In this paper we propose a novel color demosaicing algorithm for noisy data. It is assumed that the data is given according to the Bayer pattern and corrupted by signal-dependant noise which is common for CCD and CMOS digital image sensors. Demosaicing algorithms are used to reconstruct missed red, green, and blue values to produce an RGB image. This is an interpolation problem usually called color filter array interpolation (CFAI). The conventional approach used in image restoration chains for the noisy raw sensor data exploits denoising and CFAI as two independent steps. The denoising step comes first and the CFAI is usually designed to perform on noiseless data. In this paper we propose to integrate the denoising and CFAI into one procedure. Firstly, we compute initial directional interpolated estimates of noisy color intensities. Afterward, these estimates are decorrelated and denoised by the special directional anisotropic adaptive filters. This approach is found to be efficient in order to attenuate both noise and interpolation errors. The exploited denoising technique is based on the local polynomial approximation (LPA). The adaptivity to data is provided by the multiple hypothesis testing called the intersection of confidence intervals (ICI) rule which is applied for adaptive selection of varying scales (window sizes) of LPA. We show the efficiency of the proposed approach in terms of both numerical and visual evaluation.
This paper presents a novel multi-channel image restoration algorithm. The main idea is to develop practical approaches to reduce optical blur from noisy observations produced by the sensor of a camera phone. An iterative deconvolution is applied separately to each color channel directly on the raw data obtained from the camera sensor. We use a modified iterative Landweber algorithm combined with an adaptive denoising technique. The employed adaptive denoising is based on Local Polynomial Approximation (LPA) operating on data windows, which are selected by the rule of Intersection of Confidence Intervals (ICI). In order to avoid false coloring due to independent component filtering in RGB space, we have integrated a novel regularization mechanism that smoothly attenuates the high-pass filtering near saturated regions. Through simulations, it is shown that the proposed filtering is robust with respect to errors in point-spread function (PSF) and approximated noise models. Experimental results show that the proposed processing technique produces significant improvement in perceived image resolution.
In this paper, we propose the use of order filters in the iterative process of super-resolution reconstruction. At each iteration, order statistic filters are used to filter and fuse the error images. The signal dependent <i>L</i>-filter structure adjusts its coefficients to achieve edge preservation as well as maximum noise suppression in homogeneous regions. Depending on the amount of variance of the image pixels in different directional masks, the filter switches to use the orientation, which is most likely to follow the image edges. This procedure allows for the incorporation of a directional prior across the iterations. The introduction of a spatial filtering stage into the iterative process of super-resolution attempts to increase the robustness towards motion error and image outliers. Experimental results show the improvement obtained on sequences of noisy text images when motion is exactly known, and when a random motion error is introduced to simulate the real life situation of inaccurate motion estimation.
In this paper, we present a novel approach for describing and estimating similarity of shapes. The target application is content-based indexing and retrieval over large image databases. The shape feature vector is based on the efficient indexing of high curvature (HCP) points which are detected at different levels of resolution of the wavelet transform modulus maxima decomposition. The scale information, together with other topological information of those high curvature points are employed in a sophisticated similarity algorithm. The experimental results and comparisons show that the technique isolates efficiently similar shapes from a large database and reflects adequately the human similarity perception. The proposed algorithm also proved efficient in matching heavily occluded contours with their originals and with other shape contours in the database containing similar portions.