Copy window DC for later use in offscreen DC

uwi2k2 · #1 24-Apr-2009, 04:30

hi all,

first, i am german so my english might not be best. sorry for that.

for my small gdi 2d game i like to have a offscreen DC to draw in
but mostly to save a copy of the window DC ( the visible one ).

here comes a short scratch of what i am trying to do
...

CPP / C++ / C Code:

// !! used variables are all declared allredy !!
// get handel to window DC
handel = GetDC( hwnd );
// make offscreen DC and comp. bitmap in it
BackBuffer = CreateCompatibleDC( handel );
BackBit     = CreateCompatibleBitmap( BackBuffer ,500 , 500  );

... load and blit some *.bmp files to window DC ( handel )

// TIMEPOINT A : blit window DC to offscreen DC ( with all the *.bmp stuff in it )
BitBlt( BackBuffer , 0 ,0 ,500 ,500 ,handel ,0 ,0 ,SRCCOPY );

... go on with drawing in the window DC ( handel )

// blit the old status from TIMEPOINT A  from the  backbuffer DC back to Window DC 
BitBlt( handel , 0 , 0 , 500, 500, BackBuffer, 0 , 0 , SRCCOPY);

i hope you understand what i am trying to do:
i´d like to save a copy of alle the stuff drawn and loaded to the window DC in a offscreen DC to gat it back on the screen later.
sadly it does not work, drawn objects like rectangles are copyed to the backbuffer but loaded and blited *.bmp´s are not, they are somehow ignored.

hopefully you can tell me what is wrong, or how it works.

thanks ...

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