Edit pr 707 (#708)

* Unscale applies each bands scale/offset

* used the wrong shape when setting up the unscaling reshape

* edit PR and change info model

---------

Co-authored-by: Justin Deal <jdeal@aerisweather.com>

CHANGES.md

@@ -1,7 +1,24 @@
 
 # Unreleased
 
+
 * fix type hint for `ImageData.band_names` (author @n8sty, https://github.com/cogeotiff/rio-tiler/pull/704)
+* enable `per-band` scale/offset rescaling (co-author @jddeal, https://github.com/cogeotiff/rio-tiler/pull/707)
+* replace `scale` and `offset` by `scales` and `offsets` in `rio_tiler.models.Info` model
+
+    ```python
+    # before
+    with Reader("tests/fixtures/cog_scale.tif") as src:
+        info = src.info()
+        print(info.scale, info.offset)
+    >> 0.0001 1000.0
+
+    # now
+    with Reader("tests/fixtures/cog_scale.tif") as src:
+        info = src.info()
+        print(info.scales, info.offsets)
+    >> [0.0001, 0.001] [1000.0, 2000.0]
+    ```
 
 # 6.5.0 (2024-05-03)
 

rio_tiler/io/rasterio.py

@@ -265,11 +265,9 @@ def _get_descr(ix):
             "width": self.dataset.width,
             "height": self.dataset.height,
             "overviews": self.dataset.overviews(1),
+            "scales": self.dataset.scales,
+            "offsets": self.dataset.offsets,
         }
-        if self.dataset.scales[0] != 1.0 or self.dataset.offsets[0] != 0.0:
-            meta.update(
-                {"scale": self.dataset.scales[0], "offset": self.dataset.offsets[0]}
-            )
 
         if self.colormap:
             meta.update({"colormap": self.colormap})

rio_tiler/models.py

@@ -77,8 +77,8 @@ class Info(SpatialInfo):
     dtype: str
     nodata_type: Literal["Alpha", "Mask", "Internal", "Nodata", "None"]
     colorinterp: Optional[List[str]] = None
-    scale: Optional[float] = None
-    offset: Optional[float] = None
+    scales: Optional[List[float]] = None
+    offsets: Optional[List[float]] = None
     colormap: Optional[GDALColorMapType] = None
 
     model_config = {"extra": "allow"}

rio_tiler/reader.py

@@ -261,8 +261,13 @@ def read(
 
         if unscale:
             data = data.astype("float32", casting="unsafe")
-            numpy.multiply(data, dataset.scales[0], out=data, casting="unsafe")
-            numpy.add(data, dataset.offsets[0], out=data, casting="unsafe")
+
+            # reshaped to match data
+            scales = numpy.array(dataset.scales).reshape(-1, 1, 1)
+            offsets = numpy.array(dataset.offsets).reshape(-1, 1, 1)
+
+            numpy.multiply(data, scales, out=data, casting="unsafe")
+            numpy.add(data, offsets, out=data, casting="unsafe")
 
         if post_process:
             data = post_process(data)

tests/test_io_rasterio.py

@@ -82,9 +82,8 @@ def test_info_valid():
     """Should work as expected (get file info)"""
     with Reader(COG_SCALE) as src:
         meta = src.info()
-        assert meta["scale"]
-        assert meta.scale
-        assert meta.offset
+        assert meta.scales
+        assert meta.offsets
         assert not meta.colormap
         assert meta.width
         assert meta.height
@@ -113,8 +112,8 @@ def test_info_valid():
         assert meta.dtype == "int16"
         assert meta.colorinterp == ["gray"]
         assert meta.nodata_type == "Nodata"
-        assert meta.scale
-        assert meta.offset
+        assert meta.scales
+        assert meta.offsets
         assert meta.band_metadata
         band_meta = meta.band_metadata[0]
         assert band_meta[0] == "b1"
@@ -439,11 +438,11 @@ def test_Reader_Options():
 
     with Reader(COG_SCALE, options={"unscale": True}) as src:
         p = src.point(310000, 4100000, coord_crs=src.dataset.crs)
-        assert round(float(p.data[0]), 3) == 1000.892
+        numpy.testing.assert_allclose(p.data, [1000.892, 2008.917], atol=1e-03)
 
         # passing unscale in method should overwrite the defaults
         p = src.point(310000, 4100000, coord_crs=src.dataset.crs, unscale=False)
-        assert p.data[0] == 8917
+        numpy.testing.assert_equal(p.data, [8917, 8917])
 
     cutline = "POLYGON ((13 1685, 1010 6, 2650 967, 1630 2655, 13 1685))"
     with Reader(COGEO, options={"vrt_options": {"cutline": cutline}}) as src:

tests/test_reader.py

@@ -429,8 +429,8 @@ def test_point():
         assert pt.band_names == ["b1"]
 
         pt = reader.point(src_dst, [310000, 4100000], coord_crs=src_dst.crs)
-        assert pt.data == numpy.array([8917])
-        assert pt.band_names == ["b1"]
+        numpy.testing.assert_equal(pt.data, [8917, 8917])
+        assert pt.band_names == ["b1", "b2"]
 
         with pytest.raises(PointOutsideBounds):
             reader.point(src_dst, [810000, 4100000], coord_crs=src_dst.crs)
@@ -577,6 +577,8 @@ def test_read():
     # Unscale Dataset
     with rasterio.open(COG_SCALE) as src:
         assert not src.dtypes[0] == numpy.float32
+        assert src.scales == (0.0001, 0.001)
+        assert src.offsets == (1000, 2000)
         img = reader.read(src, unscale=True)
         assert img.data.dtype == numpy.float32