implemented DP-based seam estimation method

modules/stitching/include/opencv2/stitching/detail/seam_finders.hpp

@@ -43,6 +43,7 @@
 #ifndef __OPENCV_STITCHING_SEAM_FINDERS_HPP__
 #define __OPENCV_STITCHING_SEAM_FINDERS_HPP__
 
+#include <set>
 #include "opencv2/core/core.hpp"
 #include "opencv2/opencv_modules.hpp"
 
@@ -92,6 +93,114 @@ private:
 };
 
 
+class CV_EXPORTS DpSeamFinder : public SeamFinder
+{
+public:
+    enum CostFunction { COLOR, COLOR_GRAD };
+
+    DpSeamFinder(CostFunction costFunc = COLOR_GRAD);
+
+    CostFunction costFunction() const { return costFunc_; }
+    void setCostFunction(CostFunction val) { costFunc_ = val; }
+
+private:
+    enum ComponentState
+    {
+        FIRST = 1, SECOND = 2, INTERS = 4,
+        INTERS_FIRST = INTERS | FIRST,
+        INTERS_SECOND = INTERS | SECOND
+    };
+
+    class ImagePairLess
+    {
+    public:
+        ImagePairLess(const std::vector<Mat> &images, const std::vector<Point> &corners)
+            : src_(&images[0]), corners_(&corners[0]) {}
+
+        bool operator() (const std::pair<int, int> &l, const std::pair<int, int> &r) const
+        {
+            Point c1 = corners_[l.first] + Point(src_[l.first].cols / 2, src_[l.first].rows / 2);
+            Point c2 = corners_[l.second] + Point(src_[l.second].cols / 2, src_[l.second].rows / 2);
+            int d1 = (c1 - c2).dot(c1 - c2);
+
+            c1 = corners_[r.first] + Point(src_[r.first].cols / 2, src_[r.first].rows / 2);
+            c2 = corners_[r.second] + Point(src_[r.second].cols / 2, src_[r.second].rows / 2);
+            int d2 = (c1 - c2).dot(c1 - c2);
+
+            return d1 < d2;
+        }
+
+    private:
+        const Mat *src_;
+        const Point *corners_;
+    };
+
+    class ClosePoints
+    {
+    public:
+        ClosePoints(int minDist) : minDist_(minDist) {}
+
+        bool operator() (const Point &p1, const Point &p2) const
+        {
+            int dist2 = (p1.x-p2.x) * (p1.x-p2.x) + (p1.y-p2.y) * (p1.y-p2.y);
+            return dist2 < minDist_ * minDist_;
+        }
+
+    private:
+        int minDist_;
+    };
+
+    virtual void find(const std::vector<Mat> &src, const std::vector<Point> &corners,
+                      std::vector<Mat> &masks);
+
+    void process(const Mat &image1, const Mat &image2, Point tl1, Point tl2,
+                 Mat &mask1, Mat &mask2);
+
+    void findComponents();
+
+    void findEdges();
+
+    void resolveConflicts(const Mat &image1, const Mat &image2,
+                          Point tl1, Point tl2, Mat &mask1, Mat &mask2);
+
+    void computeGradients(const Mat &image1, const Mat &image2);
+
+    bool hasOnlyOneNeighbor(int c);
+
+    bool closeToContour(int y, int x, const Mat_<uchar> &contourMask);
+
+    bool getSeamTips(int c1, int c2, Point &p1, Point &p2);
+
+    void computeCosts(const Mat &image1, const Mat &image2, Point tl1, Point tl2,
+                      int c, Mat_<float> &costV, Mat_<float> &costH);
+
+    bool estimateSeam(
+            const Mat &image1, const Mat &image2, Point tl1, Point tl2, int c,
+            Point p1, Point p2, std::vector<Point> &seam, bool &isHorizontal);
+
+    void updateLabelsUsingSeam(int c1, int c2, const std::vector<Point> &seam,
+                               bool isHorizontalSeam);
+
+    CostFunction costFunc_;
+
+    // processing images pair data
+    Point unionTl_, unionBr_;
+    Size unionSize_;
+    Mat_<uchar> mask1_, mask2_;
+    Mat_<uchar> contour1mask_, contour2mask_;
+    Mat_<float> gradx1_, grady1_;
+    Mat_<float> gradx2_, grady2_;
+
+    // components data
+    int ncomps_;
+    Mat_<int> labels_;
+    std::vector<ComponentState> states_;
+    std::vector<Point> tls_, brs_;
+    std::vector<std::vector<Point> > contours_;
+    std::set<std::pair<int, int> > edges_;
+};
+
+
 class CV_EXPORTS GraphCutSeamFinderBase
 {
 public:

modules/stitching/src/seam_finders.cpp

@@ -41,6 +41,9 @@
 //M*/
 
 #include "precomp.hpp"
+#include <map>
+
+using namespace std;
 
 namespace cv {
 namespace detail {
