JP5056403B2 - Image processing apparatus, image recording apparatus, and program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image recording apparatus, and a program.

  In an inkjet printer that records an image using a recording head that ejects ink droplets from nozzles, the recording head is driven according to image data to eject ink droplets onto a recording medium to record an image.

  In recent years, in this type of ink jet printer, development of reactive two-component ink has been promoted. In image recording using two-component ink, the ink and the processing liquid are reacted on the recording medium by ejecting the ink and the processing liquid onto the recording medium, respectively. Accordingly, the color material in the ink can be aggregated and spread.

  However, in the image recording using the two-liquid ink, there is a problem that the landing position of the dots may be shifted depending on the head position or the like, and the aggregation is biased due to the positional shift between the ink and the processing liquid. Furthermore, if the ink and the treatment liquid overlap even a little, the cohesive effect is exhibited according to the overlapping ratio, but the ink and the treatment liquid do not overlap at all, and if there is no reaction, there is a significant difference in the dot shape. Occurs. In particular, in the highlight area, the influence is large because the dots are dispersed.

  In order to solve this problem, it is conceivable that the treatment liquid is discharged in a larger amount than the target amount.

  On the other hand, in image recording using two-liquid ink, both the ink liquid and the treatment liquid are ejected onto the recording medium, and particularly when printing on plain paper, the amount of solvent relative to the recording medium is too large. The problem is that the recording medium curls or the recording medium slips through. Furthermore, there is a problem of an increase in processing solution run cost. For this reason, it is calculated | required to reduce a process liquid.

In a region where the amount of ink to be ejected is large, the problem caused by reducing the ratio of the treatment liquid is small. Therefore, Patent Document 1 discloses that the treatment liquid is ejected to the same location as the ink data at a predetermined concentration or lower, and the ink is discharged at a predetermined concentration or higher. There has been proposed a method of reducing the ratio of the processing liquid in the high concentration region by discharging the processing liquid to a portion thinned out from the data.
Japanese Patent No. 3314031

  An object of the present invention is to achieve both prevention of deterioration of ink graininess and reduction of the discharge amount of a treatment liquid, as compared with the case where the discharge positions of the inks of the respective colors are not concentrated.

In the invention of the image processing apparatus according to the first aspect, the gradation value of each of a plurality of different colors of each pixel is quantized to an N value (N is an integer of 3 or more) so that a plurality of droplets are ejected in an overlapping manner. And a discharge data generating means for generating discharge data for discharging liquid droplets in N stages of discharge amounts for each of the plurality of different colors, and a color material by being mixed into the liquid droplets for each pixel liquid amount ejected the processing liquid, said regardless of the discharge rate of the plurality of colors each of droplets ejected to each pixel based on the discharge data of each color are ejected to each pixel to aggregate as little Kunar so the number of colors droplets is large, is configured to include a, a treatment liquid data generating means for generating the processing liquid data for ejecting the treatment liquid.

According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the ejection data creating means performs quantization by an error diffusion method, and at least the pixels of at least one color droplet ejected. It is configured to include a pulling-down means for lowering only the minimum threshold value among (N-1) threshold values to be compared with gradation values of colors other than one color.

Invention of images recording apparatus according to claim 3, an image processing apparatus according to claim 1 or claim 2, on the basis of the ejection data generated by said discharge data forming means, the plurality of the recording medium First discharge means for discharging each droplet of color, and second discharge means for discharging the treatment liquid onto the recording medium based on the treatment liquid data created by the treatment liquid data creation means; It is configured with.

The invention of claim 4 quantizes the gradation value of each of a plurality of different colors of each pixel into an N value (N is an integer of 3 or more) such that a plurality of droplets are overlapped and ejected to a computer. A step of creating ejection data for ejecting droplets in N stages of ejection amounts for each of the plurality of different colors , and a processing liquid for aggregating color materials by being mixed with the droplets for each pixel The number of droplets discharged to each pixel is independent of the amount of each droplet discharged from the plurality of colors based on the discharge data of each color. as little Kunar so in many, a program for executing the steps of: creating a processing liquid data for ejecting the treatment liquid.

