Capturing a window with WPF

Question

With Windows Presentation Foundation, if I have an HWND, how can I capture it\'s window as an image that I can manipulate and display?

Answer 1

While above answer is great, this would have saved a ton of time too:

Using section:

using System;
using System.Windows;
using System.Windows.Interop;
using System.Runtime.InteropServices;
using System.Windows.Media.Imaging;

Code:

/// 

/// Captures screenshot using WINAPI.
/// 
static public class CaptureScreenshot
{
    /// 

    /// Capture the screenshot.
    /// Area of screenshot.
    /// Bitmap source that can be used e.g. as background.
    /// 
    public static BitmapSource Capture(Rect area)
    {
        IntPtr screenDC = GetDC(IntPtr.Zero);
        IntPtr memDC = CreateCompatibleDC(screenDC);
        IntPtr hBitmap = CreateCompatibleBitmap(screenDC, (int)SystemParameters.VirtualScreenWidth, (int)SystemParameters.VirtualScreenHeight);
        SelectObject(memDC, hBitmap); // Select bitmap from compatible bitmap to memDC

        // TODO: BitBlt may fail horribly
        BitBlt(memDC, 0, 0, (int)area.Width, (int)area.Height, screenDC, (int)area.X, (int)area.Y, TernaryRasterOperations.SRCCOPY);
        BitmapSource bsource = Imaging.CreateBitmapSourceFromHBitmap(hBitmap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());

        DeleteObject(hBitmap);
        ReleaseDC(IntPtr.Zero, screenDC);
        ReleaseDC(IntPtr.Zero, memDC);
        return bsource;
    }

    #region WINAPI DLL Imports

    [DllImport("gdi32.dll", ExactSpelling = true, PreserveSig = true, SetLastError = true)]
    static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);

    [DllImport("gdi32.dll", SetLastError = true)]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll")]
    private static extern bool DeleteObject(IntPtr hObject);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateBitmap(int nWidth, int nHeight, uint cPlanes, uint cBitsPerPel, IntPtr lpvBits);

    [DllImport("user32.dll")]
    private static extern IntPtr GetDC(IntPtr hWnd);

    [DllImport("user32.dll")]
    private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

    private enum TernaryRasterOperations : uint
    {
        /// 
dest = source
        SRCCOPY = 0x00CC0020,
        /// 
dest = source OR dest
        SRCPAINT = 0x00EE0086,
        /// 
dest = source AND dest
        SRCAND = 0x008800C6,
        /// 
dest = source XOR dest
        SRCINVERT = 0x00660046,
        /// 
dest = source AND (NOT dest)
        SRCERASE = 0x00440328,
        /// 
dest = (NOT source)
        NOTSRCCOPY = 0x00330008,
        /// 
dest = (NOT src) AND (NOT dest)
        NOTSRCERASE = 0x001100A6,
        /// 
dest = (source AND pattern)
        MERGECOPY = 0x00C000CA,
        /// 
dest = (NOT source) OR dest
        MERGEPAINT = 0x00BB0226,
        /// 
dest = pattern
        PATCOPY = 0x00F00021,
        /// 
dest = DPSnoo
        PATPAINT = 0x00FB0A09,
        /// 
dest = pattern XOR dest
        PATINVERT = 0x005A0049,
        /// 
dest = (NOT dest)
        DSTINVERT = 0x00550009,
        /// 
dest = BLACK
        BLACKNESS = 0x00000042,
        /// 
dest = WHITE
        WHITENESS = 0x00FF0062
    }

    [DllImport("gdi32.dll")]
    private static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);

    #endregion
}

Notice that this takes screenshot of given area in the screen and not of window. It works for my purposes, you probably have to modify it for yours :)