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Capture screenshot of active window?


Question

I am making a screen capturing application and everything is going fine. All I need to do is capture the active window and take a screenshot of this active window. Does anyone know how I can do this?

2014/04/11
1
176
4/11/2014 4:43:02 PM

Accepted Answer

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);

http://www.developerfusion.com/code/4630/capture-a-screen-shot/

2009/07/22
153
7/22/2009 8:59:22 AM


I suggest next solution for capturing any current active window (not only our C# application) or entire screen with cursor position determination relative to left-top corner of window or screen respectively:

public enum enmScreenCaptureMode
{
    Screen,
    Window
}

class ScreenCapturer
{
    [DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll")]
    private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rect rect);

    [StructLayout(LayoutKind.Sequential)]
    private struct Rect
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }

    public Bitmap Capture(enmScreenCaptureMode screenCaptureMode = enmScreenCaptureMode.Window)
    {
        Rectangle bounds;

        if (screenCaptureMode == enmScreenCaptureMode.Screen)
        {
            bounds = Screen.GetBounds(Point.Empty);
            CursorPosition = Cursor.Position;
        }
        else
        {
            var foregroundWindowsHandle = GetForegroundWindow();
            var rect = new Rect();
            GetWindowRect(foregroundWindowsHandle, ref rect);
            bounds = new Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top);
            CursorPosition = new Point(Cursor.Position.X - rect.Left, Cursor.Position.Y - rect.Top);
        }

        var result = new Bitmap(bounds.Width, bounds.Height);

        using (var g = Graphics.FromImage(result))
        {
            g.CopyFromScreen(new Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size);
        }

        return result;
    }

    public Point CursorPosition
    {
        get;
        protected set;
    }
}
2012/01/31

Here is a snippet to capture either the desktop or the active window. It has no reference to Windows Forms.

public class ScreenCapture
{
    [DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
    public static extern IntPtr GetDesktopWindow();

    [StructLayout(LayoutKind.Sequential)]
    private struct Rect
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }   

    [DllImport("user32.dll")]
    private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rect rect);

    public static Image CaptureDesktop()
    {
        return CaptureWindow(GetDesktopWindow());
    }

    public static Bitmap CaptureActiveWindow()
    {
        return CaptureWindow(GetForegroundWindow());
    }

    public static Bitmap CaptureWindow(IntPtr handle)
    {
        var rect = new Rect();
        GetWindowRect(handle, ref rect);
        var bounds = new Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top);
        var result = new Bitmap(bounds.Width, bounds.Height);

        using (var graphics = Graphics.FromImage(result))
        {
            graphics.CopyFromScreen(new Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size);
        }

        return result;
    }
}

How to capture the whole screen:

var image = ScreenCapture.CaptureDesktop();
image.Save(@"C:\temp\snippetsource.jpg", ImageFormat.Jpeg);

How to capture the active window:

var image = ScreenCapture.CaptureActiveWindow();
image.Save(@"C:\temp\snippetsource.jpg", ImageFormat.Jpeg);

Originally found here: http://www.snippetsource.net/Snippet/158/capture-screenshot-in-c

2019/05/02

KvanTTT's code worked great. I extended it a bit to allow a little more flexibility on save format, as well as the ability to save by hWnd, .NET Control/Form. You can get a bitmap or save to file, with a few options.

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace MosaiqPerformanceMonitor {
     public enum CaptureMode {
          Screen, Window
     }

     public static class ScreenCapturer {
          [DllImport("user32.dll")]
          private static extern IntPtr GetForegroundWindow();

          [DllImport("user32.dll")]
          private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rect rect);

          [StructLayout(LayoutKind.Sequential)]
          private struct Rect {
                public int Left;
                public int Top;
                public int Right;
                public int Bottom;
          }

          [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
          public static extern IntPtr GetDesktopWindow();

          /// <summary> Capture Active Window, Desktop, Window or Control by hWnd or .NET Contro/Form and save it to a specified file.  </summary>
          /// <param name="filename">Filename.
          /// <para>* If extension is omitted, it's calculated from the type of file</para>
          /// <para>* If path is omitted, defaults to %TEMP%</para>
          /// <para>* Use %NOW% to put a timestamp in the filename</para></param>
          /// <param name="mode">Optional. The default value is CaptureMode.Window.</param>
          /// <param name="format">Optional file save mode.  Default is PNG</param>
          public static void CaptureAndSave(string filename, CaptureMode mode = CaptureMode.Window, ImageFormat format = null) {
                ImageSave(filename, format, Capture(mode));
          }

