Color printer characterization using optimization theory and neural networks

Claim 3

The method of claim 1 wherein said neurons operate to implement a non-linear hyperbolic tangent activation function.

Claim 4

The method of claim 1 wherein said device-independent color signals comprise LAB signals and wherein said device-dependent color signals comprise CMYK signals.

Claim 5

The method of claim 1 wherein said plurality of output prints representative of the gamut of the printer are selected in accordance with an ANSII basic data set in xy chromaticity coordinates.

Claim 6

The method of claim 4 wherein said device-independent color signals comprise LAB signals and wherein said device-dependent color signals comprise CMYK signals.

Claim 9

The method of claim 6 wherein said plurality of output prints comprise in the range of from about 101 to about 182 output prints, and wherein said neural network comprises in the range of from about 5 to about 7 neurons.

Claim 10

The method of claim 7 wherein said neurons operate to implement a non-linear hyperbolic tangent activation function.

Claim 11

The method of claim 6 wherein said color space image signals are printer independent, and wherein the color gamut of said color printer defines printer dependent signals.

Claim 12

The method of claim 6 wherein said neural network operates to implement a non-linear hyperbolic tangent activation function.

Claim 15

The method of claim 11 wherein said step of using said color prints to train said neural network includes the step of using an optimization routine to constrain said corresponding CMYK values in accordance with preselected criteria relationship between the C, M, Y and K colors.

Claim 16

The method of claim 11 further including, the steps of: providing LAB input signals that define a color image to be printed by the CMYK printer; using said LAB signals as an input to said lookup table; and providing CMYK signals from said lookup table to the CMYK printer corresponding to said LAB signals, such that output prints are produced bv the CMYK printer as defined by said RGB input signals.

Claim 17

Apparatus for producing a profile lookup table for use by a CMYK color printer in producing color prints, the profile lookup table comprising a plurality of table entries wherein each entry comprises a LAB value and a corresponding CMYK value in accordance with a print gamut of the CMYK color printer, the apparatus comprising: a neural network defining the print gamut of the CMYK color printer; said neural network having an input for receiving a test CMYK value; said neural network having an output for generating a LAB value that corresponds to said print gamut and to said test CMYK value; an error determining network; said error determining network having a first input connected to receive a series of LAB values wherein each of said received LAB values corresponds to a table entry of the profile lookup table; said error determining network having a second input connected to said output of said neural network to receive test LAB values; said error determining network having an error output that is responsive to a difference in the LAB values received by said first and second inputs; an error testing network establishing a LAB error criteria as a function of C, M, Y and K variables; said error testing network having an input connected to said error output of said error determining network; said error testing network having a NO output indicative of failure of said error output of said error determining network to meet said LAB error criteria; said error testing network having a YES output indicative of said error output of said error determining network meeting said LAB error criteria; and said YES output providing a CMYK value table entry to the profile lookup table that corresponds to a LAB value then connected to said first input of said error determining network.

Claim 18

Apparatus for producing a profile lookup table for use by a CMYK color printer in producing color prints, the profile lookup table comprising a plurality of table entries wherein each entry comprises a LAB value and a corresponding CMYK value in accordance with a print gamut of the CMYK color printer, the apparatus comprising: a neural network defining the print gamut of the CMYK color printer; said neural network having an input for receiving a test CMYK value; said neural network having an output for generating a LAB value that corresponds to said print gamut and to said test CMYK value; an error determining network; said error determining network having a first input connected to receive a series of LAB values wherein each of said received LAB values corresponds to a table entry of the profile lookup table; said error determining network having a second input connected to said output of said neural network to receive test LAB values; said error determining network having an error output that is responsive to a difference in the LAB values received by said first and second inputs; an error testing network establishing a LAB error criteria as a function of C, M, Y and K variables; said error testing network having an input connected to said error output of said error determining network; said error testing network having a NO output indicative of failure of said error output of said error determining network to meet said LAB error criteria; said error testing network having a YES output indicative of said error output of said error determining network meeting said LAB error criteria; and said YES output providing a CMYK value table entry to the profile lookup table that corresponds to a LAB value then connected to said first input of said error determining network.

Claim 19

The apparatus of claim 14 including: an optimization network connected intermediate to said NO output of said error testing network and said input of said neural network; said optimization network operating to minimize said error output of said error determining network that is responsive to a difference in the LAB values that are received by said first and second inputs of said error determining network.

