I saw that in the docs.<br><br>In my opinion that bit, and the cited paper, are not enough for users to understand what needs to be done. The fact is that it confused me, and apparently others as well, and the cost of this confusion was big. <br>
<br>I suggested a few solutions:<br>1. Change the metric to go down.<br>2. Add a flag to all image metrics that says which way they go.<br>3. Clarify the metric direction in the docs.<br><br>You say #1 is impossible since it might break old code, and I agree. (reluctantly... :) <br>
#2 is best, I think, since it would allow both kinds of metrics to be plugged into the same framework.<br>#3 is probably worst, because it would only solve the problem in this particular metric, and it would still leave room for user errors.<br>
<br>Having read the code, I got the feeling that no one has used this metric successfully. Sadly, I can't actually PROVE it now with a smoking gun. I'm curious to know if there is any reader out there who uses this metric. I'm not saying that we have a license to break it, I'm just giving you some background about how I feel about this metric. In my opinion, it's not on par with the rest of ITK, with regards to documentation, test cases, and code quality.<br>
<br>I wish this thread wouldn't end with the conclusion that everything is
perfect just the way it is. Would someone please acknowledge that there
is a problem?<br><br>Regards,<br><br>- Aviv<br><br><br><div class="gmail_quote">On Thu, Jun 26, 2008 at 1:17 PM, Hauke Heibel <<a href="mailto:heibel@cs.tum.edu">heibel@cs.tum.edu</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Aviv Hurvitz wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
All the metrics I know in ITK go "down". There was no special documentation, ...<br>
</blockquote>
As a matter of fact there is. Take a look at <a href="http://www.itk.org/Doxygen34/html/classitk_1_1GradientDifferenceImageToImageMetric.html" target="_blank">http://www.itk.org/Doxygen34/html/classitk_1_1GradientDifferenceImageToImageMetric.html</a><br>
It states "after passing the squared difference through a function of type 1/(1+x)".<br>
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And I would not expect the functionality to change since there are many people who got the usage right and whose code would break if the class's functionality would change.<br>
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- Hauke<br><font color="#888888">
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Tim Hauke Heibel<br>
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