二维码生成与解码

有三种方式：

1、ZXing.Net

实例源码：

        protected void Page_Load(object sender, EventArgs e)
        {
            DateTime dtBegin = DateTime.Now;

            string fileName = AppDomain.CurrentDomain.BaseDirectory + "bin\" + Guid.NewGuid().ToString() + ".jpg";
            string content = HttpUtility.UrlDecode(this.Request["content"]);
            BarcodeWriter writer = new BarcodeWriter() 
                { 
                    Format = BarcodeFormat.QR_CODE, 
                    Options = new EncodingOptions() 
                        { 
                            Width = 300, 
                            Height = 400 
                        },
                    Renderer = (IBarcodeRenderer<Bitmap>)Activator.CreateInstance(typeof(BitmapRenderer))
                };
            Bitmap bmp = writer.Write(content);
            bmp.Save(fileName);
            this.Response.WriteFile(fileName);

            string time = (DateTime.Now - dtBegin).TotalMilliseconds.ToString();
        }

2、QrCode.Net

实例源码：

        protected void Page_Load(object sender, EventArgs e)
        {
            DateTime dtBegin = DateTime.Now;

            string fileName = AppDomain.CurrentDomain.BaseDirectory + "bin\" + Guid.NewGuid().ToString() + ".jpg";
            string content = HttpUtility.UrlDecode(Request.QueryString["content"]);
            QrEncoder qrEncoder = new QrEncoder(ErrorCorrectionLevel.M);
            QrCode qrCode = qrEncoder.Encode(content);

            GraphicsRenderer renderer = new GraphicsRenderer(new FixedModuleSize(5, QuietZoneModules.Two), Brushes.Black, Brushes.White);
            using (FileStream stream = new FileStream(fileName, FileMode.Create))
            {
                renderer.WriteToStream(qrCode.Matrix, ImageFormat.Png, stream);
            }
            this.Response.WriteFile(fileName);

            string spendTime = (DateTime.Now - dtBegin).TotalMilliseconds.ToString();
        }

3、ThoughtWorks.QRCode

实例源码：

        protected void Page_Load(object sender, EventArgs e)
        {
            DateTime dtBegin = DateTime.Now;

            string content = HttpUtility.UrlDecode(Request.QueryString["content"]);
            Bitmap bitmap = CreateQRCode(content);
            string fileName = AppDomain.CurrentDomain.BaseDirectory + "bin\" + Guid.NewGuid().ToString() + ".jpg";
            
            bitmap.Save(fileName, ImageFormat.Jpeg);            
            Response.WriteFile(fileName,true);

            string spendTime = (DateTime.Now - dtBegin).TotalMilliseconds.ToString();
        }

        public Bitmap CreateQRCode(string content)
        {
            QRCodeEncoder qrEncoder = new QRCodeEncoder();
            qrEncoder.QRCodeEncodeMode = QRCodeEncoder.ENCODE_MODE.BYTE;
            qrEncoder.QRCodeScale = 4; //Convert.ToInt32(txtSize.Text);
            qrEncoder.QRCodeVersion = 7;// Convert.ToInt32(cboVersion.SelectedValue);
            qrEncoder.QRCodeErrorCorrect = QRCodeEncoder.ERROR_CORRECTION.M;
            try
            {
                Bitmap qrcode = qrEncoder.Encode(content, Encoding.UTF8);
                return qrcode;
            }
            catch (IndexOutOfRangeException ex)
            {
                //超出当前二维码版本的容量上限，请选择更高的二维码版本
                return new Bitmap(100, 100);
            }
            catch (Exception ex)
            {
                //生成二维码出错
                return new Bitmap(100, 100);
            }
        }

注意事项：

1、web端请求二维码的一种方式是将生成二维码的服务页面赋给<img>的src属性。

2、三种方式均为开源项目，使用时到官网下载源码，并添加到项目中即可

3、三种方式对比：3的处理速度最快，在web端访问的处理时间大概20ms，1和2的速度达不多，为50ms到70ms左右，但1和2dll较小，几百k，而3为6M

4、方式3的demo运行时有问题，原因待查