If you want to mirror it from right to left, a way is with StretchBlt
For example :
HBITMAP hBitmap = (HBITMAP)LoadImage(NULL, TEXT("E:\\takingphoto.bmp"), IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
int nX = 200, nY = 100;
BITMAP bm;
GetObject(hBitmap, sizeof(BITMAP), &bm);
HDC hDC = GetDC(NULL);
HDC hDCMem = CreateCompatibleDC(hDC);
HBITMAP hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap);
BitBlt(hDC, nX, nY, bm.bmWidth, bm.bmHeight, hDCMem, 0, 0, SRCCOPY);
nY += bm.bmHeight + 10;
StretchBlt(hDC, nX, nY, bm.bmWidth, bm.bmHeight, hDCMem,
bm.bmWidth - 1, 0,
-bm.bmWidth, bm.bmHeight,
SRCCOPY);
SelectObject(hDCMem, hBitmapOld);
DeleteObject(hDCMem);
ReleaseDC(NULL, hDC);