Most tone reproduction operators focus on luminance compression, ignoring chromatic assets. The humanvisual system, however, alters color perception according to the overall level of luminosity. This paper proposes an extensionfor existing operators to simulate chromatic changes under mesopic vision. In such conditions, red responses tend to fadefaster than the remaining stimuli, producing a blue-shift phenomenon known as the Purkinje E ect. Starting with a highdynamic range image, the proposed method proceeds by separating luminance and chrominance components. Luminancecompression is performed by means of any already existing operator, though in this paper, for convenience, the photographicoperator was employed. Chromatic changes are handled in a decoupled fashion according to overall average luminance and byfollowing the observations of previous psychophysical experiments. Finally, compressed luminance and adjusted chrominanceare combined together, providing a displayable, low-dynamic range image. The technique has a low fingerprint thus beingsuitable for interactive rendering.

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We propose a nonphotorealistic rendering method for generating halftone images with noncrossing line segments. We first compute a shortest Hamiltonian cycle that passes through all points of a stippling and then draw the line segments in the cycle at intervals of one to obtain a halftone image. We also propose a brightness correction method for the halftone image based on a hexagonal lattice approximation of centrodal Voronoi diagrams. Experimental results show that the halftone images obtained by the proposed method can eproduce the true continuous tone of input images.

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A photomosaic is a type of decorative art made up from various other photographs. We present a method for quickly generating photomosaics and propose an interactive recursive photomosaic system. Users can operate the system by using a wall display with a touch input function, which allows them to alter the appearance of the image dynamically.

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In this paper we present a method for generating sketch-like images from vector images. Most previous non-photorealistic rendering works especially generating paint-like images were intended to reproduce the effect of painting materials, while this research focuses on how to draw a rough sketch. Our method focused on the curvature of the outline of vector images. We assumed that difficulty of drawing affects the strokes. We implemented software for converting vector images to rough sketch-like images using a model based on this concept.

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For the material design of antiferromagnetic layer enabling to reduce the read gap length of magnetic recording heads, the exchange bias between the ferromagnetic (FM) and antiferromagnetic (AFM) bilayer was investigated within the framework of the classical Heisenberg model. The dependence of the exchange bias on the AFM layer thickness was also calculated using the Landau-Lifshitz-Gilbert equation. The triple-Q (3Q), T1, and AF-I spin structures are obtained in the disordered γ-phase, ordered L1₂-, and L1₀-type lattices, respectively. The exchange bias is caused by the formation of the interfacial domain wall in the AFM layer, and the critical thickness d_c of the AFM layer is dominated by the varied spin structures. Consequently, the relation of the critical thickness can be represented as √3d_c^3Q = √2d_c^T1 = d_c^AF-I.

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