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Capture a Screen Shot
This code demonstrates how to get a screen shot of the entire desktop, or a particular window, using .NET (and a few API functions). The C# version is shown here, but the download includes a VB.NET version too.
Using the class is simple - there are four methods
-
public Image CaptureScreen()
Creates an Image object containing a screen shot of the entire desktop
-
public Image CaptureWindow(IntPtr handle)
Creates an Image object containing a screen shot of a specific window
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public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
Captures a screen shot of a specific window, and saves it to a file
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public void CaptureScreenToFile(string filename, ImageFormat format)
Captures a screen shot of the entire desktop, and saves it to a file
A quick demonstration of how to use it...
ScreenCapture sc = new ScreenCapture();
// capture entire screen, and save it to a file
Image img = sc.CaptureScreen();
// display image in a Picture control named imageDisplay
this.imageDisplay.Image = img;
// capture this window, and save it
sc.CaptureWindowToFile(this.Handle,"C:\\temp2.gif",ImageFormat.Gif);
And here's the code to the class we're using
using System;
using System.Runtime.InteropServices;
using System.Drawing;
using System.Drawing.Imaging;
namespace ScreenShotDemo
{
/// <summary>
/// Provides functions to capture the entire screen, or a particular window, and save it to a file.
/// </summary>
public class ScreenCapture
{
/// <summary>
/// Creates an Image object containing a screen shot of the entire desktop
/// </summary>
/// <returns></returns>
public Image CaptureScreen()
{
return CaptureWindow( User32.GetDesktopWindow() );
}
/// <summary>
/// Creates an Image object containing a screen shot of a specific window
/// </summary>
/// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
/// <returns></returns>
public Image CaptureWindow(IntPtr handle)
{
// get te hDC of the target window
IntPtr hdcSrc = User32.GetWindowDC(handle);
// get the size
User32.RECT windowRect = new User32.RECT();
User32.GetWindowRect(handle,ref windowRect);
int width = windowRect.right - windowRect.left;
int height = windowRect.bottom - windowRect.top;
// create a device context we can copy to
IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
// create a bitmap we can copy it to,
// using GetDeviceCaps to get the width/height
IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc,width,height);
// select the bitmap object
IntPtr hOld = GDI32.SelectObject(hdcDest,hBitmap);
// bitblt over
GDI32.BitBlt(hdcDest,0,0,width,height,hdcSrc,0,0,GDI32.SRCCOPY);
// restore selection
GDI32.SelectObject(hdcDest,hOld);
// clean up
GDI32.DeleteDC(hdcDest);
User32.ReleaseDC(handle,hdcSrc);
// get a .NET image object for it
Image img = Image.FromHbitmap(hBitmap);
// free up the Bitmap object
GDI32.DeleteObject(hBitmap);
return img;
}
/// <summary>
/// Captures a screen shot of a specific window, and saves it to a file
/// </summary>
/// <param name="handle"></param>
/// <param name="filename"></param>
/// <param name="format"></param>
public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
{
Image img = CaptureWindow(handle);
img.Save(filename,format);
}
/// <summary>
/// Captures a screen shot of the entire desktop, and saves it to a file
/// </summary>
/// <param name="filename"></param>
/// <param name="format"></param>
public void CaptureScreenToFile(string filename, ImageFormat format)
{
Image img = CaptureScreen();
img.Save(filename,format);
}
/// <summary>
/// Helper class containing Gdi32 API functions
/// </summary>
private class GDI32
{
public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
[DllImport("gdi32.dll")]
public static extern bool BitBlt(IntPtr hObject,int nXDest,int nYDest,
int nWidth,int nHeight,IntPtr hObjectSource,
int nXSrc,int nYSrc,int dwRop);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC,int nWidth,
int nHeight);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
[DllImport("gdi32.dll")]
public static extern bool DeleteDC(IntPtr hDC);
[DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
[DllImport("gdi32.dll")]
public static extern IntPtr SelectObject(IntPtr hDC,IntPtr hObject);
}
/// <summary>
/// Helper class containing User32 API functions
/// </summary>
private class User32
{
[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
public int left;
public int top;
public int right;
public int bottom;
}
[DllImport("user32.dll")]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll")]
public static extern IntPtr GetWindowDC(IntPtr hWnd);
[DllImport("user32.dll")]
public static extern IntPtr ReleaseDC(IntPtr hWnd,IntPtr hDC);
[DllImport("user32.dll")]
public static extern IntPtr GetWindowRect(IntPtr hWnd,ref RECT rect);
}
}
}
James first started writing tutorials on Visual Basic in 1999 whilst starting this website (then known as VB Web). Since then, the site has grown rapidly, and James has written numerous tutorials, articles and reviews on VB, PHP, ASP and C#. In October 2003, James formed the company Developer Fusion Ltd, which owns this website, and also offers various development services. In his spare time, he's a 3rd year undergraduate studying Computer Science in the UK. He's also a Visual Basic MVP.
Comments
-
I have not tried it yet..but lets see..it -
Posted by Barzille on 01 Aug 2007
I've got a problem with screenshots of direct3d windows. After taking a first shot everything is fine. The second and all following shots are not updated correctly. Instead they always show the fir... -
Posted by pcmattman on 20 Dec 2006
Make sure that you are using SRCCOPY! Also make sure that all the code is exactly the same as it appears here. I tried this code out in C++ and it DID NOT WORK at first. A little investigation show... -
Posted by DanielSmith on 20 Dec 2006
i had the same problem too,but i just tried aca and solved thr problem, here is the details. i hope it helps.
http://screen-capture.spaces.live.com/blog/cns!543BF253C6896A68!133.entry
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Posted by pcmattman on 12 Dec 2006
I'm not sure what the problem is. I'll be able to be progamming again next week so I'll look into it.
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