added image stitching module

modules/CMakeLists.txt

@@ -36,4 +36,5 @@ add_subdirectory(haartraining)
 
 if(NOT ANDROID)
   add_subdirectory(gpu)
+  add_subdirectory(stitching)
 endif()

modules/stitching/CMakeLists.txt

+project(stitching)
+
+include_directories(
+    "${CMAKE_CURRENT_SOURCE_DIR}"
+    "${CMAKE_SOURCE_DIR}/modules/core/include"
+    "${CMAKE_SOURCE_DIR}/modules/imgproc/include"
+    "${CMAKE_SOURCE_DIR}/modules/objdetect/include"
+    "${CMAKE_SOURCE_DIR}/modules/ml/include"
+    "${CMAKE_SOURCE_DIR}/modules/highgui/include"
+    "${CMAKE_SOURCE_DIR}/modules/video/include"
+    "${CMAKE_SOURCE_DIR}/modules/features2d/include"
+    "${CMAKE_SOURCE_DIR}/modules/flann/include"
+    "${CMAKE_SOURCE_DIR}/modules/calib3d/include"
+    "${CMAKE_SOURCE_DIR}/modules/legacy/include"
+    "${CMAKE_SOURCE_DIR}/modules/imgproc/src" # for gcgraph.hpp
+    "${CMAKE_SOURCE_DIR}/modules/gpu/include"
+    )
+
+set(stitching_libs opencv_core opencv_imgproc opencv_highgui opencv_features2d opencv_calib3d opencv_gpu)
+
+set(stitching_files blenders.hpp blenders.cpp
+                    focal_estimators.hpp focal_estimators.cpp
+                    motion_estimators.hpp motion_estimators.cpp
+                    seam_finders.hpp seam_finders.cpp
+                    util.hpp util.cpp util_inl.hpp
+                    warpers.hpp warpers.cpp warpers_inl.hpp
+                    main.cpp)
+
+set(the_target opencv_stitching)    
+add_executable(${the_target} ${stitching_files})
+
+add_dependencies(${the_target} ${stitching_libs})
+set_target_properties(${the_target} PROPERTIES
+                      DEBUG_POSTFIX "${OPENCV_DEBUG_POSTFIX}"
+                      ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib/"
+                      RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin/"
+                      INSTALL_NAME_DIR "${CMAKE_INSTALL_PREFIX}/lib"
+                      OUTPUT_NAME "opencv_stitching")
+
+target_link_libraries(${the_target} ${stitching_libs})
+
+install(TARGETS ${the_target} RUNTIME DESTINATION bin COMPONENT main)

modules/stitching/blenders.cpp

+#include <opencv2/imgproc/imgproc.hpp>
+#include "blenders.hpp"
+#include "util.hpp"
+
+using namespace std;
+using namespace cv;
+
+static const float WEIGHT_EPS = 1e-5f;
+
+Ptr<Blender> Blender::createDefault(int type)
+{
+    if (type == NO)
+        return new Blender();
+    if (type == FEATHER)
+        return new FeatherBlender();
+    if (type == MULTI_BAND)
+        return new MultiBandBlender();
+    CV_Error(CV_StsBadArg, "unsupported blending method");
+    return NULL;
+}
+
+
+Point Blender::operator ()(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &masks,
+                           Mat& dst)
+{
+    Mat dst_mask;
+    return (*this)(src, corners, masks, dst, dst_mask);
+}
+
+
+Point Blender::operator ()(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &masks,
+                           Mat &dst, Mat &dst_mask)
+{
+    Point dst_tl = blend(src, corners, masks, dst, dst_mask);
+    dst.setTo(Scalar::all(0), dst_mask == 0);
+    return dst_tl;
+}
+
+
+Point Blender::blend(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &masks,
+                     Mat &dst, Mat &dst_mask)
+{
+    for (size_t i = 0; i < src.size(); ++i)
+    {
+        CV_Assert(src[i].type() == CV_32FC3);
+        CV_Assert(masks[i].type() == CV_8U);
+    }
+    const int image_type = src[0].type();
+
+    Rect dst_roi = resultRoi(src, corners);
+
+    dst.create(dst_roi.size(), image_type);
+    dst.setTo(Scalar::all(0));
+
+    dst_mask.create(dst_roi.size(), CV_8U);
+    dst_mask.setTo(Scalar::all(0));
+
+    for (size_t i = 0; i < src.size(); ++i)
+    {
+        int dx = corners[i].x - dst_roi.x;
+        int dy = corners[i].y - dst_roi.y;
+
+        for (int y = 0; y < src[i].rows; ++y)
+        {
+            const Point3f *src_row = src[i].ptr<Point3f>(y);
+            Point3f *dst_row = dst.ptr<Point3f>(dy + y);
+
+            const uchar *mask_row = masks[i].ptr<uchar>(y);
+            uchar *dst_mask_row = dst_mask.ptr<uchar>(dy + y);
+
+            for (int x = 0; x < src[i].cols; ++x)
+            {
+                if (mask_row[x])
+                    dst_row[dx + x] = src_row[x];
+                dst_mask_row[dx + x] |= mask_row[x];
+            }
+        }
+    }
+
+    return dst_roi.tl();
+}
+
+
+Point FeatherBlender::blend(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &masks,
+                            Mat &dst, Mat &dst_mask)
+{
+    vector<Mat> weights(masks.size());
+    for (size_t i = 0; i < weights.size(); ++i)
+        createWeightMap(masks[i], sharpness_, weights[i]);
+
+    Mat dst_weight;
+    Point dst_tl = blendLinear(src, corners, weights, dst, dst_weight);
+    dst_mask = dst_weight > WEIGHT_EPS;
+
+    return dst_tl;
+}
+
+
+Point MultiBandBlender::blend(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &masks,
+                             Mat &dst, Mat &dst_mask)
+{
+    CV_Assert(src.size() == corners.size() && src.size() == masks.size());
+    const int num_images = src.size();
+
+    Rect dst_roi = resultRoi(src, corners);
+
+    vector<Mat> src_(num_images);
+    vector<Point> corners_(num_images);
+    vector<Mat> masks_(num_images);
+
+    // TODO avoid creating extra border
+    for (int i = 0; i < num_images; ++i)
+    {
+        copyMakeBorder(src[i], src_[i],
+                       corners[i].y - dst_roi.y, dst_roi.br().y - corners[i].y - src[i].rows,
+                       corners[i].x - dst_roi.x, dst_roi.br().x - corners[i].x - src[i].cols,
+                       BORDER_REFLECT);
+        copyMakeBorder(masks[i], masks_[i],
+                       corners[i].y - dst_roi.y, dst_roi.br().y - corners[i].y - src[i].rows,
+                       corners[i].x - dst_roi.x, dst_roi.br().x - corners[i].x - src[i].cols,
+                       BORDER_CONSTANT);
+        corners_[i] = Point(0, 0);
+    }
+
+    Mat weight_map;
+    vector<Mat> src_pyr_gauss;
+    vector< vector<Mat> > src_pyr_laplace(num_images);
+    vector< vector<Mat> > weight_pyr_gauss(num_images);
+
+    // Compute all pyramids
+    for (int i = 0; i < num_images; ++i)
+    {
+        createGaussPyr(src_[i], num_bands_, src_pyr_gauss);
+        createLaplacePyr(src_pyr_gauss, src_pyr_laplace[i]);
+
+        masks_[i].convertTo(weight_map, CV_32F, 1. / 255.);
+        createGaussPyr(weight_map, num_bands_, weight_pyr_gauss[i]);
+    }
+
+    computeResultMask(masks, corners, dst_mask);
+
+    Mat dst_level_weight;
+    vector<Mat> dst_pyr_laplace(num_bands_ + 1);
+    vector<Mat> src_pyr_slice(num_images);
+    vector<Mat> weight_pyr_slice(num_images);
+
+    // Blend pyramids
+    for (int level_id = 0; level_id <= num_bands_; ++level_id)
+    {
+        for (int i = 0; i < num_images; ++i)
+        {
+            src_pyr_slice[i] = src_pyr_laplace[i][level_id];
+            weight_pyr_slice[i] = weight_pyr_gauss[i][level_id];
+        }
+        blendLinear(src_pyr_slice, corners_, weight_pyr_slice,
+                    dst_pyr_laplace[level_id], dst_level_weight);
+    }
+
+    restoreImageFromLaplacePyr(dst_pyr_laplace);
+    dst = dst_pyr_laplace[0];
+
+    return dst_roi.tl();
+}
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Auxiliary functions
+
+Rect resultRoi(const vector<Mat> &src, const vector<Point> &corners)
+{
+    Point tl(numeric_limits<int>::max(), numeric_limits<int>::max());
+    Point br(numeric_limits<int>::min(), numeric_limits<int>::min());
+
+    CV_Assert(src.size() == corners.size());
+    for (size_t i = 0; i < src.size(); ++i)
+    {
+        tl.x = min(tl.x, corners[i].x);
+        tl.y = min(tl.y, corners[i].y);
+        br.x = max(br.x, corners[i].x + src[i].cols);
+        br.y = max(br.y, corners[i].y + src[i].rows);
+    }
+
+    return Rect(tl, br);
+}
+
+
+Point computeResultMask(const vector<Mat> &masks, const vector<Point> &corners, Mat &dst_mask)
+{
+    Rect dst_roi = resultRoi(masks, corners);
+
+    dst_mask.create(dst_roi.size(), CV_8U);
+    dst_mask.setTo(Scalar::all(0));
+
+    for (size_t i = 0; i < masks.size(); ++i)
+    {
+        int dx = corners[i].x - dst_roi.x;
+        int dy = corners[i].y - dst_roi.y;
+
+        for (int y = 0; y < masks[i].rows; ++y)
+        {
+            const uchar *mask_row = masks[i].ptr<uchar>(y);
+            uchar *dst_mask_row = dst_mask.ptr<uchar>(dy + y);
+
+            for (int x = 0; x < masks[i].cols; ++x)
+                dst_mask_row[dx + x] |= mask_row[x];
+        }
+    }
+
+    return dst_roi.tl();
+}
+
+
+Point blendLinear(const vector<Mat> &src, const vector<Point> &corners, const vector<Mat> &weights,
+                  Mat &dst, Mat& dst_weight)
+{
+    for (size_t i = 0; i < src.size(); ++i)
+    {
+        CV_Assert(src[i].type() == CV_32FC3);
+        CV_Assert(weights[i].type() == CV_32F);
+    }
+    const int image_type = src[0].type();
+
+    Rect dst_roi = resultRoi(src, corners);
+
+    dst.create(dst_roi.size(), image_type);
+    dst.setTo(Scalar::all(0));
+
+    dst_weight.create(dst_roi.size(), CV_32F);
+    dst_weight.setTo(Scalar::all(0));
+
+    // Compute colors sums and weights
+    for (size_t i = 0; i < src.size(); ++i)
+    {
+        int dx = corners[i].x - dst_roi.x;
+        int dy = corners[i].y - dst_roi.y;
+
+        for (int y = 0; y < src[i].rows; ++y)
+        {
+            const Point3f *src_row = src[i].ptr<Point3f>(y);
+            Point3f *dst_row = dst.ptr<Point3f>(dy + y);
+
+            const float *weight_row = weights[i].ptr<float>(y);
+            float *dst_weight_row = dst_weight.ptr<float>(dy + y);
+
+            for (int x = 0; x < src[i].cols; ++x)
+            {
+                dst_row[dx + x] += src_row[x] * weight_row[x];
+                dst_weight_row[dx + x] += weight_row[x];
+            }
+        }
+    }
+
+    // Normalize sums
+    for (int y = 0; y < dst.rows; ++y)
+    {
+        Point3f *dst_row = dst.ptr<Point3f>(y);
+        float *dst_weight_row = dst_weight.ptr<float>(y);
+
+        for (int x = 0; x < dst.cols; ++x)
+        {
+            dst_weight_row[x] += WEIGHT_EPS;
+            dst_row[x] *= 1.f / dst_weight_row[x];
+        }
+    }
+
+    return dst_roi.tl();
+}
+
+
+void createWeightMap(const Mat &mask, float sharpness, Mat &weight)
+{
+    CV_Assert(mask.type() == CV_8U);
+    distanceTransform(mask, weight, CV_DIST_L1, 3);
+    threshold(weight * sharpness, weight, 1.f, 1.f, THRESH_TRUNC);
+}
+
+
+void createGaussPyr(const Mat &img, int num_layers, vector<Mat> &pyr)
+{
+    pyr.resize(num_layers + 1);
+    pyr[0] = img.clone();
+    for (int i = 0; i < num_layers; ++i)
+        pyrDown(pyr[i], pyr[i + 1]);
+}
+
+
+void createLaplacePyr(const vector<Mat> &pyr_gauss, vector<Mat> &pyr_laplace)
+{
+    if (pyr_gauss.size() == 0)
+        return;
+
+    pyr_laplace.resize(pyr_gauss.size());
+
+    Mat tmp;
+    for (size_t i = 0; i < pyr_laplace.size() - 1; ++i)
+    {
+        pyrUp(pyr_gauss[i + 1], tmp, pyr_gauss[i].size());
+        pyr_laplace[i] = pyr_gauss[i] - tmp;
+    }
+    pyr_laplace[pyr_laplace.size() - 1] = pyr_gauss[pyr_laplace.size() - 1].clone();
+}
+
+
+void restoreImageFromLaplacePyr(vector<Mat> &pyr)
+{
+    if (pyr.size() == 0)
+        return;
+
+    Mat tmp;
+    for (size_t i = pyr.size() - 1; i > 0; --i)
+    {
+        pyrUp(pyr[i], tmp, pyr[i - 1].size());
+        pyr[i - 1] += tmp;
+    }
+}

