cvRound精度

cvRound和round的结果不一样

	int r1 = 630.5000000000000 + 0.5;   //631
	int r2 = lround(630.5000000000000);  //631
	int rr = cvRound(630.5000000000000);  //630

cvRound源码：

CV_INLINE int
cvRound( double value )
{
#if ((defined _MSC_VER && defined _M_X64) || (defined __GNUC__ && defined __x86_64__ \
    && defined __SSE2__ && !defined __APPLE__)) && !defined(__CUDACC__)
    __m128d t = _mm_set_sd( value );
    return _mm_cvtsd_si32(t);
#elif defined _MSC_VER && defined _M_IX86
    int t;
    __asm
    {
        fld value;
        fistp t;
    }
    return t;
#elif ((defined _MSC_VER && defined _M_ARM) || defined CV_ICC || \
        defined __GNUC__) && defined HAVE_TEGRA_OPTIMIZATION
    TEGRA_ROUND_DBL(value);
#elif defined CV_ICC || defined __GNUC__
# if CV_VFP
    ARM_ROUND_DBL(value);
# else
    return (int)lrint(value);
# endif
#else
    /* it's ok if round does not comply with IEEE754 standard;
       the tests should allow +/-1 difference when the tested functions use round */
    return (int)(value + (value >= 0 ? 0.5 : -0.5));
#endif
}

_mm_cvtsd_si32是比0.5大才向上取整，等于0.5时向下取整