Q129887: Introducing the Powerful New Picture Object in VB 4.0

Article: Q129887
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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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 INFORMATION
================

Array 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
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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.

Additional query words: 4.00 vb4win vb4all

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Keywords          :  
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400 kbVB16bitSearch

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