go/golang：加水印

package utils

import (
    "errors"
    "fmt"
    "image"
    "image/color"
    "image/draw"
    "image/gif"
    "image/jpeg"
    "image/png"
    "io/ioutil"
    "math/rand"
    "os"
    "path"
    "time"

    "git.code.oa.com/fip-team/rasse/xlog"
    "github.com/golang/freetype"
)

// 水印的位置
const (
    TopLeft int = iota
    TopRight
    BottomLeft
    BottomRight
    Center
)

//字体路径
var Ttf string

type Water struct {
    Pattern string //增加按时间划分的子目录：默认没有时间划分的子目录
}

func (w *Water) New(SavePath, fileName string, typeface []FontInfo) error {
    var subPath string
    subPath = w.Pattern
    dirs, err := CreateDir(SavePath, subPath)
    if err != nil {
        return err
    }

    xlog.Info("dirs=", dirs)
    imgfile, _ := os.Open(fileName)
    defer imgfile.Close()
    _, str, err := image.DecodeConfig(imgfile)
    if err != nil {
        return err
    }
    newName := fmt.Sprintf("%s%s", dirs, path.Base(fileName))
    xlog.Info("fileName=", fileName)
    xlog.Info("newName=", newName)
    if str == "gif" {
        err = gifFontWater(fileName, newName, typeface)
    } else {
        err = staticFontWater(fileName, newName, str, typeface)
    }
    return err
}

//gif图片水印
func gifFontWater(file, name string, typeface []FontInfo) (err error) {
    imgfile, _ := os.Open(file)
    defer imgfile.Close()
    var err2 error
    gifimg2, _ := gif.DecodeAll(imgfile)
    gifs := make([]*image.Paletted, 0)
    x0 := 0
    y0 := 0
    yuan := 0
    for k, gifimg := range gifimg2.Image {
        img := image.NewNRGBA(gifimg.Bounds())
        if k == 0 {
            x0 = img.Bounds().Dx()
            y0 = img.Bounds().Dy()
        }
        fmt.Printf("%v, %v\n", img.Bounds().Dx(), img.Bounds().Dy())
        if k == 0 && gifimg2.Image[k+1].Bounds().Dx() > x0 && gifimg2.Image[k+1].Bounds().Dy() > y0 {
            yuan = 1
            break
        }
        if x0 == img.Bounds().Dx() && y0 == img.Bounds().Dy() {
            for y := 0; y < img.Bounds().Dy(); y++ {
                for x := 0; x < img.Bounds().Dx(); x++ {
                    img.Set(x, y, gifimg.At(x, y))
                }
            }
            img, err2 = common(img, typeface) //添加文字水印
            if err2 != nil {
                break
            }
            //定义一个新的图片调色板img.Bounds()：使用原图的颜色域，gifimg.Palette：使用原图的调色板
            p1 := image.NewPaletted(gifimg.Bounds(), gifimg.Palette)
            //把绘制过文字的图片添加到新的图片调色板上
            draw.Draw(p1, gifimg.Bounds(), img, image.ZP, draw.Src)
            //把添加过文字的新调色板放入调色板slice
            gifs = append(gifs, p1)
        } else {
            gifs = append(gifs, gifimg)
        }
    }
    if yuan == 1 {
        return errors.New("gif: image block is out of bounds")
    } else {
        if err2 != nil {
            return err2
        }
        //保存到新文件中
        newfile, err := os.Create(name)
        if err != nil {
            return err
        }
        defer newfile.Close()
        g1 := &gif.GIF{
            Image:     gifs,
            Delay:     gifimg2.Delay,
            LoopCount: gifimg2.LoopCount,
        }
        err = gif.EncodeAll(newfile, g1)
        return err
    }
}