Claim 20

The apparatus claim 15 wherein said neural network includes from 5 to 7 neurons.

Claim 21

The apparatus of claim 16 wherein said optimization network operates to apply a preselected constraint on said CMYK value table entries to the profile lookup table.

Claim 22

The apparatus of claim 17 wherein said preselected constraint is that the total quantity of printing ink that is represented by each CMYK value table entry shall not exceed a preselected quantity.

Claim 23

Apparatus for producing a profile lookup table for use by a color printer in producing color prints, the profile lookup table comprising a plurality of table entries wherein each entry comprises a printer independent color value and a corresponding printer dependent color value in accordance with a print gamut of the color printer, the apparatus comprising: a neural network defining the print gamut of the color printer; said neural network having an input for receiving a test printer dependent color value; said neural network having an output for generating a printer independent color value that corresponds to said print gamut and to said test printer dependent color value; an error determining network; said error determining network having a first input connected to receive a series of printer independent color values wherein each of said received printer independent color values corresponds to a table entry of the profile lookup table; said error determining network having a second input connected to said output of said neural network to receive test printer independent color values therefrom; said error determining network having an error output that is responsive to a difference in printer independent color values received by said first and second inputs; an error testing network establishing a color value error criteria; said error testing network having an input connected to said error output of said error determining network; said error testing network having a NO output indicative of failure of said error output of said error determining network to meet said color value error criteria; said error testing network having a YES output indicative of said error output of said error determining network meeting said color value error criteria; and said YES output providing a printer dependent color value table entry to the profile lookup table that corresponds to a printer independent color value then connected to said first input of said error determining network.

Claim 24

Apparatus for producing a profile lookup table for use by a color printer in producing color prints, the profile lookup table comprising a plurality of table entries wherein each entry comprises a printer independent color value and a corresponding printer dependent color value in accordance with a print gamut of the color printer, the apparatus comprising: a neural network defining the print gamut of the color printer; said neural network having an input for receiving a test printer dependent color value; said neural network having an output for generating a printer independent color value that corresponds to said print gamut and to said test printer dependent color value; an error determining network; said error determining network having a first input connected to receive a series of printer independent color values wherein each of said received printer independent color values corresponds to a table entry of the profile lookup table; said error determining network having a second input connected to said output of said neural network to receive test printer independent color values therefrom; said error determining network having an error output that is responsive to a difference in printer independent color values received by said first and second inputs; an error testing network establishing a color value error criteria; said error testing network having an input connected to said error output of said error determining network; said error testing network having a NO output indicative of failure of said error output of said error determining network to meet said color value error criteria; said error testing network having a YES output indicative of said error output of said error determining network meeting said color value error criteria; and said YES output providing a printer dependent color value table entry to the profile lookup table that corresponds to a printer independent color value then connected to said first input of said error determining network.

Claim 25

The apparatus of claim 19 including: an optimization network connected intermediate said NO output of said error testing network and said input of said neural network; said optimization network operating to minimize said error output of said error determining network that is responsive to a difference in the printer independent color values that are received by said first and second inputs of said error determining network.

Claim 26

The apparatus claim 20 wherein said neural network includes from 5 to 7 neurons.

Claim 27

The apparatus of claim 21 wherein said optimization network operates to apply a preselected ink constraint on said printer dependent color value table entries.

Claim 28

The apparatus of claim 22 wherein said preselected constraint is that the total quantity of printing ink/specified by each printer dependent color value table entry shall not exceed a preselected quantity of ink.

Claim 29

The apparatus of claim 19 wherein said printer dependent color value table entrvy is a CYMK table entry, and wherein said preselected constraint relates to the quantity of K within each CMYK table entry.

Claim 30

Apparatus for converting printer independent color signals to printer dependent color signals, comprising: an input for receiving a printer independent color signal that defines a color pixel image to be printed by a color printer; a color gamut conversion network having an input for receiving a test printer dependent color signal, and having an output for providing a test printer independent color signal in accordance with a color gamut of the color printer and in accordance with said received test printer dependent color signal; an error determining junction having a first input connected to said input receiving said printer independent color signal defining a color pixel image to be printed by the color printer, having a second input connected to said output of said color gamut conversion network for receiving said test printer independent color signal, and having an output responsive to a difference between said printer independent color signal defining a color pixel image to be printed by the color printer and said test printer independent color signal; a decision network constructed and arranged to implement a function f=C 1 (error signal)+C 2 (a parameter of a printed color pixel), wherein said terms “C1” and “C2” are constants, wherein said term “error signal” is a function of an acceptable color error of a printed color pixel corresponding to said printer independent color signal, and wherein said term “a parameter of a printed color pixel” relates to a factor, such as the ink cost of a printed color pixel corresponding to said input printer independent signal; said decision network having an input connected to said output of said error determining junction, having a YES output responding to said function being satisfied, and having a NO output responding to said function not being satisfied; a generating network for generating a test printer dependent color signal; said generating network having an input connected to said NO output of said decision network, and said generating network operating to generate said test printer dependent signal on an output of said generating network in response to said function not being satisfied; and circuit means connecting said output of said generating network to said input of said color gamut conversion network.

