Abstract: It is intended to provide an image forming apparatus and image forming method capable of partial magnification corrections on various partial variations of magnification as well as constant and uniform positional shift regardless of any sections. A modulated image clock of a reference color (black) is generated from a clock generated at an image clock generating section 23 and an address is generated at an address generating circuit 36 basing on the modulated image clock. Output sections 30 for respective colors other than the reference color read out correction coefficients from correction coefficient memories 15 of respective colors following the address generated. Frequency modulator circuits 31 modulate image clocks in accordance with correction coefficients. PWM 33 outputs a driving pulse to a laser driver 6 basing on modulated image clocks synchronized with a reference signal 40 by synchronizer circuits 32 and inputted image data.

Abstract: An image forming apparatus comprising a buffer memory for storing image data, a printer unit for printing based on image data output from the buffer memory, a compression unit for compressing image data output from the buffer memory to generate compression data, a hard disk for storing the compression data compressed by the compression unit, and output unit for outputting compression data from the hard disk to the buffer memory, and an expansion unit for expanding the compression data output from the buffer memory and outputting the expansion data to the printer unit. When printing multiple copies, image data are highly compressed and stored on a hard disk, and output directly to a buffer memory in a highly compressed state. Thereafter, the data are expanded and transmitted to the printer. As a result, multiple copy printing is accomplished at high speed.

Abstract: In the image processing apparatus, image data is divided into large blocks of a prescribed size and the large blocks are subdivided into small blocks by the dividing unit. The number of isolated points in each large block is then calculated by the large block isolated point calculation unit, and the number of isolated points in each small block is then calculated by the small block isolated point calculation units. It is then determined by the halftone-dot region determination unit whether or not the large block is a halftone-dot region. This determination considers both the number of isolated points in the large block and the number of isolated points in each small block.

Abstract: In an image forming apparatus, a black edge of a document image is emphasized, and the black edge is detected by deciding an edge from the lightness data and by deciding a black color from the chroma data. The data of cyan, magenta and yellow of a pixel at a black edge are replaced with minima of data of cyan, magenta and yellow of pixels in a prescribed region around the pixel. In order to prevent erroneous decision of a black edge, if a number of isolated pixels is larger than a threshold level, a decision as a pixel at a black edge is invalidated. Automatic exposure can be performed on a color document for correcting a background of the document obtained in a prescan. The background level of the document is determined only on pixels decided to be black. When color balance is adjusted on one of the data of cyan, magenta, yellow and black, the density is kept constant.

Abstract: Image distortion is corrected in a color printer wherein print units for a plurality of colors are aligned to form a color image by superposing images formed by the print units. A quantity of image distortion is detected, and correction data of main scan address and subscan address are calculated and stored according to the detected image distortion for each main scan address. When input color image data are corrected, printing position is corrected in combination of address change with density interpolation. When the correction data exceeds the maximum correction range, the correction data are replaced by the maximum in the correction range to utilize the capability of the distortion correction of the printer. Further, in the image data correction, after the image data are converted to data having a smaller number of gradation levels, the data are delayed according to the serial arrangement of the print units. Then, the delayed data are converted again for printing.

Abstract: It is intended to provide an image forming apparatus and image forming method capable of partial magnification corrections on various partial variations of magnification as well as constant and uniform positional shift regardless of any sections. A modulated image clock of a reference color (black) is generated from a clock generated at an image clock generating section 23 and an address is generated at an address generating circuit 36 basing on the modulated image clock. Output sections 30 for respective colors other than the reference color read out correction coefficients from correction coefficient memories 15 of respective colors following the address generated. Frequency modulator circuits 31 modulate image clocks in accordance with correction coefficients. PWM 33 outputs a driving pulse to a laser driver 6 basing on modulated image clocks synchronized with a reference signal 40 by synchronizer circuits 32 and inputted image data.

Abstract: 1,800 dpi binary image data is divided into 3-bit data groups or 2-bit data groups, and is input from an input unit 11 to a tone setting unit 12 and a print position controller 13. Each group of 3-bit image data is converted into 8-bit tone data and 2-bit attribute data by the tone setting unit 12 and the print position controller 13, respectively, and both sets of post-conversion data are input to a pulse width modulation unit 15 at the same time. Because all 3-bit data is handled at the same time, the input and output operation clock signals can stay the same as for a 600 dpi resolution.

Abstract: In an image forming apparatus, a color registration error correction computing portion calculates optimal typical value of position change quantity for each image forming region. Based on these typical values, write timing at each of write portions is controlled by an image control portion. That is, color registration error correction is executed based on optimal correction quantity for each image forming region.

Abstract: In order to improve character edge reproducibility in reproducing a color document image, a boundary between a character and a background is detected in color image data. Further, if the detected edge exists at the side of a character, it is decided as a true edge, and the image data are subjected to edge emphasis. Then, when an image is reproduced, undesirable partial whitening in characters in the image can be prevented.

Abstract: Image distortion is corrected in a color printer wherein print units for a plurality of colors are aligned to form a color image by superposing images formed by the print units. A quantity of image distortion is detected, and correction data of main scan address and subscan address are calculated and stored according to the detected image distortion for each main scan address. When input color image data are corrected, printing position is corrected in combination of address change with density interpolation. When the correction data exceeds the maximum correction range, the correction data are replaced by the maximum in the correction range to utilize the capability of the distortion correction of the printer. Further, in the image data correction, after the image data are converted to data having a smaller number of gradation levels, the data are delayed according to the serial arrangement of the print units. Then, the delayed data are converted again for printing.

Abstract: In order to improve character edge reproducibility in reproducing a color document image, a boundary between a character and a background is detected in color image data. Further, if the detected edge exists at the side of a character, it is decided as a true edge, and the image data are subjected to edge emphasis. Then, when an image is reproduced, undesirable partial whitening in characters in the image can be prevented.

Abstract: In multi-level error diffusion in an image processor, a quantization error data table is accessed at an address of data from a feedback adder, to output the data at the address as quantization error data. By using the table, the error is detected at high speed with an access time for the table. The quantization error is added to an input data by an adder after error integration with weights. Thus, the feedback calculation in multi-level error diffusion is performed at high speed, while the circuit structure thereof is simplified.

Abstract: It is objected to provide an image processing apparatus achieving decrease of memory volume to be used, simplified print process, and enhancement of productivity. Firstly, a plurality of image data are recorded in memories provided for respective colors. Based on the image data or mode selection by a user, it is determined that whether a multi-color image or a monochrome image is to be outputted. Next, memories 302 of respective colors transmit image data of respective colors to a computing unit 304 in accordance with readout-timing signals from a timing selector 305. In case a multi-color image is to be outputted, the timing selector 305 transmits readout-timing signals of respective colors taking time difference length of which is predetermined for each color. In case a monochrome image is to be outputted, the timing selector 305 transmits readout-timing signals of respective color simultaneously.

Abstract: A color image is formed by a color printer by superposing images of a plurality of colors formed by a plurality of print units. A discrimination signal which represent character edge is received besides image data. The print positions of the print units are corrected according to image distortion detected by a sensor, and the image data are corrected according to corrected print position data. Further, the discrimination signal of character edge is corrected according to the detected image distortion. A color image is formed based on the corrected image data and the discrimination signal of character edge.

Abstract: In an image forming apparatus, a black edge of a document image is emphasized, and the black edge is detected by deciding an edge from the lightness data and by deciding a black color from the chroma data. The data of cyan, magenta and yellow of a pixel at a black edge are replaced with minima of data of cyan, magenta and yellow of pixels in a prescribed region around the pixel. In order to prevent erroneous decision of a black edge, if a number of isolated pixels is larger than a threshold level, a decision as a pixel at a black edge is invalidated. Automatic exposure can be performed on a color document for correcting a background of the document obtained in a prescan. The background level of the document is determined only on pixels decided to be black. When color balance is adjusted on one of the data of cyan, magenta, yellow and black, the density is kept constant.

Abstract: There is provided an image processing apparatus and an image processing method capable of conducting different manners of resolution conversion processing depending on scanning direction. An image processing apparatus 1 includes: a sub-scanning-directional first resolution converting section 4 for enhancing resolution of input image data in a sub-scanning direction; a sub-scanning-directional second resolution converting section 5; a main-scanning-directional first resolution converting section 14 for enhancing resolution of input image data in a main-scanning direction; and a main-scanning-directional second resolution converting section 15. The structure such as above enables the image processing apparatus 1 to conduct resolution conversion processing in sub-scanning direction and main-scanning direction independently, thereby to obtain a high-quality output image.

Abstract: The present invention relates to an image processor provided in apparatuses such as digital copiers and printers, and that distinguishes between a character edge region and a continuous tone region of an original image and switches the tone reproduction processing between the regions.

Abstract: In an image forming apparatus, a color registration error correction computing portion calculates optimal typical value of position change quantity for each image forming region. Based on these typical values, write timing at each of write portions is controlled by an image control portion. That is, color registration error correction is executed based on optimal correction quantity for each image forming region.

Abstract: An image processor receives color image data and converts them to image data of cyan, magenta, yellow and black necessary for image forming. The received color image data are subjected to color aberration correction, and various image data processing is performed on the image data after the color aberration correction in order to improve the precision of image processing on a color document image. The image data processing includes, for example, a specified color document is decided, automatic color selection and magnification change.

Abstract: A neighborhood select circuit of an image processing apparatus includes a comparator receiving a predetermined signal and output data from a contour enhancement unit for comparing the received inputs and providing a comparison result signal according to the comparison result, a neighborhood maximum value-minimum value circuit and neighborhood minimum value-maximum value circuit receiving data output from the contour enhancement unit, and a selector for receiving the output from the neighborhood maximum value-minimum value circuit, the neighborhood minimum value-maximum value circuit and the comparator. In the neighborhood maximum value-minimum value circuit, the target pixel data in the data output from the contour enhancement unit is substituted with the maximum data in the data of the surrounding pixels, and the target pixel data subjected to the process is substituted with the minimum value in the data of the surrounding pixels.