Communicating color gamut is very important in color research and application. The problem of calculating image gamut, however, has no definitive solution yet. We propose a new method for calculating the gamut volume by rearranging the color values. The entire color space is firstly divided by hue angle ΔHab and secondly by lightness ΔL where the steps (ΔHab, ΔL) are decided in non-uniform to include the constant color samples in each segmented sectors. And the most out-side points from the center are extracted. In previous paper, the entire gamut volume was calculated by summing up the individual volume of tetrahedral with selected color values, but this volume was calculated bigger than theoretical values. In this paper, ΔL division is changed by lightness angle ΔLangle, and triangle surfaces constructed by each ordered points are decided an outer or inner side. A tetrahedron constructed by inner side surface is assigned a minus volume. As a result, the corresponding color gamuts are exactly calculated and analyzed. This method is available to describe the surface of image color gamut.

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A video printer is suitable to get hard copies of television images, and it has been making much progress in high quality technology with processing image data. We have made some investigations in getting high quality prints. First one is to reject the noise in reduced images, such as thumbnail prints. Another is the method of color comprehension with a television image and a print one.
It is well known to see the high-frequency noise in the thumbnail image without LPF. This LPF is set behind the frame memory and it requires a high dimension digital filter. It needs long time to process the data or much digital circuit. We have got a good thumbnail image with no noises using a mean filter.
There is any mismatch in color reproduction between television images and print images. For printers there needs a kind of color compensation because of color mismatch. We have made some investigations, such as the method for special use of print, non-linear compression from TV color space to printer color space and the method using TV signal processing.

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Recent progresses of digital camera system are very rapid and the image quality of the system is improved very much. On the other hand, conventional silver halides photography is one of important color image recording system. We extract the characteristics of the conventional photography and simulate the characteristics in the digital camera printing system. Simulation method is formulated and is applied to the photography tone transformation. Opinion test is carried out on the transformed print and it is confirmed that photography tone image is printed in the digital camera system.

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Error diffusion method is a major stream in digital halftoning, but unpleasant textures of output images, called “worms” and “fingerprints”, have been prevention of higher halftoning process. In particular, the worms are so noticeable in highlight area that they are major causes of graininess of output image. This paper proposes easy ways to reduce those unpleasant textures and blend advantages of error diffusion and conventional screen. The proposed modified algorithm's main intention is to employ a sine-wave whose amplitude and frequency change suitably according to input pixels. The worms are forced to be arranged by adding the sine-wave's amplitude before thresholding. In this paper, experimental results are reported and the image qualities are discussed as compared with previous methods.

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A new evaluation method for printer resolution by the pixel size estimation using one-dimensional random pattern has been developed. By using a one-dimensional random pattern as input data, the frequency response of a printer system was calculated from the density profile of the output image. The resolutions of several printers based on different marking mechanisms were compared by the present method. Psychological sharpness score of portrait images made by printers and simulated halftone prints can be predicted by estimated pixel size and the image contrasts at hi-light and mid-tone of print

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Printing quality of prints on three types of media paper was examined with ISO13660 draft standards. A thermal resin transfer printer drew test targets in each color of YMCK on three types of media paper i.e. wood-free paper, micro-porous paper and synthetic paper. Four major metrics i.e. Tangential Edge Profile (TEP) and Normal Edge Profile (NEP), area fill percentage reproduction, mottle metrics with ISO13660 draft modified by QEA and graininess metrics with Dooley and Shaw equation, ranked the specimens in descending order of synthetic paper, micro-porous paper and wood-free paper. The results can nearly be explained by the surface roughness. Micro-porous paper, however, showed some characteristic behaviors. The micro-pores in the surface of micro-porous paper seem to bring these features. The micro-pores (1) absorb melt ink into the sheet that brings a blur, (2) insulate thermally that overheat the ink-ribbon leading too much ink transfer, and (3) increase the compressibility of the sheet improving the print quality.

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The measurement system for toner motion in the development process was constructed. By employing laser sheet visualization method, the system can measure individual toner motions around the spaced single component development system in a Laser Beam Printer cartridge. The system can also measure motions of toners developing onto the latent electrostatic image on the photoreceptor. The dependences of toner motions on development bias parameters were measured. Besides the basical characteristics, some defective images, sweep-up at a developed solid image area and fading in between solid black and half-tone, were measured. The results show that the defective images are due to a stretch of the development nip length. In adittion to toner motions, the air flow fields in the development process were measured. Quantifying the toner motions and air flow fields in the development process has allowed us to control the development process and to simulate toner motion more accurately.

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