add support for packbits compressed images (#54)

* add support for packbits compressed images * update readme
geospatial-jeff · Jun 14, 2020 · ccc1314 · ccc1314
1 parent 9963224
commit ccc1314
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diff --git a/README.md b/README.md
@@ -81,8 +81,7 @@ async with COGReader("https://async-cog-reader-test-data.s3.amazonaws.com/lzw_co
 ```
 
 ### Image Data
-The reader also has methods for reading internal image tiles and performing partial reads.  Currently only jpeg, lzw,
-and webp compressions are supported.
+The reader also has methods for reading internal image tiles and performing partial reads.  Currently only jpeg, lzw, packbits, and webp compressions are supported.
 
 #### Image Tiles
 Reading the top left tile of an image at native resolution:

diff --git a/aiocogeo/compression.py b/aiocogeo/compression.py
@@ -97,4 +97,9 @@ def _deflate(self, tile: bytes) -> np.ndarray:
         """Internal method to decompress DEFLATE image bytes and convert to numpy array"""
         decoded = self._reshape(np.frombuffer(imagecodecs.zlib_decode(tile), self.dtype))
         self._unpredict(decoded)
+        return np.rollaxis(decoded, 2, 0)
+
+    def _packbits(self, tile: bytes) -> np.ndarray:
+        """Internal method to decompress PACKBITS image bytes and convert to numpy array"""
+        decoded = self._reshape(np.frombuffer(imagecodecs.packbits_decode(tile), self.dtype))
         return np.rollaxis(decoded, 2, 0)
diff --git a/aiocogeo/constants.py b/aiocogeo/constants.py
@@ -8,6 +8,7 @@
     6: "jpeg",
     7: "jpeg",
     8: "deflate",
+    32773: "packbits",
     50001: "webp",
 }
 

diff --git a/tests/conftest.py b/tests/conftest.py
@@ -23,6 +23,7 @@
     "https://async-cog-reader-test-data.s3.amazonaws.com/naip_image_nodata.tif",
     "https://async-cog-reader-test-data.s3.amazonaws.com/naip_image.tif",
     "https://async-cog-reader-test-data.s3.amazonaws.com/naip_image_masked.tif",
+    "http://async-cog-reader-test-data.s3.amazonaws.com/packbits_cog.tif",
     "https://async-cog-reader-test-data.s3.amazonaws.com/int16_deflate.tif",
     os.path.join(DATA_DIR, "cog.tif"),
 ]