ENH: Enhanced the problem set building on the image handing and arrays.
Illustrated dtypes, casting and their importance along with an example
using RGBA images. Also introduce edge detection.
str_range = '4-7, 9, 12, 15'
ranges = str_range.split(',')
lst = []
for r in ranges:
vals = r.split('-')
if len(vals) == 2:
lst.extend(range(int(vals[0]), int(vals[1]) + 1))
else:
lst.append(int(vals[0]))
set_range = set(lst)
all_elems = set(range(min(lst), max(lst)))
print all_elems - set_range