JPH11165441A - Image processing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce images in a low density area and intermediate images excellently by gradation correction adjacent images through correction characteristics information, and carrying out no gradation correction as a detection is made such that an image region having a predetermined image component signal has no predetermined width. SOLUTION: A full color sensor 34 conducts a resolution into a plurality of images by a photoelectric conversion element, and a correction at a shading correction part 203 via an analogue signal processing part 201 or the like, and further converts the RGB brightness signal of an image signal inputted from an input interface 250 to a CMY density signal at an LGO conversion part 206. Each density of a manuscript and an output image is accorded by LUT 211 of the gradation correction of adjacent images, and a predetermined pulse signal is emitted by a pulse width modulator 212 to be inputted in a laser driver 41. In addition, when an observation picture element-including image region has only the image width of one picture element in the scanning direction with respect to signals from an image region width measurement part 230, a controller 200 operates of forbid a gradation correction process by the LUT 211.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and an image processing method for performing a correction process according to, for example, the density of an input image.

[0002]

2. Description of the Related Art In an image processing apparatus for reproducing an original image based on a digital image signal, generally, when image formation processing is performed at a high resolution, the reproduction of individual pixels is unstable. There is a problem that highlight roughness is conspicuous. In particular, in an electrophotographic digital copying machine, which is a typical image processing apparatus, when the slope of the γ characteristic curve in the γ correction unit becomes large, discharge unevenness or the like is caused by contamination of the charging surface of a charger for charging the photosensitive drum. It is easily affected, and the reproducibility of the halftone image is significantly reduced. Therefore, a method has been proposed in which two adjacent pixels are mutually corrected to be expressed as any one of the pixels, thereby reducing the roughness of highlights in a reproduced image. Here, a method of mutually correcting two adjacent pixels will be outlined.

FIG. 9 is a diagram for explaining a method of mutually correcting two adjacent pixels. In this method, first, in a plurality of pixels adjacent to each other in the main scanning direction and the sub-scanning direction shown in FIG.
・ I will divide it. When performing gradation correction on image data of each pixel using a look-up table (hereinafter, LUT),
For example, as in the LUT shown in FIG. 10, the correction is performed based on different characteristic curves for the row A and the row B. That is, A
When the image data of the pixels corresponding to the columns has the input level 55, the image data output from the LUT remains at the 55 level. On the other hand, when the image data of the pixel corresponding to the column B has the input level 55, the image data output from the LUT is corrected to five levels.

[0004]

However, in the above conventional example, the degree of correction differs depending on the level of the level of the image data input to the LUT.
FIG. 11 shows the state after the gradation correction by the input image data is gradually expressed from low density to high density.

FIG. 11 is a diagram for explaining an output image of an image in the area gradation system when gradation of input image data from low density to high density is corrected by the LUT of FIG. As shown in the figure, the output image is 200 dpi × 400 dpi in the low-density region in the upper part of FIG. 11, and becomes 40 pixels in the high-density region (lower part of FIG. 11).
It becomes 0 dpi × 400 dpi. That is, due to the characteristics of the LUT in FIG. 10, in the output image, dots are reproduced in both the rows A and B in the high-density region, but the dots are reproduced in the low-density portion.
Dots are reproduced only in rows. Therefore, for example, FIG.
As shown in FIG. 10A, when the line image in the low-density area of the x-th column having a width of one pixel in the sub-scanning direction is corrected by the LUT of FIG. Is corrected by the characteristic curve for column A, the output image (B1) is reproduced with the same dots as in FIG. 12A, but when the x-th column is an even-numbered column, The image to be output is corrected by the characteristic curve shown in FIG.
As shown in 2), the image becomes thin or disappears.

