JP4032676B2 - Image recording method, image recording apparatus to which the image recording method is applied, and image recording processing program applied to the image recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly prints and records an image on a recording medium in multiple gradations after forming two or more types of dots having different densities per unit area by combining area gradation, density gradation, or a combination of both. The present invention relates to an image recording method, an image recording apparatus to which the image recording method is applied, and an image recording processing program applied to the image recording apparatus.
[0002]
[Prior art]
Conventionally, a digital color image is composed of a set of pixels constituting the image, and each pixel is expressed by a three-dimensional value indicating a color space. A color space generally used is an RGB space composed of red (R), green (G), and blue (B). In this RGB space, each pixel is provided by a combination of R, G, and B components or a combination of R, G, and B vectors having a predetermined size, and by combining the R, G, and B components. Pixels having a specific color can be formed. In the case of a digital color image, it is usually composed of 8-bit information per pixel and one numerical value of 256 gradation values that is the power of 2 is assigned. Specifically, from 0 to 255 is assigned. It has one numerical value selected from the numerical values.
[0003]
As one of such digital color image output devices (printing devices), a color ink jet printer having a plurality of different color inks has been developed and widely used for printing and recording images. Such an ink jet printer is a system that prints and records an image on a recording medium such as paper using a set of ink dots ejected from a plurality of nozzles provided in the head. Therefore, basically, only two gradation information can be adopted.
[0004]
Therefore, in recent color ink jet printers, the density per unit area can be reduced by combining area gradation that changes the size of dots for each single color, density gradation that uses inks with different densities, or a combination of both. By making it possible to form two or more different types of dots, it is possible to express information of three or more gradations functionally. Even in such a printer, 256 gradations that the original image information has Since the value data cannot be directly expressed, generally, the image data having 256 gradation values in each hue for each pixel is quantized from the output evaluation value set according to the number of gradations that can be expressed by the printer. The process to turn into.
[0005]
The image data quantized to the number of gradations that can be expressed by the printer in this way is converted into data that can be processed by the printer and then transferred to the printer, and the printer prints and records it on a recording medium such as paper according to the transferred data. I do.
[0006]
Incidentally, as a known technique related to such a printing method, a printer, and a printing apparatus, a printing apparatus, a printing method, a recording medium, and a recording medium disclosed in Japanese Patent Laid-Open Nos. 11-151821 and 11-254661 are disclosed. Examples thereof include a printing apparatus and a recording medium disclosed in Japanese Patent No. 79710, an ink jet printer disclosed in Japanese Patent Laid-Open No. 2000-190470, a printing apparatus, a printing method, and a printer disclosed in Japanese Patent Laid-Open No. 2000-225716.
[0007]
[Problems to be solved by the invention]
In the case of the above-described conventional color ink jet printer, a difference in the nozzle characteristics of the head, an error in the transport control mechanism when feeding a recording medium such as paper, or a cartridge filled with ink is mounted in the process until print recording is performed. Due to fluctuations in the movement of the carriage, differences in ink characteristics, etc., the positions of the dots that land on the recording medium may be misaligned without being regularly arranged. Appearing as a darker streak than the surrounding area, or on the contrary, the area where no ink is applied from the unexpected way of separating the dots and the white on the paper appears continuously. There is a problem that so-called banding that appears as white stripes occurs, degrading the image quality of the printed and recorded image.
[0008]
In order to reduce such banding, improvement can be expected to some extent by improving the accuracy of various control mechanisms and components in the printer or the accuracy of the ejection direction of the head. This is not preferable because the size is increased or the price is increased. Therefore, in the process of quantizing the 256 gradation values of the original image data into the number of gradations that can be expressed by the printer, it is inexpensive if the influence of the disturbance of the dots that land on the recording medium such as paper can be reduced. However, at present, no technical proposal has been made to improve such quantization processing.
[0009]
The present invention has been made to solve such problems, and its technical problem is to reduce banding that causes image quality degradation of images printed and recorded with multiple gradations per color, and to achieve high-quality printing. An object is to provide an image recording method capable of recording, an image recording apparatus to which the image recording method is applied, and an image recording processing program applied to the image recording apparatus.
[0010]
[Means for Solving the Problems]
According to the present invention, an area gradation that changes the size of each dot in a single color, a density gradation that uses inks of different densities, or a unit area by combining both the area gradation and the density gradation. Image data input for inputting image data having a predetermined gradation value in each hue for each pixel as input data applied to a printing apparatus including a head capable of forming two or more types of dots having different per-density A processing stage, an image data conversion process stage that converts image data input in the image data input process stage into data that can be processed by the printing apparatus, and an image data converted in the image data conversion process stage is expressed by the printing apparatus. A quantization process stage that quantizes the output evaluation value set according to the number of possible gradations, and prints and records the image data quantized in the quantization process stage on a recording medium In the image recording method including the print recording process step, the high frequency component in the direction in which banding occurs without forming all the pixels with only one type of dots that can be formed by the head at the quantization process step. An image recording method can be obtained in which quantization is performed according to a rule that is larger than the low frequency component.
[0011]
According to the present invention, in the image recording method, the quantization is performed by applying quantization to at least one type of dots excluding the highest density dot among the dots that can be formed by the head. A recording method is obtained.
[0012]
Furthermore, according to the present invention, in any one of the above image recording methods, in the quantization processing stage, at least two types of image recording are performed without performing the same quantization for all inks corresponding to different hues. A method is obtained.
[0013]
In addition, according to the present invention, in any one of the above-described image recording methods, an image recording method can be obtained in which quantization is performed using a two-dimensional matrix capable of executing rules.
[0014]
In any one of these image recording methods, in the quantization processing stage, an image is obtained by diffusing a quantization error indicated by a difference between a gradation value and an output evaluation value in image data generated by quantization to surrounding pixels. It is preferable to maintain the overall concentration.
[0015]
On the other hand, according to the present invention, an area gradation that changes the size of each dot in a single color, a density gradation that uses inks having different densities, or a combination of both the area gradation and the density gradation. A printing apparatus having a head capable of forming two or more types of dots having different densities per unit area; image data input means for inputting image data having a predetermined gradation value in each hue for each pixel; and image data Data conversion means for converting the image data into data that can be processed by the printing apparatus, and the image data converted by the image data conversion means is not composed of all pixels with only one kind of dots that can be formed by the head Output rating that is set according to the number of gradations that can be expressed by the printing device in accordance with a rule such that the high frequency component in the direction in which banding occurs is greater than the low frequency component. And a computer having a quantizing means for quantizing to a value, the printing apparatus, an image recording device can be obtained that acts as a print recording means for printing recording image data quantized by the quantization means to the recording medium.
[0016]
According to the present invention, in the image recording apparatus, the quantization means applies the quantization to at least one kind of dots excluding the dot having the highest density among the dots that can be formed by the head. A device is obtained.
[0017]
Furthermore, according to the present invention, in any one of the above image recording apparatuses, the quantization unit prepares at least two types of quantization without performing the same for all inks corresponding to different hues. Is obtained.
[0018]
In addition, according to the present invention, in any one of the above image recording apparatuses, the quantization means can obtain an image recording apparatus that performs quantization using a two-dimensional matrix capable of executing a rule.
