winapi - CreateDIBSection + 16 位系统颜色

Question

此代码适用于 32 位系统颜色（Windows 7），但不适用于 16 位颜色 - 菜单位图不透明！！！：

...
HBITMAP rv = rgb(hsrc, 16);
...

HBITMAP rgb(HBITMAP hsrc, WORD wBitsPixel) {

    HBITMAP hold = NULL;
    HDC hdcsrc = NULL, hdc = NULL;
    BITMAP bmp = {0};
    HBITMAP dib = NULL;
    UCHAR *dst = NULL, *src = NULL, *tmp = NULL;
    UCHAR alpha;
    int bpl;
    ULONG x, y;
    DWORD bmp_size = 0;
    HANDLE hdib = NULL;
    char *lpbitmap = NULL;
    int rv = 0;


    hdc    = GetDC(m_hMainDlg);
    hdcsrc = CreateCompatibleDC(hdc);
    hold   = (HBITMAP)SelectObject(hdcsrc, hsrc);
    rv     = GetObject(hsrc, sizeof(BITMAP), &bmp);

    BITMAPINFOHEADER bi = {0};
    bi.biSize          = sizeof(BITMAPINFOHEADER);
    bi.biWidth         = bmp.bmWidth;;
    bi.biHeight        = bmp.bmHeight;
    bi.biPlanes        = 1;
    bi.biBitCount      = wBitsPixel;
    bi.biCompression   = BI_RGB;
    bi.biSizeImage     = 0;
    bi.biXPelsPerMeter = 0;
    bi.biYPelsPerMeter = 0;
    bi.biClrUsed       = 0;
    bi.biClrImportant  = 0;

    bmp_size = ((bmp.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmp.bmHeight;
    hdib = GlobalAlloc(GHND, bmp_size);

    lpbitmap = (char *)GlobalLock(hdib);

    /* Get bits of source bitmap. */
    GetDIBits(hdcsrc, hsrc, 0, bmp.bmHeight, lpbitmap, (BITMAPINFO *)&bi, DIB_RGB_COLORS);

    /* For destination bitmap */
    BITMAPINFO bmi = {0};
    bmi.bmiHeader.biSize          = sizeof(BITMAPINFO);
    bmi.bmiHeader.biWidth         = bmp.bmWidth;
    bmi.bmiHeader.biHeight        = bmp.bmHeight;
    bmi.bmiHeader.biPlanes        = 1;
    bmi.bmiHeader.biBitCount      = wBitsPixel;
    bmi.bmiHeader.biCompression   = BI_RGB;
    bmi.bmiHeader.biSizeImage     = 0;
    bmi.bmiHeader.biXPelsPerMeter = 0;
    bmi.bmiHeader.biYPelsPerMeter = 0;
    bmi.bmiHeader.biClrUsed       = 0;
    bmi.bmiHeader.biClrImportant  = 0;

    dib = CreateDIBSection(NULL, &bmi, DIB_RGB_COLORS, (void **)&dst, NULL, 0);

    bpl = 4 * bmp.bmWidth; /* bytes per line */
    src = (UCHAR *)lpbitmap;
    for (y = 0; y < bmp.bmHeight; y++, src += bpl) {
        tmp = src;
        for (x = 0; x < bmp.bmWidth; x++) {
            alpha  = tmp[3];

            dst[0] = tmp[0] * alpha / 255;
            dst[1] = tmp[1] * alpha / 255;
            dst[2] = tmp[2] * alpha / 255;
            dst[3] = alpha;

            dst += 4;
            tmp += 4;
        }
    }

    // free resources
    ReleaseDC(m_hMainDlg, hdc);
    SelectObject(hdcsrc, hold);
    DeleteDC(hdcsrc);
    GlobalUnlock(hdib);
    GlobalFree(hdib);

    return dib;
}