High Dynamic Range Imaging Technology.

Abstract: In this lecture note, we describe high dynamic range (HDR) imaging systems. Such systems are able to represent luminances of much larger brightness and, typically, a larger range of colors than conventional standard dynamic range (SDR) imaging systems. The larger luminance range greatly improves the overall quality of visual content, making it appear much more realistic and appealing to observers. HDR is one of the key technologies in the future imaging pipeline, which will change the way the digital visual content is represented and manipulated today

High-order wavelet reconstruction for multi-scale edge aware tone mapping

This paper presents a High Order Reconstruction (HOR) method for improved multi-scale edge aware tone mapping. The study aims to contribute to the improvement of edge-aware techniques for smoothing an input image, while keeping its edges intact. The proposed HOR methods circumvent limitations of the existing state of the art methods, e.g., altering the image structure due to changes in contrast; remove artefacts around edges; as well as reducing computational complexity in terms of implementation and associated computational costs. In particular, the proposed method aims at reducing the changes in the image structure by intrinsically enclosing an edge-stop mechanism whose computational cost is comparable to the state-of-the-art multi-scale edge aware techniques

Subjective quality assessment database of HDR images compressed with JPEG XT

Recent advances in high dynamic range (HDR) capturing and display technologies attracted a lot of interest to HDR imaging. Many issues that are considered as being resolved for conventional low dynamic range (LDR) images pose new challenges in HDR context. One such issue is a lack of standards for HDR image compression. Another is the limited availability of suitable image datasets that are suitable for studying and evaluation of HDR image compression. In this paper, we address this problem by creating a publicly available dataset of 20 HDR images and corresponding versions compressed at four different bit rates with three profiles of the upcoming JPEG XT standard for HDR image compression. The images cover different scenes, dynamic ranges, and acquisition methods (fusion from several exposures, frame of an HDR video, and CGI generated images). The dataset also includes Mean Opinion Scores (MOS) for each compressed version of the images obtained from extensive subjective experiments using SIM2 HDR monitor

Mixing tone mapping operators on the GPU by differential zone mapping based on psychophysical experiments

© 2016 In this paper, we present a new technique for displaying High Dynamic Range (HDR) images on Low Dynamic Range (LDR) displays in an efficient way on the GPU. The described process has three stages. First, the input image is segmented into luminance zones. Second, the tone mapping operator (TMO) that performs better in each zone is automatically selected. Finally, the resulting tone mapping (TM) outputs for each zone are merged, generating the final LDR output image. To establish the TMO that performs better in each luminance zone we conducted a preliminary psychophysical experiment using a set of HDR images and six different TMOs. We validated our composite technique on several (new) HDR images and conducted a further psychophysical experiment, using an HDR display as the reference that establishes the advantages of our hybrid three-stage approach over a traditional individual TMO. Finally, we present a GPU version, which is perceptually equal to the standard version but with much improved computational performance

JPEG XT: A Compression Standard for HDR and WCG Images [Standards in a Nutshell]

High bit depth data acquisition and manipulation have been largely studied at the academic level over the last 15 years and are rapidly attracting interest at the industrial level. An example of the increasing interest for high-dynamic range (HDR) imaging is the use of 32-bit floating point data for video and image acquisition and manipulation that allows a variety of visual effects that closely mimic the real-world visual experience of the end user [1] (see Figure 1). At the industrial level, we are witnessing increasing traction toward supporting HDR and wide color gamut (WCG). WCG leverages HDR for each color channel to display a wider range of colors. Consumer cameras are currently available with a 14- or 16-bit analog-to-digital converter. Rendering devices are also appearing with the capability to display HDR images and video with a peak brightness of up to 4,000 nits and to support WCG (ITU-R Rec. BT.2020 [2]) rather than the historical ITU-R Rec. BT.709 [3]. This trend calls for a widely accepted standard for higher bit depth support that can be seamlessly integrated into existing products and applications. While standard formats such as the Joint Photographic Experts Group (JPEG) 2000 [5] and JPEG XR [6] offer support for high bit depth image representations, their adoption requires a nonnegligible investment that may not always be affordable in existing imaging ecosystems, and induces a difficult transition, as they are not backward-compatible with the popular JPEG image format

Overview and Evaluation of the JPEG XT HDR Image Compression Standard

Standards play an important role in providing a common set of specifications and allowing inter-operability between devices and systems. Until recently, no standard for High Dynamic Range (HDR) image coding had been adopted by the market, and HDR imaging relies on proprietary and vendor specific formats which are unsuitable for storage or exchange of such images. To resolve this situation, the JPEG Committee is developing a new coding standard called JPEG~XT that is backwards compatible to the popular JPEG compression, allowing it to be implemented using standard 8-bit JPEG coding hardware or software. In this paper, we present design principles and technical details of JPEG~XT. It is based on a two-layers design, a base layer containing a Low Dynamic Range (LDR) image accessible to legacy implementations, and an extension layer providing the full dynamic range. The paper introduces three of currently defined profiles in JPEG~XT, each constraining the common decoder architecture to a subset of allowable configurations. We assess the coding efficiency of each profile extensively through subjective assessments, using 24 naive subjects to evaluate 20 images, and objective evaluations, using 106 images with five different tone-mapping operators and at 100 different bit rates. The objective results (based on benchmarking with subjective scores) demonstrate that JPEG~XT can encode HDR images at bit rates varying from 1.1 to 1.9 bit/pixel for estimated mean opinion score (MOS) values above 4.5 out of 5, which is considered as fully transparent in many applications. This corresponds to 23-times bitstream reduction compared to lossless OpenEXR PIZ compression

Design of a study to investigate the mechanisms of obstructive sleep apnoea by means of drug-induced sleep endoscopy

Background Obstructive sleep apnoea (OSA) is an independent risk factor of hypertension and cardiovascular diseases. Recurrent episodes of upper airways collapse during sleep causing blood oxygen desaturation, hypercapnia, and micro-arousals, are known to activate the sympathetic nervous system (SNS). However, whether changes in the renin-angiotensin-aldosterone system and endothelial activation also occur remains contentious. Methods Based on routine use of drug-induced sleep endoscopy (DISE) for the work-up of OSA patients in our centre, we designed a prospective study to investigate the haemodynamic and humoral changes occurring during the apnoeic episodes reproduced in vivo in the course of DISE. Specifically, plasma aldosterone concentration and renin activity, C-terminal fragment of proendothelin-1, as a marker of endothelial damage, and free plasma catecholamines, will be measured at fixed times during DISE. The activity of catechol-O-methyltransferase (COMT), a key catecholamine-inactivating enzyme that has been scantly investigated thus far owing to the lack of commercially available kits, will be also determined by a newly developed high performance liquid chromatography method, which is herein described. Results and conclusions The aim of this study is to provide novel information on the haemodynamic, hormonal, and SNS changes, and also on COMT activity modification concomitantly occurring during apnoea, thus contributing substantively to the understanding of the pathophysiology of OSA