[0019]
In any one of these image recording methods, the quantization means diffuses the quantization error indicated by the difference between the gradation value and the output evaluation value in the image data generated by the quantization to the peripheral pixels. It is preferable to maintain the concentration of
[0020]
On the other hand, according to the present invention, an area gradation that changes the size of each dot in a single color, a density gradation that uses inks having different densities, or a combination of both the area gradation and the density gradation. An image for inputting image data having a predetermined gradation value in each hue for each pixel as input data applied to a printing apparatus including a head capable of forming two or more types of dots having different densities per unit area Data input processing, image data conversion processing that converts image data input in the image data input processing into data that can be processed by the printing device, and dots that can be formed by the head in the image data converted in the image data conversion processing In accordance with the rule that the high frequency component in the direction in which banding occurs without forming all the pixels with only one type of dot is greater than the low frequency component Quantization processing to quantize to output evaluation values set according to the number of gradations that can be expressed by the printing device, and image data quantized by the quantization processing is transferred to the printing device and printed and recorded on a recording medium Thus, an image recording processing program that enables the computer to execute the print recording processing for causing the recording to be performed is obtained.
[0021]
According to the invention, in the image recording processing program, the quantization processing is performed by applying quantization to at least one kind of dots excluding the highest density dot among the dots that can be formed by the head. An image recording processing program including the contents is obtained.
[0022]
Furthermore, according to the present invention, in any one of the above-described image recording processing programs, the quantization processing is performed by preparing at least two types without performing the same quantization for all inks corresponding to different hues. Can be obtained.
[0023]
In addition, according to the present invention, in any one of the above-described programs for image recording processing, the quantization processing is for image recording processing that includes content that is performed using a two-dimensional matrix that can execute a rule. A program is obtained.
[0024]
In any one of these image recording processing programs, the quantization processing is performed by diffusing the quantization error indicated by the difference between the gradation value and the output evaluation value in the image data generated by the quantization to surrounding pixels. It is preferable to include contents that maintain the density of the entire image.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Several embodiments will be described below, and an image recording method of the present invention, an image recording apparatus to which the image recording method is applied, and an image recording processing program applied to the image recording apparatus will be described in detail with reference to the drawings. .
[0026]
First, a technical outline of the image recording method of the present invention will be briefly described. In this image recording method, an area gradation that changes the size of each dot in a single color, a density gradation that uses inks having different densities, or a unit area by combining both of these area gradations and density gradations. Image data having a predetermined gradation value (256 gradation values) in each hue for each pixel as input data applied to a printing apparatus including a head capable of forming two or more types of dots with different per-density The image data input processing stage for inputting the image data, the image data conversion processing stage for converting the image data input in the image data input processing stage into data that can be processed by the printing apparatus, and the data conversion in the image data conversion processing stage A quantization process stage that quantizes the output image data to an output evaluation value that is set according to the number of gradations that can be expressed by the printing device, and the quantization process stage In an existing image recording method having a print recording process step of printing and recording the recorded image data on a recording medium, at the quantization process step, all pixels are configured by only one type of dots that can be formed by the head. Instead, quantization is performed according to a rule such that the high frequency component in the direction in which banding occurs is larger than the low frequency component.
[0027]
According to such an image recording method, since all pixels (images) are not composed of only one type of dot, high density dots and low density dots coexist. In the case of area gradation, since a dot having a high density is a single dot and the area on which ink is placed on the recording medium is wide, even if the adjacent dots are separated from the disorder of the dots that land on the recording medium, the ink does not get on. The area can be small, and this can prevent banding that appears due to the continuous generation of areas not carrying ink. Normally, banding appears in the reciprocating direction of the head, and if pixels that do not always place dots in the pixels in the reciprocating direction of the head are regularly inserted, even if the position where the dots land on the recording medium is shifted, the shifted position Then there is a high possibility that dots are not placed. Conventionally, banding has been caused by the distance between adjacent dots becoming larger due to the displacement of dot landing positions, or by overlapping adjacent dots. Pixels that do not form dots like the image recording method here If it is created regularly, it will be difficult to overlap with adjacent dots, and this has the effect of reducing banding. As for the regularity in the image recording method here, it is desirable to increase the high frequency component in a direction close to the direction parallel to the banding. This is because human vision is less sensitive to high frequency components than it is to low frequency components. Incidentally, in order to keep the density in the image recording area constant, as a result, the low frequency component becomes larger in the direction perpendicular to the direction in which banding occurs.
[0028]
By the way, in the above-described image recording method, in the quantization processing stage, quantization is applied to at least one kind of dots excluding the highest density dot among the dots that can be formed by the head, and the highest density dot. If the quantization is not limited, the color space that can be expressed in the entire image can be widened, and high image quality can be realized.
[0029]
In any of the image recording methods described above, at the quantization step, at least two types of quantization are prepared without performing the same for all inks corresponding to different hues (depending on the type of ink). If the quantization is changed), even in a pixel in which dots are not formed with a certain ink color, dots of other ink colors are formed, so the area not covered with ink is reduced, and this makes white fine Muscle banding is less likely to occur.
[0030]
Further, in any one of the image recording methods described above, if the quantization is performed using a two-dimensional matrix capable of executing a rule in the quantization processing stage, the two-dimensional matrix is set to have a high frequency component. If this is the case, perceived patterns are less likely to occur. Creation of such a two-dimensional matrix requires a lot of man-hours, but once it is created, high-speed and high-quality output can be obtained.
[0031]
In addition, in any one of the image recording methods described above, in the quantization processing stage, a quantization error indicated by the difference between the gradation value and the output evaluation value in the image data generated by the quantization is diffused to surrounding pixels. If the density of the entire image is maintained by this, when a pixel whose quantization error increases due to the regularity of the dot arrangement occurs, the density is kept constant by diffusing the quantization error to surrounding pixels. Will be able to keep.
[0032]
FIG. 1 is a functional block diagram showing a basic configuration of an image recording apparatus according to Embodiment 1 to which this image recording method is applied. This image recording apparatus has an area gradation that changes the size of each dot in a single color, a density gradation that uses inks having different densities, or a unit area by combining both the area gradation and the density gradation. An output device 21 including a printer 22 as a printing apparatus having a head capable of forming two or more types of dots having different hit densities and image data having a predetermined gradation value in each hue for each pixel are input. Various data between the input device 20 having the image data input means, a storage device (not shown) for storing various data, a communication device (not shown) for communicating various data, and various devices including the input device 20 And an input interface 11 that exchanges data and an output interface 12 that exchanges various data with various devices including the output device 21. In addition, image data conversion means for converting the input image data into data that can be processed by the printer 22, and only one type of dots that can be formed by the head from the image data converted by the image data conversion means. Quantize the output evaluation value set according to the number of gradations that can be expressed by the printer 22 in accordance with a rule such that the high frequency component in the direction in which banding occurs without configuring all pixels is greater than the low frequency component. And a computer 10 having a control / arithmetic mechanism 13 for performing various processes relating to printing and recording, including a function as a quantizing unit. The printer 22 is quantized by the quantizing unit of the control / arithmetic mechanism 13. The entire system is configured as a printing system so as to function as a printing recording unit that prints and records the image data on a recording medium such as paper.
