Add proj_coordoperation_create_inverse to C API (#1795)

4 files changed, 62 insertions, 0 deletions

diff --git a/scripts/reference_exported_symbols.txt b/scripts/reference_exported_symbols.txt
index e20f29b3..3f4cd51b 100644
--- a/scripts/reference_exported_symbols.txt
+++ b/scripts/reference_exported_symbols.txt
@@ -801,6 +801,7 @@ proj_context_use_proj4_init_rules
 proj_convert_conversion_to_other_method
 proj_coord
 proj_coord_error()
+proj_coordoperation_create_inverse
 proj_coordoperation_get_accuracy
 proj_coordoperation_get_grid_used
 proj_coordoperation_get_grid_used_count
diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index 9db9e5b3..5e2ac522 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -7769,6 +7769,34 @@ PJ *proj_normalize_for_visualization(PJ_CONTEXT *ctx, const PJ *obj) {
 
 // ---------------------------------------------------------------------------
 
+/** \brief Returns a PJ* coordinate operation object which represents the
+ * inverse operation of the specified coordinate operation.
+ *
+ * @param ctx PROJ context, or NULL for default context
+ * @param obj Object of type CoordinateOperation (must not be NULL)
+ * @return a new PJ* object to free with proj_destroy() in case of success, or
+ * nullptr in case of error
+ * @since 6.3
+ */
+PJ *proj_coordoperation_create_inverse(PJ_CONTEXT *ctx, const PJ *obj) {
+
+    SANITIZE_CTX(ctx);
+    auto co = dynamic_cast<const CoordinateOperation *>(obj->iso_obj.get());
+    if (!co) {
+        proj_log_error(ctx, __FUNCTION__,
+                       "Object is not a CoordinateOperation");
+        return nullptr;
+    }
+    try {
+        return pj_obj_create(ctx, co->inverse());
+    } catch (const std::exception &e) {
+        proj_log_debug(ctx, __FUNCTION__, e.what());
+        return nullptr;
+    }
+}
+
+// ---------------------------------------------------------------------------
+
 /** \brief Returns the number of steps of a concatenated operation.
  *
  * The input object must be a concatenated operation.
diff --git a/src/proj.h b/src/proj.h
index fc309542..b8b90277 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -1091,6 +1091,9 @@ int PROJ_DLL proj_coordoperation_get_towgs84_values(PJ_CONTEXT *ctx,
                                                     int value_count,
                                                     int emit_error_if_incompatible);
 
+PJ PROJ_DLL *proj_coordoperation_create_inverse(PJ_CONTEXT *ctx, const PJ *obj);
+
+
 int PROJ_DLL proj_concatoperation_get_step_count(PJ_CONTEXT *ctx,
                                                  const PJ *concatoperation);
 
diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index f87f6589..22e2ac11 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -3486,6 +3486,36 @@ TEST_F(CApi, proj_normalize_for_visualization_on_crs) {
 
 // ---------------------------------------------------------------------------
 
+TEST_F(CApi, proj_coordoperation_create_inverse) {
+
+    auto P = proj_create(
+        m_ctxt, "+proj=pipeline +step +proj=axisswap +order=2,1 +step "
+                "+proj=unitconvert +xy_in=deg +xy_out=rad +step +proj=push "
+                "+v_3 +step +proj=cart +ellps=evrst30 +step +proj=helmert "
+                "+x=293 +y=836 +z=318 +rx=0.5 +ry=1.6 +rz=-2.8 +s=2.1 "
+                "+convention=position_vector +step +inv +proj=cart "
+                "+ellps=WGS84 +step +proj=pop +v_3 +step +proj=unitconvert "
+                "+xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1");
+    ObjectKeeper keeper_P(P);
+    ASSERT_NE(P, nullptr);
+    auto Pinversed = proj_coordoperation_create_inverse(m_ctxt, P);
+    ObjectKeeper keeper_Pinversed(Pinversed);
+    ASSERT_NE(Pinversed, nullptr);
+
+    auto projstr = proj_as_proj_string(m_ctxt, Pinversed, PJ_PROJ_5, nullptr);
+    ASSERT_NE(projstr, nullptr);
+    EXPECT_EQ(std::string(projstr),
+              "+proj=pipeline +step +proj=axisswap +order=2,1 +step "
+              "+proj=unitconvert +xy_in=deg +xy_out=rad +step +proj=push +v_3 "
+              "+step +proj=cart +ellps=WGS84 +step +inv +proj=helmert +x=293 "
+              "+y=836 +z=318 +rx=0.5 +ry=1.6 +rz=-2.8 +s=2.1 "
+              "+convention=position_vector +step +inv +proj=cart "
+              "+ellps=evrst30 +step +proj=pop +v_3 +step +proj=unitconvert "
+              "+xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1");
+}
+
+// ---------------------------------------------------------------------------
+
 TEST_F(CApi, proj_get_remarks) {
     auto co = proj_create_from_database(m_ctxt, "EPSG", "8048",
                                         PJ_CATEGORY_COORDINATE_OPERATION, false,