modules/stitching/blenders.hpp

+#ifndef _OPENCV_BLENDERS_HPP_
+#define _OPENCV_BLENDERS_HPP_
+
+#include <vector>
+#include <opencv2/core/core.hpp>
+
+// Simple blender which puts one image over another
+class Blender
+{
+public:
+    enum { NO, FEATHER, MULTI_BAND };
+
+    static cv::Ptr<Blender> createDefault(int type);
+
+    cv::Point operator ()(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &masks,
+                          cv::Mat& dst);
+    cv::Point operator ()(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &masks,
+                          cv::Mat& dst, cv::Mat& dst_mask);
+
+protected:
+    virtual cv::Point blend(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &masks,
+                            cv::Mat& dst, cv::Mat& dst_mask);
+};
+
+
+class FeatherBlender : public Blender
+{
+public:
+    FeatherBlender(float sharpness = 0.02f) : sharpness_(sharpness) {}
+
+private:
+    cv::Point blend(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &masks,
+                    cv::Mat &dst, cv::Mat &dst_mask);
+
+    float sharpness_;
+};
+
+
+class MultiBandBlender : public Blender
+{
+public:
+    MultiBandBlender(int num_bands = 10) : num_bands_(num_bands) {}
+
+private:
+    cv::Point blend(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &masks,
+                    cv::Mat& dst, cv::Mat& dst_mask);
+
+    int num_bands_;
+};
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Auxiliary functions
+
+cv::Rect resultRoi(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners);
+
+cv::Point computeResultMask(const std::vector<cv::Mat> &masks, const std::vector<cv::Point> &corners, cv::Mat &mask);
+
+cv::Point blendLinear(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners, const std::vector<cv::Mat> &weights,
+                      cv::Mat& dst, cv::Mat& dst_weight);
+
+void createWeightMap(const cv::Mat& mask, float sharpness, cv::Mat& weight);
+
+void createGaussPyr(const cv::Mat& img, int num_layers, std::vector<cv::Mat>& pyr);
+
+void createLaplacePyr(const std::vector<cv::Mat>& pyr_gauss, std::vector<cv::Mat>& pyr_laplace);
+
+// Restores source image in-place. Result will be in pyr[0].
+void restoreImageFromLaplacePyr(std::vector<cv::Mat>& pyr);
+
+#endif // _OPENCV_BLENDERS_HPP_

