Showing papers on "Tone mapping published in 2013"

Local Edge-Preserving Multiscale Decomposition for High Dynamic Range Image Tone Mapping

Abstract: A novel filter is proposed for edge-preserving decomposition of an image. It is different from previous filters in its locally adaptive property. The filtered image contains local means everywhere and preserves local salient edges. Comparisons are made between our filtered result and the results of three other methods. A detailed analysis is also made on the behavior of the filter. A multiscale decomposition with this filter is proposed for manipulating a high dynamic range image, which has three detail layers and one base layer. The multiscale decomposition with the filter addresses three assumptions: 1) the base layer preserves local means everywhere; 2) every scale's salient edges are relatively large gradients in a local window; and 3) all of the nonzero gradient information belongs to the detail layer. An effective function is also proposed for compressing the detail layers. The reproduced image gives a good visualization. Experimental results on real images demonstrate that our algorithm is especially effective at preserving or enhancing local details.

Evaluation of tone mapping operators for HDR video

Abstract: Eleven tone-mapping operators intended for video processing are analyzed and evaluated with camera-captured and computer-generated high-dynamic-range content. After optimizing the parameters of the operators in a formal experiment, we inspect and rate the artifacts (flickering, ghosting, temporal color consistency) and color rendition problems (brightness, contrast and color saturation) they produce. This allows us to identify major problems and challenges that video tone-mapping needs to address. Then, we compare the tone-mapping results in a pair-wise comparison experiment to identify the operators that, on average, can be expected to perform better than the others and to assess the magnitude of differences between the best performing operators.

Adaptive local tone mapping based on retinex for high dynamic range images

Abstract: In this paper, we present a new tone mapping technique for high dynamic range images based on the retinex theory. Our algorithm consists of two steps, global adaptation and local adaptation of the human visual system. In the local adaptation process, the Gaussian filter of the retinex algorithms is substituted with a guided filter to reduce halo artifacts. To guarantee good rendition and dynamic range compression, we propose a contrast enhancement factor based on the luminance values of the scene. In addition, an adaptive nonlinearity offset is introduced to deal with the strength of the logarithm function's nonlinearity. Experiments show that our algorithm provides satisfactory results while preserving details and reducing halo artifacts.

Efficient Tone-Mapping Of High-Bit-Depth Video To Low-Bit-Depth Display

Abstract: Several embodiments of an efficient tone mapping of high bit depth video to low bit depth displays are disclosed. In one embodiment, a system maps an input image data of a high dynamic range (HDR) onto output image data of a lower dynamic range (LDR) and where the mapping does not transform the input image data from one color space to another color space. One embodiment comprises a tone mapping module which outputs a tone-mapped luminance signal for output image data and a color mapping module which outputs chroma signals for the output image data. Intermediate image processing steps may be avoided and hence may increase the efficiency of the mapping.

Tone mapping-based high-dynamic-range image compression: study of optimization criterion and perceptual quality

Abstract: We study the issue of quality assessment in tone mapping- based high-dynamic-range (HDR) image compression. In this, there are two stages at which a decision should be made regarding perceptual vis- ual quality: (a) for finding the optimal parameters of the dynamic range reduction function so that the visual quality is maximized, and (b) visual quality judgment of the decompressed image. We first investigate two objective optimization criteria, namely mean squared error and structural similarity index measure, toward optimization of a tone mapping model- based HDR image compression method. We then conduct a comprehen- sive subjective study to evaluate the visual quality of the compressed HDR images. Therefore, we consider both objective and subjective aspects for HDR image compression. To our knowledge, no systematic and compre- hensive studies exist in the current literature which shed light on the issue of quality assessment in HDR compression. So this study brings in new knowledge and perspective for the relatively less investigated topic of HDR compression from the view point of perceptual quality. We further evaluate the prediction performances of four objective methods on the 140 compressed HDR images that have been subjectively rated.

