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Transparency without Source Code

, 11 Aug 2000
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Adding transparency to any window, even if you don't have its source.
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    When I checked the newly available APIs for Windows 2000, I ran into layered windows, and after playing around with it for a while, I finally wrote this cute little program. It allows you to add transparency to any window, just by clicking on it with your mouse.

    The core functionality is done in only 4 lines of code (6 if you include variable definitions). The rest is just wizard-generated MFC code.

    HWND hWnd;
    POINT pt;
    ::GetCursorPos(&pt);
    hWnd=::WindowFromPoint(pt);
    SetWindowLong(hWnd,GWL_EXSTYLE,GetWindowLong(hWnd,GWL_EXSTYLE)^WS_EX_LAYERED);
    SetLayeredWindowAttributes(hWnd,RGB(0,0,0),m_slider.GetPos(),LWA_ALPHA);
    

    First it finds the window under the current cursor position by using GetCursorPos() and WindowFromPoint, then it toggles its WS_EX_LAYERED (new in W2k) style using SetWindowLong, and finally, it sets its transparency to a value (between 0 and 255) defined by a slider control. The new SetLayeredWindowAttributes function is available only on Windows 2000, and is well-documented in the current MSDN library. You can also use it for color-keying, i.e. to make pixels of a specific color completely transparent, while leaving other pixels unchanged. The two effects can also be combined.

    SetLayeredWindowAttributes is defined as follows:

    BOOL SetLayeredWindowAttributes(
      HWND hwnd,           // handle to the layered window
      COLORREF crKey,      // specifies the color key
      BYTE bAlpha,         // value for the blend function
      DWORD dwFlags        // action
    );
    

    SetLayeredWindowAttributes can also be used to fade in/out other windows, or to create irregularly formed windows (this was also possible using window regions, but that was much slower).

    I personally use this program to make my Taskbar, ICQ and Winamp windows transparent, since these are always on top, and I prefer being able to see what happens behind them.

    Have Fun!

    License

    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

    A list of licenses authors might use can be found here

    About the Author

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    Comments and Discussions

     
    GeneralNot Working in Windows2000 service Pack 4 PinmemberGaurang Shah 03315-Aug-07 23:53 
    Generalerror LNK2001: unresolved external symbol __imp__SetLayeredWindowAttributes@16 Pinmemberjayender10-Aug-06 21:12 
    GeneralRe: error LNK2001: unresolved external symbol __imp__SetLayeredWindowAttributes@16 Pinmemberbob169727-Sep-06 6:13 
    Generalproblem in importing a dll in VC++ Pinsussvineet jain1-Apr-05 2:47 
    Generalerror LNK2001: unresolved external symbol __imp__ldap_init Pinmembermandanani24-Mar-05 22:50 
    GeneralRe: error LNK2001: unresolved external symbol __imp__ldap_init Pinsussvineet jain1-Apr-05 2:51 
    GeneralRe: error LNK2001: unresolved external symbol __imp__ldap_init PinmemberDoug Tomlinson2-Aug-05 2:28 
    GeneralRe: error LNK2001: unresolved external symbol __imp__ldap_init PinmemberDoug Tomlinson3-Aug-05 3:08 
    Generalwhy SetLayeredWindowAttributes can't used in 8bits(256) color quality Pinmemberwhizzkid@ms28.hinet.net11-Aug-04 4:07 
    GeneralAccessing layered window DC Pinmembersckaspick29-Jun-04 13:53 
    Generalcompile erro Pinmember_skidrow_vn_10-Feb-04 8:43 
    GeneralRe: compile erro PinmemberRRode10-Feb-05 6:28 
    Generalcompile error: unresolved external symbol __imp__... Pinsussx meng18-Nov-03 15:02 
    GeneralAlpha blend from a bitmap ! Pinmemberxela8-Oct-03 3:45 
    GeneralTransparency of individual components Pinmemberannation28-Aug-03 13:03 
    GeneralVC++ 7 Conversion Pinmembervisualflux13-Jun-03 10:29 
    GeneralTransparent inactive window Pinmemberlnkenjke26-May-03 8:11 
    GeneralDrawing on Transparent Window.. Pinmemberchamana3-Mar-03 20:12 
    GeneralRe: Drawing on Transparent Window.. PinmemberAlireza Mesgar29-Sep-04 1:45 
    GeneralThat's great ! PinmemberAlicia20033-Dec-02 3:23 
    Generalwindow transparency/color keying vs OpenGL Pinmemberolione29-Apr-02 2:54 
    GeneralRe: window transparency/color keying vs OpenGL PinmemberAnonymous9-Jun-02 12:23 
    QuestionHow do you change the window properties of a control bar so when it floats it transparent? PinmemberLucas Zanatta17-Mar-02 21:27 
    AnswerRe: How do you change the window properties of a control bar so when it floats it transparent? PinmemberAnonymous21-Apr-02 2:21 
    GeneralLuv the programm but.. PinmemberAlfred18-Dec-01 21:34 

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