Giovanni Ramponi

Image enhancement via adaptive unsharp masking

This paper presents a new method for unsharp masking for contrast enhancement of images. The approach employs an adaptive filter that controls the contribution of the sharpening path in such a way that contrast enhancement occurs in high detail areas and little or no image sharpening occurs in smooth areas.

Nonlinear unsharp masking methods for image contrast enhancement

In the unsharp masking approach for image enhancement, a fraction of the highpass filtered version of the image is added to the original image to form the enhanced version. The method is simple, but it suffers from two serious drawbacks. First, it enhances the contrast in the darker areas perceptually much more strongly than that in the lighter areas. Second, it enhances the noise and/or digitization effects, particularly in the darker regions, resulting in visually less pleasing enhanced images. In general, noise can be suppressed with lowpass filters, which are associated with the blurring of the edges. On the other hand, contrast can be enhanced with highpass filters, which are associated with noise amplification. A reasonable solution, therefore, is to use suitable nonlinear filters which combine the features of both highpass and lowpass filters. This paper outlines several new methods of unsharp masking based on the use of such nonlinear filters. Computer simulations have verified the superior results obtained using these filters. In addition, a new measure of contrast enhancement is introduced which quantitatively supports the improvement obtained using the proposed methods.

A simple edge-sensitive image interpolation filter

A novel scheme for edge-preserving image interpolation is introduced, which is based on the use of a simple nonlinear filter which accurately reconstructs sharp edges. Simulation results show the superior performances of the proposed approach with respect to other interpolation techniques.

Warped distance for space-variant linear image interpolation

The problem of image interpolation using linear techniques is dealt with in this paper. Conventional space-invariant methods are revisited and changed into space-variant ones, by introducing the concept of the warped distance among the pixels of an image. A better perceptual rendition of the image details is obtained in this way; this effect is proved both via the evaluation of the response to an idealized sigmoidal edge model and with experiments on real-world images. The computational costs of the proposed approach are very small when compared to those of state-of-the art nonlinear interpolation operators.

A method for motion adaptive frame rate up-conversion

A frame interpolation algorithm for frame rate up-conversion of progressive image sequences is proposed. The algorithm is based on simple motion compensation and linear interpolation. A motion vector is searched for each pixel in the interpolated image and the resulting motion field is median filtered to remove inconsistent vectors. Averaging along the motion trajectory is used to produce the interpolated pixel values. The main novelty of the proposed method is the motion compensation algorithm which has been designed with low computational complexity as an important criterion. Subsampled blocks are used in block matching and the vector search range is constrained to the most likely motion vectors. Simulation results show that good visual quality has been obtained with moderate complexity. The algorithm has been designed mainly for 50 Hz to 75 Hz frame rate up-conversion with applications in a multimedia environment, but it can also be used in advanced television receivers to remove artifacts due to low scan rate.

A cubic unsharp masking technique for contrast enhancement

Abstract The cubic unsharp masking method is introduced in this paper. It is demonstrated, through both a statistical study and some computer simulations, that the proposed method has a much reduced noise sensitivity with respect to the linear unsharp masking technique and it permits to obtain perceptually pleasant results. The proposed operator also compares favourably with other algorithms which recently have been studied to improve the behaviour of the unsharp masking approach.

A fuzzy operator for the enhancement of blurred and noisy images

Rule-based fuzzy operators are a novel class of operators specifically designed in order to apply the principles of approximate reasoning to digital image processing. This paper shows how a fuzzy operator that is able to perform detail sharpening but is insensitive to noise can be designed. The results obtainable by the proposed technique in the enhancement of a real image are presented.

Design And Real-time Implementation Of A 3-D Rational Filter For Edge Preserving Smoothing

A nonlinear spatio-temporal filter capable of significantly attenuating noise in image sequences without corrupting image details is presented. The characteristics of the filter are described, and the results of several simulations on real-world sequences are shown. A real-time implementation of the algorithm on a last generation DSP is also described. It is shown that, by suitably exploiting the computational capability of the DSP, it is possible to process CIF images at 10 frames/sec.

Fuzzy methods for multisensor data fusion

This paper presents a new general framework for information fusion based on fuzzy methods. In the proposed architecture, feature extraction and feature fusion are performed by adopting a class of (possibly multidimensional) membership functions which take care of the possibility and admissibility of the feature itself. Test cases of one-dimensional and image data fusion are presented. >

Nonlinear fuzzy operators for image processing

Abstract The formal rules which describe the behavior of a ‘globally fuzzy’ technique for image processing are described in this paper. The analysis is then particularized, in order to get a deeper insight, to the case of a very simple operator of this family, putting to evidence the different sources of nonlinearity which are involved. Some examples briefly illustrating the achievable performances complete the presentation.