JP2004255820A - Image forming device and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which reproduces an image even if the image is difficult to print due to printer characteristics. <P>SOLUTION: The image forming device is comprised of a pattern substitution table 18 which registers therein a pixel arrangement pattern surrounding a target pixel, and a pixel arrangement pattern having a pixel value of the target pixel substituted, in a manner bringing both the patterns into correspondence with each other, by taking the printer characteristics into consideration. Then the pixel arrangement pattern surrounding the target pixel is extracted from image data, and if the extracted pixel arrangement pattern corresponds to the pixel arrangement pattern registered in the pattern substitution table 18, the pixel value of the extracted target pixel is replaced by the pixel value of the target pixel registered in the pattern substitution table, and then an image signal is output. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a multi-function peripheral (hereinafter, abbreviated as MFP), a digital copying machine, a page printer, and the like, and an image forming method.
[0002]
[Prior art]
2. Description of the Related Art Image forming apparatuses such as MFPs, digital copiers, page printers, and the like are connected to a computer directly or via a network, and are also used as a network printer that prints out documents and images edited on the computer on paper. ing.
[0003]
In this case, a printer driver for converting document data such as a document or an image to be printed into a page description language (Page Description Language: PDL) is mounted on the computer side. On the other hand, a raster image processor (Raster Image Processor: hereinafter abbreviated as RIP) for interpreting PDL and converting document data into a raster image composed of a set of dots is mounted on the image forming apparatus side. The RIP reproduces halftone image data using gradation processing such as halftone processing. The halftone processing is a method of expressing shading by an area ratio of a pattern such as a halftone dot or a line. The image data converted (rasterized) into a raster image is printed out on a predetermined sheet by a print engine.
[0004]
Many proposals have been made to improve the print quality of an image printed by such an image forming apparatus. As one of them, there is known an image forming apparatus in which a smoothing table is switched in accordance with a magnification to provide a good image with a smooth contour regardless of resolution (Patent Document 1).
[0005]
[Patent Document 1]
JP-A-8-156326
[Problems to be solved by the invention]
By the way, there is a case where an image of a specific pattern cannot be correctly reproduced due to a printer characteristic.
[0007]
For example, when an attempt is made to print an oblique line having a gentle inclination as shown in FIG. 12B, the straight line may be interrupted as shown in FIG. 12A.
[0008]
Further, when a vertical line is to be printed as shown in FIG. 13 (B), it may be printed thicker than it actually is, as shown in FIG. 13 (A).
[0009]
SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus and a method that can reproduce an image that is difficult to print due to printer characteristics, even if the image is difficult to print. is there.
[0010]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes a pattern replacement table in which a pixel array pattern centered on a pixel of interest in consideration of printer characteristics and a pixel array pattern obtained by replacing the pixel value of the pixel of interest are registered in correspondence with each other. A comparing unit that extracts a pixel array pattern centered on the target pixel from the data and compares the pixel array pattern with a pixel array pattern registered in the pattern replacement table; A replacement unit that replaces the pixel value of the pixel of interest with the pixel value of the pixel of interest registered in the pattern replacement table and outputs an image signal; and an image based on the image signal output from the replacement unit. And an image forming means for forming.
[0011]
According to the image forming method of the present invention, a pixel array pattern centered on a target pixel is extracted from image data, and a pixel array pattern centered on a target pixel and a pixel of the target pixel are determined in consideration of the pixel array pattern and printer characteristics. A comparing step of comparing the pixel array pattern registered in the pattern replacement table registered in correspondence with the pixel array pattern whose value has been replaced, and when both pixel array patterns match by this comparing means, A replacement step of replacing the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputting an image signal; and an image forming an image based on the image signal output from the replacement step. And a forming step.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing a main configuration of an MFP 10 as an example of the image forming apparatus of the present invention. The MFP 10 includes a control panel 11, a main controller 12, a printer controller 13, a scanner 14, a scanner controller 15, a page memory 16, an image processing unit 17, a print engine 19, a pattern replacement table 18, and the like.
[0014]
The control panel 11 includes a key unit and a display unit. In the key section, a numeric keypad for setting the number of prints and the like, a paper selection key for selecting a paper size such as A4, B5, B4, and A3 are arranged. The display section has a display area for the number of prints, paper size, and the like.
[0015]
The main controller 12 inputs and processes the operation key signals from the control panel 11 and controls the data display of the control panel 11. The printer controller 13, scanner controller 15, page memory 16, image processor 17, and print engine 19 are controlled.
