JPH09270915A - Image processing method and image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a direction effective for improving picture quality, in accordance with resolution and to shorten processing time by independently executing a correction processing with a first correction direction and a second correction direction orthogonal to the first direction against recording dots. SOLUTION: A control part 5 stores bit map picture data and recording direction data from a host computer in to a bit map memory 6 and a recording direction indication memory 7. A template for shaggy detection corresponding to a recording direction is set in a pattern memory 9. Bit map data in prescribed size is segmented from the memory 6, in accordance with the recording direction, is supplied to a comparison buffer 8 and is compared with the template for shaggy detection. When they match, the control part 5 reads smoothing correction data changing the size or the position of the recording dots from a correction memory 10, in accordance with the recording direction, adds it to image data existing in the comparison buffer 8 and stores it in a smoothing memory 11. When they do not match, image data is stored without correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing apparatus, and more particularly to an image processing method and an image processing apparatus for correcting a dot diameter or a dot position according to a dot pattern.

A laser printer used as an image forming apparatus is currently a 600 dpi model. 6
The model having a resolution of 00 dpi has about half the resolution of 1200 dpi, which is said to be the visual limit of humans, and has a good evaluation. However, jagged characters called jaggies are detected in characters and graphics having smooth curved portions, and improvement is desired. To remedy this drawback, increase the pixel density. However, if you simply increase the pixel density,
As the engine becomes more accurate, the cost of the printer increases, the time for transferring the pit map with high resolution increases, and the convenience is impaired.

Therefore, there has been a demand for an image processing method capable of efficiently improving the image quality without increasing the resolution.

[0004]

2. Description of the Related Art Conventionally, as an image processing method capable of improving image quality at a high speed without increasing the resolution, conventionally, the length of time of turning on and off the laser beam and the timing of starting the laser beam which determine the resolution in the main scanning direction are delicate. There was a method to control it to increase the resolution artificially.

FIG. 19 is a block diagram of a conventional example, and FIGS. 20 and 21 are operation explanatory diagrams of the conventional example. The image data to be recorded is expanded in the bitmap memory 400. The data expanded in the bitmap memory 400 is
It is supplied to the smoothing processing unit 401.

The smoothing processing unit 401 includes a comparison data buffer 402, a template pattern memory 403,
It is composed of a recording size memory 404, a recording position memory 405, and a smoothing memory 406. The comparison data puffer 402 extracts and stores a predetermined sample window from the digital image data stored in the pit map memory 400.

In the template pattern memory 403,
An image pattern that causes jaggies is held in advance.
The recording size memory 404 stores the size of the correction pixel according to the template pattern. Further, the recording position memory 405 stores the position data of the correction pixel corresponding to the template pattern.

The smoothing memory 406 stores the corrected pixel value. The sample window stored in the comparison data buffer 402 is compared with the template pattern stored in the template pattern memory 403, and if there is a matching template, the pixels stored in the recording size memory 404 according to the matching template pattern. Is set to the position stored in the recording position memory 405 and stored in the smoothing memory.

The data stored in the smoothing memory 406 is supplied to the image forming section 407. Image forming unit 40
7 is mainly a laser drive driver 408 and a laser light source 4.
09 and a photosensitive drum 410. The laser drive driver 408 is driven according to the data stored in the smoothing memory 406, and the laser light source 409 generates laser light according to the data. The laser light generated from the laser light source 409 scans and irradiates the photosensitive drum 410 to form an electrostatic latent image on the photosensitive drum 410.
Toner is supplied from the developing device to the electrostatic latent image formed on the photosensitive drum 410 to form a toner image.

The toner image is transferred onto the recording paper by the transfer device. The toner is fixed on the recording paper on which the toner image is transferred by the fixing device, and the image is drawn. For example, FIG.
When recording an image as shown in (A), FIG.
A sample window is cut out as shown in FIG.
The template pattern as shown in (C) is compared and correction is performed. As a result, dot collapse at the intersection is reduced. For example, an image as shown in FIG. 21 (A) is recorded as shown in FIG. 21 (B) if no correction is made. However, by performing the above correction, FIG. 21 (C) is obtained.
As shown in, a line segment with reduced jaggies can be obtained.

[0011]

However, although the resolution of the printer can be artificially improved by the conventional image quality improving method, on the other hand, additional image information for instructing the size of the recording dot or the position of the recording dot is generated. To increase. For example, 600
The image data corresponding to the binary data of A4 size in dpi is about 4 MB, but if the size and position of the recording dot are provided in four steps for each pixel, the number will increase 16 times. in addition,
In the case of a color printer, it is necessary for each YMC, so 48
It doubles and the memory capacity becomes large.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image processing method and an image processing apparatus capable of effectively performing correction.

[0013]

According to a first aspect of the present invention, the recording dots are corrected in a first correction direction and a second correction direction orthogonal to the first correction direction according to a pattern of the recording dots. In the image processing method for forming an image, the recording dots are independently corrected in the first correction direction and the second correction direction.

According to the first aspect, since it is possible to independently correct the recording dot in the first correction direction and the second correction direction orthogonal to the first correction direction, the image quality is improved according to the resolution. By performing the correction only in the effective direction, unnecessary correction processing can be omitted and the processing time can be shortened.

According to a second aspect, when the resolution of the recording dots is a first resolution, the recording dots are corrected in the first and second correction directions, and the recording dots are larger than the first resolution. It is characterized in that the recording dots are corrected only in the first correction direction at the second resolution.

According to the second aspect, a large image quality improvement can be expected by performing the correction in the first and second correction directions at the first resolution having a low resolution, and the second resolution at the medium resolution can be expected. At the resolution, the processing time can be shortened by performing the correction only in the first correction direction which is effective in improving the image quality.

According to a third aspect of the present invention, a correction pattern that is compared with the pattern of the recording dots and determines a correction amount in the first correction direction is compared with a pattern of the recording dots, and the correction amount in the second correction direction is compared. The correction pattern that determines the
Is corrected and the second correction direction is corrected.

According to the third aspect, since the correction pattern can be shared by the first correction direction and the second correction direction by rotating the correction pattern, the storage capacity for storing the correction pattern can be reduced. According to a fourth aspect of the present invention, the presence or absence of correction is controlled according to the brightness of the recording dots.

According to a fourth aspect of the present invention, by controlling the presence or absence of the correction depending on the lightness of the recording dots, the correction is performed when the jaggy having low lightness is conspicuous, and the correction is not performed when the jaggy having high lightness is not noticeable. As a result, only the necessary correction can be carried out, so that efficient correction can be carried out.

According to a fifth aspect of the present invention, the recording dots have a display image of a plurality of colors, a display image of a color that is not displayed is detected from the display images of the plurality of colors, and a correction value of the recording dot of the color that is displayed is set. It is characterized in that it is stored in a recording dot storage area of a display image of a color that is not displayed.

According to the fifth aspect, when there is a color that is not displayed, the memory capacity can be reduced by using the storage area of the color as an area for storing the correction value of the displayed color. According to a sixth aspect of the present invention, there is provided a bitmap memory that stores bitmap data, a recording direction instruction memory that stores recording direction data that indicates a recording direction of the bitmap memory, and a bitmap memory that is stored in the bitmap memory. A comparison data buffer that stores the extracted sample window, a template pattern memory that stores a template pattern to be corrected, and a correction data memory that stores correction data according to the template pattern stored in the template pattern memory. A correction data memory for storing data obtained by correcting the sampling window stored in the comparison data buffer with the correction data stored in the correction data memory; and a sampling window extracted from the bitmap data, Stored in the data buffer, set template data stored in the template pattern memory according to the recording direction data stored in the recording direction instruction memory, and set the sampling window and the template pattern data stored in the comparison data buffer. Compare with the stored template data,
When they match, the correction data corresponding to the direction according to the recording direction data stored in the recording direction instruction memory is extracted from the correction data memory, and the correction data is added to the sampling window stored in the comparison data buffer. And a control unit for storing in the correction memory.

