Visual Basic Window/Form Routines
GetSystemMetrics: Resizing a Form to Fit an Image
     
Posted:   Friday January 03, 2003
Updated:   Monday December 26, 2011
     
Applies to:   VB4-32, VB5, VB6
Developed with:   VB6, Windows XP; Updated with VB6, Vista
OS restrictions:   None
Author:   VBnet - Randy Birch
     
 Prerequisites
None.

This routine was posted in response to a newsgroup request for a method to resize a child window precisely to the size of a randomly loaded image.  In response to a comment about it not resizing perfectly due to 'magic numbers' I had used in the original resizing routine, I have updated the code to work without any such hard-coded values and thus resize the form irrespective of image loaded.

The demo uses one form to obtain the filename of the image to load via a common dialog, then loads the selected file into a picture box on a second form, invoking that form's AutoSizeToPicture routine via the picture box Change event.  The image-form has a dummy menu shown, to demonstrate the code works with or without a menu present.

GetSystemMetrics retrieves the sizes of various windows bits and pieces, calculating the required size to tightly fit the form around the loaded image.  Note that in order to display small images, its is necessary to remove the Control menu of the image-display form; the form can't resize smaller than the width of the control menu plus the form min/max/close buttons displayed. Note too the comments in AutoSizeToPicture related to the existence of a hidden menu on the image form.

Form 1 - the main form - needs only a command button and a common dialog control.

Form 2 - the picture form - only requires a borderless picture box.

 BAS Module Code
None.

 Form1 Code - Common Dialog Form
Add a common dialog control and a command button to a form, along with the following code:

Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright 1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Sub Form_Load()

   Command1.Caption = "Load Image..."

End Sub


Private Sub Form_Unload(Cancel As Integer)

   Unload Form2

End Sub


Private Sub Command1_Click()

   With CommonDialog1

      .Filter = "Image files (gif, jpg, bmp)|*.gif;*.jpg;*.bmp|"
      .FilterIndex = 0
      .InitDir = "e:\"  'change as required
      .ShowOpen
      
      If Len(.FileName) > 0 Then
      
         Load Form2
         Form2.Picture1.Picture = LoadPicture(.FileName)
         Form2.Caption = .FileName
         Form2.Show

      End If

   End With

End Sub
 Form Code
Add a single image control to the form. The load event sets it up for use.

Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright 1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Declare Function GetSystemMetrics Lib "user32" _
   (ByVal nIndex As Long) As Long

Private Declare Function GetMenu Lib "user32" _
   (ByVal hwnd As Long) As Long

Private Const SM_CYCAPTION = 4
Private Const SM_CYMENU = 15
Private Const SM_CXFRAME = 32
Private Const SM_CYFRAME = 33

Private twipsx As Long
Private twipsy As Long

 
Private Sub Form_Load()

   twipsx = Screen.TwipsPerPixelX
   twipsy = Screen.TwipsPerPixelY
   
   With Picture1
      .AutoSize = True
      .Appearance = 0
      .Appearance = 0
      .BackColor = &HFFFF80
      .BorderStyle = 0
   End With
   
End Sub


Private Sub Picture1_Change()

   Picture1.AutoSize = True
   Call AutoSizeToPicture(Picture1)

End Sub


Private Sub AutoSizeToPicture(pbox As PictureBox)

   Dim vOffset As Long
   Dim hOffset As Long
                     
   hOffset = (GetSystemMetrics(SM_CXFRAME) * 2) * twipsx
   vOffset = (GetSystemMetrics(SM_CYCAPTION) + (GetSystemMetrics(SM_CXFRAME)) * 2) * twipsx
                        
  'if the form also has a menu,
  'account for that too.
  '
  'NOTE: If you are just hiding the menu, then
  'GetMenu(Me.hwnd) will return non-zero even
  'if the menu is hidden, causing an incorrect
  'vertical offset to be used.  Either delete
  'the menu using the menu editor, or if you
  'must have the ability to show/hide a menu
  'on the picture form, you will need to code
  'to also test for me.mnuX.visible then...
  '
  'You can determine whether the correct sizing
  'is taking place by viewing the values returned
  'to the immediate window from the debug.print
  'code below; the values for the form and
  'picture should be the same, e.g.
  ' picture        3450          2385
  ' form           3450          2385

   If GetMenu(Me.hwnd) <> 0 Then
      vOffset = vOffset + (GetSystemMetrics(SM_CYMENU) * twipsy)
   End If

  'position the picture box and resize the form
   With pbox
      .Left = 0
      .Top = 0
      
      Me.Width = .Width + hOffset
      Me.Height = .Height + vOffset
   End With
   
  'these values should be the same
  'if the calculations worked
   Debug.Print "picture", Picture1.Width, Picture1.Height
   Debug.Print "form", Form2.ScaleWidth, Form2.ScaleHeight

End Sub
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