wxImage->SetAlpha
in [wxWindows]
|
Prev: Sending a large request via HTTP, no response at wxGTK
Next: Compiling the sample "minimal" with VC++ 2008
From: Tommy W on 20 Apr 2007 13:48 Hi, I have a wxImage which I want to make see-through. What would be the best way of achieving this? char alpha[WIDTH* HEIGHT]; /* set the values here */ or should it be char alpha[WIDTH*HEIGHT*3]; !? wxImage i(_T("file.png")); i->SetAlpha(alpha,true); wxBitmap *b = new wxBitmap(i); Is this the proper way to do it ? performing a for(int y;y<height;y++) for(int x;x<width;x++) i->SetAlpha(x,y,value); seems abit slow. And how 'slow' is wxBitmap *b = new wxBitmap(i); I guess it would be stupid to do it in the PaintEvent ? Thanks in advance /Tommy Wallberg --------------------------------------------------------------------- To unsubscribe, e-mail: wx-users-unsubscribe(a)lists.wxwidgets.org For additional commands, e-mail: wx-users-help(a)lists.wxwidgets.org
From: Vadim Zeitlin on 21 Apr 2007 07:15 On Fri, 20 Apr 2007 19:48:40 +0200 Tommy W <tommy(a)svearike.sytes.net> wrote: TW> I have a wxImage which I want to make see-through. TW> What would be the best way of achieving this? If you want just on-or-off transparency, then you can use a mask, i.e. select one of the image colours to be transparent. Otherwise you should use alpha. TW> char alpha[WIDTH* HEIGHT]; /* set the values here */ TW> or should it be TW> char alpha[WIDTH*HEIGHT*3]; !? No, alpha is 1 byte per pixel, just as the colour channels. TW> wxImage i(_T("file.png")); TW> i->SetAlpha(alpha,true); TW> wxBitmap *b = new wxBitmap(i); TW> TW> Is this the proper way to do it ? You don't need to do anything if you load wxImage from a PNG with alpha. If you do set alpha data yourself, you need to at least initialize it. TW> And how 'slow' is wxBitmap *b = new wxBitmap(i); Quite slow. BTW, you really don't want to create bitmaps on heap as they're already pointers internally. Just do "wxBitmap b(i)". TW> I guess it would be stupid to do it in the PaintEvent ? Yes, avoid if you can. If you can't, look at wxRawBitmap. Regards, VZ -- TT-Solutions: wxWidgets consultancy and technical support http://www.tt-solutions.com/ --------------------------------------------------------------------- To unsubscribe, e-mail: wx-users-unsubscribe(a)lists.wxwidgets.org For additional commands, e-mail: wx-users-help(a)lists.wxwidgets.org
From: Tommy W on 21 Apr 2007 07:24
On Saturday 21 April 2007 13:15, Vadim Zeitlin wrote: > On Fri, 20 Apr 2007 19:48:40 +0200 Tommy W <tommy(a)svearike.sytes.net> > wrote: > > TW> I have a wxImage which I want to make see-through. > TW> What would be the best way of achieving this? > > If you want just on-or-off transparency, then you can use a mask, i.e. > select one of the image colours to be transparent. Otherwise you should use > alpha. The effect I'm looking for is "grayed-out", if you understand what I'm meaning? > TW> char alpha[WIDTH* HEIGHT]; /* set the values here */ > TW> or should it be > TW> char alpha[WIDTH*HEIGHT*3]; !? > > No, alpha is 1 byte per pixel, just as the colour channels. It was just that the documentation was a bit unclear, thanks for the elaboration. > TW> wxImage i(_T("file.png")); > TW> i->SetAlpha(alpha,true); > TW> wxBitmap *b = new wxBitmap(i); > TW> > TW> Is this the proper way to do it ? > > You don't need to do anything if you load wxImage from a PNG with alpha. > If you do set alpha data yourself, you need to at least initialize it. > > TW> And how 'slow' is wxBitmap *b = new wxBitmap(i); > > Quite slow. BTW, you really don't want to create bitmaps on heap as > they're already pointers internally. Just do "wxBitmap b(i)". > TW> I guess it would be stupid to do it in the PaintEvent ? > > Yes, avoid if you can. If you can't, look at wxRawBitmap. I will look that one up, thanks for all your help /Tommy --------------------------------------------------------------------- To unsubscribe, e-mail: wx-users-unsubscribe(a)lists.wxwidgets.org For additional commands, e-mail: wx-users-help(a)lists.wxwidgets.org |