According to the sixth aspect of the present invention, the sampling window is extracted from the bit map data, stored in the comparison data buffer, and stored in the template pattern memory according to the recording direction data stored in the recording direction instruction memory. Is set, and the sampling window stored in the comparison data buffer is compared with the template data stored in the template pattern data, and when they match, the direction according to the recording direction data stored in the recording direction instruction memory is determined. The correction data is extracted from the correction data memory, the correction data is added to the sampling window stored in the comparison data buffer, and the correction data is stored in the correction memory, so that the correction can be performed in the direction according to the recording direction data. Can only be corrected in the direction Efficient correction operation can be performed.

According to a seventh aspect of the present invention, the controller rotates the template pattern stored in the template pattern memory according to the recording direction data stored in the recording direction instruction memory and stores the template pattern in the comparison data buffer. It is characterized by comparing with a sample window.

According to the seventh aspect, the template pattern stored in the template pattern memory can be shared by a plurality of recording directions. According to another aspect of the present invention, the control unit compares the sampling window stored in the comparison data buffer with the template pattern stored in the template pattern memory according to the brightness of the sampling window stored in the comparison data buffer. It is characterized by

According to the eighth aspect, since the correction can be performed according to the brightness, the correction operation can be executed only for the data of the conspicuous brightness, and the efficient correction can be executed.

[0026]

FIG. 1 is a block diagram of the first embodiment of the present invention. This embodiment shows a laser printer to which the image processing method of the present invention is applied. The laser printer 1 of the present embodiment is a printer for performing medium-level recording with a resolution of 600 dpi, and is a host computer (not shown).
An image data processing unit 2 that receives recording direction data and image data from the image data and develops the bitmap data into a bitmap data, a smoothing processing unit 3 that performs a smoothing process on the bitmap data developed in the image data processing unit 2, and a smoothing processing unit 3 The image forming unit 4 that performs printing in accordance with the data smoothed by, the print instruction from the host computer, the image data processing unit 2, the smoothing processing unit 3, and the control unit 5 that controls the image forming unit 4 are configured. It

The image data processing unit 2 comprises a bit map memory 6 and a recording direction instruction memory 7. The image data processing unit 2 develops the image data to be printed in the bitmap memory 6 according to the control signal from the control unit 5, and records to instruct the printing direction of the image data developed in the bitmap memory 6. The direction data is stored in the recording direction instruction memory 7.

Here, the printing direction data is referred to as Portlait when the erecting direction of the image data to be printed (characters and the like) and the sub-scanning direction of the printer (recording paper conveyance direction) match. The case where the upright direction of a character or the like and the sub-scanning direction of the printer differ by 90 ° is called Landscape.

The smoothing processing section 3 comprises a comparison data buffer 8, a template pattern memory 9, a smoothing correction data memory 10 and a smoothing memory 11. The smoothing processing unit 3 detects a portion where jaggies occur in the digital image data developed by the image data processing unit 2 in response to a control signal from the control unit 5, and corrects the data.

The template pattern memory 9 holds in advance an image pattern that causes jaggies in recorded samples, and holds rules defining correction data such as recording dot size and recording dot position for mitigating corresponding jaggies. are doing. Further, the comparison data buffer 8 scans the digital image data stored in the bit map memory 6, cuts out a part of the image data, and compares it with the image pattern in the template pattern memory 9. The comparison result in the comparison buffer 8 is used to determine the section of the image that causes jaggies, and the correction method is instructed.

The smoothing correction data memory 10 temporarily stores correction data for mitigating jaggies. The smoothing memory 11 also stores smoothing correction data and pit map image data for one page. The image forming unit 4 prints an image from the digital image data corrected by the smoothing processing unit 3 according to the control signal from the control unit 5.

Next, the operation of the first embodiment of the present invention will be described. FIG. 2 is an operation flowchart of the control unit according to the first embodiment of the present invention. When there is a print instruction from the host computer, the control unit 5 stores the bitmap image data and the recording direction data created by the host computer in the bitmap memory 6 and the recording direction instruction memory 7 (step S1-1).

Next, the control unit 5 determines the recording direction, that is, Portlait or Landscape according to the recording direction data stored in the recording direction instruction memory 7 (step S1-2). In step S1-2, Portlait or La
When ndscape is determined, the control unit 5 next sets the size of the prescribed image data to be read from the bitmap memory 6 in the comparison data buffer 8 according to the determined direction, Portlait or Landscape (step S1-
3, S1-4). At this time, the control unit 5 simultaneously determines the port according to the determined direction, Portlait or Landscape.
A template for lait or landscape is set in the template pattern memory 9 (steps S1-5, S1).
1-6).

Next, the control section 5 performs steps S1-3 and S3.
Bit map data of the size set in 1-4 is read from the pit map memory 6 and supplied to the comparison data buffer 8 (step S1-7). Next, the control unit 5 determines whether or not the bitmap data stored in the bitmap memory 6 has been cut out (step S1-8).

At step S1-8, if there is data to be cut out, then, at step S1-7, the bitmap data of the specified data size stored in the comparison data buffer 8 and the jaggies stored in the template pattern memory 9 are stored. It is compared with the template pattern for detection (S1-
9).

At step S1-9, if there is template data that matches the cut out data, then again,
According to the recording direction data stored in the recording direction instruction memory 7, the recording direction, that is, Portlait or Landscape
Is determined (step S1-10). Step S1-1
When Portlait or Landscape is determined to be 0, the control unit 5 reads smoothing correction data corresponding to the matched template data and according to the determined direction, Portlait or Landscape from the smoothing correction memory 10 and compares the data. Smoothing correction data is added to the image group stored in the buffer 8 and stored in the smoothing memory 11 (steps S1-11, S1-12,
S1-13, S1-14).

In the case of Portlait, the smoothing correction data is information for changing the size of recording dots in order to correct jaggies in the main scanning direction. Also, in the case of Landscape, this is information for changing the position of the recording dot in order to correct jaggies in the recording paper conveyance direction.

In step S1-9, if there is no pattern that matches the bitmap data read to the comparison data buffer 8 among the template patterns for jaggies detection stored in the template pattern memory 9, the comparison data buffer. The bitmap data stored in 8 is stored in the smoothing memory 11 as it is without correction.

The above steps S1-7 to S1-14 are repeated until it is determined in step S1-8 that there is no image group to be cut out from the bitmap memory 6. as a result,
The smoothing memory 11 stores a bitmap image to be recorded and smoothing correction data.

In step S1-8, the bit map memory 6
When it is determined that there is no image group to be cut out from the control unit 5, the control unit 5 supplies the bitmap image and the smoothing correction data stored in the smoothing memory 11 to the image forming unit 4 and sends a print command to the image forming unit 4. Supply (steps S1-15, S1-16).

Next, an explanation will be given by using an actual example. FIG. 3 and FIG. 4 show operation explanatory diagrams using an actual example of the first embodiment of the present invention. In this example, a case will be described in which a bitmap image of 9 × 7 pixels is cut out as shown in FIG. 3A and the correction is performed by comparing with a template pattern as shown in FIG. 3B.

