Image processing apparatus, control method thereof, and non-transitory computer-readable storage medium

A method of controlling an image processing apparatus that generates image data for an image forming apparatus, the image forming apparatus having a recording head in which a plurality of recording elements are arranged in a first direction, and that forms an image on a recording medium by ejecting ink from the recording elements of the recording head toward the recording medium while the recording medium is fed relatively in a second direction that is perpendicular to the first direction, the method comprising:

• acquiring multi-valued input image data;
• executing a density unevenness correction process in accordance with properties of each of the recording elements;
• and
• converting the input image data, on which the density unevenness correction processing has been executed in the executing, into halftone image data indicating the presence/absence of a dot, by using a dither matrix,
• wherein the dither matrix is a dispersive dither matrix, and has characteristics in which when input image data having a uniform tone is converted into binary halftone image data, the same number of dots are present at each of locations in the first direction, in a predetermined range in the second direction, for a tone, among the tones which the input image data can take on, that is subject to the density unevenness correction process.

An image processing apparatus that generates a dither matrix used when converting multi-valued image data into a binary dot pattern for determining whether or not to eject ink from a plurality of recording elements in a recording head provided in an image forming apparatus,

• wherein when a direction in which the plurality of recording elements in the recording head provided in the image forming apparatus are arranged is defined as a first direction, and a direction perpendicular to the first direction and in which a recording medium is fed relative to the recording head is defined as a second direction, the dither matrix has a size of Sx rows corresponding to the second direction and Sy columns corresponding to the first direction, where Sx and Sy are natural numbers;
• and
• the image processing apparatus comprises:
• a filter for evaluating local density variation in a dot pattern d(g) of a predetermined tone g;
• a first calculation unit configured to calculate a density variation map n(g) by applying the filter;
• a second calculation unit configure to calculate a total dot number map s(g) in the second direction with respect to the dot pattern d(g) of the tone g;
• a generation unit configured to generate a dot pattern having tones continuing from the tone g, by adding or removing dots to the dot pattern on the basis of the density variation map and the total dot number map;
• and
• a determination unit configured to generate a dot pattern for all tones by repeatedly applying the first calculation unit, the second calculation unit and the generation unit using an initial dot pattern of a predetermined tone as a starting point, and to determine a value of the dither matrix on the basis of the dot pattern for all tones.

A method of controlling an image processing apparatus that generates a dither matrix used when converting multi-valued image data into a binary dot pattern for determining whether or not to eject ink from a plurality of recording elements in a recording head provided in an image forming apparatus,

• wherein when a direction in which the plurality of recording elements in the recording head provided in the image forming apparatus are arranged is defined as a first direction, and a direction perpendicular to the first direction and in which a recording medium is fed relative to the recording head is defined as a second direction, the dither matrix has a size of Sx rows corresponding to the second direction and Sy columns corresponding to the first direction, where Sx and Sy are natural numbers;
• and
• the method comprises:
• (a) calculating a density variation map n(g) by applying a filter for evaluating local density variation in a dot pattern d(g) of a predetermined tone g;
• (b) calculating a total dot number map s(g) in the second direction with respect to the dot pattern d(g) of the tone g;
• (c) generating a dot pattern having tones continuing from the tone g, by adding or removing dots to the dot pattern on the basis of the density variation map and the total dot number map;
• and
• (d) generating a dot pattern for all tones by repeatedly applying the calculating (a), the calculating (b) and the generating (c) using an initial dot pattern of a predetermined tone as a starting point, and determining a value of the dither matrix on the basis of the dot pattern for all tones.

A non-transitory computer-readable storage medium storing a computer program which causes, when read and executed by a computer, the computer to execute the steps of a method of controlling an image processing apparatus that generates image data for an image forming apparatus, the image forming apparatus having a recording head in which a plurality of recording elements are arranged in a first direction, and that forms an image on a recording medium by ejecting ink from the recording elements of the recording head toward the recording medium while the recording medium is fed relatively in a second direction that is perpendicular to the first direction, the method comprising:

• acquiring multi-valued input image data;
• executing a density unevenness correction process in accordance with properties of each of the recording elements;
• and
• converting the input image data, on which the density unevenness correction processing has been executed in the executing, into halftone image data indicating the presence/absence of a dot, by using a dither matrix,
• wherein the dither matrix is a dispersive dither matrix, and has characteristics in which when input image data having a uniform tone is converted into binary halftone image data, the same number of dots are present at each of locations in the first direction, in a predetermined range in the second direction, for a tone, among the tones which the input image data can take on, that is subject to the density unevenness correction process.

A non-transitory computer-readable storage medium storing a computer program which causes, when read and executed by a computer, the computer to execute the steps of a method of controlling an image processing apparatus that generates a dither matrix used when converting multi-valued image data into a binary dot pattern for determining whether or not to eject ink from a plurality of recording elements in a recording head provided in an image forming apparatus,

• wherein when a direction in which the plurality of recording elements in the recording head provided in the image forming apparatus are arranged is defined as a first direction, and a direction perpendicular to the first direction and in which a recording medium is fed relative to the recording head is defined as a second direction, the dither matrix has a size of Sx rows corresponding to the second direction and Sy columns corresponding to the first direction, where Sx and Sy are natural numbers;
• and
• the method comprises:
• (a) calculating a density variation map n(g) by applying a filter for evaluating local density variation in a dot pattern d(g) of a predetermined tone g;
• (b) calculating a total dot number map s(g) in the second direction with respect to the dot pattern d(g) of the tone g;
• (c) generating a dot pattern having tones continuing from the tone g, by adding or removing dots to the dot pattern on the basis of the density variation map and the total dot number map;
• and
• (d) generating a dot pattern for all tones by repeatedly applying the calculating (a), the calculating (b) and the generating (c) using an initial dot pattern of a predetermined tone as a starting point, and determining a value of the dither matrix on the basis of the dot pattern for all tones.