Tone Curve Research Articles

Linearization and Normalization in Spatial Frequency Response Measurement

The standard ISO12233:2014 describes different methods on how to measure the spatial frequency response (SFR) of an imaging system. It uses either a slanted edge (eSFR) or a harmonic Siemens star (sSFR). Within the document, it is mentioned that a linearization process shall correct a non-linear tone curve. Normalization is not further defined, but is an important part of the evaluation for the sSFR method. Using the sSFR method for texture loss analysis in the upcoming ISO19567 standard (based on a low contrast version of the Siemens star) it is even more critical. In this paper, we evaluate the influence of linearization and normalization on the results, identify issues in common implementations and present a new approach.

Local inverse tone curve learning for high dynamic range image scalable compression.

This paper presents a scalable high dynamic range (HDR) image coding scheme in which the base layer is a low dynamic range version of the image that may have been generated by an arbitrary tone mapping operator (TMO). No restriction is imposed on the TMO, which can be either global or local, so as to fully respect the artistic intent of the producer. Our method successfully handles the case of complex local TMOs thanks to a block-wise and non-linear approach. A novel template-based interlayer prediction (ILP) is designed in order to perform the inverse tone mapping of a block without the need to transmit any additional parameter to the decoder. This method enables the use of a more accurate inverse tone mapping model than the simple linear regression commonly used for block-wise ILP. In addition, this paper shows that a linear adjustment of the initially predicted block can further improve the overall coding performance by using an efficient encoding scheme of the scaling parameters. Our experiments have shown an average bitrate saving of 47% on the HDR enhancement layer, compared with the previous local ILP methods.

Modified Robust Technique for Intra and Inter Constraint based on Video Enhancement using Colour Modeling of Countable Frames

New trends are more essential in the area of video enhancement for various emerging needs. Hence, we proposed a novel technique which efficiently suited for various types videos. This paper discussed about the video enhancement aiming to achieve high intra frame and inter frame qualities in an entire video. We proposed and evaluated two parameters i.e., Intra frame quality (among the frames) of the entire video and inter frame quality (in between the frames) of the entire video. Such as multiple regions of interest that can be adaptively and simultaneously enhanced. Two steps were incorporated in to the proposed work for object quality retrieval. These are (i) ACB step improve intra frame analysis features for region-of-interest a global tone curve is created by fusing from other region and (ii) ECB step improve inter frame quality implement by histogram equalization method. We observed better improvement in PSNR values and considerable reduction in MSE values over the existing techniques. Thus, the modified technique improves the video enhancement with respect to the countable number of frames and valid better results at various levels of frames. We also evaluated the execution time in the process of video enhancement which is the ultimate parameter to discuss the power consumption. The observations of the proposed technique surpass the existing methods in the area of video enhancement in frame by frame procedure. The results of the proposed technique outperform present techniques and werre simulated using MATLAB.

A perceptually uniform tone curve for OLED and other high dynamic range displays

A perceptually uniform tone curve for OLED and other high dynamic range displays

P‐193L: Late‐News Poster: Optimal Tone Curve Characteristics of Transparent Display for Preferred Image Reproduction

AbstractPreferred monitor gamma setting is compared between normal and 10%‐transmittance transparent display by simulating indoor lighting condition using LCD monitor. Four test images are manipulated to have 10 different monitor gamma values both for normal and transparent display. Based on 10 observers' judgment, it is found that lower gamma setting is preferred for transparent display than that for normal display. The preferred gamma settings for normal and transparent display have the similar lightness difference between gray levels.