First, from the pixel group of 9 × 7 pixels, as shown in FIG.
As shown in (3), a window consisting of 3 × 3 9 pixels centered on the pixel of interest is extracted. In the extracted window, pixels are distinguished according to the array, and the pixel value is weighted according to the array and added. The value thus obtained is called a hash value.

The hash value H is H = A × 2 ⁰ + B × 2 ¹ + C × 2 ² + D × 2 ³ + E ×, where A to I are the pixels of the window of 3 × 3 pixels according to the array. 2 ⁴ + F × 2 ⁵ + G × 2 ⁶ + H × 2 ⁷ + I × 2 ⁸ (1) The hash value H allows the pattern of white (`0 ') and black (` 1') of the window of 3 × 3 pixels to be identified.

There are 512 hash values H from 0 to 511. A preliminary examination of the templates that may hold true for all 512 patterns reveals that most cases do not apply to any template. Therefore, by first detecting the possibility of matching with the template in this 3 × 3 window, it is not necessary to check all the pixels forming the 9 × 7 pixel group, and the matching with the template can be performed efficiently. You can judge.

If only the central 9 pixels cannot be determined to match the template pattern, the position to be matched next is checked in advance and described in the 512 tables previously set. , Optimized. Next, matching is performed on the template pattern that may cut out the 8-pixel region shown in FIG. In addition, since the template pattern is extracted from the contour, a region of 8 pixels is cut out from the diagonal line or vertical and horizontal as shown in FIG.

For example, consider a pattern as shown in FIG. In FIG. 4A, the pixel of interest is a and 9
When a pixel group of × 7 pixels is cut out, it becomes as shown in FIG. When the pattern shown in FIG. 4B is matched with the template, a template pattern P1 shown in FIG. 4C is obtained. Smoothing correction data "11111100" is stored corresponding to this template pattern P1, and the pixel of interest a is corrected from "11111111" to "11111100" as shown in FIG. 4D.

The pixel of interest a is from “11111111” to “11111100
When corrected to “”, the pixel of interest a at the time of printing is shown in FIG.
As shown in, the dot size is reduced from 8/8 to 6/8. In addition, in FIG. 4A, the pixel b next to the target pixel a
As a target pixel, a pixel group of 9 × 7 pixels as shown in FIG. 4 (E) is cut out.

When the pattern shown in FIG. 4 (E) is matched with the template, a template pattern P2 shown in FIG. 4 (F) is obtained. Smoothing correction data "00000000" is stored corresponding to this template pattern P2, and the pixel of interest b is corrected from "00000000" to "11000000" as shown in FIG.

The target pixel b is from "00000000" to "11000000"
When corrected to “”, the pixel of interest b is printed at the time of printing as shown in FIG.
As shown in, the dot size is 0/8 to 2/8, that is, 2/8 dots are added. As described above, the jaggies are smoothed by reducing the recording dot size corresponding to the pixel of interest from 8 to 6 or adding small recording dots.

Next, the operation of the image forming section will be described. FIG. 5 is a block diagram of the image forming unit according to the first embodiment of the present invention. The image forming unit 4 generates a laser beam according to a laser drive signal supplied from the laser drive driver 12 and the laser drive driver 12 that controls the laser beam that generates a print dot, and a laser printer that prints an image on a print sheet. The mechanical unit 13, a drive circuit unit 14 that supplies various drive signals to the laser printing mechanism unit 13, a sequence control circuit 15 that performs sequence control of the drive circuit unit 14, and a printer control circuit 16 that integrally controls the entire image forming unit 4. It

The laser drive driver 12 generates a laser drive signal according to the corrected bitmap data supplied from the smoothing memory 11 and supplies it to the laser printer mechanism unit 13. The laser printer mechanism unit 13 includes a laser light source 17 that emits a laser beam L according to a laser drive signal generated by the laser drive driver 12, and a laser light source 17
The polygon mirror 18 that scans the laser light L generated in 1. in the main scanning direction, and the photosensitive drum 19 that is irradiated with the laser light L scanned by the polygon mirror 18 to form an electrostatic latent image on the surface thereof. A charger 20 that uniformly charges 19 and a developer 2 that reproduces a visible toner image by attaching toner to the surface of the photosensitive drum 19 on which the electrostatic latent image is formed.
1. Transfer device 22 and transfer device 2 for transferring the visible toner image reproduced by developing device 21 on photoconductor drum 19 to recording paper
2, a fixing device 23 for fixing the toner on the recording paper onto which the toner image is transferred, a cleaner 24 for removing the toner remaining on the photosensitive drum 19 after the toner image is transferred onto the recording paper, and the rotation timing of the photosensitive drum 19. A photoconductor drum rotation detection unit 25 for detecting a recording sheet, a sheet feeding cassette 26 for supplying a recording sheet, a sheet ejection tray 27 for ejecting the recording sheet on which an image is recorded, and a recording sheet conveying mechanism 28 for conveying the recording sheet.
It is composed of

A laser drive signal corresponding to the corrected bitmap data from the smoothing memory 11 is supplied from the laser drive driver 12 to the laser light source 17, and the laser light is emitted and erased in accordance with the laser drive signal. The laser light L emitted and erased in accordance with the laser drive signal is scanned and irradiated by the polygon mirror 18 onto the photosensitive drum 19 which is uniformly charged by the charger 20. As a result, an electrostatic latent image is drawn on the photosensitive drum 19 by the laser light.

Toner is supplied to the photosensitive drum 19 on which the electrostatic latent image is drawn by the developing device 21, and the toner adheres in accordance with the electrostatic latent image to form a visible toner image. The printing paper is supplied from the paper feed cassette 26 to the photosensitive drum 19 on which the visible toner image is formed, and the visible toner image is transferred to the printing paper by the transfer device 22 to form the image. The printing paper is supplied to the fixing device 23 and the toner is fixed. The printing paper to which the toner is fixed is discharged and held in the discharge tray 27.

The drive circuit section 14 includes a developing device drive circuit 29 for generating a drive signal for driving the developing device 21, a charger drive circuit 30 for generating a drive signal for driving the charger 20, and a drive for driving the polygon mirror 18. A polygon driving circuit 31 for generating a signal, a fixing device driving circuit 32 for generating a driving signal for driving the fixing device 23, a transfer device driving circuit 33 for generating a driving signal for driving the transfer device 22, and a driving signal for driving a cleaner. A cleaner drive circuit 34 for generating, a photoconductor drum drive circuit 35 for rotating the photoconductor drum 19, a recording paper conveyance drive circuit 36 for generating a drive signal for driving the recording paper conveyance mechanism 28, and a photoconductor drum detection unit 25 are detected. The photoconductor drum detection circuit 37 detects the rotational position of the photoconductor drum 19 from the signal.

The photoconductor drum drive circuit 35 responds to the control signal from the sequence control circuit 15 by the photoconductor drum 19.
Generate a drive signal to rotate the. The photoconductor drum detection circuit 37 detects the rotation angle of the photoconductor drum 19 and supplies it to the sequence control circuit 15. The developing device drive circuit 29 responds to the control signal from the sequence control circuit 15 to develop the developing device 2.
Drive 1

The charger drive circuit 30 controls the charger 20 according to the control signal from the sequence control circuit 15 to apply a predetermined initial potential to the photosensitive drum 19. The polygon drive circuit 31 drives the polygon mirror 18 that scans the laser light L in the main scanning direction in response to a control signal from the sequence control circuit 15.