According to the first and fourth aspects of the invention, compared with the case where the discharge positions of the droplets of the plurality of colors are not concentrated, the deterioration of the graininess is prevented and the discharge amount of the processing liquid is reduced. The effect of being able to make it compatible is acquired.

  According to the invention of claim 2, compared to the case of independently quantizing for each color, there is a higher probability that the color droplets are ejected to the same pixel, while preventing deterioration in graininess, The effect that the discharge amount of the processing liquid can be reduced is obtained.

According to the invention of claim 3 , compared with the case where the discharge positions of the droplets of each of the plurality of colors are not concentrated, it is possible to achieve both prevention of deterioration of graininess and reduction of the discharge amount of the processing liquid. The effect of being able to be obtained is obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where the present invention is applied to an inkjet printer will be described.

  First, the overall configuration of the inkjet printer 10 according to the present embodiment will be outlined with reference to FIG.

  As shown in FIG. 1, the inkjet printer 10 includes a paper feed cassette 12 in which paper (recording medium) P is accommodated. A feed roll 14 that takes out the paper P from the inside of the paper feed cassette 12 is disposed at the top of the paper feed cassette 12 on the front end side (left end side in FIG. 1).

  A first conveyance path 18 extending from the leading end of the paper feed cassette 12 and reaching the recording unit 16 for recording an image on the paper P is provided. The first transport path 18 is provided with a plurality of first transport roll pairs 20 that sandwich and transport the paper P to the recording unit 16.

  Furthermore, a second transport path 24 is provided that extends upward from the recording unit 16 and reaches the discharge tray 22 that stores the paper P on which an image is recorded. A plurality of second transport roll pairs 26 that transport the paper P to the discharge tray 22 are provided in the second transport path 24. A reverse conveyance path 36 for duplex printing is connected from the second conveyance path 24 to the first conveyance path 18.

  With the above configuration, the paper P taken out from the paper feed cassette 12 by the feed roll 14 is transported through the first transport path 18 by the plurality of transport roll pairs 20 and sent to the recording unit 16 for image recording. The sheet on which the image is recorded is transported through the second transport path 24 by a plurality of transport roll pairs 26 and is discharged to the discharge tray 22. When performing double-sided printing, the paper on which single-sided printing has been performed is transported from the second transport path 24 via the reverse transport path 36 to the first transport path 18 and sent again to the recording unit 16 to perform image recording. Is called. As described above, a series of image recording is performed. Note that the holding of the paper P is performed by electrostatic attraction force. The sheet P is pressed against the transport path 24 by a charging roll (not shown) and charges are applied to the sheet P to generate an attracting force.

  Next, the configuration of the recording unit 16 will be described.

  The recording unit 16 includes a drive roll 28 disposed on the upstream side in the sheet conveyance direction and an endless conveyance belt 32 wound around a driven roll 30 disposed on the downstream side. 1 is configured to circulate (rotate) in the direction of arrow A (clockwise). Further, a nip roll 38 that is in sliding contact with the transport belt 32 from the front side is disposed on the drive roll 28.

  An ink jet recording head 34 is disposed above the transport belt 32. The inkjet recording head 34 has a long shape in which the effective recording area is equal to or larger than the width of the paper P (the length in the direction orthogonal to the transport direction), promotes ink fixing, and improves image density and water resistance. Processing liquid head 34T that discharges the processing liquid for the purpose of, and four ink heads that respectively discharge yellow (Y), magenta (M), cyan (C), and black (K) inks 34Y, 34M, 34C, and 34K are arranged along the transport direction, and can record full-color images.

  Each of the ink heads 34Y, 34M, 34C, and 34K for each color is configured such that a plurality of ink discharge ports (nozzles) are arranged over the entire width of the effective recording area of the paper P.

