JP2002135581A - Image binary processing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image binary processing circuit that causes no discontinuous gray scale even when applying skew correction to an image. SOLUTION: The image binary processing circuit is provided with a threshold storage means 2 that stores thresholds used to device with which of two logical values multi-value image data are to be replaced, a correction position designation means 5 that designates a correction position at which image distortion is to be corrected, a threshold read means 3 that designates a read address of the thresholds and varies the read address of the thresholds on the basis of the correction position information from the correction position designation means 5, and a data comparison means 4 that compares the read thresholds with a level of the image data and outputs either of the two logical values depending on the comparison result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image binarizing circuit for replacing multi-valued image data with one of two logical values.

[0002]

2. Description of the Related Art A conventional image binarizing circuit replaces multi-valued image data with two logical values, that is, "logical 1 (place dots)" or "logical 0 (does not place dots)".
Threshold value storage means for storing a threshold value for determining whether to replace the threshold value, threshold value read means for specifying a read position of the threshold value, and comparing the read threshold value with the size of image data, Data comparing means for outputting "logic 1" or "logic 0" from the result. Hereinafter, these operations will be described.

For example, 8 bits per pixel, that is, 2 bits
The multi-valued image data expressed in 56 gradations is 64
There is image data constituting an image for one color by arranging two pixels two-dimensionally with 0 pixels and 480 pixels in the vertical direction. The image data thus configured is yellow (hereinafter, referred to as “Y”), magenta (hereinafter, referred to as “M”), and cyan (hereinafter, “C”).
It is written. ) And black (hereinafter, referred to as “K”) for one plane, so that one color image can be expressed. As means for expressing this color image in two values of "place color" and "place no color" per color, that is, one bit, a conventional image binarization circuit performs the following processing.

First, image data expressed by 8 bits per pixel per color is compared with a certain threshold value (for example, 128). Put), and when the level is smaller than the threshold value, it is set to “0 (no color is put)”. Threshold values having different values, for example, four in the horizontal direction and four in the vertical direction are stored side by side, and a total of 16 threshold values are stored. By comparing the threshold value with the threshold value of the vertical and horizontal base points (for example, upper left),
The binary data of the base point is obtained.

Next, the multivalued image data on the right side of one pixel of the processed pixel is compared with the threshold value on the right side of one of the threshold values used in the previous processing, and Is obtained. Such processing is performed while shifting one pixel at a time in the right and left direction. If four horizontal thresholds are cycled, the threshold used in the first processing is used again. When the multi-valued image data for 640 pixels in the horizontal direction can be binarized in this way, the processing of the multi-valued image data and the threshold value is shifted down by one pixel in the vertical direction, and the same processing is repeated. In this way 1
Binarize multi-valued image data for each color.

[0006] The above-mentioned conventional technique is, for example, a monochrome electrophotographic printer that forms and fixes a toner image by performing a single development process with a pair of laser scanning units (hereinafter, referred to as “LSU”) and a developing device. Alternatively, a color electrophotographic printer that forms four CMYK images using a pair of LSUs and a developing device, that is, a C developing process is performed, an image is formed, and a C toner image is temporarily formed on another transfer body. After that, the same developing device performs M, Y, and K development processes in the same manner, and a color image is formed and fixed by transferring each toner image onto a transfer body. Used.
Thereby, the input multi-valued image data is binarized,
Image data suitable for the output characteristics of the electrophotographic printer can be obtained. As a result, a halftone image can be expressed by a printer that can basically only express a binary image (whether to put or not put a color).

[0007]

There is a tandem type printer which is advantageous for high speed printing in an electrophotographic printer. In this method, for example, C, M, Y, and K images are simultaneously developed by four pairs of LSUs and a developing device, and the respective color toner images are transferred to a transfer body by aligning the respective color images to form a color image. And settle.

