Prof. Yasushi Yamaguchi Profile

Prof. Yasushi Yamaguchi

Professor at Univ of Tokyo

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Publications (4)

SPIE Journal Paper | 18 August 2017

Synthesis and assessment methods for an edge-alignment-free hybrid image

Peeraya Sripian, Yasushi Yamaguchi

JEI, Vol. 26, Issue 04, 043016, (August 2017) https://doi.org/10.1117/12.10.1117/1.JEI.26.4.043016

KEYWORDS: Spatial frequencies, Visualization, Contrast sensitivity, Visual system, Image filtering, Statistical analysis, Image enhancement, Distance measurement, Image compression, Modulation

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A hybrid image allows multiple image interpretations to be modulated by the viewing distance. It can be constructed on the basis of the multiscale perceptual mechanisms of the human visual system by combining the low and high spatial frequencies of two different images. The hybrid image was introduced as an experimental tool for visual recognition study in terms of spatial frequency perception. To produce a compelling hybrid image, the original hybrid image synthesis method could only use similar shapes of source images that were aligned in the edges. If any two different images can be hybrid, it would be beneficial as a new experimental tool. In addition, there is no measure for the actual perception of spatial frequency, whether a single spatial frequency or both spatial frequencies are perceived from the hybrid stimulus. This paper describes two methods for synthesizing a hybrid image from dissimilar shape images or unaligned images; this hybrid image is known as an “edge-alignment-free hybrid image.” A noise-inserted method can be done by intentionally inserting and enhancing noises into the high-frequency image. With this method, the low-frequency blobs are covered with high-frequency noises when viewed up close. A color-inserted method uses complementary color gratings in the background of the high-frequency image to emphasize the high-frequency image when viewed up close, whereas the gratings disappear when viewed from far away. To ascertain that our approach successfully separates the spatial frequency at each viewing distance, we measured this property using our proposed assessment method. Our proposed method allows the experimenter to quantify the probability of perceiving both spatial frequencies and a single spatial frequency in a hybrid image. The experimental results confirmed that our proposed synthesis methods successfully hid the low-frequency image and emphasized the high-frequency image at a close viewing distance. At the same time, the perception of the low-frequency image was not disturbed when the image was viewed from far away.

Proceedings Article | 17 January 2005 Paper

Device-dependent color neutralization method

Mizuho Nakajima, Yasushi Yamaguchi

Proceedings Volume 5667, (2005) https://doi.org/10.1117/12.587608

KEYWORDS: Visualization, Printing, Cryptography, Visual process modeling, Opacity, Computer simulations, Binary data, Image quality, Colorimetry, Computer graphics

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SPIE Journal Paper | 1 July 2004

Enhancing registration tolerance of extended visual cryptography for natural images

Mizuho Nakajima, Yasushi Yamaguchi

JEI, Vol. 13, Issue 03, (July 2004) https://doi.org/10.1117/12.10.1117/1.1758729

KEYWORDS: Visualization, Cryptography, Transparency, Tolerancing, Image registration, Binary data, Opacity, Image enhancement, Information security, Image quality

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Proceedings Article | 17 June 2003 Paper

Registration-tolerant extended visual cryptography

Mizuho Nakajima, Yasushi Yamaguchi

Proceedings Volume 5007, (2003) https://doi.org/10.1117/12.473920

KEYWORDS: Transparency, Visualization, Cryptography, Image registration, Opacity, Binary data, Tolerancing, Image quality, Image enhancement, Visual process modeling

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