Carry nodata in CogMeta, use in compressor

If gdal nodata is configured then use it to pad out input blocks
when needed.

odc/geo/cog/_shared.py

@@ -12,7 +12,7 @@
 
 from ..geobox import GeoBox
 from ..math import align_down_pow2, align_up
-from ..types import Shape2d, SomeShape, shape_, wh_
+from ..types import MaybeNodata, Shape2d, SomeShape, shape_, wh_
 
 # pylint: disable=too-many-locals,too-many-branches,too-many-arguments,too-many-statements,too-many-instance-attributes
 
@@ -63,6 +63,7 @@ class CogMeta:
     compressionargs: Dict[str, Any] = field(default_factory=dict, repr=False)
     gbox: Optional[GeoBox] = None
     overviews: Tuple["CogMeta", ...] = field(default=(), repr=False)
+    nodata: MaybeNodata = None
 
     def _pix_shape(self, shape: Shape2d) -> Tuple[int, ...]:
         if self.axis == "YX":
@@ -134,6 +135,7 @@ def __dask_tokenize__(self):
             self.predictor,
             self.gbox,
             len(self.overviews),
+            self.nodata,
         )
 
 

odc/geo/cog/_tifffile.py

@@ -131,6 +131,7 @@ def _sh(shape: Shape2d) -> Tuple[int, ...]:
             predictor,
             compressionargs=compressionargs,
             gbox=gbox,
+            nodata=nodata,
         )
 
         if idx == 0:
@@ -165,12 +166,13 @@ def _cog_block_compressor(
     encoder: Any = None,
     predictor: Any = None,
     axis: int = 1,
+    fill_value: Union[float, int] = 0,
     **kw,
 ) -> bytes:
     assert block.ndim == len(tile_shape)
     if tile_shape != block.shape:
         pad = tuple((0, want - have) for want, have in zip(tile_shape, block.shape))
-        block = np.pad(block, pad, "constant", constant_values=(0,))
+        block = np.pad(block, pad, "constant", constant_values=(fill_value,))
 
     if predictor is not None:
         block = predictor(block, axis=axis)
@@ -197,12 +199,17 @@ def _mk_tile_compressor(meta: CogMeta) -> Callable[[np.ndarray], bytes]:
     if meta.predictor != 1:
         predictor = TIFF.PREDICTORS[meta.predictor]
 
+    fill_value: Union[float, int] = 0
+    if meta.nodata is not None:
+        fill_value = float(meta.nodata) if isinstance(meta.nodata, str) else meta.nodata
+
     return partial(
         _cog_block_compressor,
         tile_shape=tile_shape,
         encoder=encoder,
         predictor=predictor,
         axis=axis,
+        fill_value=fill_value,
         **meta.compressionargs,
     )