Merge pull request #18607 from zteffi:warp-point-backward

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

@@ -70,6 +70,23 @@ public:
      */
     virtual Point2f warpPoint(const Point2f &pt, InputArray K, InputArray R) = 0;
 
+    /** @brief Projects the image point backward.
+
+    @param pt Projected point
+    @param K Camera intrinsic parameters
+    @param R Camera rotation matrix
+    @return Backward-projected point
+    */
+#if CV_VERSION_MAJOR == 4
+    virtual Point2f warpPointBackward(const Point2f& pt, InputArray K, InputArray R)
+    {
+        CV_UNUSED(pt); CV_UNUSED(K); CV_UNUSED(R);
+        CV_Error(Error::StsNotImplemented, "");
+    }
+#else
+    virtual Point2f warpPointBackward(const Point2f& pt, InputArray K, InputArray R) = 0;
+#endif
+
     /** @brief Builds the projection maps according to the given camera data.
 
     @param src_size Source image size
@@ -143,6 +160,8 @@ class CV_EXPORTS_TEMPLATE RotationWarperBase : public RotationWarper
 public:
     Point2f warpPoint(const Point2f &pt, InputArray K, InputArray R) CV_OVERRIDE;
 
+    Point2f warpPointBackward(const Point2f &pt, InputArray K, InputArray R) CV_OVERRIDE;
+
     Rect buildMaps(Size src_size, InputArray K, InputArray R, OutputArray xmap, OutputArray ymap) CV_OVERRIDE;
 
     Point warp(InputArray src, InputArray K, InputArray R, int interp_mode, int border_mode,
@@ -189,6 +208,9 @@ public:
     Point2f warpPoint(const Point2f &pt, InputArray K, InputArray R) CV_OVERRIDE;
     Point2f warpPoint(const Point2f &pt, InputArray K, InputArray R, InputArray T);
 
+    Point2f warpPointBackward(const Point2f& pt, InputArray K, InputArray R) CV_OVERRIDE;
+    Point2f warpPointBackward(const Point2f& pt, InputArray K, InputArray R, InputArray T);
+
     virtual Rect buildMaps(Size src_size, InputArray K, InputArray R, InputArray T, CV_OUT OutputArray xmap, CV_OUT OutputArray ymap);
     Rect buildMaps(Size src_size, InputArray K, InputArray R, CV_OUT OutputArray xmap, CV_OUT OutputArray ymap) CV_OVERRIDE;
 
@@ -228,6 +250,15 @@ public:
      */
     Point2f warpPoint(const Point2f &pt, InputArray K, InputArray H) CV_OVERRIDE;
 
+    /** @brief Projects the image point backward.
+
+    @param pt Projected point
+    @param K Camera intrinsic parameters
+    @param H Camera extrinsic parameters
+    @return Backward-projected point
+    */
+    Point2f warpPointBackward(const Point2f &pt, InputArray K, InputArray H) CV_OVERRIDE;
+
     /** @brief Builds the projection maps according to the given camera data.
 
     @param src_size Source image size

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

@@ -61,6 +61,14 @@ Point2f RotationWarperBase<P>::warpPoint(const Point2f &pt, InputArray K, InputA
     return uv;
 }
 
+template <class P>
+Point2f RotationWarperBase<P>::warpPointBackward(const Point2f& pt, InputArray K, InputArray R)
+{
+    projector_.setCameraParams(K, R);
+    Point2f xy;
+    projector_.mapBackward(pt.x, pt.y, xy.x, xy.y);
+    return xy;
+}
 
 template <class P>
 Rect RotationWarperBase<P>::buildMaps(Size src_size, InputArray K, InputArray R, OutputArray _xmap, OutputArray _ymap)

modules/stitching/include/opencv2/stitching/warpers.hpp

@@ -65,6 +65,22 @@ namespace cv {
         */
         CV_WRAP Point2f warpPoint(const Point2f &pt, InputArray K, InputArray R);
 
+        /** @brief Projects the image point backward.
+
+        @param pt Projected point
+        @param K Camera intrinsic parameters
+        @param R Camera rotation matrix
+        @return Backward-projected point
+        */
+#if CV_VERSION_MAJOR == 4
+        CV_WRAP Point2f warpPointBackward(const Point2f& pt, InputArray K, InputArray R)
+        {
+            CV_UNUSED(pt); CV_UNUSED(K); CV_UNUSED(R);
+            CV_Error(Error::StsNotImplemented, "");
+        }
+#else
+        CV_WRAP Point2f warpPointBackward(const Point2f &pt, InputArray K, InputArray R);
+#endif
         /** @brief Builds the projection maps according to the given camera data.
 
