Hierarchical tone mapping based on image colour appearance model

People always try to reconstruct images that look like original scene. But it is not succeeded up to the expected level because the display devices cannot accommodate the actual range of illumination. The original scene is having high dynamic range (HDR) and the display devices are having low dynamic range (LDR) of values. Tone mapping can be used to display HDR image in an LDR device. In this paper we are trying to develop a better tone mapping method. A number of images with different exposure are fused to form an HDR image.. Here we used average method for this which is the simplest one. Then by using tone mapping the HDR image is converted into LDR. We tried Tone Reproduction Curve (TRC) based global tone mapping. TRC method results faster operation The global tone mapping operator algorithm is simple and does not introduce ghosting. The image will also free from blur and halo like artifacts. We took log average of the images to keep the pixel values within limit. Index Terms: Image fusion, High dynamic range images, , Tone mapping. Low dynamic range image, global operator.

Tone mapping operators (TMOs) employed to visualize high dynamic range (HDR) content on conventional low dynamic range (LDR) devices suffer from two major drawbacks. First, none of them can faithfully reproduce all the contrast present in HDR images. Second, most of them require one or more parameters which are mostly content specific and their optimal values can be set only via subjective testing. To address these issues, this paper proposes that 'quality driven' adaptive contrast enhancement is a practical solution. This is achieved by enhancing the contrast adaptively based on the loss of contrast between the HDR and tone mapped image. Experimental results confirm that the proposed adaptive solution always improves upon the contrast achieved from whatever given TMO parameter settings in the tested images. So it helps to achieve the results of a more optimal TMO parameter setting without the human input.

Human Vision and Electronic Imaging VIII, 2003

A tone mapping algorithm for displaying high contrast scenes was designed on the basis of the results of experimental tests using human subjects. Systematic perceptual evaluation of several existing tone mapping techniques revealed that the most "natural" appearance was determined by the presence in the output image of detailed scenery features often made visible by limiting contrast and by properly reproducing brightness. Taking these results into account, we developed a system to produce images close to the ideal preference point for high dynamic range input image data. Of the algorithms that we tested, only the Retinex algorithm was capable of retrieving detailed scene features hidden in high luminance areas while still preserving a good contrast level. This paper presents changes made to Retinex algorithm for processing high dynamic range images, and a further integration of the Retinex with specialized tone mapping algorithms that enables the production of images that appear as similar as possible to the viewer's perception of actual scenes.

2010

High Dynamic Range (HDR) images can represent the acquired scene with a greater dynamic range of luminance than classical Low Dynamic Range (LDR) ones. Despite the recent diffusion of some HDR camera models, HDR displays are not yet in the market. For this reason HDR images need to be adapted in order to be properly rendered through conventional devices. This operation mainly consists in a dynamic range compression realized by applying a Tone Mapping Operator (TMO). In this work, a new tone map algorithm, derived from the Contrast Limited Adaptive Histogram Equalization (CLAHE) technique, is presented. With respect to the original CLAHE, in the proposed implementation an adaptive contrast limit and a new strategy for the determination of local tone mapping functions have been introduced. The comparison between the obtained LDR images, and those produced by applying State of the Art TMOs, evidences how the main characteristic of the proposed algorithm is the ability to equally enhance visibility in both dark and bright areas. This could be, for example, a key feature in video surveillance applications and automotive safety camera systems.

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.

2013 8th International Symposium on Image and Signal Processing and Analysis (ISPA), 2013

If a photograph is reproduced "faithfully", i.e. preserving the relative colorimetric values of the original scene, the resulting image will often look less colorful and less contrasted than the original scene due to some mechanisms of the human visual system. Film and digital cameras must compensate these effects in order to obtain visually pleasing images, which reproduce the appearance of the original scene. This problem occurs also in high dynamic range (HDR) photography, and tone mapped images may appear slightly hazy if the aforementioned visual effects are not compensated. In this paper we shall briefly recall the technique used by most cameras (both film-based and digital) and show one possible theoretical motivation based on a model of brightness perception. We shall then propose a simple technique which compensates the loss of colorfulness and contrast in tone mapped images, and show in particular how this technique can be combined with a tone mapping operator we recently proposed. Finally, we shall compare the results with those produced by a related method.

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

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.

2007

We propose a general hybrid approach to the issue of reproduction of high dynamic range images on devices with limited dynamic range. Our approach is based on combination of arbitrary global and local tone mapping operators. Recent perceptual studies concerning the reproduction of HDR images have shown high importance of preservation of overall image attributes. Motivated by these findings, we apply the global method first to reproduce overall image attributes correctly. At the same time, an enhancement map is constructed to guide a local operator to the critical areas that deserve enhancement. Based on the choice of involved methods and on the manner of construction of an enhancement map, we show that our approach is general and can be easily tailored to miscellaneous goals of tone mapping. An implementation of proposed hybrid tone mapping produces good results, it is easy to implement, fast to compute and it is comfortably scalable, if desired. These qualities nominate our approac...

Proceedings of SPIE, 2011

High dynamic range (HDR) imaging seems to have developed to a level of soon being a standard feature in consumer cameras. This study was motivated by the need for evaluating tone mapping operators especially for consumer imaging applications. A no-reference method based on ISO 20462-2:2005 triplet comparison was created for evaluating tone mapping operators. Multiple HDR test images were photographed and the method was validated by evaluating 25 tone mapping operators with five test images. Tone mapping operators were evaluated based on image naturalness and pleasantness. The results indicate that the method successfully ranked the method in terms of naturalness and pleasantness. The test image set could be improved for example based on an imaging photo space for HDR photography. The test images of this study are available for non-commercial research purposes.