ImageEnhance.Contrast - is this fishy or what?

Scott David Daniels Scott.Daniels at Acm.Org
Tue Jun 16 21:38:52 CEST 2009


Scott David Daniels wrote:
> roop wrote:
>> I was browsing ImageEnhace.py, and found something that I thought was
>> odd in class Contrast:
>>
>> class Contrast(_Enhance):
>>     "Adjust image contrast"
>>     <broken code>
>> <correct analysis>
> ...
> Good catch [I'll send a copy to the imaging sig].  If you replace class
> ...

Over on image-sig, Fredrik Lundh responded:

 > And the award for finding the oldest bug in PIL goes to... (that code
 > was last touched in 1996).
 >
 > I've checked in a last-second fix for 1.1.7 (to be frozen any day soon
 > now, promise).
 >
 > Thanks /F

Congrats, roop, on getting this discovered just in the nick of time.

The code he uses is:

class Contrast(_Enhance):
     "Adjust image contrast"
     def __init__(self, image):
         self.image = image
         mean = int(ImageStat.Stat(image.convert("L")).mean[0] + 0.5)
         self.degenerate = Image.new("L", image.size,
                                     mean).convert(image.mode)

--Scott David Daniels
Scott.Daniels at Acm.Org



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