modules/stitching/focal_estimators.cpp

+#include "focal_estimators.hpp"
+#include "util.hpp"
+
+using namespace std;
+using namespace cv;
+
+void focalsFromHomography(const Mat& H, double &f0, double &f1, bool &f0_ok, bool &f1_ok)
+{
+    CV_Assert(H.type() == CV_64F && H.size() == Size(3, 3));
+
+    const double h[9] =
+    {
+        H.at<double>(0, 0), H.at<double>(0, 1), H.at<double>(0, 2),
+        H.at<double>(1, 0), H.at<double>(1, 1), H.at<double>(1, 2),
+        H.at<double>(2, 0), H.at<double>(2, 1), H.at<double>(2, 2)
+    };
+
+    f1_ok = true;
+    double denom1 = h[6] * h[7];
+    double denom2 = (h[7] - h[6]) * (h[7] + h[6]);
+    if (max(abs(denom1), abs(denom2)) < 1e-5)
+        f1_ok = false;
+    else
+    {
+        double val1 = -(h[0] * h[1] + h[3] * h[4]) / denom1;
+        double val2 = (h[0] * h[0] + h[3] * h[3] - h[1] * h[1] - h[4] * h[4]) / denom2;
+        if (val1 < val2)
+            swap(val1, val2);
+        if (val1 > 0 && val2 > 0)
+            f1 = sqrt(abs(denom1) > abs(denom2) ? val1 : val2);
+        else if (val1 > 0)
+            f1 = sqrt(val1);
+        else
+            f1_ok = false;
+    }
+
+    f0_ok = true;
+    denom1 = h[0] * h[3] + h[1] * h[4];
+    denom2 = h[0] * h[0] + h[1] * h[1] - h[3] * h[3] - h[4] * h[4];
+    if (max(abs(denom1), abs(denom2)) < 1e-5)
+        f0_ok = false;
+    else
+    {
+        double val1 = -h[2] * h[5] / denom1;
+        double val2 = (h[5] * h[5] - h[2] * h[2]) / denom2;
+        if (val1 < val2)
+            swap(val1, val2);
+        if (val1 > 0 && val2 > 0)
+            f0 = sqrt(abs(denom1) > abs(denom2) ? val1 : val2);
+        else if (val1 > 0)
+            f0 = sqrt(val1);
+        else
+            f0_ok = false;
+    }
+}
+
+
+bool focalsFromFundamental(const Mat &F, double &f0, double &f1)
+{
+    CV_Assert(F.type() == CV_64F);
+    CV_Assert(F.size() == Size(3, 3));
+
+    Mat Ft = F.t();
+    Mat k = Mat::zeros(3, 1, CV_64F);
+    k.at<double>(2, 0) = 1.f;
+
+    // 1. Compute quantities
+    double a = normL2sq(F*Ft*k) / normL2sq(Ft*k);
+    double b = normL2sq(Ft*F*k) / normL2sq(F*k);
+    double c = sqr(k.dot(F*k)) / (normL2sq(Ft*k) * normL2sq(F*k));
+    double d = k.dot(F*Ft*F*k) / k.dot(F*k);
+    double A = 1/c + a - 2*d;
+    double B = 1/c + b - 2*d;
+    double P = 2*(1/c - 2*d + 0.5*normL2sq(F));
+    double Q = -(A + B)/c + 0.5*(normL2sq(F*Ft) - 0.5*sqr(normL2sq(F)));
+
+    // 2. Solve quadratic equation Z*Z*a_ + Z*b_ + c_ = 0
+    double a_ = 1 + c*P;
+    double b_ = -(c*P*P + 2*P + 4*c*Q);
+    double c_ = P*P + 4*c*P*Q + 12*A*B;
+    double D = b_*b_ - 4*a_*c_;
+    if (abs(D) < 1e-5)
+        D = 0;
+    else if (D < 0)
+        return false;
+    double D_sqrt = sqrt(D);
+    double Z0 = (-b_ - D_sqrt) / (2*a_);
+    double Z1 = (-b_ + D_sqrt) / (2*a_);
+
+    // 3. Choose solution
+    double w0 = abs(Z0*Z0*Z0 - 3*P*Z0*Z0 + 2*(P*P + 2*Q)*Z0 - 4*(P*Q + 4*A*B/c));
+    double w1 = abs(Z1*Z1*Z1 - 3*P*Z1*Z1 + 2*(P*P + 2*Q)*Z1 - 4*(P*Q + 4*A*B/c));
+    double Z = Z0;
+    if (w1 < w0)
+        Z = Z1;
+
+    // 4.
+    double X = -1/c*(1 + 2*B/(Z - P));
+    double Y = -1/c*(1 + 2*A/(Z - P));
+
+    // 5. Compute focal lengths
+    f0 = 1/sqrt(1 + X/normL2sq(Ft*k));
+    f1 = 1/sqrt(1 + Y/normL2sq(F*k));
+
+    return true;
+}

modules/stitching/focal_estimators.hpp

+#ifndef _OPENCV_FOCAL_ESTIMATORS_HPP_
+#define _OPENCV_FOCAL_ESTIMATORS_HPP_
+
+#include <opencv2/core/core.hpp>
+
+// See "Construction of Panoramic Image Mosaics with Global and Local Alignment"
+// by Heung-Yeung Shum and Richard Szeliski.
+void focalsFromHomography(const cv::Mat &H, double &f0, double &f1, bool &f0_ok, bool &f1_ok);
+
+bool focalsFromFundamental(const cv::Mat &F, double &f0, double &f1);
+
+#endif // _OPENCV_FOCAL_ESTIMATORS_HPP_

modules/stitching/main.cpp

+#include <opencv2/core/core.hpp>
+#include <opencv2/highgui/highgui.hpp>
+#include "util.hpp"
+#include "warpers.hpp"
+#include "blenders.hpp"
+#include "seam_finders.hpp"
+#include "motion_estimators.hpp"
+
+using namespace std;
+using namespace cv;
+
+void printHelp()
+{
+    cout << "Rotation model stitcher.\n" 
+        << "Usage: stitch img1 img2 [...imgN]\n" 
+        << "\t[--matchconf <0.0-1.0>]\n"
+        << "\t[--ba (ray_space|focal_ray_space)]\n"
+        << "\t[--warp (plane|cylindrical|spherical)]\n" 
+        << "\t[--seam (no|voronoi|graphcut)]\n" 
+        << "\t[--blend (no|feather|multiband)]\n"
+        << "\t[--output <result_img>]\n";
+}
+
+int main(int argc, char* argv[])
+{
+    cv::setBreakOnError(true);
+
+    vector<Mat> images;
+    string result_name = "result.png";
+    int ba_space = BundleAdjuster::RAY_SPACE;
+    int warp_type = Warper::SPHERICAL;
+    bool user_match_conf = false;
+    float match_conf;
+    int seam_find_type = SeamFinder::GRAPH_CUT;
+    int blend_type = Blender::MULTI_BAND;
+
+    if (argc == 1)
+    {
+        printHelp();
+        return 0;
+    }
+
+    for (int i = 1; i < argc; ++i)
+    {
+        if (string(argv[i]) == "--result")
+        {
+            result_name = argv[i + 1];
+            i++;
+        }
+        else if (string(argv[i]) == "--matchconf")
+        {
+            user_match_conf = true;
+            match_conf = static_cast<float>(atof(string(argv[i + 1]).c_str()));
+            i++;
+        }
+        else if (string(argv[i]) == "--ba")
+        {
+            if (string(argv[i + 1]) == "ray_space")
+                ba_space = BundleAdjuster::RAY_SPACE;
+            else if (string(argv[i + 1]) == "focal_ray_space")
+                ba_space = BundleAdjuster::FOCAL_RAY_SPACE;
+            else
+            {
+                cout << "Bad bundle adjustment space\n";
+                return -1;
+            }
+            i++;
+        }
+        else if (string(argv[i]) == "--warp")
+        {
+            if (string(argv[i + 1]) == "plane")
+                warp_type = Warper::PLANE;
+            else if (string(argv[i + 1]) == "cylindrical")
+                warp_type = Warper::CYLINDRICAL;
+            else if (string(argv[i + 1]) == "spherical")
+                warp_type = Warper::SPHERICAL;
+            else
+            {
+                cout << "Bad warping method\n";
+                return -1;
+            }
+            i++;
+        }
+        else if (string(argv[i]) == "--seam")
+        {
+            if (string(argv[i + 1]) == "no")
+                seam_find_type = SeamFinder::NO;
+            else if (string(argv[i + 1]) == "voronoi")
+                seam_find_type = SeamFinder::VORONOI;
+            else if (string(argv[i + 1]) == "graphcut")
+                seam_find_type = SeamFinder::GRAPH_CUT;
+            else
+            {
+                cout << "Bad seam finding method\n";
+                return -1;
+            }
+            i++;
+        }
+        else if (string(argv[i]) == "--blend")
+        {
+            if (string(argv[i + 1]) == "no")
+                blend_type = Blender::NO;
+            else if (string(argv[i + 1]) == "feather")
+                blend_type = Blender::FEATHER;
+            else if (string(argv[i + 1]) == "multiband")
+                blend_type = Blender::MULTI_BAND;
+            else
+            {
+                cout << "Bad blending method\n";
+                return -1;
+            }
+            i++;
+        }
+        else if (string(argv[i]) == "--output")
+        {
+            result_name = argv[i + 1];
+            i++;
+        }
+        else
+        {
+            Mat img = imread(argv[i]);
+            if (img.empty())
+            {
+                cout << "Can't open image " << argv[i] << endl;
+                return -1;
+            }
+            images.push_back(img);
+        }
+    }
+
+    const int num_images = static_cast<int>(images.size());
+    if (num_images < 2)
+    {
+        cout << "Need more images\n";
+        return -1;
+    }
+
+    LOGLN("Finding features...");
+    vector<ImageFeatures> features;
+    SurfFeaturesFinder finder;
+    finder(images, features);
+
+    LOGLN("Pairwise matching...");
+    vector<MatchesInfo> pairwise_matches;
+    BestOf2NearestMatcher matcher;
+    if (user_match_conf)
+        matcher = BestOf2NearestMatcher(true, match_conf);
+    matcher(images, features, pairwise_matches);
+
+    LOGLN("Estimating rotations...");
+    HomographyBasedEstimator estimator;
+    vector<CameraParams> cameras;
+    estimator(images, features, pairwise_matches, cameras);
+
+    for (size_t i = 0; i < cameras.size(); ++i)
+    {
+        Mat R;
+        cameras[i].M.convertTo(R, CV_32F);
+        cameras[i].M = R;
+        LOGLN("Initial focal length " << i << ": " << cameras[i].focal);
+    }
+
+    LOGLN("Bundle adjustment...");
+    BundleAdjuster adjuster(ba_space);
+    adjuster(images, features, pairwise_matches, cameras);
+
+    // Find median focal length
+    vector<double> focals;
+    for (size_t i = 0; i < cameras.size(); ++i)
+    {
+        LOGLN("Camera focal length " << i << ": " << cameras[i].focal);
+        focals.push_back(cameras[i].focal);
+    }
+    nth_element(focals.begin(), focals.end(), focals.begin() + focals.size() / 2);
+    float camera_focal = focals[focals.size() / 2];
+
+    vector<Mat> masks(num_images);
+    for (int i = 0; i < num_images; ++i)
+    {
+        masks[i].create(images[i].size(), CV_8U);
+        masks[i].setTo(Scalar::all(255));
+    }
+
+    vector<Point> corners(num_images);
+    vector<Mat> masks_warped(num_images);
+    vector<Mat> images_warped(num_images);
+
+    LOGLN("Warping images...");
+    Ptr<Warper> warper = Warper::createByCameraFocal(camera_focal, warp_type);
+    for (int i = 0; i < num_images; ++i)
+    {
+        corners[i] = (*warper)(images[i], cameras[i].focal, cameras[i].M, images_warped[i]);
+        (*warper)(masks[i], cameras[i].focal, cameras[i].M, masks_warped[i], INTER_NEAREST, BORDER_CONSTANT);
+    }
+    vector<Mat> images_f(num_images);
+    for (int i = 0; i < num_images; ++i)
+        images_warped[i].convertTo(images_f[i], CV_32F);
+
+    LOGLN("Finding seams...");
+    Ptr<SeamFinder> seam_finder = SeamFinder::createDefault(seam_find_type);
+    (*seam_finder)(images_f, corners, masks_warped);
+
+    LOGLN("Blending images...");
+    Mat result, result_mask;
+    Ptr<Blender> blender = Blender::createDefault(blend_type);
+    (*blender)(images_f, corners, masks_warped, result, result_mask);
+
+    imwrite(result_name, result);
+
+    LOGLN("Finished");
+    return 0;
+}