         @param src_size Source image size

modules/stitching/src/warpers.cpp

@@ -92,6 +92,14 @@ Point2f PyRotationWarper::warpPoint(const Point2f &pt, InputArray K, InputArray
 {
     return rw.get()->warpPoint(pt, K, R);
 }
+
+#if CV_VERSION_MAJOR != 4
+Point2f PyRotationWarper::warpPointBackward(const Point2f& pt, InputArray K, InputArray R)
+{
+    return rw.get()->warpPointBackward(pt, K, R);
+}
+#endif
+
 Rect PyRotationWarper::buildMaps(Size src_size, InputArray K, InputArray R, OutputArray xmap, OutputArray ymap)
 {
     return rw.get()->buildMaps(src_size, K, R, xmap, ymap);
@@ -164,6 +172,20 @@ Point2f PlaneWarper::warpPoint(const Point2f &pt, InputArray K, InputArray R)
     Mat_<float> T(3, 1, tz);
     return warpPoint(pt, K, R, T);
 }
+Point2f PlaneWarper::warpPointBackward(const Point2f& pt, InputArray K, InputArray R, InputArray T)
+{
+    projector_.setCameraParams(K, R, T);
+    Point2f xy;
+    projector_.mapBackward(pt.x, pt.y, xy.x, xy.y);
+    return xy;
+}
+
+Point2f PlaneWarper::warpPointBackward(const Point2f& pt, InputArray K, InputArray R)
+{
+    float tz[] = { 0.f, 0.f, 0.f };
+    Mat_<float> T(3, 1, tz);
+    return warpPointBackward(pt, K, R, T);
+}
 
 Rect PlaneWarper::buildMaps(Size src_size, InputArray K, InputArray R, OutputArray xmap, OutputArray ymap)
 {
@@ -299,6 +321,12 @@ Point2f AffineWarper::warpPoint(const Point2f &pt, InputArray K, InputArray H)
     return PlaneWarper::warpPoint(pt, K, R, T);
 }
 
+Point2f AffineWarper::warpPointBackward(const Point2f& pt, InputArray K, InputArray H)
+{
+    Mat R, T;
+    getRTfromHomogeneous(H, R, T);
+    return PlaneWarper::warpPointBackward(pt, K, R, T);
+}
 
 Rect AffineWarper::buildMaps(Size src_size, InputArray K, InputArray H, OutputArray xmap, OutputArray ymap)
 {

modules/stitching/test/test_reprojection.cpp

+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+#include "test_precomp.hpp"
+#include "opencv2/stitching/warpers.hpp"
+
+namespace opencv_test { namespace {
+class ReprojectionTest : public ::testing::Test {
+
+protected:
+    const size_t TEST_COUNT = 15;
+    Mat K, R;
+    RNG rng = RNG(0);
+    ReprojectionTest()
+    {
+        K = Mat::eye(3, 3, CV_32FC1);
+        float angle = (float)(30.0 * CV_PI / 180.0);
+        float rotationMatrix[9] = {
+                (float)cos(angle), (float)sin(angle), 0,
+                (float)-sin(angle), (float)cos(angle), 0,
+                0, 0, 1
+        };
+        Mat(3, 3, CV_32FC1, rotationMatrix).copyTo(R);
+    }
+    void TestReprojection(Ptr<detail::RotationWarper> warper, Point2f pt) {
+        Point2f projected_pt = warper->warpPoint(pt, K, R);
+        Point2f reprojected_pt = warper->warpPointBackward(projected_pt, K, R);
+        EXPECT_NEAR(pt.x, reprojected_pt.x, float( 1e-5));
+        EXPECT_NEAR(pt.y, reprojected_pt.y, float( 1e-5));
+    }
+};
+
+
+TEST_F(ReprojectionTest, PlaneWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<PlaneWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, AffineWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<AffineWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, CylindricalWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<CylindricalWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, SphericalWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<SphericalWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, FisheyeWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<FisheyeWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, StereographicWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<StereographicWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, CompressedRectilinearWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<CompressedRectilinearWarper>(1.5f, 1.0f);
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, CompressedRectilinearPortraitWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<CompressedRectilinearPortraitWarper>(1.5f, 1.0f);
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, PaniniWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<PaniniWarper>(1.5f, 1.0f);
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, PaniniPortraitWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<PaniniPortraitWarper>(1.5f, 1.0f);
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, MercatorWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<MercatorWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+TEST_F(ReprojectionTest, TransverseMercatorWarper)
+{
+    Ptr<WarperCreator> creator = makePtr<TransverseMercatorWarper>();
+    for (size_t i = 0; i < TEST_COUNT; ++i) {
+        TestReprojection(creator->create(1), Point2f(rng.uniform(-1.f, 1.f), rng.uniform(-1.f, 1.f)));
+    }
+}
+
+}} // namespace