Showing papers by "Yoichi Miyake published in 2001"

Perceptual color difference metric for complex images based on Mahalanobis distance

Abstract: In this paper, a perceptual color difference is presented as an alternative color difference metric for complex images instead of the conventional color difference equations. This color difference is derived based on Mahalanobis distance by using covariance matrices for differences of each color attribute. The covariance matrices for each class of images can be obtained by psychophysical experiments using just noticeable difference in paired comparisons. We compared the resultant matrices for different class of images and the information in the matrix can give very useful trends and clues about which kind of transformation can minimize the perceptual color difference in images when a transformation such as gamut mapping is required.

Mapping pigmentation in human skin from a multi-channel visible spectrum image by inverse optical scattering technique

Abstract: Mapping pigmentation in human skin is expected to give useful information in reproducing skin color and enhancing the ability to diagnose various skin disease. In this research, maps of melanin, oxy-hemoglobin and deoxy-hemoglobin in skin are estimated from multi-channel visible spectrum image by using an inverse optical scattering technique. In the inverse optical scattering technique, first of all, a forward model of optical scattering is built to simulate the spectral reflectance of skin. Changing the variable parameters in the forward model, we repeat the simulation until the simulated spectral reflectance matches with the spectral reflectance at each pixel of the multi-spectral image. The principle of the proposed estimation technique was confirmed by imaging the human forearm under conditions of the venous occlusion, the venous and arterial occlusion, and by imaging a slapped region of the human forearm.

Development of goniophotometric imaging system for recording reflectance spectra of 3D objects

Abstract: In recent years, it is required to develop a system for 3D capture of archives in museums and galleries. In visualizing of 3D object, it is important to reproduce both color and glossiness accurately. Our final goal is to construct digital archival systems in museum and internet or virtual museum via World Wide Web. To achieve our goal, we have developed gonio-photometric imaging system by using high accurate multi-spectral camera and 3D digitizer. In this paper, gonio-photometric imaging method is introduced for recording 3D object. 5-bands images of the object are taken under 7 different illuminants angles. The 5-band image sequences are then analyzed on the basis of both dichromatic reflection model and Phong model to extract gonio-photometric property of the object. The images of the 3D object under illuminants with arbitrary spectral radiant distribution, illuminating angles, and visual points are rendered by using OpenGL with the 3D shape and gonio-photometric property.

Real-time Multi-Spectral Image Processing for Mapping Pigmentation in Human Skin.

Abstract: Real-time mapping pigmentation in human skin is expected to give useful information for reproducing various skin colors and monitoring human conditions in real time. In this research, the maps of melanin, oxy-hemoglobin and deoxy-hemoglobin densities in skin are estimated and displayed in real time from digital video signals by using three pre-computed look up tables for color conversions. As the experiments to show the effectiveness of the proposed system, time dependent changes of pigmentation map in human hand are observed during the occlusion and release of middle finger, also during anaerobic by squat exercise. From the results of the experiments, human homeostasis for disturbance can be observed in real time. Introduction Mapping pigmentations such as oxy-hemoglobin and deoxy-hemoglobin in human skin is expected to give us helpful information about human condition and emotion. The obtained information will be used for skin diagnosis, skin color reproduction, measurement of human emotion[1, 2]. We have already proposed the technique to extract qualitative information and spatial distribution of pigmentations from multi-channel visible spectral image[3, 4, 5] by inverse optical scattering technique[1]. The Monte Carlo simulation of photon migration is used as forward model of optical scattering, nd the forward model isa iterated to perform the inverse optical scattering technique based on non-linear optimization method. This technique needs a long time to complete the process. However, a real-time processing is required in measuring changes of human condition and emotion. In this research, we introduce the technique of real-time mapping pigmentation in human skin by using three pre-computed look up tables for color conversions. The first table converts RGB values from digital video camera into three scores for three principal components. Wiener estimation is used to make the table between the RGB values and spectral reflectance which is analyzed into the three scores based on the pre-computed principal components. The second table converts the scores into pigmentation values by using inverse optical scattering technique. Since the values of scores effectively reflect the spectral variation of reflectance spectra, the second table is considered very effective to estimate the pigmentation values. It isnoted this conversion from scores to pigmentations is originally proposed in this research. The third table converts the pigmentation values into RGB values to display on a monitor. The first and third tables are dependent on devices and environment, and he second ttable is independent. It is noted that the total process is constructed from the three tables to separate the device independent process and devices dependent process, because making the second tables takes about 10 days by Monte Carlo simulation of human skin model[6, 7, 8, 9] and so on. Two experiments are performed to show the effectiveness of our system with time dependent changes of pigmentation map in human hand. Pigmentations are observed during putting hand up and down, occlusion and release of middle finger, and anaerobic by squat exercise.

