Pixel Luminance Research Articles

Luminance-Preserving Color Conversion

With the advent of new television standards introducing ultrahigh definition and high dynamic range, backward compatibility with older devices becomes an issue. We propose a method for converting footage produced in BT.2100 colorimetry to a BT.709 compliant representation. The process preserves each pixel's luminance and is fully reversible. Technically, our approach determines the exact polygonal shape of the effective BT.2100 and BT.709 gamuts at a given luminance and maps colors from one to the other by desaturating them.

Generating visually appealing QR codes using colour image embedding

ABSTRACTQuick Response (QR) codes have become very popular in current scenario. Being machine readable, they appear like blocks of random black and white noise. With their increasing use in marketing material, many attempts have been made to make them visually appealing by embedding images and logos. We propose a colour image embedding method that uses circular modules to reduce the block-like appearance of the code. The luminance of the image pixels corresponding to the centric and surrounding regions of a circular code module is modified in such a way that they blend into the code with least visual distortion, and the resultant code demonstrates high degree of decoding robustness. The results of experiments to assess the visual appeal of the resultant codes, and their tolerance to noise and blur indicate that the visually appealing codes have decodability comparable to the original QR codes, thus justifying the attempt to embed image in an otherwise non-appealing QR code. The codes generated by the proposed method and three other state-of-the art methods are compared for visual appeal and decoding robustness. The results of the comparison indicate that the codes generated by the proposed method have visual appeal best amongst the codes generated by other state-of-the art methods. In terms of tolerance to noise and blur, they are the best amongst the codes which have comparable visual appeal, and second best amongst all.

A model of perceived dynamic range for HDR images

For High Dynamic Range (HDR) content, the dynamic range of an image is an important characteristic in algorithm design and validation, analysis of aesthetic attributes and content selection. Traditionally, it has been computed as the ratio between the maximum and minimum pixel luminance, a purely objective measure; however, the human visual system's perception of dynamic range is more complex and has been largely neglected in the literature. In this paper, a new methodology for measuring perceived dynamic range (PDR) of chromatic and achromatic HDR images is proposed. PDR can benefit HDR in a number of ways: for evaluating inverse tone mapping operators and HDR compression methods; aesthetically; or as a parameter for content selection in perceptual studies. A subjective study was conducted on a data set of 36 chromatic and achromatic HDR images. Results showed a strong agreement across participants' allocated scores. In addition, a high correlation between ratings of the chromatic and achromatic stimuli was found. Based on the results from a pilot study, five objective measures (pixel-based dynamic range, image key, area of bright regions, contrast and colorfulness) were selected as candidates for a PDR predictor model; two of which have been found to be significant contributors to the model. Our analyses show that this model performs better than individual metrics for both achromatic and chromatic stimuli.

A Luminance Compensation Method Using Optical Sensors with Optimized Memory Size for High Image Quality AMOLED Displays

This paper proposes a luminance compensation method using optical sensors to achieve high luminance uniformity of active matrix organic light-emitting diode (AMOLED) displays. The proposed method compensates for the non-uniformity of luminance by capturing the luminance of entire pixels and extracting the characteristic parameters. Data modulation using the extracted characteristic parameters is performed to improve luminance uniformity. In addition, memory size is optimized by selecting an optimal bit depth of the extracted characteristic parameters according to the trade-off between the required memory size and luminance uniformity. To verify the proposed compensation method with the optimized memory size, a 40-inch 1920x1080 AMOLED display with a target maximum luminance of 350 cd/m2 is used. The proposed compensation method considering a 4σ range of luminance reduces luminance error from ± 38.64%, ± 36.32%, and ± 43.12% to ± 2.68%, ± 2.64%, and ± 2.76% for red, green, and blue colors, respectively. The optimal bit depth of each characteristic parameter is 6-bit and the total required memory size to achieve high luminance uniformity is 74.6 Mbits.

Tone mapping with contrast preservation and lightness correction in high dynamic range imaging

In real-world environments, the human visual system perceives a wide range of luminance in a scene. However, the full range of tones in a high dynamic range (HDR) scene cannot be displayed on standard display devices due to their low dynamic range (LDR). Therefore, tone mapping is necessary to faithfully display a HDR scene on an LDR display device. Existing tone mapping methods have problems because details and contrast in a scene are not preserved faithfully, and they also distort the colors in a scene. Thus, we propose a tone mapping method for preserving the detail in an HDR scene using a weighted least squares filter, which preserves the global contrast in a scene by using a competitive learning neural network, before applying a tone reproduction operator to preserve the color without shifting the lightness. According to the Helmholtz–Kohlrausch effect, the perception of brightness depends on the lightness, chroma, and hue of a color. For example, the luminance of pixels with specific colors such as red and blue is low in an HDR scene. The proposed method corrects the lightness of pixels according to the color (i.e., lightness, chroma, and hue) of a tone-mapped image. Experimental results with several test sets of images demonstrated that the proposed tone mapping method with contrast preservation and lightness correction is more suitable for dynamic range compression than existing tone mapping methods, while it also preserves the color of a scene in an effective way.

P-195L:Late-News Poster: Head Position Model-based Latency Measurement System for Virtual Reality Head Mounted Display

This paper presents a novel quantifiable latency measurement system specialized for HMD devices. After analyzing the head position, we implement the rotary platform and the pixel luminance change detector. Then, we accurately measure the latency between the HMD physical movement and an output image change.

A Novel Image Identifier Generation Method Using Luminance and Location

It has been more than 40 years since the first digital imaging sensor was invented. For the last four decades, image acquisition functionality has continuously been improved, in terms of quality, size and cost. Consequently the digital imaging techniques started to be utilized in the digital camera industry and various component applications as well. According to the trend of the current applications of digital imaging, images are being produced not only by the conventional mechanism, such as regular camera, but also by the applications with digital image acquisition functionality, who aim to better understand the circumstances using an analysis of images. As a consequence of this trend, the amount of images created by diverse image related devices is immeasurably huge. Moreover the utilization of such voluminous amount of images demands a management system that can support information management operations, such as search, contents duplication and modification detection. These operations can be efficiently and effectively processed when the image related operations are performed by the usage of distinctive values, not by the image processing operations which require much more processing time. In order to meet the satisfaction of the requirement, we have been studied approaches that can utilize the line segments and the luminance areas. However, those approaches are disadvantage in the case of that an image contains the relatively large regions with sparse edges or stationary luminance. In order to resolve such circumstances, in this paper, we present a more improved approach, in the perspective of cost and requirement satisfaction. The proposed method mainly exploits luminance areas and pixel location, so that the produced image identifiers could satisfy one-to-one relationship between images and identifiers. With experimental evaluations, we demonstrate that our approach is most favorable considering cost-effectiveness and efficiency.

Optical effects of anti-glare films on a dual-view display

The effects of different anti-glare films on an 8-inch dual-view display were investigated. To quantify the display performance, the image sharpness, speckle, and crosstalk were evaluated. The image sharpness and sparkle were first measured, and the obtained values were compared with the results of a jury appraisal for devising acceptance levels. For image sparkle, it was found that the standard deviation for the individual pixel luminance must be less than 40 to be acceptable to the user. Finally, it was found that the crosstalk of the display needs to be less than 0.5 to be unnoticeable and less than 1.0 to be acceptable.

Minimum mean brightness error contrast enhancement of color images using adaptive gamma correction with color preserving framework

In this paper, we propose an efficient method to enhance contrast of digital images. Image contrast enhancement is a pre-processing step that improves efficiency of other image dealing applications such as computer vision and pattern recognition. The proposed method enhances contrast and brightness of given image using the gamma correction and weighted probability distribution of luminance pixels. Experiments results show that the proposed method is able to enhance contrast of all type of color images without much affecting its visual and color information.

Editorial: Using Noise to Characterize Vision.

Editorial: Using Noise to Characterize Vision.

Real-time pixel luminance optimization for dynamic multi-projection mapping

Using projection mapping enables us to bring virtual worlds into shared physical spaces. In this paper, we present a novel, adaptable and real-time projection mapping system, which supports multiple projectors and high quality rendering of dynamic content on surfaces of complex geometrical shape. Our system allows for smooth blending across multiple projectors using a new optimization framework that simulates the diffuse direct light transport of the physical world to continuously adapt the color output of each projector pixel. We present a real-time solution to this optimization problem using off-the-shelf graphics hardware, depth cameras and projectors. Our approach enables us to move projectors, depth camera or objects while maintaining the correct illumination, in realtime, without the need for markers on the object. It also allows for projectors to be removed or dynamically added, and provides compelling results with only commodity hardware.

