/// <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);