As described above, when adjacent pixels are corrected by the LUT as shown in FIG. 10, the input image is reproduced as described above. For example, in the case of an oblique line as shown in FIG. As shown in the output image of FIG. 3B, dots are drawn in column A, but the dots disappear in column B, resulting in an intermittent image as a whole, which cannot be said to be a good gradation correction process. Therefore, the method of mutually correcting two adjacent pixels as described above causes a reduction in resolution for input image data in a low-density region, and in particular, jaggies are noticeable in oblique lines and the like. There are evils.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus and an image processing method capable of favorably reproducing an image in a low density range and a halftone image.

[0008]

In order to achieve the above object, an object of the present invention is to provide an image processing apparatus having the following configuration.

That is, an image area of a predetermined size consisting of a plurality of pixels included in an image represented by an input image signal, wherein each of the plurality of pixels has a predetermined image component signal within a predetermined level range. A detecting unit for detecting an area, a correcting unit for performing gradation correction on a plurality of pixels adjacent to the image according to different correction characteristic information, and an image area including a pixel of interest by the detecting unit having a predetermined width. And control means for performing control to prohibit gradation correction by the correction means when it is detected that there is no gradation correction.

For example, when the image area does not have a predetermined width and a plurality of pixels constituting the image area each have a density lower than a predetermined density value, the control means may control the correction means. Is prohibited.

Further, for example, the correction means includes: an odd-numbered column pixel adjacent to the image represented by the image signal in a main scanning direction;
Tone correction may be performed on the even-numbered column pixels according to different correction characteristic information.

Alternatively, in order to achieve the above object, an image processing method of the present invention has the following configuration.

That is, an image area of a predetermined size including a plurality of pixels included in an image represented by an input image signal, wherein the plurality of pixels each have a predetermined image component signal within a predetermined level range. A detection step of detecting an area, and a correction step of performing tone correction on a plurality of pixels adjacent to the image according to different correction characteristic information,
When the detection step detects that the image area including the pixel of interest does not have the predetermined width, the tone correction in the correction step is prohibited.

For example, when the image area does not have a predetermined width and a plurality of pixels constituting the image area each have a density lower than a predetermined density value, the gradation correction in the correction step is performed. It is characterized by prohibition.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic color digital copying machine as a typical image processing apparatus will be described in detail with reference to the drawings.

[First Embodiment] <Digital Copier> First, the overall configuration and image forming operation of a digital copier will be described with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a sectional view showing a schematic configuration of a digital copying machine as a first embodiment of the present invention.

FIG. 2 is a block diagram of an image forming process in the digital copying machine according to the first embodiment of the present invention.

The digital copying machine shown in FIG. 1 includes a reader unit for reading an original image, and a printer unit for reproducing the original image on recording paper based on an image signal of the original image read by the reader unit. The operations of the reader unit and the printer unit described below are controlled by controllers 100 and 200, respectively. Note that the controller 200 is the CPU 2
14, and controls according to a program stored in the ROM 213 in advance. Also, the controller 100
Also includes a CPU (not shown), and it goes without saying that control is performed according to a program stored in the ROM in advance.

When a copy start key (not shown) is pressed in the reader unit, the controller 100 starts exposure scanning of the original 30 placed on the original platen glass 31 by the exposure lamp 32. The reflected light image from the original 30 obtained by the exposure scanning is collected on the full-color sensor 34.

The full-color sensor 34 has R (red),
Line sensors of three colors G (green) and B (blue) are arranged at a predetermined distance from each other in the sub-scanning direction, and a plurality of light receiving elements are arranged in a line in each line sensor. The full-color sensor 34 detects the incident original 3
The reflected light image from 0 is separated into a plurality of pixels by a plurality of photoelectric conversion elements, and a photoelectric conversion signal (color-separated image signal) is generated according to the density of each pixel.

In FIG. 2, the image signal output from the full-color sensor 34 is adjusted in gain and offset by an analog signal processing unit 201, and the A / D converter 20
In step 2, each color component is converted into an RGB digital signal of, for example, 8 bits (0 to 255 levels: 256 tones).

