这是我找到此网站后的第一个问题。

我目前正在尝试创建一个VB.NET用户控件，该控件包含一个面板，在该面板上一些 在Paint事件期间应绘制图形对象（圆形，矩形，直线）。 可以简化面板始终为正方形（宽度=高度）的情况。 不幸的是，使用图片框进行绘制不是我的选择。我也不要 使用自动滚动并具有可见的滚动条。

该面板应可由用户平移/缩放。平移应通过按 鼠标中键和缩放应通过滚动鼠标滚轮来完成。 我已经找到了很好的示例，说明如何实现这些功能，到目前为止，它们都有效 很好。 现在，我还想添加用户应该能够缩放到特定位置的功能 面板的（正方形）区域，由他按下时显示的选择矩形 按下鼠标左键时，鼠标左键的大小会调整 左键。 （这应该是类似的行为，例如，放大到PDF文档）。 这是我被卡住的原因。

我提取了负责面板及其事件的代码部分， 这是我到目前为止的内容：

Public Class Form1

    Private zoomstart as Point
    Private zoomfirst as Point
    Private zoomwidth as Integer    
    Private zoomrect as Rectangle
    Private WithEvents tmrMarch as New Timer
    Private MarchOffset as Integer = 0
    Private OffsetDelta as Integer = 2
    Private DashPattern() as Single = {5,5}

    Private zoom As Single = 1.0
    Private startx as Integer = 0
    Private starty as Integer = 0
    Private offsetx as Integer = 0
    Private offsety as Integer = 0
    Private mouseDownPt as Point
    Private initialwidth As Integer

    Public WithEvents Canvas1 As New Canvas

    Private Enum T_Mouseaction
        Rectanglezooming
        Wheelzooming
        Panning
        None
    End Enum

    Private Mouseaction As T_Mouseaction = T_Mouseaction.None


    Private Sub Form1_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load
        Canvas1.Size = New Size(Me.ClientSize.Width,Me.ClientSize.Width)
        Canvas1.AutoScroll = False
        initialwidth = Canvas1.Width
        Me.Controls.Add(Canvas1)
    End Sub


    Private Sub Canvas1_Paint(ByVal sender As Object,ByVal e As PaintEventArgs) Handles Canvas1.Paint
        Select Case Mouseaction
            Case T_Mouseaction.None
                e.Graphics.TranslateTransform(offsetx,offsety)
                e.Graphics.ScaleTransform(zoom,zoom)
            Case T_Mouseaction.Panning
                e.Graphics.TranslateTransform(offsetx,zoom)
            Case T_Mouseaction.Rectanglezooming
                e.Graphics.TranslateTransform(offsetx,zoom)
            Case T_Mouseaction.Wheelzooming
                e.Graphics.ScaleTransform(zoom,zoom)
                e.Graphics.TranslateTransform(offsetx,offsety)
        End Select
        Call DrawImage(e.Graphics)
        e.Graphics.ResetTransform
        If Mouseaction = T_Mouseaction.Rectanglezooming Then
            MarchOffset = MarchOffset + OffsetDelta
            Dim pen as New Pen(Color.Black,2)
            pen.DashPattern = DashPattern
            pen.DashOffset = MarchOffset
            pen.Color = Color.Red
            e.Graphics.DrawRectangle(pen,zoomrect)
        End If 
    End Sub


    Private Sub DrawImage(ByVal gr As Graphics)
        Dim rect As Rectangle
        rect = New Rectangle(0,initialwidth,initialwidth)
        gr.FillEllipse(brushes.LightGreen,rect)
        gr.DrawEllipse(Pens.Green,rect)
        rect = New Rectangle(0.375 * initialwidth,0.375 * initialwidth,0.25 * initialwidth,0.375 * initialwidth)
        gr.FillEllipse(brushes.LightBlue,rect)
        gr.DrawEllipse(Pens.Blue,rect)
        rect = New Rectangle(0.1875 * initialwidth,0.625 * initialwidth,0.625 * initialwidth)
        gr.DrawArc(Pens.Red,rect,20,140)
        rect = New Rectangle(0.1875 * initialwidth,0.1875 * initialwidth,0.25 * initialwidth)
        gr.FillEllipse(brushes.White,rect)
        gr.DrawEllipse(Pens.Black,rect)
        rect = New Rectangle(0.25 * initialwidth,0.125 * initialwidth,0.125 * initialwidth)
        gr.FillEllipse(brushes.Black,rect)
        rect = New Rectangle(0.625 * initialwidth,rect)
        rect = New Rectangle(0.6875 * initialwidth,rect)
    End Sub



    Private Sub tmrMarch_Tick(ByVal sender as Object,ByVal e as EventArgs) Handles tmrMarch.Tick
        Canvas1.Refresh
    End Sub    




    Private Sub Canvas1_MouseDown(ByVal sender As Object,ByVal e As MouseEventArgs) Handles Canvas1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Middle Then
            Mouseaction = T_Mouseaction.Panning
            mouseDownPt = e.Location
            startx = offsetx
            starty = offsety
        End If
        If e.Button = Windows.Forms.MouseButtons.Left Then
            zoomstart = e.Location
            tmrMarch.Interval = 100
            tmrMarch.Enabled = True
        End If        
    End Sub

