15 September 2008 System of invariant correlation to rotation using a ring mask
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A new rotational invariance computational filter is presented. The filter was applied to a problem image, in this case, an image of 256 by 256 pixels of black background with a centered white Arial letter. The complete alphabet is represented in those images. The image is rotated one degree by one degree until complete 360 degrees; hence, for each alphabet letter we are generating 360 images. To achieve the rotational invariance, first of all, a translational invariance is applied and then a 256 by 256 binary mask of concentric circular rings of three pixels of thickness and separation is used. The sum of the information in the circular rings represents the signature of the image. The average of the signature of the 360 images of a selected letter is the filter used to compute the phase correlation with all alphabet letter and their rotated images. The confidence level is calculated by the mean value with two standard errors (2SE) of those 360 correlation values for each letter. The confidence level shows that this system works efficiently on the discrimination between letters.
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Selene Solorza, Selene Solorza, Josué Álvarez-Borrego, Josué Álvarez-Borrego, Vitaly Kober, Vitaly Kober, } "System of invariant correlation to rotation using a ring mask", Proc. SPIE 7073, Applications of Digital Image Processing XXXI, 707325 (15 September 2008); doi: 10.1117/12.795086; https://doi.org/10.1117/12.795086

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