The fixing device drive circuit 32 drives the fixing device 23 in accordance with the control signal from the sequence control circuit 15 so as to keep the temperature of the fixing device 23 constant. The transfer device drive circuit 33 generates a drive signal for driving the transfer device 22 according to the control signal from the sequence control circuit 15, and the transfer device 2
Feed to 2.

The cleaner drive circuit 34 drives the cleaner 24 in accordance with a control signal from the sequence control circuit 15 so as to be stably rotated at a predetermined rotation speed. In response to a control signal from the sequence control circuit 15, the recording paper conveyance drive circuit 36 transfers the printing paper from the paper feed tray 26 via the photoconductor drum 19, the transfer device 22 and the fixing device 23 to the paper ejection tray 2.
The recording paper conveying mechanism 28 is driven so as to convey the recording paper to the recording medium 7.

The sequence control circuit 15 is connected to the printer control circuit 16 and controls the drive timing of the various drive circuits according to a print command supplied from the printer control circuit 16 to control the execution of printing. The printer control circuit 16 controls driving of the entire image forming unit 4. The printer control circuit 16 is connected to the control unit 5 and
From the host computer, the print command is supplied to the end of the image data, and the print command is supplied to the sequence control circuit 16.

Next, the operation will be described. Image data processing unit 2
When the image data is stored in the pit map memory 6 and the smoothing processing in the smoothing processing unit 3 is completed,
The control unit 5 issues a print command to the printer control circuit 16. When a print command is supplied from the control unit 5, the printer control circuit 16 instructs the sequence control circuit 15 to prepare for recording so that the electrophotographic process centered on the photosensitive drum 19 can be recorded. Sequence control circuit 1
5 issues a command to the drive circuit unit 14 to activate the laser printing mechanism 13 from the drive circuit 14.

When the laser printing mechanism 13 is activated and the electrophotographic process becomes recordable, the printer control circuit 16 controls the control unit 5 to make the smoothing memory 11
Data of the recording dot size in the laser driver 1
Then, the sequence control circuit 15 is instructed to start recording.

The laser light source 17 converts image data into laser light L. The laser light L is guided to the photosensitive drum 19 by the polygon mirror 18, and the image data is converted into an electrostatic latent image by a well-known electrophotographic process. The sequence control circuit 15 uses the recording start timing from the printer control circuit 16 as a starting point, and adds a clock coefficient to monitor the rotation angle from the photoconductor drum detection circuit 37.
Monitor development of latent image by 1. Sequence control circuit 1
When the photosensitive drum 19 reaches the specified rotation angle, the recording paper feeding drive circuit 36 moves the recording paper to the photosensitive drum 1
Then, the transfer device driving circuit 33 applies a transfer voltage to the transfer device 22 to transfer the toner image onto the recording paper.

Next, the toner image is fixed on the recording paper by the fixing device 23 and is conveyed to the paper discharge tray 27. An image is formed on the recording paper by the above steps. Next, a method of changing the size of a recording dot by using laser light will be described.
FIG. 6 shows a diagram for explaining the dot changing operation of the first embodiment of the present invention.

FIG. 6 is an example showing a change in dot diameter with light emission time for controlling the size of a recording dot by a laser driving driver. This figure shows the measured data in a graph, where the vertical axis is the dot size and the horizontal axis is the emission time m.
S is taken. As shown in the figure, it can be seen that the dot size changes drastically when the light emission time is changed to be shorter than about 0.6 mS.

FIG. 7 is a block diagram of the laser drive driver of the first embodiment of the present invention, and FIGS. 8 and 9 are timing charts of the laser drive driver of the first embodiment of the present invention. The dot data stored in the smoothing memory 11 is supplied to the laser drive driver 12 and stored in the dot diameter data memory 12a.

The dot size data memory 12a stores dot size data r _0,0 , r _0,1 , r _0,2 , r in the main scanning direction.
_{0, 3,} ... _Are stored for each scanning line. The dot size data r _0,0 , r _0,1 , r _0,2 , r _0,3, ... _Are output from the print clock generator 12b and the print clocks C ₁ and C ₂ shown in FIG. , C ₃ ..., In synchronization with the main scanning order, the dot size light emission time exchanger 12 is read.
Latched to c. Dot size emission time exchanger 12c
Is a P-ROM (Programmable ROM) or normal ROM
It is composed of

[0067] dot size light-emitting time exchanger j number of the light-emitting time is latched to 12c data t _{0, 0,} t _0,1,
t _0,2, t _0,3 ···· is supplied to each flip-flop 12d-1~12d-j, which is j-number cascaded constituting the light emission time control circuit 12d. At this time, j
Light emission time data t _0,0 , t _0,1 , t _0,2 , t _0,3
Are output by a parallel load signal synchronized with the print clock output from the print clock generator.

The j pieces of light emission time data t _0,0 , t _0,1 , t _0,2 , t _0,3 ...
1 bit is shifted in synchronization with the print clock supplied from the print sub-block generator 12e shown in (E),
Sequentially sent to the latch. The latch 12f is sequentially latched from the shift register of the light emission time control circuit in synchronization with the print clock and output to the laser driver. Further, the latch 12f has parallel load signals P ₀ , P
It is set to “0” by inputting ₁ , P ₂ ... In the timing chart shown in FIG. 8, j = 7,
That is, the light emission time data t _0,0 , t _0,1 , t _0,2 , t
_{.., 3} ... _Are composed of 7 bits.

The driver 12g receives "1" from the latch 12f.
The light is emitted when .degree. Is input, and the light emission of the laser is stopped when "0" is input. FIG. 9 shows a configuration diagram of light emission time data supplied from the latch 12f to the driver 12g. FIG. 9 shows that the dot size corresponds to a 3-bit configuration. In this case, since the dot size can be designated to 8 types from level 0 to level 7, the light emission time also corresponds to that from level 0 to level 7. There are 8 levels.

In this embodiment, the dot size is changed by controlling the light emission time. However, the same effect can be obtained by controlling the laser light emission drive voltage or the light emission drive current while keeping the light emission time constant. can get. According to the present embodiment, when the erecting direction of the image data to be recorded (characters or the like) and the sub-scanning direction of the printer (recording paper conveyance direction) match, Portlait or the normality of the image data to be printed (characters or the like). Land when the vertical direction and the sub-scanning direction of the printer differ by 90 °
In case of Portlait, smoothing is performed in the horizontal direction of the recorded image, and in case of Landscape,
By smoothing the recorded image in the vertical direction, when a person views the recorded image upright, the smoothing is performed in the horizontal direction in both the Portlait and Landscape recorded images. Generally, human visual characteristics have a characteristic that the resolution in the horizontal direction is higher than that in the vertical direction.

FIG. 10 shows a diagram for explaining human visual characteristics. FIG. 10A is a schematic diagram in which one recording dot is continuously formed into a straight line, and the straight line is rotated and recorded by a printer. There is no jaggies in the horizontal and vertical directions recorded by the printer, but they are noticeable by straight lines slightly inclined from the horizontal and vertical directions. Since an ordinary printer records with the same resolution in the scanning direction, the jaggies on straight lines adjoining horizontally and vertically are the same. FIG. 10B shows data from the experimental results obtained from the human visual characteristics, and it can be seen that the human eyes have different resolutions regarding jaggies in the horizontal direction and vertical directions. The human eye has a higher resolution for jaggies in the horizontal direction than in the vertical direction. In other words, it is more effective to emphasize jaggies in the printer in the horizontal direction of human eyes.

Therefore, as in this embodiment, Portlait and
It is possible to effectively correct jaggies by performing horizontal smoothing on any recorded image of Landscape. At this time, since the correction is performed only in one direction, the processing time can be shortened.

Further, according to the present embodiment, by switching the correction direction according to the erecting direction of the character or the like, the image is corrected in the horizontal direction when viewed by a human, and the image quality is effectively improved. It FIG. 11 shows an operation explanatory diagram of the first embodiment of the present invention.

FIG. 11A shows Portlait.
State, Figure 11 (B) is Landscape
Indicates the state of. In the state of the portrait shown in FIG. 11A, the correction is performed in the direction of arrow a which is horizontal when viewed by a human, and the landscape shown in FIG.
Even in the (landscape) state, the correction is performed in the direction of the arrow a, which is horizontal when viewed by a human.

FIG. 12 shows a block diagram of the second embodiment of the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, in the first embodiment, when it is clearly indicated by the resolution data that the low resolution image data is sent to the bitmap memory, the correction data is selectively operated according to the sent resolution. By doing so, the operation of the smoothing processing unit is switched.

In this embodiment, the case where a bit image is sent from a host computer at low, medium and high resolutions will be described. Here, the low-resolution bitmap image is, for example, an image of about 300 dpi, and requires bit correction in both the horizontal and vertical directions in terms of image quality.

The medium resolution bitmap image is, for example, an image of about 600 dpi, which requires horizontal correction with respect to the upright direction of the recorded image, and the high resolution bitmap image is, for example, about 1200 dpi. Is a high-quality image that does not require correction.

The laser printer 100 of the present embodiment receives recording direction data and image data from a host computer (not shown) and develops them in the image data processing unit 101 and the image data processing unit 101, which develops the data into bitmap data. Smoothing processing unit 102 for performing smoothing processing on the bitmap data, smoothing processing unit 102
The image forming unit 4 that prints according to the data smoothed by the print instruction is received from the host computer, and the image data processing unit 101 and the smoothing processing unit 10 are received.
2. The control unit 103 controls the image forming unit 4.

The image data processing unit 101 stores, for example, a bitmap memory 6 for developing an image created by a personal computer into digital image data and storing the digital image data, and recording direction data corresponding to the printing direction recorded by the image forming unit. In addition to the recording direction instruction memory 7, it has an optimization selection circuit 105 for setting resolution data for identifying the resolution of the transmitted bitmap image.

The smoothing processing section 102 comprises a comparison data buffer 8, a template pattern memory 9, a smoothing memory 11, a recording size memory 106 and a recording position memory 107. Recorded size memory 1
06, the recording position memory 107 is provided in place of the smoothing correction data memory 10 of the first embodiment. The recording size memory 106 temporarily stores the size of the recording dot to be corrected in order to reduce jaggies. Also,
The recording position memory 107 stores the position on the bitmap of the data stored in the storage size memory 106.

Smoothing processing can be performed independently in the horizontal and vertical directions of the recorded image.
Depending on the resolution data set in the optimization selection circuit 105, it is possible to select whether to perform smoothing in both horizontal and vertical directions, only in the horizontal direction with respect to the erect direction of the recorded image, or not to perform smoothing. It is configured.

FIG. 13 shows an operation flowchart of the control unit according to the second embodiment of the present invention. The bitmap image created by the host computer is stored in the bitmap memory 6, the recording direction instruction memory 7, and the optimization selection circuit 105 together with the recording direction data and the resolution data. Depending on the recording direction specified in the recording direction instruction memory 7, Portla
Whether it or Landscape is determined, and the size of the specified image data to be read from the bitmap memory is set in the comparison data buffer 8. At the same time, Portlait or La
A template for ndscape is set in the template pattern memory 9 (steps S2-1 to S2-6).

Next, the control unit 103 reads the area where jaggies should be detected from the pit map memory 6 into the comparison data buffer 8 and compares it with the template pattern for jaggies detection stored in the template pattern memory 9 (step S2). -7 to S2-9). At this time, the number of template patterns for jaggy detection is determined by the type of jaggy shape to be corrected.

In step S2-9, the control section 103 successively compares the template pattern for jaggies detection defined in the template pattern memory 9 and the pit map data read out in the comparison data buffer 8 and, if they match, the optimum. The item to be extracted as the correction data from the template pattern memory 9 is determined according to the resolution set in the conversion selection circuit 105 (steps S2-10 to S2-).
17).

If it is determined in step S2-10 that the image is a high-resolution bitmap image, the jaggies cannot be detected by the human eyes, so the correction data for smoothing is not added and the data is directly stored in the smoothing memory. 1
1 (step S2-18).

If it is determined in step S2-11 that the image is a medium-resolution bitmap image, the recording direction is referred to again to determine the recording direction (step S2-12). In step S2-12, the recording direction
If it is determined to be Portlait, the size data is read from the recording size memory 106 according to the template pattern with which the smoothing data for the horizontal smoothing is matched, and the recording position memory is read according to the template pattern of the smoothing memory 11. The smoothing data is set in the smoothing memory 11 by storing it in the position designated by 107.

In step S2-12, the recording direction is Landsc
If judged as ape, vertical smoothing data is not added. Further, steps S2-10 and S2
When it is determined in -11 that the image is a low-resolution pit map image, data for correcting the smoothing in the horizontal and vertical directions is added regardless of the recording direction.

When the template pattern for jaggies detection stored in the template pattern memory and the bitmap data read in the comparison data buffer do not match, the bitmap data stored in the comparison data buffer is stored in the smoothing memory as it is ( Step S2-18).

As described above, according to the present embodiment, at the time of high resolution (1200 dpi) which does not require correction, correction is not performed in both the horizontal and vertical directions, but the low resolution (300 dpi) which needs correction.
In the case of i), the processing speed is improved, both horizontal and vertical are corrected to obtain a smooth image, and in the case of medium resolution, only the horizontal correction that is noticeable to human eyes is performed to improve and process the image quality. We are trying to reduce the speed.

As described above, the processing according to the resolution can be realized and the efficient image processing can be realized. FIG. 14 shows a block diagram of the third embodiment of the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the image processing method of the present invention is applied to a color electrophotographic printer.

The laser printer 200 of this embodiment comprises an image data processing unit 201, a smoothing processing unit 202, an image forming unit 203, and a control unit 204. The image data processing unit 201 includes a color bitmap memory 205 for storing a color bitmap image and a recording direction instruction memory 7. Color image data to be recorded is expanded into digital image data for each color and stored in the color bitmap memory 205. Smoothing processing unit 202
Is a comparison data buffer 8, a template pattern memory 9, a smoothing correction memory 10, and a yellow smoothing memory 2 provided for each basic color of a color image.
06, a magenta smoothing memory 207, and a cyan smoothing memory 208.

The smoothing processing unit 202 includes a control unit 20.
3, the same operation as that of the first embodiment is performed for each color of yellow, magenta, and cyan, a portion where jaggies are likely to occur is detected from the digital image, correction data is generated, and yellow, magenta, Smoothing memories 206, 207, and 208 provided for each cyan color
Then, it is supplied to the image forming unit 203.

In the image data processing unit 201, for example, yellow, magenta,
A cyan color image is stored in the bitmap memory 205.
And stored as digital image data. Further, the recording direction data is stored in the recording direction instruction memory 7 as to match or not match the upright direction of the image data to be recorded and the sub-scanning direction (recording paper conveyance direction) of the printer.

