backup

Author: konstntokas

xcube_resampling/affine.py

@@ -26,13 +26,15 @@
 import numpy as np
 import xarray as xr
 from dask_image import ndinterp
+import pyproj
 
 from .constants import (
     AffineTransformMatrix,
     AggFunction,
     FillValues,
     FloatInt,
     PreventNaNPropagations,
+    SCALE_LIMIT,
     SpatialAggMethods,
     SpatialInterpMethodInt,
     SpatialInterpMethods,
@@ -44,6 +46,7 @@
     _get_prevent_nan_propagation,
     _get_spatial_agg_method,
     _get_spatial_interp_method_int,
+    _prep_spatial_interp_methods_downscale,
     _select_variables,
     normalize_grid_mapping,
 )
@@ -243,6 +246,49 @@ def resample_dataset(
     return xr.Dataset(data_vars=data_vars, coords=coords, attrs=dataset.attrs)
 
 
+def _downscale_source_dataset(
+    source_ds: xr.Dataset,
+    source_gm: GridMapping,
+    target_gm: GridMapping,
+    interp_methods: SpatialInterpMethods | None,
+    agg_methods: SpatialAggMethods | None,
+    prevent_nan_propagations: PreventNaNPropagations,
+    transformer: pyproj.Transformer | None = None,
+) -> (xr.Dataset, GridMapping):
+    if interp_methods in [0, "nearest"]:
+        return source_ds, source_gm
+
+    if transformer is None:
+        target_xres = target_gm.x_res
+        target_yres = target_gm.y_res
+    else:
+        target_bbox = transformer.transform_bounds(*target_gm.xy_bbox)
+        target_xres = (target_bbox[2] - target_bbox[0]) / target_gm.width
+        target_yres = (target_bbox[3] - target_bbox[1]) / target_gm.height
+
+    x_scale = source_gm.x_res / target_xres
+    y_scale = source_gm.y_res / target_yres
+    if x_scale >= SCALE_LIMIT and y_scale >= SCALE_LIMIT:
+        return source_ds, source_gm
+
+    w, h = np.floor(x_scale * source_gm.width), np.floor(y_scale * source_gm.height)
+    downscaled_size = (w if w >= 2 else 2, h if h >= 2 else 2)
+
+    source_ds = resample_dataset(
+        source_ds,
+        ((1 / x_scale, 0, 0), (0, 1 / y_scale, 0)),
+        (source_gm.xy_dim_names[1], source_gm.xy_dim_names[0]),
+        downscaled_size,
+        source_gm.tile_size,
+        _prep_spatial_interp_methods_downscale(interp_methods),
+        agg_methods,
+        prevent_nan_propagations,
+    )
+    source_gm = GridMapping.from_dataset(source_ds)
+
+    return source_ds, source_gm
+
+
 def _resample_array(
     array: da.Array,
     affine_matrix: AffineTransformMatrix,