modules/stitching/motion_estimators.hpp

+#ifndef _OPENCV_MOTION_ESTIMATORS_HPP_
+#define _OPENCV_MOTION_ESTIMATORS_HPP_
+
+#include <vector>
+#include <opencv2/core/core.hpp>
+#include <opencv2/features2d/features2d.hpp>
+#include "util.hpp"
+
+struct ImageFeatures
+{
+    std::vector<cv::KeyPoint> keypoints;
+    cv::Mat descriptors;
+};
+
+
+class FeaturesFinder
+{
+public:
+    virtual ~FeaturesFinder() {}
+    void operator ()(const std::vector<cv::Mat> &images, std::vector<ImageFeatures> &features) { find(images, features); }
+
+protected:
+    virtual void find(const std::vector<cv::Mat> &images, std::vector<ImageFeatures> &features) = 0;
+};
+
+
+class SurfFeaturesFinder : public FeaturesFinder
+{
+public:
+    explicit SurfFeaturesFinder(bool gpu_hint = true);
+
+protected:
+    void find(const std::vector<cv::Mat> &images, std::vector<ImageFeatures> &features);
+
+    cv::Ptr<FeaturesFinder> impl_;
+};
+
+
+struct MatchesInfo
+{
+    MatchesInfo();
+    MatchesInfo(const MatchesInfo &other);
+    const MatchesInfo& operator =(const MatchesInfo &other);
+
+    int src_img_idx, dst_img_idx; // Optional images indices
+    std::vector<cv::DMatch> matches;
+    int num_inliers; // Number of geometrically consistent matches
+    cv::Mat H; // Homography
+};
+
+
+class FeaturesMatcher
+{
+public:
+    virtual ~FeaturesMatcher() {}
+    void operator ()(const cv::Mat &img1, const ImageFeatures &features1, const cv::Mat &img2, const ImageFeatures &features2,
+                     MatchesInfo& matches_info) { match(img1, features1, img2, features2, matches_info); }
+    void operator ()(const std::vector<cv::Mat> &images, const std::vector<ImageFeatures> &features,
+                     std::vector<MatchesInfo> &pairwise_matches);
+
+protected:
+    virtual void match(const cv::Mat &img1, const ImageFeatures &features1, const cv::Mat &img2, const ImageFeatures &features2,
+                       MatchesInfo& matches_info) = 0;
+};
+
+
+class BestOf2NearestMatcher : public FeaturesMatcher
+{
+public:
+    explicit BestOf2NearestMatcher(bool gpu_hint = true, float match_conf = 0.55f, int num_matches_thresh1 = 5, int num_matches_thresh2 = 5);
+
+protected:
+    void match(const cv::Mat &img1, const ImageFeatures &features1, const cv::Mat &img2, const ImageFeatures &features2,
+               MatchesInfo &matches_info);
+
+    int num_matches_thresh1_;
+    int num_matches_thresh2_;
+
+    cv::Ptr<FeaturesMatcher> impl_;
+};
+
+
+struct CameraParams
+{
+    CameraParams();
+    CameraParams(const CameraParams& other);
+    const CameraParams& operator =(const CameraParams& other);
+
+    double focal;
+    cv::Mat M, t;
+};
+
+
+class Estimator
+{
+public:
+    void operator ()(const std::vector<cv::Mat> &images, const std::vector<ImageFeatures> &features,
+                     const std::vector<MatchesInfo> &pairwise_matches, std::vector<CameraParams> &cameras)
+    {
+        estimate(images, features, pairwise_matches, cameras);
+    }
+
+protected:
+    virtual void estimate(const std::vector<cv::Mat> &images, const std::vector<ImageFeatures> &features,
+                          const std::vector<MatchesInfo> &pairwise_matches, std::vector<CameraParams> &cameras) = 0;
+};
+
+
+class HomographyBasedEstimator : public Estimator
+{
+public:
+    HomographyBasedEstimator() : is_focals_estimated_(false) {}
+    bool isFocalsEstimated() const { return is_focals_estimated_; }
+
+private:   
+    void estimate(const std::vector<cv::Mat> &images, const std::vector<ImageFeatures> &features,
+                  const std::vector<MatchesInfo> &pairwise_matches, std::vector<CameraParams> &cameras);
+
+    bool is_focals_estimated_;
+};
+
+
+class BundleAdjuster : public Estimator
+{
+public:
+    enum { RAY_SPACE, FOCAL_RAY_SPACE };
+
+    BundleAdjuster(int cost_space = FOCAL_RAY_SPACE) : cost_space_(cost_space) {}
+
+private:
+    void estimate(const std::vector<cv::Mat> &images, const std::vector<ImageFeatures> &features,
+                  const std::vector<MatchesInfo> &pairwise_matches, std::vector<CameraParams> &cameras);
+
+    void calcError(cv::Mat &err);
+    void calcJacobian();
+
+    int num_images_;
+    int total_num_matches_;
+    const cv::Mat *images_;
+    const ImageFeatures *features_;
+    const MatchesInfo *pairwise_matches_;
+    cv::Mat cameras_;
+    std::vector<std::pair<int,int> > edges_;
+
+    int cost_space_;
+    cv::Mat err_, err1_, err2_;
+    cv::Mat J_;
+};
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Auxiliary functions
+
+void findMaxSpanningTree(int num_images, const std::vector<MatchesInfo> &pairwise_matches, 
+                         Graph &span_tree, std::vector<int> &centers);
+
+#endif // _OPENCV_MOTION_ESTIMATORS_HPP_