@@ -152,6 +155,853 @@ void VoronoiSeamFinder::findInPair(size_t first, size_t second, Rect roi)
 }
 
 
+DpSeamFinder::DpSeamFinder(CostFunction costFunc) : costFunc_(costFunc) {}
+
+
+void DpSeamFinder::find(const vector<Mat> &src, const vector<Point> &corners, vector<Mat> &masks)
+{
+    LOGLN("Finding seams...");
+    int64 t = getTickCount();
+
+    if (src.size() == 0)
+        return;
+
+    vector<pair<int, int> > pairs;
+
+    for (size_t i = 0; i+1 < src.size(); ++i)
+        for (size_t j = i+1; j < src.size(); ++j)
+            pairs.push_back(make_pair(i, j));
+
+    sort(pairs.begin(), pairs.end(), ImagePairLess(src, corners));
+    reverse(pairs.begin(), pairs.end());
+
+    for (size_t i = 0; i < pairs.size(); ++i)
+    {
+        int i0 = pairs[i].first, i1 = pairs[i].second;
+        process(src[i0], src[i1], corners[i0], corners[i1], masks[i0], masks[i1]);
+    }
+
+    LOGLN("Finding seams, time: " << ((getTickCount() - t) / getTickFrequency()) << " sec");
+}
+
+
+void DpSeamFinder::process(
+        const Mat &image1, const Mat &image2, Point tl1, Point tl2,
+        Mat &mask1, Mat &mask2)
+{
+    Point intersectTl(std::max(tl1.x, tl2.x), std::max(tl1.y, tl2.y));
+
+    Point intersectBr(std::min(tl1.x + image1.cols, tl2.x + image2.cols),
+                      std::min(tl1.y + image1.rows, tl2.y + image2.rows));
+
+    if (intersectTl.x >= intersectBr.x || intersectTl.y >= intersectBr.y)
+        return; // there are no conflicts
+
+    unionTl_ = Point(std::min(tl1.x, tl2.x), std::min(tl1.y, tl2.y));
+
+    unionBr_ = Point(std::max(tl1.x + image1.cols, tl2.x + image2.cols),
+                     std::max(tl1.y + image1.rows, tl2.y + image2.rows));
+
+    unionSize_ = Size(unionBr_.x - unionTl_.x, unionBr_.y - unionTl_.y);
+
+    mask1_ = Mat::zeros(unionSize_, CV_8U);
+    mask2_ = Mat::zeros(unionSize_, CV_8U);
+
+    Mat tmp = mask1_(Rect(tl1.x - unionTl_.x, tl1.y - unionTl_.y, mask1.cols, mask1.rows));
+    mask1.copyTo(tmp);
+
+    tmp = mask2_(Rect(tl2.x - unionTl_.x, tl2.y - unionTl_.y, mask2.cols, mask2.rows));
+    mask2.copyTo(tmp);
+
+    // find both images contour masks
+
+    contour1mask_ = Mat::zeros(unionSize_, CV_8U);
+    contour2mask_ = Mat::zeros(unionSize_, CV_8U);
+
+    for (int y = 0; y < unionSize_.height; ++y)
+    {
+        for (int x = 0; x < unionSize_.width; ++x)
+        {
+            if (mask1_(y, x) &&
+                ((x == 0 || !mask1_(y, x-1)) || (x == unionSize_.width-1 || !mask1_(y, x+1)) ||
+                 (y == 0 || !mask1_(y-1, x)) || (y == unionSize_.height-1 || !mask1_(y+1, x))))
+            {
+                contour1mask_(y, x) = 255;
+            }
+
+            if (mask2_(y, x) &&
+                ((x == 0 || !mask2_(y, x-1)) || (x == unionSize_.width-1 || !mask2_(y, x+1)) ||
+                 (y == 0 || !mask2_(y-1, x)) || (y == unionSize_.height-1 || !mask2_(y+1, x))))
+            {
+                contour2mask_(y, x) = 255;
+            }
+        }
+    }
+
+    findComponents();
+
+    findEdges();
+
+    resolveConflicts(image1, image2, tl1, tl2, mask1, mask2);
+}
+
+
+void DpSeamFinder::findComponents()
+{
+    // label all connected components and get information about them
+
+    ncomps_ = 0;
+    labels_.create(unionSize_);
+    states_.clear();
+    tls_.clear();
+    brs_.clear();
+    contours_.clear();
+
+    for (int y = 0; y < unionSize_.height; ++y)
+    {
+        for (int x = 0; x < unionSize_.width; ++x)
+        {
+            if (mask1_(y, x) && mask2_(y, x))
+                labels_(y, x) = numeric_limits<int>::max();
+            else if (mask1_(y, x))
+                labels_(y, x) = numeric_limits<int>::max()-1;
+            else if (mask2_(y, x))
+                labels_(y, x) = numeric_limits<int>::max()-2;
+            else
+                labels_(y, x) = 0;
+        }
+    }
+
+    for (int y = 0; y < unionSize_.height; ++y)
+    {
+        for (int x = 0; x < unionSize_.width; ++x)
+        {
+            if (labels_(y, x) >= numeric_limits<int>::max()-2)
+            {
