Avoid unnecessary conversions in Image.bitmap to make it faster.

pixelocr/image.py

@@ -19,7 +19,6 @@ from io import BytesIO
 
 import numpy as np
 from skimage.io import imread, imsave
-from skimage.color import rgb2gray
 
 from .utils import cached_property, pairwise
 
@@ -156,9 +155,7 @@ class Image(object):
         0 = white (blank) pixel
         1 = black (glyph) pixel
         """
-
-        grayscale = rgb2gray(self.data)
-        return (grayscale < 1).astype('b')
+        return (self.data != 255).any(axis=2)
 
     @cached_property
     def isspace(self):