SDK截图程序（一）

#include <windows.h>
#pragma comment(linker,"/subsystem:\"windows\"" )
HBITMAP GetBitmap();

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 HDC         hdcClient, hdcWindow ;
static HDC hdcMem;
HBITMAP hBitmap;
PAINTSTRUCT ps ;

switch (message)
{
case WM_CREATE:
{
hdcClient=GetDC(hwnd);   //获得应用程序客户区窗口句柄
hdcWindow = GetWindowDC (NULL) ;  //GetWindowDC可以获得整个应用程序窗口句柄（客户区和非客户区）
//当参数传值为NULL的时候，得到系统窗口的句柄
hBitmap=CreateCompatibleBitmap(hdcClient,100,100);   //创建与设备兼容的位图，宽100像素，高100像素
hdcMem=CreateCompatibleDC(hdcClient);                //创建内存设备环境句柄
SelectObject(hdcMem,hBitmap);                        //将位图选进内存设备环境

BitBlt (hdcMem, 0, 0, 100,100,  hdcWindow, 0, 0, SRCCOPY) ;   //将系统窗口左上角100*100的图像像素复制到内存设备环境

OpenClipboard( hwnd ) ;   //打开粘贴板
EmptyClipboard() ;        //清空粘贴板
SetClipboardData( CF_BITMAP, hBitmap ) ;   //设置粘贴板数据，即将位图设置进粘贴

//之前有将新建的位图选进内存设备环境，后来将系统窗口100*100像素图像复制移动到内存
//设备环境。我的理解是，将位图选进内存设备环境之后，针对内存设备环境的操作，改变了
//位图的内容，而不需要再将内存设备环境选进位图了

CloseClipboard() ;       //关闭粘贴板
ReleaseDC (hwnd, hdcWindow) ;
return 0 ;
}

case WM_SIZE:

return 0 ;

case WM_PAINT:
hdcClient=BeginPaint (hwnd, &ps) ;
BitBlt (hdcClient, 0, 0, 100,100,  hdcMem, 0, 0, SRCCOPY) ;  //这里我们做一个小测试，将截取的图片显示在客户区
//这样需要将hdcClient和hdcMem定义成static的
EndPaint (hwnd, &ps) ;
return 0 ;

case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}

return DefWindowProc (hwnd, message, wParam, lParam) ;
}