> Ok. thanks for those links. but - i dont think that this will help me. > > i have subclassed an Fl_Double_Window and written my own > "virtual void draw()" function, so that i can paint inside > that Fl_Double_Window using the simple draw methods provided > by fltk ( for example fl_line(..) ). > > now i need to get access to that drawing somehow, so that i > can save it. > > of what use should it be, if i attach a background image to > that window using "w->image(my_fl_rgb_image);" ? is the > attached image modified by / drawn over by the fltk draw commands ? > > the question is: how is drawing stuff in fltk handled > internally? is it a stored list of draw-commands, or is there > an image-buffer that stores pixels, wich then get modified by > fl_line etc calls? if such an internal buffer exists, is > there a hacky / tricky / legal way to access it?
OK - sounds like you probably want to use fl_offscreen instead then. You create the offscreen context, and render to that as if it were your normal window. Note that the offscreen can be selected and drawn to at any time, not just during a "draw" method, so in some uses this is more convenient. You can also composite multiple images here, or use a pixmap as a background or etc. In your "draw" method for your displayed window, you just blit the offscreen image into the window. And of course you can get a handle to the underlying data... Alternately, you can get a handle to the data for the current window by using uchar *fl_read_image(uchar *p, int X, int Y, int W, int H, int alpha = 0); Either in your existing draw method, or by using Fl_Window::make_current() elsewhere to set a given window "current" whilst you read back its content. The difficulty with this approach is that (in some implementations) fl_read_image() will literally read back from the screen buffer, so if there are other windows or cursors or etc on the screen, they may get into your grabbed image - in this case, using an offscreen for your rendering my be better since the offscreen is obvioulsy private to your application. SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Basildon, Essex SS14 3EL A company registered in England & Wales. Company no. 02426132 ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** _______________________________________________ fltk mailing list [email protected] http://lists.easysw.com/mailman/listinfo/fltk
