Ricoh Company, Ltd.

Hideki Kamaji

Hiroyuki Igawa

Naoto Watanabe

Shinji Kobayashi

Shinji Kato

Shin Hasegawa

Kayoko Tanaka

Hitoshi Ishibashi

Kohta Fujimori

Noboru Sawayama

Kazumi Kobayashi

Takashi Enami

Fukutoshi Uchida

Yuushi Hirayama

An image processing apparatus includes a storage and processing circuitry. The storage is configured to store a dither table in which a plurality of dither patterns are recorded, each of the dither patterns being formed with a halftone dot screen in which an output area ratio that is a proportion of void halftone dots per unit area corresponds to any one of gradation values of image data. The processing circuitry is configured to read a gradation value for each region in image data input for each toner color, decide a dither pattern to be applied to the read gradation value, read out the decided dither pattern from the dither table, and perform dither processing of applying the read dither pattern to the region in the image data.

Image processing apparatus, image processing method, and computer-readable recording medium

An image processing apparatus includes: an image determining unit configured to determine a gradation value for each predetermined range in input image data; and a screen generator configured to arrange dot images around a plurality of growth centers in a halftone dot screen to form respective dot blocks if an input area rate indicating a ratio of black to white in dot images at the gradation value is smaller than a value at which an image defect occurs, and form bridges to connect adjacent dot blocks during a smallest gradation number if distances between the adjacent dot blocks decrease to a predetermined value or less along with growth of the dot blocks, to form a void halftone dot image.

Halftone dot screen generation with conditional arrangement of growth centers to form dot blocks and bridges connecting adjacent dot blocks

An image processing apparatus stores a first dither pattern group that includes dither patterns each corresponding to a gradation value in a first range and formed by line screens in which widths of lines are increased with an increase in the gradation value, a second dither pattern group that includes dither patterns each corresponding to a gradation value in a second range higher than the gradation value in the first range, and formed by void dot screens in which number of dots is increased and void regions surrounded by the dots are decreased with an increase in the gradation value, and a third dither pattern group that includes dither patterns for switching from the line screen to the void dot screen, switching to the void dot screen being completed before a first reference gradation value at which an image defect occurs for received image data is reached.

Image processing apparatus and image processing method

An aspect of the invention provides an image forming apparatus storing first, second, and third dither pattern groups. The first group contains a plurality of line screens, each associated with one of gray levels in a first range, varying such that as the gray level increases, the line width increases. The second group contains a plurality of void-dot screens, each associated with one of gray levels higher than those in the first range, varying such that as the gray level increases, dots increase to reduce void portions surrounded by the dots. The third group contains, for switching from the line screen to the void-dot screen, a plurality of dither patterns varying such that as the gray level increases from a reference gray level, adjacent lines are connected at joint portions tapered toward tip ends in a manner that a position that gradually advances from the tip ends to basal ends.

Image forming apparatus, and method and device for creating dither patterns

An electrophotographic image output device includes an image processor to receive input image data, and a line screen to represent halftone images and have multiple screen angles respectively allocated to different colors including yellow, magenta, and cyan. The line screen satisfies requirements of (A) a predetermined difference is secured between adjacent two of the multiple screen angles; (B) zero is not allocated to any of the multiple screen angles; and (C) among the multiple screen angles determined by the requirements (A) and (B), a screen angle closest to 90 degrees is allocated to yellow among yellow, magenta, and cyan.

Electrophotographic image output device

An image forming method and apparatus capable of implementing accurately and constantly an improved conversion of the amount of toner adhesion over the entire range of the amount of adhesion. The method includes the steps of computing a normalization value as a relative output ratio of the regular reflection output to a background regular reflection component from the surface extracted from the regular reflection light, in which the regular reflection output is obtained by detecting a plurality of gradation toner patterns with a sensor configured to simultaneously detect regular reflection light and diffuse reflection light; obtaining a diffuse reflection output conversion factor by either (1) subtracting the normalization value multiplied by the diffuse reflection output voltage generated by the surface from the diffuse reflection output voltage, or (2) subtracting the normalization value multiplied by a diffuse reflection output voltage increment, which is computed as the difference between the diffuse reflection output voltage and another diffuse reflection output voltage obtained when a light emitting device is turned off, from the diffuse reflection output voltage increment; and subjecting the relation between the diffuse reflection output conversion factor and the amount of adhesion to a polynomial approximation.

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Kanagawa, Japan

Hideki Kamaji