detect and decompress gzipped tile data

python/pmtiles/writer.py

@@ -1,3 +1,4 @@
+import gzip
 import itertools
 import json
 from contextlib import contextmanager
@@ -20,6 +21,10 @@ class Writer:
         self.leaves = []
 
     def write_tile(self,z,x,y,data):
+        # if the tile is GZIP-encoded, it won't work with range queries
+        # until transfer-encoding: gzip is well supported.
+        if data[0:2] == b'\x1f\x8b':
+            data = gzip.decompress(data)
         hsh = hash(data)
         if hsh in self.hash_to_offset:
             self.tiles.append((z,x,y,self.hash_to_offset[hsh],len(data)))