Aging impairs myogenic adaptation to pulsatile pressure in mouse cerebral arteries (1079.7)

Stability of myogenic tone of cerebral arteries is essential for adequate control over penetration of pressure (P) waves into the distal portion of the cerebral microcirculation (the resistance to flow is dominated by the fourth power of the internal vessel radius). Because aging promotes cerebromicrovascular injury, we tested the hypothesis that aging alters the myogenic response. P‐induced constriction of cannulated middle cerebral arteries (MCA) isolated from young (3 mo) and aged (24 mo) mice was assessed. Both young and aged MCAs developed similar myogenic tone in response to stepwise, steady‐state increases in intraluminal P. Young MCAs exhibited significant myogenic adaptation to sinusoidal pulsatile P (amplitude: 40 mmHg, freq:450/min). While in myogenically inactive MCAs each P pulse elicited a ~7% distension in synchrony with the pulsatile P, in young myogenically active MCAs the amplitude of the diameter changes induced by the P pulses in the autoregulated P range was significantly attenuated (~2%). The mean P‐myogenic tone curve was similar in young MCAs exposed to constant and pulsatile P. In aged MCAs the cyclic changes in diameter induced by the P pulses were increased (~4%) and development of myogenic tone in response to pulsatile P was impaired. Collectively, aging impairs myogenic adaptation of cerebral arteries to pulsatile P, which likely promotes the development of cerebral microbleeds and BBB disruption by allowing high P to penetrate the distal portion of the cerebral microcirculation.Grant Funding Source: Supported by TÁMOP 4.2.4.A/2‐11‐1‐2012‐0001,SROP‐4.2.2.A‐11/1/KONV‐2012‐0024 and 0017,OTKA K‐108444

Increasing Quality of the Interframe and also extract Histogram using Super-Imposing

Video enhancement approach aiming to achieve high qualities in entire video. Proposes a Superimposing algorithm for improve quality of intraframe based on multiple regions-of-interest and create piecewise tone mapping curve for entire frame, interframe constraints to improve the temporal quality consistency and based on result extract histogram. Two step are used for object quality retrieval (i) ACB step improve intraframe analysis features for region-of-interest ,a global tone curve is created by fusing from other region and (ii) ECB step improve interframe quality implement by histogram equalization method. Learning-based color tone mapping method to conduct global color transfer by turning the color statistic of the face region according to a per-trained set. These methods can improve the quality of some specific regions.

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

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 (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> ), the enhancement layer bitrate (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> ), and the mismatch (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ) 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 R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> , R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> , and Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> . 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.

69.1: Image Quality Assessment of Ultra‐High Resolution Mobile Display Utilizing New RGBW Method

AbstractIn this paper, newly‐developed 5.0‐inch full‐HD (1080 × RGBW × 1920) and 7.0‐inch WQXGA (2560 × RGBW × 1600) prototype LCDs utilizing a new RGBW method are described in detail. The assessment of the image quality of the new RGBW technology is described, such as color image reproducibility, white color tracking in the low power mode and tone curve correction in the outdoor bright mode.

The Comprehensive Processing Methods on Reproducing of the Image of Relic on Subtle Levels

Culture relics, as the remains of legacy in the development of human history, are unduplicated. And making the image of relics, therefore, is significant at protecting, studying and appreciating the cultural relics and even promoting the heritage of human civilization. Subtle level of relic image, as the main part for image duplication always reflects original characteristics and texture of the image. The relic’s density is adjusted to the maximum of the visual identification through centering the relics in the image for black and white points calibration. Adjusting tone curve can represent the relic’s texture to satisfy the requirements of the visual artistic appreciation in accordance with the concrete characteristics of the cultural relic’s image. Based on color adjustment, the detail expression and level texture of the relic can be emphasized. Using image processing method furthers refined correction to ensure the whole density of image and equilibrium of the level. Sharpen the image of relics to intensify the subtle level in accordance with Mach Band Effect. These basic principle and method such as level tone and color adjustment combined with the relevant image processing methods is applied comprehensively to the image duplication, which can represent and promote the subtle level of the image as well as the relics’ style with high quality.

