#include <windows.h>
#define NUM 32767
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static int iKeep [NUM][4] ;
HDC hdcScr, hdcMem ;
int cx, cy ;
HBITMAP hBitmap ;
HWND hwnd ;
int i, j, x1, y1, x2, y2 ;
if (LockWindowUpdate (hwnd = GetDesktopWindow ()))
{
hdcScr = GetDCEx (hwnd, NULL, DCX_CACHE | DCX_LOCKWINDOWUPDATE) ;
hdcMem = CreateCompatibleDC (hdcScr) ;
cx = GetSystemMetrics (SM_CXSCREEN) / 10 ;
cy = GetSystemMetrics (SM_CYSCREEN) / 10 ;
hBitmap = CreateCompatibleBitmap (hdcScr, cx, cy) ;
SelectObject (hdcMem, hBitmap) ;
srand ((int) GetCurrentTime ()) ;
for (i = 0 ; i < 2 ; i++)
for (j = 0; j < NUM; j++)
{
LockWindowUpdate(hwnd = GetDesktopWindow());
if (i == 0)
{
iKeep [j] [0] = x1 = cx * (rand () % 10) ;
iKeep [j] [1] = y1 = cy * (rand () % 10) ;
iKeep [j] [2] = x2 = cx * (rand () % 10) ;
iKeep [j] [3] = y2 = cy * (rand () % 10) ;
}
else
{
x1 = iKeep[NUM - 1 - j][0];
y1 = iKeep[NUM - 1 - j][1];
x2 = iKeep[NUM - 1 - j][2];
y2 = iKeep[NUM - 1 - j][3];
}
BitBlt (hdcMem, 0, 0, cx, cy, hdcScr, x1, y1, SRCCOPY) ;
BitBlt (hdcScr, x1, y1, cx, cy, hdcScr, x2, y2, SRCCOPY) ;
BitBlt (hdcScr, x2, y2, cx, cy, hdcMem, 0, 0, SRCCOPY) ;
}
DeleteDC (hdcMem) ;
ReleaseDC (hwnd, hdcScr) ;
DeleteObject (hBitmap) ;
}
return 0;
}
原理: