JP2004042350A - Image processor and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure high quality image recording even when recording is performed using a recording head having a recording element impossible of performing normal recording. <P>SOLUTION: The image processor comprises a section 100 for detecting a nozzle impossible of performing normal recording based on the ejecting condition, a section 101 for deciding whether raster data is recorded by a nozzle impossible of performing normal recording or not, a quantizing section 106 for converting the multi-gray level data of each inputted pixel into data of lower gray level than the input gray level, and a section 108 for diffusing the difference between the input data of a remarked pixel and the quantized data to the pixels on the periphery of the remarked pixel. The quantization threshold value for a raster in the vicinity of a raster being recorded by a nozzle judged as a nozzle impossible of performing normal recording at the quantizing section 106 is set at a value different from those of other rasters at a threshold value setting section 105. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus and an image processing method, and more particularly, to a recording apparatus that performs recording by moving a recording head having a plurality of recording elements arranged in a predetermined direction relative to a recording medium and performing recording. Is converted into data having a smaller number of gradations than the number of input gradations.
[0002]
[Prior art]
For example, as an information output device in a word processor, a personal computer, a facsimile, and the like, there are various types of recording devices that record desired information such as characters and images on a sheet-shaped recording medium such as paper or film. Among them, a method of forming a text or an image on a recording medium by attaching a recording agent to the recording medium has been put into practical use, and an ink jet recording apparatus is a typical example of such a method. In recent years, the performance of ink jet recording apparatuses has been improved, and not only texts but also images have been recorded.
[0003]
In the ink jet recording apparatus, a nozzle group in which a plurality of ink discharge ports (nozzles) capable of discharging ink of the same color and the same density is used in order to improve the recording speed and improve the image quality. Usually, nozzle groups are provided for inks of the same color but of different densities or inks of different colors. Further, there is an ink jet printer in which the ejection amount of the same color and the same density of ink is changed in several steps so that the ejection can be performed.
[0004]
Then, printing is performed by ejecting ink from the nozzles while moving the print head provided with these nozzle groups relatively to the print medium.
[0005]
When an image is recorded, a halftone processing method such as a dither method or an error diffusion method is used as a method for faithfully reproducing the gradation of image information. For example, R.I. is known as a method of converting multi-valued image data into a binary image (or an image having a binary number or more and a number of gradations smaller than the number of input gradations). The error diffusion method by Floyd et al. (“An adaptiveE algorithm for Spatial gray ScalE”, SID IntErnational Symposium DigEst of Tech., Pap. , A pseudo gray scale expression is performed by diffusing the data into a plurality of pixels.
[0006]
The error diffusion method is widely used in image processing apparatuses such as printers, copiers, and facsimile machines as a pseudo halftone processing method having high gradation reproducibility.
[0007]
[Problems to be solved by the invention]
However, when recording is performed using the above-described error diffusion method, the following problems occur.
[0008]
Here, an ink jet printer that forms an image by scanning a recording head having a plurality of nozzles arranged in a predetermined direction on a recording medium in a direction intersecting with the arrangement direction of the nozzles and discharging ink on the recording medium. A case where an image is recorded by a serial printer as described above will be described as an example.
[0009]
Among a plurality of nozzles that eject ink droplets (dots), there are nozzles that cannot eject a dot due to some influence (non-ejection) or nozzles whose ejected dot volume is less than a specified value. In particular, when the nozzle row is long and has a large number of nozzles, there is a high probability that there are nozzles that cannot perform such normal printing.
[0010]
FIG. 6 is a diagram showing a process of forming an image by scanning one line of an image line (raster) using one nozzle line. Reference numeral 60 denotes a nozzle having a good ejection state, 61 denotes a nozzle in a non-printing state in which dots cannot be ejected, 62 denotes a binarization result by an error diffusion method, and 63 denotes a dot recording state.
