)).(*image.NRGBA) //图片裁剪x0 y0 x1 y1
    } else {

        return subImg, errors.New("图片解码失败")
    }

    return subImg, nil
}