I've used the function available on WinExtras to convert from an HBitmap to a QImage, however the image that is returned is different from the original HBitmap.

Investigating a little bit I found the reason of this issue: The format of the QImage used internally by Qt, the value used is: Format_ARGB32_Premultiplied, but to correctly convert my image I implemented this function but using the QImage::Format_RGB32.

I belive the solution is give a option to set the format of the output QImage.

I've atttached a example that reproduces the error, and a possible solution.

I've attached two images that show the difference between the Qt function to convert HBitmap to QImage and the function that I proposed. I can reproduce these problem more emphatically on Windows 7 with basic theme (not aero), as you can see those images are from Windows 7 with basic theme.

Final solution that I propose:

 
QImage imageFromHBITMAP_Improved(HDC hdc, HBITMAP bitmap, QImage::Format format)
{
    BITMAPINFO bmi = {0};
    bmi.bmiHeader.biSize = sizeof(bmi.bmiHeader);

    // Get the BITMAPINFO structure from the bitmap
    if(!GetDIBits(hdc, bitmap, 0, 0, NULL, &bmi, DIB_RGB_COLORS)){
        qErrnoWarning("%s: failed to get bitmap info", __FUNCTION__);
        return QImage();
    }

    // Get bitmap bits
    QScopedArrayPointer<uchar> data(new uchar [bmi.bmiHeader.biSizeImage]);

    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = BI_RGB;

    if(!GetDIBits(hdc, bitmap, 0, bmi.bmiHeader.biHeight, data.data(), &bmi, DIB_RGB_COLORS)){
        qErrnoWarning("%s: failed to get bitmap bits", __FUNCTION__);
        return QImage();
    }

    int w = bmi.bmiHeader.biWidth;
    int h = bmi.bmiHeader.biHeight;

    return QImage(data.data(), w, h, format).mirrored();
}