[0016]
The printer controller 13 operates as shown in the flowchart of FIG. That is, when receiving original data converted into PDL from a personal computer (hereinafter abbreviated as PC) 20 connected via a network, the RIP interprets the PDL and converts the original data into a raster image. (Step S11). If the document data is a multi-valued image, gradation processing such as halftone processing is performed (at this time, binarization is performed at the same time), and halftones are reproduced (step S12). Thereafter, the rasterized binary image data is stored in the page memory 16 (step S13).
[0017]
The scanner 14 reads image data of a document placed on a document reading table (not shown).
[0018]
The scanner controller 15 binarizes the image data read by the scanner 14 and stores it in the page memory 16.
[0019]
The page memory 16 stores the binary image data sent from the printer controller 13 or the scanner controller 15 for each page. Here, the page memory 16 constitutes storage means.
[0020]
The image processing unit 17 operates as shown in the flowchart of FIG.
[0021]
The image data stored in the page memory 16 is read out one bit at a time under the control of the main controller 12, and an M × N (M, N is a positive number of 2 or more) pixel array pattern centered on the pixel of interest is extracted (step). S21). Then, the M × N pixel array pattern is compared with the pattern registered in the pattern replacement table 18 (step S22). If it is determined in step S22 that the values match, the pixel value of the target pixel is replaced with a pixel value registered in the pattern replacement table 18 (replacement means) (step S23).
[0022]
By the way, if it is determined as “mismatch” in the determination in step S22, the replacement of the target pixel in step S23 is not performed. However, when the pixel of interest is “1” (black), “FF (X)” (255) is output as the pixel value, and when the pixel of interest is “0” (white), “00 (X)” is output as the pixel value. Is done.
[0023]
Then, it is determined whether the pattern comparison has been performed for all the input pixels (step S24).
[0024]
If the determination in step S24 is “NO”, the processing in step S21 and subsequent steps is performed again.
[0025]
If the determination in step S24 is “YES”, the series of processing ends.
[0026]
Incidentally, the pixel value (8 bits) of the target pixel and the reference position are stored in the pattern replacement table 18 corresponding to the M × N (M and N are positive numbers equal to or more than 2) pixel array pattern centered on the target pixel. A signal (2 bits) is registered. Since the target pixel in FIGS. 4B, 5B, and 6B is half-filled, the pixel value is “80”.
[0027]
Here, the image processing unit 17 outputs a signal that has been subjected to pulse width modulation based on the pixel value of the target pixel to the print engine 19 as an image signal.
[0028]
The reference position signal is a signal that specifies where to paint a pixel. For example, if the reference position signal is "0", the filling is designated from the right, if "1", the center is designated, and if the reference position signal is "2", the painting from the left is designated. Note that the reference position signal “4” is not used.
[0029]
For example, when the pixel is painted from the right as shown in FIGS. 4B and 6B, “0” is set as the reference position signal, and the pixel is set as shown in FIG. 5B. Is filled in from the left, “2” is set as the reference position signal.
[0030]
Patterns that are difficult to reproduce due to printer characteristics are registered in the pattern replacement table 18. The detection of a pattern that is difficult to reproduce due to the characteristics of the printer is detected by printing each halftone gradation from the printer in advance.
[0031]
For example, as shown in FIG. 13A, when the vertical line is printed thicker than the actual one shown in FIG. 13B due to the characteristics of the printer, FIGS. 4A and 5A Are registered in the pattern replacement table 18, and when the pixel arrangement pattern matches the input pixel arrangement pattern, the pixel value of the target pixel and the reference position shown in FIG. 4B and FIG. Output a signal.
[0032]
Also, as shown in FIG. 12A, when a slant line having a gentle inclination is printed without interruption due to the characteristics of the printer, the pixel array pattern shown in FIG. If the pixel value matches the input pixel arrangement pattern, the pixel value of the target pixel shown in FIG. 6B is output. In FIGS. 4 to 6, the square with a thick bold line at the center means a target pixel.
[0033]
For example, when the binary image data shown in FIG. 7 is stored in the page memory 16, a 3 × 3 pixel array pattern is extracted from the page memory 19. Since the 3 × 3 pixel array pattern indicated by a1 in FIG. 7 matches the pixel array pattern in FIG. 4A, the pixel array pattern is replaced as b1 in FIG.