[0033]
FIG. 2 is a functional block diagram schematically showing the processing contents of the software program applied to the computer 10 provided in the image recording apparatus in a functional manner. This software program is constructed as an image recording processing program of various forms applied to the computer 10, and here, in the printer driver 48 in response to a print recording request by the application program 41 via the output interface 12. After inputting image data, the printer 22 converts the data into a data format that can be printed and output, and then a function of transmitting the data to the printer 22 through quantization is constructed.
[0034]
That is, the printer driver 48 here is an image data input process for inputting image data having a predetermined gradation value (256 gradation values) at each hue for each pixel, and an image input by the image data input process. Image data conversion processing for converting data into data that can be processed by the printer, and image data converted by the image data conversion processing without constituting all pixels with only one type of dots that can be formed by the head Quantization processing that quantizes the output evaluation value that is set according to the number of gradations that can be expressed by the printer according to the rule that the high frequency component in the banding direction is larger than the low frequency component, and the quantization It is responsible for print recording processing for transferring the image data quantized by the processing to the printer 22 and printing and recording it on a recording medium.
[0035]
More specifically, when the printer driver 48 receives data from the application program 41, the image having a predetermined gradation value (256 gradation values) in each hue for each pixel from the input device 20 via the input interface 12. After performing image data input processing for inputting data, image data conversion processing is performed on the input image data. In the image data conversion process, the resolution conversion module 42 is first driven to perform conversion to a resolution that can be output by the printer 22, and then the color conversion module 43 is driven to perform color conversion of the image data according to the color conversion table 44. Do. The color conversion table 44 is separately created and stored in advance so that the color characteristics created by the image data match the color characteristics expressed by the printer 22. For example, each of cyan (C), magenta (M), yellow (Y), and black (K) that the printer 22 constitutes image data having color configurations of red (R), green (G), and blue (b). There is a case where data is converted into data that can be expressed by a combination of inks.
[0036]
Next, in the printer driver 48, after the quantization module 45 plays a role of quantizing the resolution-converted and color-converted image data into the number of gradations (quantum number) that can be expressed by the printer 22, the rasterizer 46 performs the quantization. It plays a role of replacing the converted image data with data to be transferred to the printer 22, whereby printable and recordable image data is transferred to the printer 22, and the printer 22 prints and records the image data on a recording medium such as paper. To do.
[0037]
FIG. 3 is a schematic diagram showing the main configuration of the printer 22 provided in the image recording apparatus. The printer 22 includes an operation panel 50 provided with operation buttons for an operator to give an operation instruction, a control circuit 51 for performing various controls in each unit in the apparatus in accordance with the operation instruction from the operation panel 50, a carriage motor 52, a drive mechanism for moving the carriage 67 in the axial direction of the platen 60, a transport mechanism for transporting the recording medium 61 by the paper feed motor 62, and a print head 59 disposed on the carriage 67 to drive the ink. And a printing mechanism for discharging and forming dots.
[0038]
Among these, the drive mechanism includes a shaft 56 provided in parallel to the axis of the platen 60 to support the movement of the carriage 67, a pulley 55 for tensioning the drive belt 53 between the carriage motor 52, and the origin of the carriage 67. It is comprised from the position detection sensor 54 etc. for detecting. The printing mechanism also includes a black ink cartridge 58 and a color ink cartridge 57 (colors are cyan (C), magenta (M), and yellow (Y)) provided on the carriage 67. In addition, the print head 59 provided on the carriage 67 is provided with a black ink head 66 and three-color heads 63 to 65 for each color ink.
[0039]
FIG. 4 is a perspective view schematically showing the detailed configuration of the print head 59 provided in the printer 22 described above. However, for the sake of simplicity, only the mechanism portion for ejecting one color is shown here. However, the mechanism portion is actually applied to the heads 63 to 66 arranged in parallel for each color ink. .
[0040]
The print head 59 has a plurality of nozzles 70 each provided with a piezoelectric element 68 having a property of changing its shape when a voltage is applied, and ink is supplied from the cartridge 57 or the cartridge 58 through the ink supply path 69. When ink is ejected from the nozzle 70 by changing the shape of the piezoelectric element 68 under the supplied conditions, dots can be formed. Here, the size of the dots can be controlled by controlling the shape change of the piezoelectric element 68, and a color image can be formed on the recording medium 61 by forming dots for each color. .
[0041]
Here, the case where the print head 59 has a mechanism for ejecting ink from the nozzles 70 using the piezoelectric elements 68 as the printer 22 has been described. However, a printer 22 that ejects ink by other methods is used. May be. For example, a type in which ink is ejected by bubbles generated in the vicinity of the nozzle is also applicable. Here, the gradation is acquired based on the size of the ejected dots, but any type of gradation may be applied as long as the density per unit area changes. For example, the present invention can be applied to a type that obtains gradation by changing the ink density.
[0042]
FIG. 5 is a flowchart showing a quantized data creation processing routine performed by the control / calculator 13 provided in the image recording apparatus. This quantized data creation process routine is a process for creating multi-value quantized data for enabling printing and recording of image data input by the printer 22. When the control / calculator 13 starts its operation, The original data input process (step S10) is performed on the input image data. The original data has 256 gradation values from 0 to 255 for each color of R, G, and B in each pixel. Note that the resolution of the original data is arbitrary.
[0043]
Next, the control / calculator 13 performs resolution conversion (step S11) for enabling the printer 22 to print and record the resolution of the input image data. Note that this resolution conversion process (step S11) is not necessarily executed, but is changed so as to execute printing and recording by jumping according to the user's request or the resolution of the input image data itself. It doesn't matter.
[0044]
Further, the controller / arithmetic unit 13 performs color conversion (step S12). The color conversion process is a process of converting image data composed of three colors R, G, and B into C, M, Y, and K data. This color conversion processing is performed using the color conversion table (LUT) 44 that stores combinations according to the C, M, Y, and K characteristics of the printer 22 as described above.
[0045]
Generally, the number of gradations that can be expressed by the printer 22 is smaller than the gradation value that the original data has. For example, the number of gradations of original data represented by a Bmp file is 256 gradation values per color, whereas the number of gradations that can be expressed by the printer 22 is often less than 10 gradations. .
[0046]
For this reason, the control / calculator 13 quantizes the image data that has undergone the color conversion (step S12) to reduce the number of gradations of the original data to the number of gradations that can be expressed by the printer 22 (step S13). Perform the process. Here, it is assumed that quantization is performed from four types of gradation values 256 of the original data to four types of gradation numbers that can be expressed by the printer 22. Incidentally, the four types of gradations that can be expressed by the printer 22 are “dot non-formation (no droplet)”, “small droplet formation”, “medium droplet formation”, and “large droplet formation”. . Of course, the four gradations that can be expressed by the printer 22 are “dot non-formation (no drops)”, “low density ink formation”, “medium density ink formation”, and “high density ink formation”. It may be executed by using different ink densities, or may be executed by a combination of dot size and ink density.
