位图和位块传输(2)压缩拉伸之StretchBlt函数

在BitBlt函数中，目标图像和源图像的大小一样，是因为函数只有两个参数来指定宽和高，如果想要复制是拉伸或压缩图像的大小，可以使用StretchBlt函数

StretchBlt(hdcDst,xDst,yDst,cxDst,cyDst,hdcSrc,xSrc,ySrc,cxSrc,cySrc,dwRop);

下面这个程序展示了一下StretchBlt函数的功能，它把整个客户区填满成系统菜单图标了，改变某些参数的值，可以使得图标上下或左右颠倒

#include<windows.h>

LRESULT CALLBACK WindowProc(
							HWND hwnd,      // handle to window
							UINT uMsg,      // message identifier
							WPARAM wParam,  // first message parameter
							LPARAM lParam   // second message parameter
							);

int WINAPI WinMain(
				   HINSTANCE hInstance,      // handle to current instance
				   HINSTANCE hPrevInstance,  // handle to previous instance
				   LPSTR lpCmdLine,          // command line
				   int nCmdShow              // show state
				   )
{
	static  TCHAR szAppName[]=TEXT("leidemingzi");
	HWND hwnd;
	MSG msg;
	WNDCLASS wndclass;

	wndclass.cbClsExtra=0;
	wndclass.cbWndExtra=0;
	wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
	wndclass.hIcon=LoadIcon(NULL,IDI_ERROR);
	wndclass.hInstance=hInstance;
	wndclass.lpfnWndProc=WindowProc;
	wndclass.lpszClassName=szAppName;
	wndclass.lpszMenuName=NULL;
	wndclass.style=CS_HREDRAW|CS_VREDRAW;

	if(!RegisterClass(&wndclass))
	{
		MessageBox(NULL,TEXT("the program require the windows nt"),TEXT("tips"),MB_ICONERROR);
		return 0;
	}

	hwnd=CreateWindow(
		szAppName,  // registered class name
		TEXT("this is title"), // window name
		WS_OVERLAPPEDWINDOW,        // window style
		CW_USEDEFAULT,                // horizontal position of window
		CW_USEDEFAULT,                // vertical position of window
		CW_USEDEFAULT,           // window width
		CW_USEDEFAULT,          // window height
		NULL,      // handle to parent or owner window
		NULL,          // menu handle or child identifier
		hInstance,  // handle to application instance
		NULL        // window-creation data
		);

	ShowWindow(hwnd,nCmdShow);
	UpdateWindow(hwnd);

	while(GetMessage(&msg,NULL,0,0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	
	return msg.wParam;
}

LRESULT CALLBACK WindowProc(
							HWND hwnd,      // handle to window
							UINT uMsg,      // message identifier
							WPARAM wParam,  // first message parameter
							LPARAM lParam   // second message parameter
							)
{
	static int cxClient,cyClient,cxSource,cySource;
	HDC hdcClient,hdcWindow;
	PAINTSTRUCT ps;


	switch(uMsg)
	{
	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);

	case WM_PAINT:
		hdcClient=BeginPaint(hwnd,&ps);
		hdcWindow=GetWindowDC(hwnd);

		StretchBlt(hdcClient,0,0,cxClient,cyClient,hdcWindow,0,0,cxSource,cySource,MERGECOPY);
		ReleaseDC(hwnd,hdcWindow);
		EndPaint(hwnd,&ps);

		return 0;

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

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