win32

void WINAPI CaptureScreenIntoFile()
{
    BITMAPFILEHEADER bfHeader;
    BITMAPINFOHEADER biHeader;
    HGDIOBJ hTempBitmap;
    HBITMAP hBitmap;
    BITMAP bAllDesktops;
    HDC hDC, hMemDC;
    LONG lWidth, lHeight;

    ZeroMemory(&bfHeader, sizeof(BITMAPFILEHEADER));
    ZeroMemory(&biHeader, sizeof(BITMAPFILEHEADER));
    ZeroMemory(&bAllDesktops, sizeof(BITMAP));

    hDC = GetDC(NULL);
    hTempBitmap = GetCurrentObject(hDC, OBJ_BITMAP);
    GetObjectW(hTempBitmap, sizeof(BITMAP), &bAllDesktops);

    lWidth = bAllDesktops.bmWidth;
    lHeight = bAllDesktops.bmHeight;

    DeleteObject(hTempBitmap);

    bfHeader.bfType = (WORD)('B' | ('M' << 8));
    bfHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    biHeader.biSize = sizeof(BITMAPINFOHEADER);
    biHeader.biBitCount = 24;
    biHeader.biCompression = BI_RGB;
    biHeader.biPlanes = 1;
    biHeader.biWidth = lWidth;
    biHeader.biHeight = lHeight;
    biHeader.biSizeImage = 0;

    DWORD screen_bytes_size = (((24 * lWidth + 31) & ~31) / 8) * lHeight;

    hMemDC = CreateCompatibleDC(hDC);
    HBITMAP hbmScreen = CreateCompatibleBitmap(hDC, lWidth, lHeight);
    SelectObject(hMemDC, hbmScreen);

    int x = GetSystemMetrics(SM_XVIRTUALSCREEN);
    int y = GetSystemMetrics(SM_YVIRTUALSCREEN);
    BitBlt(hMemDC, 0, 0, lWidth, lHeight, hDC, x, y, SRCCOPY);

    HANDLE hDIB = GlobalAlloc(GHND, screen_bytes_size);
    char *lpbitmap = (char *)GlobalLock(hDIB);
    GetDIBits(hDC, hbmScreen, 0,
        (UINT)lHeight,
        lpbitmap,
        (BITMAPINFO *)&biHeader, DIB_RGB_COLORS);

    HANDLE hFile = CreateFile("12.bmp",
        GENERIC_WRITE,
        0,
        NULL,
        CREATE_ALWAYS,
        FILE_ATTRIBUTE_NORMAL, NULL);

    // Add the size of the headers to the size of the bitmap to get the total file size
    DWORD dwSizeofDIB = screen_bytes_size + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bfHeader.bfSize = dwSizeofDIB;

    DWORD dwBytesWritten = 0;
    WriteFile(hFile, (LPSTR)&bfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
    WriteFile(hFile, (LPSTR)&biHeader, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
    WriteFile(hFile, (LPSTR)lpbitmap, screen_bytes_size, &dwBytesWritten, NULL);

    DeleteDC(hMemDC);
    ReleaseDC(NULL, hDC);
    DeleteObject(hbmScreen);
}

更新： 

如果我们想把图形的信息存放到数组里面，则可以使用下面的代码。

#include <Windows.h>
#include <algorithm>

int main()
{
    BITMAPFILEHEADER bfHeader;
    BITMAPINFOHEADER biHeader;
    BITMAPINFO bInfo;
    HGDIOBJ hTempBitmap;
    HBITMAP hBitmap;
    BITMAP bAllDesktops;
    HDC hDC, hMemDC;
    LONG lWidth, lHeight;
    BYTE* sb = NULL;
    DWORD screen_bytes_size = 0;

    ZeroMemory(&bfHeader, sizeof(BITMAPFILEHEADER));
    ZeroMemory(&biHeader, sizeof(BITMAPFILEHEADER));
    ZeroMemory(&bInfo, sizeof(BITMAPINFO));
    ZeroMemory(&bAllDesktops, sizeof(BITMAP));

    hDC = GetDC(NULL);
    hTempBitmap = GetCurrentObject(hDC, OBJ_BITMAP);
    GetObjectW(hTempBitmap, sizeof(BITMAP), &bAllDesktops);

    lWidth = bAllDesktops.bmWidth;
    lHeight = bAllDesktops.bmHeight;

    DeleteObject(hTempBitmap);

    bfHeader.bfType = (WORD)('B' | ('M' << 8));
    bfHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    biHeader.biSize = sizeof(BITMAPINFOHEADER);
    biHeader.biBitCount = 24;
    biHeader.biCompression = BI_RGB;
    biHeader.biPlanes = 1;
    biHeader.biWidth = lWidth;
    biHeader.biHeight = lHeight;

    bInfo.bmiHeader = biHeader;

    screen_bytes_size = (((24 * lWidth + 31) & ~31) / 8) * lHeight;

    hMemDC = CreateCompatibleDC(hDC);
    hBitmap = CreateDIBSection(hDC, &bInfo, DIB_RGB_COLORS, (VOID**)&sb, NULL, 0);
    SelectObject(hMemDC, hBitmap);

    int x = GetSystemMetrics(SM_XVIRTUALSCREEN);
    int y = GetSystemMetrics(SM_YVIRTUALSCREEN);
    BitBlt(hMemDC, 0, 0, lWidth, lHeight, hDC, x, y, SRCCOPY);

    // Need to also copy bfHeader & biHeader bytes somehow...
    BYTE *screen_bytes = new BYTE[sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + screen_bytes_size];
    int size = sizeof(BITMAPFILEHEADER);
    std::copy(&bfHeader, &bfHeader + 1 , (BITMAPFILEHEADER*)screen_bytes); //&bfHeader + 1是指偏移一个BITMAPFILEHEADER结构体大小=》14
    std::copy(&biHeader, &biHeader + 1, (BITMAPINFOHEADER*)(screen_bytes + sizeof(BITMAPFILEHEADER)));
    std::copy(sb, sb + screen_bytes_size, screen_bytes + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER));
 //   std::copy(sb, sb + screen_bytes_size, screen_bytes);

    DeleteDC(hMemDC);
    ReleaseDC(NULL, hDC);
    DeleteObject(hBitmap);

    return 0;
}

链接： How do I get the byte representation of a BITMAPFILEHEADER and BITMAPINFOHEADER?