Talk:Structure tensor: Difference between revisions

Revision as of 18:28, 13 July 2010

Revision as of 15:45, 19 August 2010

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* This article appears to have been taken from this page, almost verbatim: http://www.cs.cmu.edu/~sarsen/structureTensorTutorial/ [[Special:Contributions/147.4.36.7|147.4.36.7]] ([[User talk:147.4.36.7|talk]]) <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|undated]] comment added 18:27, 13 July 2010 (UTC).</span><!--Template:Undated--> <!--Autosigned by SineBot-->

== Bogus theory? ==

The discussion about the eigenvalues and eigenvectors of this "structure tensor" seems to be nonsense.<br/> The eigenvectors of the matrix S are the direction of the gradient and the same rotated 90 degrees. The eigenvalues are simply <math>\lambda_1 = I_x^2 + I_y^2</math> (the square of the gradient modulus) and <math>\lambda_2 = 0</math>, as one can check by the definitions. Thus the "coherence index" is simply "gradient != (0,0)". So what is the point of all this mathematical mumbo-jumbo (other than to publish a few more papers)?<br/>This phrase seems to be meaningless,too: "A significant difference between a tensor and a matrix, which is also an array, is that a tensor represents a physical quantity the measurement of which is no more influenced by the coordinates with which one observes it than one can account for it." The matrix S obviously depends on the coordinate system.<br/>--[[User:Jorge Stolfi|Jorge Stolfi]] ([[User talk:Jorge Stolfi|talk]]) 15:45, 19 August 2010 (UTC)