Smoothing memories 206, 207, 20
Reference numeral 8 stores the recording size to be corrected to alleviate jaggies for one page for each color of yellow, magenta, and cyan. Next, the operation of the third embodiment will be described. FIG. 15 shows an operation flowchart of the control unit according to the third embodiment of the present invention.

When there is a print instruction from the host computer, the control unit 204 stores the color bitmap image data and the recording direction data created by the host computer in the bitmap memory 205 and the recording direction instruction memory 7 (step S3-). 1). Next, the control unit 204 determines the recording direction, that is, Portlait or Landscape according to the recording direction data stored in the recording direction instruction memory 7 (step S3-2). In step S3-2,
When Portlait or Landscape is determined, the control unit 2
04 is the next direction, Portlait or Land
The size of the specified image data to be read from the bitmap memory 205 according to the scape is compared with the comparison data buffer 8
(Steps S3-3 and S3-4). At this time, the control unit 204 simultaneously determines the determined direction and Portla.
Portlait or Landscape depending on it or Landscape
Template pattern memory 9 for template for ape
(Steps S3-5 and S3-6).

Next, the control unit 204, step S3-.
3, bitmap data of the size set in S3-4 is read from the pit map memory 205 and supplied to the comparison data buffer 8 (step S3-7). Next, the control unit 204 determines whether or not an image whose brightness is lower than a predetermined value is cut out from the color bitmap data stored in the bitmap memory 205 (step S3-8).

This is because the jaggies are not conspicuous for the ones having a large lightness such as yellow, and the correction is not effective. Therefore, the correction can be effectively performed for the pixels of the dark and low lightness pixels. By performing the above, the processing is efficiently performed.

At step S3-8, if there is data of low lightness to be cut out, then it is stored in the template pattern memory 9 and the bitmap data of the specified data size stored in the comparison data buffer 8 at step S3-7. It is compared with the template pattern for the detected jaggies (step S3-9).

In step S3-9, if there is template data that matches the cut out data, then again,
According to the recording direction data stored in the recording direction instruction memory 7, the recording direction, that is, Portlait or Landscape
Is determined (step S3-10). Step S3-1
When 0 is determined as Portlait or Landscape, the control unit 204 corresponds to the matched template data,
Moreover, the smoothing correction data corresponding to the determined direction, Portlait or Landscape is read from the smoothing correction memory 10, the smoothing correction data is added to the image group stored in the comparison buffer 8 and stored in the smoothing memories 206, 207 and 208. Yes (step S3
-11, S3-12, S3-13, S3-14).

In the case of Portlait, the smoothing correction data is information for changing the size of recording dots in order to correct jaggies in the main scanning direction. Also, in the case of Landscape, this is information for changing the position of the recording dot in order to correct jaggies in the recording paper conveyance direction.

In step S3-9, if there is no pattern that matches the bitmap data read to the comparison data buffer 8 among the template patterns for jaggies detection stored in the template pattern memory 9, the comparison data buffer The bitmap data stored in 8 is directly corrected by the smoothing memory 206,
It is stored in 207 and 208.

The above steps S3-7 to S3-14 are repeated until it is determined in step S3-8 that there is no image group to be cut out from the bitmap memory 205. As a result, the smoothing memory 11 stores the bitmap image to be recorded and the smoothing correction data.

In step S3-8, the bitmap memory 2
If it is determined that there is no image group to be cut out from 05, the control unit 204 supplies the bitmap image and the smoothing correction data stored in the smoothing memory 11 to the image forming unit 4 and a print command to the image forming unit 4. Is supplied (steps S3-15, S3-16).

The above data cutting from the pit map memory and template comparison are repeated for all the yellow, magenta, and cyan bit map images stored in the pit map memory. as a result,
The smoothing memory stores the yellow, magenta, and cyan pit map images to be recorded and the smoothing correction data. The operation of the smoothing processing unit is to correct the pixel value by performing the procedure described in the first embodiment on each of the yellow, magenta, and cyan images.

In the present embodiment, the above smoothing processing is performed for a color whose brightness is lower than a predetermined value, but it is conceivable that the above processing is performed only for the pixels whose brightness is minimum, that is, black pixels. Such a configuration can be realized by minimizing the lightness determination level of the third embodiment.
With such a configuration, the processing time can be shortened because the processing can be minimized.

FIG. 16 shows a block diagram of a color laser printer using the image processing method of the third embodiment of the present invention. In the figure, the same components as those in FIG.
The description is omitted. The image forming unit 203 of this embodiment is
A laser drive driver 12 that controls a laser beam that generates a print dot, a laser printer mechanism unit 209 that generates a laser beam in accordance with a laser drive signal supplied from the laser drive driver 12, and prints an image on a print sheet, a laser print It is composed of a drive circuit unit 210 that supplies various drive signals to the mechanism unit 209, a sequence control circuit 211 that performs sequence control of the drive circuit unit 210, and a printer control circuit 212 that integrally controls the entire image forming unit 203.

The laser drive driver 12 generates a laser drive signal according to the corrected bitmap data supplied from the smoothing memories 206, 207 and 208, and supplies it to the laser printer mechanism section 209. The laser printer mechanism unit 209 includes a laser light source 17 that emits a laser light L according to a laser drive signal generated by the laser drive driver 12, and a polygon mirror that scans the laser light L generated by the laser light source 17 in the main scanning direction. 18, a laser beam L scanned by the polygon mirror 18 is irradiated, and an electrostatic latent image is formed on the surface of the photosensitive drum 19, the photosensitive drum 1.
9, a charging device 20 for uniformly charging 9 and developing devices 213, 214 for reproducing yellow, magenta, and cyan toners on the surface of the photosensitive drum 19 on which the electrostatic latent image is formed to reproduce a visible toner image on each of them. 215, photosensitive drum 19
The intermediate transfer drum 216 on which the visible toner images reproduced by the developing devices 213, 214, and 215 are transferred to reproduce the color visible toner image, and the toner images of the respective colors reproduced on the photosensitive drums 19 are transferred on the intermediate transfer drum. 216, an intermediate transfer device 217 for transferring the toner to the recording paper, a transfer device 22 for transferring the color visible toner image reproduced on the intermediate transfer drum 216 to the recording paper, and a fixing device for fixing the toner on the recording paper on which the toner image is transferred by the transfer device 22. 23, a cleaner 24 for removing the toner remaining on the photoconductor drum 19 after the toner image is transferred onto the recording paper, a photoconductor drum rotation detection section 25 for detecting the rotation timing of the photoconductor drum 19, and a supply of the recording paper. A paper cassette 26, a paper ejection tray 27 for ejecting recording paper on which an image has been recorded, and a recording paper conveyance mechanism 28 for conveying recording paper. Ri made.

The driving circuit section 210 is replaced with the developing unit driving circuit 29 of the image forming section of the first embodiment, and developing units 213 and 21 are provided.
4, a developing device drive circuit 218, 219, 220 for generating drive signals for driving the intermediate drum drive circuit 221 and an intermediate drum drive circuit 221 for driving the intermediate drum 216, and a toner image transferred from the photosensitive drum 19 to the intermediate transfer drum 216. Intermediate transfer driving circuit 22 for driving the intermediate transfer device 217
2 is added.

