CopyFromBitmap()
is a method on the ID2D1Bitmap
interface, so it implies that you have a bitmap already, which is the object that calls the copy function. Something like this ...
ID2D1Bitmap *pSourceBitmap = 0;
ID2D1Bitmap *pDestinationBitmap = 0;
// some initialisation of the above bitmaps goes here ...
// copy a region from source to destination
pDestinationBitmap->CopyFromBitmap(/*point you want to copy to*/, pSourceBitmap,
/*rect to copy from*/);