// Sets the current bitmap
public void SelectBitmap(Bitmap bitmap)
{
// Does this bitmap contain an alpha channel?
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("The bitmap must be 32bpp with alpha-channel.");
}
// Get device contexts
IntPtr screenDc = APIHelp.GetDC(IntPtr.Zero);
IntPtr memDc = APIHelp.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr hOldBitmap = IntPtr.Zero;
try
{
// Get handle to the new bitmap and select it into the current device context
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
hOldBitmap = APIHelp.SelectObject(memDc, hBitmap);
// Set parameters for layered window update
APIHelp.Size newSize = new APIHelp.Size(bitmap.Width, bitmap.Height); // Size window to match bitmap
APIHelp.Point sourceLocation = new APIHelp.Point(0, 0);
APIHelp.Point newLocation = new APIHelp.Point(this.Left, this.Top); // Same as this window
APIHelp.BLENDFUNCTION blend = new APIHelp.BLENDFUNCTION();
blend.BlendOp = APIHelp.AC_SRC_OVER; // Only works with a 32bpp bitmap
blend.BlendFlags = 0; // Always 0
blend.SourceConstantAlpha = 255; // Set to 255 for per-pixel alpha values
blend.AlphaFormat = APIHelp.AC_SRC_ALPHA; // Only works when the bitmap contains an alpha channel
// Update the window
APIHelp.UpdateLayeredWindow(Handle, screenDc, ref newLocation, ref newSize,
memDc, ref sourceLocation, 0, ref blend, APIHelp.ULW_ALPHA);
}
finally
{
// Release device context
APIHelp.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
APIHelp.SelectObject(memDc, hOldBitmap);
APIHelp.DeleteObject(hBitmap); // Remove bitmap resources
}
APIHelp.DeleteDC(memDc);
}
}
// Sets the current bitmap
public void SelectBitmap(Bitmap bitmap)
{
// Does this bitmap contain an alpha channel?
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("The bitmap must be 32bpp with alpha-channel.");
}
// Get device contexts
IntPtr screenDc = APIHelp.GetDC(IntPtr.Zero);
IntPtr memDc = APIHelp.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr hOldBitmap = IntPtr.Zero;
try
{
// Get handle to the new bitmap and select it into the current device context
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
hOldBitmap = APIHelp.SelectObject(memDc, hBitmap);
// Set parameters for layered window update
APIHelp.Size newSize = new APIHelp.Size(bitmap.Width, bitmap.Height); // Size window to match bitmap
APIHelp.Point sourceLocation = new APIHelp.Point(0, 0);
APIHelp.Point newLocation = new APIHelp.Point(this.Left, this.Top); // Same as this window
APIHelp.BLENDFUNCTION blend = new APIHelp.BLENDFUNCTION();
blend.BlendOp = APIHelp.AC_SRC_OVER; // Only works with a 32bpp bitmap
blend.BlendFlags = 0; // Always 0
blend.SourceConstantAlpha = 255; // Set to 255 for per-pixel alpha values
blend.AlphaFormat = APIHelp.AC_SRC_ALPHA; // Only works when the bitmap contains an alpha channel
// Update the window
APIHelp.UpdateLayeredWindow(Handle, screenDc, ref newLocation, ref newSize,
memDc, ref sourceLocation, 0, ref blend, APIHelp.ULW_ALPHA);
}
finally
{
// Release device context
APIHelp.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
APIHelp.SelectObject(memDc, hOldBitmap);
APIHelp.DeleteObject(hBitmap); // Remove bitmap resources
}
APIHelp.DeleteDC(memDc);
}
}