Next, the operation will be described. Image data processing unit 2
When the color image data is stored in the pit map memory 205 of No. 01 and the smoothing processing in the smoothing processing unit 202 is completed, the control unit 204 issues a print command to the printer control circuit 212. Printer control circuit 212
When a print command is supplied from the control unit 204, the command instructs the sequence control circuit 211 to prepare for recording so that the electrophotographic process centered on the photosensitive drum 19 can be recorded. The sequence control circuit 211 issues a command to the drive circuit unit 210 to activate the laser printing mechanism 209 from the drive circuit 210.

When the laser printing mechanism 209 is activated and the electrophotographic process becomes recordable, the printer control circuit 211 controls the control unit 204 so that the data of the recording dot size in the smoothing memories 206, 207 and 208 is recorded. Is sent to the laser drive driver 12, and the sequence control circuit 211 is instructed to start recording.

The laser light source 17 converts image data into laser light L. The laser light L is guided to the photoconductor drum 19 by the polygon mirror 18, and image data for each color of yellow, magenta, and cyan is formed into an electrostatic latent image on the photoconductor drum 19 by a well-known electrophotographic process.

The sequence control circuit 211 uses the recording start timing from the printer control circuit 212 as a starting point.
A clock is added to monitor the rotation angle from the photoconductor drum detection circuit 37, and the development of the latent image by the developing devices 213, 214, and 215 is monitored. Sequence control circuit 211
When the photosensitive drum 19 reaches the specified rotation angle, the intermediate transfer driving circuit 222 applies a transfer voltage to the intermediate transfer device 217 to transfer the toner image to the intermediate drum 216.

Next, the recording paper is conveyed to the intermediate transfer drum 216 through the recording paper conveyance drive circuit 36, the transfer device drive circuit 33 is driven to apply a transfer voltage to the transfer device 22, and the intermediate transfer drum 216 records the recording paper. Transfer the color image to. Next, the toner image is fixed to the recording paper by the fixing device 23 and is conveyed to the paper discharge tray 27. Through the above steps, a color image is formed on the recording paper.

According to this embodiment, a color image can be corrected at high speed as in the first embodiment.
FIG. 17 shows a block diagram of the fourth embodiment of the present invention.
In this embodiment, the image processing method of the present invention is applied to a color electrophotographic printer having four color toners of yellow, magenta, cyan and black.

The blinter as in this embodiment does not have a recording capacity for storing the smoothing information obtained by the smoothing processing section. Therefore, in the present embodiment, the smoothing is performed only for the characters expressed in black, and the smoothing information is stored in the image memory reserved for yellow, magenta, and cyan.

The laser printer 300 of this embodiment comprises an image data processing section 301, a smoothing processing section 302, an image forming section 303, and a control section 304. The image data processing unit 201 includes a color bitmap memory 305 that stores a color bitmap image and a recording direction instruction memory 7. The color bit map memory 305 stores the color image data to be recorded and the black color after being developed into digital image data for each color. The smoothing processing unit 302 includes a comparison data buffer 8, a template pattern memory 9, a smoothing correction memory 10, and a yellow smoothing memory 206, a magenta smoothing memory 207, a cyan smoothing memory 208, and a black smoothing provided for each basic color of a color image. The memory 306 is included.

The smoothing processing unit 302 includes the control unit 30.
4, the same operation as in the first embodiment is performed for each color of yellow, magenta, cyan, and black, and a portion where jaggies are likely to occur is detected from the digital image,
The correction data is generated and the smoothing memories 206, 207, 2 provided for the respective colors of yellow, magenta, and cyan.
08 and 306, and supplies to the image forming unit 202.

In the image data processing unit 301, for example, yellow, magenta,
Bitmap memory 3 for color images consisting of cyan and black
05 stored as digital image data. Also,
The recording direction data is stored in the recording direction instructing memory 7 to indicate whether the erecting direction of the image data to be recorded and the sub-scanning direction (recording paper conveyance direction) of the printer are the same.

Smoothing memories 206, 207, 20
Reference numerals 8 and 306 store the recording size to be corrected for mitigating jaggies for one page for each color of yellow, magenta, and cyan. FIG. 18 shows an operation flowchart of the control unit according to the fourth embodiment of the present invention.

When there is a print instruction from the host computer, the control unit 304 stores the color bitmap image data and recording direction data created by the host computer in the bitmap memory 305 and recording direction instruction memory 7 (step S4-). 1). Next, the control unit 304 determines the recording direction, that is, Portlait or Landscape according to the recording direction data stored in the recording direction instruction memory 7 (step S4-2). In step S4-2,
When Portlait or Landscape is determined, the control unit 3
04 is the next direction, Portlait or Land
The size of the specified image data to be read from the bitmap memory 205 according to the scape is compared with the comparison data buffer 8
(Steps S4-3 and S4-4). At this time, the control unit 304 simultaneously determines the determined direction and Portla.
Portlait or Landscape depending on it or Landscape
Template pattern memory 9 for template for ape
(Steps S4-5 and S4-6).

Next, the control unit 304, step S4-.
3, bitmap data of the size set in S4-4 is read from the pit map memory 305 and supplied to the comparison data buffer 8 (step S4-7). Next, the control unit 304 determines whether or not the data read from the color bitmap data stored in the bitmap memory 305 is black (step S4-8). Step S4-8
If the cut out image is not black, step S4-
Return to 7 and cut out the next image.

This is because black or the like is more noticeable in jaggies than other colors, and it is necessary to perform correction. If the clipped image is black in step S4-8, smoothing is performed. In the smoothing, first, it is determined whether or not the cutout has been completed for all bitmap data (step S4-9).

If there is image data to be cut out in step S4-9, then it is stored in the template pattern memory 9 and the bitmap data of the specified data size stored in the comparison data buffer 8 in step S4-7. It is compared with the template pattern for detecting jaggies (step S4-10).

In step S4-10, if there is template data that coincides with the cut-out data, then, again, according to the recording direction data stored in the recording direction instruction memory 7, the recording direction, that is, Portlait or Landsc
Ape is determined (step S4-11). Step S4
If Portlait or Landscape is determined in -11, the control unit 304 corresponds to the matched template data and determines the determined direction, Portlait or Landscape.
The smoothing correction data corresponding to the ape is read from the smoothing correction memory 10, the smoothing correction data is added to the image group stored in the comparison buffer 8 and stored in the smoothing memories 206, 207, 208 and 306 (step S4-12, S4-13, S4-14, S4
-15).

Here, the extracted smoothing information of the black image is stored in the corresponding yellow, magenta, and cyan bitmap image memories. The memory address to be stored is the same as that of the black image from which the smoothing information is extracted. In other words, it does not make sense to superimpose other yellow, magenta, and cyan toners on the part to be finally recorded with black toner on the recording paper.Therefore, use the yellow, magenta, and cyan image memories as the memory for storing smoothing information. ing.

In the case of Portlait, the smoothing correction data is information for changing the size of recording dots in order to correct jaggies in the main scanning direction. Also, in the case of Landscape, this is information for changing the position of the recording dot in order to correct jaggies in the recording paper conveyance direction.

If it is determined in step S4-10 that the template pattern for jaggies detection stored in the template pattern memory 9 does not match the bitmap data read to the comparison data buffer 8, the comparison data buffer The bitmap data stored in 8 is directly corrected by the smoothing memory 206,
It is stored in 207, 208, and 306.

The above steps S3-7 to S3-14 are repeated until it is determined in step S3-8 that there is no image group to be cut out from the bitmap memory 205. As a result, the smoothing memory 11 stores the bitmap image to be recorded and the smoothing correction data.