Claim 31

Apparatus for converting printer independent color signals to printer dependent color signals, comprising: an input for receiving a printer independent color signal that defines a color pixel image to be printed by a color printer; a color gamut conversion network having an input for receiving a test printer dependent color signal, and having an output for providing a test printer independent color signal in accordance with a color gamut of the color printer and in accordance with said received test printer dependent color signal; an error determining junction having a first input connected to said input receiving said printer independent color signal defining a color pixel image to be printed by the color printer, having a second input connected to said output of said color gamut conversion network for receiving said test printer independent color signal, and having an output responsive to a difference between said printer independent color signal defining a color pixel image to be printed by the color printer and said test printer independent color signal; a decision network constructed and arranged to implement a function f=C 1 (error signal)+C 2 (a parameter of a printed color pixel), wherein said terms “C1” and “C2” are constants, wherein said term “error signal” is a function of an acceptable color error of a printed color pixel corresponding to said printer independent color signal, and wherein said term “a parameter of a printed color pixel” relates to a factor, such as the ink cost of a printed color pixel corresponding to said input printer independent signal; said decision network having an input connected to said output of said error determining junction, having a YES output responding to said function being satisfied, and having a NO output responding to said function not being satisfied; a generating network for generating a test printer dependent color signal; said generating network having an input connected to said NO output of said decision network, and said generating network operating to generate said test printer dependent signal on an output of said generating network in response to said function not being satisfied; and circuit means connecting said output of said generating network to said input of said color gamut conversion network.

Claim 32

The apparatus of claim 25 wherein said color gamut conversion network comprises a neural network that is trained in accordance with said color gamut of the color printer.

Claim 33

The apparatus of claim 25 including: means responsive to said YES output of said decision network operating to provide said test printer dependent color signal to control the printer as said function of said input printer independent color signal.

Claim 34

The apparatus of claim 27 wherein said color gamut conversion network comprises a neural network that is trained in accordance with said color gamut of the color printer.

Claim 35

The apparatus of claim 25 wherein so long as said NO output of said decision network continues to persist, said generating network operates to generate a string of individually different test printer dependent signals until such time as a test printer dependent signal is generated that results in said function being satisfied.

Claim 36

The apparatus of claim 29 wherein a serial string of said input printer independent color signals are applied to said first input of said error determining junction, and including means responsive to a corresponding string of YES outputs from said decision network operable to build a printer profile lookup table having a string of entries, each individual entry being in accordance with an individual input printer independent color signal and a corresponding individual test printer dependent signals that resulted in said function being satisfied.

Claim 37

The apparatus of claim 30 wherein said color gamut conversion network comprises a neural network that is trained in accordance with said color gamut of the color printer.

Claim 38

The apparatus of claim 25 wherein said printer independent color signals are LAB signals, wherein said printer dependent color signals are CMYK signals, and wherein the color printer is a CMYK printer.

Claim 39

The apparatus of claim 32 wherein said YES output of said decision network is operable to apply a test CMYK signal that resulted in said YES output being produced to control said CMYK printer.

Claim 40

The apparatus of claim 33 wherein said color gamut conversion network comprises a neural network that is trained in accordance with said color gamut of the CMYK printer.

Claim 41

The apparatus of claim 32 wherein said YES output of said decision network is operable to apply an entry to a profile lookup table of said CMYK printer, said entry comprising a test CMYK signal that resulted in said YES output and said input LAB signal.

Claim 42

The apparatus of claim 35 wherein said color gamut conversion network comprises a neural network that is trained in accordance with said color gamut of the CMYK printer.

Claim 45

The method of claim 37 wherein said output color signal is operable to produce a printed pixel.