Effect of Tone Curve and Size on Kansei Evaluation of High Dynamic Range Images - Comparison of Japanese and Chinese Observers

Effect of Tone Curve and Size on Kansei Evaluation of High Dynamic Range Images - Comparison of Japanese and Chinese Observers

Model-Based Calibration Approach to Improve Tone Consistency for Color Electrophotography

This paper aims to improve tone consistency for color electrophotography (EP). Color accuracy is crucial for printing. Calibrations are performed in EP printers to maintain consistent tone reproduction curves (TRCs). The calibration performance directly impacts the quality of color rendering. In this study, a model-based calibration approach is proposed to stabilize the TRCs. Regression models are developed to predict the primary color TRCs based on operating conditions and/or on-board sensor measurements. During a calibration, TRCs are predicted by the regression models, and the deviation is compensated by adjusting EP control parameters and modifying the tone correction mapping. The effectiveness of the proposed approach is validated using an off-the-shelf in-line four color EP printer under various environmental conditions and consumable factors. The experimental results demonstrate a 63.3% reduction in root-mean-squared error over the existing calibration method. VC 2011 Society for Imaging Science and Technology. [DOI: 10.2352/J.ImagingSci.Technol.2011.55.6.060505] INTRODUCTION The color reproduction quality of an electrophotographic (EP) printing system can be affected by changes in operating conditions. A tone reproduction curve (TRC) is commonly used to characterize the color that is reproduced on the printed media for each primary color. A TRC is obtained by measuring the reproduced color on the output media at a set of predetermined halftone levels. A consistent TRC implies that the reproduced color does not change under different operating conditions. Ensuring the consistency of the TRCs is the first step to ensure consistent color reproduction. Calibrations are performed in an EP system to improve TRC consistency. For an EP engine, tone reproduction on a given media is sensitive to variations in temperature, humidity, air pressure, organic photoconductor (OPC) drum age, throughputs, and other environmental factors and operating conditions. During a calibration, a number of primary color patches are printed on either the internal transfer media or the final output media at a set of predetermined halftone levels. Sensors embedded in the printer measure the printed patches. EP control parameters and the tone correction mapping are adjusted based on these on-board sensor measurements to ensure consistent primary color reproduction. Researchers have proposed approaches to improve tone reproduction consistency. Li and Dianat proposed a calibration routine to minimize least-squared photoconductor TRC errors under various operating conditions using a static linear model between the EP parameters and the sensor values with the presence of disturbances and uncertainty in the system description. Staelin et al. developed machine learning models to improve color reproduction consistency for an HP Indigo digital press. Sim et al. used time-sequential sampling to address the difficulty in generating reliable measurements that span the color gamut of a color EP engine. Totsuka et al. proposed a tone curve Received Sep. 27, 2010; accepted for publication Aug. 8, 2011; published online Dec. 16, 2011 1062-3701/2011/55(6)/060505/9/$20.00. J. Imaging Sci. Technol. Nov./Dec. 2011 060505-1 Journal of Imaging Science and TechnologyV 55(6): 060505-1–060505-9, 2011. VC Society for Imaging Science and Technology 2011

User-Configured Monitor-to-Printer Color Reproduction

Every type of color imaging device has its own color re- production method, providing color characteristic information. Thus, a color management system with an ICC profile is generally used to reproduce colors between two different color imaging devices, for example, from a monitor to a printer. However, once the ICC profile of a device is measured and stored, it usually remains unchanged. Yet, a user can sometimes control the monitor configuration, such as the color temperature, contrast, and brightness, according to their preference, thereby changing the color characteristics of the monitor. In addition, typical end user's viewing condition is not matched to standard environment. In this case, if the user then prints an image on the monitor screen, the color of the printed image will not match the color displayed on the monitor screen, as the color characteristics of the ICC profile provided by the monitor manufac- turer will no longer represent the user-configured color characteris- tics of the monitor. Therefore, this article proposes a method for user-configured monitor-to-printer color reproduction based on an estimation of the monitor characteristics under user's monitor con- figuration and viewing condition. First, the color characteristics ac- cording to change of monitor configuration is measured and mod- eled for the red-green-blue (RGB) chromaticity and tone curve. Second, to estimate the color characteristics of the user's monitor, color matching between a printed color chart and a reproduced color chart image on the monitor screen by soft proofing is accomplished. The RGB chromaticity and tone curve models are used in a soft proofing process for adjusting the monitor's color characteristics. After color matching, color characteristics of the user's monitor are then obtained. Finally, the monitor to printer color reproduction is evaluated based on the color characteristics obtained for the moni- tor. Experimental results using the proposed method show that the printed images have almost the same colors as the images on the real user-configured monitor screen. © 2011 Society for Imaging Science and Technology. DOI: 10.2352/J.ImagingSci.Technol.2011.55.2.020506

