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This paper deals with 2-dimentional synthetic aperture radar interferometry. Because of high sensitivity to noise, we propose a two-step phase unwrapping approach. The purpose of preprocessing is to organize the phase by an adaptive filter to improve the estimation of the ground slope vector. The main process smoothes the phase, using the ground slope components, and unwraps the signal. We present...
In this paper, we propose an adaptive scheme to design directional second order derivatives orthogonally and tangentially to the local edge. The principle lies on the definition of two adaptive filter masks which estimate the two derivatives along the normal (n) and tangential (t) directions. Both filter masks are controlled by an adaptive mask whose coefficients are tuned in accordance with the local...
This paper describes a new method for image corner detection based on the curvature scale space (CSS) representation. The first step is to extract edges from the original image using a Canny detector. The Canny detector sometimes leaves a gap in T-junctions so during edge extraction, the gaps are examined to locate the T-junction corner points. The corner points of an image are defined as points where...
A procedure to determine the point spread function (PSF) of a two-dimensional SEM imaging system based on experimental data is presented. The specimen required for capture by the imaging system is simple to manufacture, and only requires a sharp edge to be of use. An overview is given of caveats that exist at each stage of the process, in addition to a breakdown of the process itself. Results based...
The use of connected operator morphology, in particular operators that decompose by area, are examined for the problem of determining dense depth maps from stereo images. It is shown that the use of connected operators can augment and improve conventional processing algorithms. This paper describes how the new algorithm works and presents a comparison of its performance.
In this paper, we present an unsharp masking-based approach for noise smoothing and edge enhancing. And apply it to color image processing. The proposed structure is similar to the conventional unsharp masking structure, however, a nonlinear function is added to control the behavior of the operator. The proposed scheme enhances the true details, limits the overshoot near sharp edges and attenuates...
This work reports and illustrates the application of optimal filtering to enhance sketch contours on infrared photograhies of wood paintings. In [14] the authors tested three approaches of the symmetric exponential filter of an infinitely large window size proposed by Shen and Castan [13]: the DRF, GEF and SDEF filters. The DRF filter presented the best results and was chosen to have a fine tuning...
A number of perceptual distortion measures have been developed for both still images and image sequences. Many of these measures, however, derive from visual experiments using stimuli quite unlike digital image coding artifacts. We present the results from six visual experiments characterizing human visual sensitivity to edge-like blocking artifacts under a number of spatiotemporal conditions, in...
In this paper, a method for automatic detection of linear features in SAR images, with application to road network extraction is proposed. A pre-filtering step is firstly performed using an adaptive directional weighted order filter. It aims to smooth the noise, enhance edges and preserve thin anisotropie structures. Then, the detection operator is applied : it is based on a geometrical model of the...
In this paper we describe a rnicrocalcification detection scheme using non-linear filtering. Our scheme uses a combination of two highly non-linear filters: one for image enhancement, and one for the actual detection of the microcalcifications. Results of our method on the Nijmegen mammographic image database are given.
In this paper, we define and analyse some properties of a class of order filters. These filters can be regarded as adaptive L-Filters which can be tuned by setting only one parameter instead of N, where N is the filter size. Deterministic and statistical properties are discussed. Experimental results obtained on both synthetic and real images show that the noise reduction effect of the new filter...
The concept of cost function (CF) in the context of image filtering is put under investigation in this work. Optimal behaviour of the resulting filters in respect with noise attenuation and edge preservation is sought through the minimization of these functions. This behaviour can be controlled by proper adjustment of certain parameters in some cases. Function combinations are also considered. Finally,...
In this paper, a Markov Random Field (MRF)-based method is presented. MRF methods are based on a probabilistic representation of a image processing problem; the problem is represented as the maximization of a probability measure computed starting from input data for all possible solutions. The optimization process is often computationally expensive. The coupled problem of restoring and extracting...
In image contrast enhancement [2, 4, 5], quadratic and more generally polynomial filters are a very popular class of nonlinear filters. These filters exhibit good performances in terms of visual quality, but present some drawbacks such as the elimination of usefull information when using a fixed filter. In this paper we propose a new family of adaptive quadratic filters, where a weighted filter mask...
A new modification of sigma filter is proposed and tested in this paper. This modification is suitable for processing images corrupted by Gaussian multiplicative and impulsive noises and it avoids some typical disadvantages of the standard sigma filter while possessing robust properties. The test images include both simulated and real radar images. It is seen that the proposed modification provides...
A novel operator for the enhancement of the quality of document images is presented in this paper. This operator, which is a quadratic one, is based on the Unsharp Masking (UM) technique, but it is able to limit noise amplification because every pixel of the processed image depends upon a large portion of the input image; in the same time a good response on details is obtained. A formal description...
In this paper we propose a new adaptive weighted dα filter. The filter is adaptive regarding noise amplitude distribution, orientation of structures and anisotropy measures. The filter coefficient are chosen according to structure orientation and anisotropy measures. α value is chosen according to the result of local noise distribution and anisotropy coefficient estimations. Some experimental results...
A two-dimensional adaptive nonlinear filter, called 2-D FIR-PWL filter is introduced for noise cancellation from images. It is based on the cascade of a linear FIR filter and a piecewise-linear interpolating function. Experimental results show a very good behaviour of the filter, which outperforms in many application examples the Sigma filter both in terms of visual quality and numerical results.
Linear-Nonlinear hybrid filters that have appeared in literature suffer from some severe disadvantages. They smear edges and are very hardware intensive. These shortcomings can be overcome by having a Bit-based Weighted Mean filtering scheme. This filter starts by calculating the median of a set of sample values. The sample values are then scaled. Those values which lie in the proximity of the median,...
We propose a two-stage algorithm for the super-resolution of MR images from their low-frequency k-space samples. In the first stage we estimate a resolution-independent mask whose zeros represent the edges of the image. This builds off recent work extending the theory of sampling signals of finite rate of innovation (FRI) to two-dimensional curves. We enable its application to MRI by proposing extensions...
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