A tandem type electrophotographic printer is
The accuracy of registration (registration) of each image formed by a plurality of different pairs of LSUs and the developing unit affects the printing result of the image. That is, the angle deviation of the rotation axis of the photosensitive drum in the image forming portion of the printer, and L
A positional shift in the oblique direction (hereinafter, referred to as “skew”) occurs due to a mounting angle shift between the SU and the scanning optical system such as the developing device. The displacement of the image forming positions of the four colors transferred to the transfer member eventually appears as a displacement or a change in color tone.

FIG. 8 is a diagram showing an example in which skew has occurred in an image. FIG. 3A shows an image without skew, FIG. 3B shows an image with skew rising to the right, and FIG.
Is an image having a skew falling to the right. In FIG. 8, A indicates a direction in which an image is formed by the LSU. For this reason, a tandem type electrophotographic printer may be provided with a means for correcting a skew of an image.

Hereinafter, an example of a means for correcting a skew of an image will be described. FIG. 9 is a configuration diagram of a conventional image skew correction device, FIG. 10 is a configuration diagram of a conventional skew correction unit,
FIG. 11 is a diagram illustrating an example in which an image having a skew that rises to the right is corrected by a conventional image skew correction device. The skew correction means 40 includes a shift position setting means (or a shift point setting means) 41 for setting a shift position of image data based on a shift amount due to a preset skew.
And a shift direction setting means 42 for indicating the direction in which skew is occurring. The skew correction means 40
As shown in FIG. 10, image data before correction is input and stored, a data storage unit 50 for storing the image data, a shift position (shift point) output from the shift position setting unit 41, and a shift direction setting unit 42. And a data correction unit 51 for shifting an image in accordance with the shift direction output from the CPU.

The skew correction device configured as described above divides a plurality of images in the vertical direction and shifts the divided images in the vertical direction to obtain an image having no apparent inclination. Works like First, the image data before being corrected is stored in the data storage unit 50. The amount of data stored is equal to or greater than the number of lines to be shifted by the correction.

The data once stored is stored in a data correction means 5.
1, the image data read position is switched for each shift position in accordance with the shift position information from the shift position setting means 41 and the shift direction information from the shift direction setting means 42. In FIG. 11, A indicates a direction in which an image is formed by the LSU. The image data of each line read from the data correction unit 51 is corrected so that the read position is shifted down by one line at the positions a, b, and c so that there is no apparent inclination.

However, when the image is shifted line by line by the skew correction, a discontinuity in density occurs in the halftone image formed by the conventional image binarization circuit. FIG. 12 is a diagram showing an image of a halftone pattern having a skew in the conventional image skew correction device. FIG. 12A shows a density 50 formed by a conventional image binarization circuit.
5 is an image of a halftone pattern of%. A white or black square in the figure corresponds to one pixel. FIG. 3B shows the image shifted downward by one pixel at the position A by the skew correction. The shape of the halftone pattern changes at the skew-corrected position A as described above, but when viewed macroscopically, it looks like an image of uniform intermediate density has vertical lines.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a binarizing circuit for an image in which a density discontinuity does not occur even if the image is skew-corrected. .

Also, the present invention provides an image binary method for making a specific image pattern appearing when skew correction of an image is performed, for example, an image pattern in which a horizontal straight line becomes a discontinuous straight line at a skew correction position inconspicuous. It is an object to provide a conversion circuit.

[0016]

In order to solve this problem, an image binarizing circuit according to the present invention stores a threshold value for determining which of two logical values is to replace multi-valued image data. Threshold value storage means, correction position specification means for specifying a correction position for correcting image distortion, readout position of the threshold value, and the threshold value based on correction position information from the correction position specification means. Threshold reading means for making the reading position of the value variable, and comparing the read threshold with the size of the image data, and outputting one of the two logical values from the result. Means.

Thus, even if the image is shifted line by line by skew correction, the position and direction in which the image data is shifted can be known in advance by skew correction by the correction position specifying means. Then, the threshold read-out means which makes the read-out position of the threshold variable can change the threshold read-out position at the position where the image data is shifted by the skew correction by one line in the direction opposite to the shift direction of the skew correction. Can be shifted. As a result, even if the image is shifted line by line by the skew correction, the image can be binarized so that the shape of the halftone pattern of the image does not change.
Even when viewed macroscopically, it is possible to prevent discontinuity from occurring in the density of the image.