Interactive Support System for Image Quality Enhancement Focused on Lightness, Color and Sharpness

An interactive support system for image quality enhancement to adjust display equipments according to the user's own subjectivity is developed. Interactive support system for image quality enhancement enable the parameters based on user's preference to be derived by only selecting user's preference images without adjusting image quality parameters directly. In the interactive support system for image quality enhancement, the more the number of parameters is, the more effective this system is. In this paper, lightness, color and sharpness are used as the image quality parameters and the images are enhanced by increasing the number of parameters. Shape of tone curve is controlled by two image quality adjustment parameters for lightness enhancement. Images are enhanced using two image quality adjustment parameters for color enhancement. The two parameters are controlled in L*a*b* color space. Degree and coarseness of image sharpness enhancement are adjusted by controlling a radius of mask of smoothing filter and weight of adding. To confirm the effectiveness of the proposed method, the image quality and derivation time of the proposed method are compared with a manual adjustment method.

Local Contrast Enhancement Based on Adaptive Multiscale Retinex Using Intensity Distribution of Input Image

As the dynamic range of a digital camera is narrower than that of a real scene, the captured image requires a tone curve or contrast correction to reproduce the information in dark regions. Yet, when using a global correction method, such as histogram-based methods and gamma correction, an unintended contrast enhancement in bright regions can result. Thus, a multiscale retinex algorithm using Gaussian filters was already proposed to enhance the local contrast of a captured image using the ratio between the intensities of an arbitrary pixel in the captured image and its surrounding pixels. The intensity of the surrounding pixels is estimated using Gaussian filters and weights for each filter, and to obtain better results, these Gaussian filters and weights are adjusted in relation to the captured image. Nonetheless, this adjustment is currently a subjective process, as no method has yet been developed for optimizing the Gaussian filters and weights according to the captured image. Therefore, this article proposes local contrast enhancement based on an adaptive multiscale retinex using a Gaussian filter set adapted to the input image. First, the weight of the largest Gaussian filter is determined using the local contrast ratio from the intensity distribution of the input image. The other Gaussian filters and weights for each Gaussian filter in the multiscale retinex are then determined using a visual contrast measure and the maximum color difference of the color patches in the Macbeth color checker. The visual contrast measure is obtained based on the product of the local standard deviation and locally averaged luminance of the image. Meanwhile, to evaluate the halo artifacts generated in large uniform regions that abut to form a high contrast edge, the artifacts are evaluated based on the maximum color difference between each color of the pixels in a patch in the Macbeth color and the averaged color in CIELAB standard color space. When considering the color difference for halo artifacts, the parameters for the Gaussian filters and weights representing a higher visual contrast measure are determined using test images. In addition, to reduce the induced graying-out, the chroma of the resulting image is compensated by preserving the chroma ratio of the input image based on the maximum chroma values of the sRGB color gamut in the lightness&#x2013;chroma plane. In experiments, the proposed method is shown to improve the local contrast and saturation in a natural way.

Optimizing a Tone Curve for Backward-Compatible High Dynamic Range Image and Video Compression

For backward compatible high dynamic range (HDR) video compression, the HDR sequence is reconstructed by inverse tone-mapping a compressed low dynamic range (LDR) version of the original HDR content. In this paper, we show that the appropriate choice of a tone-mapping operator (TMO) can significantly improve the reconstructed HDR quality. We develop a statistical model that approximates the distortion resulting from the combined processes of tone-mapping and compression. Using this model, we formulate a numerical optimization problem to find the tone-curve that minimizes the expected mean square error (MSE) in the reconstructed HDR sequence. We also develop a simplified model that reduces the computational complexity of the optimization problem to a closed-form solution. Performance evaluations show that the proposed methods provide superior performance in terms of HDR MSE and SSIM compared to existing tone-mapping schemes. It is also shown that the LDR image quality resulting from the proposed methods matches that produced by perceptually-based TMOs.

