Image processing method, image processing apparatus, image forming apparatus, and recording medium

An image processing method in which a dither processing using a dither matrix is performed based on a result of deter nation of a segmentation class to which a pixel to be processed belongs, the method comprising the steps of:

• providing a computer having an image input apparatus, a storage section, a segmentation process section and an image output apparatus;
• providing to the storage section an image comprising a plurality of pixels;
• in which a dither processing using a dither matrix is performed based on a result of
• determination of segmenting the pixels into one or more a segmentation classes class to which a each pixel to be processed belongs;
• selecting any of a plurality of dither matrices comprising a combination of different numbers of dither matrices of a same configuration and a same size according to the result of determination of the segmentation class;
• and
• performing a different dither processing according to the result of determination of the segmentation class on part of the dither matrix of the same configuration and the same size included in the selected dither matrix,
• wherein, to perform the dither processing, any of a plurality of pairs of threshold values is selected according to the result of determination of the segmentation class, and the selected pair of threshold values are compared with a value of the pixel to be processed, which are set so that in correspondence with each position of the dither matrix of the same configuration and the same size, a different dither processing is performed according to the result of determination of the segmentation class on part of the dither matrix and a same dither processing is performed irrespective of the result of determination of the segmentation class on a remainder of the dither matrix.

An image processing apparatus that performs a dither processing using a dither matrix based on a result of determination of a segmentation class to which a pixel to be processed belongs, the apparatus comprising:

• a storage section that stores a plurality of pairs of threshold values that are set so that in correspondence with each position of a dither matrix of a same configuration and a same size;
• a segmentation section for determining a segmentation class on a part of the dither matrix;
• and
• a selection section that selects any of the pairs of threshold values stored in the storage section according to the result of determination of the segmentation class,
• wherein to perform the dither processing, the pair of threshold values selected by the selection section are compared with a value of the pixel to be processed, and
• wherein a dither processing is performed according to the result of determination of the segmentation class on part of the dither matrix and a same dither processing is performed irrespective of the result of determination of the segmentation class on a remainder of the dither matrix irrespective of a determination of the segmentation class on the remainder of the dither matrix.

An image processing apparatus that performs a dither processing using a dither matrix based on a result of determination of a segmentation class to which a pixel to be processed belongs, the apparatus comprising:

• a storage section that stores a plurality of pieces of data representative of relation between a pixel value before a dither processing and a pixel value after the dither processing;
• a segmentation section for determining a segmentation class on a part of the dither matrix;
• and
• a selection section that selects any of the pieces of data representative of the relation stored in the storage section according to the result of determination of the segmentation class,
• wherein to perform the dither processing, a value of the pixel to be processed is converted based on the piece of data representative of the relation selected by the selection section, and
• wherein a dither processing is performed according to the result of determination of the segmentation class on part of the dither matrix of a same configuration and a same size and a same dither processing is performed irrespective of the result of determination of the segmentation class on a remainder of the dither matrix irrespective of a determination of the segmentation class on the remainder of the dither matrix.