Convert base64 string to JPG

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时光取名叫无心
时光取名叫无心 2021-02-08 15:51

I am getting the image as base64 string ( dataurl ), Below is my function that converts the dataurl into the image,

Now if the

2条回答
  •  醉酒成梦
    2021-02-08 16:36

    Here's something which may help, demonstrates quite a few other things too (you need to have two files: flower.jpg and mouse.png to make this work, available in the repository 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 = `
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    `
    
        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
    
    }
    

    You may also want to read the example in https://golang.org/pkg/image/#Decode Hope this helps.

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