[0034]
The pixel array pattern obtained by lowering the 3 × 3 pixel array pattern shown by a1 in FIG. 7 by one pixel also matches the pixel array pattern in FIG. 4A, and is therefore replaced as shown in FIG.
[0035]
Further, since the 3 × 3 pixel array pattern shown by a2 in FIG. 7 matches the pixel array pattern in FIG. 5A, the pixel array pattern is replaced as shown by b2 in FIG.
[0036]
The pixel array pattern obtained by lowering the 3 × 3 pixel array pattern shown by a2 in FIG. 7 by one pixel also matches the pixel array pattern of FIG. 5A, and is therefore replaced as shown in FIG.
[0037]
For example, a pixel array pattern of the upper right 2 × 2 in FIG. 7 and a pixel of the same pattern as the nearest pixel one by one in the upper and left directions are virtually taken as a 3 × 3 pattern. Pattern matching may be performed. The pixels to be added may be simply blank pixels instead of the nearest pixels.
[0038]
As a result, the page memory 16 having the width x of two pixels as shown in FIG. 7 is reduced to the width y of one pixel as shown in FIG.
[0039]
The print engine 19 forms an image based on an image signal from the image processing unit 17 (image forming means), and operates a printing mechanism (not shown) to print out the formed image on paper. Therefore, when vertical lines are printed thicker than usual due to the characteristics of the printer as shown in FIG. 13A, the pattern replacement table 18 should be prepared in advance as shown in FIGS. Accordingly, printing can be performed so as to reproduce an actual thing as shown in FIG.
Also, as shown in FIG. 9, when stored in the page memory 16, a 3 × 3 pixel array pattern is extracted from the page memory 19. Since the 3 × 3 pixel array pattern shown by c1 in FIG. 9 matches the pixel array pattern in FIG. 6A, the pixel array pattern is replaced as shown by d1 in FIG.
[0040]
Further, since the 3 × 3 pixel array pattern shown by c2 in FIG. 9 matches the pixel array pattern in FIG. 6A, the pixel array pattern is replaced as shown by d2 in FIG.
[0041]
Hereinafter, similarly, the pixel array pattern of FIG. 9 is replaced as shown in FIG.
[0042]
Therefore, the portion shown in FIG. 9A overlaps the pixels as shown in FIG. 10B, so even if it is a gentle oblique line, it is interrupted as shown in FIG. Printing can be performed without interruption.
[0043]
In the above-described embodiment, halftone processing using a dither matrix has been described. However, the present invention is not limited to this, and it is also possible to use error diffusion as halftone processing or to perform gradation processing using other methods. Needless to say, apply.
[0044]
Note that the pattern replacement table 18 may be formed in, for example, an EEPROM chip that is detachable from the MFP 1 so that data can be exchanged as needed.
[0045]
In the above-described embodiment, the pattern replacement table 18 has one pixel of interest, but may have two pixels as indicated by the thick line in FIG. FIG. 11A shows a pixel array pattern before replacement, and FIG. 11B shows a pixel array pattern after replacement.
[0046]
Note that the image forming apparatus of the present invention is not limited to the MFP 1, but is also applicable to a digital copying machine, a page printer, and the like. The same image forming method is applied not only to the document data received from the PC 20 but also to the image data of the document read by the scanner 14.
[0047]
【The invention's effect】
As described above in detail, according to the present invention, an image forming apparatus and method capable of reproducing an image because the pattern is replaced even in an image that is difficult to print due to printer characteristics are provided. be able to.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of an MFP according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining processing contents of a printer controller according to the embodiment;
FIG. 3 is a flowchart for explaining processing contents of an image processing unit according to the embodiment;
FIG. 4 is an exemplary view showing an example of a pattern registered in a pattern conversion table according to the embodiment;
FIG. 5 is an exemplary view showing an example of a pattern registered in a pattern conversion table according to the embodiment;
FIG. 6 is an exemplary view showing an example of a pattern registered in a pattern conversion table according to the embodiment;
FIG. 7 is a view showing a pattern before pattern conversion according to the embodiment;
FIG. 8 is a view showing a pattern after pattern conversion according to the embodiment;
FIG. 9 is a view showing a pattern before pattern conversion according to the embodiment;
FIG. 10 is a view showing a pattern after pattern conversion according to the embodiment;
FIG. 11 is a view for explaining pattern replacement processing when there are two target pixels.
FIG. 12 is a diagram for explaining a conventional problem and an effect of the present invention.
