c# - Capture screen of Window by handle

Question

I'm trying to capture only a specific Window in the desktop but I'm getting a mixed image, part of window and part desktop area.

What am I missing?

Here's my code:

RECT rect = new RECT();

if (!SetForegroundWindow(handle))
    throw new Win32Exception(Marshal.GetLastWin32Error());

if (!GetWindowRect(handle, out rect))
    throw new Win32Exception(Marshal.GetLastWin32Error());

Thread.Sleep(500);

Rectangle windowSize = rect.ToRectangle();
Bitmap target = new Bitmap(windowSize.Width, windowSize.Height);
using (Graphics g = Graphics.FromImage(target))
{
    g.CopyFromScreen(0, 0, 0, 0, new Size(windowSize.Width, windowSize.Height));
}

target.Save("foo.png", System.Drawing.Imaging.ImageFormat.Png);

Answer 1

I think the problem in your code is this line:

g.CopyFromScreen(0, 0, 0, 0, new Size(windowSize.Width, windowSize.Height));

It should be:

g.CopyFromScreen(windowSize.X, windowSize.Y, 0, 0, new Size(windowSize.Width, windowSize.Height));

Here is the method I personally use to get an image of a particular window - it might come in handy:

public Bitmap GetScreenshot()
{
    IntPtr hwnd = ihandle;//handle here

    RECT rc;
    Win32.GetWindowRect(new HandleRef(null, hwnd), out rc);

    Bitmap bmp = new Bitmap(rc.Right - rc.Left, rc.Bottom - rc.Top, PixelFormat.Format32bppArgb);
    Graphics gfxBmp = Graphics.FromImage(bmp);
    IntPtr hdcBitmap;
    try
    {
        hdcBitmap = gfxBmp.GetHdc();
    }
    catch
    {
        return null;
    }
    bool succeeded = Win32.PrintWindow(hwnd, hdcBitmap, 0);
    gfxBmp.ReleaseHdc(hdcBitmap);
    if (!succeeded)
    {
        gfxBmp.FillRectangle(new SolidBrush(Color.Gray), new Rectangle(Point.Empty, bmp.Size));
    }
    IntPtr hRgn = Win32.CreateRectRgn(0, 0, 0, 0);
    Win32.GetWindowRgn(hwnd, hRgn);
    Region region = Region.FromHrgn(hRgn);//err here once
    if (!region.IsEmpty(gfxBmp))
    {
        gfxBmp.ExcludeClip(region);
        gfxBmp.Clear(Color.Transparent);
    }
    gfxBmp.Dispose();
    return bmp;
 }