* VB-CODE (4)
Tip 98: Saving a Window's Client Area in Bitmap Format

May 29, 1995

You may need to create a bitmap (.BMP) image file that contains a
window's client area. This article explains how to save a window's
client area to disk in a bitmap image file format.

Saving Bitmap Images to Disk
You can save the contents of a window to a disk file in bitmap format
by retrieving the target window's rectangle area and then using
several Windows® application programming interface (API) functions to
save that image to a device context such as a Picture Box control.

The GetWindowRect function can be used to retrieve the bounding
rectangle of a window or form. This rectangle includes the window's
borders, title bars, and other attributes associated with a window.
The Declare statement for the GetWindowRect function is as follows:

Private Declare Sub GetWindowRect Lib "User" (ByVal hWnd As Integer, lpRect
  As RECT)

The GetWindowRect function takes two arguments: an integer value
containing the window's handle and a pointer to a RECT rectangle
structure. The RECT structure will contain the dimensions of the
window's rectangle area after the function is called.

The BitBlt function uses the rectangle that contains the image you
want to save to disk to copy the image from one device context to
another. In this case, BitBlt is used to copy the window's client
area to the Picture Box control. Then the Save As dialog box is used
to save the contents of the Picture Box to disk as a .BMP file.

Example Program
This program shows how to save the client area of a form or window
and save it as a .BMP file.

 1. Create a new project in Visual Basic®. Form1 is created by default.
 2. Add the following Constant and Declare statements to the General
    Declarations section of Form1 (note that each Declare statement
    must be typed as a single line of code):

Private Declare Function GetActiveWindow Lib "User" () As Integer
Private Declare Function GetWindowDC Lib "User" (ByVal hWnd As Integer)
   As Integer
Private Declare Sub GetWindowRect Lib "User" (ByVal hWnd As Integer, lpRect
   As RECT)
Private Declare Function ReleaseDC Lib "User" (ByVal hWnd As Integer, ByVal hDC
   As Integer) As Integer
Private Declare Function BitBlt% Lib "GDI" (ByVal hDestDC%, ByVal X%, ByVal Y%,
   ByVal nWidth%, ByVal nHeight%, ByVal hSrcDC%, ByVal XSrc%, ByVal YSrc%, ByVal
Const SRCCOPY = &HCC0020

 3. From the Insert menu, select Form to create a second form. Form2
    is created by default. Set its Picture property to
 4. From the Insert menu, select Module to create a BASIC module.
    Module1.Bas is created by default.
 5. Add the following Type structure to Module1.Bas:

    Left As Integer
    Top As Integer
    Right As Integer
    Bottom As Integer
End Type

 6. Add a Timer control to Form1. Timer1 is created by default.
 7. Add a Picture Box control to Form1. Picture1 is created by
    default. Set its AutoRedraw property to True.
 8. Add a Command Button control to Form1. Command1 is created by
 9. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
End Sub

10. Create a new function called SaveToPicture. Add the following code
   to this function:

Sub SaveToPicture()
    Dim hDCCur As Long
    Dim hWndCur As Long
    Dim HWndOld As Long
    Dim Tim As Double
    Dim ThisRect As RECT
    Dim DX As Long
    Dim DY As Long

    HWndOld = GetActiveWindow()
    hWndCur = Form2.hWnd
    Tim = Timer + 0.5
    Loop Until Timer >= Tim

    hDCCur = GetWindowDC(hWndCur)
    Call GetWindowRect(hWndCur, ThisRect)
    DX = ThisRect.Right - ThisRect.Left + 2: DY = ThisRect.Bottom - ThisRect.Top + 2

    With Picture1
        .Width = Screen.TwipsPerPixelX * DX
        .Height = Screen.TwipsPerPixelY * DY
        Call BitBlt(.hDC, 0, 0, DX, DY, hDCCur, 0, 0, SRCCOPY)
        .Picture = .Image
    End With

    Call ReleaseDC(hWndCur, hDCCur)

    CommonDialog1.DefaultExt = "BMP"
    CommonDialog1.DialogTitle = "Save Window As"
    CommonDialog1.FileName = "*.BMP"
    CommonDialog1.Action = 2

    If CommonDialog1.FileName <> Empty Then
        SavePicture Picture1.Picture, CommonDialog1.FileName
    End If
End Sub

11. Add a Common Dialog control to Form1. CommonDialog1 is created by

Run this program by pressing the F5 function key. Click once on the
command button. The ARCHES.BMP picture is displayed on Form2. Next,
the Save File As dialog box pops up on the screen. Type a filename
for the .BMP file and Visual Basic will save Form2's window (which
contains the ARCHES.BMP picture) to a new bitmap file.

Additional References
"Bitmaps." (Product Documentation, DDKs, Windows 3.1 DDK, Device
   Driver Adaptation Guide)
"GetActiveWindow"; "GetWindowDC"; and "ReleaseDC." (Product
   Documentation, SDKs, Windows 3.1 SDK, Programmer's Reference
   Volume 2: Functions)
Knowledge Base Q71104. "How to Use Windows BitBlt Function in Visual
   Basic Application."