The image processing apparatus of the present invention includes: a first memory configured to store a first threshold value matrix used for halftone processing; a second memory configured to store a second threshold value matrix that is a threshold value matrix used for halftone processing and whose size is larger than the first threshold value matrix; and at least one circuit, the at least one circuit causing processing below: performing halftone processing for image data by using the first threshold value matrix or the second threshold value matrix selected based on attribute information on the image data, and the first threshold value matrix includes threshold values whose maximum number of bits is N and the second threshold value matrix includes threshold values whose maximum number of bits is M (M<N).

In the case of performing halftone processing using a threshold value matrix, the memory capacity for storing the threshold value matrix is reduced without reducing the image quality of an output image. An image processing apparatus that generates a halftone image by performing halftone processing using a threshold value matrix for each piece of image data of a plurality of color planes corresponding to color materials used for printing processing, and the number of bits of a threshold value in a first threshold value matrix for a color plane whose visibility is relatively low of the plurality of color planes is smaller than the number of bits of a threshold value in a second threshold value matrix for a color plane whose visibility is relatively high of the plurality of color planes.

A temporary dot pattern at a dot pattern determining target gradation is determined by adding or removing dots as much as the number of dots corresponding to a gradation difference to or from a dot pattern at a gradation at which a dot pattern is already determined, and a dot pattern at a dot pattern determining target gradation is determined by performing a replacement process of replacing dots including some of dots at a dot pattern determined gradation among the dots in the temporary dot pattern with non-dot arrangements. A halftone mask may be constituted by a group of dot patterns at each gradation, or the halftone mask may be constituted by setting a dot pattern for each gradation as a threshold value.

In an error diffusion process, a control device determines a dot value of a target pixel by using a gradation value of the target pixel, and an error value. The control device determines distribution error value by comparing a gradation dependent value with a first evaluated density value indicating a density of a first dot. The control device determines the distribution error value by using the first evaluated density value when the dot value of the target pixel indicates formation of the first dot and when the gradation dependent value is smaller than or equal to the first evaluated density value. The control device determines the distribution error value by using a modified evaluated density value greater than the first evaluated density value when the dot value indicates formation of the first dot and when the gradation dependent value is greater than the first evaluated density value.

A print system may include a print engine, a processing device and programming instructions to halftone an electronic document to be printed. The system may receive an input image representing the electronic document to be printed, use a first and second threshold array, which are flipped to each other, to halftone the input image to generate a first and second set of data, respectively, then combine the first and second set of data to generate a halftoned image. In combining the first and second set of data, each dot in the halftoned image may represent full saturation if the corresponding dot in at least one of the first and second set of data represents full saturation, or white if the corresponding dots in both the first and second set of data are white. The system may use the same halftoning method for a monochrome or color document.

An object of the present invention is to implement a bit pattern capable of specifying a plurality of colors while storing information on a shape. The present invention is an image processing apparatus that converts image data in a bitmap format into data including a bit pattern, the apparatus including: a creation unit configured to create, based on pixel values of pixels within an image area of a predetermined size within the image data, the bit pattern storing shape information on the image area, which specifies to which of a plurality of kinds of pixel each pixel within the image area corresponds, and color information on the image area, which specifies a number of colors in accordance with a kind of pixel specified by the shape information, and the number in accordance with a kind of pixel specified by the shape information is smaller than a total number of pixels within the image area.

An image processing apparatus including: a halftone processing unit configured to generate halftone image data represented by a halftone dot corresponding to a density value by performing halftone processing using a dither matrix for input image data; a phase change processing unit configured to correct a deviation of a laser beam scan line that is used in forming an image in accordance with the input image data on a printing medium by performing phase change processing to shift the phase of a pixel in the halftone image data in a sub scanning direction; and a pseudo high-resolution processing unit configured to convert the halftone image data after the phase change processing into halftone image data with a lower resolution by performing pseudo high-resolution processing, and in the dither matrix, threshold values are arranged so that the number of pixels in the sub scanning direction, which make up the halftone dot, is always even.

An image processing apparatus which performs image processing for print processing, including: a pseudo halftone processing unit configured to perform pseudo halftone processing by dithering with respect to an input image, and generate a halftone image constituted by plural dots, and a threshold matrix holding unit configured to hold a threshold matrix used for the pseudo halftone processing, wherein in the threshold matrix, thresholds are arranged such that the halftone image has a density region in which dots to be formed depending on a density of the input image are not rotational symmetric on a 90 basis, and orientations of the dots differ from each other in the density region.

In an error diffusion process, a control device determines a dot value of a target pixel by using a gradation value of the target pixel, and an error value. The control device determines distribution error value by comparing a gradation dependent value with a first evaluated density value indicating a density of a first dot. The control device determines the distribution error value by using the first evaluated density value when the dot value of the target pixel indicates formation of the first dot and when the gradation dependent value is smaller than or equal to the first evaluated density value. The control device determines the distribution error value by using a modified evaluated density value greater than the first evaluated density value when the dot value indicates formation of the first dot and when the gradation dependent value is greater than the first evaluated density value.

An image processing apparatus has a determination unit that determines a print operation to be performed and a generation unit that generates quantized data for printing a dot by comparing a threshold value and the multi-valued data. In a case of performing a first print operation, dot arrangement of the multiple types of inks printed on the print medium by the print unit on a basis of pieces of quantized data generated by the generation unit is higher in exclusiveness and dispersibility between or among dots of the multiple types of inks and lower in an overlap rate between or among the dots of the multiple types of inks than dot arrangement of the multiple types of inks printed on the print medium by the print unit on a basis of the pieces of quantized data generated by the generation unit in the case of performing the second print operation.