Alfio Castorina

Digital image stabilization by adaptive block motion vectors filtering

This paper presents a robust algorithm for video sequence stabilization. Motion estimation is achieved using block motion vectors. In this way, the motion estimator of the MPEG encoder can be used. The simple use of block motion vectors can give unreliable global motion vectors and so elaborations are done to make the algorithm robust.

High dynamic range imaging for digital still camera: an overview

We present a collection of methods and algorithms able to deal with high dynamic ranges of real pictures acquired by digital engines e.g., charge-coupled device (CCD/CMOS) cameras. An ac- curate image acquisition can be challenging under difficult light con- ditions. A few techniques that overcome dynamic range limitations problems are reported. The presented methods allow the recovery of the original radiance values of the final 8-bit-depth image starting from differently exposed pictures. This allows the capture of both low- and high-light details by merging the various pictures into a single map, thus providing a more faithful description of what the real world scene was. However, in order to be viewed on a common computer monitor, the map needs to be compressed and requan- tized while preserving the visibility of details. The main problem comes from the fact that the contrast of the radiance values is usu- ally far greater than that of the display device. Various related tech- niques are reviewed and discussed.

Contrast image correction method

A method for contrast enhancement is proposed. The algorithm is based on a local and image-dependent exponential cor- rection. The technique aims to correct images that simultaneously present overexposed and underexposed regions. To prevent halo artifacts, the bilateral filter is used as the mask of the exponential correction. Depending on the characteristics of the image (piloted by histogram analysis), an automated parameter-tuning step is intro- duced, followed by stretching, clipping, and saturation preserving treatments. Comparisons with other contrast enhancement tech- niques are presented. The Mean Opinion Score (MOS) experiment on grayscale images gives the greatest preference score for our algorithm.

Natural scenes classification for color enhancement

An innovative solution for automatic color rendition of natural digital images is presented. It is based on an adaptive color correction, driven by a natural scene classifier designed over a wide database of natural digital images used as reference. The perceived quality of the processed images is globally closer to the expected color rendition for a great part of observers, without evident artifacts. A visual comparison with two wide diffused automatic and semi-automatic color enhancement tools is also presented.

A noise reduction filter for full-frame data imaging devices

This paper describes a method for video sequences denoising that exploits extra-information provided by the image sensor. Fixed pattern noise and temporal noise are removed by analyzing a series of lines placed at the top of the imager.

A global enhancement pipeline for low-cost imaging devices

The paper describes a suitable algorithms pipelineable to enhance the picture quality in terms of both measured and perceived quality. The overall pipeline is mainly devoted to improve image acquired by low cost imaging sensors, typically present in consumer devices (i.e. mobile phone, web-cams, PDA, etc). A series of ad-hoc heuristics and techniques have been applied, taking into account main compression artifacts, chromatic and geometric distortions, etc.. Experimental results show effectiveness of the proposed pipeline.

Robust digital image stabilization algorithm using block motion vectors

This paper presents a robust algorithm for the stabilization of video sequences. Motion estimation is done using block motion vectors. In this way the motion estimator of the MPEG encoder can be used. The simple use of block motion vectors can give unreliable global motion vectors and so elaborations are done to make the algorithm robust.

A temporal noise reduction filter based on image sensor full-frame data

This paper describes a temporal filter aimed at the simultaneous cancellation of fixed pattern noise and temporal noise from image sequences by exploiting all the data provided by a typical image sensor (e.g. CCD/CMOS).

Analysis and characterization of JPEG 2000 standard for imaging devices

This paper presents a series of possible improvement strategies and/or implementations related to the JPEG 2000 standard for imaging devices. A comparative study relative to various coding options is presented together with some brief considerations about rate-ctrl techniques and perceptive improvement strategies.

High-dynamic-range imaging for digital still camera

The paper presents a collection of methods and algorithms able to deal with high dynamic range of real pictures acquired by digital engines (e.g. CCD/CMOS cameras). Accurate image acquisition can be not well suited under difficult light conditions. A few techniques that overcome the usual 8 bit-depth representations by using differently exposed pictures and recovering the original radiance values are reported. This allows capturing both low and highlight details, fusing the various pictures into a singe map, thus providing a more faithful description of what the real world scene was. However in order to be viewed on a common computer monitor the map needs to be re-quantized while preserving visibility of details. The main problem comes from the fact that usually the contrast of the radiance values is far greater than that of the display device. Various related techniques are reviewed and discussed.