// Build a kd-tree from a list of elements. All elements must implement
// the IKDTreeDomain interface and must have the same dimensionality.
KDTree* KDTree_CreateKDTree (ArrayList* exset)
{
if (ArrayList_Count(exset) == 0)
return (NULL);
KDTree* cur = KDTree_new0 ();
cur->dr = KDTree_GoodCandidate (exset, &cur->splitDim);
ArrayList* leftElems = ArrayList_new0 (NULL);
ArrayList* rightElems = ArrayList_new0 (NULL);
// split the exemplar set into left/right elements relative to the
// splitting dimension
double bound = IKDTreeDomain_GetDimensionElement (cur->dr, cur->splitDim);
int i;
for(i=0; i<ArrayList_Count(exset); i++) {
IKDTreeDomain* dom = (IKDTreeDomain*) ArrayList_GetItem(exset, i);
// ignore the current element
if (dom == cur->dr)
continue;
if (IKDTreeDomain_GetDimensionElement (dom, cur->splitDim) <= bound) {
ArrayList_AddItem(leftElems, dom);
} else {
ArrayList_AddItem(rightElems, dom);
}
}
// recurse
cur->left = KDTree_CreateKDTree (leftElems);
cur->right = KDTree_CreateKDTree (rightElems);
ArrayList_delete(leftElems);
ArrayList_delete(rightElems);
return (cur);
}
ArrayList* MatchKeys_FindMatchesBBF (ArrayList* keys1, ArrayList* keys2)
{
// TODO: swap so smaller list is searched.
ArrayList* al = ArrayList_new0 (NULL);
int i;
for (i=0; i<ArrayList_Count(keys2); i++)
ArrayList_AddItem (al, ArrayList_GetItem(keys2, i));
KDTree* kd = KDTree_CreateKDTree (al);
ArrayList_delete(al);
ArrayList* matches = ArrayList_new0 (Match_delete);
int j;
for (j=0; j<ArrayList_Count(keys1); j++) {
KeypointN* kp = (KeypointN*) ArrayList_GetItem(keys1, j);
ArrayList* kpNNList = (ArrayList*)KDTree_NearestNeighbourListBBF (kd, (IKDTreeDomain*)kp, 2, 40);
if (ArrayList_Count(kpNNList) < 2)
FatalError ("BUG: less than two neighbours!");
KDTreeBestEntry* be1 = (KDTreeBestEntry*) ArrayList_GetItem(kpNNList, 0);
KDTreeBestEntry* be2 = (KDTreeBestEntry*) ArrayList_GetItem(kpNNList, 1);
if ((be1->distance / be2->distance) > 0.6)
continue;
KeypointN* kpN = (KeypointN*)KDTreeBestEntry_Neighbour(be1);
ArrayList_AddItem(matches, Match_new (kp, kpN, be1->distance, be2->distance));
/*
WriteLine ("(%d,%d) (%d,%d) %d, 2nd: %d", (int)(kp->x + 0.5),
(int)(kp->y + 0.5), (int)(kpN->x + 0.5),
(int)(kpN->y + 0.5), be1->distance, be2->distance);
*/
}
return (matches);
}