Combining cellular automata and local binary patterns for copy-move forgery detection

Detection of duplicated regions in digital images has been a highly investigated field in recent years since the editing of digital images has been notably simplified by the development of advanced image processing tools. In this paper, we present a new method that combines Cellular Automata (CA) and Local Binary Patterns (LBP) to extract feature vectors for the purpose of detection of duplicated regions. The combination of CA and LBP allows a simple and reduced description of texture in the form of CA rules that represents local changes in pixel luminance values. The importance of CA lies in the fact that a very simple set of rules can be used to describe complex textures, while LBP, applied locally, allows efficient binary representation. CA rules are formed on a circular neighborhood, resulting in insensitivity to rotation of duplicated regions. Additionally, a new search method is applied to select the nearest neighbors and determine duplicated blocks. In comparison with similar methods, the proposed method showed good performance in the case of plain/multiple copy-move forgeries and rotation/scaling of duplicated regions, as well as robustness to post-processing methods such as blurring, addition of noise and JPEG compression. An important advantage of the proposed method is its low computational complexity and simplicity of its feature vector representation.

Uncertainty model of electro-optical thrombus growth estimation for early risk detection

It is proposed a device for the study of the real-time aggregation of white thrombi in whole blood. This device allows extrapolating the 3D-shape of platelets clotting within artificial capillaries, by simultaneously monitoring the electrical impedance between a pair of specifically designed gold electrodes and 2D optical image of pixel luminance of the fluorescent labeled platelets. Up to 30 3D images per minute have been obtained, for a process which requires few minutes before the aggregation of large thrombi structures, a noticeable result with respect to other 3D-shape reconstruction methods. The contribution of this paper mainly consists in the study of an uncertainty model which, in our opinion, is of fundamental importance to provide a valuable metrological estimation of thrombus growth under flow conditions.

Image enhancement and space-variant color reproduction method for endoscopic images using adaptive sigmoid function.

This paper presents an image enhancement and space-variant color reproduction method based on adaptive sigmoid function for endoscopic image. At first, using YCBCR conversion matrix, the color image is separated into luminance and chrominance components. The adaptive sigmoid function with two controlling parameters is applied on the uniformly distributed luminance pixels. The space-variant color reproduction generates new chrominance components by transferring and modifying old chrominance based on texture information. Finally, new luminance and chrominance components are converted into RGB color image. The proposed method highlights some of the tissue and vascular characteristics as well as pit patterns in lesion and polyp. The performance of the proposed scheme is compared with other related methods in terms of image quality, focus value, efficiency of color reproduction and statistic of visual representation.

A Hidden Markov Model to Identify Regions of Interest from Eye Movements, with an Application to Nodule Detection in Chest X-Rays

Nodules that may represent lung cancer are often missed in chest X-rays by radiologists. Recording of eye movements during search for nodules provides insights into the search process. We develop a Hierarchical Bayes Hidden Markov Model (HMM) and analyze eye tracking data of sixteen laymen looking at fourteen chest X-rays, of which seven contained a potentially cancerous nodule. We use the luminance of pixels in the X-ray image as prior information on the location of a nodule. Using a reversible jump Markov Chain Monte Carlo algorithm to estimate the HMM enables us to identify the number of regions of interest (ROIs) on each image, as well as their centers, sizes and orientations. In the application in most cases one of the ROIs covers the nodule precisely. Our study thus demonstrates that a HMM analysis of eye movements recorded on laymen may accurately reveal the location of nodules, which has significant implications. The HMM model may be useful in other applications to identify ROIs from eye movement data.

液晶显示全局动态调光算法的高效实现方法研究

The dynamic dimming algorithm consists of two steps:dimming level determination and LC pixel compensation.Look-up-table method is applied in S-curve dimming algorithm based on image classification.In order to solve the shortcomings of large consumption of hardware resources and slow processing speed of this algorithm,this paper proposes two kinds of algorithm implementations:Arithmetic Sequence Method(ASM)and Least-squares Fitting Method(LSFM).The simulation results show that the largest standard deviation is 1.8and 0.8of ASM and LSFM,respectively.The practical tests have done on the LCD TV prototype.Compared to the luminance of pixels from look-up table method,the deviation of ASM is less than 3graylevels and the deviation of LSFM is less than 1 gray-level.The hardware storage resource decreases from 71% of the proposed methods to 4% of look-up-table.The simulation and experimental results show that LSFM is better.

