LLC(Locality-constrained Linear Coding)基于OpenCV的C++源码实现

《Locality-constrained Linear Coding for Image Classification》的作者提供Matlab的代码实现，见http://www.ifp.illinois.edu/~jyang29/LLC.htm。

下面是根据作者的代码，基于OpenCV，实现的C++版的LLC：

cv::Mat BowModel::findKNN(cv::Mat &codebook, cv::Mat &input, int k) {
int nbase = codebook.rows;
int nquery = input.rows;
Mat ii = input.mul(input);
Mat cc = codebook.mul(codebook);

Mat sii(nquery,1,CV_32FC1);
sii.setTo(0);
Mat scc(nbase,1,CV_32FC1);
scc.setTo(0);
for (int i = 0; i<ii.rows; i++) {
for (int j = 0; j<ii.cols; j++) {
sii.at<float>(i,0) += ii.at<float>(i,j);
}
}
for (int i = 0; i<cc.rows; i++) {
for (int j = 0; j<cc.cols; j++) {
scc.at<float>(i,0) += cc.at<float>(i,j);
}
}

Mat D(nquery,nbase,CV_32FC1);
for (int i = 0; i<nquery; i++) {
for (int j = 0; j<nbase; j++) {
D.at<float>(i,j) = sii.at<float>(i,0);
}
}

Mat ct;
transpose(codebook, ct);
Mat D1 = 2*input*ct;

Mat scct;
transpose(scc, scct);
Mat D2(nquery, nbase, CV_32FC1);
for (int i = 0; i<nquery; i++) {
for (int j = 0; j<nbase; j++) {
D2.at<float>(i,j) = scct.at<float>(0,j);
}
}

D = D - D1 + D2;
Mat SD;
sortIdx(D, SD, CV_SORT_EVERY_ROW+CV_SORT_ASCENDING);
Mat IDX(nquery,k,CV_8UC1);
for (int i = 0; i<nquery; i++) {
for (int j = 0; j<k; j++) {
IDX.at<uchar>(i,j) = SD.row(i).col(j).at<uchar>(0,0);
}
}

ii.release();
cc.release();
sii.release();
scc.release();
D.release();
ct.release();
D1.release();
scct.release();
D2.release();
SD.release();
return IDX;
}

cv::Mat BowModel::llccode(cv::Mat &codebook, cv::Mat &input, cv::Mat IDX, int k)
{
int nquery = input.rows;
int nbase = codebook.rows;
int dim = codebook.cols;

Mat II = Mat::eye(k, k, CV_32FC1);
Mat Coeff(nquery,nbase,CV_32FC1);
Coeff.setTo(0);
Mat z;
Mat z1(k,dim,CV_32FC1);
Mat z2(k,dim,CV_32FC1);
Mat C;
Mat un(k,1,CV_32FC1);
un.setTo(1);
Mat temp;
Mat temp2;
Mat w;
Mat wt;

for (int n = 0; n<nquery; n++) {
for (int i = 0; i<k; i++) {
for (int j = 0; j<dim; j++) {
z1.at<float>(i,j) = codebook.at<float>(IDX.at<uchar>(n,i),j);
z2.at<float>(i,j) = input.at<float>(n,j);
}
}
z = z1 - z2;
transpose(z, temp);
C = z*temp;
C = C + II*(1e-4)*trace(C)[0];
invert(C,temp2);
w = temp2*un;
float sum_w=0;
for (int i = 0; i<k; i++) {
sum_w += w.at<float>(i,0);
}
w = w/sum_w;
transpose(w, wt);
for (int i = 0; i<k; i++) {
Coeff.at<float>(n,IDX.at<uchar>(n,i)) = wt.at<float>(0,i);
}
}

II.release();
z.release();
z1.release();
z2.release();
C.release();
un.release();
temp.release();
temp2.release();
w.release();
wt.release();

return Coeff;
}