Merge pull request #154 from google:translate_origin

PiperOrigin-RevId: 621238114

xee/ext.py

@@ -240,7 +240,7 @@ def __init__(
     default_scale = self.SCALE_UNITS.get(self.scale_units, 1)
     if scale is None:
       scale = default_scale
-    default_transform = affine.Affine.scale(scale, -1 * scale)
+    default_transform = affine.Affine.scale(scale, scale)
 
     transform = affine.Affine(*proj.get('transform', default_transform)[:6])
     self.scale_x, self.scale_y = transform.a, transform.e
@@ -420,13 +420,25 @@ def project(self, bbox: types.BBox) -> types.Grid:
         appropriate region of data to return according to the Array's configured
         projection and scale.
     """
-    # The origin of the image is in the top left corner. X is the minimum value
-    # and Y is the maximum value.
-    x_origin, _, _, y_origin = self.bounds  # x_min, x_max, y_min, y_max
+    x_min, y_min, x_max, y_max = self.bounds
     x_start, y_start, x_end, y_end = bbox
     width = x_end - x_start
     height = y_end - y_start
 
+    # Find the actual coordinates of the first or last point of the bounding box
+    # (bbox) based on the positive and negative scale in the actual Earth Engine
+    # (EE) image. Since EE bounding boxes can be flipped (negative scale), we
+    # cannot determine the origin (transform translation) simply by identifying
+    # the min and max extents. Instead, we calculate the translation by
+    # considering the direction of scaling (positive or negative) along both
+    # the x and y axes.
+    translate_x = self.scale_x * x_start + (
+        x_min if self.scale_x > 0 else x_max
+    )
+    translate_y = self.scale_y * y_start + (
+        y_min if self.scale_y > 0 else y_max
+    )
+
     return {
         # The size of the bounding box. The affine transform and project will be
         # applied, so we can think in terms of pixels.
@@ -435,11 +447,8 @@ def project(self, bbox: types.BBox) -> types.Grid:
             'height': height,
         },
         'affineTransform': {
-            # Since the origin is in the top left corner, we want to translate
-            # the start of the grid to the positive direction for X and the
-            # negative direction for Y.
-            'translateX': x_origin + self.scale_x * x_start,
-            'translateY': y_origin + self.scale_y * y_start,
+            'translateX': translate_x,
+            'translateY': translate_y,
             # Define the scale for each pixel (e.g. the number of meters between
             # each value).
             'scaleX': self.scale_x,

xee/ext_integration_test.py

@@ -338,8 +338,8 @@ def test_open_dataset__sanity_check(self):
     ds = self.entry.open_dataset(
         pathlib.Path('LANDSAT') / 'LC08' / 'C01' / 'T1',
         drop_variables=tuple(f'B{i}' for i in range(3, 12)),
-        scale=25.0,  # in degrees
         n_images=3,
+        projection=ee.Projection('EPSG:4326', [25, 0, 0, 0, -25, 0]),
     )
     self.assertEqual(dict(ds.dims), {'time': 3, 'lon': 14, 'lat': 7})
     self.assertNotEmpty(dict(ds.coords))
@@ -352,6 +352,24 @@ def test_open_dataset__sanity_check(self):
       self.assertFalse(v.isnull().all(), 'All values are null!')
       self.assertEqual(v.shape, (3, 14, 7))
 
+  def test_open_dataset__sanity_check_with_negative_scale(self):
+    ds = self.entry.open_dataset(
+        pathlib.Path('LANDSAT') / 'LC08' / 'C01' / 'T1',
+        drop_variables=tuple(f'B{i}' for i in range(3, 12)),
+        scale=-25.0,  # in degrees
+        n_images=3,
+    )
+    self.assertEqual(dict(ds.dims), {'time': 3, 'lon': 14, 'lat': 7})
+    self.assertNotEmpty(dict(ds.coords))
+    self.assertEqual(
+        list(ds.data_vars.keys()),
+        [f'B{i}' for i in range(1, 3)] + ['BQA'],
+    )
+    for v in ds.values():
+      self.assertIsNotNone(v.data)
+      self.assertTrue(v.isnull().all(), 'All values must be null!')
+      self.assertEqual(v.shape, (3, 14, 7))
+
   def test_open_dataset__n_images(self):
     ds = self.entry.open_dataset(
         pathlib.Path('LANDSAT') / 'LC08' / 'C01' / 'T1',
@@ -516,9 +534,9 @@ def test_write_projected_dataset_to_raster(self):
       ds = xr.open_dataset(
           col,
           engine=xee.EarthEngineBackendEntrypoint,
-          scale=10,
           crs=crs,
           geometry=geom,
+          projection=ee.Projection('EPSG:4326', [10, 0, 0, 0, -10, 0]),
       )
 
       ds = ds.isel(time=0).transpose('Y', 'X')
@@ -553,8 +571,8 @@ def test_write_dataset_to_raster(self):
       ds = xr.open_dataset(
           col,
           engine=xee.EarthEngineBackendEntrypoint,
-          scale=0.0025,
           geometry=geom,
+          projection=ee.Projection('EPSG:4326', [0.0025, 0, 0, 0, -0.0025, 0]),
       )
 
       ds = ds.isel(time=0).transpose('lat', 'lon')