public static extern BOOL UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref POINT pptDst, ref SIZE psize, IntPtr hdcSrc, ref POINT pprSrc, Int32 crKey, ref GDI32.BLENDFUNCTION pblend, Int32 dwFlags);
/// <summary>
/// Redraws the bitmap overlay.
/// </summary>
/// <returns>True if successful, false otherwise.</returns>
protected bool RefreshBitmap()
{
// The bitmap must be 32-bit RGBA
if (_bitmap == null || _bitmap.PixelFormat != PixelFormat.Format32bppArgb)
return false;
// Create a memory DC that's compatible with the screen
IntPtr screenDC = Win32.GetDC(IntPtr.Zero);
if (screenDC == IntPtr.Zero)
return false;
IntPtr memDC = GDI32.CreateCompatibleDC(screenDC);
if (memDC == IntPtr.Zero)
{
Win32.ReleaseDC(IntPtr.Zero, screenDC);
return false;
}
// Prepare to draw the bitmap
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
bool success = false;
try
{
// Select the bitmap into the memory DC
hBitmap = _bitmap.GetHbitmap(Color.FromArgb(0)); // grab a GDI handle from this GDI+ bitmap
oldBitmap = GDI32.SelectObject(memDC, hBitmap);
// Call UpdateLayeredWindow to effectively blit the contents of the memory DC into the form while performing alpha blending
Win32.POINT windowTopLeft = new Win32.POINT(Left, Top);
Win32.SIZE bitmapSize = new Win32.SIZE(_bitmap.Width, _bitmap.Height);
Win32.POINT bitmapTopLeft = new Win32.POINT(0, 0);
byte blendAlpha = 0;
if (_bitmapOpacity < 0)
blendAlpha = 0;
else if (_bitmapOpacity > 1)
blendAlpha = 255;
else
blendAlpha = (byte)(_bitmapOpacity * 255);
GDI32.BLENDFUNCTION blendFunc = new GDI32.BLENDFUNCTION();
blendFunc.BlendOp = GDI32.AC_SRC_OVER;
blendFunc.BlendFlags = 0;
blendFunc.SourceConstantAlpha = blendAlpha;
blendFunc.AlphaFormat = GDI32.AC_SRC_ALPHA;
Win32.UpdateLayeredWindow(Handle, screenDC, ref windowTopLeft, ref bitmapSize, memDC, ref bitmapTopLeft, 0, ref blendFunc, Win32.ULW_ALPHA);
success = true;
}
finally
{
// Clean up the resources
if (hBitmap != IntPtr.Zero)
{
GDI32.SelectObject(memDC, oldBitmap);
GDI32.DeleteObject(hBitmap);
}
GDI32.DeleteDC(memDC);
Win32.ReleaseDC(IntPtr.Zero, screenDC);
}
return success;
}
/// <summary>
/// Redraws the bitmap overlay.
/// </summary>
/// <returns>True if successful, false otherwise.</returns>
protected bool RefreshBitmap()
{
// The bitmap must be 32-bit RGBA
if (_bitmap == null || _bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
return(false);
}
// Create a memory DC that's compatible with the screen
IntPtr screenDC = Win32.GetDC(IntPtr.Zero);
if (screenDC == IntPtr.Zero)
{
return(false);
}
IntPtr memDC = GDI32.CreateCompatibleDC(screenDC);
if (memDC == IntPtr.Zero)
{
Win32.ReleaseDC(IntPtr.Zero, screenDC);
return(false);
}
// Prepare to draw the bitmap
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
bool success = false;
try
{
// Select the bitmap into the memory DC
hBitmap = _bitmap.GetHbitmap(Color.FromArgb(0)); // grab a GDI handle from this GDI+ bitmap
oldBitmap = GDI32.SelectObject(memDC, hBitmap);
// Call UpdateLayeredWindow to effectively blit the contents of the memory DC into the form while performing alpha blending
Win32.POINT windowTopLeft = new Win32.POINT(Left, Top);
Win32.SIZE bitmapSize = new Win32.SIZE(_bitmap.Width, _bitmap.Height);
Win32.POINT bitmapTopLeft = new Win32.POINT(0, 0);
byte blendAlpha = 0;
if (_bitmapOpacity < 0)
{
blendAlpha = 0;
}
else if (_bitmapOpacity > 1)
{
blendAlpha = 255;
}
else
{
blendAlpha = (byte)(_bitmapOpacity * 255);
}
GDI32.BLENDFUNCTION blendFunc = new GDI32.BLENDFUNCTION();
blendFunc.BlendOp = GDI32.AC_SRC_OVER;
blendFunc.BlendFlags = 0;
blendFunc.SourceConstantAlpha = blendAlpha;
blendFunc.AlphaFormat = GDI32.AC_SRC_ALPHA;
Win32.UpdateLayeredWindow(Handle, screenDC, ref windowTopLeft, ref bitmapSize, memDC, ref bitmapTopLeft, 0, ref blendFunc, Win32.ULW_ALPHA);
success = true;
}
finally
{
// Clean up the resources
if (hBitmap != IntPtr.Zero)
{
GDI32.SelectObject(memDC, oldBitmap);
GDI32.DeleteObject(hBitmap);
}
GDI32.DeleteDC(memDC);
Win32.ReleaseDC(IntPtr.Zero, screenDC);
}
return(success);
}
public static extern bool UpdateLayeredWindow(IntPtr hWnd, IntPtr hdcDst, ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pptSrc, int crKey, ref GDI32.BLENDFUNCTION pblend, int dwFlags);