FIG. 13 is a diagram for explaining a conventional problem and an effect of the present invention.
[Explanation of symbols]
10 MFP, 11 control panel, 12 main controller, 13 printer controller, 14 scanner, 15 scanner controller, 16 page memory, 17 image processing unit, 18 pattern replacement table, 19 print engine.

Claims (7)

A pattern replacement table in which a pixel array pattern centered on a pixel of interest in consideration of printer characteristics and a pixel array pattern obtained by replacing the pixel value of the pixel of interest are registered,
A comparing unit that extracts a pixel array pattern centered on the target pixel from the image data, and compares the pixel array pattern with a pixel array pattern registered in the pattern replacement table;
When both patterns match by the comparing unit, a replacing unit that replaces the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputs an image signal;
An image forming apparatus comprising: an image forming unit that forms an image based on an image signal output from the replacing unit. A pattern replacement table in which a pixel array pattern centered on the pixel of interest in consideration of the printer characteristics and a pixel array pattern obtained by replacing the pixel value of the pixel of interest are registered,
Means for binarizing the page description language by rasterizing, halftone processing, etc .;
Storage means for storing binary image data output from the processing means;
Comparing means for extracting a pixel array pattern centered on the pixel of interest from the binary image data stored in the storage means, and comparing the pixel array pattern with a pixel array pattern registered in the pattern replacement table; ,
When both pixel arrangement patterns match by the comparing unit, a replacing unit that replaces the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputs an image signal;
An image forming apparatus comprising: an image forming unit that forms an image based on an image signal output from the replacing unit. A pattern replacement table in which a pixel array pattern centered on a pixel of interest in consideration of printer characteristics and a pixel array pattern obtained by replacing the pixel value of the pixel of interest are registered in correspondence with each other;
Means for binarizing the page description language by rasterizing, halftone processing, etc .;
Storage means for storing binary image data output from the processing means;
An M × N pixel array pattern centered on the pixel of interest is extracted from the binary image data stored in the storage unit, and this pixel array pattern is compared with the pixel array pattern registered in the pattern conversion table. Means for comparing,
When both pixel arrangement patterns match by the comparing unit, a replacing unit that replaces the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputs an image signal;
An image forming apparatus comprising: an image forming unit that forms an image based on an image signal output from the replacing unit. In the pattern replacement table, a pixel value of the target pixel and a reference position signal indicating a position from which the pixel is to be filled are registered. The replacement unit outputs a signal that is pulse-width modulated based on the pixel value of the target pixel. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus outputs a reference position signal to the image forming unit. A pixel array pattern centered on the target pixel is extracted from the image data, and a pixel array pattern centered on the target pixel and a pixel array pattern obtained by replacing the pixel value of the target pixel in consideration of the pixel array pattern and the printer characteristics. A comparison step of comparing a pixel array pattern registered in a pattern replacement table registered in correspondence with
When both the pixel arrangement patterns match by the comparing means, a replacement step of replacing the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputting an image signal;
An image forming step of forming an image based on the image signal output from the replacing step. A processing step of binarizing the page description language by rasterizing, halftone processing, or the like, and storing the binary image data in a storage unit;
A pixel array pattern centered on the pixel of interest is extracted from the binary image data stored in the storage unit, and a pixel array pattern centered on the pixel of interest and the pixel of interest are extracted in consideration of the pixel array pattern and printer characteristics. A comparing step of comparing a pixel array pattern registered in a pattern replacement table registered in correspondence with a pixel array pattern obtained by replacing the pixel value of
When the two pixel arrangement patterns match in the comparison step, a replacement step of replacing the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputting an image signal;
An image forming step of forming an image based on the image signal output from the replacing step. A processing step of binarizing the page description language by rasterizing, halftone processing, or the like, and storing the binary image data in a storage unit;
An M × N pixel array pattern centered on the target pixel is extracted from the binary image data stored in the storage means, and a pixel array pattern centered on the target pixel is taken into consideration in consideration of the pixel array pattern and printer characteristics. A comparison step of comparing the pixel array pattern registered in the pattern conversion table registered in correspondence with the pixel array pattern obtained by replacing the pixel value of the pixel of interest with the pixel array pattern;
When the two pixel arrangement patterns match in the comparison step, a replacement step of replacing the pixel value of the target pixel with the pixel value of the target pixel registered in the pattern replacement table and outputting an image signal;
An image forming means for forming an image based on the image signal output from the replacing step.

Images