Abstract: The present invention discloses methods for lossless shearing and/or rotation of two-dimensional (2D) data, including digital images, with minute discrete angular increments, carried out only by permutations in the Fourier frequency domain, by exploiting the natural shear occurring as a result of computing a single one-dimensional discrete Fourier transform (DFT) of 2D arrays. Rotations in general, especially for oblong arrays, occur on elliptical paths. Circular rotation, by an angle of arctan(1/width), is achieved on square arrays. When each dimension is multiple of a smaller N, the rotation/shear angle can be increased to arctan(2N/width). Rotation steps can be repeated in long, animation-like series, with neither loss nor degradation of the Fourier content; so much so that tracing the steps back does restore the original data with remarkable precision.

Abstract: The present invention discloses methods for lossless shearing and/or rotation of two-dimensional (2D) data, including digital images, with minute discrete angular increments, carried out only by permutations in the Fourier frequency domain, by exploiting the natural shear occurring as a result of computing a single one-dimensional discrete Fourier transform (DFT) of 2D arrays. Rotations in general, especially for oblong arrays, occur on elliptical paths. Circular rotation, by an angle of arctan(1/width), is achieved on square arrays. When each dimension is multiple of a smaller N, the rotation/shear angle can be increased to arctan(2N/width). Rotation steps can be repeated in long, animation-like series, with neither loss nor degradation of the Fourier content; so much so that tracing the steps back does restore the original data with remarkable precision.

Abstract: A system for collecting, storing and displaying dermatological images for the purpose of monitoring and diagnosis of skin conditions and skin cancers, including melanoma. A hand-held unit illuminates a section of the patient's skin, and an imaging device generates imaging signals from light derived from a skin section. Pairs of light output ports in the hand-held unit are arranged such that their intensity distributions overlap at their half-intensity levels so that the resulting summation of their intensities has a flat central region. Three image stores are maintained, one for lesion images, one for “nearby skin” images, and one for reference-white images. The “nearby skin” images are used by the system software to automatically determine the skin/lesion border. The reference white images are used to set the dynamic range of the instrument and to compensate for lighting irregularities.