使用手寫筆時PictureBox.Image爲null

Question

我試圖將PictureBox的內容保存到數據庫。這本身運作良好，但是一旦簽名圖片框被繪製，它就不會設置PictureBox.Image屬性，這意味着我無法繼續該過程。

Pen myPen; 
    bool bMouseDown = false; 
    Point prevPoint; 
    Graphics gCust; 
    Graphics gTech; 

private void NewJob_Load(object sender, EventArgs e) 
    { 
     myPen = new System.Drawing.Pen(System.Drawing.Color.Black); 
     gCust = pbCustomerSig.CreateGraphics(); 
     gCust.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 
     myPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Solid; 
     myPen.SetLineCap(LineCap.Round, LineCap.Round, DashCap.Round); 
     myPen.Color = Color.Blue; 
     myPen.Width = 2f; 
} 
public static byte[] ImageToBinary(Image image) 
    { 
     Byte[] buffer = (Byte[])new ImageConverter().ConvertTo(image, typeof(Byte[])); 
     return buffer; 
    } 
private void pbCustomerSig_MouseDown(object sender, MouseEventArgs e) 
    { 
     prevPoint = e.Location; 
     bMouseDown = true; 
    } 

    private void pbCustomerSig_MouseMove(object sender, MouseEventArgs e) 
    { 
     if (bMouseDown) 
     { 
      Point thisPoint = e.Location; 
      if (prevPoint.X == 0 && prevPoint.Y == 0) 
      { 
       prevPoint = thisPoint; 
       return; 
      } 
      gCust.DrawLine(myPen, thisPoint.X, thisPoint.Y, prevPoint.X, prevPoint.Y); 
      prevPoint = thisPoint; 
     } 
    } 

    private void pbCustomerSig_MouseUp(object sender, MouseEventArgs e) 
    { 
     bMouseDown = false; 
    } 

的錯誤是在這裏 -

h.CustomerSignature = ImageToBinary(pbCustomerSig.Image); 

任何想法，爲什麼PictureBox.Image屬性爲null？

非常感謝！

Answer 1

您沒有爲pbCustomerSig.Image分配值。空是正常的。 而不是嘗試繪製到位圖。 Here is a sample for drawing on existing bitmap但您可以使用相同的方式在空白位圖上繪製並同時在圖片框上顯示它。