    Private Sub Canvas1_MouseUp(ByVal sender As Object,ByVal e As MouseEventArgs) Handles Canvas1.MouseUp
        Cursor = Cursors.Default
        tmrMarch.Enabled = False
        If Mouseaction = T_Mouseaction.Rectanglezooming Then
            Dim oldzoom as Single = zoom

            zoom = 1 ' <=== ?

            zoom = Math.Truncate(zoom / 0.2) * 0.2

            Dim oldoffsetx,oldoffsety as Integer
            Dim newoffsetx,newoffsety as Integer
            oldoffsetx = CInt(zoomrect.X / oldzoom)
            oldoffsety = CInt(zoomrect.Y / oldzoom)
            newoffsetx = CInt(zoomrect.X / zoom)
            newoffsety = CInt(zoomrect.Y / zoom)

            offsetx = newoffsetx - oldoffsetx + offsetx ' <=== ?
            offsety = newoffsety - oldoffsety + offsety ' <=== ?    
        End If
        Mouseaction = T_Mouseaction.None
        Canvas1.Refresh
    End Sub    


    Private Sub Canvas1_MouseMove(ByVal sender As Object,ByVal e As MouseEventArgs) Handles Canvas1.MouseMove
        If e.Button = Windows.Forms.MouseButtons.Middle
            Cursor = Cursors.Hand
            Dim mousePosnow as Point = e.Location
            Dim deltaX,deltaY as Integer
            deltaX = mousePosnow.X - mouseDownPt.X
            deltaY = mousePosnow.Y - mouseDownPt.Y
            offsetx = CInt(startx + deltaX)
            offsety = CInt(starty + deltaY)
            Mouseaction = T_Mouseaction.Panning
            Canvas1.Refresh
        End If

        If e.Button = Windows.Forms.MouseButtons.Left Then
            Dim loc as Point
            loc = e.Location
            Dim sizex,sizey as Integer
            sizex = Math.Abs(zoomstart.X - loc.X)
            sizey = Math.Abs(zoomstart.Y - loc.Y)
            zoomwidth = Math.Max(sizex,sizey)
            If loc.X < zoomstart.X Then
                zoomfirst.X = loc.X
            Else
                zoomfirst.X = zoomstart.x
            End If
            If loc.Y < zoomstart.Y Then
                zoomfirst.Y = loc.Y
            Else
                zoomfirst.Y = zoomstart.Y
            End If
            If zoomwidth > 10 Then
                Mouseaction = T_Mouseaction.Rectanglezooming
            End If
            zoomrect = New Rectangle(zoomfirst,New Size(zoomwidth,zoomwidth))
            Canvas1.Refresh
        End If        
    End Sub    


    Private Sub Canvas1_MouseWheel(ByVal sender as Object,ByVal e as MouseEventArgs) Handles Canvas1.MouseWheel
        If Mouseaction = T_Mouseaction.Panning Then
            Exit Sub
        End If
        Dim oldzoom as Single = zoom
        If e.Delta > 0 Then
            zoom = zoom + 0.2
        End If
        If e.Delta < 0 Then
            zoom = Math.Max(zoom - 0.2,0.2)
        End If
        Dim mousePosnow as Point = e.Location
        Dim x,y as Integer
        x = mousePosnow.X
        y = mousePosnow.Y
        Dim oldoffsetx,oldoffsety as Integer
        Dim newoffsetx,newoffsety as Integer
        oldoffsetx = CInt(x / oldzoom)
        oldoffsety = CInt(y / oldzoom)
        newoffsetx = CInt(x / zoom)
        newoffsety = CInt(y / zoom)
        offsetx = newoffsetx - oldoffsetx + offsetx
        offsety = newoffsety - oldoffsety + offsety
        Mouseaction = T_Mouseaction.Wheelzooming
        Canvas1.Refresh
    End Sub    


    Private Sub Canvas1_MouseEnter(ByVal sender as Object,ByVal e as EventArgs) Handles Canvas1.MouseEnter
        Canvas1.Focus
    End Sub

    Private Sub Canvas1_MouseLeave(ByVal sender as Object,ByVal e as EventArgs) Handles Canvas1.MouseLeave
        Me.Focus
    End Sub    

End Class


Public Class Canvas
    Inherits Panel

    Public Sub New
        Me.DoubleBuffered = True
    End Sub
End Class

请向Rod Stephens索取笑脸代码，在这种情况下，该代码只是一个占位符 以便稍后在用户控件中绘制图形。 （http://csharphelper.com/blog/2014/11/scale-a-drawing-so-it-fits-a-target-area-in-c/）

在MouseMove事件中已经正确创建了缩放矩形（行进蚂蚁）。 在MouseUp事件中，我要应用缩放并将选定区域缩放为大小 面板的。在Paint事件中，实际缩放由ScaleTransform和 TranslateTransform操作。

但是我不知道如何计算适当的缩放系数和x / y偏移量，因此 所选区域将缩放为面板尺寸。我试图定位用于以下代码 鼠标滚轮缩放。我有点困惑，因为在我看来 实际上涉及两个缩放因子：一个受鼠标滚轮操作影响 另一个链接到选择矩形操作。 我还尝试将缩放系数计算为“ selection.width / panel.width”， 但这只会给面板导航带来“跳跃”的行为，并且无法正确缩放。

任何帮助将不胜感激。预先非常感谢。