[0047]
By the way, when the controller / arithmetic unit 13 performs the quantization process (step S13) on all the C, M, Y, and K image data created by the color conversion process (step S12). Subsequently, it is determined whether or not all colors are finished (step S14). As a result, if all colors are not finished, the process returns to the quantization (step S12) and the quantization is repeated. When the end of color is reached, the quantized data creation routine is terminated.
[0048]
In this way, the quantized image data of all colors is finally converted into a data format that can be processed by the printer 22 by the control / calculator 13, and then transferred to the printer 22 via the output interface 12. .
[0049]
Hereinafter, the quantization processing that is a feature of the present invention will be described in more detail. Note that the types of dots formed in each color are three types, large droplets, medium droplets, and small droplets. However, the types of dots formed in these colors are dots if the density per unit area is different. This may be realized by the size of the ink, may be realized by the ink density, or may be realized in a mixed form.
[0050]
Here, in order to facilitate the explanation of the quantization process, the concept of group 1 and group 2 is used, the reciprocating direction of the print head 59 is set as the X direction, and the start position of the reciprocating motion of the print head 59 is set as the origin. When the coordinate in the X direction in the image is x, a continuous n pixel in the X direction is considered as one unit, and a group 1 of m pixels in each unit of n pixels in which one unit of n pixels is continuously repeated. Assume an operation of dividing into a group 2 of remaining (nm) pixels. Here, the method of selecting m pixels may be such that m pixels are continuous, have periodicity, or are random.
[0051]
FIG. 6 is a flowchart showing detailed operation processing (quantization routine) of the quantization processing.
[0052]
In the case of this quantization routine, it is performed by the control / calculation unit 13 in the computer 10, and when the operation process is started, the control / calculation unit 13 first reads the output evaluation value and the threshold value (step S31). Specifically, the level value L0 without a drop, the level value L1 of a small drop, the level value L2 of a medium drop, the level value L3 of a large drop, and the determination of no drop and a drop are used. The threshold value th0, the threshold value th1 used for the determination of the small droplet and the medium droplet, and the threshold value th2 used for the determination of the medium droplet and the large droplet are read.
[0053]
Next, the controller / arithmetic unit 13 receives the input image data value (the gradation value of the image data) ID subjected to the color conversion process, and the quantization error (output evaluation value OD from the image data value ID) of the surrounding pixels. Obtained by subtracting a predetermined weight and adding the value QE, and adding them to obtain a data value D, that is, D ← ID + QE (step S32). Store the value obtained.
[0054]
Incidentally, the quantization error here is diffused to the peripheral pixels by performing weighting predetermined by the process of the quantization error calculation and error diffusion (step S38) in the final stage. FIG. 7 schematically illustrates weighting when the quantization error applied to this quantization routine is diffused to surrounding pixels. Here, for example, when the input image data value ID is 200 and the output evaluation value OD is 255, if the quantization error is 200-255 = −55, the pixel P1 to the pixel P2 that are currently processed are processed. It is shown that the quantization error diffused in the range is −55 × 5/48 = −5.73, which is about −6. Such error diffusion is performed for all the pixels shown in FIG. 7, and this quantization error is reflected when the data value D is obtained in the process of D ← ID + QE (step S32).
[0055]
Further, the controller / arithmetic unit 13 determines whether or not the data value D is less than the threshold th2 (D <th2) (step S33). If the data value D is equal to or greater than the threshold th2, the output evaluation value OD. The process of OD ← L3 (step S375) for storing the large drop level value L3 is performed. If the data value D is less than the threshold th2, the quantization process performed in the group 1 is advanced according to the value of x, or In order to determine whether or not to proceed to the quantization processing performed in group 2, in order to set group 1 when the remainder when x is divided by n is m or more and set group 2 when x is smaller than m, x% n < It is determined whether or not m (step S34). For example, when n = 2 and m = 1, group 1 and group 2 appear alternately in the X direction.
[0056]
As a result of the determination of whether or not x% n <m (step S34), if x% n <m and not group 1, the drop evaluation level value L0 is stored in the output evaluation value OD OD ← L0 ( The process of step S374) is performed. If x% n <m and group 2, the process proceeds to determination of no-droplet / small-droplet / medium-drop according to the data value D.
[0057]
That is, it is determined whether or not the data value D is less than the threshold value th1 (D <th1) (step S35). If the data value D is equal to or greater than the threshold value th1, the medium drop level value L2 is included in the output evaluation value OD. OD ← L2 (step S373) is stored, but if the data value D is less than the threshold th1, it is subsequently determined whether or not the data value D is less than the threshold th0 (D <th0). (Step S36).
[0058]
As a result, if the data value D is equal to or greater than the threshold th0, the process of OD ← L1 (step S372) for storing the droplet level value L1 in the output evaluation value OD is performed, but if the data value D is less than the threshold th0. A process of OD ← L0 (step S371) for storing the drop-free level value L0 in the output evaluation value OD is performed, and the output evaluation value OD is determined by such a series of operation processes.
[0059]
Finally, the control / calculator 13 performs quantization error calculation by subtracting the determined output evaluation value OD from the input image data value ID, and also performs quantization error calculation for diffusing the quantization error to surrounding pixels and Error diffusion (step S38) is performed and the quantization routine is terminated. The quantization error calculation and error diffusion (step S38) processing is performed when the determined output evaluation value OD is converted into a data format for enabling the print recording processing by the printer 22, which is shown in FIG. As described above, the image data diffused to the peripheral pixels by applying a predetermined weight is transferred to the printer 22.
[0060]
According to the quantization and error diffusion processing in the image recording apparatus according to the first embodiment, the quantization error generated by not forming the dots is diffused around the pixels where the dots are not formed in the case of the group 1. Since dots are formed including this quantization error, the density when viewed macroscopically does not change, and a high-quality image can be obtained even if the number of pixels that do not form dots increases. Further, in the image recording apparatus according to the first embodiment, as described in detail in the fourth embodiment later, if the quantization is changed depending on the type of ink color, the banding of white fine stripes can be prevented. can get.
[0061]
Incidentally, in the quantization routine of FIG. 6, after comparing the data value D with the threshold th2 used for the determination of medium drops and large drops, the process proceeds to the quantization process of group 1 or the quantization process of group 2 is performed. The case of determining whether to proceed is exemplified, but this determination may be performed before determining the type of dot, or the comparison between the data value D and the threshold th1 used for determination of small droplets and medium droplets may be performed. You may go after you go. However, in the latter case, the type of dot belonging to group 1 is only a small droplet. In the quantization routine of FIG. 6, the types of dots belonging to group 1 are not particularly limited, and use of the highest density dots is avoided. However, when the highest density dots are used, This is because the density that can be expressed as a whole decreases, and the color space becomes narrower.
[0062]
FIG. 8 exemplifies how dots are arranged when n = 2 and m = 1 as a result of quantization and error diffusion processing according to the quantization routine of FIG. However, here, the intersection of straight lines drawn with dotted lines represents the center position of the pixel.
[0063]
Referring to FIG. 8, the operation and effect of applying the quantization routine will be described. In group 1, when the output evaluation value OD is set to the level value L0 without droplets, the quantization error increases and diffuses to surrounding pixels. The error is increased. In other words, the diffused quantization error becomes large in the peripheral pixels, so that high density dots are likely to appear. High-density dots have the effect of reducing the banding that fills the paper with a large area and white streaks.
