Apparatus and method for processing image

An image processing apparatus for converting M gradation image data into N gradation image data, wherein N is less than M, said image processing apparatus comprising:

• determining means for determining, based on the M gradation image data of a target region, whether the target region corresponds to an edge portion or to a non-edge portion;
• and
• processing means for generating, based on the determination by said determining means, the N gradation image data of the target region by using a first matrix in a case where the target region corresponds to the edge portion, and for generating the N gradation image data of the target region by using a part of a second matrix in a case where the target region corresponds to the non-edge portion,
• wherein said first matrix is a first dither matrix, and said second matrix is a second dither matrix,
• wherein said first dither matrix has a size corresponding to one region of the M gradation image data, and said second dither matrix has a size corresponding to a plurality of regions of the M gradation image data.

An image processing method for converting M gradation image data into N gradation image data, wherein N is less than M, said image processing method comprising the steps of:

• (a) determining, based on the M gradation image data of a target region, whether the target region corresponds to an edge portion or to a non-edge portion;
• and selectively
• (b-1) generating the N gradation image data of the target region by using a first matrix in a case where the target region corresponds to the edge portion in accordance with the determination in the step (a);
• and
• (b-2) selecting one of a plurality of parts of a second matrix and generating the N gradation image data of the target region by using the selected part of said second matrix in a case where the target region corresponds to the non-edge portion in accordance with the determination in the step (a),
• wherein said first matrix has a first size corresponding to one region of the M gradation image data, and said second matrix has a second size corresponding to a plurality of regions of the M gradation image data.

A storage containing a computer readable program with which a computer can execute a process including the steps of:

• (a) determining, based on M gradation image data of a target region, whether the target region corresponds to an edge portion or to a non-edge portion;
• and selectively
• (b-1) generating N gradation image data of the target region by using a first matrix in a case where the target region corresponds to the edge portion in accordance with the determination in the step (a);
• and
• (b-2) selecting one of a plurality of parts of a second matrix and generating the N gradation image data of the target region by using the selected part of said second matrix in a case where the target region corresponds to the non-edge portion in accordance with the determination in the step (a),
• wherein N is less than M,
• wherein said first matrix has a first size corresponding to one region of the M gradation image data, and said second matrix has a second size corresponding to a plurality of regions of the M gradation image data.

An image processing apparatus for converting M gradation image data into N gradation image data, wherein N is less than M, said image processing apparatus comprising:

• determining means for determining an attribute of the M gradation image data of a target region, and for generating composite data of the target region from the M gradation image data and the attribute of the target region;
• and
• processing means for generating, based on the composite data of the target region, the N gradation image data of the target region by using a selected one of a plurality of matrixes, wherein said processing means selects the selected one of the plurality of matrixes based on the attribute included in the composite data of the target region,
• wherein each of the plurality of matrixes is a dither matrix,
• wherein each of the plurality of dither matrixes has a size which is different from sizes of the other matrixes.

An image processing method for converting M gradation image data into N gradation image data, wherein N is less than M, said image processing method comprising the steps of:

• (a) determining an attribute of the M gradation image data of a target region;
• (b) generating composite data of the target region from the M gradation image data and the attribute of the target region;
• (c) selecting one of a plurality of matrixes based on the attribute included in the composite data of the target region;
• and
• (d) generating, based on the composite data of the target region, the N gradation image data of the target region by using the matrix selected in the step (c),
• wherein each of the plurality of dither matrixes has a size which is different from sizes of the other matrixes.

An image data converting method for converting image data of multi-valued data into image data of binary data equivalent to x times the image data of multi-valued data, comprising the steps of:

• determining whether a target pixel of the image data of multi-valued data corresponds to an edge portion or a non-edge portion;
• and
• converting image data of the target pixel into image data which is a part (1/n) of image data of a matrix having n*x pieces of binary data for reproducing N levels of gradation in response to a density of image data of the target pixel in a case where the target pixel corresponds to the non-edge portion, and converting image data of the target pixel into image data of a matrix having x pieces of binary data for reproducing x levels of gradation in response to a density of image data of the target pixel in a case where the target pixel corresponds to the edge portion;
• wherein N denotes an integer, x and n each denotes an integer of not less than 2, and the values of N, x, and n satisfy the following formula:
• N≦n*x.

An image data converting apparatus for converting image data of multi-valued data into image data of binary data equivalent to x times the image data of multi-valued data, comprising:

• a determining part for determining whether a target pixel of the image data of multi-valued data corresponds to an edge portion or a non-edge portion;
• and
• an area gradation processing part for converting image data of the target pixel into image data which is a part (1/n) of image data of a matrix having n*x pieces of binary data for reproducing N levels of gradation in response to a density of image data of the target pixel in a case where it is determined by said determining part that the target pixel corresponds to the non-edge portion, and for converting image data of the target pixel into image data of a matrix having x pieces of binary data for reproducing x levels of gradation in response to a density of image data of the target pixel in a case where it is determined by said determining part that the target pixel corresponds to the edge portion;
• wherein N denotes an integer, x and n each denotes an integer of not less than 2, and the values of N, x, and n satisfy the following formula:
• N≦n*x.

A computer program product for converting image data of multi-valued data into image data of binary data equivalent to x times the image data of multi-valued data, said computer program product causing a computer to execute a process including the steps of:

• determining whether a target pixel of the image data of multi-valued data corresponds to an edge portion or a non-edge portion;
• and
• converting image data of the target pixel into image data which is a part (1/n) of image data of a matrix having n*x pieces of binary data for reproducing N levels of gradation in response to a density of image data of the target pixel in a case where the target pixel corresponds to the non-edge portion, and converting image data of the target pixel into image data of a matrix having x pieces of binary data for reproducing x levels of gradation in response to a density of image data of the target pixel in a case where the target pixel corresponds to the edge portion;
• wherein N denotes an integer, x and n each denotes an integer of not less than 2, and the values of N, x, and n satisfy the following formula:
• N≦n*x.