  Ink droplets may be ejected by a known method such as a thermal method or a piezoelectric method.

  The ink jet recording head 34 faces the flat portion 32F of the transport belt 32, and the facing region is an ejection region where ink droplets and processing liquid are ejected from the ink jet recording head 34. The paper P transported through the first transport path 18 is held by the transport belt 32, reaches the discharge region, and faces the ink jet recording head 34. Treatment liquid is attached.

  Further, above the ink jet recording head 34, the ink tanks 40Y, 40M, 40C, and 40K that supply ink to the ink heads 34Y, 34M, 34C, and 34K, and the processing liquid that supplies the processing liquid to the processing liquid head 34T. A tank 40L is provided.

  Further, a maintenance unit (not shown) corresponding to each color including a dummy jet receiving member, a wiping member, a cap member and the like is provided at a position that can be opposed to the nozzle surface of the inkjet recording head 34 or a position that can be moved to the opposed position. Deploy.

  The maintenance units for Y and M are arranged on the left side in FIG. 1 with respect to the ink heads 34Y and 34M. Further, the maintenance units for C and K are arranged on the right side in FIG. 1 with respect to the ink heads 34C and 34K.

  At the time of maintenance, the inkjet recording head 34 is raised, and the maintenance unit is slid from the left and right to move to face the corresponding nozzle surfaces.

  As shown in FIG. 2, the print engine 50 including the ink heads 34Y, 34M, 34C, 34K and the processing liquid head 34T is a system controller in which a CPU 52, a ROM 54, a RAM 56, and the like are connected by a bus 58. 60. For example, the system controller 60 determines the ejection timing of the ink droplets and the processing liquid and the nozzle to be used according to the image information, and inputs drive signals to the ink heads 34Y, 34M, 34C, 34K and the processing liquid head 34T. Thus, the ink jet recording head 34 is controlled.

  Next, the treatment liquid head 34T and the ink heads 34Y, 34M, 34C, and 34K that can be used in the inkjet printer 10 having the above-described configuration will be described in detail.

  Each of the ink heads 34Y, 34M, 34C, and 34K is connected to the bus 58 of the system controller 60, and is driven by a multi-value (large dot, medium dot, small dot, and so on) by a drive circuit (not shown) controlled by the system controller 60. Analog drive with no dots. By making the ink heads 34Y, 34M, 34C, and 34K multi-valued, high speed and high image quality can be achieved. That is, by ejecting large dots, ink can be placed on a large area, so that it can be output at high speed, and by ejecting small dots, the graininess can be improved and output with high image quality. In order to eject dots of different sizes from one nozzle, for example, when ejecting large dots, medium dots, and small dots, voltages having different waveforms are applied to the ink heads 34Y, 34M, 34C, and 34K, respectively. Applied.

  The treatment liquid head 34T is connected to the bus 58 of the system controller 60, and is driven by a multi-value (large dot ejection / medium dot ejection / small dot ejection / dot) by a drive circuit (not shown) controlled by the system controller 60. The drive is controlled without discharge. When ejecting large dots, medium dots, and small dots in the same manner as the ink heads 34Y, 34M, 34C, and 34K in order to eject dots having different sizes from one nozzle, voltages having different waveforms are used. Is applied to the ink head 34T.

  The system controller 60 can be connected to a personal computer or the like via a network interface (not shown).

Next, image processing performed by the system controller 60 will be described.
(First embodiment)
A first embodiment of image processing performed by the system controller 60 will be described with reference to FIGS.

  A program for executing this image processing is stored in a ROM 54 that is a storage medium of the system controller 60.