Generation of Tone Mapping Function for Dynamic Pixel and Backlight Control

Abstract: Systems, methods, and devices are provided for generating a tone mapping function used in adjusting the power consumed by a backlight of an electronic display. One such method includes sampling an image frame in framebuffer space and generating a tone mapping function in linear space. The tone mapping function may have at least two portions: a nondistorting portion that does not to distort pixels to which it applies when an intensity of a backlight of the electronic display is modified and a distorting portion that does distort pixels to which it applies when the intensity of the backlight is modified. Thereafter, the intensity of the backlight may be modified based at least in part on the nondistorting portion of the tone mapping function, the tone mapping function converted to framebuffer space, and the tone mapping function applied to the image frame or a subsequent image frame.

Lighting Design for Globally Illuminated Volume Rendering

Abstract: With the evolution of graphics hardware, high quality global illumination becomes available for real-time volume rendering. Compared to local illumination, global illumination can produce realistic shading effects which are closer to real world scenes, and has proven useful for enhancing volume data visualization to enable better depth and shape perception. However, setting up optimal lighting could be a nontrivial task for average users. There were lighting design works for volume visualization but they did not consider global light transportation. In this paper, we present a lighting design method for volume visualization employing global illumination. The resulting system takes into account view and transfer-function dependent content of the volume data to automatically generate an optimized three-point lighting environment. Our method fully exploits the back light which is not used by previous volume visualization systems. By also including global shadow and multiple scattering, our lighting system can effectively enhance the depth and shape perception of volumetric features of interest. In addition, we propose an automatic tone mapping operator which recovers visual details from overexposed areas while maintaining sufficient contrast in the dark areas. We show that our method is effective for visualizing volume datasets with complex structures. The structural information is more clearly and correctly presented under the automatically generated light sources.

High Dynamic Range Imaging

Abstract: While real scenes produce a wide range of brightness variations, current cameras use low dynamic range image detector that typically provide 256 levels of brightness data at each pixel. We propose methods to create High Dynamic Range images, the method to enhance the dynamic range of is based on capturing multiple exposure photographs of the scene. Even if there are few methods available for creating HDR images, HDR display technologies still lag behind. We present a tone mapping algorithm to display HDR images on Low Dynamic Range display devices. We also deal with histogram manipulation for painterly effect on output. Applications of HDR images are discussed in brief. An algorithm to create HDR images for still scenes in Color Filter Array (CFA) domain is proposed and successfully implemented.

Fast tone mapping for high dynamic range images

Abstract: We present a fast, effective and flexible tone reproduction method that preserves visibility and contrast impression of high dynamic range scenes in low dynamic range reproduction devices. A single parameter controls the visibility and contrast in a simple and elegant manner and at interactive speed. The new method is simple to use and is computationally highly efficient. Experiments show that the technique produces good results on a variety of high dynamic range images. The method can also be used to enhance ordinary low dynamic range digital images.

Survey and evaluation of tone mapping operators for HDR video

Abstract: This work presents a survey and a user evaluation of tone mapping operators (TMOs) for high dynamic range (HDR) video, i.e. TMOs that explicitly include a temporal model for processing of variations in the input HDR images in the time domain. The main motivations behind this work is that: robust tone mapping is one of the key aspects of HDR imaging [Reinhard et al. 2006]; recent developments in sensor and computing technologies have now made it possible to capture HDR-video, e.g. [Unger and Gustavson 2007; Tocci et al. 2011]; and, as shown by our survey, tone mapping for HDR video poses a set of completely new challenges compared to tone mapping for still HDR images. Furthermore, video tone mapping, though less studied, is highly important for a multitude of applications including gaming, cameras in mobile devices, adaptive display devices and movie post-processing.

