Abstract: An image processing apparatus executes an area dividing process on color image data that have been divided into blocks of a prescribed size, and for each block, selects a three-color mode when tone gradation is of higher priority and a four-color mode when resolution is of higher priority, as a color mode for an area averaging process. The image processing device executes a compression process in the selected color mode block by block, and outputs image data in a data format of 256 bit length, regardless of the color mode for compression.

Abstract: A method for compressing image data that are processed by a pseudo gradation process using a dither pattern is provided. The method includes the steps of dividing the image data into predetermined areas, determining whether or not a dot arrangement pattern of the image data in each area matches the dither pattern that was used in the pseudo gradation process, determining a representative value concerning density of the image data in the area if the dot arrangement pattern matches the dither pattern, and making compressed data by using the determined representative value.

Abstract: In image processing that expresses a small region with a predetermined number of representative colors, the image processing being carried out for each of small regions, with respect to the content of one small region, based on the extent of variation in that small region of each of the values of a plurality of color variables that express the color of each pixel, a target color variable is selected (#104), among values from the maximum value to the minimum value of the target color variable in that small region, a value of the target color variable for which the number of pixels is “0” is obtained as a reference value, and the pixels in that small region are grouped based on the reference value (#106), and a representative color of each group is obtained (#109).

Abstract: A printer divides an input image into a plurality of blocks and extracts a block image corresponding to each of the blocks. The colors of the block image are reduced to, for example, four colors. Index numbers are given to pixels of the color-reduced image, and the four colors are assigned. To a color palette in which color information of the four colors is described in correspondence with the index numbers, object information indicative of the kinds of images (for example, a character, a chart, and a photographic image) is added. Consequently, the handling performance of object information for use in an image processing such as a color conversion process is improved.

Abstract: There is provided an image processing apparatus employing an error diffusion method capable of preventing a pseudo contour attributable to a delayed dot. The image processing apparatus receives an error diffused from a neighboring pixel and corrects a value (an input value of 0 to 1) of a pixel to be processed before it reduces a tone. Then a subtracter calculates an error associated with the tone reduction, which is diffused to a neighboring pixel. Herein, only for an input value of no less than 0.5 an inversion portion multiplies by ?1 an error from a neighboring pixel and an error to a neighboring pixel. Thus a dot can be free of delay to prevent a pseudo contour.

Abstract: In a image processing apparatus executing an error diffusion process, normal error diffusion process is performed when an input pixel value is not “0”. When the input value is “0” (white pixel), “0” is automatically output, error memory of the pixel is reset, and calculation and distribution of the error are not performed. Accordingly, the speed of processing of the image processing apparatus can be improved. Further, by setting smaller the threshold value in error diffusion, the influence caused by resetting of the error memory and delay in generating a dot can be prevented.

Abstract: There is provided an image processing apparatus employing an error diffusion method capable of preventing a pseudo contour attributable to a delayed dot. The image processing apparatus receives an error diffused from a neighboring pixel and corrects a value (an input value of 0 to 1) of a pixel to be processed before it reduces a tone. Then a subtracter calculates an error associated with the tone reduction, which is diffused to a neighboring pixel. Herein, only for an input value of no less than 0.5 an inversion portion multiplies by ?1 an error from a neighboring pixel and an error to a neighboring pixel. Thus a dot can be free of delay to prevent a pseudo contour.

Abstract: An image data compression method includes the steps of dividing image data into predetermined regions, generating modeled data by extracting a feature of the image data for each of the regions, performing trial calculation of data quantity of compressed data that is generated by a thinning-out process in which data is thinned out from the modeled data based on a threshold value concerning the thinning-out process, determining a thinning-out threshold value that is a threshold value such that the data quantity becomes equal to or less than a predetermined target data quantity, and performing the thinning-out process based on the thinning-out threshold value so that compressed data is generated.

Abstract: A method for compressing image data on which a pseudo gradation process has been performed by using a dither pattern is provided. The method includes the steps of dividing the image data into predetermined blocks, calculating a typical value if an arrangement pattern of image data in each block can be reproduced by using a dither pattern that was used for the pseudo gradation process and the typical value, checking whether there is an arrangement pattern that matches the arrangement pattern of the image data in the block before then if it cannot be reproduced, calculating position data indicating a matching position if there is the arrangement pattern before then, obtaining the arrangement pattern of the image data in the block as block data if there is not the arrangement pattern before then, and using the calculated or obtained typical value, position data or block data for generating compressed data.

Abstract: A method for compressing image data having pixels arranged like a matrix in a line direction and a sub scan direction orthogonal to the line direction is provided. The method includes the steps of dividing the image data in the line direction and in the sub scan direction into blocks covering a plurality of lines, determining a representative value about density of pixels included in each of the blocks, determining additional information for each one line in each of the blocks or for each plurality of lines whose number is smaller than the number of lines of the block in each of the blocks, the additional information being information about the density of each of the pixels to be used instead of the representative value or to be added to the representative value, if there is, and creating compressed data by using the representative value and the additional information.

Abstract: An image processing apparatus providing a halftoning process such as error diffusion prevents an image contour distortion, as follows: data in an image to be processed is used to partially extend the image to be processed. Then error diffusion or the like is employed to provide a halftoning process. The extension is removed to obtain image data. A dot generation delay can be prevented that would otherwise be introduced such as when an extension-free image is halftoned.

Abstract: A method for compressing image data includes a first step for dividing image data into predetermined areas and determining a representative value about density of pixels in each area, a second step for determining density of pixels included in each area by using the representative value of the area and an interpolation rule, a third step for determining reproducibility of an image obtained, on the basis of the density of pixels determined in the second step, by using the image data and a dither pattern that is used for a pseudo gradation process performed on the image data, and a fourth step for encoding, on the basis of the representative value determined in the first step, for areas that are determined to have a good reproducibility in the third step.

Abstract: Thresholding is performed on an inputted pixel value using a corrected threshold value in a thresholding unit, and a binarized pixel value is output. The output is inverted, and from the inverted output the threshold value used for the thresholding is subtracted, and the resultant value is distributed to threshold values used for processing of the surrounding pixels. At this time, an input value is added to the value to be distributed (feedback value). Then, in the thresholding of the next pixel, the input value is subtracted from the distributed value, and the result is subtracted from an initial threshold value to derive a value which becomes a threshold value to be used in the binarization. When the input value changes, there is an effect of canceling out the change so that the edge can be weakened.

Abstract: From profiles of an input color space and an output color space, the specific color data on respective color spaces are obtained, and a color space compression parameter is set based on each specific color data obtained. In other words, the color space compression parameter for appropriately converting data within the input color space into data within the output color space is derived from each specific color data. The color space compression processing (color matching) is performed on an absolute color space using the derived color space compression parameter so that it becomes possible to perform at a higher speed an appropriate color matching that takes into account the characteristics of the input color space and the output color space.

Abstract: There is provided an image processing apparatus, operating as described below, employing an error distribution method to perform a halftone process intensively providing dots to achieve high resolution and a high level of tone representation simultaneously. The image processing apparatus, employing the error distribution method to convert an image represented by multiple values into an image provided in binary representation, employs a distribution weighting coefficient to distribute an error caused at a target pixel to a neighboring pixel. The distribution weighting coefficient simply decreases and ultimately attains zero as the distance from the target pixel increases, and the distance extending to attain zero is also set to vary with direction. Such a distribution weighting coefficient allows a halftone process providing dots intensively.

Abstract: A method for compressing image data that are processed by a pseudo gradation process using a dither pattern is provided. The method includes the steps of dividing the image data into predetermined areas, determining whether or not a dot arrangement pattern of the image data in each area matches the dither pattern that was used in the pseudo gradation process, determining a representative value concerning density of the image data in the area if the dot arrangement pattern matches the dither pattern, and making compressed data by using the determined representative value.

Abstract: A print system includes a computer and a printer. Image data having pseudo gradation with a dither pattern are printed by the printer. The computer divides the image data into predetermined areas, determines whether or not a dot arrangement pattern of image data in each of the areas matches a dither pattern that was used for generating the pseudo gradation, determines a representative value concerning a density of image data within the area if they match one another, and sends data related to the determined representative value to the printer. The printer obtains a representative value of each area from compressed data received from the computer and compares the obtained representative value with the dither pattern so as to reproduce a dot pattern.

Abstract: There is provided an image processing apparatus employing an error diffusion method capable of preventing a pseudo contour attributable to a delayed dot. The image processing apparatus receives an error diffused from a neighboring pixel and corrects a value (an input value of 0 to 1) of a pixel to be processed before it reduces a tone. Then a subtracter calculates an error associated with the tone reduction, which is diffused to a neighboring pixel. Herein, only for an input value of no less than 0.5 an inversion portion multiplies by ?1 an error from a neighboring pixel and an error to a neighboring pixel. Thus a dot can be free of delay to prevent a pseudo contour.

Abstract: The gray axis of an input apparatus is shifted so as to match the gray axis of an output apparatus. Each data on a plane of equal lightness located in the Gamut of the input apparatus is shifted in the same direction in accordance with the shift of the gray axis by an amount of shifting smaller in proportion to greater distance from the gray axis. Therefore, the image is not governed by the chromaticness in the shifting direction even if the gray axis is shifted. Points located outside the Gamut of the output apparatus is compressed-converted into points within the Gamut (surface) where color difference is minimized while maintaining the lightness. A desired image is reproduced without inversion in the lightness after Gamut compression between data.

Abstract: There is provided an image processing apparatus employing an error diffusion method capable of preventing a pseudo contour attributable to a delayed dot. The image processing apparatus receives an error diffused from a neighboring pixel and corrects a value (an input value of 0 to 1) of a pixel to be processed before it reduces a tone. Then a subtracter calculates an error associated with the tone reduction, which is diffused to a neighboring pixel. Herein, only for an input value of no less than 0.5 an inversion portion multiplies by ?1 an error from a neighboring pixel and an error to a neighboring pixel. Thus a dot can be free of delay to prevent a pseudo contour.