  FIG. 3 is a conceptual diagram of the image data G. Image data G for forming an image represents pixel values representing gradation values of a large number of pixels g. In FIG. 3, an arrow M indicates a scanning direction M, that is, a sheet conveyance direction, and an arrow N indicates a nozzle arrangement direction N. Hereinafter, each pixel included in the image is identified as a pixel g (x, y), where x is the position coordinate in the nozzle arrangement direction N and y is the position coordinate in the scanning direction M. Note that 1 ≦ x ≦ n (n: the number of pixels in the nozzle arrangement direction N), 1 ≦ y ≦ m (m: the number of pixels in the scanning direction M), and the values of n and m differ depending on the image data G. In addition, an image is formed on the pixels g having the same value of x by ink ejected from the same nozzle.

  In the image processing, as shown in FIG. 4, first, original data of an image to be recorded is input. As the original data, for example, data in which gradation values of R, G, and B colors of each pixel are expressed in 256 gradations from 0 to 255 using 8 bits is used. Hereinafter, a case where data represented by 256 gradations is used will be described. However, gradations can be set to various values.

  The system controller 60 performs resolution conversion and color conversion processing on the input original data, and converts 8-bit R, G, B image data into 8-bit K, M, C, and Y gradations. It is converted into data for each pixel represented by a value. This color conversion process is a process for converting image data represented by each of R, G, and B colors into image data represented by each of Y, M, and C colors, and Y, M for each pixel. , C color conversion processing for replacing each of the C colors with K colors.

  Further, the system controller 60 compares, for example, 2-bit K, M, C, and Y data for each pixel represented by 8-bit K, M, C, and Y gradation values with a threshold value. Are converted (quantized) into data represented by the respective tone values. The 2-bit gradation value represents one of four values “0”, “1”, “2”, and “3”. '0' indicates no dot discharge (discharge amount 0), '1' indicates small dot discharge (discharge amount small), '2' indicates medium dot discharge (medium discharge amount), and '3' indicates large Represents dot ejection (large ejection volume). The number of gradation values for quantization is set according to the specifications of the treatment liquid head 34T, the ink heads 34Y, 34M, 34C, 34K, the drive circuit, and the like. For example, when dot ejection control is performed in three stages (no dot ejection / small dot ejection / large dot ejection), the value is set to 3 values.

  In the present embodiment, for each color of K, M, C, and Y, using an error diffusion method that diffuses a quantization error caused by quantization by comparison between image data and a threshold value to surrounding pixels. Then, a process of converting 8-bit data into 2-bit data is performed.

  First, the quantization threshold will be described with reference to FIG. FIG. 5 shows threshold values in the case of quantizing 256 gradation image data of 0 to 255 into four values of large dot discharge, medium dot discharge, small dot discharge, and no dot discharge.

  As shown in FIG. 5, in the present embodiment, for example, three threshold values, a large dot discharge threshold value 208, a medium dot discharge threshold value 128, and a small dot discharge threshold value 48 are set. The system controller 60 quantizes the 8-bit gradation value by comparing each threshold value with the 8-bit gradation value of each pixel. That is, when the gradation value is 0 or more and 48 or less, it is converted to “0 (no liquid discharge)”, and when it is 49 or more and 128 or less, it is converted to “96 (small dot discharge)”. In the following cases, it is converted to “160 (medium dot discharge)”, and in the case of 209 or more, it is converted to “255 (large dot discharge)”.

  Next, error diffusion processing will be described.

  The quantization error U of the pixel g (x, y) to be processed is expressed by the following equation (1).

U = (Q + R) -S (1)
In addition,
Q: gradation value before quantization of pixel g (x, y) (0 to 255)
R: Sum of quantization errors diffused from neighboring pixels by error diffusion S: Output value

  The output value is a gradation value after quantization. In the present embodiment, “0” indicates no dot discharge, “96” indicates small dot discharge, “160” indicates medium dot discharge, and “255” indicates large dot discharge. 'And.

  FIG. 6 shows an example of the quantization error U diffusion process. In the figure, a pixel g indicated by a bold frame is a target pixel g (x, y), and a pixel indicated by hatching is an already quantized pixel. The numerical values in the frame indicating the pixels g other than these indicate the diffusion ratio when the quantization error U of the pixel of interest g (x, y) is diffused to the peripheral pixels.

