Fast Fourier Transforms can be used to assist analyis of an image which may possibly be cut into tiles prior to the FFT. FFT is applied to the horizontal and/or vertical sampled pixel intensity values in each tile.

The frequency domain image data from horizontal /vertical slices of each tile thus transformed can have spectral peak detection applied to the data and these peaks compared with the data of other sampled patterns, textures or images allowing them to be identified in each tile of the image.

The optical magnification or rotation of the patterns will result in changes to the positions of the frequency peaks however the relationship ratio-wise between the individual peaks will be maintained and so this method can still provide a reasonable correspondance testing between textures which have been rotated upto at least +-45 degrees,reduced or magnified, as long as the detail in the raw data remains within the niquist sampling frequency limit.

By S.humble

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