modules/stitching/seam_finders.cpp

+#include <opencv2/imgproc/imgproc.hpp>
+#include <gcgraph.hpp>
+#include "seam_finders.hpp"
+#include "util.hpp"
+
+using namespace std;
+using namespace cv;
+
+
+Ptr<SeamFinder> SeamFinder::createDefault(int type)
+{
+    if (type == NO)
+        return new NoSeamFinder();
+    if (type == VORONOI)
+        return new VoronoiSeamFinder();
+    if (type == GRAPH_CUT)
+        return new GraphCutSeamFinder();
+    CV_Error(CV_StsBadArg, "unsupported seam finding method");
+    return NULL;
+}
+
+
+void SeamFinder::operator ()(const vector<Mat> &src, const vector<Point> &corners,
+                             vector<Mat> &masks)
+{
+    find(src, corners, masks);
+}
+
+
+void PairwiseSeamFinder::find(const vector<Mat> &src, const vector<Point> &corners,
+                              vector<Mat> &masks)
+{
+    if (src.size() == 0)
+        return;
+
+    for (size_t i = 0; i < src.size() - 1; ++i)
+    {
+        for (size_t j = i + 1; j < src.size(); ++j)
+        {
+            int x_min = max(corners[i].x, corners[j].x);
+            int x_max = min(corners[i].x + src[i].cols - 1, corners[j].x + src[j].cols - 1);
+            int y_min = max(corners[i].y, corners[j].y);
+            int y_max = min(corners[i].y + src[i].rows - 1, corners[j].y + src[j].rows - 1);
+
+            if (x_max >= x_min && y_max >= y_min)
+                findInPair(src[i], src[j], corners[i], corners[j],
+                           Rect(x_min, y_min, x_max - x_min + 1, y_max - y_min + 1),
+                           masks[i], masks[j]);
+        }
+    }
+}
+
+
+void VoronoiSeamFinder::findInPair(const Mat &img1, const Mat &img2, Point tl1, Point tl2,
+                                   Rect roi, Mat &mask1, Mat &mask2)
+{
+    const int gap = 10;
+
+    Mat submask1(roi.height + 2 * gap, roi.width + 2 * gap, CV_8U);
+    Mat submask2(roi.height + 2 * gap, roi.width + 2 * gap, CV_8U);
+
+    // Cut submasks with some gap
+    for (int y = -gap; y < roi.height + gap; ++y)
+    {
+        for (int x = -gap; x < roi.width + gap; ++x)
+        {
+            int y1 = roi.y - tl1.y + y;
+            int x1 = roi.x - tl1.x + x;
+            if (y1 >= 0 && x1 >= 0 && y1 < img1.rows && x1 < img1.cols)
+                submask1.at<uchar>(y + gap, x + gap) = mask1.at<uchar>(y1, x1);
+            else
+                submask1.at<uchar>(y + gap, x + gap) = 0;
+
+            int y2 = roi.y - tl2.y + y;
+            int x2 = roi.x - tl2.x + x;
+            if (y2 >= 0 && x2 >= 0 && y2 < img2.rows && x2 < img2.cols)
+                submask2.at<uchar>(y + gap, x + gap) = mask2.at<uchar>(y2, x2);
+            else
+                submask2.at<uchar>(y + gap, x + gap) = 0;
+        }
+    }
+
+    Mat collision = (submask1 != 0) & (submask2 != 0);
+    Mat unique1 = submask1.clone(); unique1.setTo(0, collision);
+    Mat unique2 = submask2.clone(); unique2.setTo(0, collision);
+
+    Mat dist1, dist2;
+    distanceTransform(unique1 == 0, dist1, CV_DIST_L1, 3);
+    distanceTransform(unique2 == 0, dist2, CV_DIST_L1, 3);
+
+    Mat seam = dist1 < dist2;
+
+    for (int y = 0; y < roi.height; ++y)
+    {
+        for (int x = 0; x < roi.width; ++x)
+        {
+            if (seam.at<uchar>(y + gap, x + gap))
+                mask2.at<uchar>(roi.y - tl2.y + y, roi.x - tl2.x + x) = 0;
+            else
+                mask1.at<uchar>(roi.y - tl1.y + y, roi.x - tl1.x + x) = 0;
+        }
+    }
+}
+
+
+class GraphCutSeamFinder::Impl
+{
+public:
+    Impl(int cost_type, float terminal_cost, float bad_region_penalty)
+        : cost_type_(cost_type), terminal_cost_(terminal_cost), bad_region_penalty_(bad_region_penalty) {}
+
+    void findInPair(const Mat &img1, const Mat &img2, Point tl1, Point tl2,
+                    Rect roi, Mat &mask1, Mat &mask2);
+
+private:
+    void setGraphWeightsColor(const Mat &img1, const Mat &img2, const Mat &mask1, const Mat &mask2,
+                              GCGraph<float> &graph);
+
+    int cost_type_;
+    float terminal_cost_;
+    float bad_region_penalty_;
+};
+
+
+void GraphCutSeamFinder::Impl::setGraphWeightsColor(const Mat &img1, const Mat &img2, const Mat &mask1, const Mat &mask2,
+                                                    GCGraph<float> &graph)
+{
+    const Size img_size = img1.size();
+
+    // Set terminal weights
+    for (int y = 0; y < img_size.height; ++y)
+    {
+        for (int x = 0; x < img_size.width; ++x)
+        {
+            int v = graph.addVtx();
+            graph.addTermWeights(v, mask1.at<uchar>(y, x) ? terminal_cost_ : 0.f,
+                                    mask2.at<uchar>(y, x) ? terminal_cost_ : 0.f);
+        }
+    }
+
+    const float weight_eps = 1e-3f;
+
+    // Set regular edge weights
+    for (int y = 0; y < img_size.height; ++y)
+    {
+        for (int x = 0; x < img_size.width; ++x)
+        {
+            int v = y * img_size.width + x;
+            if (x < img_size.width - 1)
+            {
+                float weight = normL2(img1.at<Point3f>(y, x), img2.at<Point3f>(y, x)) +
+                               normL2(img1.at<Point3f>(y, x + 1), img2.at<Point3f>(y, x + 1)) +
+                               weight_eps;
+
+                if (!mask1.at<uchar>(y, x) || !mask1.at<uchar>(y, x + 1) ||
+                    !mask2.at<uchar>(y, x) || !mask2.at<uchar>(y, x + 1))
+                    weight += bad_region_penalty_;
+
+                graph.addEdges(v, v + 1, weight, weight);
+            }
+            if (y < img_size.height - 1)
+            {
+                float weight = normL2(img1.at<Point3f>(y, x), img2.at<Point3f>(y, x)) +
+                               normL2(img1.at<Point3f>(y + 1, x), img2.at<Point3f>(y + 1, x)) +
+                               weight_eps;
+
+                if (!mask1.at<uchar>(y, x) || !mask1.at<uchar>(y + 1, x) ||
+                    !mask2.at<uchar>(y, x) || !mask2.at<uchar>(y + 1, x))
+                    weight += bad_region_penalty_;
+
+                graph.addEdges(v, v + img_size.width, weight, weight);
+            }
+        }
+    }
+}
+
+
+void GraphCutSeamFinder::Impl::findInPair(const Mat &img1, const Mat &img2, Point tl1, Point tl2,
+                                          Rect roi, Mat &mask1, Mat &mask2)
+{
+    const int gap = 10;
+
+    Mat subimg1(roi.height + 2 * gap, roi.width + 2 * gap, CV_32FC3);
+    Mat subimg2(roi.height + 2 * gap, roi.width + 2 * gap, CV_32FC3);
+    Mat submask1(roi.height + 2 * gap, roi.width + 2 * gap, CV_8U);
+    Mat submask2(roi.height + 2 * gap, roi.width + 2 * gap, CV_8U);
+
+    // Cut subimages and submasks with some gap
+    for (int y = -gap; y < roi.height + gap; ++y)
+    {
+        for (int x = -gap; x < roi.width + gap; ++x)
+        {
+            int y1 = roi.y - tl1.y + y;
+            int x1 = roi.x - tl1.x + x;
+            if (y1 >= 0 && x1 >= 0 && y1 < img1.rows && x1 < img1.cols)
+            {
+                subimg1.at<Point3f>(y + gap, x + gap) = img1.at<Point3f>(y1, x1);
+                submask1.at<uchar>(y + gap, x + gap) = mask1.at<uchar>(y1, x1);
+            }
+            else
+            {
+                subimg1.at<Point3f>(y + gap, x + gap) = Point3f(0, 0, 0);
+                submask1.at<uchar>(y + gap, x + gap) = 0;
+            }
+
+            int y2 = roi.y - tl2.y + y;
+            int x2 = roi.x - tl2.x + x;
+            if (y2 >= 0 && x2 >= 0 && y2 < img2.rows && x2 < img2.cols)
+            {
+                subimg2.at<Point3f>(y + gap, x + gap) = img2.at<Point3f>(y2, x2);
+                submask2.at<uchar>(y + gap, x + gap) = mask2.at<uchar>(y2, x2);
+            }
+            else
+            {
+                subimg2.at<Point3f>(y + gap, x + gap) = Point3f(0, 0, 0);
+                submask2.at<uchar>(y + gap, x + gap) = 0;
+            }
+        }
+    }
+
+    const int vertex_count = (roi.height + 2 * gap) * (roi.width + 2 * gap);
+    const int edge_count = (roi.height - 1 + 2 * gap) * (roi.width + 2 * gap) +
+                           (roi.width - 1 + 2 * gap) * (roi.height + 2 * gap);
+    GCGraph<float> graph(vertex_count, edge_count);
+
+    switch (cost_type_)
+    {
+    case GraphCutSeamFinder::COST_COLOR:
+        setGraphWeightsColor(subimg1, subimg2, submask1, submask2, graph);
+        break;
+    default:
+        CV_Error(CV_StsBadArg, "unsupported pixel similarity measure");
+    }
+
+    graph.maxFlow();
+
+    for (int y = 0; y < roi.height; ++y)
+    {
+        for (int x = 0; x < roi.width; ++x)
+        {
+            if (graph.inSourceSegment((y + gap) * (roi.width + 2 * gap) + x + gap))
+                mask2.at<uchar>(roi.y - tl2.y + y, roi.x - tl2.x + x) = 0;
+            else
+                mask1.at<uchar>(roi.y - tl1.y + y, roi.x - tl1.x + x) = 0;
+        }
+    }
+}
+
+
+GraphCutSeamFinder::GraphCutSeamFinder(int cost_type, float terminal_cost, float bad_region_penalty)
+    : impl_(new Impl(cost_type, terminal_cost, bad_region_penalty)) {}
+
+
+void GraphCutSeamFinder::findInPair(const Mat &img1, const Mat &img2, Point tl1, Point tl2,
+                                    Rect roi, Mat &mask1, Mat &mask2)
+{
+    impl_->findInPair(img1, img2, tl1, tl2, roi, mask1, mask2);
+}

