How to Use Windows 3.0 BitBlt Function from Visual Basic

ID Number: Q71104

1.00

WINDOWS

Summary:

The Windows GDI.DLL has a function call 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.

This information applies to Microsoft Visual Basic Programming System

version 1.0 for Windows.

More Information:

To use BitBlt within a Visual Basic application, you must Declare

the BitBlt function in either the Global section or within the

(declaration) section of your code window. 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 version 3.0 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

References:

1. "Programming Windows: the Microsoft Guide to Writing Applications

for Windows 3," by Charles Petzold (published by Microsoft

Press, 1990)

2. "Microsoft Windows 3.0 Software Development Kit: Reference

Volume 1"

3. The WINSDK.HLP file shipped with Microsoft Windows 3.0 Software

Development Kit.

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