Normalised cross correlation

[Tony Yu]

On Tue, Mar 20, 2012 at 12:12 PM, Malcolm Reynolds <
malcolm.reynolds at gmail.com> wrote:

>
>> Wow, those results are incredibly different. Yes, please put together a
>> small script to reproduce the different behaviors (ideally, with the matlab
>> result saved as .npy---or if it's easier .mat---file; also, if you can
>> reproduce with a smaller image, that would be great).
>>
>> It'll be easy to check for switched arguments, but the rest might
>> take some time for me to get to. In your original email, it sounded like
>> you have some expertise in template matching; feel free to dig into the
>> code and see if you can spot any errors in the code.
>>
>> Cheers,
>> -Tony
>>
>
> I've quickly whipped up some scripts in both matlab (if you have access to
> that) and python and put them here:
> https://github.com/malcolmreynolds/NCC-test-program - if you don't have
> access to matlab, then the .mat file included should contain the inputs and
> outputs from matlab's normxcorr2. To run it you just need to put any image
> called 'lena.png' in the directory and then I ran 'ipython --pylab -i
> run_ncc.py' at the shell on OS X. You may have your plotting set up a
> different way, or not use pylab, but if all else fails the result images
> are written out as pngs (also included in the repository). With matlab just
> get to the matlab prompt and do "run_ncc".
>
> For reference, this is what I see when using a 256x256 downsampled version
> of the lena image:
> http://img843.imageshack.us/img843/2729/screenshot20120320at155.png (matlab on left, middle and right are python with and without the
> pad_output flag).
>
> I'm afraid I'm definitely not an expert on template matching, but I reckon
> it's pretty crucial to have a good free (&fast!) implementation available
> in numpy/scipy/skimage in order to compete.. I will take a dig through your
> code sometime but unfortunately deadlines are always looming for me.. I'll
> hopefully get a chance this coming weekend.
>
> Thanks for your quick response, let me know if you have any problems with
> the stuff on github.
>
> Malcolm
>

Great. Thanks for putting this together and for the original bug report.
I'll take a look at this soon.... I hope. :)

-Tony
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