Visually Favorable Tone-Mapping With High Compression Performance in Bit-Depth Scalable Video Coding

Abstract: In bit-depth scalable video coding, the tone-mapping scheme used to convert high-bit-depth to eight-bit videos is an essential yet very often ignored component. In this paper, we demonstrate that an appropriate choice of a tone-mapping operator can improve the coding efficiency of bit-depth scalable encoders. We present a new tone-mapping scheme that delivers superior compression efficiency while adhering to a predefined base layer perceptual quality. We develop numerical models that estimate the base layer bit-rate (Rb), the enhancement layer bitrate (Re), and the mismatch (QL) between the resulting low dynamic range (LDR) base-layer signal and the predefined base layer representation. Our proposed tone curve is given by the solution of an optimization problem which minimizes a weighted sum of Rb, Re, and QL. The problem formulation also considers the temporal effect of tone-mapping by adding a constraint to the optimization problem that suppresses flickering artifacts. We also propose a technique with which to tone-map a high-bit-depth video directly in a compression-friendly color space (e.g., one luma and two chroma channels) without converting to the RGB domain. Experimental results show that we can save up to 40% of the total bit-rate (or 3.5 dB PSNR improvement for the same bitrate), and, in general, about 20% bit-rate savings can be achieved.

Automatic selection of optimum algorithms for high dynamic range image processing based on scene classification

Abstract: A method for processing high dynamic range (HDR) images by selecting preferred tone mapping operators and gamut mapping algorithms based on scene classification. Scenes are classified into indoor scenes, outdoor scenes, and scenes with people, and tone mapping operators and gamut mapping algorithms are selected on that basis. Prior to scene classification, the multiple images taken at various exposure values are fused into a low dynamic range (LDR) image using an exposure fusing algorithm, and scene classification is performed using the fused LDR image. Then, the HDR image generated from the multiple images are tone mapped into a LDR image using the selected tone mapping operator and then gamut mapped to the color space of the output device such as printer.

An integer tone mapping operation for hdr images expressed in floating point data

Abstract: This report proposes a new tone mapping operation which is implemented in integer input and integer output. A tone mapping operation (TMO) generates a low dynamic range (LDR) image from a high dynamic range (HDR) image. Since pixel values of an HDR image are generally expressed in a floating point data format, e.g. RGBE, OpenEXR, a TMO is also implemented in floating point calculations in conventional approaches. However, it requires huge memory resources, even though a resulting LDR image is expressed in simple integer. We perform a TMO with integer input and integer output to reduce memory resources. It is experimentally confirmed with PSNR and contrast evaluations that the proposed method offers LDR images of visually high quality comparable to the conventional method.

Image capture apparatus, method of controlling image capture apparatus, and electronic device

Abstract: An image capture apparatus is provided that is capable of accurately determining exposure conditions of multiple images to be used in high dynamic range compositing in a short duration, based on a captured image. A scene dynamic range is computed based on luminance information obtained from an image captured with a standard exposure according to a luminance zone to be prioritized in high dynamic range shooting and luminance information obtained from an image captured with an over-exposure or an under-exposure relative to the standard exposure. An exposure range of multiple images for creating a high dynamic range image is determined according to the computed dynamic range.

Local tone mapping for high dynamic range images

Abstract: A method of local tone mapping of a high dynamic range (HDR) image is provided that includes dividing a luminance image of the HDR image into overlapping blocks and computing a local tone curve for each block, computing a tone mapped value for each pixel of the luminance image as a weighted sum of values computed by applying local tone curves of neighboring blocks to the pixel value, computing a gain for each pixel as a ratio of the tone mapped value to the value of the pixel, and applying the gains to corresponding pixels in the HDR image. A weight for each value is computed based on distance from the pixel to the center point of the block having the local tone curve applied to compute the value and the intensity difference between the value of the pixel and the block mean pixel value.

