JP3729985B2 - Print data correction apparatus, print data correction method, and software recording medium recording print data correction program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a print data correction apparatus, a print data correction method, and a medium on which a print data correction program is recorded.
[0002]
[Prior art]
In recent years, high-definition color ink-jet printers have advanced, and so-called photographic image quality has been reached. In such an ink jet printer, predetermined color inks are ejected in granular form, dots of a predetermined color are added to desired positions, and the image is expressed in a dot matrix. In this case, a color image is reproduced using three colors of cyan (C), magenta (M), and yellow (Y), or four color inks obtained by adding black (K) thereto.
[0003]
By the way, in order to come to be called photographic image quality, it is important to make dots finer, but color reproducibility is also extremely important. Despite the fact that colors are expressed in multi-tone data of red, green and blue (RGB) inside the computer, the printer can only handle CMYK two-tone data, so color space conversion and gradation conversion are performed. It has been broken. That is, two-tone display of CMYK is realized while maintaining colors expressed by RGB multi-tones. Of course, it is assumed here that each dot is colored at a specified density.
[0004]
However, although the print data is output while maintaining color reproducibility, the weight of the color ink particles varies depending on the machine difference for each print head. As a result, each dot is colored at its original density. It may not be said that it is doing.
[0005]
[Problems to be solved by the invention]
In the conventional color ink jet printer described above, if the amount of ink particles to be ejected varies depending on the machine body of the print head, it cannot be said that each dot is colored at its original density, resulting in color reproducibility. There was a problem that it sometimes deteriorated.
[0006]
Therefore, in the case of the present applicant, the print data is corrected in advance to compensate for the machine difference, and the color reproducibility is improved by printing based on the corrected print data. Such correction uses a correction table. In order to create this correction table, first, a patch is printed over all gradations by a reference print head that discharges ink ink particles of a reference weight. Print. Each patch is compared to find a combination of patches with no error, and the combination list is used as a correction table.
[0007]
Since patches need to be compared and compared in this way, it is very difficult to compare patches for all reproducible colors. Therefore, when a correction table was created for each element color, when printing a single color, it was possible to obtain almost the same color as in the case of the reference head. However, when the colors were mixed, the deviation occurred again.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a print data correction apparatus, a print data correction method, and a print data correction capable of reproducing colors more accurately regardless of machine differences such as a print head. An object is to provide a software recording medium in which a program is recorded.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, in order to print out a color image with a plurality of element colors based on print data, color ink for each element color is attached to a recording medium in a dot matrix form. to the printing apparatus comprising a print head, a print data correction device for correcting the print data to compensate for color changes based on the deviation of the amount of the color ink, along with some set to each element colors A correction amount storage means for storing a correction amount that compensates for a deviation in the usage amount of the color ink due to a difference in the body of the print head with respect to a reference print head that discharges a color ink particle of a reference weight, and determines a color mixture order for each dot And a correction amount adjusting means for adjusting the correction amount so as to reduce the correction amount as compared with the case of a single color when the same color mixture order increases, and based on the adjusted correction amount It is constituted comprising a correction means for correcting the print data.
[0010]
In the invention according to claim 1 configured as described above, the correction is made in response to the deviation of the usage amount of the color ink due to the machine difference of the print head relative to the reference print head caused by the machine difference of the print head of the printing apparatus. The amount storage means stores a correction amount for compensating for the deviation of the same usage amount for each element color, and the correction amount adjustment means determines the color mixture order for each dot and increases the color mixture order. The correction amount is set to a reduction amount that reduces the correction amount that compensates for the deviation in the amount of color ink used due to the difference in the print head body relative to the reference print head, compared to the case of a single color . Then, the correction means corrects the print data based on the adjusted correction amount.
[0011]
An experimental result was obtained that when the correction amount for a single color was applied to a mixed color, the correction amount set as a single color was too strong. This may be due to various factors, but it is reasonable to think that the amount of correction for each element color has a strong influence due to color mixing. The use of color ink due to the difference in the print head's body with respect to the reference print head during color mixing By reducing the correction amount for compensating the amount deviation, the correction amount set in the single color state is not used as it is in the case of mixed colors, and the reproducibility of mixed colors is improved. In this case, the mixed color order has a wide range such as a secondary color and a tertiary color, and it can be determined that the influence of the correction amount in the case of a single color decreases as the order increases. Therefore, the color reproducibility is improved by determining the color mixture order for each dot and reducing it to the optimum.
[0012]
The correction amount storage means may store a correction amount that can compensate for the deviation in the amount of color ink used due to the machine difference of the print head with respect to the reference print head for each element color. It is feasible. For example, assuming that the print data is gradation data, it may be stored in the form of a conversion table having conversion data corresponding to each gradation, or a predetermined calculation may be performed by inputting the print data. The calculation parameter may be stored as a function to be performed. Further, it is not necessarily stored individually, but may be stored in a form that is fused or compressed.
[0013]
The correction amount adjusting means only needs to determine the color mixture order for each dot and reduce the correction amount, and various methods can be adopted for determining the color mixture order. As an example thereof, the invention according to claim 2 is the print data correction apparatus according to claim 1, wherein the correction amount adjusting means determines variations in the component amounts of the respective element colors and varies evenly. In this configuration, it is determined that the color mixture order is the highest.
[0014]
In the invention according to claim 2 configured as described above, the correction amount adjusting means determines the variation in the component amount of each element color. If each element color has the same component amount, it is judged that the color mixture order is large because it is mixed at the same rate, and the component amount of the other element color is small relative to the element color even if it is mixed. For example, when considering the correction amount, it is appropriate to consider the degree of influence to be low and determine that the color mixture order is small. Therefore, it is determined that the color mixture order is the highest when the component amounts of the element colors are evenly dispersed.
[0015]
Various methods can be employed for obtaining the variation in the amount of components, and the method is not necessarily limited to a specific method. As an example of such a simple technique, the invention according to claim 3 is the print data correction apparatus according to claim 2, wherein the correction amount adjusting means includes the minimum component amount for each element color and the above-described amount. The variation is determined based on the ratio to the average value of the component amounts.
[0016]
In the invention according to claim 3 configured as described above, the correction amount adjusting means obtains a ratio between the minimum component amount for each element color and the average value of the component amounts. Here, the ratio is obtained, and if there are three element colors, the ratio of the sum of the three values to the minimum value is included. Then, the variation is determined based on this ratio.
[0017]
When the correction amount adjusting means determines the color mixture order, it is not necessarily limited to the determination based on the component amount, and the invention according to claim 4 is the print data correction apparatus according to claim 1, wherein The adjusting means is configured to determine the saturation and determine that the color mixture order is high when the saturation is low.
[0018]
In the invention according to claim 4 configured as described above, the correction amount adjustment means determines the saturation, but this saturation is similar in nature to the variation of the component amount, and the saturation is low. Each element color is uniform, and when the same saturation is high, the difference between the element colors is often large. Therefore, when the saturation can be easily determined, it can be adopted as a method for determining the color mixture order.
[0019]
When this correction amount adjusting means obtains an adjustment amount for reducing the correction amount for each dot, it is arbitrary at which point the adjustment amount is obtained. As an example thereof, the invention according to claim 5 is the print data correction device according to any one of claims 1 to 4, wherein the correction amount adjusting means determines the color mixture order for the print data for each dot. Thus, the adjustment amount of the correction amount is obtained.
[0020]
In the invention according to claim 5 configured as described above, the correction amount adjustment means determines the color mixture order every time print data is input for each dot, and obtains the adjustment amount of the correction amount. Of course, the case where it is determined for each unit where the print data is input is also included. That is, the correction amount is adjusted in accordance with the flow of print data.
[0021]
On the other hand, as another example, the invention according to claim 6 is the print data correction apparatus according to any one of claims 1 to 4, wherein the correction amount adjusting means is based on a combination of element colors. Thus, the adjustment amount of the correction amount is obtained in advance.
[0022]
In the invention according to claim 6 configured as described above, the correction amount adjusting means obtains the adjustment amount of the correction amount in advance based on the combination of the element colors. The adjustment amount obtained in advance may be a conversion table or the like, or if there are other conversion tables such as color conversion, they are incorporated into them so that color conversion and correction can be executed with a single reference. May be.
[0023]
As described above, the method of reducing and applying the correction amount set for each element color at the time of color mixing does not necessarily have to be a substantial device. As an example, the invention according to claim 7 can be applied to print data. to the printing apparatus comprising the print head to be attached to a recording medium the color ink of each element colors in a dot matrix in order to print out a color image by a plurality of element colors based, the bias of the amount of the color ink A print data correction method for correcting the print data to compensate for a color change based on the print head body relative to a reference print head that is set for each element color and discharges a color ink particle of a reference weight stores a correction amount for compensating for the deviation of the amount of the color inks due to the difference, if the color mixing degree is increased as well as determining color mixing degree in each dot To over single time by adjusting the correction amount to reduce the correction amount, it is constituted to fix the print data based on the adjusted correction amount.
