VBGood网站全文搜索 Google

搜索VBGood全站网页(全文搜索)
首页 - 经验之谈 - VB中实现“擦视”技术
发表评论(0)作者:不详, 平台:VB6.0+Win98, 阅读:9557, 日期:2000-10-22
VB中实现“擦视”技术

  在电影和电视中应尽量避免“跳跃分隔”的镜头画面,同样VB5软件设计时,窗体间切换时也应该做到平滑自然,这就是所说的“擦视技术”(Wipe)。如何实现“擦视技术”,大家都会想到一个功能强大的API函数——位块传输Bitblt( )函数,本文主要探讨以下两个问题:


(1)Bitblt( )函数只能实现图像的位块传输,那么如何实现背景与控件界面一同擦视;


(2)调用Bitblt( )函数需要传递一长串繁琐的参数,那么如何用一个通用过程将其模块化,使其通用性强,使用简单。


  窗体中的控件虽然不能被擦视,但图像能实现,我们可以首先“拍”下要切换的两个窗体界面的图片,当需要擦视切换时,将一个载有该图片的过渡窗体Show出来,在该窗体上实现擦视切换(以下给出了5种擦视方法),擦视完毕后将其Hide,并将第二个窗体Show出来,这样在视觉上毫无破绽,具体方法如下:


编写一个通用的Wipe过程实现擦视


  (1)在一个新工程中添加一个窗体,该窗体只含一个PictureBox控件,属性设置如下:


  对象 Name AutoRedraw ScaleMode Visible BorderStyle


  Form FrmWipe True 3---pixel 0---None


  PictureBox PicResource True 3---pixel False


  (2)添加一个标准模块Wipe.bas其代码如下:


  Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As- Long, ByVal _ nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As _ Long, ByVal dwRop As Long) As Long


  Public FrmOriginal As Form


  Public FrmNextOne As Form


  Public WipeMode As Integer


  Public strDestine, strResource As String


  ’ 定义Wipe过程


  Public Sub Wipe(iMode As Integer, WipeStrDestine As String, WipeStrResource As String, frmHide As Form,_ frmShow As Form) ‘iMode为擦视方式,WipeStrDestine和WipeStrResource为图片路径,frmHide和


  WipeMode = iMode ‘frmShow为切换窗体


  Set FrmNextOne = frmShow


  Set FrmOriginal = frmHide


  strDestine = WipeStrDestine


  strResource = WipeStrResource


  FrmWipe.Show ‘Show出过度窗体


  End Sub


  (3)在FrmWipe窗体的Form_Initialize( )、Form_Activate( )和Form_Deactivate( )事件中添加代码如下:


  Private Sub Form_Activate()


  Dim iMoveStep, xMax, yMax, iEndMax As Integer


  Dim w, h, iTemp, i, X1, Y1, ij As Integer


  Dim kxy As Single


  Dim blnStop As Boolean


  MousePointer = 11 ’让鼠标成沙漏


  FrmWipe.Picture = LoadPicture(strDestine)


  PicResource.Picture = LoadPicture(strResource)


  blnStop = False


  iMoveStep = 0


  xMax = FrmWipe.ScaleWidth / 2


  yMax = FrmWipe.ScaleHeight / 2


  kxy = yMax / xMax


  h = FrmWipe.ScaleHeight


  While blnStop = False


   Select Case WipeMode ’擦视方式


   Case 1 ’从中间向周围擦视


   iEndMax = xMax


  X1 = xMax - iMoveStep


  w = iMoveStep * 2


  Y1 = CInt(yMax - iMoveStep * kxy)


  h = CInt(2 * iMoveStep * kxy)


  i = BitBlt(FrmWipe.hDC, X1, Y1, w, h, PicResource.hDC, X1, Y1, &HCC0020)


  Case 2 ’从左向右擦视


  iEndMax = xMax


  w = iMoveStep * 2


  i = BitBlt(FrmWipe.hDC, 0, 0, w, h, PicResource.hDC, X1, Y1, &HCC0020)


  Case 3 ’从左右向中间擦视


  iEndMax = xMax


  w = iMoveStep


  i = BitBlt(FrmWipe.hDC, 0, 0, w, h, PicResource.hDC, 0, 0, &HCC0020)


  X1 = ScaleWidth - iMoveStep


  i = BitBlt(FrmWipe.hDC, X1, 0, w, h,


    PicResource.hDC, X1, 0, &HCC0020)


  Case 4 ’呈百叶窗状擦视


  iEndMax = CInt(2 * xMax / 10)


  iTemp = CInt(2 * xMax / 10)


  w = iMoveStep - 7


  For ij = 0 To 9


  i = BitBlt(FrmWipe.hDC, iTemp * ij, 0, w, h,


    PicResource.hDC, iTemp * ij, 0, &HCC0020)


  Next


  Case 5 ’从中间向左右


  iEndMax = xMax


  w = iMoveStep * 2


  X1 = xMax - iMoveStep


  i = BitBlt(FrmWipe.hDC, X1, 0, w, h,


    PicResource.hDC, X1, 0, &HCC0020)


  End Select


  Refresh


  iMoveStep = iMoveStep + 8 ‘加上不同的常量可改变擦视速度


  If iMoveStep > iEndMax Then ‘结束条件


   blnStop = True


   End If


  Wend


  FrmNextOne.Show ’show出第二个窗体


  FrmOriginal.Hide ’隐藏原窗体,也可以Unload


  FrmWipe.Hide ’隐藏过渡窗体,也可以Unload


  End Sub


  Private Sub Form_Deactivate()


  FrmWipe.Picture = LoadPicture() ‘清空图片释放内存


  PicResource.Picture = LoadPicture()


  End Sub


  Private Sub Form_Initialize()


  FrmWipe.WindowState = FrmOriginal.WindowState ’ 使各个窗体的大小、位置一致


  If FrmOriginal.WindowState < > 2 Then


   FrmWipe.Width = FrmNextOne.Width


   FrmWipe.Height = FrmNextOne.Height


   FrmWipe.Top = FrmOriginal.Top


   FrmWipe.Left = FrmOriginal.Left


   FrmNextOne.Top = FrmOriginal.Top


   FrmNextOne.Left = FrmOriginal.Left


   FrmNextOne.Width = FrmOriginal.Width


   FrmNextOne.Height = FrmOriginal.Height


  End If


  End Sub


应用举例


  当程序设计中窗体切换需要擦视时,只需将上述窗体FrmWipe.frm和模块Wipe.bas添加到您的工程中,并在您需要擦视的事件中调用Wipe过程即可轻松地实现擦视技术。假设您需要通过单击按钮(名为cmdChangeToForm1和cmdChangeToForm2),在Form1和Form2间相互擦视切换,可在Form1中的cmdChangeToForm2_Click( )和Form2中的cmdChangeToForm1_Click( )事件中调用Wipe过程。假设“拍”下来两幅界面图片放在:VB5\Background\子目录下名为:PicForm1.jpgPic和PicForm2.jpg。(用Windows中的画图、图片编辑器或PhotoShop均可实现)


  Private Sub cmdChangeToForm2_Click()


  Wipe 4, App.Path + "\back\PicForm1.jpg", App.Path + "\back\PicForm2.jpg", Form1, Form2


  End Sub ‘调用Wipe过程,4表示用第四种方法擦视


  Private Sub cmdChangeToForm1_Click()


  Wipe 1, App.Path + "\back\PicForm2.jpg", App.Path + "\back\PicForm1.jpg", Form2, Form1


  End Sub