Further, the image binarizing circuit of the present invention has a specific image pattern detecting means for detecting a specific image pattern appearing as a result of correcting the distortion of the image, and the threshold value reading means comprises: In this configuration, the readout position of the threshold value can be changed by image pattern detection information.

Thus, a specific image pattern appearing at the skew correction position can be detected by the specific image pattern detecting means, and a predetermined pattern is generated in order to generate a binarized pattern that makes this image pattern inconspicuous based on the detected information. Since the threshold value can be read out by the threshold value reading means, a specific image pattern appearing at the skew correction position can be made inconspicuous.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that threshold value storage means for storing a threshold value for determining which of two logical values is to be replaced with multi-valued image data,
A correction position specifying means for specifying a correction position for correcting image distortion, a threshold reading position, and a variable threshold reading position based on correction position information from the correction position specifying means. An image binarization circuit having a threshold reading unit and a data comparing unit that compares the read threshold value and the size of the image data and outputs one of two logical values from the result. Even when skew correction of an image is performed by a tandem type electrophotographic printer, the threshold reading position at the position where the image data is shifted can be shifted by one line in the direction opposite to the skew correction shift direction. Having.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a specific image pattern detecting means for detecting a specific image pattern appearing as a result of correcting the distortion of the image, The reading means is an image binarization circuit which makes a reading position of a threshold variable according to specific image pattern detection information, and detects a specific pattern appearing at a position where image data is shifted when performing skew correction of an image. In addition, the reading position of the threshold value used in the binarization is changed, so that even when skew correction of the image is performed, there is an effect that a discontinuous portion does not occur in the density of the image.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

(Embodiment 1) FIG. 1 is a block diagram of an image binarization circuit according to an embodiment of the present invention, and FIG.
FIG. 3 is a functional block diagram of a printer using an image binarizing circuit according to an embodiment of the present invention. FIG. 3 is a configuration diagram of a printer engine mechanism of a tandem-type electrophotographic printer according to an embodiment of the present invention. . A process in which print data is sent from a host computer and a printer prints an image will be described with reference to these drawings.

In FIG. 1, an image binarization circuit 1 replaces multi-valued image data with two logical values, that is, "logical 1 (place dots)" or "logical 0 (does not place dots)". Threshold value storage means 2 for storing a threshold value for determining whether to replace the image, correction position specification means 5 for specifying a correction position for correcting image distortion, readout position of the threshold value, and correction position specification The threshold reading means 3 which makes the reading position of the threshold variable according to the correction position information from the means 5 is compared with the read threshold and the size of the multi-valued image data 6. Data comparing means 4 for outputting any one of the binary image data 7 of logical values.

In FIG. 2, the tandem type electrophotographic printer 10 includes a printer controller 20 and a printer engine 23. The printer controller 20 includes a data receiving unit 21 that receives print data 27 output from the host computer 26, an image generating unit 22 that generates binary or multi-valued image data from the received print data, Image binarizing circuit 1 shown in FIG. 1 for converting data into binary image data 7
It is composed of The printer engine 23 includes a printer engine mechanism unit 25, a printer engine control unit 24 that controls the same, and a skew correction unit 8 that corrects image skew. Printer engine control unit 2
Reference numeral 4 denotes a configuration in which the skew amount 9 of the image can be passed to the image binarization circuit 1.

First, the host computer 26 generates print data 27 to be printed and outputs it to the printer 10. Here, the print data 27 is PCL (Prin
ter Control Language) or PS
(Post Script) and GDI (Graphic)
al Device Interface), and is composed of a print image description language such as an IEEE 1284 interface of the host computer 26 or a USB.
(Universal Serial Bus) interface, network interface (neither is shown), or the like.

