// 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
var screenDc = NativeMethods.GetDC(IntPtr.Zero);
var memDc = NativeMethods.CreateCompatibleDC(screenDc);
var hBitmap = IntPtr.Zero;
var 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 = NativeMethods.SelectObject(memDc, hBitmap);
// Set parameters for layered window update
var newSize = new NativeMethods.Size(bitmap.Width, bitmap.Height);
// Size window to match bitmap
var sourceLocation = new NativeMethods.Point(0, 0);
var newLocation = new NativeMethods.Point(Left, Top); // Same as this window
var blend = new NativeMethods.Blendfunction
{
BlendOp = NativeMethods.AcSrcOver,
BlendFlags = 0,
SourceConstantAlpha = 255,
AlphaFormat = NativeMethods.AcSrcAlpha
};
// Only works with a 32bpp bitmap
// Always 0
// Set to 255 for per-pixel alpha values
// Only works when the bitmap contains an alpha channel
// Update the window
NativeMethods.UpdateLayeredWindow(Handle, screenDc, ref newLocation, ref newSize,
memDc, ref sourceLocation, 0, ref blend, NativeMethods.UlwAlpha);
}
finally
{
// Release device context
NativeMethods.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
NativeMethods.SelectObject(memDc, hOldBitmap);
NativeMethods.DeleteObject(hBitmap); // Remove bitmap resources
}
NativeMethods.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
var screenDc = NativeMethods.GetDC(IntPtr.Zero);
var memDc = NativeMethods.CreateCompatibleDC(screenDc);
var hBitmap = IntPtr.Zero;
var 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 = NativeMethods.SelectObject(memDc, hBitmap);
// Set parameters for layered window update
var newSize = new NativeMethods.Size(bitmap.Width, bitmap.Height);
// Size window to match bitmap
var sourceLocation = new NativeMethods.Point(0, 0);
var newLocation = new NativeMethods.Point(Left, Top); // Same as this window
var blend = new NativeMethods.Blendfunction
{
BlendOp = NativeMethods.AcSrcOver,
BlendFlags = 0,
SourceConstantAlpha = 255,
AlphaFormat = NativeMethods.AcSrcAlpha
};
// Only works with a 32bpp bitmap
// Always 0
// Set to 255 for per-pixel alpha values
// Only works when the bitmap contains an alpha channel
// Update the window
NativeMethods.UpdateLayeredWindow(Handle, screenDc, ref newLocation, ref newSize,
memDc, ref sourceLocation, 0, ref blend, NativeMethods.UlwAlpha);
}
finally
{
// Release device context
NativeMethods.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
NativeMethods.SelectObject(memDc, hOldBitmap);
NativeMethods.DeleteObject(hBitmap); // Remove bitmap resources
}
NativeMethods.DeleteDC(memDc);
}
}
