How to Use Windows BitBlt Function From Visual Basic

See AlsoVMZ7S4

This article is reprinted from the Microsoft Knowledge Base.  To view the article, maximize your help window.  This information applies to Visual Basic for Windows, versions 2.0 and 3.0.

Summary:

Windows GDI.EXE has a function called BitBlt, which 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, you must Declare the

BitBlt function in  the (declaration) section of any code module or within the (declaration) section of a code

window for the form.  Declare the Function as follows:

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

Note: The above Declare statement must be written on just one line.

The following formal parameters are defined as:

   Formal 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.

   nHeight Specifies the height (in logical units) of

     the destination 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.

   XSrc    Specifies the logical x-coordinate and the

     y-coordinate of the upper-left corner of the

     source bitmap.

  dwRop    Specifies the raster operation to be performed

     as defined below.

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

within the "()" 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.

   NOTSRCERASE(1100A6) Inverts the result of combining the

     destination and 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 the 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.

Below is an example of how to copy the contents of a picture control

to the contents of another picture control.

Define a form with two picture controls. Display some graphics on

Picture1 by loading from a picture file or pasting from the clipboard

at design time. You can load a picture from a file as follows: from

the Properties bar, select Picture from the Properties list box and

click the arrow at 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.

Add the following code to the Form_Click procedure. Run the program

and click the form. The contents of the first picture will be displayed to

the second picture.

Sub Form_Click ()

   ' 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 Sub