  That is, by diffusion processing, 7/16 of the quantization error U of the pixel of interest g (x, y) becomes g (x, y + 1) to be subjected to the next quantization processing, and 5/16 of the quantization error U becomes The pixel g (x + 1, y) and the pixel g (x + 1, y) that are respectively diffused to the pixel g (x + 1, y) adjacent to the pixel of interest and are adjacent to the diagonal position of the pixel of interest are quantized errors. 3/16 and 1/16 of U are diffused.

  As shown in FIG. 4, the quantization using the above-described error diffusion method is first performed on 2 bits of the reference K color.

  Next, quantization M using the error diffusion method is performed on the M colors. At this time, the ink of K color is ejected, that is, for any pixel whose K color gradation value is 1 to 3, the threshold value for ejecting small dots is set to 48 as shown by the dotted frame in FIG. Pull down to 8.

  Next, quantization C using the error diffusion method is performed on the C color. At this time, at least one ink of K color and M color is ejected, that is, the threshold value of small dot ejection is set for any pixel whose gradation value is at least one of K color and M color. Pull down from 48 to 8.

  Next, quantization Y using the error diffusion method is performed on the Y color. At this time, at least one ink of K color, M color, and C color is ejected, that is, for any pixel in which the gradation value of at least one of K color, M color, and C color is 1 to 3. Reduces the threshold for small dot ejection from 48 to 8.

  Note that the order of M, C, and Y is not limited to the order described above. Further, the present invention can be implemented without using the K color as a reference.

  Further, in the error diffusion method, the pixel value obtained by changing the threshold value for each pixel propagates to surrounding pixel values, so that the balance of gradation values is not lost in the entire image data.

  Next, referring to FIG. 7A, the gradation value (T value) of T represented by 2 bits is obtained from the gradation values of K, M, C, and Y represented by 2 bits. The required processing will be described.

  First, T calculation processing for obtaining a T value represented by 8 bits from the gradation values of K, M, C, and Y represented by 2 bits is performed for each pixel.

  In the T value calculation process, an 8-bit T value is obtained using the following equation (2).

T = 255 × W (n) × n (2)
In addition,
W (n): Weight n: Number of colors ejecting dots (0 to 4)
W (n) is determined so as to decrease exponentially as n increases, as shown in FIG. 7B.

  In addition, n is obtained by counting the number of colors discharged from the dots regardless of the amount of liquid of large dots, medium dots, and small dots. Specifically, it is obtained by calculating the logical sum of the first bit value and the second bit value of the 2-bit gradation value of each color.

  In the present embodiment, the values shown in Table 1 below are used.

  That is, the T value when n is “0” is “0”, the T value when n is “1” is “63”, the T value when n is “2” is “112”, and n is “ The T value when “3” is “138”, and the T value when “n” is “4” is “153”.

  In this way, in a pixel from which one color of ink is ejected, the T value, that is, the appropriate amount of processing liquid, is constant regardless of whether the dot is a large dot, a medium dot, or a small dot. As the appropriate amount of liquid increases, the ratio of processing liquid to ink decreases. That is, for each pixel, the ratio of the droplet amount of the processing liquid to the appropriate amount of ink liquid is adjusted so as to decrease as the appropriate amount of ink liquid increases.

  Note that the method of obtaining the 8-bit T value is not limited to the above-described method, and any value from 0 to 255 corresponding to the appropriate amount of ink liquid may be obtained.

  Next, a quantization process for converting (quantizing) an 8-bit T value into a 2-bit T value is performed using an error diffusion method.

  Similar to the description with reference to FIGS. 5 and 6 described above, in the present embodiment, for example, three threshold values of a large dot discharge threshold value 208, a medium dot discharge threshold value 128, and a small dot discharge threshold value 48, and an 8-bit value of each pixel. By performing a comparison process with the T value and an error diffusion process, the T value is quantized into four values to obtain a 2-bit T value.

