用C#创建二维码并保存为图片

Question

I'm receiving data from a URL on our web application that's dynamically generated using an API's response. I have to handle it by putting it in a QRCode and send this QRCode back to the front-end for my client to download it. We're using C# for back-end and React.js for the front-end.

I've tried to use ZXIng libraries for C# but with no success. I've tried a lot of code, but nothing seems to happen.

Answer 1

Try the following code. It's been tested, but you may need to adapt it for your usage which shouldn't be too difficult.

Download/install NuGet package: ZXing.Net

Add the following using directives :

• using System.IO;
• using ZXing;
• using ZXing.Common;
• using ZXing.QrCode;

Code :

private Bitmap CreateQrCode(string data)
{
    //specify desired options
    QrCodeEncodingOptions options = new QrCodeEncodingOptions()
    {
        CharacterSet = "UTF-8",
        DisableECI = true,
        Width = 250,
        Height = 250
    };

    //create new instance and set properties
    BarcodeWriter writer = new BarcodeWriter()
    {
        Format = BarcodeFormat.QR_CODE,
        Options = options
    };

    //create QR code and return Bitmap
    return writer.Write(data);
}

private byte[] GetQrCodeBytes(string data, System.Drawing.Imaging.ImageFormat imgFormat)
{
    using (MemoryStream ms = new MemoryStream())
    {
        //create QR code and save to file
        using (Bitmap bmp = CreateQrCode(data))
        {
            //save to MemoryStream
            bmp.Save(ms, imgFormat);
        }

        return ms.ToArray();
    }
}

private string GetTextFromQrCode(byte[] qrcodeBytes)
{
    //specify desired options
    DecodingOptions options = new DecodingOptions()
    {
        CharacterSet = "UTF-8"
    };

    //create new instance and set properties
    BarcodeReader reader = new BarcodeReader() { Options = options };

    using (MemoryStream ms = new MemoryStream(qrcodeBytes))
    {
        using (Bitmap bmp = (Bitmap)Bitmap.FromStream(ms))
        {
            //decode QR code
            Result r = reader.Decode(bmp);

            //return QR code text
            return r.Text;
        }
    }
}

private string GetTextFromQrCode(string filename)
{
    //specify desired options
    DecodingOptions options = new DecodingOptions()
    {
        CharacterSet = "UTF-8"
    };

    //create new instance and set properties
    BarcodeReader reader = new BarcodeReader() { Options = options };

    //read image and convert to Bitmap
    using (Bitmap bmp = (Bitmap)Bitmap.FromFile(filename))
    {
        //decode QR code
        Result r = reader.Decode(bmp);

        //return QR code text
        return r.Text;
    }
}

private void SaveQrCode(string data, string filename, System.Drawing.Imaging.ImageFormat imgFormat)
{
    //create QR code and save to file
    using (Bitmap bmp = CreateQrCode(data))
    {
        bmp.Save(filename, imgFormat);
    }
}

---

Decode QR Code (Usage 1):

string filename = @"C:\Temp\TestQrCode.png"
string qrcodeText = GetTextFromQrCode(filename);

Decode QR Code (Usage 2):

Note : In the code below, the QR code is read from a file and placed in a byte[] . Reading from a file is for demonstration/testing purposes.

string filename = @"C:\Temp\TestQrCode.png"
byte[] qrcodeBytes = File.ReadAllBytes(filename);
string qrcodeText = GetTextFromQrCode(qrcodeBytes);

---

Save QR Code (Usage 1):

string qrcodeText = "This is a test";
string filename = @"C:\Temp\TestQrCode.png"

//get filename extension
string ext = Path.GetExtension(filename);

if (ext == ".bmp" || ext == ".dib" || ext == ".rle")
    SaveQrCode(qrcodeText, filename, System.Drawing.Imaging.ImageFormat.Bmp);
else if (ext == ".jpg" || ext == ".jpeg" || ext == ".jfif" || ext == ".jpe")
    SaveQrCode(qrcodeText, fileName, System.Drawing.Imaging.ImageFormat.Jpeg);
else if (ext == ".png")
    SaveQrCode(qrcodeText, fileName, System.Drawing.Imaging.ImageFormat.Png);

Save QR Code (Usage 2):

Note : In the code below, the QR code is saved to a byte[] , then written to a file. Writing to a file is for demonstration/testing purposes.

string qrcodeText = "This is a test";
string filename = @"C:\Temp\TestQrCode.png"

//get filename extension
string ext = Path.GetExtension(filename);

byte[] qrcodeBytes = null;

if (ext == ".bmp" || ext == ".dib" || ext == ".rle")
    qrcodeBytes = GetQrCodeBytes(qrcodeText, System.Drawing.Imaging.ImageFormat.Bmp);
else if (ext == ".jpg" || ext == ".jpeg" || ext == ".jfif" || ext == ".jpe")
    qrcodeBytes = GetQrCodeBytes(qrcodeText, System.Drawing.Imaging.ImageFormat.Jpeg);
else if (ext == ".png")
    qrcodeBytes = GetQrCodeBytes(qrcodeText, System.Drawing.Imaging.ImageFormat.Png);

//save to file
File.WriteAllBytes(fileName, qrcodeBytes);

---

Resources

• How to read and create barcode images using C# and ZXing.NET
• Basic with QR Code using Zxing Library
• Setting the filter to an OpenFileDialog to allow the typical image formats?