+                if (labels_(y, x) == numeric_limits<int>::max())
+                    states_.push_back(INTERS);
+                else if (labels_(y, x) == numeric_limits<int>::max()-1)
+                    states_.push_back(FIRST);
+                else if (labels_(y, x) == numeric_limits<int>::max()-2)
+                    states_.push_back(SECOND);
+
+                floodFill(labels_, Point(x, y), ++ncomps_);
+                tls_.push_back(Point(x, y));
+                brs_.push_back(Point(x+1, y+1));
+                contours_.push_back(vector<Point>());
+            }
+
+            if (labels_(y, x))
+            {
+                int l = labels_(y, x);
+                int ci = l-1;
+
+                tls_[ci].x = std::min(tls_[ci].x, x);
+                tls_[ci].y = std::min(tls_[ci].y, y);
+                brs_[ci].x = std::max(brs_[ci].x, x+1);
+                brs_[ci].y = std::max(brs_[ci].y, y+1);
+
+                if ((x == 0 || labels_(y, x-1) != l) || (x == unionSize_.width-1 || labels_(y, x+1) != l) ||
+                    (y == 0 || labels_(y-1, x) != l) || (y == unionSize_.height-1 || labels_(y+1, x) != l))
+                {
+                    contours_[ci].push_back(Point(x, y));
+                }
+            }
+        }
+    }
+}
+
+
+void DpSeamFinder::findEdges()
+{
+    // find edges between components
+
+    map<pair<int, int>, int> wedges; // weighted edges
+
+    for (int ci = 0; ci < ncomps_-1; ++ci)
+    {
+        for (int cj = ci+1; cj < ncomps_; ++cj)
+        {
+            wedges[make_pair(ci, cj)] = 0;
+            wedges[make_pair(cj, ci)] = 0;
+        }
+    }
+
+    for (int ci = 0; ci < ncomps_; ++ci)
+    {
+        for (size_t i = 0; i < contours_[ci].size(); ++i)
+        {
+            int x = contours_[ci][i].x;
+            int y = contours_[ci][i].y;
+            int l = ci + 1;
+
+            if (x > 0 && labels_(y, x-1) && labels_(y, x-1) != l)
+            {
+                wedges[make_pair(ci, labels_(y, x-1)-1)]++;
+                wedges[make_pair(labels_(y, x-1)-1, ci)]++;
+            }
+
+            if (y > 0 && labels_(y-1, x) && labels_(y-1, x) != l)
+            {
+                wedges[make_pair(ci, labels_(y-1, x)-1)]++;
+                wedges[make_pair(labels_(y-1, x)-1, ci)]++;
+            }
+
+            if (x < unionSize_.width-1 && labels_(y, x+1) && labels_(y, x+1) != l)
+            {
+                wedges[make_pair(ci, labels_(y, x+1)-1)]++;
+                wedges[make_pair(labels_(y, x+1)-1, ci)]++;
+            }
+
+            if (y < unionSize_.height-1 && labels_(y+1, x) && labels_(y+1, x) != l)
+            {
+                wedges[make_pair(ci, labels_(y+1, x)-1)]++;
+                wedges[make_pair(labels_(y+1, x)-1, ci)]++;
+            }
+        }
+    }
+
+    edges_.clear();
+
+    for (int ci = 0; ci < ncomps_-1; ++ci)
+    {
+        for (int cj = ci+1; cj < ncomps_; ++cj)
+        {
+            map<pair<int, int>, int>::iterator itr = wedges.find(make_pair(ci, cj));
+            if (itr != wedges.end() && itr->second > 0)
+                edges_.insert(itr->first);
+
+            itr = wedges.find(make_pair(cj, ci));
+            if (itr != wedges.end() && itr->second > 0)
+                edges_.insert(itr->first);
+        }
+    }
+}
+
+
+void DpSeamFinder::resolveConflicts(const Mat &image1, const Mat &image2,
+                                    Point tl1, Point tl2, Mat &mask1, Mat &mask2)
+{
+    if (costFunc_ == COLOR_GRAD)
+        computeGradients(image1, image2);
+
+    // resolve conflicts between components
+
+    bool hasConflict = true;
+    while (hasConflict)
+    {
+        int c1, c2;
+        hasConflict = false;
+
+        for (set<pair<int, int> >::iterator itr = edges_.begin(); itr != edges_.end(); ++itr)
+        {
+            c1 = itr->first;
+            c2 = itr->second;
+
+            if ((states_[c1] & INTERS) && (states_[c1] & (~INTERS)) != states_[c2])
+            {
+                hasConflict = true;
+                break;
