Relax numba requirement to 3.6+

changelogs/master/improved/20200530_glass_blur_perf.md

@@ -2,9 +2,9 @@
 
 This patch improves the performance of
 `imgaug.augmenters.imgcorruptplike.apply_glass_blur()`
-and the corresponding augmenter. The improvement is
-around 14x to 45x, depending on the image size
-(larger images have more speedup).
+and the corresponding augmenter in python 3.6+.
+The improvement is around 14x to 45x, depending on
+the image size (larger images have more speedup).
 
 Added dependencies:
-* `numba`
+* `numba` (requires python 3.6+)

imgaug/augmenters/imgcorruptlike.py

@@ -72,9 +72,13 @@
 import warnings
 
 import numpy as np
-import numba
-import skimage.filters
 import six.moves as sm
+import skimage.filters
+# numba cannot be installed in python <=3.5
+try:
+    import numba
+except ImportError:
+    numba = None
 
 import imgaug as ia
 from .. import dtypes as iadt
@@ -491,7 +495,9 @@ def _apply_glass_blur_imgaug(x, severity=1):
         )
     )
 
-    x = _apply_glass_blur_imgaug_loop(x, iterations, max_delta, dxxdyy)
+    x = _apply_glass_blur_imgaug_loop_dispatcher(
+        x, iterations, max_delta, dxxdyy
+    )
 
     return np.clip(
         skimage.filters.gaussian(x / 255., sigma=sigma, multichannel=True),
@@ -500,8 +506,16 @@ def _apply_glass_blur_imgaug(x, severity=1):
 
 
 # Added in 0.5.0.
-# fastmath seems to slow this down
-@numba.jit(nopython=True, nogil=True)
+def _apply_glass_blur_imgaug_loop_dispatcher(x, iterations, max_delta, dxxdyy):
+    func = _apply_glass_blur_imgaug_loop
+    # numba is None if it could not be imported
+    if numba is not None:
+        # fastmath seems to slow this down
+        func = numba.jit(func, nopython=True, nogil=True)
+    return func(x, iterations, max_delta, dxxdyy)
+
+
+# Added in 0.5.0.
 def _apply_glass_blur_imgaug_loop(
         x, iterations, max_delta, dxxdyy
 ):

requirements.txt

@@ -11,4 +11,5 @@ opencv-python-headless
 imageio<=2.6.1; python_version<'3.5'
 imageio; python_version>='3.5'
 Shapely
-numba
+# numba is not available in <=3.5
+numba; python_version>='3.6'