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Copying graphics with BitBlt (.NET Style)

, 29 Dec 2003
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When Graphics.Clone() just won't do.

Introduction

When the basic GDI+ functions just won't do, what you want is back to API school. BitBlt quite simply makes copies of portions of the screen. This is done by accessing the Windows hDC and other low level mind numbing things.

First we most Declare the functions that are in the GDI32.DLL file so we can use them in VB.NET.

Declare Auto Function BitBlt Lib "GDI32.DLL" ( _
     ByVal hdcDest As IntPtr, _
     ByVal nXDest As Integer, _
     ByVal nYDest As Integer, _
     ByVal nWidth As Integer, _
     ByVal nHeight As Integer, _
     ByVal hdcSrc As IntPtr, _
     ByVal nXSrc As Integer, _
     ByVal nYSrc As Integer, _
     ByVal dwRop As Int32) As Boolean

Then I have created a special function that will copy the area of the screen specified by rectangleF.

Private Function copyRect(ByVal src As PictureBox, _ 
       ByVal rect As RectangleF) As Bitmap
     'Get a Graphics Object from the form
     Dim srcPic As Graphics = src.CreateGraphics
     'Create a EMPTY bitmap from that graphics
     Dim srcBmp As New Bitmap(src.Width, src.Height, srcPic)
     'Create a Graphics object in memory from that bitmap
     Dim srcMem As Graphics = Graphics.FromImage(srcBmp)

     'get the IntPtr's of the graphics
     Dim HDC1 As IntPtr = srcPic.GetHdc
     'get the IntPtr's of the graphics
     Dim HDC2 As IntPtr = srcMem.GetHdc

     'get the picture 
     BitBlt(HDC2, 0, 0, rect.Width, _ 
       rect.Height, HDC1, rect.X, rect.Y, 13369376)

     'Clone the bitmap so we can dispose this one 
     copyRect = srcBmp.Clone()

     'Clean Up 
     srcPic.ReleaseHdc(HDC1)
     srcMem.ReleaseHdc(HDC2)
     srcPic.Dispose()
     srcMem.Dispose()
     srcMem.Dispose()
End Function

Then all we need to do is call the function to return the image you want:

Dim bmp = CType(copyRect(src, _ 
    New RectangleF(0, 0, 50, src.Height)), Bitmap)    
dest.Image = bmp.CloneShorthand:

-or-

dest.Image = CType(copyRect(src, _ 
   New RectangleF(0, 0, 50, src.Height)), Bitmap).Clone

Either statement will clone the src image at (0,0,50, src.height) and return a bitmap object. I have simply then taken the bitmap object and cloned it into a picturebox so you can see the results.

License

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About the Author

Matthew Hazlett
Web Developer
United States United States
I started programming for fun when I was about 10 on an Franklin Ace 1000.
 
I still do it just for fun but it has gotten me a few jobs over the years. More then I can say for my Microsoft Certifications. Smile | :)
 
The way I learned was by example, now its time to give back to the next generation of coders.
 


Comments and Discussions

 
GeneralClon BitBlt Vb to .Net (Sub BitBlt2) PinmemberMember 366877515-Aug-08 14:12 
Questioncoloring images in picture box Pinmembersurgunsum13-Nov-07 0:16 
GeneralPrint Screen PinmemberAliBong20-Aug-06 0:06 
GeneralConverting the Code Above for Layered Windows and Cmd Line Arguments [modified] PinmemberMeskibob20-Jul-06 19:01 
Generalcode doesn't work with my version of vb.net Pinmemberserendipity 223-May-06 14:10 
GeneralMore memory problems with this example PinmemberMike.Anderson20-Dec-05 7:47 
GeneralRe: More memory problems with this example PinmemberMatthew Hazlett20-Dec-05 8:53 
GeneralGood work, thanks! PinmemberPinhead7512-May-05 20:59 
Generalcopy invisible images Pinmemberthecopymaster29-Sep-04 4:20 
GeneralRe: copy invisible images Pinmemberbskirkman26-Jan-06 12:37 
GeneralRe: copy invisible images Pinmemberdi~v~inci11-Sep-08 5:03 
GeneralRe: copy invisible images PinmemberWan--Vevi20-Oct-08 17:22 
GeneralImages PinmemberFade (Amit BS)18-Apr-04 13:22 
GeneralRe: Images Pinmemberserendipity 223-May-06 14:14 
AnswerRe: Images- off screen PinmemberFade (Amit BS)9-May-06 22:33 
GeneralRe: Images PinmemberFade (Amit BS)9-May-06 22:38 
GeneralFix for Memory Leak Pinmemberhazlema30-Dec-03 14:42 
GeneralRe: Fix for Memory Leak PineditorHeath Stewart2-Jan-04 9:53 
GeneralBitBlt vs DrawImage PinmemberStan Shannon30-Dec-03 13:45 
GeneralRe: BitBlt vs DrawImage Pinmemberhazlema30-Dec-03 14:43 
Havn't compared them indepth but it's much faster.

GeneralRe: BitBlt vs DrawImage PinsussWeenerpoo16-Jan-04 5:14 
GeneralRe: BitBlt vs DrawImage PinmemberFade (Amit BS)18-Apr-04 13:17 
GeneralRe: BitBlt vs DrawImage Pinmemberyvdh22-Jul-05 14:31 

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