VC++ 螢幕截圖完整實現：CopyScreenToBitmap + SaveBitmapToFile 雙函式詳解與實戰調用

一、 核心流程

1. CopyScreenToBitmap(RECT*)：建立螢幕 DC → 相容記憶體 DC → 建立相容位圖 → BitBlt 複製螢幕像素 → 回傳 HBITMAP。
2. SaveBitmapToFile(HBITMAP, filename)：取得位圖屬性 → 建構 BITMAPINFOHEADER → 計算對齊掃描行大小 → 分配全域記憶體 → GetDIBits 取像素資料 (含調色盤處理) → 寫入 BMP 檔案頭 + 資訊頭 + 像素資料。

二、 關鍵函式完整代碼 (精簡註解版)

1. 螢幕區域 → HBITMAP

HBITMAP CopyScreenToBitmap(LPRECT lpRect) {
    if (IsRectEmpty(lpRect)) return NULL;

    HDC hScrDC = CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
    HDC hMemDC = CreateCompatibleDC(hScrDC);

    int nX = lpRect->left, nY = lpRect->top;
    int nX2 = lpRect->right, nY2 = lpRect->bottom;
    int nWidth = nX2 - nX, nHeight = nY2 - nY;

    HBITMAP hBitmap = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);
    HBITMAP hOld = (HBITMAP)SelectObject(hMemDC, hBitmap);

    BitBlt(hMemDC, 0, 0, nWidth, nHeight, hScrDC, nX, nY, SRCCOPY);

    hBitmap = (HBITMAP)SelectObject(hMemDC, hOld); // 取回新位圖句柄
    DeleteDC(hScrDC); DeleteDC(hMemDC);
    return hBitmap; // 呼叫端負責 DeleteObject
}

2. HBITMAP → .bmp 檔案

BOOL SaveBitmapToFile(HBITMAP hBitmap, LPCTSTR szFile) {
    BITMAP bm; GetObject(hBitmap, sizeof(bm), &bm);

    // 1. 計算位元深度與調色盤
    HDC hDC = CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
    int bits = GetDeviceCaps(hDC, BITSPIXEL) * GetDeviceCaps(hDC, PLANES);
    DeleteDC(hDC);
    WORD wBitCount = (bits<=1)?1:(bits<=4)?4:(bits<=8)?8:(bits<=24)?24:32;
    DWORD dwPaletteSize = (wBitCount<=8) ? (1<

// 1. 截取當前視窗
CRect rect; GetWindowRect(&rect);
HBITMAP hBmp = CopyScreenToBitmap(&rect);
SaveBitmapToFile(hBmp, _T("C:\\WindowCapture.bmp"));
DeleteObject(hBmp);

// 2. 全螢幕截圖
CRect scr;
scr.SetRect(0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN));
HBITMAP hBmp2 = CopyScreenToBitmap(&scr);
SaveBitmapToFile(hBmp2, _T("C:\\FullScreen.bmp"));
DeleteObject(hBmp2);