  As a result, even when only one pixel from which a single small color dot is ejected is isolated, the treatment liquid is ejected.

  In this way, by reducing the threshold value used for quantization of the gradation value of each color in pixels where ink of other colors is ejected, a plurality of colors can be applied to the same pixel, particularly in a highlight area where the ink ejection amount is small. The probability that ink is ejected can be increased.

Moreover, by calculating | requiring weighting and calculating | requiring the discharge amount of a process liquid, the discharge amount of a process liquid can be made into the quantity which was sufficient for reaction and suppressed.
(Second Embodiment)
Next, image processing according to the second embodiment of the present invention will be described.

  In the first embodiment, the case of performing quantization using the error diffusion method has been described, but in the second embodiment, a dot concentration type dither in which thresholds are arranged so that the dots are thick from the center of the matrix. A case where quantization is performed using a halftone screen which is a matrix will be described. In the following, description of portions corresponding to those of the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

  A second embodiment of the image processing performed by the system controller 60 will be described with reference to FIGS.

  The flow of image processing will be described with reference to FIG.

  First, for example, original data of an image to be recorded in which 256 gradation values from 0 to 255 are represented using 8 bits for each gradation value of R, G, and B colors of each pixel is input.

  The system controller 60 performs resolution conversion and color conversion processing on the input original data to obtain data for each pixel represented by 8-bit K, M, C, and Y gradation values.

  Next, the system controller 60 converts each pixel data represented by 8-bit K, M, C, Y gradation values into 1-bit K, M, C, Y gradation values. Is converted (quantized) into data represented by. The 1-bit gradation value represents one of “0” and “1”. '0' represents no dot ejection, and '1' represents dot ejection. Note that the gradation value may be represented by 2 bits, and the number of values in this case is four.

  In this embodiment, 8-bit data is converted into 1-bit data for each color of K, M, C, and Y by using a halftone screen.

  The halftone screen is a threshold value matrix having a characteristic of excellent gradation reproducibility and a characteristic of concentrating pixels to be ejected with ink.

  FIG. 9 shows an example of a halftone screen. In the present embodiment, the halftone screen uses a threshold matrix in which elements of 100 different values are arranged.

  In the quantization processing in the present embodiment, each color is divided into blocks of 10 × 10 pixels, and the corresponding halftone screen elements and gradation values are compared and binarized in units of blocks. . Binarization is performed by setting “1” when the gradation value is equal to or greater than the element value, and setting it to “0” when the gradation value is less than the element value.

  Since the number of elements of the halftone screen is 10 × 10 and the number of gradations is 256, the division processing for dividing the gradation value by 2.55 or the element value of the halftone screen is 2.55. Quantization is performed after a multiplication process is performed.

  Further, T calculation processing is performed for obtaining a gradation value (T value) of T represented by 8 bits from each gradation value of K, M, C, and Y represented by 8 bits.

  In the T calculation process, first, 256 T values are obtained according to the following equation (3).

T = W (Σ) × Σ (3)
In addition,
W (Σ): Weight Σ: The sum of the gradation values of K, M, C, and Y. W (Σ) decreases exponentially as Σ increases as shown in FIG. Determine as follows. That is, for each pixel, the ratio of the droplet amount of the treatment liquid to the appropriate amount of ink liquid can be adjusted so as to decrease as the appropriate amount of ink liquid increases.

  Next, as shown in FIG. 10B, the value in the range of 1 to 5% when the maximum value of W (Σ) × Σ can be taken as 100% is uniformly converted to a value of 5%. At the same time, the gradation value in the high percentage range is converted into a predetermined value.

  Next, by using a halftone screen, 8-bit T-value data is binarized and converted to 1-bit data. By performing the process of converting to the uniform value of 5%, there is a high probability that the value of a pixel having a small gradation value is converted to “1”.

