.net - 使用鼠标在图片框图像上绘制 vb.net

Question

如何在 vb.net 中使用鼠标在图片框图像上绘制线条或画笔？

Answer 1

使用一行测试和工作，将类似的问题从 C#转换为 VB.NET：

Private _Previous As System.Nullable(Of Point) = Nothing
Private Sub pictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
  _Previous = e.Location
  pictureBox1_MouseMove(sender, e)
End Sub

Private Sub pictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
  If _Previous IsNot Nothing Then
    If PictureBox1.Image Is Nothing Then
      Dim bmp As New Bitmap(PictureBox1.Width, PictureBox1.Height)
      Using g As Graphics = Graphics.FromImage(bmp)
        g.Clear(Color.White)
      End Using
      PictureBox1.Image = bmp
    End If
    Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
      g.DrawLine(Pens.Black, _Previous.Value, e.Location)
    End Using
    PictureBox1.Invalidate()
    _Previous = e.Location
  End If
End Sub

Private Sub pictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
  _Previous = Nothing
End Sub

Answer 2

我已经修改了您的代码以放置一个“点”，可以在鼠标单击时移动（覆盖）

我需要的是这个用于多个“点”，比如四个。

用户从列表中选择一个标记，并将其放在图片框上，然后他们选择另一个并放置在不同的位置，但是它会覆盖以前的标记。

Marker = Lst_Markers.SelectedIndex + 1
If _Previous IsNot Nothing Then
  For i As Integer = 0 To Marker
    Dim bmp As New Bitmap(PictureBox1.Width, PictureBox1.Height)
    PictureBox1.Image = bmp
  Next
  Select Case Marker
    Case 1
      'PictureBox1.Image = bmp1
      Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
        g.FillEllipse(Brushes.Red, e.X, e.Y, 10, 10)
      End Using
    Case 2
      'PictureBox1.Image = bmp2
      Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
        g.FillEllipse(Brushes.Yellow, e.X, e.Y, 10, 10)
      End Using
    Case 3
      'PictureBox1.Image = bmp3
      Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
        g.FillEllipse(Brushes.Green, e.X, e.Y, 10, 10)
      End Using
    Case 4
      'PictureBox1.Image = bmp4
      Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
        g.FillEllipse(Brushes.Blue, e.X, e.Y, 10, 10)
      End Using
    Case Else
      MsgBox("Select a marker")
  End Select
  PictureBox1.Invalidate()
  _Previous = e.Location
End If