请教关于图像双缓冲的问题
源代码如下：
#include <windows.h>
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName [] = TEXT ("BitBlt") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_INFORMATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;
if (!RegisterClass (&wndclass))
{
MessageBox (NULL, TEXT ("This program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}
hwnd = CreateWindow (szAppName, TEXT ("BitBlt Demo"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL) ;
ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam)
{
static int cxClient, cyClient, cxSource, cySource ;
HDC hdcClient, hdcWindow ;
int x, y ;
PAINTSTRUCT ps ;
switch (message)
{
case WM_CREATE:
cxSource = GetSystemMetrics (SM_CXSIZEFRAME) +
GetSystemMetrics (SM_CXSIZE) ;
cySource = GetSystemMetrics (SM_CYSIZEFRAME) +
GetSystemMetrics (SM_CYCAPTION) ;
return 0 ;
case WM_SIZE:
cxClient = LOWORD (lParam) ;
cyClient = HIWORD (lParam) ;
return 0 ;
case WM_PAINT:
hdcClient = BeginPaint (hwnd, &ps) ;
RECT r;
r=ps.rcPaint;
HDC hdcMem;
hdcMem = CreateCompatibleDC(hdcClient);
hdcWindow = GetWindowDC (hwnd) ;
for (y = 0 ; y < cyClient ; y += cySource)
for (x = 0 ; x < cxClient ; x += cxSource)
{
BitBlt (hdcMem, x, y, cxSource, cySource,
hdcWindow, 0, 0, SRCCOPY) ;
}
[b]//这一段是另外加上去的，但是就是这一段导致图像显示不出来
BitBlt(hdcClient,
r.left,
r.top,
r.right-r.left,
r.bottom-r.top,
hdcMem,
0,
0,
SRCCOPY);
//请教这是为什么？[/b][b][/b][color=#FF0000][/color]ReleaseDC (hwnd, hdcWindow) ;
EndPaint (hwnd, &ps) ;
return 0 ;
case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}
[解决办法]
CPaintDC dc(this);
CDC MemDC;
CRect rect;
CBitmap MemBitmap;
GetClientRect(rect);
MemDC.CreateCompatibleDC(&dc);
MemBitmap.CreateCompatibleBitmap(&dc,rect.Width(),rect.Height());
CBitmap* pOldBitmap=MemDC.SelectObject(&MemBitmap);
MemDC.FillSolidRect(rect,RGB(50,120,100));
dc.BitBlt(0,0,rect.Width(),rect.Height(),&MemDC,0,0,SRCCOPY);
MemDC.SelectObject(pOldBitmap);
MemBitmap.DeleteObject();
MemDC.DeleteDC();
[解决办法]
看看MSDN吧，MSDN上描述的很清楚，你建立一个兼容的DC之后，还要为这个DC创建一个兼容的画布，即BITMAP，
3楼已经写的很清楚了。
我在给你一段代码吧。
你创建个800x480的窗口就好了。
想改变窗口显示，往pBuffer里写值就好了。
gMainWnd == 你的hwnd,
unsigned short pBuffer[800*480] = {0};
HDC dc = GetWindowDC(gMainWnd);
HDC MemDc = CreateCompatibleDC(dc);
HBITMAP hBitmap = CreateBitmap(800,480,1,16,pBuffer);
HBITMAP hOldBitmap = (HBITMAP)SelectObject(MemDc,hBitmap);
BitBlt(dc,0,0,800,480,MemDc,0,0,SRCCOPY);
SelectObject(MemDc, hOldBitmap);
DeleteDC(MemDc);
ReleaseDC(gMainWnd, dc);
DeleteObject(hBitmap);