[0024]
That is, there is no difference in that the method is not limited to the work to be corrected by a substantial apparatus, and is effective as a method.
[0025]
By the way, as described above, the print data correction apparatus for correcting the print data may exist alone or may be used in a state of being incorporated in a certain device. Is included. Further, it can be changed as appropriate, for example, by hardware or by software.
[0026]
In the case of software for color correction as an embodiment of the idea of the present invention, it naturally exists on a software recording medium in which such software is recorded, and it must be used.
[0027]
As an example, the invention according to claim 8 includes a print head that attaches color ink of each element color to a recording medium in a dot matrix form in order to print out a color image with a plurality of element colors based on print data. to the printing apparatus including, a software storage medium storing a print data hotfix the print data by a computer in order to compensate a color change based on the deviation of the amount of the color inks, each element colors And a correction amount that compensates for a deviation in the usage amount of the color ink due to a difference in the machine body of the print head with respect to a reference print head that discharges a color ink particle of a reference weight. When the same color mixture order increases, the correction amount is adjusted so as to reduce the correction amount as compared with the case of a single color. It is constituted to fix the print data based on the positive quantity.
[0028]
Of course, the software recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any software recording medium to be developed in the future. In addition, the duplication stages such as the primary duplication product and the secondary duplication product are equivalent without any question. In addition, even when the communication method is used as a supply method, the present invention is not changed, and the same applies to the case where data is written on a semiconductor chip.
[0029]
Furthermore, even when a part is software and a part is realized by hardware, there is no difference in the idea of the invention, and a part is stored on a software recording medium as needed. It may be in a form that is read appropriately.
[0030]
【The invention's effect】
As described above, according to the present invention, there is no difficulty in obtaining the correction amount of the mixed color in the sense that the correction amount is set for each element color, and the correction amount is optimized for the mixed color dot. Therefore, it is possible to provide a print data correction apparatus capable of substantially eliminating color misregistration due to machine difference and improving color reproducibility.
[0031]
According to the second aspect of the present invention, by determining the color mixture order with reference to the component amount, not only the color mixture number but also the influence degree can be determined, and the color reproducibility can be improved.
[0032]
Furthermore, according to the invention concerning Claim 3, the variation in a component amount is computable by comparatively simple calculation.
[0033]
Further, according to the fourth aspect of the present invention, the color mixture order can be obtained by using one reproduction element of the color called saturation, which is suitable when the saturation is obtained for other reasons.
[0034]
Further, according to the fifth aspect of the present invention, it is not necessary to calculate only the necessary color by obtaining the adjustment amount for each dot and to obtain the adjustment amount even for the unused color. In particular, if the result is cached, the amount of calculation is further reduced.
[0035]
Further, according to the sixth aspect of the present invention, if the adjustment amount is first obtained and the conversion table is formed, the conversion table is only referred to thereafter. Will be reduced.
[0036]
Furthermore, according to the invention concerning Claim 7, the printing data correction method which can improve the color reproducibility at the time of color mixing similarly can be provided.
[0037]
Furthermore, according to the invention concerning Claim 8, the software recording medium which recorded the print data correction program which can improve the color reproducibility at the time of color mixing similarly can be provided.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0039]
FIG. 1 shows a print data correction apparatus according to an embodiment of the present invention by a claim correspondence diagram. FIG. 2 shows a hardware configuration example of a printing system to which the print data correction apparatus is applied. .
[0040]
This printing system can be roughly classified into an image input device 10, an image processing device 20, and a printing device 30. The image input device 10 corresponds to a scanner 11, a digital still camera 12, or a video camera 14, and the image processing device 20 includes a computer 21, a hard disk 22, a keyboard 23, a CD-ROM drive 24, and a floppy disk drive 25. And the modem 26 and the display 27, and a specific example of the printing apparatus 30 corresponds to the printer 31 and the like. The modem 26 is connected to a public communication line, connected to an external network via the public communication line, and can be installed by downloading software and data.
