Question

我将图像作为base64字符串（dataurl），下面是我将dataurl转换为图像的函数，

现在如果图像是png而不是png库会创建图像，而jpg库会抛出错误，反之亦然。

问题是当我上传png时效果很好但是当我上传jpg文件时返回此错误

JPEG格式无效：缺少SOI标记

func (ProfileController) SetProfilePic(w http.ResponseWriter, r *http.Request) {

    session, _ := session.UserSession.Get(r, "mvc-user-session")

    var fieldMapForBasic map[string]*json.RawMessage
    var f *os.File

    data, _ := ioutil.ReadAll(r.Body)
    json.Unmarshal(data, &fieldMapForBasic)

    image, _ := json.Marshal(fieldMapForBasic["image"])
    coI := strings.Index(string(image), ",")
    rawImage := string(image)[coI+1:]

     // Encoded Image DataUrl //
    unbased, _ := base64.StdEncoding.DecodeString(string(rawImage))

    res := bytes.NewReader(unbased)
    path , _ := os.Getwd()


     // Path to store the image //
    newpath := filepath.Join( path +  "/storage",  strconv.Itoa(session.Values["id"].(int) ))
    os.MkdirAll(newpath, os.ModePerm)
    uid := uuid.NewV4()
    fmt.Println(newpath)

    // if image is png this function will create the image from dataurl string//
    pngI, errPng := png.Decode(res)
    if  errPng == nil {
        f, _ = os.OpenFile(newpath + "/" + uid.String() + ".png", os.O_WRONLY | os.O_CREATE, 0777)
        png.Encode(f, pngI)
        fmt.Println("Png generated")
        user := model.User{}
        user.ProfilePic = "storage/"+ strconv.Itoa(session.Values["id"].(int) ) + "/" + uid.String()
        session.Values["profile_pic"] = user.ProfilePic
        session.Save(r,w)
        database.Connection.Id(session.Values["id"].(int)).Update(&user)
    }else{
        fmt.Println(errPng.Error())
    }


    // If image is Jpg this will generate the Image //
    jpgI, errJpg := jpeg.Decode(res)
    if errJpg == nil {
        f, _ = os.OpenFile(newpath + "/" + uid.String() + ".jpg", os.O_WRONLY | os.O_CREATE, 0777)
        jpeg.Encode(f, jpgI, &jpeg.Options{Quality:75})
        fmt.Println("Jpg created")
    }else {
        fmt.Println(errJpg.Error())
    }


    defer func() {
        f.Close()
    }()


    render.Json(w, "ok")
}

输入dataurl是：

“数据：图像/ JPEG; BASE64，/ 9J / 4AAQSkZJRgABAQEAYABgAAD / 2wBDAAIBAQIBAQICAgICAgICAwUDAwMDAwYEBAMFBwYHBwcGBwcICQsJCAgKCAcHCg0KCgsMDAwMBwkODw0MDgsMDAz / 2wBDAQICAgMDAwYDAwYMCAcIDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAz / wAARCADeAN4DASIAAhEBAxEB / 8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL / 8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4 + Tl5ufo6erx8vP09fb3 + PN6 / 8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL / 8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3 + PN6 / 9oADAMBAAIRAxEAPwDtKKKK / cD8rCiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiii gAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKAP / Z“

这可能会有所帮助

Answer 1

这里有一些可能有用的东西，也展示了其他一些东西（你需要有两个文件：flower.jpg和mouse.png来完成这项工作，可以在资源库https://github.com/rravishankar/golangtraining/tree/master/test/jpegencode中找到）：

package main

import (
    "bufio"
    "encoding/base64"
    "fmt"
    "image"
    "image/jpeg"
    "image/png"
    "strings"

    "log"
    "os"
)

func main() {

    createJpg()
    createPng()
    base64toPng()
    base64toJpg(getJPEGbase64("flower.jpg"))
}

//Take an existing jpg srcFileName and decode/encode it
func createJpg() {

    srcFileName := "flower.jpg"
    dstFileName := "newFlower.jpg"
    // Decode the JPEG data. If reading from file, create a reader with
    reader, err := os.Open(srcFileName)
    if err != nil {
        log.Fatal(err)
    }
    defer reader.Close()
    //Decode from reader to image format
    m, formatString, err := image.Decode(reader)
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Got format String", formatString)
    fmt.Println(m.Bounds())

