GetDIBits返回兼容位图的无效颜色数组

Question

我试图通过GetDIBits从兼容的位图(它完全由RGB(0,0,255)颜色填充)中获取像素数组，但它返回了另一种颜色。而且，当我试图改变一个数组时，它实际上返回了一个异常。怎么啦？

case WM_PAINT:
{
    PAINTSTRUCT ps;
    HDC hdc = BeginPaint(hwnd, &ps);
    HBRUSH hb = CreateSolidBrush(RGB(0, 0, 255));

    HDC hdcc = CreateCompatibleDC(hdc);
    HBITMAP bm = CreateCompatibleBitmap(hdc, r.right, r.bottom);

    SelectObject(hdcc, bm);
    SelectObject(hdcc, hb);

    Rectangle(hdcc, 0, 0, r.right, r.bottom); //filling by the blue brush

    BITMAPINFO bi = { 0 };

    bi.bmiHeader.biSize = sizeof(bi.bmiHeader);

    int er = GetDIBits(hdcc, bm, 0, 0, NULL, &bi, DIB_RGB_COLORS);
    //In GetDIBits, as HDC argument must be compatible, yes?

    if (!er)
    {
        cout << "ERROR HERE:"<< GetLastError()<<"ENDS";
    }

    COLORREF *buf = new COLORREF(bi.bmiHeader.biSizeImage); //Yet, still, I have not understood, which type array should be - char, BYTE, COLORREF or anything else

    bi.bmiHeader.biBitCount = 32;
    bi.bmiHeader.biCompression = BI_RGB;
    bi.bmiHeader.biHeight = abs(bi.bmiHeader.biHeight);

    GetDIBits(hdcc, bm, 0, bi.bmiHeader.biHeight, buf, &bi, DIB_RGB_COLORS);

    for (int i(0); i < 100; i++)
    {
        cout << (int)GetRValue(buf[i]) << ",";
        cout << (int)GetGValue(buf[i]) << ",";
        cout << (int)GetBValue(buf[i]) << ",";
        cout << endl;
    }

    SetDIBits(hdcc, bm, 0, bi.bmiHeader.biHeight, buf, &bi, DIB_RGB_COLORS);

    delete []buf;

    BitBlt(hdc, 0, 0, r.right, r.bottom, hdcc, 0, 0, SRCCOPY);

    DeleteObject(hb);
    DeleteDC(hdcc);
    DeleteObject(bm);

    EndPaint(hwnd, &ps);
}
break;

enter image description here

Answer 1

这一行有几个问题：

COLORREF *buf = new COLORREF(bi.bmiHeader.biSizeImage);

正如@PaulMcKenzie指出的那样，你的意思是使用方括号而不是圆括号，这样你为array.

• biSizeImage分配的空间是以字节为单位的，而不是COLORREFs，所以这个over-allocates.

• biSizeImage可能是零，在这种情况下你什么都不会分配。当biSizeImage为零时，意味着您必须计算程序中这一点的实际大小，biSizeImage是设备相关(“兼容”)位图的大小，它很可能与您试图获取的设备无关数据所需的大小不同。