[0041]
Here, the scanner 11 and the digital still camera 12 as the image input device 10 output RGB (green, blue, red) 256-gradation image data as image data, and the printer 31 as the printing device 30 is CMYK (cyan). , Magenta, yellow, and black) are required as input. Accordingly, in the computer 21 as the image processing apparatus 20, the 256 gradation image data is input, predetermined image processing and printing processing are performed, and output as two gradation image data. Note that an operating system 21a is running in the computer 21, a printer driver 21b and a display driver 21c corresponding to the printer 31 and the display 27 are incorporated, and the application 21d controls execution of processing by the operating system 21a. In addition, display on the display 27 is performed in cooperation with the display driver 21c, and printing processing is executed in cooperation with the printer driver 21b as necessary.
[0042]
In the present embodiment, in the process of generating print data in such a printing system, the print data correction device 30a inputs the generated print data, performs predetermined data correction, and outputs it. In this case, the correction amount storage means 30a1 holds a correction amount for correcting the machine difference for each element color as described later, and the correction amount adjustment means 30a2 determines the color mixture order for each dot. A reduction instruction is issued, and the correction means 30a3 corrects the data in a substantial sense while reducing the correction amount for each element color stored in the correction amount storage means 30a1 based on the correction amount reduction instruction from the correction amount adjustment means 30a2. Will do. Hereinafter, this process will be described in detail.
[0043]
First, the printer 31 that performs printing based on the corrected print data will be described. FIG. 3 shows a schematic configuration of the printer 31. A print head 31a including three print head units, a print head controller 31b for controlling the print head 31a, and a print head for moving the print head 31a in the digit direction. A digit moving motor 31c, a paper feed motor 31d for feeding print paper in the line direction, and a print controller 31b, a printer controller 31e corresponding to an interface between the print head digit moving motor 31c and the paper feed motor 31d and external devices. A dot printing mechanism is provided, and an image can be printed according to print data.
[0044]
FIG. 4 shows a more specific configuration of the print head 31a, and FIG. 5 shows an operation during ink ejection. A fine pipe line 31a3 extending from the color ink tank 31a1 to the nozzle 31a2 is formed in the print head 31a, and an ink chamber 31a4 is formed at a terminal portion of the pipe line 31a3. The wall surface of the ink chamber 31a4 is formed of a flexible material, and a piezoelectric element 31a5 that is an electrostrictive element is provided on the wall surface. The piezo element 31a5 has a crystal structure that is distorted by applying a voltage and performs high-speed electro-mechanical energy conversion. The distorted operation of the crystal structure pushes the wall surface of the ink chamber 31a4, thereby the ink chamber 31a4. Reduce the volume of the. Then, a predetermined amount of color ink particles are ejected vigorously from the nozzle 31a2 communicating with the ink chamber 31a4. This pump structure is called a micro pump mechanism.
[0045]
Note that two independent rows of nozzles 31a2 are formed in one print head unit, and color ink is supplied independently to the nozzles 31a2 in each row. Therefore, two print nozzle units are provided for each of the three print head units, and it is possible to use six color inks to the maximum. In the example shown in FIG. 3, two rows in the left print head unit are used for black ink, only one row in the middle print head unit is used for cyan ink, and in the right print head unit. The left and right two rows are used for magenta ink and yellow ink, respectively.
[0046]
Thus, in the present embodiment, the present invention is applied to the ink jet printer 31 that employs the micropump mechanism. In the printer 31 having an ink-jet dot adhesion mechanism, printing is performed by ejecting one ink particle for one dot from the above-described print head 31a. However, the size of one dot attached in this way is not necessarily constant, and there is a machine difference in the print head 31a. In the case where the printing density does not change by so-called overstrike, the dot size affects the printing density. Therefore, when the machine size difference occurs in the dot size, the printing density varies, and in color, the color balance and brightness, and in monochrome, the gray density varies.
[0047]
In the present embodiment, the ink jet printer 31 that employs the micropump mechanism has been described. However, the present invention can be applied to printers having other dot adhesion mechanisms as long as there is a difference in the size of the dot. is there.
[0048]
For example, as shown in FIG. 6, a bubble jet system in which a heater 31a8 is provided on the wall surface of a pipe line 31a7 in the vicinity of the nozzle 31a6, bubbles are generated by heating the heater 31a8, and colored ink is discharged with the pressure. This pump mechanism has also been put to practical use. Even in this case, it is undeniable that the difference in the airframe is caused by the ability of the heater 31a8 and the opening shape of the nozzle 31a6.