+            }
+        }
+
+        if (hasConflict)
+        {
+            int l1 = c1+1, l2 = c2+1;
+
+            if (hasOnlyOneNeighbor(c1))
+            {
+                // if the first components has only one adjacent component
+
+                for (int y = tls_[c1].y; y < brs_[c1].y; ++y)
+                    for (int x = tls_[c1].x; x < brs_[c1].x; ++x)
+                        if (labels_(y, x) == l1)
+                            labels_(y, x) = l2;
+
+                states_[c1] = states_[c2] == FIRST ? SECOND : FIRST;
+            }
+            else
+            {
+                // if the first component has more than one adjacent component
+
+                Point p1, p2;
+                if (getSeamTips(c1, c2, p1, p2))
+                {
+                    vector<Point> seam;
+                    bool isHorizontalSeam;
+
+                    if (estimateSeam(image1, image2, tl1, tl2, c1, p1, p2, seam, isHorizontalSeam))
+                        updateLabelsUsingSeam(c1, c2, seam, isHorizontalSeam);
+                }
+
+                states_[c1] = states_[c2] == FIRST ? INTERS_SECOND : INTERS_FIRST;
+            }
+
+            const int c[] = {c1, c2};
+            const int l[] = {l1, l2};
+
+            for (int i = 0; i < 2; ++i)
+            {
+                // update information about the (i+1)-th component
+
+                int x0 = tls_[c[i]].x, x1 = brs_[c[i]].x;
+                int y0 = tls_[c[i]].y, y1 = brs_[c[i]].y;
+
+                tls_[c[i]] = Point(numeric_limits<int>::max(), numeric_limits<int>::max());
+                brs_[c[i]] = Point(numeric_limits<int>::min(), numeric_limits<int>::min());
+                contours_[c[i]].clear();
+
+                for (int y = y0; y < y1; ++y)
+                {
+                    for (int x = x0; x < x1; ++x)
+                    {
+                        if (labels_(y, x) == l[i])
+                        {
+                            tls_[c[i]].x = std::min(tls_[c[i]].x, x);
+                            tls_[c[i]].y = std::min(tls_[c[i]].y, y);
+                            brs_[c[i]].x = std::max(brs_[c[i]].x, x+1);
+                            brs_[c[i]].y = std::max(brs_[c[i]].y, y+1);
+
+                            if ((x == 0 || labels_(y, x-1) != l[i]) || (x == unionSize_.width-1 || labels_(y, x+1) != l[i]) ||
+                                (y == 0 || labels_(y-1, x) != l[i]) || (y == unionSize_.height-1 || labels_(y+1, x) != l[i]))
+                            {
+                                contours_[c[i]].push_back(Point(x, y));
+                            }
+                        }
+                    }
+                }
+            }
+
+            // remove edges
+
+            edges_.erase(make_pair(c1, c2));
+            edges_.erase(make_pair(c2, c1));
+        }
+    }
+
+    // update masks
+
+    int dx1 = unionTl_.x - tl1.x, dy1 = unionTl_.y - tl1.y;
+    int dx2 = unionTl_.x - tl2.x, dy2 = unionTl_.y - tl2.y;
+
+    for (int y = 0; y < mask2.rows; ++y)
+    {
+        for (int x = 0; x < mask2.cols; ++x)
+        {
+             int l = labels_(y - dy2, x - dx2);
+             if ((states_[l-1] & FIRST) && mask1.at<uchar>(y - dy2 + dy1, x - dx2 + dx1))
+                mask2.at<uchar>(y, x) = 0;
+        }
+    }
+
+    for (int y = 0; y < mask1.rows; ++y)
+    {
+        for (int x = 0; x < mask1.cols; ++x)
+        {
+             int l = labels_(y - dy1, x - dx1);
+             if ((states_[l-1] & SECOND) && mask2.at<uchar>(y - dy1 + dy2, x - dx1 + dx2))
+                mask1.at<uchar>(y, x) = 0;
+        }
+    }
+}
+
+
+void DpSeamFinder::computeGradients(const Mat &image1, const Mat &image2)
+{
+    CV_Assert(costFunction() == COLOR_GRAD);
+    CV_Assert(image1.type() == CV_32FC3);
+    CV_Assert(image2.type() == CV_32FC3);
+
+    Mat gray;
+    cvtColor(image1, gray, CV_BGR2GRAY);
+    Sobel(gray, gradx1_, CV_32F, 1, 0);
+    Sobel(gray, grady1_, CV_32F, 0, 1);
+
+    cvtColor(image2, gray, CV_BGR2GRAY);
+    Sobel(gray, gradx2_, CV_32F, 1, 0);
