Multiscale: Support project files containing an integer working_scale

All project files created with ilastik1.4.1b13 break otherwise

ilastik/applets/dataSelection/opDataSelection.py

@@ -206,9 +206,20 @@ def from_h5_group(cls, data: h5py.Group, params: Dict = None):
         if "display_mode" in data:
             params["display_mode"] = data["display_mode"][()].decode("utf-8")
         if "working_scale" in data:
-            # This raises if working_scale is an int,
-            # which would be the case if anyone actually created a Precomputed project with ilastik1.4.1b13
-            params["working_scale"] = data["working_scale"][()].decode("utf-8")
+            try:
+                params["working_scale"] = data["working_scale"][()].decode("utf-8")
+            except AttributeError:
+                # Support for projects created with ilastik 1.4.1b13
+                saved_scale = int(data["working_scale"][()])
+                if saved_scale == 0:  # 0 by default (in all project files).
+                    params["working_scale"] = DEFAULT_LOWEST_SCALE_KEY
+                elif saved_scale > 0:  # Precomputed dataset with non-default scale selected
+                    from lazyflow.utility.io_util.RESTfulPrecomputedChunkedVolume import (
+                        RESTfulPrecomputedChunkedVolume as Precomputed,
+                    )
+
+                    url = params["url"]  # Should have url in this case
+                    params["working_scale"] = Precomputed.fetch_scale_key(url, saved_scale)
         if "scale_locked" in data:
             params["scale_locked"] = bool(data["scale_locked"][()])
         return cls(**params)
@@ -587,12 +598,13 @@ def from_h5_group(cls, group: h5py.Group, params: Dict = None):
         """
         Returns a deserialized DatasetInfo dict equivalent to a dict from a MultiscaleUrlDatasetInfo
         """
-        from lazyflow.utility.io_util.RESTfulPrecomputedChunkedVolume import RESTfulPrecomputedChunkedVolume
+        from lazyflow.utility.io_util.RESTfulPrecomputedChunkedVolume import (
+            RESTfulPrecomputedChunkedVolume as Precomputed,
+        )
 
         deserialized = super().from_h5_group(group)
-        remote_source = RESTfulPrecomputedChunkedVolume(deserialized.url.lstrip("precomputed://"))
         deserialized.nickname = cls._nickname_from_url(deserialized.nickname)
-        deserialized.working_scale = remote_source.highest_resolution_key
+        deserialized.working_scale = Precomputed.fetch_scale_key(deserialized.url, "highest")
         deserialized.scale_locked = True
         return deserialized
 

lazyflow/utility/io_util/RESTfulPrecomputedChunkedVolume.py

@@ -21,6 +21,7 @@
 ###############################################################################
 import json
 import logging
+from typing import Union, Literal
 
 import jsonschema
 import numpy
@@ -227,6 +228,19 @@ def generate_url(self, block_coordinates, scale=DEFAULT_LOWEST_SCALE_KEY):
         url = f"{base_url}/{scale}/{min_x}-{max_x}_{min_y}-{max_y}_{min_z}-{max_z}"
         return url, downloaded_block_shape
 
+    @staticmethod
+    def fetch_scale_key(url: str, scale_index: Union[int, Literal["highest"]]):
+        """Support for legacy projects with integer scale indexing.
+        Requests the info file and returns the key of the scale that would have corresponded
+        to the index in legacy versions (i.e. index in the reversed list)."""
+        remote_source = RESTfulPrecomputedChunkedVolume(url.lstrip("precomputed://"))
+        if scale_index == "highest":
+            return remote_source.highest_resolution_key
+        else:
+            assert isinstance(scale_index, int)
+            scales = [s for s in reversed(remote_source._json_info["scales"])]
+            return scales[scale_index]["key"]
+
 
 if __name__ == "__main__":
     logging.basicConfig(level=logging.DEBUG)