[0049]
FIG. 7 shows a schematic configuration of a so-called electrophotographic printer 33 as another mechanism. A charging device 33b, an exposure device 33c, a developing device 33d, and a transfer device 33e are arranged on the periphery of the rotating drum 33a as a photoconductor corresponding to the rotation direction, and the peripheral surface of the rotating drum 33a is made uniform by the charging device 33b. Then, the exposure device 33c removes the charge on the image portion, the developing device 33d attaches toner to the uncharged portion, and the transfer device 33e transfers the toner onto paper as a recording medium. Thereafter, the toner is passed between the heater 33f and the roller 33g to melt and fix the toner on the paper.
[0050]
Even in the case of such an electrophotographic printer 33, there is a variation in the amount of toner adhered due to the difference in the body of the charging device 33b, the exposure device 33c, or the rotating drum 33a itself. Therefore, a problem similar to that of the ink jet printer 31 occurs.
[0051]
In this embodiment, a computer system is incorporated between the image input apparatus 10 and the printing apparatus 30 to perform printing processing. However, such a computer system is not necessarily required. For example, as shown in FIG. 8, in a printer 32 that inputs and prints image data without going through a computer system, an image as print data inputted through a scanner 11b, a digital still camera 12b, a modem 26b, or the like. It is also possible to input data and make corrections to eliminate the machine difference.
[0052]
Next, a process in which print data is output to the printer 31 will be described. FIG. 9 shows the flow of image data. The image input device 10 outputs RGB multi-gradation (256 gradations) image data represented as dot-matrix pixels to the image processing device 20, and the image processing is performed. The apparatus 20 performs predetermined image processing and outputs the image data to the printing apparatus 30 as CMYK two-gradation image data (binary data). In the image processing apparatus 20, a color conversion process from the RGB color space to the CMYK color space is performed, and the RGB 256 gradation image data is converted into CMYK 256 gradation image data. Next, considering that the data that can be input by the printing apparatus 30 is two gradations, a halftone process for converting 256 gradation image data into two gradation image data is executed. The image data is output to the printing apparatus 30 as print data through such a process, but can be called print data in a broad sense because it is data about the same image in the previous process. The print data correction device 30a described above can theoretically perform correction processing on any stage of print data. In this embodiment, the CMYK 256-gradation image simultaneously with the color conversion processing. It shall be performed on data.
[0053]
FIG. 10 shows a color conversion table rewriting procedure for performing correction processing as color conversion processing. The contents will now be described according to the procedure.
[0054]
First, in step S100, a correction lookup table for the primary color (single color) is created. Here, a procedure for creating the correction lookup table will be described. As described above, first, a patch is printed over all gradations by the reference print head 31a that discharges a reference weight of color ink particles. In the present embodiment, since there are 256 gradations, the printed patch has a grid shape of 16 vertically and horizontally as shown in FIG. Next, patches are printed over all gradations in the same manner with the print head 31a having a difference in machine body. In the print head 31a having a difference in machine body, since the weight of the ejected ink particles is deviated, the print density is deviated and does not coincide with the patch printed over all gradations by the reference print head 31a.
[0055]
Therefore, as shown in FIG. 12, each patch printed by the reference print head 31a is individually compared with each patch printed by the print head 31a having a difference in machine body, and the gradations of the matching patches are compared. In the figure, a combination of patches that are printed when predetermined gradation data is input and that have the same print density is shown. Therefore, this combination forms a correction lookup table as it is. In the present embodiment, since three print heads 31a are provided, a correction lookup table is created for each print head 31a. Such a correction look-up table contains the above-described correction amount, and in this sense, it can also be said to be a correction amount for each element color.
[0056]
If the correction look-up table created for each print head 31a in this way is used, it can be considered that corrections can be made in the same way for colors other than the primary color, but in reality, secondary colors and tertiary colors are used. Deviations appear when color mixing occurs.
[0057]
Therefore, in step S110, the correction amount in the correction lookup table is reduced, and the secondary color patch is printed. Here, the adjustment of the reduction amount is expressed by multiplying the correction amount by a predetermined coefficient, and FIG. 13 shows a correction lookup table when the coefficient is set in increments of “0.1”. Since the correction amount is small in the low gradation region and the high gradation region, it is difficult to see the change. However, when the vicinity of the gradation “180” where the correction amount is maximum is seen, the correction amount is “1.0” as the correction amount. It can be seen that the amount of correction is reduced by almost “2” gradation data by decreasing the coefficient in increments of “0.1” for the difference in 20 ”gradation data. Of course, in the case of a secondary color, an individual correction look-up table for each print head 31a multiplied by the same coefficient is used. In this case, the step size of the coefficient does not necessarily have to be “0.1”.
