How to calculate the ZNCC threshold?

As for choosing a threshold, it is not computed but is something that a user must choose based on comparison with samples that are to be considered alike and those considered different. The ZNCC value lies between -1 and +1. The closer to +1 the greater the similarity.

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Roger Stafford 2015-8-1

Choosing an appropriate threshold value is something that depends on a number of variables: 1) the nature of the imaging system, 2) the typical variations in the scene to be viewed that are to be disregarded versus those of significance, and 3) the degree of certainly the user wishes to have so as not to miss a significant event versus the expense of responding to non-significant events. I see no way of choosing such threshold values that does not involve a careful consideration and experimentation by the user rather than some automatic computation. Would you trust such an automatic method, Remos?

remos remos 2015-8-1

so no means for the choice of the threshold. experimentation is the only way thank you my friend for these kind explanations

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Answer 2

Image Analyst 2015-8-1

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https://ww2.mathworks.cn/matlabcentral/answers/231988-how-to-calculate-the-zncc-threshold#answer_187930

normxcorr2() may do what you want. It normalizes to zero mean and unit standard deviation. See the definition at https://en.wikipedia.org/wiki/Cross-correlation#Normalized_cross-correlation and see if that will work for you.

What do you need to do, and why do you think you need this specialized version of the normalized cross correlation instead of the regular one? Show us your image and template and show us how normxcorr2() fails on your images so we can help you further.