[0011]
As shown in FIG. 6, when an image is formed by one scan, dots cannot be printed on a printing medium on a raster corresponding to a non-printing nozzle. Therefore, when it is necessary to form dots on the raster corresponding to the non-printing nozzles by the binarization processing using the conventional error diffusion method, the number of dots that must be actually printed near the dots An image is formed with a smaller number of dots. That is, density preservation, which is one of the advantages of the error diffusion method, is not sufficiently performed, and the quality of a recorded image is significantly reduced.
[0012]
The present invention has been made in view of the above circumstances, and is an image processing apparatus capable of performing high-quality image recording even when performing recording using a recording head having a recording element that cannot perform normal recording. And an image processing method.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an image processing apparatus according to the present invention is an image processing apparatus for a recording apparatus that performs recording by moving a recording head having a plurality of recording elements arranged in a predetermined direction relative to a recording medium. And
Determining means for determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording,
Quantization means for converting the input multi-grayscale data of each pixel into data having a smaller number of tones than the number of input tones;
Error diffusion means for diffusing the difference between the input data of the pixel of interest and the data quantized by the quantization means to pixels around the pixel of interest,
The quantizing means determines that the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording by the determining means has a different quantization value from the data of the other pixels. Is performed.
[0014]
According to another aspect of the present invention, there is provided an image processing method for a printing apparatus which performs printing by moving a printhead having a plurality of printing elements arranged in a predetermined direction relative to a print medium. And
A determining step of determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording;
A quantization step of converting the input multi-grayscale data of each pixel into data having a smaller number of gradations than the number of input gradations;
Error diffusion step of diffusing the difference between the input data of the target pixel and the data quantized in the quantization step to pixels around the target pixel,
In the quantization step, the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording in the determination step has a different quantization value from the data of the other pixels. Is performed.
[0015]
Further, the above object is also achieved by a computer program for causing a computer to execute the image processing method, and a storage medium storing the program.
[0016]
That is, according to the present invention, in a printing apparatus that performs printing by moving a printing head having a plurality of printing elements arranged in a predetermined direction relative to a printing medium, the input pixel data can be printed normally. It is determined whether the data is pixel data recorded by a recording element that cannot be performed, and the input multi-grayscale data of each pixel is converted into data having a grayscale number smaller than the input grayscale number. The difference between the input data of the pixel and the data quantized in the quantization is diffused to the pixels around the pixel of interest, and in the quantization, it is determined that recording is performed by a recording element that cannot perform normal recording. A different quantization process is performed on the data of the pixels in the vicinity of the pixel than the data of the other pixels.
[0017]
With this configuration, the data of the neighboring pixels of the data of the non-recording pixel determined to be recorded by the recording element that cannot perform normal recording is processed differently from the other pixel data, for example, is recorded. By performing a process for increasing the number of dots, it is possible to alleviate a sharp decrease in density caused by the data of the non-printed pixels.
[0018]
Therefore, even when printing is performed using a print head having a print element that cannot perform normal printing, high-quality image printing in which white stripes are suppressed by alleviating a sharp decrease in density caused by data of non-printed pixels. Can be performed.
[0019]
It is preferable that the quantizing means further includes a threshold changing means for changing a threshold value at the time of quantization with respect to data of a pixel near the non-recorded pixel.
[0020]
In this case, when the threshold value changing unit changes the threshold value so that the number of recording dots for pixels near the non-recording pixel increases, a sharp decrease in density exerted by data of the non-recording pixel can be effectively mitigated.
[0021]
It is preferable that the apparatus further includes a user interface for a user to select a parameter used by the threshold value changing unit.
[0022]
As the parameter, an application range of the threshold variation process, a threshold variation intensity, presence / absence of reference to an input pixel value at the time of threshold setting, and the like can be considered.
[0023]
It is preferable that the threshold variation unit defines the variation of the threshold with reference to the data of the input pixel.
[0024]
It is preferable that the image processing apparatus further includes a detecting unit that detects a recording element that cannot perform normal recording.