Claim 46

The method of claim 37 wherein said output color signal is applied as an entry to a color printer profile lookup table.

Claim 47

The method of claim 37 wherein said output color signal defines a color pixel to be printed by a color printer, and wherein said decision means implements the function; acceptable error=C 1 (actual error)+C 2 (cost of said color pixel), wherein said terms “C1” and “C2” are constants, wherein said term “actual error” is a function of an acceptable visual color error of said color pixel, and wherein said term “cost of said color pixel” relates to the ink cost of said color pixel.

Claim 48

The method of claim 40 wherein said color gamut conversion means comprises a neural network that is trained in accordance with a plurality of color prints that define said color gamut.

Claim 49

The method of claim 40 wherein said input color signal is a LAB signal, wherein said test color signal is a LAB signal, wherein said output color signal is a CMYK signal, and wherein said color printer is a CMYK printer.

Claim 50

The method of claim 42 wherein said color gamut conversion means comprises a neural network that is trained in accordance with a plurality of CMYK color prints that define said color gamut.

Claim 51

The method of claim 37 including the steps of: generating a string of input color signals and then, by operation of the method of claim 37 , generating a corresponding string of output color signals for which acceptable errors have been determined; and generating a profile lookup table for said color printer in accordance with said string of input color signals and said corresponding string of output color signals.

Claim 52

The method of claim 44 wherein said input color signals are LAB signals, wherein said test color signals are LAB signals, wherein said output color signals are CMYK signals, wherein said profile lookup table comprises a string of table entries, each table entry of which relates an individual LAB signal to a corresponding individual CMYK signal, and wherein said color printer is a CMYK printer.

Claim 53

The method of claim 45 wherein said color gamut conversion means comprises a neural network that is trained in accordance with a plurality of CMYK color prints that define said color gamut.

Claim 54

Apparatus for constructing a profile lookup table for use by a given CMYK printer in printing a CMYK color print in response to a plurality of printer independent color signals that define the CMYK color print, the profile lookup table containing a plurality of individual entries, each entry containing a printer independent signal and a corresponding CMYK signal in accordance with a gamut of the given CMYK printer, the profile lookup table for use in converting printer independent signals to CMYK signals in accordance with the gamut of the given CMYK printer, said apparatus comprising: a neural network having an input and an output; said neural network being responsive to a CMYK signal at said input and operating to provide a printer independent signal at said output in accordance with the gamut of the given CMYK printer; apparatus input means for receiving a plurality of input printer independent signals, each individual one of said input printer independent signals corresponding to an individual entry in the profile lookup table; error measuring means having a first input connected to receive an individual one of said plurality of input printer independent signals, having a second input connected to said output of said neural network, and having a difference error output that is responsive to a difference between signals applied to said first and second inputs; error criteria means having an input connected to said difference error output of said error measuring means, said error criteria means operating to set CMYK optimization criteria to be met by all CMYK entries to the profile lookup table; said error criteria means providing a NO output so long as said difference between signals applied to said first and second inputs of said error measuring means does not satisfy said CMYK optimization criteria; said error criteria means providing a YES output when said difference between signals applied to said first and second inputs of said error measuring means satisfies said CMYK optimization criteria; first means responsive to said NO output operating to sequentially apply a different CMYK signal to said input of said neural network until such time as a given CMYK signal applied to said input of said neural network operates to provide said YES output from said error criteria means; and second means responsive to said YES output for producing an entry in the profile lookup table that comprises said individual one of said input printer independent signal and said given CMYK signal.

Claim 55

Apparatus for constructing a profile lookup table for use by a given CMYK printer in printing a CMYK color print in response to a plurality of printer independent color signals that define the CMYK color print, the profile lookup table containing a plurality of individual entries, each entry containing a printer independent signal and a corresponding CMYK signal in accordance with a gamut of the given CMYK printer, the profile lookup table for use in converting printer independent signals to CMYK signals in accordance with the gamut of the given CMYK printer, said apparatus comprising: a neural network having an input and an output; said neural network being responsive to a CMYK signal at said input and operating to provide a printer independent signal at said output in accordance with the gamut of the given CMYK printer; apparatus input means for receiving a plurality of input printer independent signals, each individual one of said input printer independent signals corresponding to an individual entry in the profile lookup table; error measuring means having a first input connected to receive an individual one of said plurality of input printer independent signals, having a second input connected to said output of said neural network, and having a difference error output that is responsive to a difference between signals applied to said first and second inputs; error criteria means having an input connected to said difference error output of said error measuring means, said error criteria means operating to set CMYK optimization criteria to be met by all CMYK entries to the profile lookup table; said error criteria means providing a NO output so long as said difference between signals applied to said first and second inputs of said error measuring means does not satisfy said CMYK optimization criteria; said error criteria means providing a YES output when said difference between signals applied to said first and second inputs of said error measuring means satisfies said CMYK optimization criteria; first means responsive to said NO output operating to sequentially apply a different CMYK signal to said input of said neural network until such time as a given CMYK signal applied to said input of said neural network operates to provide said YES output from said error criteria means; and second means responsive to said YES output for producing an entry in the profile lookup table that comprises said individual one of said input printer independent signal and said given CMYK signal.

