Fixed #31766 -- Avoided uncessary computation in GDALRaster

Implemented a clone method using ds_copy to clone GDALRaster objects. Added conditional to simply clone GDALRaster if SRID matches with transform srs argument.

AUTHORS

@@ -110,6 +110,7 @@ answer newbie questions, and generally made Django that much better:
     Baptiste Mispelon <bmispelon@gmail.com>
     Barry Pederson <bp@barryp.org>
     Bartolome Sanchez Salado <i42sasab@uco.es>
+    Barton Ip <notbartonip@gmail.com>
     Bartosz Grabski <bartosz.grabski@gmail.com>
     Bashar Al-Abdulhadi
     Bastian Kleineidam <calvin@debian.org>

django/contrib/gis/gdal/raster/source.py

@@ -425,6 +425,10 @@ def warp(self, ds_input, resampling='NearestNeighbour', max_error=0.0):
 
         return target
 
+    def clone(self):
+        "Return a clone of this GDALRaster object"
+        return GDALRaster(self._ptr, write=self._write)
+
     def transform(self, srs, driver=None, name=None, resampling='NearestNeighbour',
                   max_error=0.0):
         """
@@ -443,6 +447,10 @@ def transform(self, srs, driver=None, name=None, resampling='NearestNeighbour',
                 'Transform only accepts SpatialReference, string, and integer '
                 'objects.'
             )
+
+        if target_srs.srid == self.srid:
+            return self.clone()
+
         # Create warped virtual dataset in the target reference system
         target = capi.auto_create_warped_vrt(
             self._ptr, self.srs.wkt.encode(), target_srs.wkt.encode(),

tests/gis_tests/gdal_tests/test_raster.py

@@ -2,13 +2,15 @@
 import shutil
 import struct
 import tempfile
+from unittest import mock
 
 from django.contrib.gis.gdal import GDAL_VERSION, GDALRaster, SpatialReference
 from django.contrib.gis.gdal.error import GDALException
 from django.contrib.gis.gdal.raster.band import GDALBand
 from django.contrib.gis.shortcuts import numpy
 from django.test import SimpleTestCase
 
+
 from ..data.rasters.textrasters import JSON_RASTER
 
 
@@ -470,6 +472,59 @@ def test_raster_warp_nodata_zone(self):
         # The result is an empty raster filled with the correct nodata value.
         self.assertEqual(result, [23] * 16)
 
+    def test_raster_clone(self):
+        source = GDALRaster({
+            'datatype': 1,
+            'driver': 'MEM',
+            'width': 4,
+            'height': 4,
+            'srid': 3086,
+            'origin': (500000, 400000),
+            'scale': (100, -100),
+            'skew': (0, 0),
+            'bands': [{
+                'data': range(16),
+                'nodata_value': 23,
+            }],
+        })
+
+        clone = source.clone()
+
+        # Test cloned raster has same attributes
+        self.assertEqual(source.name, clone.name)
+        self.assertEqual(source.srs.srid, clone.srs.srid)
+        self.assertEqual(source.width, clone.width)
+        self.assertEqual(source.height, clone.height)
+        self.assertEqual(source.bands[0].datatype(), clone.bands[0].datatype())
+        self.assertAlmostEqual(source.origin[0], clone.origin[0], 3)
+        self.assertAlmostEqual(source.origin[1], clone.origin[1], 3)
+        self.assertAlmostEqual(source.scale[0], clone.scale[0], 3)
+        self.assertAlmostEqual(source.scale[1], clone.scale[1], 3)
+        self.assertEqual(source.skew, clone.skew)
+
+    def test_raster_transform_skips_recalculation(self):
+        with mock.patch.object(GDALRaster, "clone") as clone_func:
+            source = GDALRaster({
+                'datatype': 1,
+                'driver': 'tif',
+                'name': rstfile.name,
+                'width': 5,
+                'height': 5,
+                'nr_of_bands': 1,
+                'srid': 4326,
+                'origin': (-5, 5),
+                'scale': (2, -2),
+                'skew': (0, 0),
+                'bands': [{
+                    'data': range(25),
+                    'nodata_value': ndv,
+                }],
+            })
+
+            target = source.transform(4326)
+
+            self.assertEqual(clone_func.call_count, 1)
+
     def test_raster_transform(self):
         tests = [
             3086,