。net 不用api就行
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缩放操作
Function 缩放(ByVal bitmap As Bitmap, ByVal 倍数 As Single) As Bitmap
Dim w As Integer = bitmap.Width * 倍数
Dim h As Integer = bitmap.Height * 倍数
Dim tem As New Bitmap(w, h)
Dim g As Graphics = Graphics.FromImage(tem)
g.DrawImage(bitmap, New Rectangle(0, 0, w, h), New Rectangle(0, 0, bitmap.Width, bitmap.Height), GraphicsUnit.Pixel)
g.Dispose()
Return tem
End Function
鼠标滚轮事件 MouseWheel
MouseEventArgs.Delta 值可以判断滚动方向
在VB中，并没有包含鼠标滚轮的滚动事件，所以必须用API自己捕获滚动信息并加以处理。主要需要用到CallWindowProc和SetWindowLong两个函数，请参考以下代码：
’在模块中
‘声明方法
Declare Function CallWindowProc Lib "user32 " Alias "CallWindowProcA " (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Declare Function SetWindowLong Lib "user32 " Alias "SetWindowLongA " (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Const GWL_WNDPROC = (-4)
Public Const WM_MOUSEWHEEL = H20A
Public PrevWndProc As Long
Function WndProc(ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long ‘写自己处理鼠标滚动的事件，这里让Form上下滚动
Dim t(0 To 1) As Integer
If uMsg = WM_MOUSEWHEEL Then
If wParam 0 Then 'backward
Form1.Top = Form1.Top + 10
Else 'forforward
Form1.Top = Form1.Top - 10
End If
Else
WndProc = CallWindowProc(PrevWndProc, hwnd, uMsg, wParam, lParam) ‘让Windows处理其他事件
End If
End Function
然后在Form中写入：
Option Explicit
Private Sub Form_Load()
PrevWndProc = SetWindowLong(Me.hwnd, GWL_WNDPROC, AddressOf WndProc) ‘让WndProc来处理该窗体的事件
End Sub
Private Sub Form_Unload(Cancel As Integer)
Dim lResult As Long
lResult = SetWindowLong(Me.hwnd, GWL_WNDPROC, PrevWndProc) ‘让Windows默认的函数来处理事件
End Sub
关于CallWindowProc和SetWindowLong您可以参考以下文章：
SetWindowLong
CallWindowProc
1、滚动条分为水平滚动条（HSCROLLBAR）和垂直滚动条(VSCROLLBAR)两种，可以作为输入设备或者速度、数量的指示器来使用. 2、基本属性：object.max[=value],object.min[=value],最大最小范围 object.value[=value],
拦截窗口程序消息可以解决
参考 VB王国荣API讲座 讲消息的那章
几个API就可以搞定
点击panel时得到panel的焦点，就可以用鼠标滚轮来控制滚动条了！代码如下：
Private Sub Panel1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Panel1.Click
Panel1.Focus()
End Sub
VB可以使用子类化处理鼠标滚轮消息。
新建工程
在窗体中添加滚动条VScroll1
'窗体代码
Private Sub Form_Load()
'取得控件的句柄
hwndVS = VScroll1.hwnd
'保存smMap控件的默认窗口消息处理函数地址
OldWindowProc = GetWindowLong(VScroll1.hwnd, GWL_WNDPROC)
'将smMap控件的消息处理函数指定为自定义函数NewWindowProc
Call SetWindowLong(VScroll1.hwnd, GWL_WNDPROC, AddressOf NewWindowProc)
End Sub
添加一模块：
Option Explicit
Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Const GWL_WNDPROC = -4
Public Const WM_MOUSEWHEEL = H20A
Public OldWindowProc As Long '用来保存系统默认的窗口消息处理函数的地址
Public hwndVS As Long '用来保存控件的句柄
'自定义的消息处理函数
Public Function NewWindowProc(ByVal hwnd As Long, ByVal msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
On Error Resume Next
If msg = WM_MOUSEWHEEL Then
'则对鼠标滚轮事件进行处理
If wParam = -7864320 Then '向下滚动
Form1.VScroll1.Value = Form1.VScroll1.Value + 1
ElseIf wParam = 7864320 Then '向上滚动
Form1.VScroll1.Value = Form1.VScroll1.Value - 1
End If
Else
'调用默认窗口消息处理函数
NewWindowProc = CallWindowProc(OldWindowProc, hwnd, msg, wParam, lParam)
End If
End Function