[0025]
In this case, it is preferable that the detecting unit detects a recording element that cannot perform normal recording based on a driving result of each recording element or a recording result of each recording element on a recording medium.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0027]
In the embodiment described below, a recording head having a plurality of nozzles arranged in a predetermined direction is scanned on a recording medium in a direction intersecting with the arrangement direction of the nozzles to discharge ink onto the recording medium. An image processing apparatus related to a serial type recording apparatus using an ink jet recording method for forming an image will be described as an example.
[0028]
(1st Embodiment)
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention. 100 is an ejection state detection unit, 101 is a non-recording raster determination unit, 102 is an address input terminal, 103 is an input terminal for pixel data, 104 is a cumulative error addition unit, 105 is a threshold setting unit that sets a quantization threshold, and 106 is A quantization unit 107 is an error calculation unit that calculates a quantization error, 108 is an error diffusion unit that spreads a quantization error, 109 is a cumulative error memory, and 110 is an output terminal for image data formed after a series of processing. .
[0029]
Hereinafter, the operation of the image processing apparatus of FIG. 1 will be described with reference to the flowchart of FIG.
[0030]
First, the ejection state detection unit 100 detects the ejection state of each nozzle (step S200). Here, a nozzle in a non-printing state in which the ejection amount of ink droplets from each nozzle is less than a specified value is detected. Next, an input image is sequentially scanned by an image scanning unit (not shown), and each pixel data is input from the input terminal 103 (step S201).
[0031]
FIG. 3 is a diagram showing a state of scanning of an input image. Reference numeral 300 denotes a pixel at the upper left end of the input image, and reference numeral 301 denotes a pixel at the lower right end of the input image. The scanning of the image starts from the pixel 300 at the upper left corner of the image area and proceeds to the right in units of one pixel. Then, when reaching the right end of the image data sequence, the process moves to the left end pixel of the image data sequence one pixel lower. The process is repeated in this way, and when the process reaches the pixel 301 at the lower right, the scanning process of the image is completed.
[0032]
Next, the cumulative error value corresponding to the pixel position of the cumulative error memory is added to the input pixel data in the cumulative error adding unit 104 (step S202). The cumulative error memory has one storage area E0 and the same number of storage areas E (x) as the number of horizontal pixels W of the input image, and stores a quantization error by a method described later. It is assumed that all the accumulated error memories have been initialized to the initial value 0 before the processing is started.
[0033]
FIG. 4 is a diagram showing details of the contents stored in the accumulated error memory. In the cumulative error adding unit 104, the value of the error memory E (x) corresponding to the horizontal pixel position x of the input pixel data is added. That is, with respect to the input pixel data I, the value of the pixel data I ′ after adding the cumulative error is
I ′ = I + E (x)
It becomes.
[0034]
Next, the non-recording raster determination unit 101 refers to the raster number of the input image input from the address input terminal 102, and determines whether there is a non-recording raster for which image formation is not possible near the raster of interest (step). S203). Here, when the raster number of the target raster is L, the number of nozzles provided in the nozzle row is N, and the nozzle number in the non-printing state is Pi,
L% N = (Pi + N-1)% N
L% N = (Pi + 1)% N
It is determined that a non-record raster exists in the vicinity of a raster satisfying any one of the above. Note that% is an operator representing modulo (remainder).
[0035]
FIG. 5 is a diagram illustrating an image forming process in the case where a nozzle row in which the number of nozzles N = 16 and the nozzle numbers in the non-printing state are P0 = 3 and P1 = 11 is used. As shown in FIG. 5, rasters adjacent to raster numbers L = 3, 11, 19,... Of the output image, that is, rasters with raster numbers L = 2, 4, 10, 12, 18, 20,. It is determined that the recording raster exists in the vicinity.
[0036]
Next, when it is determined that a non-recording raster exists near the focused raster, the threshold setting unit 105 performs a first threshold setting process A (step S204), and determines that there is no non-recording raster near the raster. If it is determined, the threshold setting unit 105 performs a second threshold setting process B (step S205).
