隱蔽的base64字符串JPG Golang

我收到圖像爲base64字符串（dataurl），下面是我的函數的dataurl轉換成圖像，隱蔽的base64字符串JPG Golang

現在，如果圖像比爲png庫將創建爲PNG圖像和jpg庫會拋出錯誤，反之亦然。

問題是，當我上傳png格式它工作得很好，但是當我上傳JPG文件
返回該錯誤

無效的JPEG格式：缺少SOI標記

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") 
}

輸入dataurl是：

「的數據：圖像/ JPEG; BASE64，/ 9J/4AAQSkZJRgABAQEAYABgAAD/2wBDAAIBAQIBAQICAgICAgICAwUDAwMDAwYEBAM FBwYHBwcGBwcICQsJCAgKCAcHCg0KCgsMDAwMBwkODw0MDgsMDAz/2wBDAQICAgMDAwYDAwYMCAcIDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAz/wAARCADeAN4DASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4 + Tl5ufo6erx8vP09fb3 + PN6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3 + PN6/9oADAMBAAIRAxEAPwDtKKKK/cD8rCiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACi iigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKAP/Z」

這可能有助於

來源

2017-09-03 mchampaneri

我不知道是什麼「SOI錯誤」的意思是，但你試圖解碼與PNG和JPEG相同的數據（存儲在「res」中）。 – Carpetsmoker

我已更新問題 – mchampaneri

您正在將io.Reader傳遞給png.Decode()，這會開始消費讀者，只會發現輸入不是有效的PNG，因此會返回錯誤。

然後將您部分使用的閱讀器傳遞給jpeg.Decode()，該閱讀器讀取尚未讀取的數據，該數據不是有效的JPEG，並返回您觀察到的錯誤。

你需要爲每個解碼器創建一個新的讀者：

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

// ... 

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

或者更好的是，考慮MIME類型，只調用合適的解碼器：

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

來源

2017-09-06 14:51:55 Flimzy

這工作。但如果你能解釋更多一點，這將是可觀的。我是golang的初學者。 – mchampaneri

你想讓我進一步解釋什麼？ – Flimzy

「部分消耗的閱讀器傳遞給jpeg.Decode（）」。我無法理解這一點。我通過了對於新讀者來說相同的資源。不是嗎？ – mchampaneri

這裏的東西可以幫助演示了其他不少東西太（你需要有兩個文件：爲Flower.jpg和mouse.png，使這項工作，可以在倉庫https://github.com/rravishankar/golangtraining/tree/master/test/jpegencode）：

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 
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HwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIh 
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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 

}

您可能還想閱讀https://golang.org/pkg/image/#Decode 中的示例希望這有助於您。

來源

2017-09-03 15:07:48 Ravi

這是我的Jpg輸入字符串 – mchampaneri

如果缺少SOI標記，那麼base64字符串中可能缺少一些字節（https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format#File_format_structure）修改您的程序打印JPEG的base64字符串。然後使用您的JPEG base64字符串作爲輸入（對'base64toJpg'函數）分別運行我的程序（演示工作） - 查看您是否獲得了JPEG。如果出現錯誤，請查看它是什麼，如果需要，請獲取源JPEG，使用上述代碼中的getJPEGbase64函數獲取base64字符串，並匹配您在http請求中獲得的base64字符串。 – Ravi

我已經測試了base64字符串在線https://codebeautify.org/base64-to-image-converter。它工作正常 – mchampaneri

隱蔽的base64字符串JPG Golang

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