Color image-processing apparatus

Claim 2

A color copier comprising: a color line image sensor for optically scanning, line by line, a color document to provide fundamental color signals for each line of the document; matrix circuit means connected to receive the fundamental color signals for converting the fundamental color signals into a brightness signal and two color difference signals, said matrix circuit means having a set of matrix coefficients for obtaining the brightness signal and the two color difference signals; a color printer for reproducing the color document by use of a plurality of color inks; color conversion circuit means, coupled between said matrix circuit means and said color printer, including a read only memory table for storing ink amount control signals in a digitalized manner, which are adapted for controlling the amounts of the color inks used in said color printer, said read only memory table being accessed by the brightness signal and the color difference signals for outputting corresponding ink amount control signals; and nonlinear conversion circuit means connected between said image sensor and said matrix circuit means for converting the fundamental color signals from said image sensor in a nonlinear fashion such that a change in level of an input signal in a low-level range is increased to an extent greater that that in a high-level range, whereby the degrees of data quantization of the ink amount control signals are made substantially uniform in said read only memory table of said color conversion circuit means.

Claim 3

A copier according to claim 1, wherein said color line-image sensor is divided into a plurality of sensor sections along the line of the document; and said matrix circuit has a plurality of matrix conversion coefficient sets corresponding to said plurality of sensor sections of said color line-image sensor.

Claim 4

A copier according to claim 2, wherein said plurality of matrix conversion sets are determined such that a difference in color signals obtained from adjacent sensor sections can be minimized.

Claim 5

A copier according to claim 1, wherein said color line-image sensor comprises a charge-coupled device and a color filter array of fundamental colors.

Claim 6

A copier according to claim 4, wherein said color filter array comprises red, blue, and green filter elements arranged in a line.

Claim 7

A copier according to claim 1, wherein said nonlinear conversion circuit has a conversion characteristic given by Xo={(Xi+D).sup.n -D.sup.n }/{(1+D).sup.n -D.sup.n } where Xi and Xo are input and output signals of said nonlinear conversion circuit, respectively, and D and n are each a constant.

Claim 8

A copier according to claim 6, wherein D is about 0.05 and n is ranged from 1/2 to 1/3.

Claim 9

A copier accoridng to claim 2, wherein D=0.05 and n=1/3.

Claim 10

A copier according to claim 6, wherein D=0.01 and n=1/3.

Claim 11

A color copier comprising: a color line image sensor for optically scanning, line by line, a color document to provide fundamental color signals representative of red, green, and blue for each line of the document; matrix circuit means connected to receive the fundamental color signals for converting the fundamental color signals into a brightness signal I and two color difference signals C1 and C2, said matrix circuit means having a set of matrix coefficients for obtaining the brightness signal and the two color difference signals; a color printer for reproducing the color document by use of a plurality of color inks including magneta, yellow, and cyana; color conversion circuit means, coupled between said matrix circuit means and said color printer, including a read only memory table for storing ink amount control signals in a digitized manner, which are adapted for controlling the amounts of the color inks used in said color printer, said read only memory table being accessed by the brightness signal and the color difference signals for outputting corresponding ink amount control signals; and nonlinear conversion circuit means connected between said image sensor and said matrix circuit means for converting the fundamental color signals from said image sensor in a nonlinear fashion such that a change in level of an input signal in a low-level range is increased to an extent greater than that in a high-level range, whereby the coordinates representing each of yellow, magneta, cyan, red, green, and blue are distributed at substantially the same distance from the origin on a plane defined by color difference axes in said read only memory table of said color conversion circuit means.

Claim 12

A color copier comprising: a color line image sensor for optically scanning, line by line, a color document to provide fundamental color signals representative of red, green, and blue for each line of the document; matrix circuit means connected to receive the fundamental color signals for converting the fundamental color signals into a brightness signal I and two color difference signals C1 and C2, said matrix circuit means having a set of matrix coefficients for obtaining the brightness signal and the two color difference signals; a color printer for reproducing the color document by use of a plurality of color inks including magneta, yellow, and cyana; color conversion circuit means, coupled between said matrix circuit means and said color printer, including a read only memory table for storing ink amount control signals in a digitized manner, which are adapted for controlling the amounts of the color inks used in said color printer, said read only memory table being accessed by the brightness signal and the color difference signals for outputting corresponding ink amount control signals; and nonlinear conversion circuit means connected between said image sensor and said matrix circuit means for converting the fundamental color signals from said image sensor in a nonlinear fashion such that a change in level of an input signal in a low-level range is increased to an extent greater than that in a high-level range, whereby the coordinates representing each of yellow, magneta, cyan, red, green, and blue are distributed at substantially the same distance from the origin on a plane defined by color difference axes in said read only memory table of said color conversion circuit means.