PROJStringFormatter: add optimizations useful for IAU CRS transformation pipelines

2 files changed, 46 insertions, 0 deletions

diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 9e7f0580..1f193559 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -7868,6 +7868,32 @@ const std::string &PROJStringFormatter::toString() const {
                 continue;
             }
 
+            // axisswap order=2,-1 followed by axisswap order=-2,1 is a no-op
+            if (curStep.name == "axisswap" && prevStep.name == "axisswap" &&
+                curStepParamCount == 1 && prevStepParamCount == 1 &&
+                !prevStep.inverted &&
+                prevStep.paramValues[0].equals("order", "2,-1") &&
+                !curStep.inverted &&
+                curStep.paramValues[0].equals("order", "-2,1")) {
+                deletePrevAndCurIter();
+                continue;
+            }
+
+            // axisswap order=2,-1 followed by axisswap order=1,-2 is
+            // equivalent to axisswap order=2,1
+            if (curStep.name == "axisswap" && prevStep.name == "axisswap" &&
+                curStepParamCount == 1 && prevStepParamCount == 1 &&
+                !prevStep.inverted &&
+                prevStep.paramValues[0].equals("order", "2,-1") &&
+                !curStep.inverted &&
+                curStep.paramValues[0].equals("order", "1,-2")) {
+                prevStep.inverted = false;
+                prevStep.paramValues[0] = Step::KeyValue("order", "2,1");
+                // Delete this iter
+                iterCur = steps.erase(iterCur);
+                continue;
+            }
+
             // axisswap order=2,1 followed by axisswap order=2,-1 is
             // equivalent to axisswap order=1,-2
             // Same for axisswap order=-2,1 followed by axisswap order=2,1
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 646a990a..4e888f2c 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -7881,6 +7881,26 @@ TEST(io, projstringformatter_axisswap_minus_two_one_followed_two_one) {
 
 // ---------------------------------------------------------------------------
 
+TEST(io, projstringformatter_axisswap_two_minus_one_followed_minus_two_one) {
+    auto fmt = PROJStringFormatter::create();
+    fmt->ingestPROJString("+proj=pipeline "
+                          "+step +proj=axisswap +order=2,-1 "
+                          "+step +proj=axisswap +order=-2,1");
+    EXPECT_EQ(fmt->toString(), "+proj=noop");
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(io, projstringformatter_axisswap_two_minus_one_followed_one_minus_two) {
+    auto fmt = PROJStringFormatter::create();
+    fmt->ingestPROJString("+proj=pipeline "
+                          "+step +proj=axisswap +order=2,-1 "
+                          "+step +proj=axisswap +order=1,-2");
+    EXPECT_EQ(fmt->toString(), "+proj=axisswap +order=2,1");
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(io, projstringformatter_unmodified) {
     const char *const strs[] = {"+proj=pipeline "
                                 "+step +proj=axisswap +order=2,-1 "