modules/stitching/seam_finders.hpp

+#ifndef _OPENCV_SEAM_FINDERS_HPP_
+#define _OPENCV_SEAM_FINDERS_HPP_
+
+#include <vector>
+#include <opencv2/core/core.hpp>
+
+class SeamFinder
+{
+public:
+    enum { NO, VORONOI, GRAPH_CUT };
+
+    static cv::Ptr<SeamFinder> createDefault(int type);
+
+    virtual ~SeamFinder() {}
+
+    void operator ()(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners,
+                     std::vector<cv::Mat> &masks);
+
+protected:
+    virtual void find(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners,
+                      std::vector<cv::Mat> &masks) = 0;
+};
+
+
+class NoSeamFinder : public SeamFinder
+{
+protected:
+    void find(const std::vector<cv::Mat>&, const std::vector<cv::Point>&, std::vector<cv::Mat>&) {}
+};
+
+
+class PairwiseSeamFinder : public SeamFinder
+{
+protected:
+    void find(const std::vector<cv::Mat> &src, const std::vector<cv::Point> &corners,
+              std::vector<cv::Mat> &masks);
+
+    virtual void findInPair(const cv::Mat &img1, const cv::Mat &img2, cv::Point tl1, cv::Point tl2,
+                            cv::Rect roi, cv::Mat &mask1, cv::Mat &mask2) = 0;
+};
+
+
+class VoronoiSeamFinder : public PairwiseSeamFinder
+{
+private:
+    void findInPair(const cv::Mat &img1, const cv::Mat &img2, cv::Point tl1, cv::Point tl2,
+                    cv::Rect roi, cv::Mat &mask1, cv::Mat &mask2);
+};
+
+
+class GraphCutSeamFinder : public PairwiseSeamFinder
+{
+public:
+    // TODO add COST_COLOR_GRAD support
+    enum { COST_COLOR/*, COST_COLOR_GRAD*/ };
+
+    GraphCutSeamFinder(int cost_type = COST_COLOR, float terminal_cost = 10000.f,
+                       float bad_region_penalty = 1000.f);
+
+private:
+    void findInPair(const cv::Mat &img1, const cv::Mat &img2, cv::Point tl1, cv::Point tl2,
+                    cv::Rect roi, cv::Mat &mask1, cv::Mat &mask2);
+
+    class Impl;
+    cv::Ptr<Impl> impl_;
+};
+
+#endif // _OPENCV_SEAM_FINDERS_HPP_

modules/stitching/util.cpp

+#include "util.hpp"
+
+using namespace std;
+using namespace cv;
+
+void DjSets::create(int n) {
+    rank_.assign(n, 0);
+    size.assign(n, 1);
+    parent.resize(n);
+    for (int i = 0; i < n; ++i)
+        parent[i] = i;
+}
+
+
+int DjSets::find(int elem) {
+    int set = elem;
+    while (set != parent[set])
+        set = parent[set];
+    int next;
+    while (elem != parent[elem]) {
+        next = parent[elem];
+        parent[elem] = set;
+        elem = next;
+    }
+    return set;
+}
+
+
+int DjSets::merge(int set1, int set2) {
+    if (rank_[set1] < rank_[set2]) {
+        parent[set1] = set2;
+        size[set2] += size[set1];
+        return set2;
+    }
+    if (rank_[set2] < rank_[set1]) {
+        parent[set2] = set1;
+        size[set1] += size[set2];
+        return set1;
+    }
+    parent[set1] = set2;
+    rank_[set2]++;
+    size[set2] += size[set1];
+    return set2;
+}
+
+
+void Graph::addEdge(int from, int to, float weight)
+{
+    edges_[from].push_back(GraphEdge(from, to, weight));
+}

modules/stitching/util.hpp

+#ifndef _OPENCV_STITCHING_UTIL_HPP_
+#define _OPENCV_STITCHING_UTIL_HPP_
+
+#include <vector>
+#include <list>
+#include <opencv2/core/core.hpp>
+
+#define ENABLE_LOG 1
+
+#if ENABLE_LOG
+  #include <iostream>
+  #define LOG(msg) std::cout << msg;
+#else
+  #define LOG(msg)
+#endif
+
+#define LOGLN(msg) LOG(msg << std::endl)
+
+
+class DjSets
+{
+public:
+    DjSets(int n = 0) { create(n); }
+
+    void create(int n);
+    int find(int elem);
+    int merge(int set1, int set2);
+
+    std::vector<int> parent;
+    std::vector<int> size;
+
+private:
+    std::vector<int> rank_;
+};
+
+
+struct GraphEdge
+{
+    GraphEdge(int from, int to, float weight) 
+        : from(from), to(to), weight(weight) {}
+    bool operator <(const GraphEdge& other) const { return weight < other.weight; }
+    bool operator >(const GraphEdge& other) const { return weight > other.weight; }
+
+    int from, to;
+    float weight;
+};
+
+
+class Graph
+{
+public:
+    Graph(int num_vertices = 0) { create(num_vertices); }
+
+    void create(int num_vertices) { edges_.assign(num_vertices, std::list<GraphEdge>()); }
+
+    int numVertices() const { return static_cast<int>(edges_.size()); }
+
+    void addEdge(int from, int to, float weight);
+
+    template <typename B>
+    B forEach(B body) const;
+
+    template <typename B> 
+    B walkBreadthFirst(int from, B body) const;
+    
+private:
+    std::vector< std::list<GraphEdge> > edges_;
+};
+
+#include "util_inl.hpp"
+
+#endif // _OPENCV_STITCHING_UTIL_HPP_

modules/stitching/util_inl.hpp

+#ifndef _OPENCV_STITCHING_UTIL_INL_HPP_
+#define _OPENCV_STITCHING_UTIL_INL_HPP_
+
+#include <queue>
+#include "util.hpp" // Make your IDE see declarations
+
+template <typename B>
+B Graph::forEach(B body) const
+{
+    for (int i = 0; i < numVertices(); ++i)
+    {
+        std::list<GraphEdge>::const_iterator edge = edges_[i].begin();
+        for (; edge != edges_[i].end(); ++edge)
+            body(*edge);
+    }
+    return body;
+}
+
+
+template <typename B>
+B Graph::walkBreadthFirst(int from, B body) const
+{
+    std::vector<bool> was(numVertices(), false);
+    std::queue<int> vertices;
+
+    was[from] = true;
+    vertices.push(from);
+
+    while (!vertices.empty())
+    {
+        int vertex = vertices.front();
+        vertices.pop();
+
+        std::list<GraphEdge>::const_iterator edge = edges_[vertex].begin();
+        for (; edge != edges_[vertex].end(); ++edge)
+        {
+            if (!was[edge->to])
+            {
+                body(*edge);
+                was[edge->to] = true;
+                vertices.push(edge->to);
+            }
+        }
+    }
+
+    return body;
+}
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Some auxiliary math functions
+
+static inline
+float normL2(const cv::Point3f& a, const cv::Point3f& b)
+{
+    return (a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y) + (a.z - b.z) * (a.z - b.z);
+}
+
+
+static inline
+double normL2sq(const cv::Mat &m)
+{
+    return m.dot(m);
+}
+
+
+template <typename T>
+static inline
+T sqr(T x)
+{
+    return x * x;
+}
+
+#endif // _OPENCV_STITCHING_UTIL_INL_HPP_