The RGB digital signal input to the shading correction unit 203 is optimized in gain corresponding to each light receiving element in order to eliminate the variation in sensitivity of the light receiving elements arranged in a line in the full color sensor 34. General shading correction is performed.

The line delay unit 204 corrects a spatial shift included in the image signal output from the shading correction unit 203. This spatial shift is caused by the line sensors of the full-color sensor 34 being arranged at a predetermined distance from each other in the sub-scanning direction. Specifically, based on the B (blue) color component signal, the R (red) and G (green) color component signals are line-delayed in the sub-scanning direction to synchronize the phases of the three types of color component signals. .

The input masking unit 205 converts the color space of the image signal output from the line delay unit 204 into, for example, a standard color space of NTSC-RGB by the matrix operation of Formula 1. That is, the color space of each color component signal output from the full-color sensor 34 is determined by the spectral characteristics of the filter of each color component.
The conversion into the B standard color space.

[0026]

(Equation 1)

The input interface 250 receives color image data from an external device (not shown) such as a computer as necessary.

The LOG conversion unit 206 is constituted by, for example, a look-up table (LUT) composed of a ROM or the like (not shown), and the RGB output from the input masking unit 205.
The luminance signal is converted into a CMY density signal.

The line delay memory 207 includes a LOG conversion unit 206 for a period (line delay period) during which a black character determination unit (not shown) generates a control signal UCR, FILTER, SEN, or the like based on the output of the input masking unit 205. The image signal output from is delayed.

It should be noted that the control signal UCR is equal to the masking UC
A control signal for controlling the R unit 208. The control signal FILTER is a control signal used by the output filter 210 to perform edge enhancement. Also, the control signal SE
N is a control signal used to increase the resolution when a black character determination unit (not shown) determines a black character.

The masking / UCR unit 208 extracts a black component signal K from the image signal output from the line delay memory 207. Further, in order to correct the color turbidity of the recording color material in the printer unit, a matrix operation is performed on the MCYK image signal, and M, C,
For example, an 8-bit plane-sequential color component image signal is output in the order of Y and K. The matrix coefficients used for the matrix calculation are set by a CPU (not shown) in the controller 100.

The image area width measuring section 230 will be described later.

The gamma correction unit 209 performs density correction on the image signal output from the image area width measurement unit 230 so that the image signal matches the ideal gradation characteristics of the printer unit. The output filter (spatial filter processing unit) 210 performs edge enhancement or smoothing processing on the image signal output from the γ correction unit 209 according to a control signal from a CPU (not shown) in the controller 100.

The LUT 211 includes an LUT (not shown) for matching the density of the original image with the density of the output image;
Further, an LUT for mutually correcting gradation between adjacent pixels.
(Hereinafter, referred to as a mutual correction LUT of two adjacent pixels), and is configured by a RAM or the like. In the present embodiment, the above-described LUT of FIG. 10 is employed as an example of the mutual correction LUT of two adjacent pixels according to the following description.

The pulse width modulator (PWM) 212 has an LU
A pulse signal having a pulse width corresponding to the level of the image signal input from T211 is output, and the pulse signal is input to a laser driver 41 (laser driver 3 in FIG. 1) for driving a laser light source (not shown).

In FIG. 1, a laser beam E emitted from a semiconductor laser in a laser driver 3 is rotated by a polygon mirror 3a.
Lens 3b such as an f / θ lens and a fixed mirror 3 for directing the laser beam E toward the photosensitive drum 1.
The spot image is formed on the photosensitive drum 1 by c. The laser beam E scans the photosensitive drum 1 in a direction substantially parallel to the rotation axis of the photosensitive drum 1 (main scanning direction), and repeatedly scans the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 (sub-scanning direction).
To form an electrostatic latent image.

In the printer section, the photosensitive drum 1 has amorphous silicon, selenium, OPC, etc. on its surface.
It is supported rotatably in the direction of the arrow in FIG. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2,
Laser exposure optical system 3, surface potential sensor 12, four developing units 4y, 4c, 4m, 4bk of different colors, photosensitive drum 1
The upper light amount detecting means 13, the transfer device 5, and the cleaning device 6 are arranged.

