1,720,984 research outputs found
An Innovative Display for Medical Applications
No full textInternational Workshop on Image Analysis and Biomechanical Modelling: from Biomolecules to Bioactive Biomaterials.
Trieste 1st-2nd September 200
Dual Layer LCD Display
No full textRiunione Annuale Gruppo Elettronica (GE 2008).
18-20 Giugno 2008, Otranto (LE
Tone mapping and enhancement of high dynamic range images based on a model of visual perception
No full textWe present a new dynamic range compression method for the reproduction of high dynamic range digital images on conventional display devices. The proposed technique is computationally efficient and easily adjustable with few parameters. Novel contributions of this work include an edge preserving smoother for the extraction of the visual adaptation level which avoids the formation of halo artifacts in the resulting image and a technique for contrast mapping which improves the visibility of the image details. The algorithm is finally evaluated by means of an objective measure proving its effectiveness
Fast bilateral filter for edge-preserving smoothing
No full textEdge-preserving lowpass filters are a valuable tool in several image processing tasks, including noise reduction and dynamic range compression. A high-quality algorithm is the bilateral filter, but its computational cost is very high. A fast but approximate implementation was introduced by Durand and Dorsey. Introduced are two modifications in this technique which allow further acceleration and a significant increase in quality
Minimum-Error Splitting Algorithm for a Dual Layer LCD Display—Part II: Implementation and Results
No full textA dual layer LCD display is able to achieve a high dynamic range by stacking two liquid crystal panels one on top of the other over an enhanced backlight unit. However, the finite distance between the two panels inevitably introduces a parallax error when the display is observed off-axis, and the dynamic range limitations of the individual panels introduce a reconstruction error near sharp edges in the input image. In Part I, we have formulated the image splitting as a constrained optimization problem in which a joint minimization of the parallax error and the visibility of the reconstruction error is performed.
In this Part II, we describe one possible numerical method which solves the optimization problem at a low computational cost. We also describe in more detail the characteristics of the prototype display which has been built by FIMI-Philips. We finally present some results and an evaluation of the errors introduced by the proposed splitting algorithm
Minimum-Error Splitting Algorithm for a Dual Layer LCD Display—Part I: Background and Theory
No full textA Dual Layer high dynamic range LCD display can be built by stacking two panels one on top of the other. In this way, the dynamic range is theoretically squared and the bit depth is also increased. Dedicated splitting algorithms are however needed to generate the two images which drive the panels, in order to minimize the parallax and reconstruction errors.
In this paper we present an algorithm, based on variational techniques, which seeks the joint minimization of both errors. We propose a simplified visible difference metric that exploits some limitations of the human visual system and can be easily incorporated into an optimization algorithm. The image splitting task is formulated as a quadratic programming problem, which can be efficiently solved by means of appropriate numerical methods.
Preliminary tests on medical images showed that the algorithm has good performances and appears robust with respect to the parameter adjustment
Color rendering in high dynamic range images
No full textIf a photograph is reproduced “faithfully”, i.e. preserving the relative colorimetric values of the original scene, the resulting image will often look less colorful and less contrasted than the original scene due to some mechanisms of the human visual system. Film and digital cameras must compensate these effects in order to obtain visually pleasing images, which reproduce the appearance of the original scene. This problem occurs also in high dynamic range (HDR) photography, and tone mapped images may appear slightly hazy if the aforementioned visual effects are not compensated. In this paper we shall briefly recall the technique used by most cameras (both film-based and digital) and show one possible theoretical motivation based on a model of brightness perception. We shall then propose a simple technique which compensates the loss of colorfulness and contrast in tone mapped images, and show in particular how this technique can be combined with a tone mapping operator we recently proposed. Finally, we shall compare the results with those produced by a related metho
Image-splitting techniques for a dual-layer high dynamic range LCD display
No full textLiquid crystal displays (LCDs) are replacing analog film in radiology and reducing diagnosis times. Their typical dynamic range, however, can be too low for some applications, and their poor ability to reproduce low-luminance areas represents a critical drawback. The black level of an LCD can be drastically improved by stacking two liquid crystal panels in series. In this way the global transmittance is the pointwise product of the transmittances of the two panels and the theoretical dynamic range is squared. Such a high dynamic range (HDR) display also permits the reproduction of a larger number of gray levels, increasing the bit depth of the device. The two panels, however, are placed at a small distance from each other due to mechanical constraints, and this introduces a parallax error when the display is observed off-axis. A complex, spatially adaptive algorithm is therefore necessary to generate the images used to drive the two panels. We describe the characteristics of a prototype dual-layer HDR display and discuss the issues involved in the image-splitting algorithms. We propose some solutions and analyze their performance, giving a measure of the capabilities and limitations of the device
Effect of case variability on the measurement of reader performance when comparing medical display technologies: application to the study of high-luminance-range displays
No full textPerspective registration and multi-frame super-resolution of license plates in surveillance videos
No full textOne task often encountered in surveillance videos is the recognition of a target—e.g. the license plate of a vehicle. Often, the quality of a single video frame does not permit a reliable recognition. If multiple frames are available, it is possible to combine them in order to generate a single image with lower noise (frame averaging) and/or higher resolution (super-resolution). In order for these techniques to work, it is necessary to accurately estimate the motion of the object of interest in the recorded footage. In this paper, we introduce a method capable of accurately computing the perspective transformation that describes the motion of a planar object. The method minimizes the squared distance between the transformed image and a reference, computed over a user-defined region of interest, and uses the partial derivatives in order to significantly speed up the computation. This approach is inspired by the well known Kanade–Lucas–Tomasi feature tracker
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