  For example, when the gradation value of each pixel of a 10 × 10 pixel block is 1% when the maximum value of W (Σ) × Σ can be taken as 100%, it is uniformly 5%. FIG. 11A shows the result of binarization when the process of converting to the value is not performed. A colored pixel indicates a pixel having a T value of “1”, and a colorless pixel indicates a pixel having a T value of “0”.

  On the other hand, when the process of uniformly converting the value to 5% is performed, the result shown in FIG. 11B is obtained.

  In this way, by using a halftone screen to quantize the gradation values of each color, it is possible to increase the probability that a plurality of colors of ink are ejected to the same pixel, particularly in a highlight area where the amount of ink ejection is small. Can do.

  In addition, using a halftone screen to quantize the discharge amount of the processing liquid and raising a small value in a predetermined range to a predetermined value, it is sufficient even for pixel positions in highlight areas where the ink discharge amount is small. The amount of treatment liquid that causes a reaction can be discharged.

Further, by lowering a large value in the predetermined range to a predetermined value, the discharge amount of the processing liquid can be made an amount sufficient for the reaction and suppressed.
(Third embodiment)
Next, image processing according to the third embodiment of the present invention will be described.

  In the second embodiment, the case where the tone value and T value of each color are obtained by using a common halftone screen has been described. However, in the third embodiment, the tone value and T value of each color are obtained. Will be described using different halftone screens. In the following, description of portions corresponding to the second embodiment will be omitted, and differences from the second embodiment will be mainly described.

  With reference to FIGS. 12 to 14, a third embodiment of the image processing performed by the system controller 60 will be described.

  The flow of image processing will be described with reference to FIG.

  First, for example, original data of an image to be recorded in which 256 gradation values from 0 to 255 are represented using 8 bits for each gradation value of R, G, and B colors of each pixel is input.

  The system controller 60 performs resolution conversion and color conversion processing on the input original data to obtain data for each pixel represented by 8-bit K, M, C, and Y gradation values.

  Next, the system controller 60 converts each pixel data represented by 8-bit K, M, C, Y gradation values into 1-bit K, M, C, Y gradation values. Is converted (quantized) into data represented by.

  In the present embodiment, 8-bit data is converted into 1-bit data by using different dither matrices for K, M, C, and Y colors.

  For the quantization of each of K, M, C, and Y, a dither matrix as shown in FIGS. 13A and 13B is used. That is, the dither matrix set so that the values of the four central elements are the same is used. By using such a dither matrix, dots of a plurality of colors are ejected from the same pixel, particularly in a pixel having a small highlight gradation value in each color.

  When the dither matrix shown in FIGS. 13A and 13B is used, the number of elements is 4 × 4. Therefore, the division processing for dividing the gradation value by 16 or the halftone dot screen element value of 16 is used. Quantization is performed after a multiplication process is performed.

  Further, T calculation processing is performed for obtaining a gradation value (T value) of T represented by 8 bits from each gradation value of K, M, C, and Y represented by 8 bits.

  In the T calculation process, 256 T values are obtained according to the above equation (3). That is, for each pixel, the ratio of the droplet amount of the treatment liquid to the appropriate amount of ink liquid can be adjusted so as to decrease as the appropriate amount of ink liquid increases.

  Next, by using a dither matrix as shown in FIG. 13C, 8-bit T value data is converted into 1-bit data. As shown in FIG. 13C, the dither matrix used for binarization of the T value sets the values of the central four elements to “1”. By setting the values of the central four elements to “1”, it is possible to increase the probability that the value of a pixel having a small gradation value is converted to “1”.

  FIG. 14 shows an example of a dither matrix having 8 × 8 elements that can be used in the present embodiment. For example, the K color gradation value is binarized by the dither matrix of FIG. 10A, the M color gradation value is binarized by the dither matrix of FIG. Then, the gradation value of the C color is binarized, the gradation value of the Y color is binarized by the dither matrix of FIG. 4D, and the T value is binarized by the dither matrix of FIG.

