最近在查閱ORB演算法的相關資料，其中涉及到求兩個01字串間的hamming距離，作為度量兩個向量距離的值。在opencv庫中有結構體HammingLUT，來看看它的定義：

struct CV_EXPORTS Hamming
{
    enum { normType = NORM_HAMMING };
    typedef unsigned char ValueType;
    typedef int ResultType;

    /** this will count the bits in a ^ b
     */
    ResultType operator()( const unsigned char* a, const unsigned char* b, int size ) const
    {
        return normHamming(a, b, size);
    }
};

typedef Hamming HammingLUT;
 

	HammingLUT lut;
	unsigned int result;
	result = lut((a), (b), size);

result = lut((a), (b), 1);
result = lut((a), (b), 2);
result = lut((a), (b), 3);

所以我自己也簡單寫了一個小函式HammingDist

//計算hamming距離
int HammingDis(unsigned char *s1, unsigned char *s2, int size)
{
	int i, temp, num, dis=0;
	for (i = 0; i < size; i++)
	{
		num = 0;
		temp = s1[i] ^ s2[i];
		while (temp)//按位統計1的數量
		{
			if (temp % 2)num++;
			temp /= 2;
		}
		dis += num;
	}
	return dis;
}