The data receiving section 21 has a print data 27
And temporarily accumulates it in a memory (not shown) inside the printer controller 20. The image generation unit 22 analyzes the print data on the memory, and performs CMYK4
Generate binary or multi-valued image data for each color. Since the electrophotographic printer engine 23 cannot directly print multivalued data, the multivalued image data generated by the image binarization circuit 1 is converted into binary image data 7 in which dots are not placed. Convert. The method of converting multi-value data into binary data is as described in the related art.

The printer engine 23 first corrects the binary image data 7 with the skew correction unit 8 in order to correct the skew caused by the mechanical displacement of the printer engine mechanism 25. The skew correction is the same as that described with reference to FIG. The printer engine control unit 24 controls the printer engine mechanism unit 25 to transfer the skew-corrected binary image data to a sheet (not shown) and output it.

Here, the process of outputting an image by the printer engine 23 will be described in detail with reference to FIG. 3, four image stations 81a, 81b, 81c and 81d are arranged in the printer engine mechanism 25, and the image stations 81a, 81b, 81c and 81d are photosensitive drums 82a, 82b and 82c as image carriers. ,
82d.

Then, a dedicated charging means 83 is provided therearound.
a, 83b, 83c, 83d, developing means 84a, 84
b, 84c, 84d, cleaning means 85a, 85
b, 85c, 85d, and exposure means 86a, 86b, 86c of a scanning optical system for irradiating each photosensitive drum with light corresponding to image data output from the skew correction unit 8.
86d, transfer units 88a, 88b, 88 in the transfer means 87
c and 88d are arranged respectively.

Here, the image stations 81a, 81
b, 81c, and 81d form yellow, magenta, cyan, and black images, respectively. The exposure units 86a, 86b, 86c, and 86d correspond to yellow, magenta, cyan, and black images, respectively. Lights 89a, 89b, 89c, and 89d are output. Each of the image stations 81a, 81b, 81c,
81d, the photosensitive drums 82a, 82
Below rollers b, 82c and 82d, rollers 810 and 811
Belt-like intermediate transfer belt 812 supported by
Is arranged, and moves in the direction of arrow A. These operations are controlled by the printer engine control unit 24. Also,
Sheet material 816 stored in paper feed cassette 815
Is fed by a paper feed roller 817, and is discharged to a discharge tray (not shown) via a sheet material transfer roller 818 and a fixing unit 819.

In the above configuration, first, the charging means 83d and the exposure means 8 of the image forming station 81d are used.
After forming a latent image of the black component color of the image information on the photosensitive drum 82d by a known electrophotographic process means such as 6d, it is visualized as a black toner image by a developing material having black toner by a developing means 84d. , Transfer unit 8
At 8d, the black toner image is transferred to the intermediate transfer belt 812.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 812, the image forming station 8
1c, a latent image of a cyan component color is formed,
c, a cyan toner image of cyan toner is obtained, transferred by the transfer device 88c, and superimposed on the black toner image previously transferred on the intermediate transfer belt 812.

Hereinafter, image formation is performed in the same manner for the magenta toner image and the yellow toner image. When the superimposition of the four color toner images on the intermediate transfer belt 812 is completed, the four-color toner image is transferred onto the sheet material 816 such as the paper fed from the paper feed cassette 815 by the paper feed roller 817 by the sheet material transfer roller 818. The color toner images are collectively transferred and conveyed, and are heat-fixed by the fixing unit 819, so that a full-color image is obtained on the sheet material 816. Each of the photoreceptor drums 82a, 82b, 82 after the transfer is completed.
c and 82d are cleaning means 85a, 85b and 85
At c and 85d, the residual toner is removed, and the printing operation is completed in preparation for the next image formation to be performed subsequently.

Here, each image station 81a, 81
b, 81c, 81d and exposure means 86a, 8 of the scanning optical system.
6b, 86c, 86d and the transfer means 87 each have a mechanical mounting error. Therefore, at the time of assembling and adjusting the equipment, the skew is measured from the output image, the shift amount is obtained, and the skew correction unit 8 performs skew correction. The skew correction method is the same as that of the related art, and thus the description is omitted. Although the skew on the print image is corrected by the skew correction unit 8, the halftone pattern is deformed at the skew correction position in the conventional image binarization circuit as shown in FIG.

