//暴力匹配方式，在k2中找到k1的最佳匹配，hamming距离
// k1查询特征点，k2数据库特征点
int BruteForceMatch(const KeypointWithDesc& k1,
const std::vector<KeypointWithDesc>&k2, int*dist)
{
unsigned int distance[3] = { DESCRIPTOR_LENGTH * 8, DESCRIPTOR_LENGTH * 8, DESCRIPTOR_LENGTH * 8 };
//最小距离， 次小距离，当前距离
unsigned int index[3] = { 0 };
unsigned short temp = 0;
for (int i = 0; i < k2.size(); ++i)
{
distance[2] = 0;
for (int j = 0; j < DESCRIPTOR_LENGTH/2; ++j)
{
//异或求海明距离
temp = k1.m_d[j+1] ^ k2[i].m_d[j+1];
temp = (temp << 8) | (k1.m_d[j] ^ k2[i].m_d[j]);
distance[2] += __popcnt16(temp);
}
if (distance[2] < distance[1]){
distance[1] = distance[2];
index[1] = i;
if (distance[1] <= distance[0]){
distance[2] = distance[0];
distance[0] = distance[1];
distance[1] = distance[2];
index[2] = index[0];
index[0] = index[1];
index[1] = index[2];
}
}
}
dist[0] = distance[0];
dist[1] = distance[1];
return index[0];
}
static inline int
popcnt(std::uint16_t n)
{
return __popcnt16(n);
}
