remove dependency on opencv-python (#126)

* remove dependency on `opencv-python`

* apply `flake8` fixes

* add change log entry

* update dependencies

CHANGES.rst

@@ -5,7 +5,7 @@ General
 -------
 
 - Moved build configuration from ``setup.cfg`` to ``pyproject.toml`` to support PEP621 [#95]
-
+- made dependency on ``opencv-python`` conditional [#126]
 
 ramp_fitting
 ~~~~~~~~~~~~

pyproject.toml

@@ -15,7 +15,6 @@ dependencies = [
     'astropy >=5.0.4',
     'scipy >=1.6.0',
     'numpy >=1.17',
-    'opencv-python >=4.6.0.66',
 ]
 dynamic = ['version']
 
@@ -36,6 +35,9 @@ test = [
     'pytest-doctestplus',
     'pytest-openfiles >=0.5.0',
 ]
+opencv = [
+    'opencv-python >=4.6.0.66',
+]
 
 [project.urls]
 'repository' = 'https://github.com/spacetelescope/stcal'

src/stcal/jump/jump.py

@@ -1,12 +1,22 @@
 import time
 import logging
+import warnings
+
 import numpy as np
-import cv2 as cv
 from . import twopoint_difference as twopt
 from . import constants
 
 import multiprocessing
 
+try:
+    import cv2 as cv
+
+    OPENCV_INSTALLED = True
+except ImportError:
+    OPENCV_INSTALLED = False
+    warnings.warn('Could not import `opencv-python`; '
+                  'certain snowball detection and usage of ellipses will be inoperable')
+
 log = logging.getLogger(__name__)
 log.setLevel(logging.DEBUG)
 

tests/test_jump.py

@@ -1,17 +1,21 @@
-import pytest
 import numpy as np
+import pytest
 from astropy.io import fits
 
 from stcal.jump.jump import flag_large_events, find_circles, find_ellipses
 
+DQFLAGS = {'JUMP_DET': 4, 'SATURATED': 2, 'DO_NOT_USE': 1}
 
+try:
+    import cv2 as cv
 
-DQFLAGS = {'JUMP_DET': 4, 'SATURATED': 2, 'DO_NOT_USE': 1}
+    OPENCV_INSTALLED = True
+except ImportError:
+    OPENCV_INSTALLED = False
 
 
 @pytest.fixture(scope='function')
 def setup_cube():
-
     def _cube(ngroups, readnoise=10):
         nints = 1
         nrows = 204
@@ -27,6 +31,7 @@ def _cube(ngroups, readnoise=10):
     return _cube
 
 
+@pytest.mark.skipif(not OPENCV_INSTALLED, reason="`opencv-python` not installed")
 def test_find_simple_circle():
     plane = np.zeros(shape=(5, 5), dtype=np.uint8)
     plane[2, 2] = DQFLAGS['JUMP_DET']
@@ -38,6 +43,7 @@ def test_find_simple_circle():
     assert circle[0][1] == pytest.approx(1.0, 1e-3)
 
 
+@pytest.mark.skipif(not OPENCV_INSTALLED, reason="`opencv-python` not installed")
 def test_find_simple_ellipse():
     plane = np.zeros(shape=(5, 5), dtype=np.uint8)
     plane[2, 2] = DQFLAGS['JUMP_DET']
@@ -49,9 +55,10 @@ def test_find_simple_ellipse():
     plane[2, 4] = DQFLAGS['JUMP_DET']
     plane[3, 3] = DQFLAGS['JUMP_DET']
     ellipse = find_ellipses(plane, DQFLAGS['JUMP_DET'], 1)
-    assert ellipse[0][2] == pytest.approx(45.0, 1e-3) # 90 degree rotation
+    assert ellipse[0][2] == pytest.approx(45.0, 1e-3)  # 90 degree rotation
     assert ellipse[0][0] == pytest.approx((2.5, 2.0))  # center
 
+
 @pytest.mark.skip(reason="only for local testing")
 def test_single_group():
     inplane = fits.getdata("jumppix.fits")
@@ -61,4 +68,3 @@ def test_single_group():
                       min_jump_area=15, max_offset=1, expand_factor=1.1, use_ellipses=True,
                       sat_required_snowball=False)
     fits.writeto("jumppix_expand.fits", indq, overwrite=True)
-