In the printer section, the controller 200
Prior to image formation, the photosensitive drum 1 is rotated in the direction of the arrow in FIG. 1 and is uniformly discharged by the pre-exposure lamp 11, and then uniformly charged by the primary charger 2. Thereafter, the photosensitive drum 1 is exposed and scanned by the laser light E modulated according to the above-described image information signal, so that an electrostatic latent image having an area gradation characteristic is formed according to the image information signal. 1 is formed.

The developing units 4y, 4c, 4m, and 4bk develop the electrostatic latent images on the photosensitive drum 1 using yellow, magenta, cyan, and black color toners as recording materials, respectively. Specifically, the controller 200 converts the electrostatic latent image formed on the photosensitive drum 1 into a predetermined developing device 4
A negatively-charged visible image (toner image) using a resin as a substrate is formed on the photosensitive drum 1 by performing reversal development using a two-component developer composed of a toner and a carrier according to y, 4c, 4m, and 4bk. These toners are formed by using a styrene copolymer resin as a binder and dispersing recording materials of each color. Each developing device is provided with an eccentric cam 24y, 2
By the operation of 4c, 24m, and 24bk, a structure is provided in which the photosensitive drum 1 is selectively approached in accordance with each separated color. Here, the reversal development is a development method in which a toner charged to the same polarity as the latent image is attached to a region of the photoconductor exposed to light, and the toner is visualized.

In the present embodiment, the transfer device 5 includes a transfer drum 5a, a transfer brush charger 5b as transfer means, a suction roller 5g opposed to a suction brush charger 5c for electrostatically adsorbing recording paper, and an inner charger. 5d, outer charger 5e,
And a transfer peeling sensor 5h. In addition, in the peripheral opening area of the transfer drum 5a which is rotatably supported,
A recording paper holding sheet 5f made of a dielectric material such as polycarbonate is integrally stretched in a cylindrical shape.

The controller 200 controls the recording paper cassette 7
The transfer system and the transfer device 5 transfer the recording paper in the
And is supplied to a position facing the photosensitive drum 1 via the recording medium holding sheet 5f by electrostatic force. Then, the toner image formed on the photosensitive drum 1 is transferred to the transfer drum 5a.
Is transferred onto the recording paper on the recording paper holding sheet 5f according to the rotation of.

When the transfer of the toner image of the original image onto the recording paper is completed, the controller 200 separates the recording paper from the transfer drum 5a by operating the separation claw 8a, the separation push-up roller 8b, and the separation charger 5h. After the toner image is fixed on the recording paper by the roller fixing device 9, the toner image is discharged onto the tray 10.

After transferring the toner image, the controller 200 cleans the residual toner on the surface of the photosensitive drum 1 with the cleaning device 6 including the cleaning blade 6a and the squeeze sheet, and prepares for the next image forming process. Further, in order to prevent scattering of powder on the recording paper holding sheet 5f of the transfer drum 5a, adhesion of oil on the recording paper, etc., the fur brush 14 and the fur brush 14 are interposed via the recording paper holding sheet 5f. Cleaning is performed using the backup brush 15 facing the cleaning brush. Such cleaning is performed before or after image formation, and is performed as needed when a jam (paper jam) occurs.

Next, the operation of the image area width measuring section 230 will be described. The image area width measuring unit 230 is configured to perform the following based on the image signal output from the masking / UCR unit 208.
From one image represented by the image signal, an image area of a predetermined size consisting of a plurality of pixels having data such as density and luminance within a predetermined level range is detected.

As a method for measuring the width of the image area, for example, a method proposed in the above-mentioned Japanese Unexamined Patent Publication No. Hei 7-273983 or Japanese Unexamined Patent Publication No. Hei 7-203198 is adopted. Here, the outline of the method will be described.

