Introducing the Powerful New Picture Object in VB 4.0 (129887)
The information in this article applies to:
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows 4.0
This article was previously published under Q129887 SUMMARY
In Visual Basic version 3.0, you had only the Picture property of the
PictureBox control. Now, in Visual Basic version 4.0, you have a new
Picture object that adds many capabilities. This article details some of
these new capabilities.
MORE INFORMATIONArray of Picture Objects
You can use an array of Picture objects to keep a series of graphics in
memory without using a form that contains multiple PictureBox or Image
controls. For example, the following code loads a Picture object with a
bitmap and uses that bitmap to set the Picture property of a PictureBox
control:
Private Sub Command1_Click()
Dim x As Picture
Set x = LoadPicture("cars")
Set Picture1.Picture = x
End Sub
Handle Property of Picture Object Differs from hDC Property of PictureBox
There is no direct relationship between a Picture.Handle and a
PictureBox.hDC. The hDC property of the PictureBox is the handle provided
by the operating system to the device context of the PictureBox control.
The Handle property of the Picture object is actually the handle of the GDI
object that is contained in the Picture object. If the Picture property
contains a bitmap, its an HBITMAP. If it contains an icon, then its an
HICON, or if it contains a metafile, then its an HMETAFILE.
Use the Picture Object Instead of the Windows API
There are lots of things you can do with an HBITMAP, an HICON, or an
HMETAFILE in the Windows API, but the Picture object already does most of
them for you. This means that you are better off using the Picture object
instead of the Windows API whenever possible.
There are now two completely different ways to paint graphics on a window
(or blit). You can use BitBlt or StretchBlt on the hDC of an object, or you
can use the PaintPicture method on the Picture Object or Property. If you
have an Image control, you can only use PaintPicture because Image controls
do not have an hDC. For example:
Private Sub Command1_Click()
Dim x as Picture
Set x = LoadPicture("cars.bmp")
PaintPicture x, 0, 0
PaintPicture Picture1.Picture, 0, 200
PaintPicture Image1.Picture, 0, 500
End Sub
The link between the Picture object and the PictureBox control is the Image
property. You can draw something into the hDC of the PictureBox (with
BitBlt, Polygon, LineTo, or other API functions), and then assign its Image
property to the Picture property. This gives the PictureBox a bitmap with
the same content as the hDC. This is useful for operations such as
converting an icon or a metafile into a bitmap. However, you can only use
raster operation (ROP) codes with PaintPicture on bitmaps, so this
conversion is necessary for many blitting operations.
NOTE: For a list of Raster Operation (ROP) codes for use with PaintPicture,
see WIN32API.TXT in your VB\WINAPI directory.
Modification Type: | Major | Last Reviewed: | 12/9/2003 |
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Keywords: | KB129887 |
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