QRCodeGenerator qrGenerator = new QRCodeGenerator();
QRCodeData qrCodeData = qrGenerator.CreateQrCode(content, QRCodeGenerator.ECCLevel.M,true);
var qrCode = new BitmapByteQRCode(qrCodeData);
byte[] qrCodeAsBitmapByteArr = qrCode.GetGraphic(5);
//这种方式保存的图片，微信小程序wx.showShareImageMenu无法调用 ，会提示showShareImageMenu:fail invalid
//var fs = new FileStream(pathFull, FileMode.Create);
//fs.Write(qrCodeAsBitmapByteArr, 0, qrCodeAsBitmapByteArr.Length);
//fs.Dispose();
//这种方法可以明确为图片
var ms = new MemoryStream(qrCodeAsBitmapByteArr);
Bitmap bitmap = new Bitmap(ms);
bitmap.Save(pathFull, ImageFormat.Jpeg);