    //Encode from image format to writer
    f, err := os.OpenFile(dstFileName, os.O_WRONLY|os.O_CREATE, 0777)
    if err != nil {
        log.Fatal(err)
        return
    }

    err = jpeg.Encode(f, m, &jpeg.Options{Quality: 75})
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Jpg file", dstFileName, "created")

}

//Take an existing png srcFileName and decode/encode it
func createPng() {
    srcFileName := "mouse.png"
    dstFileName := "newMouse.png"
    reader, err := os.Open(srcFileName)
    if err != nil {
        log.Fatal(err)
    }
    defer reader.Close()
    //Decode from reader to image format
    m, formatString, err := image.Decode(reader)
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Got format String", formatString)
    fmt.Println(m.Bounds())

    //Encode from image format to writer
    f, err := os.OpenFile(dstFileName, os.O_WRONLY|os.O_CREATE, 0777)
    if err != nil {
        log.Fatal(err)
        return
    }

    err = png.Encode(f, m)
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Png file", dstFileName, "created")

}

//Converts pre-existing base64 data (found in example of https://golang.org/pkg/image/#Decode) to test.png
func base64toPng() {
    const data = `
/9j/4AAQSkZJRgABAQIAHAAcAAD/2wBDABALDA4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdA
SFxOQERXRTc4UG1RV19iZ2hnPk1xeXBkeFxlZ2P/2wBDARESEhgVGC8aGi9jQjhCY2NjY2NjY2NjY2Nj
Y2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2P/wAARCABnAJYDASIAAhEBAxEB/8QA
HwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIh
MUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVW
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x8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQF
BgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAV
YnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOE
hYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq
8vP09fb3+Pn6/9oADAMBAAIRAxEAPwDlwKMD0pwzSiuK57QzGDxS7D6in8Y5ximnAPUfSlcq4m3ilUYp
2OKXHvRcVxnTtS7c07HNFK4DQPakC4PNOA+tOx70XAjK/So5gBGP94fzqfvUVx/qxx/EP51UXqRP4WSE
cmgjilP3jSEZqS0IO/NGDnpUiocDg/McDjvV6HTPOdVWYgsM5KcfzzQ2JySM2jp6VYu7SWzmMUwG4cgj
kMPUVBjjtTGtRu0Zopw+lFFxhinrGzuqqMsxAA9yaXFSRv5cqSEcIwYj6GpuZ30O30fSLKzhUpbpNMv3
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ALy/zq1t96r3y4tT/vL/ADq4P3kRP4WSleTSFKkkKoCW4GaqNcMxIjXj1pxjKT0FKrGC1Nrw3vGrKkYz
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oOxPU/8A68VVtbbRtMVntbePKDLTSHJH/Aj/AEqHTvE66rq72VugMMcbSGTnL4wMAfjT5n0HyW3L+s6b
baxaJBdzN+7bcrxkAhun0rz3VNCv7e7lgigknWI43xLu6jjIHTjtXqfkpPGVYsBkghTikgsYIN/lhgXb
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Bo1gM/uW55/1jf41nOipu7LhV5FZHIGzI6zwj/vr/Ck+yr3uYf8Ax7/CutbQdMb71tn/ALaN/jSf8I/p
X/PoP++2/wAan6rAr6wzkWt0II+1Rc/7Lf4Vd1eeCSKBbdZDdShYoiZNoyfY10P/AAj2lf8APmP++2/x
oPh/SjKspsozIuNrZORjp3qo0FHYPb3OZt7ae3SzjuItsiRSAgnccl/UA+3Q1yNjKLR4ZZYY5VD7tkv3
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GHk245CZ6/X1qPTLq40q+W5t2QybSpDAkEEc55/zilk5k2r91eKhLDzWz2rpsczbbuemeD76fUNG865I
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KoiBZOV9JBnt707MVy5RWdNdy7wRGf3bfMinnO1jg+vY03WXLaJO3mhQ20b0zwpYf0qlG7S7icrJs08U
VwumgC+YiQyeVtZH567hzj8aSL949oGhE/2v5pJCDkksQwBHC4/+vXQ8LZ2uYxxCavY7us/xCcaBfn0h
b+VP0bnSrb94ZMJgOecj1rl/GfidUE2k2gy5+SeQjgA/wj3rlas2jdao48qrjLAGkSKPk4Gc1WMj92I+
lIJnU8OfxPWo5inBokmtQTmM4OOh71b0q6vbFmWCbaxHyqQGAP0PT8KhSTzVyo5ocSKA5VfTOTmqsmRd
pl99XjPzThzK3zOeOSeveirNmkgg/fIpYsTkYORxRXmzlTjJqx6EVUcU7mhkKCzdAK59QI9zYxtG1fYU
UVtgtmY4nZEa8Ak9aqFv3rfSiiu1nMeifDv/AJF+T/r4f+QrqqKKQwzQenNFFMCOKFIgNuThdoJ5OPSk
ubeK6t3gnXdG4wwziiii/UTKMOg6dbzJLFE4dSCP3rEdeOM8805tDsGMvySgSsS6rM6gk9eAcUUVftZt
3uyVGNthuq3Eei6DK8H7sRR7YuMgHtXkc8rzTNLM26RyWY+p70UVnLY0iEsUipG7rhZBlDkc1HgYoorM
0HwyBXGeRjmrcUhMg2ghezd//rUUVcTKW5s2jZtY/QDaOKKKK8ip8bPRj8KP/9k=
`

    reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
    m, formatString, err := image.Decode(reader)
    if err != nil {
        log.Fatal(err)
    }
    bounds := m.Bounds()
    fmt.Println(bounds, formatString)

    //Encode from image format to writer
    pngFilename := "test.png"
    f, err := os.OpenFile(pngFilename, os.O_WRONLY|os.O_CREATE, 0777)
    if err != nil {
        log.Fatal(err)
        return
    }

    err = png.Encode(f, m)
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Png file", pngFilename, "created")

}

//Given a base64 string of a JPEG, encodes it into an JPEG image test.jpg
func base64toJpg(data string) {

    reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
    m, formatString, err := image.Decode(reader)
    if err != nil {
        log.Fatal(err)
    }
    bounds := m.Bounds()
    fmt.Println("base64toJpg", bounds, formatString)

    //Encode from image format to writer
    pngFilename := "test.jpg"
    f, err := os.OpenFile(pngFilename, os.O_WRONLY|os.O_CREATE, 0777)
    if err != nil {
        log.Fatal(err)
        return
    }

    err = jpeg.Encode(f, m, &jpeg.Options{Quality: 75})
    if err != nil {
        log.Fatal(err)
        return
    }
    fmt.Println("Jpg file", pngFilename, "created")

}

//Gets base64 string of an existing JPEG file
func getJPEGbase64(fileName string) string {

    imgFile, err := os.Open(fileName)

    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    defer imgFile.Close()

    // create a new buffer base on file size
    fInfo, _ := imgFile.Stat()
    var size = fInfo.Size()
    buf := make([]byte, size)

    // read file content into buffer
    fReader := bufio.NewReader(imgFile)
    fReader.Read(buf)

    imgBase64Str := base64.StdEncoding.EncodeToString(buf)
    //fmt.Println("Base64 string is:", imgBase64Str)
    return imgBase64Str

}

您可能还想阅读https://golang.org/pkg/image/#Decode中的示例希望这会有所帮助。

Answer 2

您正在将io.Reader传递给开始使用阅读器的png.Decode()，但却发现输入不是有效的PNG，因此会返回错误。

然后你的部分消费者被传递给jpeg.Decode()，它读取尚未读取的数据，这不是有效的JPEG，并返回你观察到的错误。

您需要为每个解码器创建一个新的阅读器：

pngI, errPng := png.Decode(bytes.NewReader(unbased))

// ...

jpgI, errJpg := jpeg.Decode(bytes.NewReader(unbased))

或者更好的是，考虑MIME类型，只调用正确的解码器：

switch strings.TrimSuffix(image[5:coI], ";base64") {
case "image/png":
    pngI, err = png.Decode(res)
    // ...
case "image/jpeg":
    jpgI, err = jpeg.Decode(res)
    // ...
}

将base64字符串隐藏为JPG

2 个答案: