Visually-favorable tone-mapping with high compression performance

Applications of Digital Image Processing XXXVII, 2014

Tone Mapping Operators (TMOs) compress High Dynamic Range (HDR) content to address Low Dynamic Range (LDR) displays. However, before reaching the end-user, this tone mapped content is usually compressed for broadcasting or storage purposes. Any TMO includes a quantization step to convert floating point values to integer ones. In this work, we propose to adapt this quantization, in the loop of an encoder, to reduce the entropy of the tone mapped video content. Our technique provides an appropriate quantization for each mode of both the Intra and Inter-prediction that is performed in the loop of a block-based encoder. The mode that minimizes a rate-distortion criterion uses its associated quantization to provide integer values for the rest of the encoding process. The method has been implemented in HEVC and was tested over two different scenarios: the compression of tone mapped LDR video content (using the HM10.0) and the compression of perceptually encoded HDR content (HM14.0). Results show an average bit-rate reduction under the same PSNR for all the sequences and TMO considered of 20.3% and 27.3% for tone mapped content and 2.4% and 2.7% for HDR content.

2015

In our proposed model a hybrid method of tone mapping is presented. In this technique, an image of High Dynamic Range (HDR) is employed as input and split up into two layers i.e. base and detail layer. The details of HDR image will be preserved because only the base layer's contrast is brought down. A bilateral filter is used to obtain the base layer. Along the base layer the logarithmic compression is used and a bias power function is employed so that the logarithmic base can be varied adaptively and the contrast remains preserved. This tone mapping technique produces a high quality tone mapped image as specified in given experimental results.

2014 IEEE International Conference on Multimedia and Expo (ICME), 2014

Tone Mapping Operators (TMOs) transform High Dynamic Range (HDR) contents to address Low Dynamic Range (LDR) displays. However, before reaching the end-user, these contents are usually compressed using a codec (coderdecoder) for broadcasting or storage purposes. Achieving the best trade-off between rendering and compression efficiency is of prime importance. Any TMO includes a rounding quantization to convert floating point values to integer ones. In this work, we propose to modify this quantization to increase the compression efficiency of the tone mapped content. By using a motion compensation, our technique preserves the rendering intent of the TMO while maximizing the correlations between successive frames. Experimental results show that we can save up to 12% of the total bit-rate as well as an average bit-rate reduction of 8.5% for all the test sequences. We show that our technique can be applied to other applications such as denoising.

2006

The problem of reproducing high dynamic range images on devices with restricted dynamic range has gained a lot of interest in the computer graphics community. There ex- ist various approaches to this issue, which span several re- search areas including computer graphics, image process- ing, color science, physiology, neurology, psychology, etc. These approaches assume a thorough knowledge of both the

2012

In order to view wide contrast details in an image scene, a wide dynamic range (WDR) image sensor is required. However, these wide dynamic range images cannot be accurately viewed on a regular display device due to its limited dynamic range. Without the proper use of a WDR image compression algorithm, the details of images will be lost. Tone-mapping algorithms are used to adapt the captured wide dynamic range scenes to the low dynamic range displays available. This paper explores the utilization of an exponent-tone mapping algorithm for colored and monochrome WDR images in lure of a regular display. The exponent-based tone mapping algorithm utilizes only the Bayer (CFA) of the WDR image to produce tone mapped image results. High quality results are achieved without the use of additional image processing techniques such as histogram clipping. The image results are then compared with other conventional tone mapping operators available.

IEEE Access

A new tone-mapping algorithm is presented for visualization of high dynamic range (HDR) images on low dynamic range (LDR) displays. In the first step, the real-world pixel intensities of the HDR image are transformed to a perceptual domain using the perceptual-quantizer (PQ). This is followed by construction of the histogram of the luminance channel. Tone-mapping curve is generated from the cumulative histogram. It is known that histogram-based tone-mapping approaches can lead to excessive stretching of contrast in highly populated bins, whereas the pixels in sparse bins can suffer from excessive compression of contrast. We handle these issues by restricting the pixel counts in the histogram to remain below a defined limit, determined by a uniform distribution model. The proposed method is compared with state-of-the-art algorithms, using some well-known metrics that quantify the quality of tone-mapped images, and is found to have the best performance. INDEX TERMS Image enhancement, high dynamic range imaging, tone-mapping, image visualization.

Computers & Graphics, Elsevier, ISSN 0097-8493, Vol. 32, Issue 3, p. 330-349, 2008., 2008

The problem of reproducing high dynamic range images on devices with restricted dynamic range has gained a lot of interest in the computer graphics community. There exist various approaches to this issue, which span several research areas including computer graphics, image processing, color vision, physiological aspects, etc. These approaches assume a thorough knowledge of both the objective and subjective attributes of an image. However, no comprehensive overview and analysis of such attributes has been published so far. In this contribution, we present an overview about the effect of the basic image attributes in the HDR tone mapping. Furthermore, we propose a scheme of relationships between these attributes, leading to the definition of an overall image quality measure. We present results of subjective psychophysical experiments that we have performed to prove the proposed relationship scheme. Moreover, we also present the evaluation of existing tone mapping methods (operators) with regard to these attributes. Finally, the execution of with-reference and without a real reference perceptual experiments gave us the opportunity to relate the obtained subjective results. Our effort is not just useful to get into the tone mapping field or when implementing a tone mapping operator, but it also sets the stage for well-founded quality comparisons between tone mapping operators. By providing good definitions of the different attributes, user-driven or fully automatic comparisons are made possible at all.

Proceedings of the 24th Spring Conference on Computer Graphics, 2010

Figure : The HDR image compressed using two variants of our gradient domain tone mapping operator: contrast mapping (center) and contrast equalization (right). For comparison the gamma compressed image is depicted (left).

RealReflect report D, 2004

The need of tone mapping high dynamic range (HDR) images has highly increased recently because they are useful not only for static images but also for multimedia applications. Therefore, how to produce visually sufficient HDR images has been one of the important discussions in the computer graphics community for years against the problems which come from the limited number of bits in image formats and the limited display range of the physical devices. A number of techniques have been introduced to conquer those problems including construction ...

with the developments in Image acquisition techniques there is an increasing interest towards High Dynamic Range (HDR) images where the number of intensity levels ranges between 2 to 10 4 . Tone Mapping Operator (TMO) is used to convert the HDR image into Low Dynamic Range (LDR) images that can be visualized clearly there are different operators offered in the HDR tool box. The outputs of the operators are discussed in the paper with the objective analysis. Newly Logarithmic TMO and Exponential TMO are proposed and evaluation is done. Which are being compared with individual TMOs, give better results in quality metrics.