[0037]
Here, the individual threshold setting processing will be described in detail. First, in the first threshold setting process A, a value obtained by applying a variation amount according to an input pixel value to a reference threshold (reference threshold) is used as a threshold at the time of quantization. That is, if the input pixel value is an integer value in the range of 0 to 255, and the reference threshold value is 128, which is the median value of the definition area of the input pixel, the threshold value Th (L) is expressed by the following equation:
Th (L) = 128 + Th_v (I)
Is determined by
[0038]
Here, Th_v (I) is the amount of change applied to the reference threshold, and is determined according to the input pixel value I. In the present embodiment, the formula:
Th_v (I) = I / 2
It is assumed that this variation is defined. In this embodiment, it is assumed that dots are recorded at pixel positions where the output value is 0, and dots are not recorded at pixel positions where the output value is 255.
[0039]
Since a non-recording raster cannot perform dot recording, a raster having a lower density is generated as compared with a nearby raster in which dot recording can be performed as usual, and a so-called “white streak” is generated. In order to alleviate the occurrence of the white stripe, the number of dots recorded on the raster adjacent to the non-record raster is increased more than usual, and the decrease in density damaged in the white stripe is compensated for by the density of the nearby raster.
[0040]
On the other hand, in the second threshold setting process B, the threshold at the time of quantization is as the reference threshold,
Th (L) = 128
And
[0041]
Next, a quantization process is performed in the quantization unit 106 (step S206). The pixel data I ′ after the addition of the accumulated error is compared with a threshold value Th (L) determined by the threshold value setting unit 105 to determine an output pixel value. In the present embodiment, the output value after quantization is binary, and the output pixel value is determined by comparing the threshold value Th (L) with the pixel data I ′ after the addition of the cumulative error. That is, assuming that the input pixel value is an integer value in the range of 0 to 255, the output gradation value O is expressed by the following formula:
O = 0 (I '<Th (L))
O = 255 (I ′ ≧ Th (L))
Determined from the load.
[0042]
Next, the error calculator 107 calculates the difference between the pixel data I ′ after the addition of the cumulative error and the output pixel value O, that is, the quantization error Err,
Err = I'-O
(Step S207).
[0043]
Next, in the error diffusion unit 108, according to the horizontal position x of the pixel of interest,
E (x + 1) ← E (x + 1) + E × 7/16 (x <W)
E (x-1) ← E (x-1) + E × 3/16 (x> 1)
E (x) ← E0 + E × 5/16 (1 <x <W)
E (x) ← E0 + E × 8/16 (x = 1)
E (x) ← E0 + E × 13/16 (x = W)
E0 ← E × 1/16 (x <W)
E0 ← 0 (x = W)
The error diffusion processing is performed so that
[0044]
Thus, the error diffusion processing for one pixel of the input image is completed. It is determined whether or not this error diffusion processing has been performed on all pixels of the input image (step S209). If it is determined that the above processing has been performed on all pixels, the pseudo halftone processing of the input image is performed. Is completed.
[0045]
In the threshold setting process A according to the first embodiment, two rasters adjacent to the non-recording raster are targeted. However, the threshold is not limited to two rasters as long as the raster is near the non-recording raster.
[0046]
Further, in the threshold setting process A according to the first embodiment, the variation applied to the threshold is determined with reference to the input pixel value, but may be a fixed value that does not depend on the input pixel value.
[0047]
In the first embodiment, the ejection state detection unit detects the nozzles in the non-printing state by detecting the ejection amount of the ink droplets from each nozzle, but the ejection state detection unit detects the ink droplets ejected from each nozzle. The nozzle in the non-printing state may be detected by focusing on the printing area on the printing medium.
[0048]
As described above, according to the first embodiment, for a raster in which image formation cannot be performed due to the influence of a nozzle in a non-printing state, the frequency of occurrence of recording dots of an adjacent raster is increased. It is possible to alleviate a sharp decrease in density due to a raster on which image formation cannot be performed, and to suppress the occurrence of white streaks, thereby providing a high-quality output image.
[0049]
(Second embodiment)
Hereinafter, a second embodiment of the image processing apparatus according to the present invention will be described. In the following description, the same parts as those in the first embodiment will not be described, and the description will focus on the characteristic parts of the present embodiment.
[0050]
FIG. 7 is a block diagram showing the configuration of the second embodiment of the image processing apparatus of the present invention. The difference from the configuration of the first embodiment shown in FIG. 1 is that a threshold parameter setting unit 700 for setting parameters when setting a threshold and a monitor 701 for setting threshold parameters are added. .
[0051]
Hereinafter, the operation of the image processing apparatus of FIG. 7 will be described with reference to the flowchart of FIG.
[0052]
First, the ejection state detection unit 100 detects the ejection state of each nozzle (step S800). Here, a nozzle in a non-printing state in which the ejection amount of ink droplets from each nozzle is less than a specified value is detected. Next, in a threshold parameter setting unit 700, as a threshold parameter, an application range of a threshold variation process performed on a raster near a non-recording raster, on which an image cannot be formed, which will be described later, a threshold variation intensity, and an input pixel value for threshold setting are set. The presence or absence of reference is specified by the user (step S801).
[0053]
FIG. 9 shows an example of a user interface screen for specifying these threshold parameters. The user interface screen is displayed on the monitor 701. Reference numeral 900 denotes an application range specifying unit for threshold fluctuation processing, 901 denotes a threshold fluctuation intensity specifying unit, 902 denotes an input pixel value reference presence / absence specifying unit for threshold setting, 903 denotes a threshold parameter setting determining unit, and 904 denotes re-execution of threshold parameter setting. The decision unit. In the present embodiment, as shown in FIG. 9, it is assumed that the application range of the threshold variation process is ± 2 rasters, the threshold variation intensity is 64, and the threshold parameter is specified so as to refer to the input pixel value.
[0054]
Next, an input image is sequentially scanned by an image scanning unit (not shown), and each pixel data is input from the input terminal 103 (step S802). The scanning of the image is the same as in the first embodiment described with reference to FIG.
[0055]
Next, the cumulative error value corresponding to the pixel position of the cumulative error memory is added to the input pixel data in the cumulative error adding unit 104 (step S803). The cumulative error memory has one storage area E0 and the same number of storage areas E (x) as the number of horizontal pixels W of the input image, and stores the quantization error as in the first embodiment described with reference to FIG. I have. It is assumed that all the accumulated error memories have been initialized to the initial value 0 before the processing is started.
[0056]
Next, the non-recording raster determination unit 101 refers to the raster number of the input image input from the address input terminal 102, and determines that the target raster is within the range in which the threshold variation process specified by the application range specifying unit 900 is performed. Is determined (step S804). Here, when the raster number of the raster of interest is L, the number of nozzles provided in the nozzle row is N, the nozzle number in the non-printing state is Pi, and the application range n of the threshold variation process is ± 2 rasters,
L% N = (Pi + n)% N (n = −2, −1,..., 1, 2)
Are determined to be within the applicable range of the threshold variation process.
[0057]
The application range n of the threshold variation process corresponds to the application range illustrated on the user interface screen of FIG. 9, and if the application range is specified as ± 1 raster,
-1 ≦ n ≦ 1
When the application range is specified as ± 3 rasters,
-3 ≦ n ≦ 3
Is defined respectively. Note that% is an operator representing modulo (remainder).
[0058]
Similar to the first embodiment, in the case of using the nozzle row shown in FIG. 5 in which the number of nozzles N = 16 and the nozzle numbers in the non-printing state are P0 = 3 and P1 = 11, the present embodiment Since the application range of the threshold variation process is defined as ± 2 rasters near the non-recording raster as described above, the raster numbers L of the output image are L = 1, 2, 4, 5, 9, 10, 12, 13,. The rasters at 17, 18, 20, 21,... Are subjected to the threshold variation processing.
[0059]
Next, when it is determined that the target raster is within the applicable range of the threshold variation process, the threshold setting unit 105 performs a first threshold setting process A (step S805), and determines that the raster is out of the applicable range. Then, the threshold setting unit 105 performs a second threshold setting process B (step S806).
[0060]
Here, the individual threshold setting processing will be described in detail. First, in the first threshold setting process A, a value obtained by applying a fluctuation amount defined by the threshold fluctuation intensity specifying unit 901 to the reference threshold is used as a threshold at the time of quantization. That is, assuming that the input pixel value is an integer value in the range of 0 to 255 and the reference threshold value is 128, which is the median value of the definition area of the input pixel, the threshold value Th (L) is given by the following expression
Th (L) = 128 + Th_v (I)
Is determined by
[0061]
Here, Th_v (I) is a fluctuation amount applied to the reference threshold, and is linked to the threshold fluctuation intensity V defined by the threshold fluctuation intensity specifying unit 901 and the setting result of the input pixel value reference presence / absence specifying unit 902. Is determined. In the present embodiment, the threshold fluctuation intensity V is set to 64 and the input pixel value I is referred to.
Th_v (I) = I × V / 255 (V = 64)
It is assumed that this variation is defined.
[0062]
The threshold fluctuation intensity V corresponds to the fluctuation intensity specified on the user interface screen of FIG. 9. When the fluctuation intensity is specified as 128, V = 128, when 32 is specified, V = 32, and when 16 is specified, V = 16. , 8 are defined as V = 8.
[0063]
If the input pixel value reference presence / absence designation unit 902 is set so as not to refer to the input image value, the expression,
Th_v (I) = V / 255
Gives the amount of variation applied to the reference threshold.
[0064]
In this embodiment, it is assumed that dots are recorded at pixel positions where the output value is 0, and dots are not recorded at pixel positions where the output value is 255.
[0065]
Since a non-recording raster cannot perform dot recording, a raster whose density is lower than that of a nearby raster in which dot recording can be normally performed is generated, and a so-called “white streak” is generated. In order to alleviate the occurrence of white streaks, a threshold setting process A for adjusting the threshold fluctuation amount governing the frequency of recording dots in accordance with a parameter specified by the user, for several rasters located near the non-recording raster. Is carried out.
[0066]
On the other hand, in the second threshold setting process B, the threshold at the time of quantization is as the reference threshold,
Th (L) = 128
And
[0067]
Next, a quantization process is performed in the quantization unit 106 (step S807). The processing performed here is the same as the processing performed in step S206 in the first embodiment, and a description thereof will be omitted.
[0068]
Next, the error calculator 107 calculates the difference between the pixel data I ′ after the addition of the cumulative error and the output pixel value O, that is, the quantization error Err,
Err = I'-O
Is calculated (step S808).
[0069]
Next, the error diffusion unit 108 performs an error diffusion process according to the horizontal position x of the pixel of interest (step S809). The processing performed here is the same as the processing performed in step S208 in the first embodiment, and a description thereof will be omitted.
[0070]
Thus, the error diffusion processing for one pixel of the input image is completed. It is determined whether or not this error diffusion processing has been performed on all pixels of the input image (step S810). If it is determined that the above processing has been performed on all pixels, the pseudo halftone processing of the input image is performed. Is completed.
[0071]
In the second embodiment, the ejection state detection unit detects the ejection amount of ink droplets from each nozzle to detect a nozzle in a non-printing state. However, the ejection state detection unit detects the ink droplet ejection from each nozzle. The nozzle in the non-printing state may be detected by focusing on the printing area on the printing medium.
[0072]
As described above, according to the second embodiment, the amount of threshold fluctuation at the time of quantization of a raster within a specified range from a raster in which image formation cannot be performed due to the effect of a nozzle in a non-printing state is determined by the user. , It is possible to change the output image quality as desired by the user.
[0073]
(Other embodiments)
In the embodiment described above, an image is formed by ejecting ink to a recording medium by scanning a recording head having a plurality of nozzles arranged in a predetermined direction on a recording medium in a direction intersecting the arrangement direction of the nozzles. Although an image processing apparatus according to a recording apparatus using an ink jet recording method has been described as an example, the present invention can be applied to a recording apparatus that performs recording according to a method other than the ink jet method. In this case, the nozzles that eject ink droplets correspond to the recording elements that record dots.
[0074]
In addition, the present invention has a recording head having a length corresponding to the recording width of the recording medium, and performs recording by moving the recording medium with respect to the recording head. The present invention can also be applied to a recording device that performs recording by moving a recording head relatively to a recording medium, other than a recording device of a type (printer).
[0075]
Further, in the above-described embodiment, the image processing apparatus has been described as including the discharge state detection unit that detects the discharge state of each nozzle of the print head. However, the detection of the discharge state is performed by the nozzle that cannot perform normal printing. If the position (number) is recognized by the image processing apparatus, the processing may be performed by another apparatus. In this case, the data of the nozzle position or number where normal printing cannot be performed is transmitted to the image processing device from another device that has detected the ejection state, and stored in a predetermined memory position in the image processing device. It becomes.
[0076]
In the above-described embodiment, a configuration having a print head having one nozzle row will be described. However, in a configuration in which the number of nozzle rows corresponding to the type of ink is used to perform color printing, each nozzle row is used. The processing described in each embodiment is performed on the data to be recorded.
[0077]
The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but may be applied to an apparatus (for example, a copying machine, a facsimile machine, etc.) including one device. May be applied. Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus to store the storage medium. It is needless to say that the present invention can also be achieved by reading and executing the program code stored in the program.
[0078]
In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
[0079]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.
[0080]
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0081]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0082]
When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the above-described flowcharts (shown in FIG. 2 and / or FIG. 8).
[0083]
【The invention's effect】
As described above, according to the present invention, data of neighboring pixels of data of a non-printed pixel determined to be printed by a print element that cannot perform normal printing is different from other pixel data. By performing a process, for example, a process of increasing the number of dots to be printed, it is possible to alleviate a sharp decrease in density caused by the data of the non-printed pixels.
[0084]
Therefore, even when printing is performed using a print head having a print element that cannot perform normal printing, high-quality image printing in which white stripes are suppressed by alleviating a sharp decrease in density caused by data of non-printed pixels. Can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating a process in the image processing apparatus of FIG. 1;
FIG. 3 is a diagram showing a state of scanning of an input image.
FIG. 4 is a diagram showing details of contents stored in a cumulative error memory;
FIG. 5 is a diagram illustrating an image forming process when a nozzle row including a nozzle in a non-printing state is used.
FIG. 6 is a diagram illustrating a process of forming an image by scanning one line of an image line by using one nozzle line;
FIG. 7 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment of the present invention.
FIG. 8 is a flowchart illustrating a process in the image processing apparatus of FIG. 7;
FIG. 9 is a diagram showing a user interface screen for setting a threshold parameter.
[Explanation of symbols]
100 Discharge state detector
101 Non-record raster determination unit
102 Address input terminal
103 Image data input terminal
104 Cumulative error adder
105 Threshold setting unit
106 Quantization unit
107 Error calculation unit
108 Error diffusion unit
109 Accumulated error memory
110 Image data output terminal
700 threshold parameter setting unit
701 monitor

Claims (20)

An image processing apparatus of a recording apparatus that performs recording by moving a recording head having a plurality of recording elements arranged in a predetermined direction relatively to a recording medium,
Determining means for determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording,
Quantization means for converting the input multi-grayscale data of each pixel into data having a smaller number of tones than the number of input tones;
Error diffusion means for diffusing the difference between the input data of the pixel of interest and the data quantized by the quantization means to pixels around the pixel of interest,
The quantizing means determines that the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording by the determining means has a different quantization value from the data of the other pixels. An image processing apparatus for performing a conversion process. 2. The image processing apparatus according to claim 1, wherein the quantization unit further includes a threshold value changing unit that changes a threshold value at the time of quantization for the data of the neighboring pixels. 3. The image processing apparatus according to claim 2, wherein the threshold value changing unit changes the threshold value so that recording dots for the pixels in the vicinity increase. The image processing apparatus according to claim 2, further comprising a user interface for allowing a user to select a parameter used by the threshold value changing unit. 5. The image processing apparatus according to claim 4, wherein the parameters include an application range of the threshold variation process, a threshold variation intensity, and whether or not an input pixel value is referred to when setting a threshold. The image processing apparatus according to claim 2, wherein the threshold value variation unit defines a variation amount of the threshold value with reference to input pixel data. The image processing apparatus according to claim 1, further comprising a detection unit configured to detect a printing element that cannot perform the normal printing. The image processing apparatus according to claim 7, wherein the detection unit detects a printing element that cannot perform the normal printing based on a driving result of each printing element. The image processing apparatus according to claim 7, wherein the detection unit detects a recording element on which normal recording cannot be performed, based on a recording result of each recording element on a recording medium. The printing apparatus according to claim 1, wherein the printing apparatus is a printing apparatus that performs printing by scanning the print head on a print medium in a direction that intersects a direction in which the print elements are arranged. 11. An image processing apparatus as described in the above. The image processing apparatus according to claim 1, wherein the recording head is an inkjet recording head that performs recording by discharging ink. An image processing method for a printing apparatus that performs printing by moving a printing head having a plurality of printing elements arranged in a predetermined direction relative to a printing medium,
A determining step of determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording;
A quantization step of converting the input multi-grayscale data of each pixel into data having a smaller number of gradations than the number of input gradations;
Error diffusion step of diffusing the difference between the input data of the target pixel and the data quantized in the quantization step to pixels around the target pixel,
In the quantization step, the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording in the determination step has a different quantization value from the data of the other pixels. An image processing method comprising performing a conversion process. 13. The image processing method according to claim 12, wherein the quantization step further includes a threshold value changing step of changing a threshold value at the time of quantization for data of the neighboring pixels. 14. The image processing method according to claim 13, wherein, in the threshold value changing step, the threshold value is changed such that recording dots for the neighboring pixels increase. 15. The image processing method according to claim 13, further comprising a user interface for allowing a user to select a parameter used in the threshold changing step. 16. The image processing method according to claim 15, wherein the parameters include an application range of a threshold variation process, a threshold variation intensity, and whether or not an input pixel value is referenced when setting a threshold. 17. The image processing method according to claim 13, wherein in the threshold value changing step, the amount of change in the threshold value is defined with reference to input pixel data. 18. The image processing method according to claim 12, further comprising a detecting step of detecting a recording element that cannot perform the normal recording. A computer program that causes a computer to execute an image processing method of a recording apparatus that performs recording by moving a recording head having a plurality of recording elements arranged in a predetermined direction relative to a recording medium,
A determining step of determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording;
A quantization step of converting the input multi-grayscale data of each pixel into data having a smaller number of gradations than the number of input gradations;
An error diffusion step of diffusing the difference between the input data of the target pixel and the data quantized by the quantization means to pixels around the target pixel, and a program code corresponding to the error diffusion step.
In the quantization step, the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording in the determination step has a different quantization value from the data of the other pixels. A computer program for performing a conversion process. A storage medium storing a computer program for causing a computer to execute an image processing method of a printing apparatus that performs printing by moving a printing head having a plurality of printing elements arranged in a predetermined direction relative to a printing medium. ,
A determining step of determining whether or not the input pixel data is pixel data recorded by a recording element that cannot perform normal recording;
A quantization step of converting the input multi-grayscale data of each pixel into data having a smaller number of gradations than the number of input gradations;
An error diffusion step of diffusing the difference between the input data of the target pixel and the data quantized by the quantization means to pixels around the target pixel, and storing a program code corresponding to the error diffusion step.
In the quantization step, the data of a pixel in the vicinity of a pixel determined to be recorded by the recording element that cannot perform the normal recording in the determination step has a different quantization value from the data of the other pixels. A storage medium for performing a conversion process.

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