Christos "TZOTZIOY" Georgiou <[EMAIL PROTECTED]> writes: > A set seems more appropriate in this case: > > color_count = len(set(izip(r, g, b))) # untested code
Well, while potentially premature optimization, I was trying for performance in this case. In Python 2.3, the sets module is coded in Python, and just wraps a dictionary, and when handed an iterable, ends up looping (in Python) with individual dictionary key assignments. Although I didn't specifically test sets, when I did a loop like that myself, it was 5-6 times slower than directly building the dictionary. That might change in 2.4 with the built-in set - it's still a wrapper around dict but knows it's just directly setting items to a true value so can avoid dealing with the tuples that dict does (not to mention I don't have to build the extra tuple). Although I expect the direct support in PIL 1.1.5 that Fredrik posted about will be best. > >For a greyscale, or single banded image, it should be faster just to > >use the built-in PIL "histogram" method and take the length of the > >resulting list. > > More like the count of non-zero elements in the histogram; I believe the > length of the resulting list will be constant (ie 256). Oops, definitely yes. -- David -- http://mail.python.org/mailman/listinfo/python-list