+    Sobel(gray, grady2_, CV_32F, 0, 1);
+}
+
+
+bool DpSeamFinder::hasOnlyOneNeighbor(int c)
+{
+    set<pair<int, int> >::iterator begin, end;
+    begin = lower_bound(edges_.begin(), edges_.end(), make_pair(c, numeric_limits<int>::min()));
+    end = upper_bound(edges_.begin(), edges_.end(), make_pair(c, numeric_limits<int>::max()));
+    return ++begin == end;
+}
+
+
+bool DpSeamFinder::closeToContour(int y, int x, const Mat_<uchar> &contourMask)
+{
+    const int rad = 2;
+
+    for (int dy = -rad; dy <= rad; ++dy)
+    {
+        if (y + dy >= 0 && y + dy < unionSize_.height)
+        {
+            for (int dx = -rad; dx <= rad; ++dx)
+            {
+                if (x + dx >= 0 && x + dx < unionSize_.width &&
+                    contourMask(y + dy, x + dx))
+                {
+                    return true;
+                }
+            }
+        }
+    }
+
+    return false;
+}
+
+
+bool DpSeamFinder::getSeamTips(int c1, int c2, Point &p1, Point &p2)
+{
+    CV_Assert(states_[c1] & INTERS);
+
+    // find special points
+
+    vector<Point> specialPoints;
+    int l2 = c2+1;
+
+    for (size_t i = 0; i < contours_[c1].size(); ++i)
+    {
+        int x = contours_[c1][i].x;
+        int y = contours_[c1][i].y;
+
+        if (closeToContour(y, x, contour1mask_) &&
+            closeToContour(y, x, contour2mask_) &&
+            ((x > 0 && labels_(y, x-1) == l2) ||
+             (y > 0 && labels_(y-1, x) == l2) ||
+             (x < unionSize_.width-1 && labels_(y, x+1) == l2) ||
+             (y < unionSize_.height-1 && labels_(y+1, x) == l2)))
+        {
+            specialPoints.push_back(Point(x, y));
+        }
+    }
+
+    if (specialPoints.size() < 2)
+        return false;
+
+    // find clusters
+
+    vector<int> labels;
+    cv::partition(specialPoints, labels, ClosePoints(10));
+
+    int nlabels = *max_element(labels.begin(), labels.end()) + 1;
+    if (nlabels < 2)
+        return false;
+
+    vector<Point> sum(nlabels);
+    vector<vector<Point> > points(nlabels);
+
+    for (size_t i = 0; i < specialPoints.size(); ++i)
+    {
+        sum[labels[i]] += specialPoints[i];
+        points[labels[i]].push_back(specialPoints[i]);
+    }
+
+    // select two most distant clusters
+
+    int idx[2];
+
+    double maxDist = -numeric_limits<double>::max();
+
+    for (int i = 0; i < nlabels-1; ++i)
+    {
+        for (int j = i+1; j < nlabels; ++j)
+        {
+            double size1 = points[i].size(), size2 = points[j].size();
+            double cx1 = cvRound(sum[i].x / size1), cy1 = cvRound(sum[i].y / size1);
+            double cx2 = cvRound(sum[j].x / size2), cy2 = cvRound(sum[j].y / size1);
+
+            double dist = (cx1 - cx2) * (cx1 - cx2) + (cy1 - cy2) * (cy1 - cy2);
+            if (dist > maxDist)
+            {
+                maxDist = dist;
+                idx[0] = i;
+                idx[1] = j;
+            }
+        }
+    }
+
+    // select two points closest to the clusters' centers
+
+    Point p[2];
+
+    for (int i = 0; i < 2; ++i)
+    {
+        double size = points[idx[i]].size();
+        double cx = cvRound(sum[idx[i]].x / size);
+        double cy = cvRound(sum[idx[i]].y / size);
+
+        int closest = -1;
+        double minDist = numeric_limits<double>::max();
+
+        for (size_t j = 0; j < points[idx[i]].size(); ++j)
+        {
+            double dist = (points[idx[i]][j].x - cx) * (points[idx[i]][j].x - cx) +
+                          (points[idx[i]][j].y - cy) * (points[idx[i]][j].y - cy);
+            if (dist < minDist)
+            {
+                minDist = dist;
+                closest = j;
+            }
+        }
+
+        p[i] = points[idx[i]][closest];
+    }
+
+    p1 = p[0];
+    p2 = p[1];
+    return true;
+}
+
+
+void DpSeamFinder::computeCosts(const Mat &image1, const Mat &image2, Point tl1, Point tl2,
+                                int c, Mat_<float> &costV, Mat_<float> &costH)
+{
+    CV_Assert(image1.type() == CV_32FC3);
+    CV_Assert(image2.type() == CV_32FC3);
