/// <summary>
/// Creates a handle to a PARGB32 bitmap from an Icon.
/// </summary>
/// <param name="iconHandle">The handle to the icon.</param>
/// <param name="iconSize">The iconSize of the icon.</param>
/// <returns>A PARGB32 bitmap with the contents of the icon, including transparency.</returns>
public static IntPtr CreatePARGB32HBitmap(IntPtr iconHandle, Size iconSize)
{
// Make sure we're ready for buffered painting.
// TODO: Really we only need to do this once per thread, so an improvement
// might be to have a manager create this as required per thread.
Uxtheme.BufferedPaintInit();
// Create a compatible device context to work with.
var deviceContextHandle = Gdi32.CreateCompatibleDC(IntPtr.Zero);
if (deviceContextHandle == IntPtr.Zero)
{
return(IntPtr.Zero);
}
// Now create a 32 bit bitmap of the appropriate size, getting it's bits and handle.
IntPtr bits;
IntPtr hBitmap;
if (!Create32BitHBITMAP(deviceContextHandle, iconSize, out bits, out hBitmap))
{
Gdi32.DeleteDC(deviceContextHandle);
return(IntPtr.Zero);
}
// Select the bitmap, keeping track of the old one. If this fails,
// delete the device context and return a null handle.
var oldBitmapHandle = Gdi32.SelectObject(deviceContextHandle, hBitmap);
if (oldBitmapHandle == IntPtr.Zero)
{
Gdi32.DeleteDC(deviceContextHandle);
return(IntPtr.Zero);
}
// Create paint params that represent our alpha blending.
var bfAlpha = new BLENDFUNCTION
{
BlendOp = AC_SRC_OVER,
BlendFlags = 0,
SourceConstantAlpha = 255,
AlphaFormat = AC_SRC_ALPHA
};
var paintParams = new BP_PAINTPARAMS();
paintParams.cbSize = (uint)Marshal.SizeOf(paintParams);
paintParams.dwFlags = BPPF_ERASE;
paintParams.pBlendFunction = Marshal.AllocHGlobal(Marshal.SizeOf(bfAlpha));
Marshal.StructureToPtr(bfAlpha, paintParams.pBlendFunction, false);
// Create the pointer that'll hold the device context to the buffer, set the icon rectangle.
IntPtr bufferDeviceContextHandle;
var iconRect = new RECT(0, 0, iconSize.Width, iconSize.Height);
// Create a paint buffer handle.
var paintBufferHandle = Uxtheme.BeginBufferedPaint(deviceContextHandle, ref iconRect,
BP_BUFFERFORMAT.BPBF_DIB, ref paintParams, out bufferDeviceContextHandle);
// Free the memory we allocated for the blend function.
Marshal.FreeHGlobal(paintParams.pBlendFunction);
// If we created a paint buffer successfully, we can draw the icon into it.
if (paintBufferHandle != IntPtr.Zero)
{
// Try and draw the icon.
if (Gdi32.DrawIconEx(bufferDeviceContextHandle, 0, 0, iconHandle, iconSize.Width, iconSize.Height, 0, IntPtr.Zero,
(int)DI_NORMAL))
{
// Now convert the buffer we've painted into PARGB32, meaning we'll end up
// with a PARGB32 bitmap.
ConvertBufferToPARGB32(paintBufferHandle, deviceContextHandle, iconHandle, iconSize);
}
// This will write the buffer contents to the destination bitmap.
Uxtheme.EndBufferedPaint(paintBufferHandle, true);
}
// Select the old bitmpa and delete the device context.
Gdi32.SelectObject(deviceContextHandle, oldBitmapHandle);
Gdi32.DeleteDC(deviceContextHandle);
// We're done with buffered painting.
Uxtheme.BufferedPaintUnInit();
// Baddabing-baddabom, PARGB32.
return(hBitmap);
}