Is there a way to take a screenshot of the user's Windows desktop?

Question

I want to provide the user with a scaled-down screenshot of their desktop in my application.

Is there a way to take a screenshot of the current user's Windows desktop?

I'm writing in C#, but if there's a better solution in another language, I'm open to it.

To clarify, I need a screenshot of the Windows Desktop - that's the wallpaper and icons only; no applications or anything that's got focus.

Answer 1

You're looking for Graphics.CopyFromScreen. Create a new Bitmap of the right size and pass the Bitmap's Graphics object screen coordinates of the region to copy.

There's also an article describing how to programmatically take snapshots.

Response to edit: I misunderstood what you meant by "desktop". If you want to take a picture of the desktop, you'll have to:

1. Minimize all windows using the Win32API (send a MIN_ALL message) first
2. Take the snapshot
3. Then undo the minimize all (send a MIN_ALL_UNDO message).

---

A better way to do this would be not to disturb the other windows, but to copy the image directly from the desktop window. GetDesktopWindow in User32 will return a handle to the desktop. Once you have the window handle, get it's device context and copy the image to a new Bitmap.

There's an excellent example on CodeProject of how to copy the image from it. Look for the sample code about getting and creating the device context in the "Capturing the window content" section.

Answer 2

I get the impression that you are shooting for taking a picture of the actual desktop (with wallpaper and icons), and nothing else.

1) Call ToggleDesktop() in Shell32 using COM
2) Use Graphics.CopyFromScreen to copy the current desktop area
3) Call ToggleDesktop() to restore previous desktop state

Edit: Yes, calling MinimizeAll() is belligerent.

Here's an updated version that I whipped together:

    /// <summary>
    /// Minimizes all running applications and captures desktop as image
    /// Note: Requires reference to "Microsoft Shell Controls and Automation"
    /// </summary>
    /// <returns>Image of desktop</returns>
    private Image CaptureDesktopImage() {

        //May want to play around with the delay.
        TimeSpan ToggleDesktopDelay = new TimeSpan(0, 0, 0, 0, 150);

        Shell32.ShellClass ShellReference = null;

        Bitmap WorkingImage = null;
        Graphics WorkingGraphics = null;
        Rectangle TargetArea = Screen.PrimaryScreen.WorkingArea;
        Image ReturnImage = null;

        try
        {

            ShellReference = new Shell32.ShellClass();
            ShellReference.ToggleDesktop();

            System.Threading.Thread.Sleep(ToggleDesktopDelay);

            WorkingImage = new Bitmap(TargetArea.Width,
                TargetArea.Height);

            WorkingGraphics = Graphics.FromImage(WorkingImage);
            WorkingGraphics.CopyFromScreen(TargetArea.X, TargetArea.X, 0, 0, TargetArea.Size);

            System.Threading.Thread.Sleep(ToggleDesktopDelay);
            ShellReference.ToggleDesktop();

            ReturnImage = (Image)WorkingImage.Clone();

        }
        catch
        {
            System.Diagnostics.Debugger.Break();
            //...
        }
        finally
        {
            WorkingGraphics.Dispose();
            WorkingImage.Dispose();
        }

        return ReturnImage;

    }

Adjust to taste for multiple monitor scenarios (although it sounds like this should work just fine for your application).

Answer 3

You might look at using GetDesktopWindow through p/invoke, then get the device context and take your snapshot. There is a very detailed tutorial here. It might be better than perturbing the existing windows.

Answer 4

All former answers are completely wrong (minimizing apps is absurd)
Simply use SHW api : one line of code (the desktop bitmap being cached, the api simply blits it to your HDC...)