Prev: svg example
Next: wxList problem
From: "Steven Van Ingelgem" on 22 Mar 2008 16:06
system: VS2005/trunk/XP


Hi,


How can I draw on a bitmap in such a way that I get a bitmap with a
transparent background?


What I do at the moment is:

dc.SetBackground( *wxTRANSPARENT_BRUSH );
dc.SetBackgroundMode(wxTRANSPARENT);
dc.SetBrush( *wxTRANSPARENT_BRUSH );
dc.Clear();

& than dc.SetTextForeground to set the colour of my text... But still
it keeps on giving me a black background.

I think it's because in dc.cpp (1650), SetBkColor receives the
wxTRANSPARENTBRUSH, which is equal to 0x02 00 00 00 (thus wxBlack).
Now SetBkColor expects CLR_NONE to set the background really
transparent, which is 0xFF FF FF FF (at least on windows that is).


Could someone tell me if I'm wrong here and/or what I should do to correct it?


Thanks!
_______________________________________________
wx-users mailing list
wx-users(a)lists.wxwidgets.org
http://lists.wxwidgets.org/mailman/listinfo/wx-users

From: "Steven Van Ingelgem" on 22 Mar 2008 16:28
Proof of concept:

Index: minimal.cpp
===================================================================
--- minimal.cpp (revision 52691)
+++ minimal.cpp (working copy)
@@ -148,6 +148,18 @@
// set the frame icon
SetIcon(wxICON(sample));

+
+ wxInitAllImageHandlers();
+
+ wxBitmap bmp(100,100);
+ wxMemoryDC dc(bmp);
+ dc.SetBackground( *wxTRANSPARENT_BRUSH );
+ dc.Clear();
+ dc.SetTextForeground( *wxRED );
+ dc.DrawText( "This is a BUG!", 0, 0 );
+ dc.SelectObject( wxNullBitmap );
+ bmp.SaveFile( "/tmp/Testing.png", wxBITMAP_TYPE_PNG );
+
#if wxUSE_MENUS
// create a menu bar
wxMenu *fileMenu = new wxMenu;



Behaviour: This will create a black bitmap with red text.
Expected: A transparent image with red text.


Greetings


On 22/03/2008, Steven Van Ingelgem <steven(a)vaningelgem.be> wrote:
> system: VS2005/trunk/XP
>
>
> Hi,
>
>
> How can I draw on a bitmap in such a way that I get a bitmap with a
> transparent background?
>
>
> What I do at the moment is:
>
> dc.SetBackground( *wxTRANSPARENT_BRUSH );
> dc.SetBackgroundMode(wxTRANSPARENT);
> dc.SetBrush( *wxTRANSPARENT_BRUSH );
> dc.Clear();
>
> & than dc.SetTextForeground to set the colour of my text... But still
> it keeps on giving me a black background.
>
> I think it's because in dc.cpp (1650), SetBkColor receives the
> wxTRANSPARENTBRUSH, which is equal to 0x02 00 00 00 (thus wxBlack).
> Now SetBkColor expects CLR_NONE to set the background really
> transparent, which is 0xFF FF FF FF (at least on windows that is).
>
>
> Could someone tell me if I'm wrong here and/or what I should do to correct it?
>
>
> Thanks!
>
_______________________________________________
wx-users mailing list
wx-users(a)lists.wxwidgets.org
http://lists.wxwidgets.org/mailman/listinfo/wx-users

 | 
Pages: 1
Prev: svg example
Next: wxList problem