In order to prevent this, the binarizing circuit of the present invention is configured as shown in FIG. The specific implementation method and operation of each means in FIG. 1 will be described with reference to FIGS. 4, 5, 6, and 7. FIG. FIG.
FIG. 5 is a configuration diagram of a threshold value storage unit and a data comparison unit of the image binarization circuit according to one embodiment of the present invention. FIG. 5 is a diagram showing a threshold value of the image binarization circuit according to one embodiment of the present invention. FIG. 6 is a diagram illustrating a configuration of a reading unit, FIG. 6 is a diagram illustrating a storage state of threshold values of an image binarization circuit according to an embodiment of the present invention, and FIG. FIG. 6 is a diagram illustrating a comparison positional relationship between a circuit threshold value and multi-valued image data.

The threshold value storage means 2 is a 32 k word × 8 bit memory 91 shown in FIG. 4, and the data comparison means 4 is composed of a comparator 92 having two 8-bit width data inputs.
The threshold reading means 3 is constituted by the circuit shown in FIG. That is, a 3-bit counter 100 having the same period as the image data output period for one pixel, having a data load function using a clock 105 synchronized with image data as a clock input, and having an enable control function, and being connected to the load data input of the counter 100 Then, the register 101 for storing the address initial value in the X direction, the register 102 for storing the address reset position in the X direction, and the output value 90x of the counter 100 are compared with the value of the register 102.
04 and a comparator 103 connected to the load input of the counter 100.

Further, the counter 100 and the counter 1
Enable signal 10 connected to the enable input 07
And an exposure means 8 of the printer engine 23 in an output period H for one line of an image.
A 2-bit counter 107 having the same cycle as 6a, 86b, 86c, 86d and having a data load function and an enable control function using a clock 113 synchronized therewith as a clock input, and a register 108 for storing an initial address value in the Y direction. , And an adder / subtractor 109 connected to the load data input of the counter 107.

Further, a register 110 for storing an address reset position in the Y direction and an output value 9 of the counter 107 are provided.
0y and the value of the register 110, and the result 112 is compared with the comparator 111 connected to the load input of the counter 107.
And a 14-bit counter 114 that counts the clock 105 and is reset by the clock 113, and a correction position storage register 115 that stores the correction position and correction direction of the skew obtained from the amount of deviation measured during the assembly adjustment of the device.
, And compares the value of the register 115 with the value of the counter 114, and outputs an addition / subtraction value to the adder / subtractor 109 and the counter 107.
And a Y-direction address counter circuit comprising an addition / subtraction designation circuit 116 for designating addition / subtraction to the address.

The operation of the binarization circuit configured as described above will be described. As shown in FIG. 4, the threshold value 93 is stored in the memory 91, and by giving the address 90, the corresponding threshold value having an 8-bit width is read out. Threshold 9
Numerals 3 are arranged in a grid pattern with respect to the addresses as shown in FIG. The threshold value 93 and the 8-bit multi-valued image data 6 to be binarized are compared by a comparator 92, and the multi-valued image data 6
Is greater than or equal to the threshold value 93, and 1 is obtained as the binary image data 7 when it is smaller.

The address 90 given to the memory 91 is
As shown in FIG. 5, it is composed of an X direction address 90x output from the X direction counter 100 and a Y direction address 90y output from the Y direction counter 107. X, Y counter 10
Operations 0 and 107 are started by the counter operation enable signal 106 at the timing when the printer engine 23 needs the binary image data. The counter operation enable signal 106 is generated by the printer engine control unit 24. The X direction counter 100 outputs the value of the X direction initial value storage register 101 as an initial value.