          /// <summary> Capture a specific window (or control) and save it to a specified file.  </summary>
          /// <param name="filename">Filename.
          /// <para>* If extension is omitted, it's calculated from the type of file</para>
          /// <para>* If path is omitted, defaults to %TEMP%</para>
          /// <para>* Use %NOW% to put a timestamp in the filename</para></param>
          /// <param name="handle">hWnd (handle) of the window to capture</param>
          /// <param name="format">Optional file save mode.  Default is PNG</param>
          public static void CaptureAndSave(string filename, IntPtr handle, ImageFormat format = null) {
                ImageSave(filename, format, Capture(handle));
          }

          /// <summary> Capture a specific window (or control) and save it to a specified file.  </summary>
          /// <param name="filename">Filename.
          /// <para>* If extension is omitted, it's calculated from the type of file</para>
          /// <para>* If path is omitted, defaults to %TEMP%</para>
          /// <para>* Use %NOW% to put a timestamp in the filename</para></param>
          /// <param name="c">Object to capture</param>
          /// <param name="format">Optional file save mode.  Default is PNG</param>
          public static void CaptureAndSave(string filename, Control c, ImageFormat format = null) {
                ImageSave(filename, format, Capture(c));
          }
          /// <summary> Capture the active window (default) or the desktop and return it as a bitmap </summary>
          /// <param name="mode">Optional. The default value is CaptureMode.Window.</param>
          public static Bitmap Capture(CaptureMode mode = CaptureMode.Window) {
                return Capture(mode == CaptureMode.Screen ? GetDesktopWindow() : GetForegroundWindow());
          }

          /// <summary> Capture a .NET Control, Form, UserControl, etc. </summary>
          /// <param name="c">Object to capture</param>
          /// <returns> Bitmap of control's area </returns>
          public static Bitmap Capture(Control c) {
                return Capture(c.Handle);
          }


          /// <summary> Capture a specific window and return it as a bitmap </summary>
          /// <param name="handle">hWnd (handle) of the window to capture</param>
          public static Bitmap Capture(IntPtr handle) {
                Rectangle bounds;
                var rect = new Rect();
                GetWindowRect(handle, ref rect);
                bounds = new Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top);
                CursorPosition = new Point(Cursor.Position.X - rect.Left, Cursor.Position.Y - rect.Top);

                var result = new Bitmap(bounds.Width, bounds.Height);
                using (var g = Graphics.FromImage(result))
                     g.CopyFromScreen(new Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size);

                return result;
          }

          /// <summary> Position of the cursor relative to the start of the capture </summary>
          public static Point CursorPosition;


          /// <summary> Save an image to a specific file </summary>
          /// <param name="filename">Filename.
          /// <para>* If extension is omitted, it's calculated from the type of file</para>
          /// <para>* If path is omitted, defaults to %TEMP%</para>
          /// <para>* Use %NOW% to put a timestamp in the filename</para></param>
          /// <param name="format">Optional file save mode.  Default is PNG</param>
          /// <param name="image">Image to save.  Usually a BitMap, but can be any
          /// Image.</param>
          static void ImageSave(string filename, ImageFormat format, Image image) {
                format = format ?? ImageFormat.Png;
                if (!filename.Contains("."))
                     filename = filename.Trim() + "." + format.ToString().ToLower();

                if (!filename.Contains(@"\"))
                     filename = Path.Combine(Environment.GetEnvironmentVariable("TEMP") ?? @"C:\Temp", filename);

                filename = filename.Replace("%NOW%", DateTime.Now.ToString("[email protected]"));
                image.Save(filename, format);
          }
     }
}
2012/08/14

I assume you use Graphics.CopyFromScreen to get the screenshot.

You can use P/Invoke to GetForegroundWindow (and then get its position and size) to determine which region you need to copy from.

2011/07/31

You can use the code from this question: How can I save a screenshot directly to a file in Windows?

Just change WIN32_API.GetDesktopWindow() to the Handle property of the window you want to capture.

2017/05/23

Source: https://stackoverflow.com/questions/1163761
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