Creating a transparent window in C++ Win32

Question

I\'m creating what should be a very simple Win32 C++ app whose sole purpose it to ONLY display a semi-transparent PNG. The window shouldn\'t have any chrome, and all the opa

Answer 1

Use the SetLayeredWindowAttributes^archive function, this allows you to set a mask color that will become transparent, thus allowing the background to show through.

You will also need to configure your window with the layered flag, e.g.:

SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED);

After that it's fairly simple:

// Make red pixels transparent:
SetLayeredWindowAttributes(hwnd, RGB(255,0,0), 0, LWA_COLORKEY);

When your PNG contains semi-transparent pixels that you want to blend with the background, this becomes more complicated. You could try looking at the approach in this CodeProject article:

Cool, Semi-transparent and Shaped Dialogs with Standard Controls for Windows 2000 and Above