Thereafter, the count is incremented in synchronization with the clock 105, and when the count is equal to the value of the X-direction reset position storage register 102, the comparator 103 outputs a match signal 104. The X-direction counter 100 outputs the coincidence signal 10
4, the value of the X direction initial value storage register 101 is loaded again and output to the X direction address 90x. The Y direction counter 107 adds the value of the Y direction initial value storage register 108 and the value from the addition / subtraction designation circuit 116 to the addition / subtraction unit 10.
In step 9, the value is added or subtracted, and the value is output as an initial value.

Thereafter, the count is incremented in synchronization with the clock 113, and when the count matches the value of the Y-direction reset position storage register 110, the comparator 111 outputs a match signal 112. The Y-direction counter 107 outputs the coincidence signal 11
2, the value of the Y direction initial value storage register 108 and the value from the addition / subtraction designation circuit 116 are added or subtracted again.
The value is loaded and output to the Y-direction address 90y.

The pixel counter 114 counts up the number of pixels in the X direction in synchronization with the clock 105, and resets it during the L period of the clock 113. When the value of the pixel counter 114 matches the skew correction position in the correction position storage register 115, the addition / subtraction designation circuit 116 specifies addition or subtraction and the amount of addition or subtraction according to the correction direction in the correction position storage register 115. To Y-direction counter 1
07 and to the adder / subtractor 109.

By the above operation, the comparison positional relationship between the threshold value and the multi-valued image data is as shown in FIG. That is, the pixels constituting the image are two-dimensionally arranged as shown in FIG. 7, and the point S is the base point at the upper left of the image. The multi-valued image data at the point S is compared with a threshold value from a storage position of the memory 91 determined by the initial address of the X direction counter 100 and the Y direction counter 107 (for example, the position of the X direction address 0 and the Y direction address 0 in FIG. 11). And binarized. When the multi-valued image data is sequentially output in the X direction in FIG. 7 in synchronization with the clock 105, the Y direction address of the threshold table in FIG. It is sequentially increased and compared with a threshold determined by the address.

Thereafter, when the X-direction address coincides with the reset position determined by the X-direction reset position storage register 102 in FIG. 5, the operation returns to the initial value, and the same operation is repeated in a section where there is no skew correction thereafter. When the position of the pixel to be binarized matches the correction position set in the correction position storage register 115, the Y-direction address increases in the direction opposite to the skew correction direction, that is, when the image shifts upward in the paper. If the image shifts downward in the direction of the paper, the Y-direction counter 1
07 is controlled.

FIG. 7 shows a case where the skew correction direction is the paper upward direction, and the A line is the control point. Thereafter, with the Y-direction address increasing or decreasing, only the X-direction address repeats the increase and reset as described above. When the comparison between the multi-valued image data for one line and the threshold value is completed, the Y-direction address is incremented by 1, and the comparison between the multi-valued image data for the next line and the threshold value is performed in the same manner as described above.

As described above, the same processing is repeated until all the lines are binarized. By this processing, the position of the threshold value for the pixel on the sheet is shifted in the Y direction at the line A in FIG. 7, that is, the skew correction position. A thick frame B in FIG. 7 shows the threshold values in the same arrangement as the threshold value table.

As described above, the comparison positional relationship between the threshold value and the multi-valued image data is as shown in FIG. 7. However, since the actually printed image is shifted upward on the sheet by the A line, the halftone pattern There is no discontinuity in the shape, and no discontinuity occurs in the image density even when viewed macroscopically.

(Embodiment 2) When skew correction of an image is performed, a specific pattern appearing at a position where image data is shifted, for example, a horizontal straight line becomes a discontinuous straight line at the skew correction position as shown in FIG. In order to detect the changed image pattern, the multi-valued image data is input to and held in a window circuit composed of four horizontal pixels and four vertical pixels. This window circuit is a known circuit, and can be constituted by a memory or a register. Each pixel of the above window circuit is
Each pixel of a register group including four horizontal pixels and four vertical pixels holding a plurality of specific image patterns to be detected is compared by a comparator.