//png,jpeg图片水印
func staticFontWater(file, name, status string, typeface []FontInfo) (err error) {
    //需要加水印的图片
    imgfile, _ := os.Open(file)
    defer imgfile.Close()
    var staticImg image.Image
    if status == "png" {
        staticImg, _ = png.Decode(imgfile)
    } else {
        staticImg, _ = jpeg.Decode(imgfile)
    }
    img := image.NewNRGBA(staticImg.Bounds())
    for y := 0; y < img.Bounds().Dy(); y++ {
        for x := 0; x < img.Bounds().Dx(); x++ {
            img.Set(x, y, staticImg.At(x, y))
        }
    }
    img, err = common(img, typeface) //添加文字水印
    if err != nil {
        return err
    }
    //保存到新文件中
    newfile, err := os.Create(name)
    if err != nil {
        return err
    }
    defer newfile.Close()
    if status == "png" {
        err = png.Encode(newfile, img)
    } else {
        err = jpeg.Encode(newfile, img, &jpeg.Options{100})
    }
    return err
}

//添加文字水印函数
func common(img *image.NRGBA, typeface []FontInfo) (*image.NRGBA, error) {
    var err2 error
    //拷贝一个字体文件到运行目录
    fontBytes, err := ioutil.ReadFile(Ttf)
    if err != nil {
        err2 = err
        return nil, err2
    }
    font, err := freetype.ParseFont(fontBytes)
    if err != nil {
        err2 = err
        return nil, err2
    }
    errNum := 1
Loop:
    for _, t := range typeface {
        info := t.Message
        f := freetype.NewContext()
        f.SetDPI(108)
        f.SetFont(font)
        f.SetFontSize(t.Size)
        f.SetClip(img.Bounds())
        f.SetDst(img)
        f.SetSrc(image.NewUniform(color.RGBA{R: t.R, G: t.G, B: t.B, A: t.A}))
        //第一行的文字
        // pt := freetype.Pt(img.Bounds().Dx()-len(info)*4-20, img.Bounds().Dy()-100)
        first := 0
        two := 0
        switch int(t.Position) {
        case 0:
            first = t.Dx
            two = t.Dy + int(f.PointToFixed(t.Size)>>6)
        case 1:
            first = img.Bounds().Dx() - len(info)*4 - t.Dx
            two = t.Dy + int(f.PointToFixed(t.Size)>>6)
        case 2:
            first = t.Dx
            two = img.Bounds().Dy() - t.Dy
        case 3:
            first = img.Bounds().Dx() - len(info)*4 - t.Dx
            two = img.Bounds().Dy() - t.Dy
        case 4:
            first = (img.Bounds().Dx() - len(info)*4) / 2
            two = (img.Bounds().Dy() - t.Dy) / 2
        default:
            errNum = 0
            break Loop
        }
        // fmt.Printf("%v, %v, %v\n", first, two, info)
        pt := freetype.Pt(first, two)
        _, err = f.DrawString(info, pt)
        if err != nil {
            err2 = err
            break
        }
    }
    if errNum == 0 {
        err2 = errors.New("坐标值不对")
    }
    return img, err2
}

//定义添加的文字信息
type FontInfo struct {
    Size     float64 //文字大小
    Message  string  //文字内容
    Position int     //文字存放位置
    Dx       int     //文字x轴留白距离
    Dy       int     //文字y轴留白距离
    R        uint8   //文字颜色值RGBA中的R值
    G        uint8   //文字颜色值RGBA中的G值
    B        uint8   //文字颜色值RGBA中的B值
    A        uint8   //文字颜色值RGBA中的A值
}

//生成图片名字
func getRandomString(lenght int) string {
    str := "0123456789abcdefghijklmnopqrstuvwxyz"
    bytes := []byte(str)
    bytesLen := len(bytes)
    result := []byte{}
    r := rand.New(rand.NewSource(time.Now().UnixNano()))
    for i := 0; i < lenght; i++ {
        result = append(result, bytes[r.Intn(bytesLen)])
    }
    return string(result)
}

//检查并生成存放图片的目录
func CreateDir(SavePath, subPath string) (string, error) {
    var dirs string
    if subPath == "" {
        dirs = fmt.Sprintf("%s/", SavePath)
    } else {
        dirs = fmt.Sprintf("%s/%s/", SavePath, time.Now().Format(subPath))
    }
    _, err := os.Stat(dirs)
    if err != nil {
        err = os.MkdirAll(dirs, os.ModePerm)
        if err != nil {
            return "", err
        }
    }
    return dirs, nil
}