[0064]
In addition, since the group 1 and the group 2 appear continuously in the transport direction of the recording medium such as paper, the dot arrangement is arranged in the transport direction of the recording medium as shown in the drawing, It tends to be difficult to place dots. As a result, even if the dot landing position is deviated in the reciprocating direction of the head, the possibility of overlapping with adjacent dots is reduced.
[0065]
Furthermore, even if the dot landing position shifts in the recording medium transport direction and the dots overlap, resulting in higher density, no dot is placed on both sides of the higher density position, so the density is high. The portion is less likely to be connected in the reciprocating direction of the head. As a result, there is an effect of reducing banding that appears when adjacent dots overlap and become darker.
[0066]
In addition, banding generally appears in a direction perpendicular to the conveyance direction of the recording medium. Therefore, if dots are arranged in parallel to the conveyance direction of the recording medium as shown in the figure, either in the vertical direction or the parallel direction in the print recording result However, the two-dimensional spatial frequency is increased, which has the effect of making banding inconspicuous.
[0067]
On the other hand, even in an image with a monotonous density change, by creating pixels that do not form dots, the types of dots that are ejected from the nozzles increase, and even with the same nozzle, depending on the type of dots that are ejected, the ejection direction, the occurrence of satellites, etc. Although the ejection characteristics may change, even if it has such characteristics, dots having various ejection characteristics can be mixed by increasing the types of dots to be ejected. As a result, even in an image having a monotonous change in density, dots having characteristics that adversely affect image quality are not evenly arranged, which has the effect of reducing banding.
[0068]
On the other hand, if quantization is performed so as to preferentially avoid the types of nozzles or dots that have ejection characteristics that adversely affect image quality, the proportion of dot types that have undesirable ejection characteristics can be reduced. As a result, it is possible to realize high image quality by performing quantization in consideration of ejection characteristics.
[0069]
In the case of the image recording apparatus according to the first embodiment described above, it has been described that the quantization is performed in order from the formation of the dot having the higher density. However, the order of determining the dot type in the quantization can be arbitrary. . In the case of the image recording apparatus according to the first embodiment, it is desirable that m pixels that do not form dots in the set of n pixels have periodicity and the frequency of the m pixels is increased. This is because the sensitivity to the high frequency component is lower than the sensitivity to the low frequency component as human vision, and it is difficult to visually recognize the effect of not forming dots and the effect on image quality can be minimized. Furthermore, in the case of the image recording apparatus according to the first embodiment, the process of quantizing the drop-free level value L0 as the output evaluation value OD according to a certain rule has been described, but the dot density lower than the original quantization result is described. If it is a type, the value set for the output evaluation value OD is not limited to the drop-free level value L0, and for example, a small drop level value L1 may be set. When the droplets are used, the quantization error is smaller than when no dots are formed, and the proportion of the dots formed in the peripheral pixels is high in density. Accordingly, in this case, the density difference between the pixels does not become too large, so that deterioration of graininess can be suppressed. In addition, in the case of the image recording apparatus according to the first embodiment, the process of creating pixels that do not form dots while repeating a predetermined rule has been described. For example, in the case where all the pixels constituting a straight line belong to group 2 in a straight line of one dot that is continuous in a certain direction, the straight line may disappear. Therefore, it is possible to cope with such a case. Therefore, if the rules are changed according to the characteristics of the image, a high-quality image can be obtained. Examples of the method for changing the predetermined rule include exchanging the group 1 and the group 2 or changing part of the dot type set in the output evaluation value OD.
[0070]
FIG. 9 is a flowchart showing detailed operation processing (quantization routine) of quantization processing performed by the control / calculator 13 provided in the image recording apparatus according to the second embodiment to which the image recording method of the present invention is applied. . However, in the case of the image recording apparatus according to the second embodiment, the basic configuration (hardware configuration) is the same as that in the first embodiment, but the control / calculator 13 is compared with the quantization routine described in FIG. The difference is that a process of dividing the group 1 and the group 2 is introduced in the middle of the quantization routine performed in (1).
[0071]
Specifically, in the case of the quantization routine here, when the operation process is started, the control / calculator 13 first performs the process of reading the output evaluation value and the threshold value (step S41), specifically, Is a drop-free level value L 0, a small-drop level value L 1, a medium-drop level value L 2, a large-drop level value L 3, a threshold th 0 used to determine whether there is no drop and a small drop, A threshold th1 used for determination of medium drops and a threshold th2 used for determination of medium drops and large drops are read.
[0072]
Next, the controller / arithmetic unit 13 calculates the input image data value ID subjected to the color conversion process and a value QE obtained by adding a predetermined weight to the quantization error of the peripheral pixels and adding them. Used, the data value D obtained by adding them, that is, the value obtained by the process of D ← ID + QE (step S42) is stored.
[0073]
Further, the control / calculator 13 determines whether or not the data value D is less than the threshold th2 (D <th2) (step S43). If the data value D is equal to or greater than the threshold th2, the output evaluation value OD is determined. The process of OD ← L3 (step S475) for storing the large drop level value L3 is performed. If the data value D is less than the threshold value th2, the process proceeds to the quantization performed in the group 1, or the quantum performed in the group 2. In order to determine whether or not to proceed to conversion, the X direction is the scanning direction of the carriage 67, the Y direction is the conveyance direction of the recording medium 61, and the X and Y coordinates in the image are x and y, and p, Under the condition that q is a natural number and the remainder when y is divided by q is represented by y% q, the remainder is determined by the remainder when x + p (y% q) is divided by n. When m is greater than or equal to m , X + p (y% q)% n <whether the determination is m the (step S44) performed and the case where m is less than to the group 2.
[0074]
As a result of determining whether or not x + p (y% q)% n <m (step S44), if x + p (y% q)% n <m and not group 1, the output evaluation value OD indicates no drop. The process of OD ← L0 (step S474) for storing the level value L0 is performed. If x + p (y% q)% n <m and group 2 is satisfied, there is no droplet / small droplet / medium according to the data value D Move on to drop determination.
[0075]
That is, it is determined whether or not the data value D is less than the threshold value th1 (D <th1) (step S45). If the data value D is equal to or greater than the threshold value th1, the medium drop level value L2 is included in the output evaluation value OD. OD ← L2 (step S473) is stored, but if the data value D is less than the threshold th1, it is determined whether the data value D is subsequently less than the threshold th0 (D <th0). (Step S46).
[0076]
As a result, if the data value D is greater than or equal to the threshold th0, the process of OD ← L1 (step S472) for storing the droplet level value L1 in the output evaluation value OD is performed, but if the data value D is less than the threshold th0. A process of OD ← L0 (step S471) for storing the drop-free level value L0 in the output evaluation value OD is performed, and the output evaluation value OD is determined by such a series of operation processes.
[0077]
Here again, finally, the controller / arithmetic unit 13 performs quantization error calculation by subtracting the output evaluation value OD determined from the input image data value ID, and also performs quantization error calculation for diffusing the quantization error to surrounding pixels. Then, error diffusion (step S48) is performed and the quantization routine is terminated. This quantization error calculation and error diffusion (step S48) processing is performed when the determined output evaluation value OD is converted into a data format for enabling the printer 22 to perform print recording processing. As described above, the image data diffused to the peripheral pixels by applying a predetermined weight is transferred to the printer 22.