+    CV_Assert(states_[c] & INTERS);
+
+    // compute costs
+
+    int l = c+1;
+    Rect roi(tls_[c], brs_[c]);
+
+    int dx1 = unionTl_.x - tl1.x, dy1 = unionTl_.y - tl1.y;
+    int dx2 = unionTl_.x - tl2.x, dy2 = unionTl_.y - tl2.y;
+
+    const float badRegionCost = normL2(Point3f(255.f, 255.f, 255.f),
+                                       Point3f(0.f, 0.f, 0.f));
+
+    costV.create(roi.height, roi.width+1);
+
+    for (int y = roi.y; y < roi.br().y; ++y)
+    {
+        for (int x = roi.x; x < roi.br().x+1; ++x)
+        {
+            if (labels_(y, x) == l && x > 0 && labels_(y, x-1) == l)
+            {
+                const Point3f &pr1 = image1.at<Point3f>(y + dy1, x + dx1);
+                const Point3f &pl1 = image1.at<Point3f>(y + dy1, x + dx1 - 1);
+                const Point3f &pr2 = image2.at<Point3f>(y + dy2, x + dx2);
+                const Point3f &pl2 = image2.at<Point3f>(y + dy2, x + dx2 - 1);
+
+                float costColor = (normL2(pl1, pr2) + normL2(pl2, pr1)) / 2;
+                if (costFunc_ == COLOR)
+                    costV(y - roi.y, x - roi.x) = costColor;
+                else if (costFunc_ == COLOR_GRAD)
+                {
+                    float costGrad = fabs(gradx1_(y + dy1, x + dx1)) + fabs(gradx1_(y + dy1, x + dx1 - 1)) +
+                                     fabs(gradx2_(y + dy2, x + dx2)) + fabs(gradx2_(y + dy2, x + dx2 - 1)) + 1.f;
+                    costV(y - roi.y, x - roi.x) = costColor / costGrad;
+                }
+            }
+            else
+                costV(y - roi.y, x - roi.x) = badRegionCost;
+        }
+    }
+
+    costH.create(roi.height+1, roi.width);
+
+    for (int y = roi.y; y < roi.br().y+1; ++y)
+    {
+        for (int x = roi.x; x < roi.br().x; ++x)
+        {
+            if (labels_(y, x) == l && y > 0 && labels_(y-1, x) == l)
+            {
+                const Point3f &pd1 = image1.at<Point3f>(y + dy1, x + dx1);
+                const Point3f &pu1 = image1.at<Point3f>(y + dy1 - 1, x + dx1);
+                const Point3f &pd2 = image2.at<Point3f>(y + dy2, x + dx2);
+                const Point3f &pu2 = image2.at<Point3f>(y + dy2 - 1, x + dx2);
+
+                float costColor = (normL2(pu1, pd2) + normL2(pu2, pd1)) / 2;
+                if (costFunc_ == COLOR)
+                    costH(y - roi.y, x - roi.x) = costColor;
+                else if (costFunc_ == COLOR_GRAD)
+                {
+                    float costGrad = fabs(grady1_(y + dy1, x + dx1)) + fabs(grady1_(y + dy1 - 1, x + dx1)) +
+                                     fabs(grady2_(y + dy2, x + dx2)) + fabs(grady2_(y + dy2 - 1, x + dx2)) + 1.f;
+                    costH(y - roi.y, x - roi.x) = costColor / costGrad;
+                }
+            }
+            else
+                costH(y - roi.y, x - roi.x) = badRegionCost;
+        }
+    }
+}
+
+
+bool DpSeamFinder::estimateSeam(
+        const Mat &image1, const Mat &image2, Point tl1, Point tl2, int c,
+        Point p1, Point p2, vector<Point> &seam, bool &isHorizontal)
+{
+    CV_Assert(states_[c] & INTERS);
+
+    Mat_<float> costV, costH;
+    computeCosts(image1, image2, tl1, tl2, c, costV, costH);
+
+    Rect roi(tls_[c], brs_[c]);
+    Point src = p1 - roi.tl();
+    Point dst = p2 - roi.tl();
+    int l = c+1;
+
+    // estimate seam direction
+
+    bool swapped = false;
+    isHorizontal = std::abs(dst.x - src.x) > std::abs(dst.y - src.y);
+
+    if (isHorizontal)
+    {
+        if (src.x > dst.x)
+        {
+            std::swap(src, dst);
+            swapped = true;
+        }
+    }
+    else if (src.y > dst.y)
+    {
+        swapped = true;
+        std::swap(src, dst);
+    }
+
+    // find optimal control
+
+    Mat_<uchar> control = Mat::zeros(roi.size(), CV_8U);
+    Mat_<uchar> reachable = Mat::zeros(roi.size(), CV_8U);
+    Mat_<float> cost = Mat::zeros(roi.size(), CV_32F);
+
+    reachable(src) = 1;
+    cost(src) = 0.f;
+
+    int nsteps;
+    pair<float, int> steps[3];
+
+    if (isHorizontal)
+    {