When all the pixels of the register holding the specific image pattern and all the pixels of the window circuit match and the image data in the window circuit is at the skew correction position of the image, the specific image pattern is It is determined that it has been detected. This determination circuit can be realized by inputting a comparison output whose output becomes 1 when the pixel counter 114 and the correction position storage register 115 in FIG.

When a specific image pattern is detected, an offset is added to an address 90 given to a 32 k word × 8 bit memory 91 storing a threshold value. Specifically, the highest bit of the address 90 is changed from 0 to 1, and the threshold read position is changed. This address stores a threshold value for generating a binarized pattern that makes discontinuous portions of a specific image pattern inconspicuous. As a result, when the specific image pattern is detected at the skew correction position, the threshold value of the binarized pattern that makes the discontinuous portion of the specific image pattern inconspicuous can be read, and the skew correction position can be read. Discontinuous portions of the image can be made inconspicuous.

[0053]

As described above, according to the present invention, even if the image is shifted in the vertical or horizontal direction due to the skew correction of the image or the like, the threshold value for binarization is determined in advance by the shift direction of the image. Can be binarized by being shifted in the opposite direction, so that an effective effect of preventing a discontinuous portion from being generated in the halftone pattern shape due to the image shift can be obtained.

Further, according to the present invention, since a specific image pattern appearing at the skew correction position can be detected, there is an effect that it can be binarized so as to make it inconspicuous. An effective effect of being able to obtain is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image binarization circuit according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of a printer using an image binarizing circuit according to an embodiment of the present invention;

FIG. 3 is a configuration diagram of a printer engine mechanism of a tandem type electrophotographic printer according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a threshold value storage unit and a data comparison unit of the image binarization circuit according to one embodiment of the present invention;

FIG. 5 is a configuration diagram of threshold reading means of the image binarization circuit according to one embodiment of the present invention;

FIG. 6 is a diagram showing a storage state of a threshold value of the image binarization circuit according to one embodiment of the present invention;

FIG. 7 is a diagram illustrating a comparison positional relationship between a threshold value of an image binarization circuit and multi-valued image data according to an embodiment of the present invention;

FIG. 8 is a diagram illustrating an example in which skew has occurred in an image.

FIG. 9 is a configuration diagram of a conventional image skew correction device.

FIG. 10 is a configuration diagram of a conventional skew correction unit.

FIG. 11 is a diagram showing an example in which an image having a skew that rises to the right is corrected by a conventional image skew correction device.

FIG. 12 is a diagram showing an image of a halftone pattern having skew in a conventional image skew correction device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image binarization circuit 2 Threshold storage means 3 Threshold reading means 4 Data comparison means 5 Correction position designation means 6 Multivalued image data 7 Binary image data 10 Tandem type electrophotographic printer 20 Printer controller 21 Data Receiver 22 Image generator 23 Printer engine 24 Printer engine controller 25 Printer engine mechanism 26 Host computer 27 Print data

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2C262 AB05 AB13 AB15 BB03 BB06 BB14 BB22 CA13 EA04 GA04 GA11 5B057 AA11 BA29 CA08 CA12 CA16 CB07 CB12 CB16 CC02 CD12 CE12 CH11 CH18 DA17 DB02 DB08 DC01 5C077 LL02 PQ20PP55 PP55 RR02 RR16 TT03

Claims (2)

[Claims] 1. A threshold value storing means for storing a threshold value for determining which of two logical values to replace multi-valued image data, and a correction position specifying means for specifying a correction position for correcting image distortion. Threshold reading means for designating a reading position of the threshold value, and making the reading position of the threshold variable by correction position information from the correction position designating means; and the read threshold value And a data comparing means for comparing the size of the image data and outputting one of the two logical values from the result. 2. The image processing apparatus according to claim 1, further comprising: a specific image pattern detecting unit configured to detect a specific image pattern appearing as a result of correcting the distortion of the image, wherein the threshold value reading unit sets the threshold value based on the specific image pattern detection information. 2. The image binarization circuit according to claim 1, wherein a readout position is variable.