Intra-and-Inter-Constraint-Based Video Enhancement Based on Piecewise Tone Mapping

Abstract: Video enhancement plays an important role in various video applications. In this paper, we propose a new intra-and-inter-constraint-based video enhancement approach aiming to: 1) achieve high intraframe quality of the entire picture where multiple regions-of-interest (ROIs) can be adaptively and simultaneously enhanced, and 2) guarantee the interframe quality consistencies among video frames. We first analyze features from different ROIs and create a piecewise tone mapping curve for the entire frame such that the intraframe quality can be enhanced. We further introduce new interframe constraints to improve the temporal quality consistency. Experimental results show that the proposed algorithm obviously outperforms the state-of-the-art algorithms.

Approach for camera control

Abstract: An approach is provided for performing back-end operations for camera control. In one example, a method includes the following: receiving a user edit via a user interface device that displays an interpretation of a scene at which a camera lens of the camera is pointing, wherein the user edit is based on user input that is associated with a selection region on the user interface device; generating an edits mask based on one or more matching image patches, which are based on the user edit and a high dynamic range (HDR) image generated by the camera; performing one or more tone mapping operations based on the edits mask and the HDR image in order to generate a tone mapped HDR image; and performing one or more metering operations based on the edits mask and the tone mapped HDR image in order to generate metering parameters for frame capturing operations.

Method for tone mapping based on histogram equalization

Abstract: The invention discloses a method for tone mapping based on histogram equalization. The method comprises the steps of: 1) inputting a high-dynamic range image; 2) acquiring the image brightness and converting the image brightness into a log domain; 3) carrying out histogram statistics; 4) calculating the average brightness of the image, and carrying out segmentation on the histogram by taking the average brightness as a segmentation point; 5) carrying out differentiation setting on mapping parameters of two segments of the histogram; 6) carrying out a histogram equalization algorithm in a segmentation mode; 7) restoring a brightness channel after the tone mapping to an RGB color space; and 8) outputting a displayable low-dynamic range image. According to the invention, the differentiation setting is carried out on the mapping parameters of the two segments after the histogram is segmented, and a bright background is enabled to map linearly as far as possible so as to reduce missing of a highlight part, and a foreground part is still subjected to histogram equalization processing so as to expand the contrast ratio of the image. The method disclosed by the invention can effectively maintain the original brightness of the image while increasing the contrast ration of the image, and effectively improves a phenomenon of brightness saturation in a classical histogram equalization algorithm.

Impact of temporal coherence-based Tone Mapping on video compression

Abstract: Tone Mapping Operators (TMOs) aim at converting real world high dynamic range (HDR) images captured with HDR cameras, into low dynamic range (LDR) images that can be displayed on LDR displays Even though most of the designed solutions provide good results for still HDR images, they are not efficient for tone mapping video sequences The main issue is their inability to preserve the temporal correlation inherent in a video sequence This has a consequence on the video compression efficiency In this work, we show that higher compression ratios can be obtained by preserving the temporal coherency of a sequence We evaluate temporal coherency and video compression in regard to two aspects The first one evaluates the quality of the decoded LDR sequences after applying different TMOs The second aspect assesses the quality of a reconstructed HDR sequence when a TMO and a codec are applied

A novel image decomposition approach and its applications

Abstract: The current state-of-the-art edge-preserving decomposition techniques may not be able to fully separate textures while preserving edges. This may generate artifacts in some applications, e.g., edge detection, texture transfer, etc. To solve this problem, a novel image decomposition approach based on explicit texture separation from large scale components of an image is presented. We first apply a Gaussian structure-texture decomposition, to separate the majority of textures out of the input image. However, residual textures are still visible around the strong edges. To remove these residuals, an asymmetric sampling operator is proposed and followed by a joint bilateral correction to remove an excessive blur effect. We demonstrate that our approach is well suited for the tasks such as texture transfer, edge detection, non-photorealistic rendering, and tone mapping. The results show our approach outperforms existing state-of-the-art image decomposition approaches.

