Question

我想在鼠标移动时绘制椭圆。这是我的代码

Dim released As Boolean = False
Dim firstx As Integer = 0
Dim firsty As Integer = 0

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
    If e.Button = MouseButtons.Left Then
        If released = False Then
            firstx = e.X
            firsty = e.Y
            released = True
        End If
        Dim flag As New Bitmap(PictureBox2.Image) 'This code fills RAM everytime.
        Dim g As Graphics = Graphics.FromImage(flag)
        g.DrawEllipse(New Pen(Color.MediumOrchid, 5), firstx, firsty, e.X - firstx, e.Y - firsty)
        g.Dispose()
        PictureBox1.Image = flag
    Else
        released = False
    End If
End Sub

我知道在MouseMove事件中定义图形会导致这个问题。它会在每一个动作中创建图形。解决方案是什么？

注意： PictureBox1和PictureBox2具有相同的图片。

Answer 1

您不需要为创建位图来获取图形对象引用的开销。

而不是：

Dim flag As New Bitmap(PictureBox2.Image)
Dim g As Graphics = Graphics.FromImage(flag)

试试这个

Dim g As Graphics = PictureBox2.CreateGraphics

然而;你应该做的是在你需要绘制的图片框的绘画事件中处理绘画。

当鼠标移动时，您存储要绘制的椭圆的坐标并调用PictureBox2.Invalidate，这将导致绘制事件。

绘图椭圆使用太多RAM

1 个答案: