JP2004284279A - Image processing device/method and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device capable of reducing image quality deterioration, and an image processing method and an image processing program. <P>SOLUTION: This image processing device is constituted in such a way that the formation of dots by a defective nozzle is considered as "no liquid droplet" and the quantization processing by binary error diffusion is operated on image data with regard to pixels on the periphery of the defective nozzle. In addition, as for the pixels around the part other than the periphery of the defective nozzle, normally the quantization processing by (quaternary) error diffusion is operated on image data. Consequently, dots hardly occur on the periphery of a large liquid droplet and the number of the pixels on which the dots are deposited, increases. Thus, even when no dots are deposited at all in a single line, the dot absence is not conspicuous. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus, an image processing method, and an image processing program, and particularly to forming a plurality of types of dots having different densities per unit area due to area gradation or density gradation or a mixture of them, and performing multi-gradation. The present invention relates to an image processing apparatus, an image processing method, and an image processing program that are suitable for an image recording apparatus that prints and records an image on a computer.
[0002]
[Prior art]
As one of digital color image output devices, a color inkjet printer having a plurality of color inks has been proposed, and is widely used for printing images. Ink jet printers eject ink from a plurality of nozzles in a head while moving a head in which a plurality of nozzles are integrated and arranged in a direction (main scanning direction) orthogonal to a direction in which a printing medium such as paper is fed (sub-scanning direction). An ink dot is formed by landing ink particles on a print medium to record an image. The ink uses black (K), cyan (C), magenta (M), and yellow (Y) as basic colors.
[0003]
In these types of ink jet printers, the density of nozzles has been increasing in recent years, and the number of nozzles in a head has also increased. On the other hand, there is a high demand for a higher printing speed, and one line is completed by one head scan (an image is formed in one pass). Conventionally, the effect of defective nozzles was reduced by using a plurality of nozzles per line, but as a result of creating an image in one pass, the ejection characteristics of each nozzle reduced the image quality. The effect is greater. Therefore, in order to obtain good image quality in one pass, it is desirable to realize a good ejection state for all nozzles. However, in reality, it is difficult to achieve this in terms of processing accuracy and cost, and the number of nozzles per head also increases. In some cases, the number of nozzles having a poor discharge state is increased. For this reason, image quality deterioration (banding of white stripes or the like) tends to occur.
[0004]
As an image quality correction for such a defective nozzle, for example, a technique described in Patent Document 1 has been proposed.
[0005]
In the technique described in Patent Document 1, when lines or dots are recorded on a recording medium by a plurality of recording elements, the lines or dots are regularly shifted from a predetermined position on the recording medium. At times, it has been proposed to change the line thickness or dot diameter of a printing element having a displacement and a printing element adjacent thereto. That is, it has been proposed to increase the dot diameter of a line (pixel) adjacent to the defective nozzle. As a result, a stripe pattern caused by a regular shift of lines or dots is visually inconspicuous.
[0006]
[Patent Document 1]
JP-A-2-192855 (pages 1-2, FIG. 1)
[0007]
[Problems to be solved by the invention]
However, the technique described in Patent Literature 1 has a problem that even if the dot diameter of a pixel adjacent to a defective nozzle is changed, density unevenness occurs with another pixel adjacent to the defective nozzle.
[0008]
For example, as shown in FIG. 10, in the technique described in Patent Document 1, when the dot # 4 is shifted upward, the dot # 3 is reduced and the dot # 5 is increased. However, since # 2 and # 6 are not changed at all, white stripes are formed between # 2 and # 3 by reducing # 3, and between # 5 and # 6 by increasing # 5. Contains darkening black streaks.
[0009]
SUMMARY An advantage of some aspects of the invention is to provide an image processing apparatus, an image processing method, and an image processing program that can reduce image quality degradation.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes an input unit that inputs image data having a gradation value for each pixel, and a plurality of pixel recording units that form dots for each pixel. A recording head capable of forming a plurality of types of dots having different densities per unit area according to an area gradation or an area gradation and a density gradation for each color; Means for prohibiting dot formation by a defective pixel recording unit, and a method for quantizing the image data input by the input means into the plurality of types of gradation numbers at which the recording head can form dots. The image data corresponding to the defective pixel neighboring pixel recording unit near the pixel recording unit and the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit are different from each other. It is characterized by comprising a quantizing means for performing that quantization.
[0011]
According to the first aspect of the present invention, the input means inputs image data having a gradation value for each pixel. For example, image data having gradation values of 0 to 255 is input.
[0012]
The prohibiting means prohibits dot formation by a defective pixel recording unit that cannot form dots normally among a plurality of pixel recording units.
[0013]
Further, the quantizing means quantizes the image data input by the input means to the number of gradations at which the recording head can form dots. Different quantization is performed for image data corresponding to the neighboring pixel recording unit and image data corresponding to a pixel recording unit other than the defective pixel neighboring pixel recording unit. For example, when quantizing the image data of 256 gradations into image data of 2 to 4 gradations, the quantization means converts the image data corresponding to the defective pixel neighboring pixel recording unit to 2 gradations and the other pixels. The recording unit quantizes the image data so as to have four gradations. In this way, by performing quantization, dots are not formed in the defective pixel recording portion, and large droplets having a large area on which ink is applied increase around the defective pixel recording portion, thereby suppressing banding such as white streaks due to the defective pixel recording portion. It is possible to reduce image quality deterioration.
[0014]
For example, as in the invention according to claim 2, the quantizing means sets the number of gradations after quantizing the image data corresponding to the defective pixel neighboring pixel recording unit to a value other than the defective pixel desired pixel recording unit. It is possible to quantize the image data corresponding to the pixel recording unit so that the number of gradations after the quantization is higher than the number of gradations. By performing such quantization, defective pixel recording can be performed. No dot is formed in the portion, and in the vicinity, the number of gradations becomes low, and the white streak due to the defective pixel recording portion can be made inconspicuous.
[0015]
In general, the smaller the number of gradations of quantization, the worse the granularity is, so that the defective pixel neighboring pixel recording unit has a worse granularity than the pixel recording units other than the defective pixel neighboring pixel recording unit. However, the quantizing means may be configured such that an image corresponding to a pixel recording section located between a defective pixel neighboring pixel recording section and a pixel recording section other than the defective pixel neighboring pixel recording section is provided. By quantizing the image data so that the number of gradations gradually increases with respect to the data, a boundary generated between the defective pixel neighboring pixel recording unit and a pixel recording unit other than the defective pixel neighboring pixel recording unit is defined. It can be made inconspicuous, and continuity of image quality is maintained.
[0016]
The image processing method according to claims 4 to 6 is an image processing method applicable to the image processing apparatus according to claims 1 to 3 described above. Similarly, the described image processing program is an image processing program applicable to the image processing apparatus according to the first to third aspects.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to a printing system including an inkjet printer.
[0018]
FIG. 1 is a block diagram showing a schematic configuration of a printing system including an inkjet printer according to an embodiment of the present invention.
[0019]
The input device 20, the output device 21 including the inkjet printer 22, and storage devices and communication devices (not shown) are connected to the computer 10. The input interface (IF) unit 11 and the output IF unit 12 control data exchanged between the various devices described above and the computer 10. Various processes related to printing performed in the computer 10 are managed by the control / calculation unit 13.
[0020]
FIG. 2 is a block diagram illustrating a software configuration of the printing system.
[0021]
When a print command is issued from the application program 41, the printer driver 47 of the computer 10 receives the data, converts the data into a data format that can be output by the inkjet printer 22, and outputs the data.
[0022]
When the printer driver 47 receives data from the application program 41, the first resolution conversion module 42 in the printer driver 47 starts processing. The resolution conversion module plays a role of converting the resolution into a resolution that can be output by the inkjet printer 22. The color conversion module 43 performs color conversion on the data according to the color conversion table 44. The color conversion table 44 is separately created and stored so that the characteristics of the colors created by the image data and the characteristics of the colors expressed by the inkjet printer 22 match. As a specific color configuration, image data including red (R), green (G), and blue (B) is converted from cyan (C), magenta (M), yellow (Y), and black ( It plays a role of converting the data into data matched to a color that can be expressed by the combination of the respective inks of K). The quantization module 45 has a role of quantizing to a quantum number that can be expressed by the inkjet printer 22. The rasterize 46 has a role of replacing the quantized data quantized by the quantization module 45 with data to be transferred to the inkjet printer 22, and transfers the data to the inkjet printer 22 after the replacement.
[0023]
FIG. 3 is a schematic configuration diagram of the inkjet printer 22. The ink jet printer 22 includes a control circuit 31 for performing main control, a drive mechanism for moving the carriage 37 in the axial direction of the platen 39 by the carriage motor 32, and a transport mechanism for transporting the recording medium P by the paper feed motor 38. And a printing mechanism for driving a print head 40 provided on the carriage 37 to discharge ink and form dots.
[0024]
The drive mechanism includes a shaft 36 provided in parallel with the shaft of the platen 39 to support the movement of the carriage 37, a pulley 35 for stretching a drive belt 33 between the carriage motor 32, and the origin of the carriage 37. And a position detection sensor 34 for detecting the position. That is, the belt 33 moves in a direction corresponding to the rotation direction of the carriage motor 32, and accordingly, the carriage 37 and the print head 40 are guided by the shaft 36, and the installation position direction (forward direction) of the carriage motor 32 in the drawing. Or, it is transported in the installation position direction (return direction) of the pulley 35.
[0025]
The printing mechanism includes a cartridge 411K for black ink provided on the carriage 37 and cartridges 412C, 413M, and 414Y for color ink (cyan (C), magenta (M), and yellow (Y)). In addition, the print head 40 arranged on the carriage 37 is provided with a black ink head 41K and three color heads 410C, 410M and 410Y for each color ink.
[0026]
The control circuit 31 receives information on the recording direction and the ejection amount of each of the CMYK inks from the computer 10 and executes a recording process. The recording medium P is conveyed in a direction (sub-scanning direction) orthogonal to the main scanning direction (the forward direction and the backward direction) of the carriage 37 and the print head 40.
[0027]
FIG. 4 is a perspective view of the configuration of the print head 40 as viewed obliquely from below (on the side of the recording medium). In FIG. 4, the print head 40 includes a head main body 410, a black ink cartridge 411K provided above the head main body 410, and C, M, and Y color ink cartridges 412C, 413M, and 414Y. In the head body 410, nozzle rows 421K, 422C, 423M, and 424Y corresponding to the colors of the ink in the upper ink cartridge are mounted.
[0028]
Each nozzle row is composed of a plurality of nozzles arranged in the feed direction of the recording medium P, and the nozzle rows 421K, 422C, 423M, and 424Y are arranged in a direction perpendicular to the feed direction of the recording medium P (that is, the carriage 37). In the direction of movement). In FIG. 4, Y (nozzle row 424Y), M (nozzle row 423M), C (nozzle row 422C), and K (nozzle row 421K) are arranged in this order from the left. In FIG. 4, when moving from left to right is the forward direction, and when moving from right to left is the backward direction, the ink lands on the recording medium in the order of KCYM in the forward direction and in the order of YMCK in the backward direction. Will be done.
[0029]
In FIG. 4, the arrangement of the nozzle rows is shown for each color. However, the arrangement is not limited to this, and various arrangements such as a staggered arrangement can be applied.
[0030]
Inside the head body 410, ink is supplied from the cartridges 411K, 412C, 413M, and 414Y to the nozzle rows 421K, 422C, 423M, and 424Y. Each of the nozzles constituting the nozzle rows 421K, 422C, 423M, and 424Y has a piezoelectric element.
[0031]
As is well known, the piezoelectric element has a property of changing its shape when a voltage is applied. Therefore, by utilizing this change in shape, the ink of the upper ink cartridge is ejected from the nozzle and the recording medium P Printing (recording) is performed by forming dots on the top. At this time, the size of the dot can be controlled by controlling the shape change of the piezoelectric element.
[0032]
Note that, in the present embodiment, a method including a head that discharges ink using a piezoelectric element is applied, but a recording apparatus that discharges ink by another method may be applied. For example, the present invention can be applied to a recording apparatus that discharges ink by using bubbles generated by applying heat to the vicinity of a nozzle (the size of a dot is controlled by a difference in the amount of applied heat).
[0033]
Next, a process of creating multi-valued quantized data to be printed by the inkjet printer 22 will be described. FIG. 5 is a flowchart showing an example of a quantization data creation processing routine, which is a process performed by the control / calculation unit 13 in the computer 10 shown in FIG. 1 executing the software shown in FIG. .
[0034]
First, when the quantization data creation process is started, original data is input to the control / calculation unit 13 (S10). The original data has 256 tones from 0 to 255 for each color of each pixel R, G, B. The resolution of this original data is arbitrary.
[0035]
The control / calculation unit 13 converts the resolution of the input original data into a resolution for printing by the inkjet printer 22 (S12). In this resolution conversion processing, printing may be performed without performing this processing depending on the user's request or the resolution of the input data.
[0036]
Further, the control / arithmetic unit 13 performs a color conversion process (S14). The color conversion process is a process of converting data consisting of three colors of R, G, and B into C, M, Y, and K data. This color conversion processing is performed by using a color conversion table lookup table (LUT) in which a combination matching the characteristics of C, M, Y, and K of the inkjet printer 22 is stored in advance.
[0037]
Generally, the number of gradations that can be expressed by the printer is smaller than the number of gradations of the original data. For example, the number of gradations of the original data represented by the bitmap (Bmp) file is 256 gradations for each color of RGB, while the number of gradations that can be expressed by the printer is at most 10 gradations. Often less. Therefore, the control / arithmetic unit 13 performs a quantization process on the data subjected to the color conversion process to reduce the number of gradations to the number of gradations that can be expressed by the printer (S16). Here, it is assumed that quantization is performed to four types of the number of gradations that can be expressed by the inkjet printer 22 from among the 256 kinds of gradation values of the original data. In the present embodiment, it is assumed that the four types of gradations that can be expressed by the inkjet printer 22 are “dot non-formation”, “small droplet formation”, “medium droplet formation”, and “large droplet formation”. However, the four types of gradations that can be expressed by the ink jet printer 22 are different inks such as “no dot formation”, “formation of low density ink”, “formation of medium density ink”, and “formation of high density ink”. It may be executed using the density, or may be executed based on a combination of the dot size and the ink density. Further, the number of gradations that can be expressed by the ink jet printer 22 is not limited to four kinds of gradations, but may be, for example, three kinds, five or more kinds of plural kinds of gradations. The details of the quantization process will be described later.
[0038]
By the way, the control / arithmetic unit 13 determines whether or not the quantization process has been performed for each color and the quantization process has been completed for all the colors. To end.
[0039]
The image data of all colors quantized in this way is finally converted into a data format that can be processed by the inkjet printer 22 by the control / calculation unit 13 and then sent to the inkjet printer 22 via the output IF unit 12. Will be transferred.
[First Embodiment]
Subsequently, the above-described quantization processing according to the first embodiment of the present invention will be described in detail. FIG. 6 is a flowchart illustrating a flow of the quantization process according to the first embodiment performed by the control / calculation unit 13. Note that the quantization operation method performed in the quantization processing of the present embodiment is an example in which the quantization operation method is performed using a generally known error diffusion method, and detailed description of the error diffusion method is omitted.
[0040]
In the following description, the nozzle rows 421K, 422C, 423M, and 424Y of the print head 40 of the inkjet printer 22 may not discharge ink droplets or may have a nozzle in a poor discharge state. The description will be made on the assumption that it is detected in the manufacturing stage and stored in the control / calculation unit 13.
[0041]
First, the coordinates and color-converted data in the image for each pixel are read into the control / calculation unit 13 (S20).
[0042]
Next, the control / arithmetic unit 13 weights errors generated in the peripheral pixels in a predetermined manner, and adds the total of the errors to the image data of the read pixels (S24). It is determined whether or not the pixel corresponds to a previously stored defective nozzle (S26).
[0043]
When the control / calculation unit 13 determines that the pixel is not a pixel corresponding to the defective nozzle, it subsequently determines whether or not the pixel is a pixel around the defective nozzle (S28). Here, the determination of the pixels around the defective nozzle is made, for example, by determining whether or not the nozzle is a nozzle adjacent to the defective nozzle or a nozzle corresponding to several rows before and after the defective nozzle.
[0044]
If the pixel is determined to be a pixel around the defective nozzle, quantization is performed with a binary halftone of "no drop / large drop" (S30). That is, a quantization operation by binary error diffusion is performed.
[0045]
If it is determined that the pixel is not a pixel around the defective nozzle, quantization using normal halftone is performed (S32). In the present embodiment, the normal halftone is a quaternary halftone of “no drop / small drop / medium drop / large drop”. That is, a quantization operation by quaternary error diffusion is performed.
[0046]
On the other hand, if it is determined that the pixel corresponds to the defective nozzle, the dot level is fixed to “no drop” (S34). That is, dot formation by a defective nozzle is prohibited.
[0047]
When the quantization calculation method is determined in this way, the control / calculation unit 13 determines the dot size (dot level) according to the determined quantization calculation method (S36). At this time, an error between the input image data and the output dot level is calculated (S40), and a predetermined weighting is performed to diffuse the error to peripheral pixels.
[0048]
Then, it is determined whether or not the determination of the dot level has been completed for all the pixels (S38). If the determination of the dot level for all the pixels has not been completed, the image data is read and the above processing is repeated. It is.
[0049]
For example, as shown in FIG. 7A, if the nozzle is defective due to the lack of the nozzle # 4 in the nozzle row, the ink is not ejected by the nozzle # 4 and banding (white streaks) occurs. Appear in the image. In the present embodiment, by performing the quantization process as described above, as shown in FIG. 7B, the nozzle of # 4 is not ejected, and the error is diffused to the periphery. At this time, in FIG. 7B, the nozzles of # 2 and # 3 are set to the dot level obtained by performing the quantization operation by the binary error diffusion, and the other nozzles are subjected to the quantization operation by the four-value error diffusion . As a result, as shown in FIG. 7B, a large drop has a large area where ink spreads, so that a portion where the # 4 nozzle is not ejected can be interpolated, and the occurrence of banding (white streaks) can be suppressed. it can.
[0050]
That is, since the quantization operation by the binary error diffusion is performed on the pixels around the defective nozzle, dots are unlikely to be generated around the large droplet, and the number of pixels where no dots are placed increases. As a result, even if no dot is placed in one line, the dot becomes inconspicuous. In FIG. 7B, the dot is not placed at the nozzle # 4, but the quantization operation by the binary error diffusion is performed around the nozzle, so that the number of pixels where the dot is not placed increases, and the banding becomes inconspicuous.
[0051]
Therefore, banding can be effectively suppressed by performing different quantization operations between the nozzles around the defective nozzle and the other nozzles.
[0052]
In the present embodiment, when performing a quantization operation using the error diffusion method, the image gradation value (image data) at the pixel near the defective nozzle is set in order to make large dots easily appear near the defective nozzle. The error diffusion may be performed after the correction is made to increase (increase the density).
[Second embodiment]
Subsequently, the above-described quantization processing according to the second embodiment of the present invention will be described in detail.
[0053]
In the first embodiment, the row for performing the quantization operation by the binary error diffusion, the row for performing the quantization operation by the quaternary error diffusion, and the type of the halftone are changed for each row. May have a discontinuity between binary and quaternary error diffusion. For example, in FIG. 7B, since # 1 and # 2 are quaternary error diffusion, high image quality is maintained without graininess. However, a phenomenon is conceivable in which the graininess suddenly deteriorates when # 3 is obtained by binary error diffusion. As shown in FIG. 7B, when the area of the binary error diffusion is one row, the deterioration of the graininess is not conspicuous, but when the area of the binary error diffusion is widened, the above-mentioned deterioration of the graininess becomes a problem. In the first embodiment, since the quantization operation is performed using the error diffusion method, the continuity in image quality is maintained to some extent. However, when the quantization operation by the dither method is considered, discontinuity of the image quality appears remarkably.
[0054]
Therefore, in the quantization process according to the second embodiment, in order to maintain continuity in image quality, a boundary that transitions from a region where quantization operation by binary error diffusion is performed to a region where quantization operation by normal error diffusion is performed is defined. Let it change gradually. Specifically, as shown in FIG. 8, a pixel adjacent to the defective nozzle performs a quantization operation by the binary error diffusion, and a pixel adjacent to the pixel to perform the quantization operation by the binary error diffusion is a binary error diffusion. A quantization operation is performed so that diffusion and quaternary error diffusion are performed in alternate columns.
[0055]
FIG. 9 is a flowchart illustrating the flow of a quantization process according to the second embodiment performed by the control / calculation unit 13. The quantization operation method performed in the quantization processing according to the present embodiment also shows an example in which a generally known error diffusion method is used, and a detailed description of the error diffusion method is omitted.
[0056]
In the following description, as in the first embodiment, a description will be given assuming that a defective nozzle is detected in advance, and the position of the defective nozzle is stored in the control / calculation unit 13 in advance.
[0057]
First, the coordinates and color-converted data in the image for each pixel are read into the control / calculation unit 13 (S50).
[0058]
Next, the control / arithmetic unit 13 weights the errors generated in the peripheral pixels in a predetermined manner and adds the total of those errors to the image data of the read pixels (S54). It is determined whether or not the pixel corresponds to a previously stored defective nozzle (S56). If there is no error from the peripheral pixels, it is determined whether or not the pixel corresponds to the defective nozzle (S56).
[0059]
When determining that the pixel is not a pixel corresponding to the defective nozzle, the control / calculation unit 13 subsequently determines whether or not the pixel is a pixel in a row around the defective nozzle (S58). Here, as shown in FIG. 8, for example, as shown in FIG. 8, if # 4 is a defective nozzle, it is determined whether the pixel is a pixel corresponding to the nozzle # 2 or # 3. Is determined.
[0060]
If it is a pixel in a row around the defective nozzle, it is next determined whether or not the pixel is in a row adjacent to the defective nozzle (S60). It is determined whether or not it is (S62), and in the case of an even-numbered column, quantization with normal halftone is performed (S64). Also in the present embodiment, the normal halftone is a quaternary halftone of “no drop / small drop / medium drop / large drop”. That is, a quantization operation by quaternary error diffusion is performed.
[0061]
If it is an odd-numbered column or if it is a pixel in a row adjacent to the defective nozzle, quantization is performed with a binary halftone of "no drop / large drop" (S66). That is, a quantization operation by binary error diffusion is performed.
[0062]
On the other hand, if the pixel is not a pixel in the row around the defective nozzle, quantization is performed using normal halftone (S64). If the pixel is a pixel corresponding to the defective nozzle, the dot level is fixed to “no drop”. (S68).
[0063]
When the quantization calculation method is determined in this way, the control / calculation unit 13 determines the dot size (dot level) according to the determined quantization calculation method (S70).
[0064]
Then, it is determined whether or not the determination of the dot level has been completed for all the pixels (S72). If the determination of the dot level for all the pixels has not been completed, the image data is read and the above-described processing is repeated. It is. At this time, an error between the input image data and the output dot level is calculated (S74) and added to the next pixel read (S50 to S54).
[0065]
That is, as shown in FIG. 8, the defective nozzle (# 4 in FIG. 8) is set to “no droplet / large droplet”, and the adjacent pixel performs a quantization operation by binary error diffusion to obtain a pixel corresponding to the defective nozzle. The pixels further adjacent to the pixel of interest are subjected to the quantization processing by the quaternary error diffusion for the even-numbered columns and the quantization processing by the binary error diffusion for the odd-numbered columns. Perform the conversion.
[0066]
As described above, in the second embodiment, the quantization process is performed so as to gradually change the boundary that changes from the region where the quantization operation based on binary error diffusion is performed to the region where the quantization operation based on normal error diffusion is performed. The above continuity can be maintained. Then, even when the quantization operation by the dither method is performed, continuity in image quality can be maintained.
[0067]
In the second embodiment, the pixels corresponding to the row adjacent to the defective nozzle are subjected to a quantization operation by binary error diffusion, and the adjacent pixels are alternately subjected to binary error diffusion and quaternary error diffusion for each column. Is performed, and the quantization operation by quaternary error diffusion is performed for other than the above. However, the present invention is not limited to this. For example, pixels corresponding to several rows adjacent to the defective nozzle are subjected to binary error diffusion. Is performed, and the quantization operation by binary error diffusion and quaternary error diffusion is alternately performed for each of several columns adjacent to this, and the quantization operation by quaternary error diffusion is performed for other than these. It may be. The boundary between the region where the quantization operation by the binary error diffusion is performed and the region where the quantization hydrochloric acid is performed by the quaternary error diffusion is alternately performed for each column by the quantization operation by the binary error diffusion and the quaternary error diffusion. Although the quantization operation is performed, the present invention is not limited to this. If the transition is made gradually, the operation may be performed every two columns instead of every column.
[0068]
In the first and second embodiments, the error diffusion method has been described as an example of the quantization operation method. However, the present invention is not limited to this. For example, the quantization operation may be performed by a dither method. It is possible. In this case, the quantization processing can be performed in the same manner as in the first and second embodiments by making the weight different depending on whether the pixel is a peripheral pixel of the defective nozzle or not.
[0069]
Furthermore, in the above-described first and second embodiments, the case where a plurality of types of dots are formed by area gray scale has been described as an example. However, the present invention is not limited to this. For example, area gray scale and density gray scale The present invention may be applied to a case where a plurality of types of dots are formed by combining.
[0070]
【The invention's effect】
As described above, according to the present invention, image data corresponding to a defective pixel neighboring pixel recording unit near the defective pixel recording unit, and image data corresponding to a pixel recording unit other than the defective pixel neighboring pixel recording unit, By performing different quantization in each step, it becomes possible to perform quantization so that the number of gradations becomes low in the vicinity of the defective pixel recording section, so that white streaks caused by the defective pixel recording section can be made inconspicuous. Thus, there is an effect that image quality deterioration due to a defective nozzle can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a printing system including an inkjet printer according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a software configuration of a printing system according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of an ink jet printer.
FIG. 4 is a perspective view of the configuration of the print head as viewed obliquely from below (on the side of the recording medium).
FIG. 5 is a flowchart illustrating an example of a quantization data creation processing routine.
FIG. 6 is a flowchart illustrating a flow of a quantization process according to the first embodiment.
FIG. 7A is a diagram illustrating an example of occurrence of banding (white streaks) due to missing nozzles, and FIG. 7B is a diagram illustrating banding reduction by quantization processing according to the first embodiment;
FIG. 8 is a schematic diagram for explaining a quantization process according to the second embodiment.
FIG. 9 is a flowchart illustrating a flow of a quantization process according to the second embodiment.
FIG. 10 is a diagram for explaining a problem of the related art.
[Explanation of symbols]
10 Computer
11 Input IF section
37 carriage
40 print head
45 Quantization module
410 Head body
421K, 422C, 423M, 424Y nozzle row

Claims (9)

Input means for inputting image data having a gradation value for each pixel,
A plurality of pixel recording units that form dots for each pixel are arranged, and recording that can form a plurality of types of dots having different densities per unit area according to area gradation or area gradation and density gradation for each single color. Head and
Prohibiting means for prohibiting dot formation by a defective pixel recording unit that cannot form dots normally among the plurality of pixel recording units;
When the image data input by the input unit is quantized into the plurality of types of gradation numbers at which the recording head can form dots, the image data corresponds to a defective pixel neighboring pixel recording unit near the defective pixel recording unit. The image data and the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit, a quantization unit that performs different quantization respectively,
An image processing apparatus comprising: The quantizing unit is configured to calculate the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit, based on a gradation number after quantizing the image data corresponding to the defective pixel neighboring pixel recording unit. The image processing apparatus according to claim 1, wherein the quantization is performed such that the number of gradations after quantizing is higher than the number of gradations. The quantizing unit gradually gradations the image data corresponding to the pixel recording unit located between the defective pixel neighboring pixel recording unit and the pixel recording unit other than the defective pixel neighboring pixel recording unit. 3. The image processing apparatus according to claim 2, wherein the image data is quantized so as to increase the number. A plurality of pixel recording units that form dots for each pixel are arranged, and recording that can form a plurality of types of dots having different densities per unit area according to area gradation or area gradation and density gradation for each single color. An image processing method for converting image data having a gradation value for each pixel so that recording can be performed by a head,
An input step of inputting the image data,
A prohibition step of prohibiting dot formation by a defective pixel recording unit that cannot form dots normally among the plurality of pixel recording units;
When quantizing the image data input by the input step into the plurality of types of gradation numbers at which the recording head can form dots, the image data corresponding to the defective pixel neighboring pixel recording unit near the defective pixel recording unit Image data and the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit, a quantization step to perform different quantization respectively,
An image processing method comprising: The quantizing step is performed by: comparing the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit with the number of gradations after quantizing the image data corresponding to the defective pixel neighboring pixel recording unit. 5. The image processing method according to claim 4, wherein the quantization is performed such that the number of gradations after quantizing is higher. The quantizing step includes gradually gradation of the image data corresponding to the pixel recording unit located between the defective pixel neighboring pixel recording unit and the pixel recording unit other than the defective pixel neighboring pixel recording unit. 6. The image processing method according to claim 5, wherein the image data is quantized so as to increase the number. A plurality of pixel recording units that form dots for each pixel are arranged, and recording that can form a plurality of types of dots having different densities per unit area according to area gradation or area gradation and density gradation for each single color. An image processing program for converting image data having a gradation value for each pixel so that recording can be performed by a head,
An input step of inputting the image data,
A prohibition step of prohibiting dot formation by a defective pixel recording unit that cannot form dots normally, among the plurality of pixel recording units;
When quantizing the image data input in the input step into the plurality of types of gradation numbers at which the recording head can form dots, the image data corresponding to a defective pixel neighboring pixel recording unit near the defective pixel recording unit Image data and the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit, a quantization step of performing different quantization respectively,
An image processing program for executing a process including: The quantization step may be performed by: comparing the image data corresponding to the pixel recording unit other than the defective pixel neighboring pixel recording unit, with respect to the gradation number after quantizing the image data corresponding to the defective pixel neighboring pixel recording unit. 8. The image processing program according to claim 7, wherein the quantization is performed such that the number of gradations after quantizing is higher. The quantization step includes gradually gradation of the image data corresponding to the pixel recording unit located between the defective pixel neighboring pixel recording unit and the pixel recording unit other than the defective pixel neighboring pixel recording unit. 9. The image processing program according to claim 8, wherein the image data is quantized so as to increase the number.

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