/// <summary> /// Changes the current bitmap shown in the form with a custom opacity level and alpha blending. Here is where all happens! /// The size of the bitmap drawn is equal to the size of the given "bitmap". /// This is a private method. Use the other managed methods to perform the bitmap setting operations. /// </summary> /// <param name="bitmap">The bitmap must be 32ppp with alpha-channel.</param> /// <param name="opacity">0-255</param> private void SetBitmap(ref Bitmap bitmap, byte opacity, bool SetNewPos, int NewLeftPos, int NewTopPos) { if (bitmap.PixelFormat != PixelFormat.Format32bppArgb) { throw new ApplicationException("The bitmap must be 32ppp with alpha-channel."); } // The idea 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 = Win32.GetDC(IntPtr.Zero); IntPtr memDc = Win32.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 = Win32.SelectObject(memDc, hBitmap); Win32.Size size = new Win32.Size(bitmap.Width, bitmap.Height); Win32.Point pointSource = new Win32.Point(0, 0); Win32.Point topPos; if (SetNewPos == true) { topPos = new Win32.Point(NewLeftPos, NewTopPos); //Very important to update the Location because UpdateLayeredWindow doesn't do it correctly. this.Location = new Point(NewLeftPos, NewTopPos); } else { topPos = new Win32.Point(Left, Top); this.Location = new Point(Left, Top); } Win32.BLENDFUNCTION blend = new Win32.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); //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. Win32.DeleteObject(hBitmap); } Win32.DeleteDC(memDc); } }
private void SetBitmap(ref Bitmap bitmap, byte opacity, bool SetNewPos, int NewLeftPos, int NewTopPos) { IntPtr dC = Win32.GetDC(IntPtr.Zero); IntPtr intPtr = Win32.CreateCompatibleDC(dC); IntPtr intPtr2 = IntPtr.Zero; IntPtr hObject = IntPtr.Zero; try { intPtr2 = bitmap.GetHbitmap(Color.FromArgb(0)); hObject = Win32.SelectObject(intPtr, intPtr2); Win32.Size size = new Win32.Size(bitmap.Width, bitmap.Height); Win32.Point point = new Win32.Point(0, 0); Win32.Point point2; if (SetNewPos) { point2 = new Win32.Point(NewLeftPos, NewTopPos); base.Location = new Point(NewLeftPos, NewTopPos); } else { point2 = new Win32.Point(base.Left, base.Top); base.Location = new Point(base.Left, base.Top); } Win32.BLENDFUNCTION bLENDFUNCTION = default(Win32.BLENDFUNCTION); bLENDFUNCTION.BlendOp = 0; bLENDFUNCTION.BlendFlags = 0; bLENDFUNCTION.SourceConstantAlpha = opacity; bLENDFUNCTION.AlphaFormat = 1; Win32.UpdateLayeredWindow(base.Handle, dC, ref point2, ref size, intPtr, ref point, 0, ref bLENDFUNCTION, 2); } catch (Exception) { } finally { Win32.ReleaseDC(IntPtr.Zero, dC); if (intPtr2 != IntPtr.Zero) { Win32.SelectObject(intPtr, hObject); Win32.DeleteObject(intPtr2); } Win32.DeleteDC(intPtr); } }
public static extern Win32.Bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref Win32.Point pptDst, ref Win32.Size psize, IntPtr hdcSrc, ref Win32.Point pprSrc, int crKey, ref Win32.BLENDFUNCTION pblend, int dwFlags);