Kai Oistamo

Three-dimensional median-related filters for color image sequence filtering

Most current algorithms developed for image sequence filtering require motion information in order to obtain good results both in the still and moving parts of an image sequence. In the present paper, filters which completely preserve stationary regions in image sequences are introduced. In moving regions, the 3D filters inherently reduce to spatial filters and perform well in these areas without any motion-compensation or motion-detection. A new multivariate filtering operation called the alpha-trimmed vector median is proposed. Guidelines for the determination of optimal 3D median-related structures for color and gray-level image sequence filtering are given. Algorithms based on vector median, extended vector median, alpha-trimmed vector median, and componentwise median operations are developed. Properties of the human visual system are taken into account in the design of filters. Noise attenuation and detail preservation capability of the filters is examined. In particular, the impulsive noise attenuation capability of the filters is analyzed theoretically. Simulation results based on real image sequences are given. >

Vector median filters for complex signal

The authors introduce vector median-type (VM) filters for complex narrowband signals and investigate basic properties of the VM operation. They present and analyze the root structures of the filters. Sinusoidal signals modulated by root signals of standard median filters are shown to be root signals of VM filters. For actual implementation, the authors use vector FIR (finite impulse response)-median hybrid (VFMH) filters. They show that these filters preserve abrupt changes in amplitude and phase. The filters are shown to remove impulsive and Gaussian noise effectively. Examples are given of VM and VFMH performance for complex signals.<<ETX>>

Video signal processing using vector median

In the vector median approach the samples of the vector-valued input signal are processed as vectors as opposed to componentwise scalar processing. The VM-type filters utilize the correlation between different components in video signal. This makes the VM-filters attractive in video signal processing. In this paper the performance of vector median filters for color video signals is investigated. Vector median FIR median hybrid filters (VFMH) for cross luma and cross color cancellation are introduced. In the VFMH filter the vector median operation is combined with linear substructures resulting in improved cross color and cross luma attenuation and in very good noise attenuation.

Vector median operation for color image processing

Vector median-type filters for color video signals are introduced. In the vector median approach the samples of the vector-valued input signal are processed as vectors as opposed to componentwise scalar processing. The VM-type filters utilize the correlation between different components in video signal. Different components in the color video signal correlate strongly. If there is a change in one component, a change is also likely to happen in the other components. This makes the VM-filters attractive in video signal processing. In this paper the performance of vector median filters for color video signals are investigated. Recursive vector median filters for cross luma and cross color cancellation are presented. The vector median operation is combined with linear filtering resulting in improved cross colour and cross luma attenuation and in very good noise attenuation.

Weighted vector median operation for filtering multispectral data

Weighted vector median and weighted extensive vector median operations for filtering multispectral data are proposed. The operations share the good qualities of vector median filters, but allow extra freedom in the filter design. The weights of the input samples are defined as vectors. With this structure the possible difference in the noise statistics in the different signal components can be taken into account. An example of the weighted vector median for color image filtering is given.<<ETX>>

Reconstruction of quincunx-coded image sequences using vector median

A novel method for reconstruction of offset field quincunx coded color image sequences by processing signal components as vectors is presented. A multidimensional weighted vector median interpolation filter is introduced. The suggested interpolation method provides perfect reconstruction of still image areas and has good properties in moving areas of the sequence without any motion information. The performance of the proposed methods is tested using a video sequencer.