[Image-SIG] Odd behavior in PIL 1.1.4 equalization

Fredrik Lundh fredrik at pythonware.com
Thu May 5 11:04:31 CEST 2005

David Kirtley wrote:

> I seem to have found an odd behavior in the equalization.
> I created a series of test images with PIL for a demonstration:
>   a 300x300 RGB image with three bars of gray with offsets of 20 in
> all three channels
>  with starting values of 0 to 200 in steps of 50.
> I expected the equalization routine to move them to 0, 128, 255 as per
> the definition of Histogram Equailzation but to my suprise the
> equalization routine decides to instead
> set them to 0, 85, 170.
> Is this intended functionality? Is this a bug/feature?  :)

looks like an off-by-one error (note that 170+85=255).  should only
cause problems for extreme cases, and should be trivial to fix.

I'll into this for 1.1.6 (patches are welcome).


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