Library code snippets
Capture a Screen Shot
By James Crowley, published on 13 Apr 2004
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 -
public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)Captures a screen shot of a specific window, and saves it to a file -
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 this website when learning Visual Basic back in 1999 whilst studying his GCSEs. The site grew steadily over the years while being run as a hobby - to a regular monthly audience ...
Related articles
Related discussion
-
Creating a Windows Service in VB.NET
by Templario55 (107 replies)
-
About User Control in .Net
by andypat (4 replies)
-
High-Performance .NET Application Development & Architecture
by Manjot Bawa (0 replies)
-
How can i send data from VB.Net to Dymo Labels
by himanshu.tomar (0 replies)
-
popup window in vb.net... how it's work?..
by yf2009 (6 replies)
Related podcasts
-
More jQuery in ASP.NET
In this episode Chris Brandsma, Rick Strahl, Dave Ward, Bertrand Le Roy, and Scott Koon conclude their discussion of Microsoft's jQuery in ASP.NET announcement1.This episode of the Alt.NET Podcast is brought to you by LLBLGen Pro, the most mature O/R mapper and code generator out there.Are ...
Events coming up
-
Nov
18
15 Minutes of Fame
Dresher, United States
This is a yearly tradition. We select 10 of the favorite speakers from monthly meetings, code camps, and hands on labs. Each one does a 15 minute talk on their favorite .NET technology. This is our 10th anniversary so we plan a gala event with special prizes and refreshments.
Comments
Leave a comment
Sign in or Join us (it's free).