If it is determined in step S4-10 that there is no image group to be cut out from the bitmap memory 205,
The control unit 304 controls the smoothing memories 206, 207,
The bitmap image and the smoothing correction data stored in 208 and 306 are supplied to the image forming unit 4 and a print command is supplied to the image forming unit 4 (step S4).
-15).

Next, it is judged whether or not the transferred image is a black image, and if it is a black image, the smoothing memory 206,
Image data is extracted from 207 and 208, and if it is not a black image, smoothing memories 206 and 207,
Printing is performed from the images stored in 208 and 306 (steps S4-15, S4-16, S4-17).

The above-described clipping of black bit data from the bitmap memory and template comparison are repeated for the black bitmap image stored in the bitmap memory. As a result, smoothing information about the black image can be stored in the yellow, magenta, and cyan bit map images.

[0132]

As described above, according to the first aspect of the present invention, the recording dots are independently corrected in the first correction direction and the second correction direction orthogonal to the first correction direction. Since it can be performed, there is a feature that unnecessary correction processing can be omitted and processing time can be shortened by performing correction only in a direction effective for improving image quality according to resolution.

According to the second aspect, a significant improvement in image quality can be expected by performing the correction in the first and second correction directions at the first resolution having a low resolution, and the second resolution at the medium resolution can be expected. The resolution has a feature that the processing time can be shortened by performing the correction only in the first correction direction which is effective in improving the image quality.

According to the third aspect, since the correction pattern can be shared in the first correction direction and the second correction direction by rotating the correction pattern, the storage capacity for storing the correction pattern can be reduced. Have. According to the fourth aspect, by controlling the presence or absence of the correction depending on the brightness of the recording dots, the correction is performed when the jaggies with low brightness are conspicuous, and the correction is not performed when the jaggies with high brightness are not conspicuous. Since it is possible to perform only simple corrections, it has a feature that efficient corrections can be performed.

According to the fifth aspect, when there is a color that is not displayed, the memory capacity can be reduced by using the storage area of the color as an area for storing the correction value of the displayed color. According to the sixth aspect, the sampling window is extracted from the bitmap data, stored in the comparison data buffer, and the template data stored in the template pattern memory is set according to the recording direction data stored in the recording direction instruction memory. , The sampling window stored in the comparison data buffer is compared with the template data stored in the template pattern data, and when they match, the correction data according to the direction according to the recording direction data stored in the recording direction instruction memory is obtained. By extracting the correction data from the correction data memory, adding the correction data to the sampling window stored in the comparison data buffer, and storing it in the correction memory, it is possible to perform correction in the direction according to the recording direction data, so that only in the prominent direction. Correction can be performed and efficient compensation is possible. Action has the features such as can be performed.

According to the seventh aspect, the template pattern stored in the template pattern memory can be shared by a plurality of recording directions, so that the memory capacity can be reduced. According to the eighth aspect, since the correction can be performed according to the brightness, the correction operation can be executed only for the data of the conspicuous brightness, the efficient correction can be executed, and the high-speed processing can be realized. Has features.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is an operation flowchart of a control unit according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram using an actual example of the first embodiment of the present invention.

FIG. 4 is an operation explanatory diagram using an actual example of the first exemplary embodiment of the present invention.

FIG. 5 is a block configuration diagram of an image forming unit according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a dot changing operation of the first embodiment of the present invention.

FIG. 7 is a block diagram of a laser drive driver according to the first embodiment of the present invention.

FIG. 8 is an operation timing chart of the laser drive driver according to the first embodiment of the present invention.

FIG. 9 is an operation timing chart of the laser drive driver according to the first embodiment of the present invention.

FIG. 10 is a diagram for explaining human visual characteristics.

FIG. 11 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 12 is a block diagram of a second embodiment of the present invention.

FIG. 13 is an operation flowchart of the control unit according to the second embodiment of the present invention.

FIG. 14 is a block diagram of a third embodiment of the present invention.

FIG. 15 is an operation flowchart of the control unit according to the third embodiment of the present invention.

FIG. 16 is a block configuration diagram of an image forming unit according to a third embodiment of the present invention.

FIG. 17 is a block configuration diagram of a fourth embodiment of the present invention.

FIG. 18 is an operation flowchart of the control unit according to the fourth embodiment of the present invention.

FIG. 19 is a block diagram of a conventional example.

FIG. 20 is a diagram illustrating an operation of a conventional example.

FIG. 21 is a diagram illustrating an operation of a conventional example.

[Explanation of symbols]

 1, 100, 200, 300 Laser printer 2, 101, 201, 301 Image processing unit 3, 102, 202, 302 Image smoothing processing unit 4, 203, 303 Image forming unit 5, 103, 204, 304 Control unit 6, 205 , 305 Bitmap memory 7 Recording direction instruction memory 8 Comparison data buffer 9 Template pattern memory 10 Smoothing correction data memory 11 Smoothing memory

Claims (8)

[Claims] 1. An image processing method for forming an image by correcting a recording dot in a first correction direction and a second correction direction orthogonal to the first correction direction according to a pattern of the recording dot, wherein An image processing method, wherein recording dots are independently corrected in the first correction direction and the second correction direction. 2. When the resolution of the recording dots is a first resolution, the recording dots are corrected in the first and second correction directions, and the recording dots have a second resolution larger than the first resolution. The image processing method according to claim 1, wherein the correction of the recording dots is performed only in the first correction direction when the resolution is reached. 3. Compared with the pattern of the recording dots,
By rotating the correction pattern, the correction pattern that determines the correction amount in the first correction direction and the correction pattern that is compared with the pattern of the recording dots and determines the correction amount in the second correction direction are shared. The image processing method according to claim 1, wherein the first correction direction and the second correction direction are corrected. 4. The image processing method according to claim 1, wherein the presence or absence of correction is controlled according to the brightness of the recording dots. 5. The recording dots have a display image of a plurality of colors, a display image of a color that is not displayed is detected from the display images of the plurality of colors, and the correction value of the recording dot of the displayed color is not displayed 5. The image processing method according to claim 1, wherein the color display image is stored in a recording dot storage area. 6. A bitmap memory for storing bitmap data, a recording direction instructing memory for storing recording direction data for instructing a recording direction of the bitmap memory, and a bitmap memory stored in the bitmap memory. A comparison data buffer that stores the extracted sample window, a template pattern memory that stores a template pattern to be corrected, and a correction data memory that stores correction data according to the template pattern stored in the template pattern memory A correction data memory for storing data obtained by correcting the sampling window stored in the comparison data buffer with the correction data stored in the correction data memory; and extracting a sampling window from the bitmap data, The template data stored in the comparison data buffer and set in the template pattern memory according to the recording direction data stored in the recording direction instruction memory is set, and the sampling window and the template pattern stored in the comparison data buffer are set. The template data stored in the data is compared, and when they match, the correction data corresponding to the direction corresponding to the recording direction data stored in the recording direction instruction memory is extracted from the correction data memory, and the comparison data buffer An image processing apparatus, comprising: a control unit that adds the correction data to a sampling window stored in the storage unit and stores the correction data in the correction memory. 7. The sample window stored in the comparison data buffer by rotating the template pattern stored in the template pattern memory according to the recording direction data stored in the recording direction instruction memory. The image processing device according to claim 6, which is compared with 8. The controller compares the sampling window stored in the comparison data buffer with a template pattern stored in the template pattern memory according to the brightness of the sampling window stored in the comparison data buffer. The image processing apparatus according to claim 6, which is performed.