[0058]
In step 120, the color of the patch at the reference print head 31a printed in this way for the secondary color and the patch at the print head 31a having a difference in machine body with the coefficient α2 changed are respectively measured, and the error is reduced as a whole. The coefficient α2 is determined. According to the experimental results, the coefficient α2 is most preferably “0.8”.
[0059]
Next, the coefficient α3 for the tertiary color is determined by the same method. That is, in step S130, the coefficient α3 is changed to print a tertiary color patch, and in step S140, the optimum coefficient α3 is determined in comparison with the patch on the reference print head 31a. It was confirmed that the optimum coefficient α3 for this tertiary color is about “0.6”.
[0060]
Here, the secondary color and tertiary color patches are printed by adding the respective element colors uniformly. In these cases, the coefficients confirmed as described above are optimal. However, the mixed state of the element colors in each pixel in the actual print data is various, and the coefficient α2 is not necessarily optimal for the secondary color and the coefficient α3 is not optimal for the tertiary color.
[0061]
Here, referring to FIG. 14 in which the components of each pixel are represented by component values of element colors, when the largest component value is H, the smallest component value is L, and the intermediate component value is M, the component value L The element colors are all satisfied, the two component colors are satisfied for the component value L and the component value M or less, and only one element color is satisfied for the component value M or more. ing. Accordingly, a component s1 having a component value L or less that satisfies all the element colors is considered as a component of a tertiary color, and a portion having a component value L or more and a component value M or less is considered as a secondary color component, and a portion having a component value M or more. Is a primary color component, and the total component s1, s2, s3 with respect to the sum S of all components is multiplied by a coefficient α3, a coefficient α2, and a coefficient 1.0 to obtain a coefficient α0. That is,
α0 = α3 × (s1 / S) + α2 × (s2 / S) + 1.0 × (s3 / S) (1)
The coefficient α0 is used.
[0062]
In this case, the hardware and software that store at least the correction lookup table for the primary color constitute the correction amount storage means 30a1, and the hardware and software that calculate the coefficient α0 based on the equation (1) adjust the correction amount. The means 30a2 is configured.
[0063]
Of course, the formula (1) used by the correction amount adjusting means 30a2 is merely an example, and the correction amount is reduced as the mixed color order increases to the secondary color or the tertiary color by using at least the primary color correction lookup table. The coefficient α0 may be used.
[0064]
For example, a parameter indicating how close the color is to the tertiary color can be used. In the example of RGB, a parameter (gray degree) is set to “100” when close to gray and “0” when close to the primary color. If this gray degree is “100”, a coefficient α3 is adopted. If the gray level is “0”, the coefficient “1.0” is adopted. This gray degree can be obtained as follows. Now, assuming that the input data value (component amount) for each ink is in_dataC1, in_dataC2, and in_dataC3, the minimum input data value MIN_value is
MIN_value = min (in_dataC1, in_dataC2, in_dataC3)
The maximum input data value MAX_value is
MAX_value = max (in_dataC1, in_dataC2, in_dataC3)
MID_value that is intermediate between the input data values is
MID_value = mid (in_dataC1, in_dataC2, in_dataC3)
It is assumed that In this case, the gray degree gray is
gray = (MIN_value × 3) / (MIN_value + MAX_value + MID_value)
It will be expressed as Of course, the numerator may be MIN_value, and the denominator may be an average value. The coefficient αg for the gray degree gray is
αg = 1−0.4 × (gray / 100) (2)
It can be calculated by
[0065]
In the present embodiment, the gray level gray and the coefficient αg are made to correspond to each other based on the expression (2), but can be finely adjusted. For example, FIG. 15 shows a graph as an example, and the rate of change of the coefficient αg is slightly increased in the region where the gray degree gray is high.
[0066]
FIG. 16A shows a case where the gray level is “100”. This is a case where the input data values of the respective inks match. FIG. 5B shows a case where the gray level is “0”, and only one element color is a primary color having a component amount. Further, FIG. 5C shows a case where the gray degree is “50”. When the input data value of each ink is 1: 2: 3, the gray degree is “50”. In this case, the coefficient αg is “0.8” according to the expression (2), but the coefficient α0 is “0.7333” according to the expression (1), and both are different. Therefore, it may be selected as appropriate based on the output result.
