Image processing method, image processing apparatus, image forming apparatus, computer program product and computer memory product for carrying out image processing by transforming image data to image data having spatial frequency components
First Claim
1. An image processing method for carrying out image processing by transforming image data to image data having spatial frequency components and by modifying the coefficients of said spatial frequency components, comprising steps controlled by a processor of:
- judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same is equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component;
modifying the coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment;
adding specific values to the modified coefficients of the alternating current (AC) components of the image data;
inversely transforming the image data, to which said specific values are added, to image data having spatial coordinate components;
comparing gray levels of the inversely transformed image data with predetermined values; and
transforming said gray levels to quantized levels corresponding to the result of the comparison, whereinall the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out.
1 Assignment
0 Petitions
Accused Products
Abstract
Image processing is carried out by transforming image data to image data having spatial frequency components, by judging whether the absolute values of the coefficients of the predetermined frequency components of the transformed image data are equal to or more than a predetermined value, by modifying the coefficients of the AC components of the image data depending on the result of the judgment, by inversely transforming the image data having the modified coefficients to image data having spatial coordinate components, by comparing the gray levels of the inversely transformed image data with predetermined values, and by transforming the gray levels to quantized levels corresponding to the result of the comparison. By carrying out proper image processing corresponding to the characteristics of the image, the number of gray levels of the image can be decreased while the characteristic portions of the original image are maintained properly.
15 Citations
17 Claims
-
1. An image processing method for carrying out image processing by transforming image data to image data having spatial frequency components and by modifying the coefficients of said spatial frequency components, comprising steps controlled by a processor of:
-
judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same is equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component; modifying the coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment; adding specific values to the modified coefficients of the alternating current (AC) components of the image data; inversely transforming the image data, to which said specific values are added, to image data having spatial coordinate components; comparing gray levels of the inversely transformed image data with predetermined values; and transforming said gray levels to quantized levels corresponding to the result of the comparison, wherein all the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out. - View Dependent Claims (2, 3)
-
-
4. An image processing apparatus which has a frequency transform unit for transforming image data to image data having spatial frequency components, and carries out image processing by modifying the coefficients of said spatial frequency components, comprising:
-
a judging unit for judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same is equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component; a calculation unit for modifying the coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment made by said judging unit; an adding unit for adding specific values to the coefficients of the alternating current (AC) components of the image data modified by said calculation unit; an inverse transform unit for inversely transforming the image data, to which said specific values are added by said adding unit, to image data having spatial coordinate components; and a threshold processing unit for comparing gray levels of the image data inversely transformed by said inverse transform unit with predetermined values and for transforming said gray levels to quantized levels corresponding to the result of the comparison, wherein all the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11)
-
-
12. An image forming apparatus including an image processing apparatus which has a frequency transform unit for transforming image data to image data having spatial frequency components, and carries out image processing by modifying the coefficients of said spatial frequency components,
said image processing apparatus, comprising: -
a judging unit for judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same are equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component; a calculation unit for modifying the coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment made by said judging unit; an adding unit for adding specific values to the coefficients of the alternating current (AC) components of the image data modified by said calculation unit; an inverse transform unit for inversely transforming the image data, to which said specific values are added by said adding unit, to image data having spatial coordinate components; and a threshold processing unit for comparing gray levels of the image data inversely transformed by said inverse transform unit with predetermined values and for transforming said gray levels to quantized levels corresponding to the result of the comparison, wherein an image is formed on the basis of the image data image-processed by said image processing apparatus, and all the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out. - View Dependent Claims (13)
-
-
14. A computer program product for controlling a computer to carry out image processing by transforming image data to image data having spatial frequency components and by modifying the coefficients of said spatial frequency components, wherein the computer program product comprises:
-
a computer readable storage medium having computer readable program code means embodied in said medium, said computer readable program code means comprising computer instruction means for; judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same is equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component; modifying coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment; adding specific values to the modified coefficients of the alternating current (AC) components of the image data; inversely transforming the image data, to which said specific values are added, to image data having spatial coordinate components; comparing gray levels of the inversely transformed image data with predetermined values; and transforming said gray levels to quantized levels corresponding to the result of the comparison, wherein all the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out. - View Dependent Claims (15, 16)
-
-
17. A computer memory product readable by a computer containing a program for controlling a computer to carry out image processing by transforming image data to image data having spatial frequency components and by modifying the coefficients of said spatial frequency components, the program comprising steps of:
-
judging whether at least one of absolute values of the products obtained by multiplying the plural coefficients of the predetermined frequency components, corresponding to a predetermined direct current component, of the transformed image data by the coefficients of the direct current (DC) components of the same is equal to or more than a predetermined value, wherein a plurality of the absolute values correspond with each of the plural coefficients and the absolute values correspond with the direct current component; modifying coefficients of alternating current (AC) components of said image data by calculation depending on the result of the judgment; adding specific values to the modified coefficients of the alternating current (AC) components of the image data; inversely transforming the image data, to which said specific values are added, to image data having spatial coordinate components; comparing gray levels of the inversely transformed image data with predetermined values; and transforming said gray levels to quantized levels corresponding to the result of the comparison, wherein all the coefficients of the alternating current components corresponding to the predetermined direct current component are modified by calculation, once the judging has been carried out.
-
Specification