modules/stitching/warpers.cpp

+#include "warpers.hpp"
+
+using namespace std;
+using namespace cv;
+
+Ptr<Warper> Warper::createByCameraFocal(int focal, int type)
+{
+    if (type == PLANE)
+        return new PlaneWarper(focal);
+    if (type == CYLINDRICAL)
+        return new CylindricalWarper(focal);
+    if (type == SPHERICAL)
+        return new SphericalWarper(focal);
+    CV_Error(CV_StsBadArg, "unsupported warping type");
+    return NULL;
+}
+
+
+void ProjectorBase::setCameraMatrix(const Mat &M)
+{
+    CV_Assert(M.size() == Size(3, 3));
+    CV_Assert(M.type() == CV_32F);
+    m[0] = M.at<float>(0, 0); m[1] = M.at<float>(0, 1); m[2] = M.at<float>(0, 2);
+    m[3] = M.at<float>(1, 0); m[4] = M.at<float>(1, 1); m[5] = M.at<float>(1, 2);
+    m[6] = M.at<float>(2, 0); m[7] = M.at<float>(2, 1); m[8] = M.at<float>(2, 2);
+
+    Mat M_inv = M.inv();
+    minv[0] = M_inv.at<float>(0, 0); minv[1] = M_inv.at<float>(0, 1); minv[2] = M_inv.at<float>(0, 2);
+    minv[3] = M_inv.at<float>(1, 0); minv[4] = M_inv.at<float>(1, 1); minv[5] = M_inv.at<float>(1, 2);
+    minv[6] = M_inv.at<float>(2, 0); minv[7] = M_inv.at<float>(2, 1); minv[8] = M_inv.at<float>(2, 2);
+}
+
+
+Point Warper::operator ()(const Mat &src, float focal, const Mat& M, Mat &dst,
+                          int interp_mode, int border_mode)
+{
+    return warp(src, focal, M, dst, interp_mode, border_mode);
+}
+
+
+void PlaneWarper::detectResultRoi(Point &dst_tl, Point &dst_br)
+{
+    float tl_uf = numeric_limits<float>::max();
+    float tl_vf = numeric_limits<float>::max();
+    float br_uf = -numeric_limits<float>::max();
+    float br_vf = -numeric_limits<float>::max();
+
+    float u, v;
+
+    projector_.mapForward(0, 0, u, v);
+    tl_uf = min(tl_uf, u); tl_vf = min(tl_vf, v);
+    br_uf = max(br_uf, u); br_vf = max(br_vf, v);
+
+    projector_.mapForward(0, static_cast<float>(src_size_.height - 1), u, v);
+    tl_uf = min(tl_uf, u); tl_vf = min(tl_vf, v);
+    br_uf = max(br_uf, u); br_vf = max(br_vf, v);
+
+    projector_.mapForward(static_cast<float>(src_size_.width - 1), 0, u, v);
+    tl_uf = min(tl_uf, u); tl_vf = min(tl_vf, v);
+    br_uf = max(br_uf, u); br_vf = max(br_vf, v);
+
+    projector_.mapForward(static_cast<float>(src_size_.width - 1), static_cast<float>(src_size_.height - 1), u, v);
+    tl_uf = min(tl_uf, u); tl_vf = min(tl_vf, v);
+    br_uf = max(br_uf, u); br_vf = max(br_vf, v);
+
+    dst_tl.x = static_cast<int>(tl_uf);
+    dst_tl.y = static_cast<int>(tl_vf);
+    dst_br.x = static_cast<int>(br_uf);
+    dst_br.y = static_cast<int>(br_vf);
+}
+
+
+void SphericalWarper::detectResultRoi(Point &dst_tl, Point &dst_br)
+{
+    detectResultRoiByBorder(dst_tl, dst_br);
+
+    float tl_uf = static_cast<float>(dst_tl.x);
+    float tl_vf = static_cast<float>(dst_tl.y);
+    float br_uf = static_cast<float>(dst_br.x);
+    float br_vf = static_cast<float>(dst_br.y);
+
+    float x = projector_.minv[1];
+    float y = projector_.minv[4];
+    float z = projector_.minv[7];
+    if (y > 0.f)
+    {
+        x = projector_.focal * x / z + src_size_.width * 0.5f;
+        y = projector_.focal * y / z + src_size_.height * 0.5f;
+        if (x > 0.f && x < src_size_.width && y > 0.f && y < src_size_.height)
+        {
+            tl_uf = min(tl_uf, 0.f); tl_vf = min(tl_vf, static_cast<float>(CV_PI * projector_.scale));
+            br_uf = max(br_uf, 0.f); br_vf = max(br_vf, static_cast<float>(CV_PI * projector_.scale));
+        }
+    }
+
+    x = projector_.minv[1];
+    y = -projector_.minv[4];
+    z = projector_.minv[7];
+    if (y > 0.f)
+    {
+        x = projector_.focal * x / z + src_size_.width * 0.5f;
+        y = projector_.focal * y / z + src_size_.height * 0.5f;
+        if (x > 0.f && x < src_size_.width && y > 0.f && y < src_size_.height)
+        {
+            tl_uf = min(tl_uf, 0.f); tl_vf = min(tl_vf, static_cast<float>(0));
+            br_uf = max(br_uf, 0.f); br_vf = max(br_vf, static_cast<float>(0));
+        }
+    }
+
+    dst_tl.x = static_cast<int>(tl_uf);
+    dst_tl.y = static_cast<int>(tl_vf);
+    dst_br.x = static_cast<int>(br_uf);
+    dst_br.y = static_cast<int>(br_vf);
+}

modules/stitching/warpers.hpp

+#ifndef _OPENCV_WARPERS_HPP_
+#define _OPENCV_WARPERS_HPP_
+
+#include <opencv2/core/core.hpp>
+#include <opencv2/imgproc/imgproc.hpp>
+
+class Warper
+{
+public:
+    enum { PLANE, CYLINDRICAL, SPHERICAL };
+
+    static cv::Ptr<Warper> createByCameraFocal(int focal, int type);
+
+    virtual ~Warper() {}
+
+    cv::Point operator ()(const cv::Mat &src, float focal, const cv::Mat& M, cv::Mat &dst,
+                          int interp_mode = cv::INTER_LINEAR, int border_mode = cv::BORDER_REFLECT);
+
+protected:
+    virtual cv::Point warp(const cv::Mat &src, float focal, const cv::Mat& M, cv::Mat &dst,
+                           int interp_mode, int border_mode) = 0;
+};
+
+
+struct ProjectorBase
+{
+    void setCameraMatrix(const cv::Mat& M);
+
+    cv::Size size;
+    float focal;
+    float m[9];
+    float minv[9];
+    float scale;
+};
+
+
+template <class P>
+class WarperBase : public Warper
+{   
+protected:
+    cv::Point warp(const cv::Mat &src, float focal, const cv::Mat &M, cv::Mat &dst,
+                   int interp_mode, int border_mode);
+
+    // Detects ROI of the destination image. It's correct for any projection.
+    virtual void detectResultRoi(cv::Point &dst_tl, cv::Point &dst_br);
+
+    // Detects ROI of the destination image by walking over image border.
+    // Correctness for any projection isn't guaranteed.
+    void detectResultRoiByBorder(cv::Point &dst_tl, cv::Point &dst_br);
+
+    cv::Size src_size_;
+    P projector_;
+};
+
+
+struct PlaneProjector : ProjectorBase
+{
+    void mapForward(float x, float y, float &u, float &v);
+    void mapBackward(float u, float v, float &x, float &y);
+
+    float plane_dist;
+};
+
+
+// Projects image onto z = plane_dist plane
+class PlaneWarper : public WarperBase<PlaneProjector>
+{
+public:
+    PlaneWarper(float plane_dist = 1.f, float scale = 1.f)
+    {
+        projector_.plane_dist = plane_dist;
+        projector_.scale = scale;
+    }
+
+private:
+    void detectResultRoi(cv::Point &dst_tl, cv::Point &dst_br);
+};
+
+
+struct SphericalProjector : ProjectorBase
+{
+    void mapForward(float x, float y, float &u, float &v);
+    void mapBackward(float u, float v, float &x, float &y);
+};
+
+
+// Projects image onto unit sphere with origin at (0, 0, 0).
+// Poles are located at (0, -1, 0) and (0, 1, 0) points.
+class SphericalWarper : public WarperBase<SphericalProjector>
+{
+public:
+    SphericalWarper(float scale = 300.f) { projector_.scale = scale; }
+
+private:  
+    void detectResultRoi(cv::Point &dst_tl, cv::Point &dst_br);
+};
+
+
+struct CylindricalProjector : ProjectorBase
+{
+    void mapForward(float x, float y, float &u, float &v);
+    void mapBackward(float u, float v, float &x, float &y);
+};
+
+
+// Projects image onto x * x + z * z = 1 cylinder
+class CylindricalWarper : public WarperBase<CylindricalProjector>
+{
+public:
+    CylindricalWarper(float scale = 300.f) { projector_.scale = scale; }
+
+private:
+    void detectResultRoi(cv::Point &dst_tl, cv::Point &dst_br)
+    {
+        WarperBase<CylindricalProjector>::detectResultRoiByBorder(dst_tl, dst_br);
+    }
+};
+
+#include "warpers_inl.hpp"
+
+#endif // _OPENCV_WARPERS_HPP_

