HOWTO: Use Windows BitBlt Function in Visual Basic Application

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic for Windows, version 4.0

SUMMARY

Windows GDI.EXE has a function called BitBlt that will move the source device given by the hSrcDC parameter to the destination device given by the hDestDC parameter. This article explains in detail the arguments of the Windows BitBlt function call.

MORE INFORMATION

To use BitBlt within a Visual Basic application:

Use the following Declare statement to declare the Function in 16-bit Visual Basic. (If the declaration is placed in the General Declarations section of a Form, the keyword Private must be placed at the beginning of the declaration.)

Declare Function BitBlt Lib "GDI" (ByVal hDestDC%, ByVal X%, ByVal Y%, _

If you are using the 32-bit version of Visual Basic use the following Declare statement. (If the declaration is placed in the General Declarations section of a Form, the keyword Private must be placed at the beginning of the declaration.)

Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As _

The following defines each of the formal parameters used in the Declare:

Parameter   Definition

hDestDC     Specifies the device context that is to receive the bitmap.
X,Y         Specifies the logical x-coordinate and y-coordinate of the
            upper-left corner of the destination rectangle.

nWidth   Specifies the width (in logical units) of the destination
         rectangle and the source bitmap.

         rectangle and the source bitmap.

hSrcDC   Identifies the device context from which the bitmap will be
         copied. It must be NULL(zero) if the dwRop& parameter specifies a
         raster operation that does not include a source.

      left corner of the source bitmap.

The following Raster operations are defined using the predefined constants found in the WINDOWS.H file supplied with the Microsoft Windows Software Development Kit (SDK). The value in the parentheses () is the value to assign to the dwRop& variable.

Code/Value (hex)     Description

BLACKNESS (42)       Turn output black.
DSINVERT(550009)     Inverts the destination bitmap.
MERGECOPY(C000CA)    Combines the pattern and the source bitmap using the
                     Boolean AND operation.
MERGEPAINT(BB0226)   Combines the inverted source bitmap with the
                     destination bitmap using the Boolean OR operator.
NOTSRCCOPY(330008)   Copies the inverted source bitmap to the destination.

                     source bitmap using the Boolean OR operator.
PATCOPY(F00021)      Copies the pattern to the destination bitmap.
PATINVERT(5A0049)    Combines the destination bitmap with the pattern using
                     the Boolean XOR operator.
PATPAINT(FB0A09)     Combines the inverted source bitmap with the pattern
                     using the Boolean OR operator. Combines the result of
                     this operation with the destination bitmap using the
                     Boolean OR operator.
SRCAND(8800C6)       Combines pixels of the destination and source bitmap
                     using the Boolean AND operator.
SRCCOPY(CC0020)      Copies the source bitmap to destination bitmap.
SRCERASE(4400328)    Inverts the destination bitmap and combines the
                     results with the source bitmap using the Boolean AND
                     operator.
SRCINVERT(660046)    Combines pixels of the destination and source bitmap
                     using the Boolean XOR operator.
SRCPAINT(EE0086)     Combines pixels of the destination and source bitmap
                     using the Boolean OR operator.
WHITENESS(FF0062)    Turns all output white.

Step-by-Step Example

Here is an example showing how to copy the contents of a picture control to the contents of another picture control.

1. Define a form (Form1) and place two picture controls (Picture1 and Picture2) on Form1.

2. Select the Visual Basic Insert menu to add a new code module to your project with the default name of module1.bas.

3. In the General Declarations section of the module place the following code to declare the BitBlt API.

         #If Win32 Then
         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
         #Else
         Declare Function BitBlt Lib "GDI" (ByVal hDestDC%, ByVal X%, ByVal _
         Y%, ByVal nWidth%, ByVal nHeight%, ByVal hSrcDC%, ByVal XSrc%, _
         ByVal YSrc%, ByVal dwRop&) As Integer
         #End If
   

4. Display some graphics on Picture1 by loading from a picture file or by pasting from the clipboard at design time. You can load a picture from a file as follows:

   - Select Picture from the Properties list box and click the button with

        three dots to the right of the Settings box.
   

   - Then select the desired picture file such as a .BMP or .ICO file

        supplied with Microsoft Windows from the dialog box.
   

5. Add the following code to the Form_Click procedure:

         Private Sub Form_Click ()
         #If Win32 Then
         Const PIXEL = 3
         Picture1.ScaleMode = PIXEL
         Picture2.ScaleMode = PIXEL
         hDestDC& = Picture2.hDC
         x& = 0: y& = 0
         nWidth& = Picture2.ScaleWidth
         nHeight& = Picture2.ScaleHeight
         ' Assign information of the source bitmap.
         hSrcDC& = Picture1.hDC
         xSrc& = 0: ySrc& = 0
         ' Assign the SRCCOPY constant to the Raster operation.
         dwRop& = &HCC0020
         Suc& = BitBlt(hDestDC&, x&, y&, nWidth&, nHeight&, hSrcDC&, _
         xSrc&, ySrc&, dwRop&)
         #Else
         ' Assign information of the destination bitmap. Note that Bitblt
         ' requires coordinates in pixels.
         Const PIXEL = 3
         Picture1.ScaleMode = PIXEL
         Picture2.ScaleMode = PIXEL
         hDestDC% = Picture2.hDC
         x% = 0: y% = 0
         nWidth% = Picture2.ScaleWidth
         nHeight% = Picture2.ScaleHeight
         ' Assign information of the source bitmap.
         hSrcDC% = Picture1.hDC
         xSrc% = 0: ySrc% = 0
         ' Assign the SRCCOPY constant to the Raster operation.
         dwRop& = &HCC0020
         Suc% = BitBlt(hDestDC%, x%, y%, nWidth%, nHeight%, hSrcDC%, _
         xSrc%, ySrc%, dwRop&)
         #End If
         End Sub
   

6. Run the program. Click the form. The contents of the first picture will be displayed on the se cond picture.

Keywords          : APrgGrap vb416 VB4WIN kbgraphic kbfasttip
Version           : 4.0
Platform          : WINDOWS
Issue type        : kbhowto