client: clean up required Python packages

* Packages that are only used in testing or development
have been moved to `dev-requirements.txt`
* Closes #178
* Minor rewrite to drop the `scikit-image` package, which
saves around 200MB in install size

server/dev-requirements.txt

@@ -0,0 +1,4 @@
+pytest>=2.9.1
+pytest-cov>=2.2.1
+freezegun>=0.3.6
+pycodestyle>=2.0.0

server/requirements.txt

@@ -1,16 +1,12 @@
 alembic>=0.8.5
 pyyaml>=3.11
-psycopg2>=2.6.1
+psycopg2-binary>=2.6.1
 SQLAlchemy>=1.0.12
-pytest>=2.9.1
-pytest-cov>=2.2.1
-freezegun>=0.3.6
 coloredlogs==5.0
-pycodestyle>=2.0.0
-scipy>=0.18.1
 elasticsearch>=5.0.0
 elasticsearch-dsl>=5.0.0
-scikit-image>=0.12
+numpy>=1.8.2
+pillow>=4.3.0
 pynacl>=1.2.1
 pytz>=2018.3
-pyRFC3339>=1.0
+pyRFC3339>=1.0

server/szurubooru/func/image_hash.py

@@ -5,7 +5,6 @@ from typing import Any, Optional, Tuple, Set, List, Callable
 import elasticsearch
 import elasticsearch_dsl
 import numpy as np
-from skimage.color import rgb2gray
 from PIL import Image
 from szurubooru import config, errors
 
@@ -41,8 +40,7 @@ def _get_session() -> elasticsearch.Elasticsearch:
 
 def _preprocess_image(content: bytes) -> NpMatrix:
     img = Image.open(BytesIO(content))
-    img = img.convert('RGB')
-    return rgb2gray(np.asarray(img, dtype=np.uint8))
+    return np.asarray(img.convert('L'), dtype=np.uint8)
 
 
 def _crop_image(