How To Size a Picture Box Dynamically to Fit an AVI Image

• Microsoft Visual Basic Professional and Enterprise Editions, 32-bit only, for Windows, version 4.0

SUMMARY

To size a picture box to fit an AVI image at run time, you must first get the dimensions of the AVI file. This article demonstrates how to do it.

MORE INFORMATION

The example uses the mciSendCommand function to get the dimensions of the AVI file currently referenced by an MCI control.

Step-by-Step Example

1. Start a new project in Visual Basic. Add a module (.BAS) file, and make sure the MCI control is included in the project. Add a MCI control (MMControl1), a Command Button (Command1), and a Picture box (Picture1) to Form1. Set Form1's ScaleMode property to Pixels (3).



2. In the General declarations section of the .BAS file, add this code:

   
      Type RECT
         Left As Long
         Top As Long
         Right As Long
         Bottom As Long
      End Type
   
      Type MCI_OVLY_RECT_PARMS
         dwCallback As Long
         rc As RECT
      End Type
   
      Global Const MCI_OVLY_WHERE_SOURCE = &H20000
      Global Const MCI_OVLY_WHERE_DESTINATION = &H40000
      Global Const MCI_WHERE = &H843
   
      'Enter the following Declare statement:
   
      Declare Function mciSendCommand Lib "winmm.dll" _
         Alias "mciSendCommandA" ( _
            ByVal wDeviceID As Long, _
            ByVal uMessage As Long, _
            ByVal dwParam1 As Long,
            dwParam2 As Any) As Long
   
      ' Enter the following Declare statement:
      Declare Function mciGetErrorString Lib "winmm.dll" _
         Alias "mciGetErrorStringA" ( _
            ByVal dwError As Long, _
            ByVal lpstrBuffer As String, _
            ByVal uLength As Long) As Long
    




3. In the Command1_Click() method for the Command button on Form1, enter this code:

   
      Sub Command1_Click ()
         Const MB_OK = 0
         Const MB_ICONSTOP = 16
   
         Dim Retval&, Buffer$
         Dim dwParam2 As MCI_OVLY_RECT_PARMS
   
         MMControl1.Command = "Close"
         MMControl1.Filename = "WndSurf1.avi"  'Sample AVI file to be
                                                  'played.
   
         'Get the MCI control to display the video in Picture1:
         MMControl1.hWndDisplay = Picture1.hWnd
   
         MMControl1.Command = "Open"
   
         'Initialize the structure being passed with mciSendCommand, and
         'set it in case you want to use the Notify property:
         dwParam2.dwCallback = MMControl1.hWnd
         dwParam2.rc.Left = 0
         dwParam2.rc.Top = 0
         dwParam2.rc.Right = 0
         dwParam2.rc.Bottom = 0
   
         'Send the message:
         'Enter the following two lines as one, single line of code:
         Retval& = mciSendCommand(MMControl1.DeviceID, MCI_WHERE,
                   MCI_OVLY_WHERE_SOURCE, dwParam2)
   
         If Retval& <> 0 Then  ' An error occurred.
            Buffer$ = Space$(100)
            'Get a description of the error:
            Retval& = mciGetErrorString(Retval&, Buffer$, Len(Buffer$))
            MsgBox Trim$(Buffer$), MB_OK + MB_ICONSTOP, "ERROR"
         Else
            'Resize the picture box:
            Picture1.Width = dwParam2.rc.right - dwParam2.rc.left
            Picture1.Height = dwParam2.rc.bottom - dwParam2.rc.top
   
            'Play the video:
            MMControl1.Wait = True ' Wait for the next command to complete
            MMControl1.Command = "play" 'Play the video clip
            MMControl1.Command = "close"
         End If
      End Sub
    




4. Test the program by pressing the F5 key to run it, and clicking the command button. The AVI file will play back in the picture box, which will have been resized to fit the video clip exactly.

Additional query words: 3.00 4.00 MCI AVI vb4win vb432

Keywords : kbcode kbWndw
Version : 4.00
Platform : WINDOWS
Issue type :