public void SetView(Bitmap newView, int newOpacity)
{
if (newView == null) return;
if (newView.PixelFormat != PixelFormat.Format32bppArgb)
throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");
View = newView;
Opacity = newOpacity%256;
IntPtr screenDc = User.GetDC(IntPtr.Zero);
IntPtr memDc = GDI.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
try
{
hBitmap = newView.GetHbitmap(Color.FromArgb(0));
oldBitmap = GDI.SelectObject(memDc, hBitmap);
var size = new SIZE {cx = newView.Width, cy = newView.Height};
var pointSource = new POINT {x = 0, y = 0};
var topPos = new POINT {x = Left, y = Top};
var blend = new User.BLENDFUNCTION
{
BlendOp = User.AC_SRC_OVER,
BlendFlags = 0,
SourceConstantAlpha = (byte) newOpacity,
AlphaFormat = User.AC_SRC_ALPHA
};
User.UpdateLayeredWindow(Handle, screenDc, ref topPos,
ref size, memDc, ref pointSource,
0,
ref blend, User.ULW_ALPHA);
}
finally
{
User.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
GDI.SelectObject(memDc, oldBitmap);
GDI.DeleteObject(hBitmap);
}
GDI.DeleteDC(memDc);
}
}
public static extern int SetViewportExtEx(IntPtr hdc, int nX, int nY, ref SIZE lpSize);
public static extern int SetWindowExtEx(IntPtr hdc, int nX, int nY, ref SIZE lpSize);
public static extern int ScaleWindowExtEx(IntPtr hdc, int nXnum, int nXdenom, int nYnum, int nYdenom,
ref SIZE lpSize);
public static extern int SetBitmapDimensionEx(IntPtr hbm, int nX, int nY, ref SIZE lpSize);
public static extern int GetViewportExtEx(IntPtr hdc, ref SIZE lpSize);
public static extern int GetWindowExtEx(IntPtr hdc, ref SIZE lpSize);
public static extern int GetTextExtentPoint32(IntPtr hdc, string lpsz, int cbString, ref SIZE lpSize);
public static extern int GetTextExtentExPoint(IntPtr hdc, string lpszStr, int cchString, int nMaxExtent,
ref int lpnFit, int alpDx, ref SIZE lpSize);
public static extern int GetBitmapDimensionEx(IntPtr hBitmap, ref SIZE lpDimension);
public static extern int GetAspectRatioFilterEx(IntPtr hdc, ref SIZE lpAspectRatio);
public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst,
ref POINT pptDst, ref SIZE psize, IntPtr hdcSrc, ref POINT pptSrc,
uint crKey,
[In] ref BLENDFUNCTION pblend, uint dwFlags);
