COLOR PREDICTION METHOD, PRINT DATA GENERATION APPARATUS, AND COLOR PREDICTION PROGRAM
FIG3 is a diagram showing a hardware configuration of a print data generation apparatus in the embodiment
FIG3 is a diagram showing a hardware configuration of the print data generation apparatus 100 in the present embodiment. The print data generation apparatus 100 is implemented by a personal computer, and includes a CPU 11, a ROM 12, a RAM 13, an auxiliary storage device 14, an input operation unit 15 such as a keyboard, a display unit 16, an optical disk drive 17, and a network interface unit 18. The submitted data transmitted via the communication line 600 is inputted into the print data generation apparatus 100 via the network interface unit 18. Print data generated by performing the color prediction process and the like by the print data generation apparatus 100 is sent to the digital printing apparatus 400 through the communication line 600 via the network interface unit 18.
diagram
141
program
18
network interface unit
100
2
color
600
communication line
300
printing apparatus
16
display unit
500
colorimeter
15
Equation
200
plate making apparatus
170
optical disk
13
Equation
['8. A print data generation apparatus (100) that generates print data in a format printable by a digital printing apparatus (400) on the basis of submitted data, the print data generation apparatus (100) comprising: color prediction means (S610 to S630) configured to perform a color prediction process in which pixel data is read from the submitted data on a pixel-by-pixel basis, and a color of the read pixel data is predicted; XYZ data generation means (S640) configured to generate XYZ data representing color tristimulus values X, Y, and Z on the basis of a result obtained by the color prediction process; first data conversion means (S650) configured to convert the XYZ data into Lab data that is data of a CIELAB color space; and second data conversion means (S660) configured to convert the Lab data into print data in a format printable  by the digital printing apparatus, wherein the color prediction process includes a process for predicting a color obtained by sequentially overprinting, on a base material, inks of a first printing color to an Nth (N is an integer of 2 or more) printing color, the color prediction means (S610 to S630) includes first reflectance obtaining means (S10) configured to obtain, as a first reflectance, a reflectance of a unit region with a state where an ink of the first printing color is applied on the base material, and calculation means (S20) configured to perform a calculation process which is executed (N-1) times for pixel data of one pixel, and in the calculation process, during a Kth (K is an integer of 1 or more and N-1 or less) execution, a reflectance of the unit region with a state where inks of the first printing color to a (K+1)th printing color are sequentially overprinted on the base material is calculated, and the calculation means (S30) includes second reflectance calculation means (S310) configured to calculate, as a second reflectance, a reflectance of a printing region with a state where the ink of the first printing color is applied on the base material, when a value of the K is 1, and to calculate, as a second  reflectance, a reflectance of a printing region with a state where an ink of a Kth printing color is overprinted on an ink of a (K-1)th printing color, when the value of the K is 2 or more, third reflectance calculation means (S320 and S330) configured to calculate, as a third reflectance, a reflectance of the unit region with a state where, assuming that a transparent ink is applied on the base material, an ink of a (K+1)th printing color is overprinted on the transparent ink, first conversion equation calculation means (S340) configured to obtain a first conversion equation representing a line connecting first coordinates and second coordinates regarding a color prediction coordinate system where an abscissa represents a product of a reflectance of a background and a reflectance of a foreground and an ordinate represents a reflectance of a state where the background and the foreground overlap, the first coordinates corresponding to a combination of a product of a fourth reflectance that is a reflectance of the base material and a fifth reflectance that is a reflectance of a state where the ink of the (K+1)th printing color is applied on the base material, and the third reflectance, the second coordinates corresponding to a combination of a product of a sixth reflectance that is a reflectance of a  state where a black ink is applied on the base material and the fifth reflectance, and a seventh reflectance that is a reflectance of a state where the ink of the (K+1)th printing color is overprinted on the black ink, eighth reflectance calculation means (S350) configured to calculate, as an eighth reflectance, a reflectance of a printing region with a state where the ink of the (K+1)th printing color