+        for (int x = src.x+1; x <= dst.x; ++x)
+        {
+            for (int y = 0; y < roi.height; ++y)
+            {
+                // seam follows along upper side of pixels
+
+                nsteps = 0;
+
+                if (labels_(y + roi.y, x + roi.x) == l)
+                {
+                    if (reachable(y, x-1))
+                        steps[nsteps++] = make_pair(cost(y, x-1) + costH(y, x-1), 1);
+                    if (y > 0 && reachable(y-1, x-1))
+                        steps[nsteps++] = make_pair(cost(y-1, x-1) + costH(y-1, x-1) + costV(y-1, x), 2);
+                    if (y < roi.height-1 && reachable(y+1, x-1))
+                        steps[nsteps++] = make_pair(cost(y+1, x-1) + costH(y+1, x-1) + costV(y, x), 3);
+                }
+
+                if (nsteps)
+                {
+                    pair<float, int> opt = *min_element(steps, steps + nsteps);
+                    cost(y, x) = opt.first;
+                    control(y, x) = opt.second;
+                    reachable(y, x) = 255;
+                }
+            }
+        }
+    }
+    else
+    {
+        for (int y = src.y+1; y <= dst.y; ++y)
+        {
+            for (int x = 0; x < roi.width; ++x)
+            {
+                // seam follows along left side of pixels
+
+                nsteps = 0;
+
+                if (labels_(y + roi.y, x + roi.x) == l)
+                {
+                    if (reachable(y-1, x))
+                        steps[nsteps++] = make_pair(cost(y-1, x) + costV(y-1, x), 1);
+                    if (x > 0 && reachable(y-1, x-1))
+                        steps[nsteps++] = make_pair(cost(y-1, x-1) + costV(y-1, x-1) + costH(y, x-1), 2);
+                    if (x < roi.width-1 && reachable(y-1, x+1))
+                        steps[nsteps++] = make_pair(cost(y-1, x+1) + costV(y-1, x+1) + costH(y, x), 3);
+                }
+
+                if (nsteps)
+                {
+                    pair<float, int> opt = *min_element(steps, steps + nsteps);
+                    cost(y, x) = opt.first;
+                    control(y, x) = opt.second;
+                    reachable(y, x) = 255;
+                }
+            }
+        }
+    }
+
+    if (!reachable(dst))
+        return false;
+
+    // restore seam
+
+    Point p = dst;
+    seam.clear();
+    seam.push_back(p + roi.tl());
+
+    if (isHorizontal)
+    {
+        for (; p.x != src.x; seam.push_back(p + roi.tl()))
+        {
+            if (control(p) == 2) p.y--;
+            else if (control(p) == 3) p.y++;
+            p.x--;
+        }
+    }
+    else
+    {
+        for (; p.y != src.y; seam.push_back(p + roi.tl()))
+        {
+            if (control(p) == 2) p.x--;
+            else if (control(p) == 3) p.x++;
+            p.y--;
+        }
+    }
+
+    if (!swapped)
+        reverse(seam.begin(), seam.end());
+
+    CV_Assert(seam.front() == p1);
+    CV_Assert(seam.back() == p2);
+    return true;
+}
+
+
+void DpSeamFinder::updateLabelsUsingSeam(int c1, int c2, const vector<Point> &seam, bool isHorizontalSeam)
+{
+    Mat_<int> mask = Mat::zeros(brs_[c1].y - tls_[c1].y, brs_[c1].x - tls_[c1].x, CV_32S);
+
+    for (size_t i = 0; i < contours_[c1].size(); ++i)
+        mask(contours_[c1][i] - tls_[c1]) = 255;
+
+    for (size_t i = 0; i < seam.size(); ++i)
+        mask(seam[i] - tls_[c1]) = 255;
+
+    // find connected components after seam carving
+
+    int l1 = c1+1, l2 = c2+1;
+
+    int ncomps = 0;
+
+    for (int y = 0; y < mask.rows; ++y)
+        for (int x = 0; x < mask.cols; ++x)
+            if (!mask(y, x) && labels_(y + tls_[c1].y, x + tls_[c1].x) == l1)
+                floodFill(mask, Point(x, y), ++ncomps);
+
+    for (size_t i = 0; i < contours_[c1].size(); ++i)
+    {
+        int x = contours_[c1][i].x - tls_[c1].x;
+        int y = contours_[c1][i].y - tls_[c1].y;
+
+        bool ok = false;
+        static const int dx[] = {-1, +1, 0, 0, -1, +1, -1, +1};
+        static const int dy[] = {0, 0, -1, +1, -1, -1, +1, +1};
+
+        for (int j = 0; j < 8; ++j)
