Create QRCode with C# and save it as an image

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.

Solution

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 (version: 0.16.8)

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);

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