[0067]
On the other hand, such a concept of grayness has a property common to the concept of saturation, which is a color expression element. FIG. 17 schematically shows the L * a * b * color space. The brightness L * is taken in the vertical direction in the three-dimensional space, and the color is represented by plane coordinates in the horizontal plane. The plane coordinates in the horizontal plane are expressed by the orthogonal coordinates of the a * axis and the b * axis, becoming closer to gray as it goes to the origin, and becoming more vivid as it goes to the periphery. Of course, the distance from the origin is saturation, and the distance from the origin is inversely proportional to the gray level. When the print data has such indirect or direct saturation elements, the coefficient αs is determined using the saturation, and the correction amount is referred to the correction lookup table for each element color. Can be reduced.
[0068]
The correction unit 30a3 that realizes the above correction method may correct the data based on the CMYK print data by using the coefficient based on the equation (1) or (2) and the correction lookup table. Since the color conversion table is also referred to when the color conversion from RGB to CMYK is performed, the correction work is completed by referring to the table once by rewriting the color conversion table. Therefore, in step S150, the corrected coefficient correction lookup table is written in the color conversion table.
[0069]
The above-described procedure is executed when the printer driver 21b is activated in the computer 21, and the operation of the present embodiment having the above-described configuration will be described below with reference to the flowchart of the printer driver 21b shown in FIG. .
[0070]
Assuming that the image data read by the scanner 11 is printed by the printer 31, first, the application 21d is started and the scanner 11 starts reading while the operating system 21a is running on the computer 21. Let When the read image data is taken into the application 21d via the operating system 21a, predetermined image processing is performed and printing processing is selected.
[0071]
When the printing process is selected, the operating system 21a activates the printer driver 21b. Since the primary color correction lookup table does not exist when the printer driver 21b is first activated, a single color patch is printed in step S205 after the determination in step S200. On the other hand, a patch printed by the reference print head 31a is prepared separately, compared with the patch printed by the print head 31a provided for each printer 31, and a value for which correspondence is obtained is input in step S210.
[0072]
Using this result, a secondary color patch is printed in step S215. At this time, the coefficients are changed to print several patches, and the coefficient α2 for the patch that seems to be optimal is determined in step S220. Similarly, in step S225, a patch of the tertiary color is printed, and in step S230, the coefficient α3 for the patch that seems to be optimal is determined. That is, the coefficients α2 and α3 are input as to coefficients that are considered optimal. Once the above processing is performed, it is effective as long as the print head 31a does not change.
[0073]
However, it is assumed that the coefficients α2 and α3 need to be obtained for the processes in steps S215 to S230. The coefficients α2 and α3 have been experimentally determined, and it has been found that numerical values of “0.8” and “0.6” are suitable, respectively, and even if these values are used as defaults, they are sufficiently effective. The result is obtained. Therefore, as long as a single color patch is printed at least in steps S205 and S210 and a predetermined corresponding value can be input, the processing in steps S215 to S230 may be omitted.
[0074]
At the first startup, the above-described printing and input are performed, and in the next step S240, processing for writing in the color conversion table is performed. That is, for each color in the color conversion table, the correction value is reduced by using the formula (1) or (2), and the conversion value is calculated and rewritten.
[0075]
Thereafter, the RGB print data created by the application 21d is color-converted into CMYK print data in step S250. Of course, what is used for the color conversion at this time is a color conversion table in which a predetermined correction amount is written in step S240, and necessary corrections are added simultaneously with the color conversion.
[0076]
When the color conversion is completed, the print data remains at 256 gradations. In step S255, the print data is converted into two-gradation print data that can be input by the printer 31 and output to the printer 31. When the printer 31 inputs such print data, the reduction amount of the correction look-up table is an optimum value in the vicinity of the aiming color, and clean printing without color misregistration is performed as in the case of printing with the reference print head 31a. It becomes possible.
[0077]
As described above, when the recording material such as the color ink constituting the dot as in the ink jet printer 31 fluctuates due to the machine difference, it is impossible to set the correction amount of the color misregistration for each color. After obtaining the correction amount for a single color, determine the color mixture order of each dot, and apply it while reducing the correction amount as the color mixture order increases, so that the optimal correction according to the color mixture order of each dot The color reproducibility can be improved by compensating for the machine difference.
[Brief description of the drawings]
FIG. 1 is a diagram corresponding to claims of a print data correction apparatus according to the present invention.
FIG. 2 is a block diagram illustrating a specific hardware configuration example of a printing system to which the print data correction apparatus is applied.
