more tests

rio_tiler/utils.py

@@ -305,6 +305,7 @@ def get_vrt_transform(
         tuple: VRT transform (affine.Affine), width (int) and height (int)
 
     """
+    # 1. Get the Dataset Resolution in the output crs
     if src_dst.crs != dst_crs:
         src_width = src_dst.width
         src_height = src_dst.height
@@ -358,6 +359,7 @@ def get_vrt_transform(
     else:
         dst_transform = src_dst.transform
 
+    # 2. adjust output bounds if needed
     # If bounds window is aligned with the dataset internal tile we align the bounds with the pixels.
     # This is to limit the number of internal block fetched.
     if _requested_tile_aligned_with_internal_tile(src_dst, bounds, bounds_crs=dst_crs):
@@ -384,6 +386,7 @@ def get_vrt_transform(
 
     w, s, e, n = bounds
 
+    # 3. Calculate the VRT Height/Width
     # When no output size (resolution) - Use Dataset Resolution
     # NOTE: When we don't `fix` the output width/height, we're using the reprojected dataset resolution
     # to calculate what is the size/transform of the VRT
@@ -399,16 +402,11 @@ def get_vrt_transform(
         # NOTE: Here we check if the Output Resolution is higher thant the dataset resolution (OverZoom)
         # When not over-zooming we don't want to use the output Width/Height to calculate the transform
         # See issues https://github.com/cogeotiff/rio-tiler/pull/648
-        w_res = (
-            output_transform.a
-            if abs(output_transform.a) < abs(dst_transform.a)
-            else dst_transform.a
-        )
-        h_res = (
-            output_transform.e
-            if abs(output_transform.e) < abs(dst_transform.e)
-            else dst_transform.e
-        )
+        if abs(dst_transform.a) > abs(output_transform.a):
+            w_res = output_transform.a
+
+        if abs(dst_transform.e) > abs(output_transform.e):
+            h_res = output_transform.e
 
     vrt_width = max(1, round((e - w) / w_res))
     vrt_height = max(1, round((s - n) / h_res))

tests/test_reader.py

@@ -495,6 +495,70 @@ def test_part_with_buffer():
     numpy.array_equal(img_no_buffer.data, img.data[:, 2:-2, 2:-2])
 
 
+def test_part_with_buffer_overzoom():
+    """Make sure buffer works as expected."""
+    bounds = [
+        -6574807.42497772,
+        12210356.646387195,
+        -6261721.357121638,
+        12523442.714243278,
+    ]
+    # Read part at full resolution
+    with rasterio.open(COG) as src_dst:
+        img_no_buffer = reader.part(
+            src_dst,
+            bounds,
+            dst_crs=constants.WEB_MERCATOR_CRS,
+            height=2000,
+            width=2000,
+        )
+
+    x_size = img_no_buffer.width
+    y_size = img_no_buffer.height
+
+    x_res = (bounds[2] - bounds[0]) / x_size
+    y_res = (bounds[3] - bounds[1]) / y_size
+
+    nx = x_size + 4
+    ny = y_size + 4
+
+    # apply a 2 pixel buffer
+    bounds_with_buffer = (
+        bounds[0] - x_res * 2,
+        bounds[1] - y_res * 2,
+        bounds[2] + x_res * 2,
+        bounds[3] + y_res * 2,
+    )
+    with rasterio.open(COG) as src_dst:
+        img = reader.part(
+            src_dst,
+            bounds_with_buffer,
+            height=ny,
+            width=nx,
+            dst_crs=constants.WEB_MERCATOR_CRS,
+        )
+        assert img.width == nx
+        assert img.height == ny
+
+    with rasterio.open(COG) as src_dst:
+        imgb = reader.part(
+            src_dst,
+            bounds,
+            buffer=2,
+            dst_crs=constants.WEB_MERCATOR_CRS,
+            height=2000,
+            width=2000,
+        )
+        assert imgb.width == nx
+        assert imgb.height == ny
+
+    assert numpy.array_equal(img.data, imgb.data)
+    assert img.bounds == imgb.bounds
+
+    numpy.array_equal(img_no_buffer.data, imgb.data[:, 2:-2, 2:-2])
+    numpy.array_equal(img_no_buffer.data, img.data[:, 2:-2, 2:-2])
+
+
 def test_read():
     """Test reader.read function."""
     with rasterio.open(COG) as src: