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- Raymond H. Chan, Chung-Wa Ho, Mila Nikolova
- IEEE Transactions on Image Processing
- 2005

This paper proposes a two-phase scheme for removing salt-and-pepper impulse noise. In the first phase, an adaptive median filter is used to identify pixels which are likely to be contaminated by noise (noise candidates). In the second phase, the image is restored using a specialized regularization method that applies only to those selected noise candidates.… (More)

- Tony F. Chan, Selim Esedoglu, Mila Nikolova
- SIAM Journal of Applied Mathematics
- 2006

We show how certain nonconvex optimization problems that arise in image processing and computer vision can be restated as convex minimization problems. This allows, in particular, the finding of global minimizers via standard convex minimization schemes. 1. Introduction. Image denoising and segmentation are two related, fundamental problems of computer… (More)

- Mila Nikolova
- Journal of Mathematical Imaging and Vision
- 2004

- Mila Nikolova, Michael K. Ng
- SIAM J. Scientific Computing
- 2005

We address the minimization of regularized convex cost functions which are customarily used for edge-preserving restoration and reconstruction of signals and images. In order to accelerate computation, the multiplicative and the additive half-quadratic reformulation of the original cost-function have been pioneered in Geman & Reynolds (1992) and Geman &… (More)

- Mila Nikolova
- SIAM J. Numerical Analysis
- 2002

We present a theoretical study of the recovery of an unknown vector x ∈ I R p (a signal, an image) from noisy data y ∈ I R q by minimizing with respect to x a regularized cost-function F (x, y) = Ψ(x, y) + αΦ(x), where Ψ is a data-fidelity term, Φ is a smooth regularization term and α > 0 is a parameter. Typically, Ψ(x, y) = Ax − y 2 where A is a linear… (More)

- Mila Nikolova
- Multiscale Modeling & Simulation
- 2005

- Mila Nikolova
- Journal of Mathematical Imaging and Vision
- 2004

We focus on the question of how the shape of a cost-function determines the features manifested by its local (and hence global) minimizers. Our goal is to check the possibility that the local minimizers of an unconstrained cost-function satisfy different subsets of affine constraints dependent on the data, hence the word " weak ". A typical example is the… (More)

- Mila Nikolova, Michael K. Ng, Shuqin Zhang, Wai-Ki Ching
- SIAM J. Imaging Sciences
- 2008

We consider the restoration of piecewise constant images where the number of the regions and their values are not fixed in advance, with a good difference of piecewise constant values between neighboring regions, from noisy data obtained at the output of a linear operator (e.g., a blurring kernel or a Radon transform). Thus we also address the generic… (More)

Image deblurring [4] from noisy data is a fundamental problem in image processing. Let the true image x belong to a proper function space S(Ω) on Ω = [0, 1] 2 , and the observed digital image y be a vector in R m×m indexed by A = {1, 2, · · · , m} × {1, 2, · · · , m}. The image degradation can be modeled as y = N (Hx), where H : S(Ω) → R m×m is a linear… (More)

- Mila Nikolova, Michael K. Ng, Chi-Pan Tam
- IEEE Transactions on Image Processing
- 2010

Nonconvex nonsmooth regularization has advantages over convex regularization for restoring images with neat edges. However, its practical interest used to be limited by the difficulty of the computational stage which requires a nonconvex nonsmooth minimization. In this paper, we deal with nonconvex nonsmooth minimization methods for image restoration and… (More)