Claim 56

The apparatus of claim 47 wherein said CMYK optimization criteria includes a total ink quantity and/or a total black ink quantity represented by said given CMYK signal.

Claim 57

The apparatus of claim 48 wherein said printer independent signals are LAB signals.

Claim 58

Apparatus for controlling a given CMYK printer to print a CMYK color print in response to a plurality of printer independent color signals that define a plurality of color pixels within the CMYK color print, said CMYK printer having a CMYK color gamut, said apparatus comprising: gamut-defining means having an input and an output; said gamut-defining means being responsive to a CMYK signal at said input and operating to provide a printer independent signal at said output in accordance with the CMYK gamut of the given CMYK printer; apparatus input means for receiving the plurality of input printer independent signals that define a plurality of pixels within the CMYK color print, each individual one of said input printer independent signals corresponding to an individual pixel of the pixels within the CMYK color print; error measuring means having a first input connected to receive each individual one of said plurality of input printer independent signals, having a second input connected to said output of said gamut-defining means, and having a difference error output that is responsive to a difference between signals applied to said first and second inputs; error criteria means having an input connected to said difference error output of said error measuring means, said error criteria means operating to set CMYK optimization criteria to be met by all color pixels of the CMYK color print; said error criteria means providing a NO output so long as said difference between signals applied to said first and second inputs of said error measuring means does not satisfy said CMYK optimization criteria; said error criteria means providing a YES output when said difference between signals applied to said first and second inputs of said error measuring means satisfies said CMYK optimization criteria; first means responsive to said NO output operating to sequentially apply a different CMYK signal to said input of said gamut-defining means, until such time as a given CMYK signal applied to said input of said gamut-defining means operates to provide said YES output from said error criteria means; and second means responsive to said YES output for providing said given CMYK signal to control the given printer.

Claim 59

Apparatus for controlling a given CMYK printer to print a CMYK color print in response to a plurality of printer independent color signals that define a plurality of color pixels within the CMYK color print, said CMYK printer having a CMYK color gamut, said apparatus comprising: gamut-defining means having an input and an output; said gamut-defining means being responsive to a CMYK signal at said input and operating to provide a printer independent signal at said output in accordance with the CMYK gamut of the given CMYK printer; apparatus input means for receiving the plurality of input printer independent signals that define a plurality of pixels within the CMYK color print, each individual one of said input printer independent signals corresponding to an individual pixel of the pixels within the CMYK color print; error measuring means having a first input connected to receive each individual one of said plurality of input printer independent signals, having a second input connected to said output of said gamut-defining means, and having a difference error output that is responsive to a difference between signals applied to said first and second inputs; error criteria means having an input connected to said difference error output of said error measuring means, said error criteria means operating to set CMYK optimization criteria to be met by all color pixels of the CMYK color print; said error criteria means providing a NO output so long as said difference between signals applied to said first and second inputs of said error measuring means does not satisfy said CMYK optimization criteria; said error criteria means providing a YES output when said difference between signals applied to said first and second inputs of said error measuring means satisfies said CMYK optimization criteria; first means responsive to said NO output operating to sequentially apply a different CMYK signal to said input of said gamut-defining means, until such time as a given CMYK signal applied to said input of said gamut-defining means operates to provide said YES output from said error criteria means; and second means responsive to said YES output for providing said given CMYK signal to control the given printer.

Claim 60

The apparatus of claim 50 wherein said CMYK optimization criteria includes a total ink quantity and/or a total black ink quantity represented by said given CMYK signal.

Claim 61

The apparatus of claim 51 wherein said printer independent signals are LAB signals.

Claim 62

The apparatus of claim 52 wherein said gamut defining means is a neural network.