Fliped cursor icon on desktop recording using directshow

问题

Using Directshow.NET I have developed an application which will record the desktop screen, to get mouse pointer we need to paint mouse pointer by our own. So I added SampleGrabber adn in BufferCB I have written below code:

    public const Int32 CURSOR_SHOWING = 0x00000001;

    [StructLayout(LayoutKind.Sequential)]
    public struct ICONINFO
    {
        public bool fIcon;
        public Int32 xHotspot;
        public Int32 yHotspot;
        public IntPtr hbmMask;
        public IntPtr hbmColor;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct POINT
    {
        public Int32 x;
        public Int32 y;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct CURSORINFO
    {
        public Int32 cbSize;
        public Int32 flags;
        public IntPtr hCursor;
        public POINT ptScreenPos;
    }

    [DllImport("user32.dll")]
    public static extern bool GetCursorInfo(out CURSORINFO pci);

    [DllImport("user32.dll")]
    public static extern IntPtr CopyIcon(IntPtr hIcon);

    [DllImport("user32.dll")]
    public static extern bool DrawIcon(IntPtr hdc, int x, int y, IntPtr hIcon);

    [DllImport("user32.dll")]
    public static extern bool GetIconInfo(IntPtr hIcon, out ICONINFO piconinfo);

public int BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
{
Graphics g;
Bitmap v;
v = new Bitmap(m_videoWidth, m_videoHeight, m_stride, System.Drawing.Imaging.PixelFormat.Format24bppRgb, pBuffer);            
g = Graphics.FromImage(v);
CURSORINFO cursorInfo;
cursorInfo.cbSize = Marshal.SizeOf(typeof(CURSORINFO));

if (GetCursorInfo(out cursorInfo))
{
    if (cursorInfo.flags == CURSOR_SHOWING)
    {
        var iconPointer = CopyIcon(cursorInfo.hCursor);
        ICONINFO iconInfo;
        int iconX, iconY;

        if (GetIconInfo(iconPointer, out iconInfo))
        {
            iconX = cursorInfo.ptScreenPos.x - ((int)iconInfo.xHotspot);
            iconY = cursorInfo.ptScreenPos.y - ((int)iconInfo.yHotspot);

            DrawIcon(g.GetHdc(), iconX, iconY, cursorInfo.hCursor);
            g.ReleaseHdc();
            g.Dispose();
            v.Dispose();                        
        }
    }
}
return 0;
}

This code is painting the mouse cursor but cursor is flipped on Y axis.

It's may be because in BufferCB if we convert pBuffer in Bitmap then that frame is flipped on Y axis. To solve this I flipped current frame on Y axis by adding v.RotateFlip(RotateFlipType.RotateNoneFlipY); inside BufferCB after this change mouse pointer is not visible in desktop recording video.

How I can flip mouse pointer?

Update #1

I converted icon pointer to Icon then into Bitmap using Icon.ToBitmap() and then flipped on Y axis, here is code (Thanks to @Roman R.):

...
iconX = cursorInfo.ptScreenPos.x - ((int)iconInfo.xHotspot);
iconY = cursorInfo.ptScreenPos.y - ((int)iconInfo.yHotspot);

Icon ic = Icon.FromHandle(iconPointer);
Bitmap icon = ic.ToBitmap();
icon.RotateFlip(RotateFlipType.RotateNoneFlipY);
g.DrawImage(icon, iconX, iconY);
g.Dispose();
v.Dispose();
icon.Dispose();
ic.Dispose();  
...

Only one issue I am facing in above modification sometimes I get ArgumentException at line Bitmap icon = ic.ToBitmap();

  System.ArgumentException occurred
  HResult=-2147024809
  Message=Parameter is not valid.
  Source=System.Drawing
  StackTrace:
       at System.Drawing.Bitmap.FromHicon(IntPtr hicon)
  InnerException: 

I disposed all the bitmaps used, still i get this exception.

回答1:

The problem you have here is your BufferCB implementation. You create a temporary Graphics/Bitmap object, so that it could be updated with the cursor overlay. You have this bitmap upside down and normal draw of the icon applies it flipped.

You need to take into account that normal order of lines of 24-bit RGB buffer you get with BufferCB callback is bottom-to-top; order of lines Bitmap constructor expects is the opposite. You need to transfer lines into Bitmap in reversed order, then get them back respectively. I am not sure if negative stride works out there well, presumably it will not. Or simply overlay the cursor pre-flipped, to compensate for flipped background and overlay coordinates too.

回答2:

You have another option of painting correct mouse pointer. Just take a mouse pointer's PNG image and in BufferCB:

public int BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
{
Graphics g;
Bitmap v;
v = new Bitmap(m_videoWidth, m_videoHeight, m_stride, System.Drawing.Imaging.PixelFormat.Format24bppRgb, pBuffer);            
g = Graphics.FromImage(v);
CURSORINFO cursorInfo;
cursorInfo.cbSize = Marshal.SizeOf(typeof(CURSORINFO));

if (GetCursorInfo(out cursorInfo))
{
    if (cursorInfo.flags == CURSOR_SHOWING)
    {
        var iconPointer = CopyIcon(cursorInfo.hCursor);
        ICONINFO iconInfo;
        int iconX, iconY;

        if (GetIconInfo(iconPointer, out iconInfo))
        {
            iconX = cursorInfo.ptScreenPos.x - ((int)iconInfo.xHotspot);
            iconY = cursorInfo.ptScreenPos.y - ((int)iconInfo.yHotspot);

            //DRAW STATIC POINTER IMAGE
            Bitmap pointerImage = new Bitmap('pointer.png');
            g.DrawImage(pointerImage,iconX,iconY);

            g.Dispose();
            v.Dispose();                        
        }
    }
}
return 0;
}

来源：https://stackoverflow.com/questions/35339408/fliped-cursor-icon-on-desktop-recording-using-directshow