Image evaluation and analysis of ink jet printing system (I): MTF measurement and analysis of ink jet images

Abstract: In this study, the modulation transfer functions of prints, which included both mechanical and optical dot gain effects were measured from samples printed by an ink jet printer on glossy-coated, matte-coated and uncoated papers. The MTF of prints were measured from sinusoidal patterns and Fourier transforms of line spread functions from one-pixel line and step images. The MTF of prints by three measurement methods were analyzed and compared. The one-pixel line method was chosen to compare MTF of prints on different types of papers and printing directions. In addition, MTF of papers were also measured by contact sinusoidal pattern on papers. The point spread function of ink on each paper was estimated by using the measured point spread function of paper in the reflection image model. The results showed that glossy-coated ink jet paper had low MTF of paper but high MTF of print. Finally, printed densities of ink jet images were predicted using the estimated point spread function of ink and measured point spread function of paper. Because the spread function of ink was estimated as having a Gaussian distribution, which does not correctly represent the real point spread function of ink jet printing, the predicted density did not fit well with the measured density.

Correlation map analysis between appearances of Japanese facial images and amount of melanin and hemoglobin components in the skin

Abstract: Skin color reproduction becomes increasingly important with the recent progress in various imaging systems. In this paper, based on subjective experiments, correlation maps are analyzed between appearance of Japanese facial images and amount of melanin and hemoglobin components in the facial skin. Facial color images were taken by digital still camera. The spatial distributions of melanin and hemoglobin components in the facial color image were separated by independent component analysis of skin colors. The separated components were synthesized to simulate the various facial color images by changing the quantities of the two separated pigments. The synthesized images were evaluated subjectively by comparing with the original facial images. From the analysis of correlation map, we could find the visual or psychological terms that are well related to melanin components influence the appearance of facial color image.

Evaluation of Image Quality on Reflective-type LCD: Calibration Based on the PCA.

Abstract: A new measurement method of EOTF (Electro Optical Transfer Function) based on the PCA (Principal Component Analysis) is proposed for colorimetry of RLCD (Reflective type Liquid Crystal Display). Spectral radiance of primary color with different reflectance displayed onto the RLCD under D65 illuminant were measured and analyzed by PCA. It is shown that the reflectance spectra of arbitrary color on the RLCD can be estimated with high accuracy by using those obtained eigen vectors. The new model named PCA model is compared to the conventional GOG (Gain Offset Gamma) model. As a result, it is shown that the PCA model is very significant to the colorimetry of both RLCD and CRT. Introduction In recent years, many kinds of display and printer have been developed to get color image with high quality. Therefore, it is increased to exchange and transform color picture between different devices, particularly from color image onto the CRT and LCD to printer. Therefore it has become increasingly important to do the research on the color management and it is required to develop accurate method for colorimetry of CRT and LCD. One of the most important characteristics of EOTF is a transfer function from digital data to XYZ tristimulus values and spectral radiance of display devices. GOG-model defined as Eq.1 has been widely used to colorimetry of CRT.