Brightness-controllable and detail-preservation tone mapping method

Abstract: The invention discloses a brightness-controllable and detail-preservation tone mapping method. The brightness-controllable and detail preservation tone mapping method includes inputting a high-dynamic-range image; acquiring the brightness of the image and converting the brightness of the image into a logarithm domain; computing the average brightness and standard deviation of the inputted image; dividing a histogram of the brightness; modifying sections of the histogram; presetting the average brightness and standard deviation of an outputted low-dynamic-range image; computing gray-level division points of the low-dynamic-range image; estimating the average brightness and standard deviation of the outputted low-dynamic-range image via a mathematical model; correcting the standard deviation until a relative error between the preset standard deviation and the estimated standard deviation is smaller than a certain value; performing tone mapping on the sections of the histogram; restoring brightness channels to RGB (red, green and blue) color space after tone mapping is performed on the brightness channels; outputting the displayable low-dynamic-range image. The brightness-controllable and detail-preservation tone mapping method has the advantages that the brightness is controllable, details are preserved, and a high-brightness area processing effect is superior to high-brightness area processing effects realized by other global tone mapping methods.

Context-dependent JPEG backward-compatible high-dynamic range image compression

Abstract: High-dynamic range (HDR) imaging is expected, together with ultrahigh definition and high-frame rate video, to become a technology that may change photo, TV, and film industries. Many cameras and displays capable of capturing and rendering both HDR images and video are already available in the market. The popularity and full-public adoption of HDR content is, however, hindered by the lack of standards in evalu- ation of quality, file formats, and compression, as well as large legacy base of low-dynamic range (LDR) displays that are unable to render HDR. To facilitate the wide spread of HDR usage, the backward compatibility of HDR with commonly used legacy technologies for storage, rendering, and compression of video and images are necessary. Although many tone-mapping algorithms are developed for generating viewable LDR con- tent from HDR, there is no consensus of which algorithm to use and under which conditions. We, via a series of subjective evaluations, demonstrate the dependency of the perceptual quality of the tone-mapped LDR images on the context: environmental factors, display parameters, and image con- tent itself. Based on the results of subjective tests, it proposes to extend JPEG file format, the most popular image format, in a backward compat- ible manner to deal with HDR images also. An architecture to achieve such backward compatibility with JPEG is proposed. A simple implementation of lossy compression demonstrates the efficiency of the proposed archi- tecture compared with the state-of-the-art HDR image compression. © 2013

Anisotropic Diffusion for Details Enhancement in Multi-Exposure Image Fusion

Abstract: We develop a multiexposure image fusion method based on texture features, which exploits the edge preserving and intraregion smoothing property of nonlinear diffusion filters based on partial differential equations (PDE). With the captured multiexposure image series, we first decompose images into base layers and detail layers to extract sharp details and fine details, respectively. The magnitude of the gradient of the image intensity is utilized to encourage smoothness at homogeneous regions in preference to inhomogeneous regions. Then, we have considered texture features of the base layer to generate a mask (i.e., decision mask) that guides the fusion of base layers in multiresolution fashion. Finally, well-exposed fused image is obtained that combines fused base layer and the detail layers at each scale across all the input exposures. Proposed algorithm skipping complex High Dynamic Range Image (HDRI) generation and tone mapping steps to produce detail preserving image for display on standard dynamic range display devices. Moreover, our technique is effective for blending flash/no-flash image pair and multifocus images, that is, images focused on different targets.

Optimized tone mapping with LDR image quality constraint for backward-compatible high dynamic range image and video coding

Abstract: Backward compatibility to low dynamic range (LDR) displays is an important requirement for high dynamic range (HDR) image and video coding in order to enable a successful transition to HDR technology. In a recent work [1], an optimized solution for tone mapping and inverse tone mapping of HDR images is achieved in terms of mean square error (MSE) of the logarithm of luminance values of HDR image pixels for backward-compatible compression. Although this pioneer optimization approach provides a well settled mathematical framework for tone mapping, one of its important shortcomings is not to take the quality of the resulting LDR images into account during the formulation. In this paper, we include the LDR image quality as a constraint to optimization problem and develop a methodology to compromise the trade-off between HDR image quality and LDR image quality during HDR image and video coding. The developed methodology is verified on HDR images by showing the increase (decrease) in the quality of generated LDR images while losing (gaining) from the rate-distortion performance of HDR image coding.

