NtUserGetLayeredWindowAttributes - NtDoc

#ifndef _NTUSER_H

NTSYSCALLAPI
BOOL
NTAPI
NtUserGetLayeredWindowAttributes(
    _In_ HWND WindowHandle,
    _In_ COLORREF* pcrKey,
    _In_ BYTE* pbAlpha,
    _In_ ULONG pdwFlags
    );

#endif
View code on GitHub