Fix import in example and make a little more usable.

examples/inference.py

 #!/usr/bin/python
 
 """
-Usage: python dense_inference.py image annotations output
-
 Adapted from the original C++ example: densecrf/examples/dense_inference.cpp
 http://www.philkr.net/home/densecrf Version 2.2
 """
 
 import numpy as np
 import cv2
-import densecrf as dcrf
+import pydensecrf.densecrf as dcrf
 from skimage.segmentation import relabel_sequential
 import sys
 
+if len(sys.argv) != 4:
+    print("Usage: python {} IMAGE ANNO OUTPUT".format(sys.argv[0]))
+    print("")
+    print("IMAGE and ANNO are inputs and OUTPUT is where the result should be written.")
+    sys.exit(1)
+
 img = cv2.imread(sys.argv[1], 1)
 labels = relabel_sequential(cv2.imread(sys.argv[2], 0))[0].flatten()
 output = sys.argv[3]

examples/utils_example.py

 """
-Usage: python util_inference_example.py image annotations
-
-Adapted from the dense_inference.py to demonstate the usage of the util
-functions.
+Adapted from the inference.py to demonstate the usage of the util functions.
 """
 
 import sys
@@ -15,6 +12,10 @@ from skimage.segmentation import relabel_sequential
 from pydensecrf.utils import compute_unary, create_pairwise_bilateral, \
     create_pairwise_gaussian
 
+if len(sys.argv) != 3:
+    print("Usage: python {} IMAGE ANNO".format(sys.argv[0]))
+    sys.exit(1)
+
 fn_im = sys.argv[1]
 fn_anno = sys.argv[2]