modules/stitching/warpers_inl.hpp

+#ifndef _OPENCV_WARPERS_INL_HPP_
+#define _OPENCV_WARPERS_INL_HPP_
+
+#include "warpers.hpp" // Make your IDE see declarations
+
+template <class P>
+cv::Point WarperBase<P>::warp(const cv::Mat &src, float focal, const cv::Mat &M, cv::Mat &dst,
+                              int interp_mode, int border_mode)
+{
+    src_size_ = src.size();
+
+    projector_.size = src.size();
+    projector_.focal = focal;
+    projector_.setCameraMatrix(M);
+
+    cv::Point dst_tl, dst_br;
+    detectResultRoi(dst_tl, dst_br);
+
+    cv::Mat xmap(dst_br.y - dst_tl.y + 1, dst_br.x - dst_tl.x + 1, CV_32F);
+    cv::Mat ymap(dst_br.y - dst_tl.y + 1, dst_br.x - dst_tl.x + 1, CV_32F);
+
+    float x, y;
+    for (int v = dst_tl.y; v <= dst_br.y; ++v)
+    {
+        for (int u = dst_tl.x; u <= dst_br.x; ++u)
+        {
+            projector_.mapBackward(static_cast<float>(u), static_cast<float>(v), x, y);
+            xmap.at<float>(v - dst_tl.y, u - dst_tl.x) = x;
+            ymap.at<float>(v - dst_tl.y, u - dst_tl.x) = y;
+        }
+    }
+
+    dst.create(dst_br.y - dst_tl.y + 1, dst_br.x - dst_tl.x + 1, src.type());
+    remap(src, dst, xmap, ymap, interp_mode, border_mode);
+
+    return dst_tl;
+}
+
+
+template <class P>
+void WarperBase<P>::detectResultRoi(cv::Point &dst_tl, cv::Point &dst_br)
+{
+    float tl_uf = std::numeric_limits<float>::max();
+    float tl_vf = std::numeric_limits<float>::max();
+    float br_uf = -std::numeric_limits<float>::max();
+    float br_vf = -std::numeric_limits<float>::max();
+
+    float u, v;
+    for (int y = 0; y < src_size_.height; ++y)
+    {
+        for (int x = 0; x < src_size_.width; ++x)
+        {
+            projector_.mapForward(static_cast<float>(x), static_cast<float>(y), u, v);
+            tl_uf = std::min(tl_uf, u); tl_vf = std::min(tl_vf, v);
+            br_uf = std::max(br_uf, u); br_vf = std::max(br_vf, v);
+        }
+    }
+
+    dst_tl.x = static_cast<int>(tl_uf);
+    dst_tl.y = static_cast<int>(tl_vf);
+    dst_br.x = static_cast<int>(br_uf);
+    dst_br.y = static_cast<int>(br_vf);
+}
+
+
+template <class P>
+void WarperBase<P>::detectResultRoiByBorder(cv::Point &dst_tl, cv::Point &dst_br)
+{
+    float tl_uf = std::numeric_limits<float>::max();
+    float tl_vf = std::numeric_limits<float>::max();
+    float br_uf = -std::numeric_limits<float>::max();
+    float br_vf = -std::numeric_limits<float>::max();
+
+    float u, v;
+    for (float x = 0; x < src_size_.width; ++x)
+    {
+        projector_.mapForward(static_cast<float>(x), 0, u, v);
+        tl_uf = std::min(tl_uf, u); tl_vf = std::min(tl_vf, v);
+        br_uf = std::max(br_uf, u); br_vf = std::max(br_vf, v);
+
+        projector_.mapForward(static_cast<float>(x), static_cast<float>(src_size_.height - 1), u, v);
+        tl_uf = std::min(tl_uf, u); tl_vf = std::min(tl_vf, v);
+        br_uf = std::max(br_uf, u); br_vf = std::max(br_vf, v);
+    }
+    for (int y = 0; y < src_size_.height; ++y)
+    {
+        projector_.mapForward(0, static_cast<float>(y), u, v);
+        tl_uf = std::min(tl_uf, u); tl_vf = std::min(tl_vf, v);
+        br_uf = std::max(br_uf, u); br_vf = std::max(br_vf, v);
+
+        projector_.mapForward(static_cast<float>(src_size_.width - 1), static_cast<float>(y), u, v);
+        tl_uf = std::min(tl_uf, u); tl_vf = std::min(tl_vf, v);
+        br_uf = std::max(br_uf, u); br_vf = std::max(br_vf, v);
+    }
+
+    dst_tl.x = static_cast<int>(tl_uf);
+    dst_tl.y = static_cast<int>(tl_vf);
+    dst_br.x = static_cast<int>(br_uf);
+    dst_br.y = static_cast<int>(br_vf);
+}
+
+
+inline
+void PlaneProjector::mapForward(float x, float y, float &u, float &v)
+{
+    x -= size.width * 0.5f;
+    y -= size.height * 0.5f;
+
+    float x_ = m[0] * x + m[1] * y + m[2] * focal;
+    float y_ = m[3] * x + m[4] * y + m[5] * focal;
+    float z_ = m[6] * x + m[7] * y + m[8] * focal;
+
+    u = scale * x_ / z_ * plane_dist;
+    v = scale * y_ / z_ * plane_dist;
+}
+
+
+inline
+void PlaneProjector::mapBackward(float u, float v, float &x, float &y)
+{
+    float x_ = u / scale;
+    float y_ = v / scale;
+
+    float z;
+    x = minv[0] * x_ + minv[1] * y_ + minv[2] * plane_dist;
+    y = minv[3] * x_ + minv[4] * y_ + minv[5] * plane_dist;
+    z = minv[6] * x_ + minv[7] * y_ + minv[8] * plane_dist;
+
+    x = focal * x / z + size.width * 0.5f;
+    y = focal * y / z + size.height * 0.5f;
+}
+
+
+inline
+void SphericalProjector::mapForward(float x, float y, float &u, float &v)
+{
+    x -= size.width * 0.5f;
+    y -= size.height * 0.5f;
+
+    float x_ = m[0] * x + m[1] * y + m[2] * focal;
+    float y_ = m[3] * x + m[4] * y + m[5] * focal;
+    float z_ = m[6] * x + m[7] * y + m[8] * focal;
+
+    u = scale * atan2f(x_, z_);
+    v = scale * (static_cast<float>(CV_PI) - acosf(y_ / sqrtf(x_ * x_ + y_ * y_ + z_ * z_)));
+}
+
+
+inline
+void SphericalProjector::mapBackward(float u, float v, float &x, float &y)
+{
+    float sinv = sinf(static_cast<float>(CV_PI) - v / scale);
+    float x_ = sinv * sinf(u / scale);
+    float y_ = cosf(static_cast<float>(CV_PI) - v / scale);
+    float z_ = sinv * cosf(u / scale);
+
+    float z;
+    x = minv[0] * x_ + minv[1] * y_ + minv[2] * z_;
+    y = minv[3] * x_ + minv[4] * y_ + minv[5] * z_;
+    z = minv[6] * x_ + minv[7] * y_ + minv[8] * z_;
+
+    x = focal * x / z + size.width * 0.5f;
+    y = focal * y / z + size.height * 0.5f;
+}
+
+
+inline
+void CylindricalProjector::mapForward(float x, float y, float &u, float &v)
+{
+    x -= size.width * 0.5f;
+    y -= size.height * 0.5f;
+
+    float x_ = m[0] * x + m[1] * y + m[2] * focal;
+    float y_ = m[3] * x + m[4] * y + m[5] * focal;
+    float z_ = m[6] * x + m[7] * y + m[8] * focal;
+
+    u = scale * atan2f(x_, z_);
+    v = scale * y_ / sqrtf(x_ * x_ + z_ * z_);
+}
+
+
+inline
+void CylindricalProjector::mapBackward(float u, float v, float &x, float &y)
+{
+    float x_ = sinf(u / scale);
+    float y_ = v / scale;
+    float z_ = cosf(u / scale);
+
+    float z;
+    x = minv[0] * x_ + minv[1] * y_ + minv[2] * z_;
+    y = minv[3] * x_ + minv[4] * y_ + minv[5] * z_;
+    z = minv[6] * x_ + minv[7] * y_ + minv[8] * z_;
+
+    x = focal * x / z + size.width * 0.5f;
+    y = focal * y / z + size.height * 0.5f;
+}
+
+#endif // _OPENCV_WARPERS_INL_HPP_