Color Correction by Estimation of Dominant Chromaticity in Multi-Scaled Retinex

In image capture a scene with nonuniform illumination has an influence on the image quality, especially the contrast and detail in dark regions. Generally, the tone curve or histogram of an image is modified to improve the contrast and detail, yet this is insufficient as the intensity and chromaticity of the illumination vary with geometric position. Thus, the multi-scaled retinex algorithm has been proposed, where the influence of nonuniform illumination is reduced by partitioning the original image using local average images that are estimated based on Gaussian filtering of the original image. However, the multi-scaled retinex algorithm produces color distortion as the local average images are independently estimated for each channel. In particular, if the chromatic distribution of the original image is not uniform and is dominated by a certain chromaticity, the local average image includes not only the intensity and chromaticity of the illumination but also the dominant chromaticity through the Gaussian filtering, thereby distorting the color. Accordingly, this article proposes a multi-scaled retinex using a modified local average image to reduce the color distortion by the dominant chromaticity of the original image. As with the multi-scaled retinex algorithm, the local average image is obtained through Gaussian filtering of the original image. The local average image is then divided by the average chromaticity value of the original image to reduce the influence of the dominant chromaticity. However, because the average chromaticity value includes the dominant chromaticity of the original image and the chromaticity of the illumination, the chromaticity removed from the illumination in the local average image needs to be compensated. Therefore, the chromaticity of the illumination is estimated based on the chromaticity of the highlight regions in the original image. The chromaticity of the local average image is then modified by the estimated chromaticity. In experiments, the proposed method was found to improve local contrast and reduce the color distortion.

トーンカーブ補正による感性に基づく対話的高画質化支援システム

トーンカーブ補正による感性に基づく対話的高画質化支援システム

Modeling a Generic Tone‐mapping Operator

AbstractAlthough several new tone‐mapping operators are proposed each year, there is no reliable method to validate their performance or to tell how different they are from one another. In order to analyze and understand the behavior of tone‐mapping operators, we model their mechanisms by fitting a generic operator to an HDR image and its tone‐mapped LDR rendering. We demonstrate that the majority of both global and local tone‐mapping operators can be well approximated by computationally inexpensive image processing operations, such as a per‐pixel tone curve, a modulation transfer function and color saturation adjustment. The results produced by such a generic tone‐mapping algorithm are often visually indistinguishable from much more expensive algorithms, such as the bilateral filter. We show the usefulness of our generic tone‐mapper in backward‐compatible HDR image compression, the black‐box analysis of existing tone mapping algorithms and the synthesis of new algorithms that are combination of existing operators.

Contrast-Gain-Based Visual Tone Mapping for Digital Photo Prints

With the popularization of digital photo printing, there is a demand for print image quality that approaches the quality of silver halide photographs. One way to achieve this is through automatic correction of image luminance/tone. The conventional approach based on spatially invariant mapping often causes undesired luminance changes when enhancing contrast; moreover, luminance changes are also accompanied by changes in contrast. This paper proposes a novel algorithm for the enhancement of the contrast and lightness using spatially variant mapping to achieve high-quality printing of images photographed using digital cameras. First, we define a "contrast-gain" function to quantitatively evaluate the visual contrast that results from tone mapping. Based on this function, the proposed tone mapping algorithm enables independent control of the lightness and contrast through spatially variant processing. Next, we formalize a "shadow-up tone curve," which produces an effect similar to auxiliary lighting during photography. Our contrast-gain-based visual tone mapping method, which uses the shadow-up tone curve in the algorithm, has none of the unnaturalness that arises with a conventional single tone curve. Furthermore, it provides an extremely natural effect similar to that in images photographed by a professional photographer using auxiliary light provided by a reflection board.