示例#1
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 public static extern bool UpdateLayeredWindow(IntPtr hWnd, IntPtr hdcDst, ref POINT pptDst, ref SIZE psize, IntPtr hdcSrc, ref POINT ppSrc, Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);
示例#2
0
        /// <summary>
        /// 设置图片为窗体,透明区域根据 opacity 的值决定透明度
        /// </summary>
        /// <param name="bitmap">透明位图</param>
        /// <param name="opacity">透明度的值0~255</param>
        public void SetBitmap(Bitmap bitmap, byte opacity)
        {
            if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
                throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");

            // The ideia of this is very simple,
            // 1. Create a compatible DC with screen;
            // 2. Select the bitmap with 32bpp with alpha-channel in the compatible DC;
            // 3. Call the UpdateLayeredWindow.

            IntPtr screenDc = NativeMethods.GetDC(IntPtr.Zero);
            IntPtr memDc = NativeMethods.CreateCompatibleDC(screenDc);
            IntPtr hBitmap = IntPtr.Zero;
            IntPtr oldBitmap = IntPtr.Zero;

            try
            {
                hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));  // grab a GDI handle from this GDI+ bitmap
                oldBitmap = NativeMethods.SelectObject(memDc, hBitmap);

                SIZE size = new SIZE(bitmap.Width, bitmap.Height);
                POINT pointSource = new POINT(0, 0);
                POINT topPos = new POINT(Left, Top);
                BLENDFUNCTION blend = new BLENDFUNCTION();
                blend.BlendOp = Consts.AC_SRC_OVER;
                blend.BlendFlags = 0;
                blend.SourceConstantAlpha = opacity;
                blend.AlphaFormat = Consts.AC_SRC_ALPHA;

                NativeMethods.UpdateLayeredWindow(Handle, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, Consts.ULW_ALPHA);
            }
            finally
            {
                NativeMethods.ReleaseDC(IntPtr.Zero, screenDc);
                if (hBitmap != IntPtr.Zero)
                {
                    NativeMethods.SelectObject(memDc, oldBitmap);
                    //Windows.DeleteObject(hBitmap); // The documentation says that we have to use the Windows.DeleteObject... but since there is no such method I use the normal DeleteObject from Win32 GDI and it's working fine without any resource leak.
                    NativeMethods.DeleteObject(hBitmap);
                }
                NativeMethods.DeleteDC(memDc);
            }
        }