Use URI format for output of precomputed-pyramid

On windows the "C:/" full paths are not supported by
volume-to-precomputed-pyramid.

pytools/ng/mrc2ngpc.py

@@ -18,6 +18,7 @@
 import os.path
 import sys
 import logging
+from pathlib import Path
 
 
 @click.command()
@@ -74,7 +75,8 @@ def main(input_image, output_precompute, flat, gzip):
         if not gzip:
             cmd_opts.append("--no-gzip")
 
-        cmd = ["volume-to-precomputed-pyramid"] + cmd_opts + [nifti_filename, output_precompute]
+        cmd = ["volume-to-precomputed-pyramid"] + cmd_opts + [nifti_filename,
+                                                              Path(output_precompute).as_uri()]
 
         logger.info("Executing conversion of NIFTI to Neruoglancer precompute pyramid...")
         logger.debug(f"Executing: {cmd}")