Abstract: A threshold generation device sets a ratio of a length along a main scanning direction to a length along a sub-direction based on a relation between image reproducibility in the main scanning direction and image reproducibility in the sub-direction of an image processing device for forming an image on a paper based on an image data obtained by the halftone processing. The device determines spatial frequency characteristics having a domain of an ellipse shape having set major axis and minor axis as peak values. The device sets a threshold value of each pixel of the threshold matrix in accordance with the determined spatial frequency characteristics.

Abstract: An image processing apparatus to perform a screen process on color image data using threshold matrices includes an address calculation section, threshold processor and shift section. The address calculation section calculates an address in the threshold matrix. The threshold processor acquires a threshold by the address, and performs an n-valued process (n?2) on a pixel value using the threshold. The shift section divides the image data into blocks in units of the threshold matrix, determines shift amounts for each block, and shifts the address. The threshold processor acquires a threshold by an address after the shift for at least one color, and performs the n-valued process using the threshold. The threshold matrix for a color for which the address is shifted has a screen ruling with a lower number of lines than the address is not shifted.

Abstract: An image processing apparatus includes a probability conversion unit, a processor, and a threshold conversion unit. The probability conversion unit receives an initial pattern and converts it into a probability distribution space. The processor performs weighting on a density distribution space indicating a density of pixels determined to be dotted using the probability distribution space, determines pixels to be dotted and an order of the dotting in the weighted density distribution space, updates the probability distribution space until the order for all pixels in the initial pattern is determined, and repeats the determination using the updated probability distribution space. The threshold conversion unit converts the order of dotting into thresholds to obtain a threshold matrix. The probability conversion unit uses a threshold matrix preliminarily created to form a halftone dot as the initial pattern.

Abstract: An image forming apparatus includes an image forming section which forms an image on a sheet, a reading section which reads the image formed on the sheet by the image forming section, and a control section. The control section allows the image forming section to form a reference image for evaluation of image quality, allows the reading section to read the reference image at a resolution lower than a resolution at which the reference image is formed, obtains read values of the reference image, the resolution of which has been made higher than the resolution of the reference image read by the reading section using the read reference image, and creates evaluation data based on the obtained read values.

Abstract: Provided is an image processor obtaining image data divided in packing units, comprising: a parallel processing unit performing an image conversion processing in parallel on the pixel data arranged in a sub scan direction in the packing unit, based on the obtained pixel data and the intermediate value for the pixel data, to calculate an output value after the conversion of the pixel data and an index value; an intermediate value calculating unit calculating an intermediate value based on the respective index values calculated by the parallel processing units regarding pixels within a predetermined relative position range; and a first retention unit for delaying the start of the image conversion processing to one pixel data for a delay period set to be equal to or longer than a period required for obtaining the one pixel data and calculating the intermediate value for the one pixel data.

Abstract: Disclosed is an image processing apparatus which uses a threshold matrix of a resolution higher than a resolution of an input image, the image processing apparatus including: a screen processing section which performs screen processing on an input image which is input; a matrix storage section which stores a threshold matrix of a resolution higher than a resolution of the input image; a threshold obtaining section which obtains a new threshold corresponding to each pixel of the input image based on a threshold of each cell composing the threshold matrix, wherein the screen processing section compares the pixel value of each pixel of the input image with the new threshold corresponding to each pixel of the input image obtained by the threshold obtaining section and generates a multivalue output image.

Abstract: Disclosed is an image forming apparatus including: an image forming section which forms an image on paper; a plurality of image reading sections each of which reads the image formed on the paper, and is connectable to the image forming apparatus; a storage section which stores connection information on a connection state between each of the image reading sections and the image forming apparatus; and a control section which selects a test image reading section from among the image reading sections based on the connection information, makes the selected test image reading section read a test image formed by the image forming section, and performs image quality adjustment based on the read test image.

Abstract: An image processing apparatus to perform a screen process on color image data using threshold matrices includes an address calculation section, threshold processor and shift section. The address calculation section calculates an address in the threshold matrix. The threshold processor acquires a threshold by the address, and performs an n-valued process (n?2) on a pixel value using the threshold. The shift section divides the image data into blocks in units of the threshold matrix, determines shift amounts for each block, and shifts the address. The threshold processor acquires a threshold by an address after the shift for at least one color, and performs the n-valued process using the threshold. The threshold matrix for a color for which the address is shifted has a screen ruling with a lower number of lines than the address is not shifted.

Abstract: An image processing apparatus including: a determining processing section which binarizes a pixel value of a target pixel using a threshold; a calculation section which calculates feedback values by multiplying binarized pixel values of adjacent processed pixels by a feedback coefficient; a addition section which adds the feedback values to the pixel value of the target pixel before binarization; a diffusion section which diffuses a difference between the binarized pixel value and the unadded pixel value as an error to adjacent unprocessed pixels; and a subtraction section which subtracts the error from the unadded pixel value of the target pixel, wherein when all pixel values of processed pixels are 0 and an output value of the target pixel is a maximum value, it is determined that the target pixel is an isolated point and an output value of an adjacent pixel is set to a forced output value excluding 0.

Abstract: An image processing apparatus includes a probability conversion unit, a processor, and a threshold conversion unit. The probability conversion unit receives an initial pattern and converts it into a probability distribution space. The processor performs weighting on a density distribution space indicating a density of pixels determined to be dotted using the probability distribution space, determines pixels to be dotted and an order of the dotting in the weighted density distribution space, updates the probability distribution space until the order for all pixels in the initial pattern is determined, and repeats the determination using the updated probability distribution space. The threshold conversion unit converts the order of dotting into thresholds to obtain a threshold matrix. The probability conversion unit uses a threshold matrix preliminarily created to form a halftone dot as the initial pattern.

Abstract: An image processing apparatus including an input unit which inputs a pixel value of a multi-level notice pixel, a first add unit which acids an error value to the input value, a second add unit which adds a green noise value to the input value, a threshold processing unit which outputs an binarized output values a green noise calculation unit which calculates the green noise value, a subtract unit which calculates an error value due to binarization, an error diffusion unit which diffuses the calculated error value to an untreated pixel which is not yet binarized and a correction processing unit which adds a positive first offset to the error value to perform a correction and outputs the corrected error value to the first add unit.

Abstract: A threshold generation device sets a ratio of a length along a main scanning direction to a length along a sub-direction based on a relation between image reproducibility in the main scanning direction and image reproducibility in the sub-direction of an image processing device for forming an image on a paper based on an image data obtained by the halftone processing. The device determines spatial frequency characteristics having a domain of an ellipse shape having set major axis and minor axis as peak values. The device sets a threshold value of each pixel of the threshold matrix in accordance with the determined spatial frequency characteristics.

Abstract: An image processing apparatus including an input unit which inputs a pixel value of a multi-level notice pixel, a first add unit which acids an error value to the input value, a second add unit which adds a green noise value to the input value, a threshold processing unit which outputs an binarized output values a green noise calculation unit which calculates the green noise value, a subtract unit which calculates an error value due to binarization, an error diffusion unit which diffuses the calculated error value to an untreated pixel which is not yet binarized and a correction processing unit which adds a positive first offset to the error value to perform a correction and outputs the corrected error value to the first add unit.

Abstract: Disclosed is an image forming apparatus including: an image forming section which forms an image on paper; a plurality of image reading sections each of which reads the image formed on the paper, and is connectable to the image forming apparatus; a storage section which stores connection information on a connection state between each of the image reading sections and the image forming apparatus; and a control section which selects a test image reading section from among the image reading sections based on the connection information, makes the selected test image reading section read a test image formed by the image forming section, and performs image quality adjustment based on the read test image.

Abstract: Provided is an image processor obtaining image data divided in packing units, comprising: a parallel processing unit performing an image conversion processing in parallel on the pixel data arranged in a sub scan direction in the packing unit, based on the obtained pixel data and the intermediate value for the pixel data, to calculate an output value after the conversion of the pixel data and an index value; an intermediate value calculating unit calculating an intermediate value based on the respective index values calculated by the parallel processing units regarding pixels within a predetermined relative position range; and a first retention unit for delaying the start of the image conversion processing to one pixel data for a delay period set to be equal to or longer than a period required for obtaining the one pixel data and calculating the intermediate value for the one pixel data.

Abstract: Disclosed is an image processing apparatus which uses a threshold matrix of a resolution higher than a resolution of an input image, the image processing apparatus including: a screen processing section which performs screen processing on an input image which is input; a matrix storage section which stores a threshold matrix of a resolution higher than a resolution of the input image; a threshold obtaining section which obtains a new threshold corresponding to each pixel of the input image based on a threshold of each cell composing the threshold matrix, wherein the screen processing section compares the pixel value of each pixel of the input image with the new threshold corresponding to each pixel of the input image obtained by the threshold obtaining section and generates a multivalue output image.

Abstract: Disclosed is an image reading apparatus which reads images in a front side and a back side of a document by passing the document through the image reading apparatus once including a first reading section to read the front side of the document, a second reading section to read the back side of the document and an image process section to calculate a first standard value for carrying out a first shading correction to the first reading section and a second standard value for carrying out a second shading correction to the second reading section, respectively, and to carry out the first shading correction to a first image data read by the first reading section based on the calculated first standard value and to carry out the second shading correction to a second image data read by the second reading section based on the calculated second standard value.

Abstract: An image processing apparatus including: a determining processing section which binarizes a pixel value of a target pixel using a threshold; a calculation section which calculates feedback values by multiplying binarized pixel values of adjacent processed pixels by a feedback coefficient; a addition section which adds the feedback values to the pixel value of the target pixel before binarization; a diffusion section which diffuses a difference between the binarized pixel value and the unadded pixel value as an error to adjacent unprocessed pixels; and a subtraction section which subtracts the error from the unadded pixel value of the target pixel, wherein when all pixel values of processed pixels are 0 and an output value of the target pixel is a maximum value, it is determined that the target pixel is an isolated point and an output value of an adjacent pixel is set to a forced output value excluding 0.

Abstract: An image forming apparatus forms a pattern image on a sheet by irradiating a photosensitive body with laser lights emitted from first to eighth laser light sources based on timing set in a displaying/setting section. As the pattern image, a combined pattern image in which a plurality of combined images are arranged continuously in the sub scanning direction, in each of which combined images two first line images are arranged apart from each other in the main scanning direction, and the second line image is arranged therebetween.

Abstract: Disclosed is an image processing apparatus to perform screen processing for image data, and to form an image based thereon, comprising a screen processing unit to perform the screen processing by using a subcell corresponding to a plurality of pixels, and in which a first and a second threshold values are determined according to each position of the pixels, wherein the screen processing unit obtains threshold values, to output either an invariable value Dmin, an invariable value DMax, or an interpolated value of the two invariable values, and wherein the subcell is determined so that the first threshold value of a given pixel is larger than the first threshold value of a prior pixel and is smaller than the second threshold value thereof, the threshold values of the prior pixel being determined so that a dot is formed in the prior pixel earlier than in the given pixel.