First, an input image signal is binarized using a predetermined density value (for example, density 0.3) as a threshold value.
1 is a black pixel and 0 is a white pixel. Next, for example, 2 × 2
A matrix of pixels, in which all the pixels are 1 (black), is sequentially moved downward from left to right in a 2 × 2 pixel matrix in a region represented by the image signal. Take AND while moving to. Such a process is performed for all pixel areas for which the image area width is to be measured.

If the upper left pixel of the matrix is set as the target pixel and AND is taken, both the calculation result of the target pixel and the calculation result of the lower pixel of the target pixel are 1 (black). For example, it has a plurality of pixel widths in the downward direction. Similarly, if both the calculation result for the pixel of interest and the calculation result for the pixel on the right side of the pixel of interest are 1 (black), it indicates that the pixel has a plurality of pixel widths in the horizontal direction. When the area to be measured is a line having a width of one pixel, 1 and 0 are included in the AND result. Therefore, by utilizing the difference in the result of taking the AND, whether the pixel of interest is one pixel wide,
Alternatively, it is determined whether the pixel is included in a region having a plurality of pixel widths.

However, even if it is determined that the area has a plurality of pixel widths, when the matrix of 2 × 2 pixels is sequentially moved downward from left to right in the area,
When the matrix of 2 × 2 pixels moves on the right side and the lower side of the area, the operation result of three pixels other than the pixel of interest in the matrix becomes 0 (white), and that part has a width of one pixel. The line will be determined. Therefore, in such a case, when the result of the operation when the matrix moves one step up is 1 (black), it is determined that the line having the one pixel width belongs to the upper black pixel area. Accurate measurement of the image area width is realized.

Next, the features of the gradation correction in this embodiment will be described. In the present embodiment, the method of mutually correcting two adjacent pixels is based on the general method described above with reference to FIGS. That is, the adjacent pixels are
Rows A, B, A, B,... In the main scanning direction. When gradation correction is performed on the image data of each pixel in the rows A and B, for example, the correction is performed based on different characteristic curves for the rows A and B of the LUT shown in FIG. The data of these tables is stored in advance in, for example, the ROM 213 or the like, and is set in the LUT 211 by the CPU 214.

Further, the adverse effect on the output image in the low-density range when two adjacent pixels are mutually corrected, that is, as described with reference to FIG. If the output signal from the image area width measuring unit 230 indicates that the image area including the pixel of interest has only one image width in the main scanning direction, the controller The reference numeral 200 prohibits the tone correction processing by the LUT 211 for the image data of the target pixel, and passes it to the PWM 212 as it is. Thereby, when the input image has an image width of one pixel,
An output image can be output at 400 dpi.

In the following description, the low concentration region is defined as
For example, it refers to a density of 0.8 or less in a commercially available densitometer.

FIG. 3 is a flowchart showing a mutual correction process of two adjacent pixels according to the first embodiment of the present invention. The software that realizes this processing is stored in ROM 21 in advance.
3 according to the software.
214 performs.

In FIG. 5, in step S 1, a pixel (hereinafter referred to as a pixel of interest) as multi-valued color image data input this time to the LUT 211 is included by referring to an output signal from the image area width measuring unit 230. It is determined whether the image area has an image width of only one pixel in the main scanning direction. Then, if YES is determined in the step S1, the image data of the target pixel is output to the PWM 212 as it is in a step S5. That is, the mutual correction processing of two adjacent pixels is not performed.

On the other hand, if NO in step S1, it is determined whether the pixel of interest is a pixel in column A (step S2).

If YES in step S2, tone correction is performed using the characteristic curve for column A of the LUT (step S2).
3). Then, the image data whose gradation has been corrected in step S3 is output to the PWM 212 in step S5.

On the other hand, in the case of NO in step S2, since the pixel is in the B column, gradation correction is performed using the characteristic curve for the B column of the LUT (step S4). Then, the image data whose gradation has been corrected in step S4 is converted to PWM2 in step S5.
12 is output.

