Kinjiro Amano | The University of Manchester (original) (raw)

Papers by Kinjiro Amano

Vision Research, Mar 1, 2012

There is no standard method for classifying eye fixations. Thresholds for speed, acceleration, du... more There is no standard method for classifying eye fixations. Thresholds for speed, acceleration, duration, and stability of point of gaze have each been employed to demarcate data, but they have no commonly accepted values. Here, some general distributional properties of eye movements were used to construct a simple method for classifying fixations, without parametric assumptions or expert judgment. The method was primarily speed-based, but the required optimum speed threshold was derived automatically from individual data for each observer and stimulus with the aid of Tibshirani, Walther, and Hastie's 'gap statistic'. An optimum duration threshold, also derived automatically from individual data, was used to eliminate the effects of instrumental noise. The method was tested on data recorded from a video eye-tracker sampling at 250 frames a second while experimental observers viewed static natural scenes in over 30,000 one-second trials. The resulting classifications were compared with those by three independent expert visual classifiers, with 88-94% agreement, and also against two existing parametric methods. Robustness to instrumental noise and sampling rate were verified in separate simulations. The method was applied to the recorded data to illustrate the variation of mean fixation duration and saccade amplitude across observers and scenes.

Journal of Vision, Sep 1, 2018

Hyperspectral radiance data. The zipped file contains an unaveraged hyperspectral radiance image ... more Hyperspectral radiance data. The zipped file contains an unaveraged hyperspectral radiance image in Matlab MAT format, size 1024 × 1344 × 33, and spectral radiance in W m−2 sr−1 nm−1. The image is one of a pair of images acquired at different times. The zipped file also contains a BMP colour image, rendered from the radiance image, and an information document, which includes geographic location. The separate JPG image of the scene is for illustration only. Padding artefacts may be visible at the image edges. The hyperspectral images were acquired by Sérgio Nascimento, Kinjiro Amano, and David Foster from the Minho region of Portugal in 2002 and 2003.

Naïve observers viewed a sequence of colored “Mondrian ” patterns, simulated on a color monitor. ... more Naïve observers viewed a sequence of colored “Mondrian ” patterns, simulated on a color monitor. Each pattern was presented twice in succession, first under one daylight illuminant of color temperature either 16000 K or 4000 K, and then under the other, to test for color constancy. Observers compared the central square of the pattern across illuminants, either rating it for sameness of material appearance, or for sameness of hue and saturation, or judging an objective property, that is, whether its change of color originated from a change in material or only in illumination. Average color-constancy indices were high for materialappearance ratings and binary judgments of origin, and low for hue-saturation ratings. Individuals ’ performance varied, but judgments of material and of hue and saturation remained demarcated. Observers seem able to separate phenomenal percepts from their ontological projections of mental appearance onto physical phenomena: thus, even when a chromatic change...

i-Perception, Mar 1, 2020

We estimated Trump's skin colour from 70 internet images and also from the "twitter tan line" ima... more We estimated Trump's skin colour from 70 internet images and also from the "twitter tan line" image (February 8, 2020; Twitter). We then compared the estimated skin colours with two existing data sets of skin colours: the range of skin tans that occur naturally in the Caucasian population and the range skin colours brought about by a sunless tan. We find that Trump's skin colour is close to the edge of the natural skin tan gamut and firmly within the gamut of a sunless skin tan. The skin colour above Trump's tan line is outside of the naturally occurring range of skin colours, even outside the skin tan of nonmelanized albinos. The latter finding is consistent with the hypothesis that part of the image may have been digitally distorted.

is a sample cover image for this issue. The actual cover is not yet available at this time.) This... more is a sample cover image for this issue. The actual cover is not yet available at this time.) This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