[0078]
According to the quantization and error diffusion processing in the image recording apparatus according to the second embodiment, since the use rate of large dots is increased by providing pixels that do not form dots, the area on which ink is placed on the recording medium 61 is increased. In addition to obtaining an effect of reducing banding that includes white fine streaks, pixels that do not form dots in the conveyance direction of the recording medium 61 are created, so that dots are easily connected obliquely on the recording medium 61. Therefore, it is possible to obtain an effect of preventing banding that occurs when adjacent dots overlap to increase the density. Also in the image recording apparatus according to the second embodiment, as described in detail in the fourth embodiment later, if the quantization is changed according to the type of ink color, it is possible to prevent banding of fine white stripes. Is obtained.
[0079]
FIG. 10 exemplifies how dots are arranged when m = 1, n = 2, p = 1, and q = 2 as a result of quantization and error diffusion in the image recording apparatus according to the second embodiment. is there. FIG. 10 shows a state in which dots appear in a staggered pattern. Since the distance between adjacent dots increases, the robustness with respect to the deviation of the landing positions of the dots increases. It can be seen that banding that occurs when dots overlap and the density increases can be prevented.
[0080]
Incidentally, in the quantization routine of FIG. 9, the ratio and pattern of m pixels that do not form dots in the set of n pixels may be selected in accordance with the banding characteristics. As described in the case of Example 1, it is preferable to use a pattern having a high-frequency component, and it is desirable to avoid a dot having the highest density for a type that does not form dots.
[0081]
Furthermore, an image recording apparatus according to Example 3 to which the image recording method of the present invention is applied will be described. Also in the case of the image recording apparatus according to the third embodiment, the basic configuration (hardware configuration) is the same as that in the first embodiment, but group 1 and group are in the middle of the quantization routine performed by the control / calculator 13. 2 is different from the method in the first and second embodiments. That is, in the case of the first and second embodiments, grouping is performed using mathematical formulas based on information of two-dimensional coordinates in the image, whereas in this third embodiment, a predetermined rule can be executed. Grouping is performed using a two-dimensional matrix.
[0082]
The algorithm of the quantization routine based on this two-dimensional matrix is almost as shown in FIG. 6, but the determination (step S34) of whether x% n <m corresponding to the grouping process is different. In the following, the grouping process here will be described.
[0083]
FIG. 11 is a schematic diagram of a main part shown to explain a two-dimensional matrix used for a quantization routine in the controller / arithmetic unit 13 provided in the image recording apparatus according to the third embodiment. (A) relates to the gradation value before grouping, and (b) in FIG. 5 relates to the element configuration after grouping. However, the size of the two-dimensional matrix applicable here is arbitrary, and it is desirable that the two-dimensional matrix has a blue noise characteristic indicating that the image quantized as a dither threshold has a power spectrum of a large high-frequency component. . This is because in the case of human vision, since the ability to perceive high frequency components is low, even if the power spectrum of high frequency components is large, the image quality determined from human vision is not affected.
[0084]
In this grouping process, referring to FIG. 11A, first, each element E1 of the two-dimensional matrix is compared with a predetermined value and classified into group 1 and group 2. As an example, a case in which the value of each element E1 of the two-dimensional matrix is larger than 128 in FIG.
[0085]
Next, referring to FIG. 11 (b), after grouping, it is divided into group 1 and group 2, and as a result, for example, element E2 represents group 1 and element E3 represents group 2. . The quantization performed on these groups 1 and 2 is performed in the same manner as in the above-described embodiments, and the same effect can be obtained.
[0086]
If grouping using a two-dimensional matrix in the image recording apparatus according to the third embodiment is performed, one-dimensional low-frequency components generated by banding can be reduced, and two-dimensional high-frequency components can be increased, thereby reducing banding. Thus, the effect of suppressing the occurrence of perceived patterns can be obtained. Creation of such a two-dimensional matrix requires a lot of man-hours, but once it is created, it is possible to realize high-quality image output. Also in the image recording apparatus according to the third embodiment, as described in detail in the fourth embodiment later, if the quantization is changed according to the type of ink color, it is possible to prevent banding of fine white stripes. Is obtained.
[0087]
In addition, an image recording apparatus according to a fourth embodiment to which the image recording method of the present invention is applied will be described. In the case of the image recording apparatus according to the fourth embodiment, the basic configuration (hardware configuration) is the same as that in the first embodiment, but the quantized data creation routine performed by the control / calculator 13 is the same as that of the first embodiment. It is different from the case. That is, in the first embodiment, the quantization (step 13) processing after the color conversion (step S12) processing is performed in the same manner for all colors, whereas in the fourth embodiment, it differs depending on the type of ink color. Quantization processing is performed.
[0088]
FIG. 12 is a flowchart illustrating a routine for changing the quantization method for each color, which is applied to the quantized data creation routine performed by the control / calculator 13 provided in the image recording apparatus according to the fourth embodiment. The routine for changing the quantization method for each color is a case where the quantization process differs depending on the type of ink color. For example, magenta (M) and other cyan (C), yellow (Y), and black (K). If the control / calculator 13 starts operation, it first determines what the target color is in order to determine the color to be quantized. Step S51) Process. If the color to be quantized is any one of cyan (C), yellow (Y), and black (K) as a result of the process of determining the target color (step S51), CYK quantization is performed. The process of (Step S52) is performed. If it is magenta (M), the process ends after performing the process of quantization of M (Step S53). The CYK quantization (step S52) here may employ the quantization method already described in each embodiment, or may employ a quantization method not listed here. Any quantization method can be applied as long as the M quantization process (step S53) is different from the CYK quantization process (step S52).
[0089]
Specifically, when the quantization method is the same as in the case of the first embodiment, when the remainder when x is divided by n is m or more, cyan, yellow, and black are described in the first embodiment. The group 1 quantization process is performed, and magenta performs the group 2 quantization process described in the first embodiment. When the remainder when x is divided by n is smaller than m, cyan, yellow, and black perform the group 2 quantization process described in the first embodiment, and magenta performs the group 1 process described in the first embodiment. Performs quantization processing.
[0090]
FIG. 13 exemplifies dot arrangement when n = 2 and m = 1 in the quantization and error diffusion processing in the image recording apparatus according to the fourth embodiment. Here, however, the intersection of straight lines drawn with dotted lines represents the center position of the pixel. From FIG. 13, the cyan, yellow and black dots CYK and the magenta dot M are all easily connected in the transport direction of the recording medium 61, but their positions are shifted in the reciprocating direction of the head. I understand.
[0091]
When the quantization process is changed depending on the type of ink color as in the case of the image recording apparatus according to the fourth embodiment, the area where no ink is placed on the recording medium 61 is reduced, or the quantization process is changed. It is desirable to have a spatially complementary relationship so that the inks do not overlap easily. As a result, even in pixels where dots are not formed with a certain ink color, dots of other ink colors are formed, so the area where ink is not applied is reduced, thereby preventing the banding of fine white stripes. Is obtained.
