Generate BitmapSource from UIElement

Question

I am attempting to generate a BitmapFrame that is based on a UIElement. Here is my function:

private BitmapFrame RenderToBitmap2()
{
           


        

Answer 1

I had the same issue before, I wanted to copy content of a UIElement to an image, I used the same approach in the answer above and it seems to work fine, only problem I has, I wanted it to work real-time, so I had to dig deeper, I found some references about using windows APIs to copy the content of the element into a Bitmap, and then this bitmap has to be converted into a BitmapSource so it's usable in WPF

so far it works fine, but it seems to leak memory (not sure about this). I will try to re-use the UIElement hwnd Handle and the bitmap object for better performance and the memory leak (if it exists)

[DllImport("gdi32.dll")]
private static extern bool BitBlt(
  IntPtr hdcDest, // handle to destination DC
  int nXDest, // x-coord of destination upper-left corner
  int nYDest, // y-coord of destination upper-left corner
  int nWidth, // width of destination rectangle
  int nHeight, // height of destination rectangle
  IntPtr hdcSrc, // handle to source DC
  int nXSrc, // x-coordinate of source upper-left corner
  int nYSrc, // y-coordinate of source upper-left corner
  System.Int32 dwRop // raster operation code
);

[DllImport("User32.dll")]
public extern static System.IntPtr GetDC(System.IntPtr hWnd);

[DllImport("User32.dll")]
public extern static int ReleaseDC(System.IntPtr hWnd, System.IntPtr hDC); //modified to include hWnd

//[DllImport("gdi32.dll")]
//[return: MarshalAs(UnmanagedType.Bool)]
//internal static extern bool DeleteObject(IntPtr hObject);

private static Bitmap GetBitmapFromControl(Window element, int width, int height)
{
    HwndSource hWnd = (HwndSource)HwndSource.FromVisual(element);
    System.IntPtr srcDC = GetDC(hWnd.Handle);

    Bitmap bm = new Bitmap(width, height);
    Graphics g = Graphics.FromImage(bm);
    System.IntPtr bmDC = g.GetHdc();
    BitBlt(bmDC, 0, 0, bm.Width, bm.Height, srcDC, 0, 0, 0x00CC0020 /*SRCCOPY*/);
    ReleaseDC(hWnd.Handle, srcDC);
    g.ReleaseHdc(bmDC);
    g.Dispose();

    return bm;
}

public static BitmapSource ToWpfBitmap(this Bitmap bitmap)
{
    using (MemoryStream stream = new MemoryStream())
    {
        bitmap.Save(stream, ImageFormat.Bmp);

        stream.Position = 0;
        BitmapImage result = new BitmapImage();
        result.BeginInit();
        // According to MSDN, "The default OnDemand cache option retains access to the stream until the image is needed."
        // Force the bitmap to load right now so we can dispose the stream.
        result.CacheOption = BitmapCacheOption.OnLoad;
        result.StreamSource = stream;
        result.EndInit();
        result.Freeze();


        //DeleteObject(bitmap.GetHbitmap());
        bitmap.Dispose();

        return result;
    }
}