c#裁剪圖片後使用zxing產生二維碼

private void button1_Click(object sender, EventArgs e)        {            if (string.IsNullOrEmpty(this.textBox1.Text.Trim()))            {                MessageBox.Show("請輸入需要轉換的資訊！");                return;            }            string content = textBox1.Text;            Hashtable hints= new Hashtable();               hints.Add(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);//錯誤修正層級            hints.Add(EncodeHintType.CHARACTER_SET, "UTF-8");//編碼格式            ByteMatrix byteMatrix = new MultiFormatWriter().encode(content, BarcodeFormat.QR_CODE, 300, 300, hints);            Bitmap bitmap = toBitmap(byteMatrix);            pictureBox1.Image = bitmap;            SaveFileDialog sFD = new SaveFileDialog();            sFD.Filter = "*.png|*.png";            sFD.AddExtension = true;            try            {                if (sFD.ShowDialog() == DialogResult.OK)                {                    writeToFile(byteMatrix, System.Drawing.Imaging.ImageFormat.Png, sFD.FileName);                }            }            catch (Exception ex)            {                MessageBox.Show(ex.Message);            }        }        public static void writeToFile(ByteMatrix matrix, System.Drawing.Imaging.ImageFormat format, string file)        {            System.Drawing.Imaging.EncoderParameters eps = new System.Drawing.Imaging.EncoderParameters();            eps.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);            Bitmap bmap = toBitmap(matrix);            bmap.Save(file, format);        }        public static Bitmap toBitmap(ByteMatrix matrix)        {            int width = matrix.Width;            int height = matrix.Height;            Bitmap bmap = new Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);            for (int x = 0; x < width; x++)            {                for (int y = 0; y < height; y++)                {                    bmap.SetPixel(x, y, matrix.get_Renamed(x, y) != -1 ? ColorTranslator.FromHtml("Purple") : ColorTranslator.FromHtml("0xFFFFFFFF"));//可以自訂色彩和背景色                }            }            return bmap;             }