Accessing Memory DC contents
Posted on 1997-09-18
I created a memory device context with the following functions:
--- Note the big size of the bitmap ---
Then I blit a part of it (640x480) on the screen with CDC::BitBlt();
I would like to modify a dozen of small parts in my compatible bitmap (64 x 64 pixel squares), so that the changes appear on the screen in the next BitBlt().
It don't want to have to copy again all the 5040 x 800 pixels !!
I just want a way to directly access the data used by the compatible dc.
I'll give a A if I get a way to access directly the data in memory (not with BitBlt() or something like that).
I'll give a B for a way to do it without having to create a compatible DC or a Bitmap for each little square.
I already CAN do it by creating a DC for each square, so please don't explain me this method :) .I would like, again, direct access to memory.
Note: if I ask the compatible bitmap to fill a BITMAP structure, all attempts to write these bits cause a protection fault (pointers are valid, but I'm under NT 4, and I don't have write access using this method)