US 5,708,728 AGranted

Color image processing device with error-diffusion binarization function

AssigneeBrother Kogyo Kabushiki Kaisha

InventorMayumi Nomura

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Abstract

Input chromatic densities IC, IM, and IY are first converted into corrected chromatic densities I'C, I'M, and I'Y based on the input density IK. The input density IK is then added with the corresponding weighted error sum EK, so that a modified density IKmod is obtained. Similarly, the corrected chromatic densities I'C, I'M, and I'Y are added with the weighted error sums EC, EM, and EY, respectively, so that modified densities ICmod, IMmod, and IYmod are obtained. Then, the modified density IKmod is compared with the threshold T, and an output OK is determined. When the obtained output OK is zero, the ICmod, IMmod, and IYmod are compared with the threshold T, and output data OC, OM, and OY are obtained. On the other hand, when the obtained output OK is a dot-forming data, the output data OC, OM, and OY are forcibly set to a non-dot forming data.

Claims18

Dependent claims

A color image processing device for binarizing a color continuous tone image to produce color pseudo-continuous tone image data, the device comprising:

modification means for modifying input density data of each pixel for each of a plurality of color components with a corresponding sum of binarization errors which are distributed to the subject pixel from at least one preceding nearby pixel, the plurality of color components including a predetermined color component and at least one reference color component;
predetermined color output determination means for comparing the modified input density of the subject pixel for the predetermined color component with a predetermined threshold value, thereby determining binarized output data for the predetermined color component, the binarized output data being either one of a dot-forming data and an on-dot forming data, the dot-forming data indicating production of a dot of the predetermined color component on the subject pixel, the non-dot forming data indicating production of no dots of the predetermined color component on the subject pixel;
reference color output determination means for comparing, when the binarized output data for the predetermined color component is a non-dot forming data, the modified input density of the subject pixel for the reference color component with the predetermined threshold value, thereby determining binarized output data for the reference color component, the binarized output data being either one of a dot-forming data and a non-dot forming data, the dot-forming data indicating production of a dot of the reference color component on the subject pixel, the non-dot forming data indicating production of no dots of the reference color component on the subject pixel, the reference color output determination means determining binarized output data for the reference color component as the non-dot forming data when the binarized output data for the predetermined color component is a dot-forming data;
binarization error determining means for determining a binarization error for the predetermined color component as a difference between the modified input density data of the predetermined color component and the binarized output data for the predetermined color component and for determining a binarization error for the reference color component as a difference between the modified input density data of the reference color component and the binarized output data for the reference color component;
and
means for distributing the binarization errors of the predetermined color component and of the reference color component to at least one subsequent nearby pixel which has not yet been binarized.

3 more elements

A method of binarizing a color continuous tone image to produce color pseudo-continuous tone image data, the method comprising the steps of:

modifying input density data of one pixel for each of a plurality of color components with a corresponding sum of binarization errors which are distributed to the subject pixel during error-diffusion binarization processes previously performed for at least one preceding nearby pixel, the plurality of color components including a predetermined color component and at least one reference color component;
comparing the modified input density of the subject pixel for the predetermined color component with a predetermined threshold value, thereby determining binarized output data for the predetermined color component, the binarized output data being either one of a dot-forming data and non-dot forming data, the dot-forming data indicating production of a dot of the predetermined color component on the subject pixel, the non-dot forming data indicating production of no dots of the predetermined color component on the subject pixel;
comparing, when the binarized output data for the predetermined color component is a non-dot forming data, the modified input density of the subject pixel for the reference color component with the predetermined threshold value, thereby determining binarized output data for the reference color component, the binarized output data being either one of a dot-forming data and a non-dot forming data, the dot-forming data indicating production of a dot of the reference color component on the subject pixel, the non-dot forming data indicating production of no dots of the reference color component on the subject pixel;
determining binarized output data for the reference color component as the non-dot forming data when the binarized output data for the predetermined color component is a dot-forming data;
determining a binarization error for the predetermined color component as a difference between the modified input density data of the predetermined color component and the binarized output data for the predetermined color component and determining a binarization error for the reference color component as a difference between the modified input density data of the reference color component and the binarized output data for the reference color component;
and
distributing the binarization errors of the predetermined color component and of the reference color component to at least one subsequent nearby pixel which has not yet been binarized.

4 more elements

Dependencies are inferred from the claim text.