[0092]
Finally, an image recording apparatus according to Example 5 to which the image recording method of the present invention is applied will be described. In the case of the image recording apparatus according to the fifth embodiment, the basic configuration (hardware configuration) is the same as that in the first embodiment, but in the middle of the quantization routine performed by the control / calculator 13, The method for dividing the group 2 is different from that in the first to third embodiments. That is, in the third embodiment, a configuration in which grouping is performed using a two-dimensional matrix capable of executing a predetermined rule is applied, and in this fifth embodiment, banding is reduced by adopting a dither method as a quantization method. This is done using a dither matrix. This dither method is described in, for example, “Fine Imaging and Hard Copy” (Corona) p. 309 and the like, the description of basic matters is omitted here, and the configuration of a dither matrix for reducing banding will be described below.
[0093]
FIG. 14 is a schematic diagram of a main part shown to explain a basic configuration of a dither matrix used for a quantization routine in the controller / arithmetic unit 13 provided in the image recording apparatus according to the fifth embodiment.
[0094]
In the dither matrix, the arrangement of the dots after the quantization process is set so that the dots are arranged in parallel with the conveyance direction of the recording medium 61 as shown in FIG. Further, the quantization process is performed by extending to the multi-value dither method.
[0095]
Referring to FIG. 14, the dither matrix column L1 has a larger assigned value than the other dither matrix columns, so that it is difficult to form dots or dots with high density. In L2, since the assigned value is small compared to the other dither matrix columns, it is easy to form dots, and it is easy to form dots with higher density than the dither matrix column L1. As a result, the dot arrangement after the quantization processing by the multi-value dither method is arranged in parallel with the conveyance direction of the recording medium 61 as in FIG. The effect of suppressing the banding by the dot arrangement is the same as described in the previous embodiments.
[0096]
Although the quantization method used in the first to fourth embodiments is based on the combined use of the error diffusion method, in general, high quality image quality can be obtained as a feature of the error diffusion method, but the processing cost is large. There is a problem of becoming. On the other hand, the special feature of the dither method is that the processing cost is low and the speed can be increased. Therefore, in the image recording apparatus according to the fifth embodiment, the processing speed can be improved by using the dither method as the quantization method, and the dot array after the quantization processing has the recording medium 61 as shown in FIG. Banding can be reduced by arranging them in parallel with the transport direction.
[0097]
However, in the image recording apparatus according to the fifth embodiment, after quantization processing, as shown in FIG. 8, the dither matrix is set in advance so that the dot arrangement is arranged in parallel with the conveyance direction of the recording medium 61. However, other quantization processing methods may be employed. That is, for example, a general dither matrix such as a Bayer type dither matrix is prepared, and the ease of appearance of dots is controlled by increasing or decreasing the value of the dither matrix depending on the position in the dither matrix. There are cases. Here, when the value of the dither matrix is increased, dots having high density are less likely to appear, and when the value of the dither matrix is decreased, dots having high density are likely to appear. The dither matrix value increasing / decreasing method here may be set in advance so as to be the dot arrangement embodied in each of the foregoing embodiments.
[0098]
As described above, in the case of the image recording apparatus according to the fifth embodiment, only the arrangement of the appearing dots is manipulated, and the density of the entire image is not changed. It is possible to obtain a quality image. Further, when performing multi-value dither processing, a higher quality image can be obtained by setting a dither matrix that disperses dots so as to have a high spatial frequency when forming the highest density dot. .
[0099]
The dither matrix used in the image recording apparatus according to the fifth embodiment has been described with reference to the case where the dither matrix is set according to the quantization processing in the first embodiment. If the dither matrix is configured as described above, the same effect can be expected with respect to banding and the like. It is also possible to use the quantization method embodied in each of the above-described embodiments and the quantization method described in Embodiment 5 in accordance with the type of ink and the type of dots to be formed.
[0100]
Each of the image recording apparatuses according to the first to fifth embodiments described above is a case where the printer 22 is an ink jet printer and the print head 59 having the piezoelectric element 68 and ejecting ink from the nozzle 70 is employed. As described above, it is possible to apply various different types of printers and printing apparatuses represented by other types of printers that eject ink with bubbles generated in the ink in the vicinity of the nozzles. Any device capable of expressing an image by assigning dots can be applied to a printing device other than a printer.
[0101]
In addition, in the case of the image recording apparatus according to the first to fifth embodiments, by including processing operations by the computer 10, as described above, a software program (image recording processing program) for implementing these processing operations. It is also possible to use a recording medium for an image recording apparatus in which is stored in advance. As such a recording medium for an image recording apparatus, for example, a flexible disk medium, a CD-ROM, a non-magnetic disk, an IC card, a ROM cartridge, a punch card, a printed matter on which a code such as a barcode is printed, an internal storage device of a computer (Various memories such as RAM and ROM) and external storage devices can be used in various forms readable by the computer 10.
[0102]
Further, in the case of the image recording apparatus according to the first to fifth embodiments, a software program for causing the computer 10 to perform processing operations including the above-described image recording process and the like is transmitted via a communication path by the program supply apparatus. It can also be set as the structure supplied.
[0103]
In addition, the basic configuration and processing operations of the image recording apparatuses according to the first to fifth embodiments can be implemented in various forms without departing from the gist thereof. For example, the various configurations described in the respective embodiments It is also possible to construct at least part or all of the processing operations by hardware, and the present invention is not limited to the disclosed mode.
[0104]
【The invention's effect】
As described above, according to the present invention, an area gradation that changes the size of each dot in a single color, a density gradation that uses inks with different densities, or both of these area gradations and density gradations. Image data having a predetermined gradation value in each hue for each pixel as input data applied to a printing apparatus including a head capable of forming two or more types of dots having different densities per unit area by combining After the input is converted to data that can be processed by the printing device, the pixels are composed of dots that can be formed by the head, and then quantized into an output evaluation value that is set according to the number of gradations that can be expressed by the printing device In this case, the high frequency component in the direction in which banding occurs without forming all the pixels with only one type of dots that can be formed by the head is larger than the low frequency component. After quantizing according to the above, the quantized image data is printed and recorded on the recording medium, so that banding that causes image quality degradation of images printed and recorded with multiple gradations per color is reduced. And high-quality print recording is possible. In particular, since quantization is applied to at least one type of dots excluding the highest density dot among the dots that can be formed by the head, the color space that can be expressed in the entire image can be widened. , It will be possible to achieve high image quality. Also, quantization is not performed on all inks corresponding to different hues, but at least two types are prepared, and quantization is changed according to the type of ink. Even in pixels where dots are not formed, other ink-colored dots are formed and the area where ink is not applied is reduced, thereby making it difficult for banding of fine white stripes to occur. Further, since the quantization is performed using a two-dimensional matrix that can execute the rule, if the two-dimensional matrix is set to have a high frequency component, a perceived pattern hardly occurs. In addition, since the quantization error indicated by the difference between the gradation value and the output evaluation value in the image data generated by quantization is diffused to surrounding pixels, the density of the entire image is maintained, so that the dot array When pixels having a large quantization error due to regularity are generated, the density can be kept constant by diffusing the quantization error to surrounding pixels, and a high-quality image can be obtained.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating a basic configuration of an image recording apparatus according to a first embodiment to which an image recording method of the present invention is applied.