In the actual correction process for each pixel, the distribution of the LUT to the characteristic curve for column A or the characteristic curve for column B may be performed using the pixel clock VCLK.

FIG. 4 is a diagram for explaining an output image of a thin line according to the first embodiment of the present invention. As shown in FIG. 9A, when the input image is one pixel in the main scanning direction, both the A and B columns are output as output images as they are. Therefore, if the input image represents a diagonal line as a whole, the diagonal line can be reproduced as a diagonal line in the output image.

[Second Embodiment] In the first embodiment,
When the input image is one pixel in the main scanning direction, mutual correction of two adjacent pixels is prohibited and output is performed on 400 lines. Here, a problem in the first embodiment will be raised.

As shown in FIG. 10A, a certain image area included in the input image has an odd number (2n + 1) in the main scanning direction.
Consider the case of low-density image data that has the width of a pixel in a column and that pixel is smaller than a predetermined density value.
In this case, the output image is as shown in (B1) of FIG.
The pixel in column A is located in column 2n and the pixel in column B is located in column (2n + 1). As shown in FIG. 5B2, the pixel in column A is located at column (2n + 1) and the column 2n is located at column (2n + 1). Is different from the case where the pixels in the B column are located at the same time, and there is a problem that the density and width of the image reproduced macroscopically change.

Therefore, in the present embodiment, when the width of the image area is, for example, 15 pixels or less, the mutual correction processing of two adjacent pixels is prohibited. Therefore, in the present embodiment, in the determination in step S1 in the flowchart of FIG. 3 described above, it is determined whether or not the image area including the target pixel has an image width of 15 pixels or less in the main scanning direction. Processing other than step S1 is the same as in the first embodiment, and a description thereof will not be repeated.

According to the present embodiment, it is possible to prevent a change in shading and width of a line having an odd pixel width as described with reference to FIG. 5, reduce jaggies such as oblique lines, and obtain a good image. Is obtained.

[Third Embodiment] In the third embodiment,
As shown in FIG. 6, as a result of the mutual correction processing of two adjacent pixels,
The output images were arranged in a staggered arrangement.

FIG. 7 is a flowchart showing a mutual correction process of two adjacent pixels according to the third embodiment of the present invention. The software that realizes this processing is stored in ROM 21 in advance.
3 according to the software.
214 performs.

Referring to FIG. 11, in step S11, the image area including the target pixel has an image width of only one pixel in the main scanning direction by referring to the output signal from the image area width measuring unit 230. Determine if there is. Then, in the case of YES in step S11, the image data of the target pixel is directly subjected to PWM 212 in step S17.
Output to That is, the mutual correction processing of two adjacent pixels is not performed.

On the other hand, if NO in step S11, it is determined whether the pixel of interest is an odd-numbered row pixel (step S1).
2). If YES in step S12 (pixels in odd-numbered rows), it is determined whether the pixel is a pixel in column A (step S13).

If YES in step S13, LU
Tone correction is performed using the characteristic curve for column A of T (step S15). Then, the image data whose gradation has been corrected in step S15 is output to the PWM 212 in step S17. On the other hand, if NO in step S13, since the pixel is a pixel in column B, tone correction is performed using the characteristic curve for column B of the LUT (step S16), and the flow proceeds to step S17.

On the other hand, if NO in step S12, it is determined whether the pixel of interest is a pixel in column A (step S1).
4). In the case of YES in step S14, the processing after step S16 is performed. On the other hand, if NO in step S14
In the case of the above, since the pixels are in the B column, the above-described step S15
The following processing is performed.

It should be noted that, during the actual correction processing for each pixel, in order to distribute to the characteristic curve for column A or the characteristic curve for column B of the LUT according to whether the row is an odd row or an even row,
The pixel clock VCLK may be used.

