Abstract: Various examples are directed to apparatus and methods for enhancing an X-ray medical image. In one example, a method for X-ray dental images enhancement is provided. The method includes receiving an input image and applying the noise reduction trough Recursive Locally-Adaptive Wiener Filtration (RLA-WF) based on the sliding window, which is calculated following a recursive two-dimensional scheme; contrast enhancement to the filtered image, including using recursive Sliding Window Contrast Limited Adaptive Histogram Equalization (SW-CLAHE) utilizing a Truncation Threshold Surface (TTS) for calculation of the truncation threshold for the local histogram in each sliding window. The method also includes applying sharpness enhancement to the input image, including using Fast Recursive Adaptive Unsharp Masking (FRA-UM) utilizing a sliding window with two or one-dimensional recursion, to obtain a sharpened image.

Abstract: An apparatus and method for lossless run-length data encoding is disclosed. In the first stage of the method, an input data sequence is transformed without increasing its volume in order to obtain long sequences of identical digits. In the second stage, every such sequence is replaced with a unique shorter sequence. The compressed data is decoded performing corresponding inverse operations. The method is very efficient for compression of some classes of digital images with long sequences of the same number, such as graphics, texts, signatures, and fingerprints.

Abstract: Disclosed is a method and system for digital watermarking of multimedia signals. The input multimedia signal is represented using an inverse difference pyramid decomposition. Spectrum coefficients may be calculated for each level of the pyramid using a new kind of complex Hadamard transform, the matrix of which is distinguished from the known ones by the fact that only one-fourth of its coefficients are complex numbers. The phases of a previously selected part of the low-frequency coefficients are modified with the watermark data, limiting the angles of the phase changes in a gap of several degrees only. After an inverse complex Hadamard Transform, the values of the coefficients from all pyramid levels are summed up and the result is the watermarked signal. The watermark can contain multiple independent levels for each level of the pyramid.