  When the dither matrix shown in FIG. 14 is used, since the number of elements is 8 × 8, division processing for dividing the gradation value by 4 or multiplication processing for multiplying the element value of the halftone screen by 4 is performed. Quantize from

  In this way, the value of the element located at the center of the dither matrix used for quantization of the tone value of each color is set to be small, and the value of the element located at the center of the dither matrix used for quantization of the tone value of each color is set. Is set to be the same, it is possible to increase the probability that inks of a plurality of colors are ejected to the same pixel, particularly in a highlight region where the ink ejection amount is small.

  Furthermore, by setting the value of the element located at the center of the dither matrix used for quantization of the discharge amount of the processing liquid to “1”, the pixel position in the highlight area where the ink discharge amount is small is sufficient. An amount of treatment liquid that causes a reaction can be discharged.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment. 1 is a schematic configuration diagram of an inkjet printer according to an embodiment. 2 is a conceptual diagram of image data G. FIG. It is a figure which shows the flow of the image processing in 1st Embodiment. It is a figure explaining the threshold value of quantization. 6 is a diagram illustrating an example of a quantization error U diffusion process. FIG. (A) is a figure explaining the process which calculates | requires the gradation value of T, (B) is a conceptual diagram of a weight. It is a figure which shows the flow of the image processing in 2nd Embodiment. It is a figure which shows an example of a halftone screen. (A) is a conceptual diagram of weights, and (B) is a conceptual diagram of conversion of T gradation values. (A) shows the result when the conversion of FIG. 10 (B) is not performed, and (B) shows the result when the conversion of FIG. 10 (B) is performed. It is a figure which shows the flow of the image processing in 3rd Embodiment. An example of a 4 × 4 dither matrix is shown. An example of an 8 × 8 dither matrix is shown.

Explanation of symbols

10 Inkjet printer 34 Inkjet recording head 60 System controller

Claims (4)

Each gradation value of a plurality of different colors of each pixel is quantized to an N value (N is an integer of 3 or more) so that a plurality of liquid droplets are overlapped , and N for each of the plurality of different colors. Discharge data creating means for creating discharge data for discharging droplets at a stage discharge amount ;
The amount of the processing liquid that agglomerates the color material by being mixed with the liquid droplets for each pixel is the amount of each of the plurality of colors that is discharged to each pixel based on the discharge data for each color. irrespective of the ejection amount of droplets, said enough small Kunar so many number of colors of liquid droplets ejected to each pixel, the processing liquid data generating means for generating the processing liquid data for ejecting the treatment liquid,
An image processing apparatus. The ejection data creation means performs quantization by an error diffusion method and at least 1
A pull-down unit that lowers only a minimum threshold value among (N-1) threshold values to be compared with a gradation value of a color other than the at least one color of a pixel from which a droplet of one color is discharged; The image processing apparatus according to claim 1. The image processing apparatus according to claim 1 or 2 ,
First ejection means for ejecting droplets of each of the plurality of colors onto a recording medium based on the ejection data created by the ejection data creating means;
Second discharge means for discharging the treatment liquid onto the recording medium based on the treatment liquid data created by the treatment liquid data creation means;
An image recording apparatus comprising: On the computer,
Each gradation value of a plurality of different colors of each pixel is quantized to an N value (N is an integer of 3 or more) so that a plurality of liquid droplets are overlapped , and N for each of the plurality of different colors. Creating ejection data for ejecting droplets at a staged ejection volume ;
The amount of the processing liquid that agglomerates the color material by being mixed with the liquid droplets for each pixel is the amount of each of the plurality of colors that is discharged to each pixel based on the discharge data for each color. irrespective of the ejection amount of droplets, said enough small Kunar so many number of colors of liquid droplets ejected to each pixel, creating a processing liquid data for ejecting the treatment liquid,
A program for running

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