BitBlt与StretchBlt应用实例

此程序来源《windows程序设计》，挺不错的：

源代码：

#include <windows.h>
#include "resource.h"
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,
                 HINSTANCE hPrevInstance,
                 PSTR szCmdLine,
                 int iCmdShow) {
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;
    static TCHAR szAppName[] = TEXT("XZZ");
    
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = szAppName;
    wndclass.lpszClassName = szAppName;
    
    if(!RegisterClass(&wndclass)) {
        MessageBox(NULL, TEXT("Register failure..."),
            szAppName, MB_ICONERROR);
        return 0;
    }
    
    hwnd = CreateWindow(szAppName,
        szAppName,
        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 HBITMAP hBitmap;
    static HDC hdcMem;
    HDC hdc;
    int x, y;
    static int cxBitmap, cyBitmap, cxClient, cyClient, iSize = ID_BIG;
    PAINTSTRUCT ps;
    static PTSTR pText = TEXT("hello, world");
    SIZE size;
    HMENU hMenu;

    switch(message) {
    case WM_CREATE:
        hdc = GetDC(hwnd);
        hdcMem = CreateCompatibleDC(hdc);
        GetTextExtentPoint32(hdc, pText, lstrlen(pText), &size);
        cxBitmap = size.cx;
        cyBitmap = size.cy;
        /*
         * 创建兼容位图， 选进内存设备， 在内存设备上画图
         */
        hBitmap = CreateCompatibleBitmap(hdc, cxBitmap, cyBitmap);
        SelectObject(hdcMem, hBitmap);
        TextOut(hdcMem, 0, 0, pText, lstrlen(pText));
        ReleaseDC(hwnd, hdc);
        return 0;

    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        return 0;

    case WM_COMMAND:
        hMenu = GetMenu(hwnd);
        switch(LOWORD(wParam)) {
        case ID_SMALL:
            CheckMenuItem(hMenu, iSize, MF_UNCHECKED);
            iSize = LOWORD(wParam);
            CheckMenuItem(hMenu, iSize, MF_CHECKED);
            InvalidateRect(hwnd, NULL, TRUE);
            return 0;
        case ID_BIG:
            CheckMenuItem(hMenu, iSize, MF_UNCHECKED);
            iSize = LOWORD(wParam);
            CheckMenuItem(hMenu, iSize, MF_CHECKED);
            InvalidateRect(hwnd, NULL, TRUE);
            return 0;
        }
        return 0;

        case WM_PAINT:
            hdc = BeginPaint(hwnd, &ps);
            switch(iSize) {
            case ID_BIG:
                StretchBlt(hdc, 0, 0, cxClient, cyClient, hdcMem, 0, 0,
                    cxBitmap, cyBitmap, SRCCOPY);
                break;
            case ID_SMALL:
                BitBlt(hdc, cxClient / 2, cyClient / 2, cxBitmap,
                    cyBitmap, hdcMem, 0, 0, SRCCOPY);
                break;
            }
            EndPaint(hwnd, &ps);
            return 0;

            case WM_DESTROY:
                DeleteDC(hdcMem);
                DeleteObject(hBitmap);
                PostQuitMessage(0);
                return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}