public void SetBitmap(Bitmap bitmap, byte opacity)
{
if (!haveHandle)
{
return;
}
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("位图必须是32位包含alpha 通道");
}
IntPtr screenDc = Win32.GetDC(IntPtr.Zero);
IntPtr memDc = Win32.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
try
{
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0)); // 创建GDI位图句柄，效率较低
oldBitmap = Win32.SelectObject(memDc, hBitmap);
Interop.Size size = new Interop.Size(bitmap.Width, bitmap.Height);
Interop.Point pointSource = new Interop.Point(0, 0);
Interop.Point topPos = new Interop.Point(Left, Top);
Interop.BLENDFUNCTION blend = new Interop.BLENDFUNCTION();
blend.BlendOp = Win32.AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = opacity;
blend.AlphaFormat = Win32.AC_SRC_ALPHA;
Win32.UpdateLayeredWindow(Handle, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, Win32.ULW_ALPHA);
}
finally
{
Win32.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
Win32.SelectObject(memDc, oldBitmap);
Win32.DeleteObject(hBitmap);
}
Win32.DeleteDC(memDc);
}
}