0202 Multi-layer Color PIVによるミストの3次元分布計測法の開発

In order to measure three-dimensional flows in large atmospheric space, we have developed a new PIV system based on Multi-layer Color PIV. This new system allows us to determine the six-layer three-dimensional velocity vector fields at a given frame rate just using a single camera view by color coded volumetric projection of light. In this paper, we developed the prototype system, and verified it by simulation of artificial 3D smoke. This system estimates the six-layer two components velocity field in three-dimensional vector field. As the result of verification, reconstructed layers and determined vectors have high correlation value with theoretic image and vector field, around the center of measurement volume. On the other hand, two problems were found. One is a fragility of pattern matching system for strong velocity gradient field. The other is increase of layer reconstruction error against low luminance pixels.

Dynamic Driver Supply Voltage Scaling for Organic Light Emitting Diode Displays

Organic light emitting diode (OLED) display is a self-illuminating device that is supposed to be more power efficient than liquid crystal display (LCD). However, OLED display panels consume as much power as LCD panels due to total internal reflection. As the power consumption of the OLED panel depends on the pixel colors, most of the earlier power saving methods alter the pixel colors. In practice, such OLED power saving techniques can hardly accommodate photo viewers and movie players. This paper introduces the first OLED power saving technique that dynamically changes the supply voltage of the panel. Reduced supply voltage results in both power saving and decreased pixel luminance, but model-based color correction restores the decreased luminance with minimum color distortion. This technique is similar to dynamic backlight scaling of LCDs but is based on the unique characteristics of the OLED drivers. We provide an online color compensation algorithm using the luminance histogram. Luminance quantization in the histogram also achieves resource minimization. We develop a prototype and demonstrate the proposed OLED dynamic voltage scaling (DVS). Experimental result shows that the proposed OLED DVS saves up to 74.7% of the display power for the still images and up to 35.9% for movie clips.

Pedestrian Detection Based on Blob Motion Statistics

Pedestrian detection based on video analysis is a key functionality in automated surveillance systems. In this paper, we present efficient detection metrics that consider the fact that human movement presents distinctive motion patterns. Contrary to several methods that perform an intrablob analysis based on motion masks, we approach the problem without necessarily considering the periodic pixel motion inside the blob. As such, we do not analyze periodicity in the pixel luminances, but in the motion statistics of the tracked blob as a whole. For this, we propose the use of the following cues: 1) a cyclic behavior in the blob trajectory, and 2) an in-phase relationship between the change in blob size and position. In addition, we also exploit the relationship between blob size and vertical position, assuming that the camera is positioned sufficiently high. If the homography between the camera and the ground is known, the features are normalized by transforming the blob size to the real person size. For improved performance, we combine these features using the Bayes classifier. We also present a theoretical statistical analysis to evaluate the system performance in the presence of noise. We perform online experiments in a real industrial scenario and also with videos from well-known databases. The results illustrate the applicability of the proposed features.

Image Quality-Aware Backlight Dimming With Color and Detail Enhancement Techniques

In this paper, we propose an advanced backlight dimming technique that preserves the quality of color and details in images even when the backlight luminance of liquid crystal display (LCD) devices is lowered. The proposed backlight dimming technique consists of the following two steps: backlight luminance level selection and pixel compensation. In the first step, to reduce power consumption, the proposed approach selects an optimal level of backlight luminance for a given image based on image quality evaluation that considers the peak signal-to-noise ratio (PSNR) and color distortion level. In the second step, it adaptively adjusts the RGB ratio depending on image details, thereby enhancing image color and details, which are degraded by the lowered backlight luminance level calculated in the first step. The simulation results showed that the proposed method successfully selected the optimal backlight luminance level and prevented severe color distortion, while the benchmark method induced severe color distortion in some images. In addition, for the same backlight luminance level, pixel compensation in the proposed method reduced color difference for color distortion evaluation and the loss rate of edge strength, which showed detail loss by up to 3.58% and 40.55%, compared to benchmark methods, respectively.