Vision Research, Mar 1, 2012

Journal of Vision, Sep 1, 2018

i-Perception, Mar 1, 2020

Accurate geometrical and spatial information of the built environment can be accurately acquired ... more Accurate geometrical and spatial information of the built environment can be accurately acquired and the resulting 3D point cloud data is required to be processed to construct the digital model, Building Information Modelling (BIM) for existing facilities. Point cloud by laser scanning over the buildings and facilities has been commonly used, but the data requires external information so that any objects and materials can be correctly identified and classified. A number of advanced data processing methods have been developed, such as the use of colour information to attach semantic information. However, the accuracy of colour information depends largely on the scene environment where the image is acquired. The limited number of spectral channels on conventional RGB camera often fails to extract important information about surface material, despite spectral surface reflectance can represent a signature of the material. Hyperspectral imaging can, instead, provide precise representation of spatial and spectral information. By implementing such information to 3D point cloud, the efficiency of material detection and classification in BIM should be significantly improved. In this work, the feasibility of the image integration and discuss practical difficulties in the development.

Skin color provides essential information about an individual's health condition and emotion. Add... more Skin color provides essential information about an individual's health condition and emotion. Additive manufacturing of human skin has been developed markedly in recent years along with increasing demands for clinical and medical applications. It is therefore critical to achieve precise color reproduction of facial skin and constant color appearance under different illuminations particularly for the application to maxillofacial prostheses. In this study, the color quality of 3D facial prostheses under various illuminations was assessed by measuring human perceptual error, quantified by the color difference metric CIEDE2000, and an index for color constancy. The index was calculated in the same manner as a standard color-constancy index. Thus, in a color space, where the chromaticity coordinates of real skin and artificial skin were located, let a be the distance between real skin and artificial skin colors under a test illuminant and let b be the distance between the real skin color under test and reference illuminants, then the index is 1 – a/b. Perfect constancy corresponds to unity and the greater the error, the lower the index. 3D facial prostheses of three human subjects, one Caucasian and two Chinese, were generated by an additive manufacturing with an elaborated color management from 3D color digital imaging to 3D printing. Colors of the 3D prostheses and subjects' real skin were compared with a spectrophotometer. Mean color difference CIEDE2000 over subjects was approximately 7.2 (a Caucasian 5.7, two Chinese 7.9), slightly larger than the conventional values of acceptable perceptual error (4.0). Despite these differences, color constancy indices between selected CIE standard illuminants (D65, A, F2, F11) ranged over 0.57–0.84, close to values from traditional color-constancy experiments with human observers. The color quality of facial prostheses in modern additive skin manufacturing may be as good perceptually as that of real human skin, even under different scene illuminations. Meeting abstract presented at VSS 2017

The response of the human eye to incident light has two components: one image-forming and one non... more The response of the human eye to incident light has two components: one image-forming and one non-image-forming. The image-forming response follows luminance spectral sensitivity, peaking at approximately 550 nm, and the non-image-forming response follows melanopsin spectral sensitivity, peaking at approximately 480 nm. But the two signals may be interdependent, especially in natural scenes with large illumination variations. To test this hypothesis, luminance and melanopsin signals were computed in over 32 hyperspectral radiance images of vegetated and non-vegetated outdoor scenes under natural lighting, with correlated colour temperature 3,000 K to 20,000 K within scenes, and in time-lapse images with daylight correlated colour temperature 3,000 K to 7,500 K. With allowance for prereceptoral lens absorption, luminance and melanopsin signals were computed at each pixel and grouped into 64 patches of 155 × 125 pixels within each 1240 × 1000 pixel image, corresponding at the camera to approximately 7° visual angle, and their correlation quantified. Across scenes, mean R2 over patches ranged from 76% to 99%. Within scenes, R2 varied more widely, with minimum less than 10%. These results suggest that although the two signals are broadly correlated, the predictability of melanopsin signals from luminance signals in any given scene is limited, presumably owing to the complexity of natural scenes. A partial report of these findings was presented at the January meeting of the Colour Group of Great Britain, London, 2017.