Content adaptive bilateral filtering

Abstract: Bilateral filter is perhaps the most popular and simplest edge-preserving local filter. However, it may produce halos near some edges due to unwanted smoothing of the edges. In this paper, a content adaptive bilateral filter is proposed to overcome this problem. Both spatial similarity and range similarity parameters of the proposed bilateral filter are adaptive to the content of an image to be filtered rather than being fixed as in the existing bilateral filter. The proposed filter preserves edges and smoothes flat areas better than the existing bilateral filter. It is applied to design a local tone mapping algorithm for high dynamic range images as well as a noise reduction algorithm for low dynamic range color images. Experimental results show that the resultant tone mapping algorithm produces images with better visual quality and at the same time halo artifacts are avoided from appearing in the tone mapped image. The resultant noise reduction algorithm can also produce images with higher structural similarity index values and better visual quality. Noise in smooth regions are more reduced and edges are preserved better in the de-noised image.

Anisotropic Diffusion for Details Enhancement in Multiexposure Image Fusion

Abstract: We develop a multiexposure image fusion method based on texture features, which exploits the edge preserving and intraregion smoothing property of nonlinear diffusion filters based on partial differential equations (PDE). With the captured multiexposure image series, we first decompose images into base layers and detail layers to extract sharp details and fine details, respectively. The magnitude of the gradient of the image intensity is utilized to encourage smoothness at homogeneous regions in preference to inhomogeneous regions. Then, we have considered texture features of the base layer to generate a mask (i.e., decision mask) that guides the fusion of base layers in multiresolution fashion. Finally, well-exposed fused image is obtained that combines fused base layer and the detail layers at each scale across all the input exposures. Proposed algorithm skipping complex High Dynamic Range Image (HDRI) generation and tone mapping steps to produce detail preserving image for display on standard dynamic range display devices. Moreover, our technique is effective for blending flash/no-flash image pair and multifocus images, that is, images focused on different targets.

Gaze-Dependent Tone Mapping

Abstract: In this paper we model the process of temporal adaptation of the human visual system to varying luminance conditions. An eye tracker is used to capture the location of an observer’s gaze in a high dynamic range image displayed on the screen. We apply a novel technique of eye tracker data filtering to avoid flickering caused by incorrect gaze estimation. Temporary adaptation luminance is then determined in the area surrounding the gaze point. We use its value to compress the high dynamic range image and display it on the low dynamic range display. The applied tone mapping technique uses a global compression curve in which location is shifted along the luminance axis according to a value of the adaptation luminance. This technique models the natural process of adaptation occurring in the human eyes, also taking into account the time-dependent visual adaptation to dark and bright backgrounds.

Segmentation-based optimized tone mapping for high dynamic range image and video coding

Abstract: A core part of the state-of-the art high dynamic range (HDR) image and video compression methods is the tone mapping operation to convert the visible luminance range into the finite bit depths that can be supported by the current video codecs. These conversions are until now optimized to provide backward compatibility to the existing low dynamic range (LDR) displays. However, a direct application of these methods for the emerging HDR displays can result in a loss of details in the bright and dark regions of the HDR content. In this paper, we overcome this limitation by designing a tone mapping operation which handles the bright and dark regions separately. The proposed method first finds the optimal segmentation of the HDR image into two parts, namely dark and bright regions, and then designs the optimal tone mapping for each region in terms of the mean square error between the logarithm of the luminance values of the original and reconstructed HDR content (HDR-MSE). The results indicate the superiority of the proposed method over the state-of-the art HDR coding methods.