+        {
+            int c = x + dx[j];
+            int r = y + dy[j];
+
+            if (c > 0 && c < mask.cols && r > 0 && r < mask.rows &&
+                mask(r, c) && mask(r, c) != 255)
+            {
+                ok = true;
+                mask(y, x) = mask(r, c);
+            }
+        }
+
+        if (!ok)
+            mask(y, x) = 0;
+    }
+
+    if (isHorizontalSeam)
+    {
+        for (size_t i = 0; i < seam.size(); ++i)
+        {
+            int x = seam[i].x - tls_[c1].x;
+            int y = seam[i].y - tls_[c1].y;
+
+            if (y < mask.rows-1 && mask(y+1, x) && mask(y+1, x) != 255)
+                mask(y, x) = mask(y+1, x);
+            else
+                mask(y, x) = 0;
+        }
+    }
+    else
+    {
+        for (size_t i = 0; i < seam.size(); ++i)
+        {
+            int x = seam[i].x - tls_[c1].x;
+            int y = seam[i].y - tls_[c1].y;
+
+            if (x < mask.cols-1 && mask(y, x+1) && mask(y, x+1) != 255)
+                mask(y, x) = mask(y, x+1);
+            else
+                mask(y, x) = 0;
+        }
+    }
+
+    // find new components connected with the second component and
+    // with other components except the ones we are working with
+
+    map<int, int> connect2;
+    map<int, int> connectOther;
+
+    for (int i = 1; i <= ncomps; ++i)
+    {
+        connect2.insert(make_pair(i, 0));
+        connectOther.insert(make_pair(i, 0));
+    }
+
+    for (size_t i = 0; i < contours_[c1].size(); ++i)
+    {
+        int x = contours_[c1][i].x;
+        int y = contours_[c1][i].y;
+
+        if ((x > 0 && labels_(y, x-1) == l2) ||
+            (y > 0 && labels_(y-1, x) == l2) ||
+            (x < unionSize_.width-1 && labels_(y, x+1) == l2) ||
+            (y < unionSize_.height-1 && labels_(y+1, x) == l2))
+        {
+            connect2[mask(y - tls_[c1].y, x - tls_[c1].x)]++;
+        }
+
+        if ((x > 0 && labels_(y, x-1) != l1 && labels_(y, x-1) != l2) ||
+            (y > 0 && labels_(y-1, x) != l1 && labels_(y-1, x) != l2) ||
+            (x < unionSize_.width-1 && labels_(y, x+1) != l1 && labels_(y, x+1) != l2) ||
+            (y < unionSize_.height-1 && labels_(y+1, x) != l1 && labels_(y+1, x) != l2))
+        {
+            connectOther[mask(y - tls_[c1].y, x - tls_[c1].x)]++;
+        }
+    }
+
+    vector<int> isAdjComp(ncomps + 1, 0);
+
+    for (map<int, int>::iterator itr = connect2.begin(); itr != connect2.end(); ++itr)
+    {
+        double len = contours_[c1].size();
+        isAdjComp[itr->first] = itr->second / len > 0.05 && connectOther.find(itr->first)->second / len < 0.1;
+    }
+
+    // update labels
+
+    for (int y = 0; y < mask.rows; ++y)
+        for (int x = 0; x < mask.cols; ++x)
+            if (mask(y, x) && isAdjComp[mask(y, x)])
+                labels_(y + tls_[c1].y, x + tls_[c1].x) = l2;
+}
+
+
 class GraphCutSeamFinder::Impl : public PairwiseSeamFinder
 {
 public:

samples/cpp/stitching_detailed.cpp

@@ -276,7 +276,9 @@ static int parseCmdArgs(int argc, char** argv)
             if (string(argv[i + 1]) == "no" ||
                 string(argv[i + 1]) == "voronoi" ||
                 string(argv[i + 1]) == "gc_color" ||
-                string(argv[i + 1]) == "gc_colorgrad")
+                string(argv[i + 1]) == "gc_colorgrad" ||
+                string(argv[i + 1]) == "dp_color" ||
+                string(argv[i + 1]) == "dp_colorgrad")
                 seam_find_type = argv[i + 1];
             else
             {
@@ -612,6 +614,10 @@ int main(int argc, char* argv[])
 #endif
             seam_finder = new detail::GraphCutSeamFinder(GraphCutSeamFinderBase::COST_COLOR_GRAD);
     }
+    else if (seam_find_type == "dp_color")
+        seam_finder = new detail::DpSeamFinder(DpSeamFinder::COLOR);
+    else if (seam_find_type == "dp_colorgrad")
+        seam_finder = new detail::DpSeamFinder(DpSeamFinder::COLOR_GRAD);
     if (seam_finder.empty())
     {
         cout << "Can't create the following seam finder '" << seam_find_type << "'\n";