[sis] 02/02: Add an `isIdentity()` method and comment.

[de...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

desruisseaux pushed a commit to branch geoapi-4.0
in repository https://gitbox.apache.org/repos/asf/sis.git

commit 2d89bb02e63736b815edeb75a221bc5de87dfc8d
Author: Martin Desruisseaux <ma...@geomatys.com>
AuthorDate: Fri Jan 28 22:23:56 2022 +0100

    Add an `isIdentity()` method and comment.
---
 .../sis/referencing/operation/transform/RotatedPole.java   | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/RotatedPole.java b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/RotatedPole.java
index fb826dd..88bec33 100644
--- a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/RotatedPole.java
+++ b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/RotatedPole.java
@@ -118,6 +118,8 @@ public class RotatedPole extends AbstractMathTransform2D implements Serializable
 
     /**
      * Creates the inverse of the given forward operation.
+     * The new pole latitude is φ<sub>p</sub> = (180° − φ<sub>forward</sub>).
+     * We get this effect be inverting the sign of {@link #cosφp} while keeping {@link #sinφp} unchanged.
      *
      * @see #inverse()
      */
@@ -150,7 +152,7 @@ public class RotatedPole extends AbstractMathTransform2D implements Serializable
                     i = 3 - i;
                 }
                 double value = -((Number) ((ParameterValue<?>) values.get(i)).getValue()).doubleValue();
-                if (i == 0) value = Math.IEEEremainder(value + 180, 360);
+                if (i == 0) value = IEEEremainder(value + 180, 360);
                 target.setValue(value);
                 return true;
             }
@@ -329,6 +331,16 @@ public class RotatedPole extends AbstractMathTransform2D implements Serializable
     }
 
     /**
+     * Tests whether this transform does not move any points.
+     *
+     * @return {@code true} if this transform is (at least approximately) the identity transform.
+     */
+    @Override
+    public boolean isIdentity() {
+        return abs(cosφp) == 1;
+    }
+
+    /**
      * Compares the specified object with this math transform for equality.
      *
      * @param  object  the object to compare with this transform.