CaptureScreenToBitmap

Macht einen Schnappschuss des Bildschirminhalts und speichert ihn in ein BMP-Bild. Die Funktion ist simpel, zuerst wird der Bildschirminhalt in einen Compatible Memory DC kopiert, anschließend die Daten in eine Bitmap-Struktur konvertiert und zum Schluss alles in die BMP-Datei geschrieben. Der String-Parameter gibt den Dateinamen an, unter dem das Bild gespeichert werden soll. Bei Erfolg liefert die Funktion 1 zurück, sonst 0.

/*

Make a screenshot and save it to a BMP image



Sources:

1) MSDN index["bitmaps [Win32]", "code examples"]->"Capturing an image"

2) MSDN index["bitmaps [Win32]", "code examples"]->"Storing an image"





*/



int CaptureBMP(LPCTSTR szFile)

{

    // Source[1]

    HDC hdcScr, hdcMem;

    HBITMAP hbmScr;

    BITMAP bmp;

    int iXRes, iYRes;



    // Create a normal DC and a memory DC for the entire screen. The

    // normal DC provides a "snapshot" of the screen contents. The

    // memory DC keeps a copy of this "snapshot" in the associated

    // bitmap.

    hdcScr = CreateDC("DISPLAY", NULL, NULL, NULL);

    hdcMem = CreateCompatibleDC(hdcScr);



    iXRes = GetDeviceCaps(hdcScr, HORZRES);

    iYRes = GetDeviceCaps(hdcScr, VERTRES);



    // Create a compatible bitmap for hdcScreen.

    hbmScr = CreateCompatibleBitmap(hdcScr, iXRes, iYRes);

    if (hbmScr == 0) return 0;



    // Select the bitmaps into the compatible DC.

    if (!SelectObject(hdcMem, hbmScr)) return 0;



    // Copy color data for the entire display into a

    // bitmap that is selected into a compatible DC.

    if (!StretchBlt(hdcMem,

        0, 0, iXRes, iYRes,

        hdcScr,

        0, 0, iXRes, iYRes,

        SRCCOPY))



        return 0;



    // Source[2]

    PBITMAPINFO pbmi;

    WORD cClrBits;



    // Retrieve the bitmap's color format, width, and height.

    if (!GetObject(hbmScr, sizeof(BITMAP), (LPSTR) &bmp)) return 0;



    // Convert the color format to a count of bits.

    cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);

    if (cClrBits == 1)

        cClrBits = 1;

    else if (cClrBits <= 4)

        cClrBits = 4;

    else if (cClrBits <= 8)

        cClrBits = 8;

    else if (cClrBits <= 16)

        cClrBits = 16;

    else if (cClrBits <= 24)

        cClrBits = 24;

    else cClrBits = 32;



    // Allocate memory for the BITMAPINFO structure. (This structure

    // contains a BITMAPINFOHEADER structure and an array of RGBQUAD

    // data structures.)

    if (cClrBits != 24)

        pbmi = (PBITMAPINFO) LocalAlloc(LPTR,

                sizeof(BITMAPINFOHEADER) +

                sizeof(RGBQUAD) * (1 << cClrBits));



    // There is no RGBQUAD array for the 24-bit-per-pixel format.

    else

        pbmi = (PBITMAPINFO) LocalAlloc(LPTR,

                sizeof(BITMAPINFOHEADER));



    // Initialize the fields in the BITMAPINFO structure.

    pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);

    pbmi->bmiHeader.biWidth = bmp.bmWidth;

    pbmi->bmiHeader.biHeight = bmp.bmHeight;

    pbmi->bmiHeader.biPlanes = bmp.bmPlanes;

    pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;

    if (cClrBits < 24)

        pbmi->bmiHeader.biClrUsed = (1 << cClrBits);



    // If the bitmap is not compressed, set the BI_RGB flag.

    pbmi->bmiHeader.biCompression = BI_RGB;



    // Compute the number of bytes in the array of color

    // indices and store the result in biSizeImage.

    pbmi->bmiHeader.biSizeImage = (pbmi->bmiHeader.biWidth + 7) / 8

                                    * pbmi->bmiHeader.biHeight * cClrBits;



    // Set biClrImportant to 0, indicating that all of the

    // device colors are important.

    pbmi->bmiHeader.biClrImportant = 0;



    HANDLE hf;                  // file handle

    BITMAPFILEHEADER hdr;       // bitmap file-header

    PBITMAPINFOHEADER pbih;     // bitmap info-header

    LPBYTE lpBits;              // memory pointer

    DWORD dwTotal;              // total count of bytes

    DWORD CB ;                   // incremental count of bytes

    BYTE *hp;                   // byte pointer

    DWORD dwTmp;



    pbih = (PBITMAPINFOHEADER) pbmi;

    lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);



    if (!lpBits) return 0;



    // Retrieve the color table (RGBQUAD array) and the bits

    // (array of palette indices) from the DIB.

    if (!GetDIBits(hdcMem, hbmScr, 0, (WORD) pbih->biHeight, lpBits, pbmi, DIB_RGB_COLORS)) return 0;



    // Create the .BMP file.

    hf = CreateFile(szFile,

                    GENERIC_READ | GENERIC_WRITE,

                    (DWORD) 0,

                    NULL,

                    CREATE_ALWAYS,

                    FILE_ATTRIBUTE_NORMAL,

                    (HANDLE) NULL);

    if (hf == INVALID_HANDLE_VALUE) return 0;



    hdr.bfType = 0x4d42;        // 0x42 = "B" 0x4d = "M"



    // Compute the size of the entire file.

    hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +

                 pbih->biSize + pbih->biClrUsed *

                 sizeof(RGBQUAD) + pbih->biSizeImage);

    hdr.bfReserved1 = 0;

    hdr.bfReserved2 = 0;



    // Compute the offset to the array of color indices.

    hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +

                    pbih->biSize + pbih->biClrUsed *

                    sizeof (RGBQUAD);



    // Copy the BITMAPFILEHEADER into the .BMP file.

    if (!WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER), (LPDWORD) &dwTmp, NULL)) return 0;



    // Copy the BITMAPINFOHEADER and RGBQUAD array into the file.

    if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)

                + pbih->biClrUsed * sizeof (RGBQUAD),

                (LPDWORD) &dwTmp, NULL))

        return 0;



    // Copy the array of color indices into the .BMP file.

    dwTotal = CB  = pbih->biSizeImage;

    hp = lpBits;

    if (!WriteFile(hf, (LPSTR) hp, (int) CB , (LPDWORD) &dwTmp, NULL)) return 0;



    // Close the .BMP file.

    if (!CloseHandle(hf)) return 0;



    // Free memory.

    GlobalFree((HGLOBAL)lpBits);

    ReleaseDC(0, hdcScr);

    ReleaseDC(0, hdcMem);



    return 1;

}