2 is a functional block diagram schematically showing a functional configuration of processing contents by a software program applied to a computer provided in the image recording apparatus shown in FIG. 1. FIG.
FIG. 3 is a schematic diagram showing a main configuration of a printer provided in the image recording apparatus shown in FIG. 1;
4 is a perspective view schematically showing a detailed configuration of a print head provided in the printer shown in FIG. 3. FIG.
FIG. 5 is a flowchart showing a quantized data creation processing routine performed by a control / arithmetic unit provided in the image recording apparatus shown in FIG. 1;
6 is a flowchart showing detailed operation processing (quantization routine) of the quantization processing described in FIG. 5;
FIG. 7 schematically illustrates weighting when a quantization error applied to the quantization routine described with reference to FIG. 6 is diffused to surrounding pixels.
FIG. 8 schematically illustrates how dots are arranged when n = 2 and m = 1 as a result of quantization and error diffusion processing according to the quantization routine of FIG. 6;
FIG. 9 is a flowchart showing detailed operation processing (quantization routine) of quantization processing performed by a control / arithmetic unit provided in the image recording apparatus according to the second embodiment to which the image recording method of the present invention is applied.
FIG. 10 illustrates an example of how dots are arranged when m = 1, n = 2, p = 1, and q = 2 as a result of quantization and error diffusion in the image recording apparatus described in FIG. 9; is there.
FIG. 11 is a schematic diagram for explaining a two-dimensional matrix used for a quantization routine in a control / arithmetic unit provided in an image recording apparatus according to a third embodiment to which the image recording method of the present invention is applied; (A) relates to the gradation value before grouping, and (b) relates to the element configuration after grouping.
FIG. 12 shows a routine for changing the quantization method for each color applied to a quantized data creation routine performed by a control / calculator provided in the image recording apparatus according to the fourth embodiment to which the image recording method of the present invention is applied. It is a flowchart.
13 schematically illustrates how dots are arranged when n = 2 and m = 1 as a result of quantization and error diffusion processing in the image recording apparatus described with reference to FIG. 12;
FIG. 14 is a schematic diagram of a main part shown to explain a basic configuration of a dither matrix used for a quantization routine in a control / arithmetic unit provided in an image recording apparatus according to Embodiment 5;
[Explanation of symbols]
10 Computer
11 Input interface
12 Output interface
20 input devices
21 Output equipment
22 Printer
41 application
42 Resolution conversion module
43 color conversion module
44 color conversion table
45 Quantization module
46 Rasterizer
48 Printer Driver
50 Operation panel
51 Control circuit
52 Carriage motor
53 Drive belt
54 Position detection sensor
55 pulley
56 axes
57,58 cartridge
59 Print head
60 platen
61 Recording media
62 Paper feed motor
63-66 heads
67 Carriage
68 Piezoelectric elements
69 Ink supply path
70 nozzles
CYK Cyan / Yellow / Black dots
E1, E2, E3 elements
M Magenta dot
L1, L2 Dither matrix column
P1, P2 pixels

Claims (15)

An image data input processing stage for inputting image data having a predetermined gradation value; an image data conversion processing stage for converting the image data input in the image data input processing stage into data that can be processed by a printing apparatus; A quantization process stage that quantizes the image data converted in the image data conversion process stage into an output evaluation value that is set according to the number of gradations that can be expressed by the printing device, and the quantization process stage performs quantization An image recording method comprising: a print recording processing step of printing and recording the image data recorded on a recording medium;
In the quantization process step, the quantization is performed according to a rule that regularly arranges pixels in which no dots are placed in a direction in which banding occurs . 2. The image recording method according to claim 1, wherein in the quantization process step, the quantization is applied to at least one kind of dots excluding a dot having the highest density among dots that can be formed in the print recording process step. And an image recording method.   3. The image recording method according to claim 1, wherein in the quantization processing step, the quantization is performed by preparing at least two types without performing the same for all inks corresponding to different hues. Image recording method.   4. The image recording method according to claim 1, wherein in the quantization processing step, the quantization is performed using a two-dimensional matrix capable of executing the rule. Recording method.   5. The image recording method according to claim 1, wherein, in the quantization process step, a quantum indicated by a difference between a gradation value in the image data generated by the quantization and the output evaluation value. An image recording method characterized in that the density of the entire image is maintained by diffusing a conversion error to surrounding pixels. A printing apparatus having a head capable of forming two or more types of dots having different densities per unit area;
Image data input means for inputting image data having a predetermined gradation value;
Image data conversion means for converting the image data into data that can be processed by the printing apparatus, and image data converted by the image data conversion means are set according to the number of gradations that can be expressed by the printing apparatus. A computer having quantization means for quantizing the output evaluation value ,
The quantization means performs the quantization according to a rule that regularly arranges pixels without placing dots in a direction in which banding occurs.
The printing apparatus functions as a printing recording unit that prints and records the image data quantized by the quantization unit on a recording medium.   7. The image recording apparatus according to claim 6, wherein the quantization means applies the quantization to at least one kind of dots excluding the dot having the highest density among the dots that can be formed by the head. An image recording apparatus.   8. The image recording apparatus according to claim 6, wherein the quantizing unit prepares and performs at least two types of quantization without performing the same for all inks corresponding to different hues. Recording device.   9. The image recording apparatus according to claim 6, wherein the quantization unit performs the quantization using a two-dimensional matrix capable of executing the rule. apparatus.   10. The image recording apparatus according to claim 6, wherein the quantization unit is a quantization indicated by a difference between a gradation value in the image data generated by the quantization and the output evaluation value. An image recording apparatus that maintains the density of an entire image by diffusing an error to surrounding pixels. Image data input processing for inputting image data having a predetermined gradation value;
Image data conversion processing for converting the image data input in the image data input processing into data that can be processed by a printing apparatus;
The image data converted by the image data conversion processing is set according to the number of gradations that can be expressed by the printing apparatus in accordance with a rule that regularly arranges pixels without placing dots in the direction in which banding occurs. A quantization process for quantizing the output evaluation value,
An image recording processing program that enables a computer to execute print recording processing for transferring image data quantized by the quantization processing to a printing apparatus and printing and recording it on a recording medium. 12. The program for image recording processing according to claim 11, wherein the quantization process is performed by applying the quantization to at least one type of dots excluding a dot having the highest density among dots that can be formed by the printing apparatus. An image recording processing program including contents to be performed.   13. The program for image recording processing according to claim 11 or 12, wherein the quantization processing includes at least two types of contents prepared without performing the quantization on all inks corresponding to different hues in the same manner. An image recording processing program characterized by the above.   The image recording processing program according to any one of claims 11 to 13, wherein the quantization process includes a content of performing the quantization using a two-dimensional matrix capable of executing the rule. A characteristic image recording processing program.   15. The image recording processing program according to claim 11, wherein the quantization processing is indicated by a difference between a gradation value in the image data generated by the quantization and the output evaluation value. What is claimed is: 1. An image recording processing program comprising: contents for maintaining density of an entire image by diffusing a quantization error to surrounding pixels.

Images