FIG. 3 is a schematic block diagram of a printer.
FIG. 4 is a schematic explanatory diagram of a print head unit in the printer.
FIG. 5 is a schematic explanatory diagram illustrating a situation in which color ink is ejected by the print head unit.
FIG. 6 is a schematic explanatory diagram illustrating a situation in which color ink is discharged by a bubble jet type print head.
FIG. 7 is a schematic explanatory diagram of an electrophotographic printer.
FIG. 8 is a schematic block diagram illustrating another application example of the print data correction apparatus of the present invention.
FIG. 9 is a block diagram illustrating a specific procedure of print processing.
FIG. 10 is a flowchart illustrating a color conversion table rewriting procedure.
FIG. 11 is a diagram illustrating patches to be printed.
FIG. 12 is a diagram illustrating a comparison between a patch by a reference print head and a patch by a print head having a difference in machine body.
FIG. 13 is a diagram showing a correction look-up table in which coefficients are changed.
FIG. 14 is a diagram illustrating a state in which a coefficient corresponding to a color mixture order is weighted and added according to a pixel component.
FIG. 15 is a graph showing another example of correspondence between gray levels and coefficients.
FIG. 16 is a diagram illustrating a specific example of the gray degree.
FIG. 17 is a diagram illustrating an L * a * b * color space when using saturation.
FIG. 18 is a flowchart of a printer driver.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Image input device 20 ... Image processing device 21 ... Computer 23 ... Keyboard 30 ... Printing devices 31-33 ... Printer

Claims (8)

To the printing apparatus comprising the print head to be attached to a recording medium the color ink of each element colors in a dot matrix in order to print out a color image by a plurality of element colors based on print data, the amount of the color ink A print data correction device for correcting the print data to compensate for a color change based on the bias of
A correction amount storage means for storing a correction amount which is set for each element color and which compensates for a deviation in the usage amount of the color ink due to a machine body difference of the print head with respect to a reference print head which discharges a color ink particle of a reference weight. When,
A correction amount adjusting means for determining the color mixture order for each dot and adjusting the correction amount so as to reduce the correction amount as compared with the case of a single color when the color mixture order increases;
A print data correction apparatus comprising: correction means for correcting the print data based on the adjusted correction amount. 2. The print data correction apparatus according to claim 1, wherein the correction amount adjustment unit determines a variation in the component amount of each element color, and determines that the color mixture order is the highest when there is an even variation. The print data correction device. 3. The print data correction apparatus according to claim 2, wherein the correction amount adjusting unit determines the variation based on a ratio between a minimum component amount for each element color and an average value of the component amounts. Print data correction device. 2. The print data correction apparatus according to claim 1, wherein the correction amount adjustment means determines the color mixture order to be high when the saturation is determined and the saturation is low. 5. The print data correction apparatus according to claim 1, wherein the correction amount adjustment unit determines the color mixture order for print data for each dot to obtain an adjustment amount of the correction amount. A print data correction device characterized by the above. 5. The print data correction apparatus according to claim 1, wherein the correction amount adjusting unit obtains an adjustment amount of the correction amount in advance based on a combination of each element color. Print data correction device. To the printing apparatus comprising the print head to be attached to a recording medium the color ink of each element colors in a dot matrix in order to print out a color image by a plurality of element colors based on print data, the amount of the color ink A print data correction method for correcting the print data in order to compensate for a color change based on the bias of the print, the print on the reference print head that is set for each element color and discharges a color ink particle of a reference weight Stores a correction amount that compensates for deviations in the amount of color ink used due to head machine differences , determines the color mixture order for each dot, and reduces the correction amount compared to a single color when the color mixture order increases. A method for correcting print data, comprising: adjusting a correction amount in order to correct the print data based on the adjusted correction amount. To the printing apparatus comprising the print head to be attached to a recording medium the color ink of each element colors in a dot matrix in order to print out a color image by a plurality of element colors based on print data, the amount of the color ink A software recording medium on which a print data correction program for correcting the print data is corrected by a computer to compensate for a color change based on the bias of the color ink particles set for each element color and having a reference weight When a correction amount that compensates for a deviation in the usage amount of the color ink due to the difference in machine body of the print head with respect to a reference print head that discharges ink is stored, the color mixture order is determined for each dot, and the color mixture order increases The correction amount is adjusted to reduce the correction amount as compared with the case of single color, and the print data is corrected based on the adjusted correction amount. Recorded software recording medium the print data modification program characterized and.

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