is overprinted on the ink of the Kth printing color on the basis of the second reflectance and the fifth reflectance, using the first conversion equation, second conversion equation calculation means (S360) configured to obtain a second conversion equation representing a line connecting third coordinates and fourth coordinates regarding the color prediction coordinate system, the third coordinates corresponding to a combination of a product of the second reflectance and the fifth reflectance, and the eighth reflectance, the fourth coordinates corresponding to a combination of a product of the fourth reflectance and the fifth reflectance, and the fifth reflectance, and first reflectance update means (S370) configured to calculate a reflectance of the unit region with a state where the inks of the first printing color to the (K+1)th printing color are sequentially overprinted on the base  material on the basis of the first reflectance and the fifth reflectance, using the second conversion equation, and to update the first reflectance with the calculated reflectance.', '9. A color prediction program (141) for predicting a color obtained by sequentially overprinting, on a base material, inks of a first printing color to an Nth (N is an integer of 2 or more) printing color, the program comprising, a first reflectance obtaining step (S10) of obtaining, as a first reflectance, a reflectance of a unit region with a state where an ink of the first printing color is applied on the base material, and a calculation step (S30) of calculating a reflectance of the unit region, the calculation step being executed (N-1) times, and in the calculation step, during a Kth (K is an integer of 1 or more and N-1 or less) execution, the reflectance of the unit region with a state where inks of the first printing color to a (K+1)th printing color are sequentially overprinted on the base material is calculated, wherein the calculation step (S30) includes: a second reflectance calculation step (S310) of calculating, as a second reflectance, a reflectance of a printing region with a state where the ink of the first  printing color is applied on the base material, when a value of the K is 1, and of calculating, as a second reflectance, a reflectance of a printing region with a state where an ink of a Kth printing color is overprinted on an ink of a (K-1)th printing color, when the value of the K is 2 or more; a third reflectance calculation step (S320 and S330) of calculating, as a third reflectance, a reflectance of the unit region with a state where, assuming that a transparent ink is applied on the base material, an ink of a (K+1)th printing color is overprinted on the transparent ink; a first conversion equation calculation step (S340) of obtaining a first conversion equation representing a line connecting first coordinates and second coordinates regarding a color prediction coordinate system where an abscissa represents a product of a reflectance of a background and a reflectance of a foreground and an ordinate represents a reflectance of a state where the background and the foreground overlap, the first coordinates corresponding to a combination of a product of a fourth reflectance that is a reflectance of the base material and a fifth reflectance that is a reflectance of a state where the ink of the (K+1)th printing color is applied on the base material, and the third reflectance,  the second coordinates corresponding to a combination of a product of a sixth reflectance that is a reflectance of a state where a black ink is applied on the base material and the fifth reflectance, and a seventh reflectance that is a reflectance of a state where the ink of the (K+1)th printing color is overprinted on the black ink; an eighth reflectance calculation step (S350) of calculating, as an eighth reflectance, a reflectance of a printing region with a state where the ink of the (K+1)th printing color is overprinted on the ink of the Kth printing color on the basis of the second reflectance and the fifth reflectance, using the first conversion equation; a second conversion equation calculation step (S360) of obtaining a second conversion equation representing a line connecting third coordinates and fourth coordinates regarding the color prediction coordinate system, the third coordinates corresponding to a combination of a product of the second reflectance and the fifth reflectance, and the eighth reflectance, the fourth coordinates corresponding to a combination of a product of the fourth reflectance and the fifth reflectance, and the fifth reflectance; and a first reflectance update step (S370) of calculating a reflectance of the unit region with a state where the inks of the first printing color to the (K+1)th printing color are sequentially overprinted on the base material on  the basis of the first reflectance and the fifth reflectance, using the second conversion equation, and of updating the first reflectance with the calculated reflectance.']