By performing the staggered gradation correction in this manner, the resolution becomes equivalent to 283 dpi at an oblique angle of 45 degrees, and the maximum distance between dots is about 2 × 200 × 400 dpi.
/ 3. Therefore, according to the present embodiment, it is possible to prevent a thin line thin enough to be undetectable by the image area width measuring unit 230, in particular, that a straight line parallel to the main scanning direction and the sub-scanning direction is not reproduced in the output image. it can.

It is needless to say that this embodiment may detect an image having a plurality of pixel widths as in the second embodiment.

[Fourth Embodiment] In each of the above-described embodiments, the width of the image area is measured over the entire density range of the input image to be reproduced, and an image having a predetermined pixel width in the main scanning direction is measured. , The mutual correction of two adjacent pixels is prohibited. In this case, when the number (width) of a plurality of pixels adjacent in the main scanning direction in an image area is odd and the image area has a density lower than a certain density value, the input image is reproduced. In some cases, jaggies such as shading, width changes, and diagonal lines may be conspicuous. Therefore, in the present embodiment, the image area including the target pixel has a density lower than a predetermined density value (for example,
Mutual correction of two adjacent pixels is performed only when the density is 0.8) and the width of the image in the main scanning direction is larger than, for example, 15 pixels.

By adopting such a processing, when the input image is reproduced, changes in shading and width, jaggies such as oblique lines can be reduced, and the time required for processing in the image area width measuring section 230 can be reduced. Therefore, the time required for image formation can be reduced as a whole.

[Fifth Embodiment] In each of the embodiments described above, the present invention is applied to a color copying machine. However, the present invention is also effective for a monochrome copying machine. The control of the tone correction itself is the same as in each of the above-described embodiments, and a description thereof will be omitted.

FIG. 8 is a diagram showing a configuration of a monochrome digital copying machine as a fifth embodiment of the present invention. The basic configuration is the same as that of the case of color, but in brief, when a copy start key (not shown) is pressed, the CPU 2
Reference numeral 8 denotes a document 101 placed on a platen glass 102
The exposure scan by the exposure lamp 103 is started. A reflected light image from the document 101 obtained by this exposure scanning is transmitted through a lens 104 to a CCD (Charge Coupled Device).
ce) Focused on 105, analog / digital (A / D)
Input to the converter 22.

The A / D converter 22 receives the original 10
The reflected light image from 1 is divided into a plurality of pixels by a plurality of photoelectric conversion elements, and a photoelectric conversion signal (digital signal) is generated according to the density of each pixel.

The CPU 28 drives a pulse width modulator (PWM) 107 in accordance with the input photoelectric conversion signal, and the PWM 107 outputs a pulse signal having a pulse width corresponding to the level of the input image signal. The pulse signal is input to the laser driver 1 that drives the laser light source 107.

The laser beam E emitted from the semiconductor laser in the laser driver 1 is swept by the rotary polygon mirror 400 and scans the photosensitive drum 4 to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 4 is
The image is reversely developed by the developing device 5 to form a visible image (toner image). Then, the toner image is transferred onto the recording paper 500 transported by a transport unit (not shown), and is thermally fixed by the rollers 7.

In the monochrome copying machine having such a configuration, even if the tone correction control of each of the above embodiments is performed,
Changes in shading and width, and diagonal jaggies are reduced,
Good images can be obtained.

[Other Embodiments] The present invention relates to a plurality of devices (for example, a host computer, an interface device,
The present invention may be applied to a system including a reader, a printer, or the like, or may be applied to an apparatus (for example, a copying machine, a facsimile machine, a printer, or the like) including one device.

An object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or a CPU or M
Needless to say, this can also be achieved by the PU) reading and executing the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

Examples of a storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, and CD.
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0086]

As described above, according to the present invention,
An image processing apparatus and an image processing method that satisfactorily reproduce an image in a low density region and a halftone image are realized.

[0087]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a digital copying machine as a first embodiment of the present invention.

FIG. 2 is a block diagram of an image forming process in the digital copying machine according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a mutual correction process of two adjacent pixels according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an output image of a thin line according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining a problem when mutual correction processing of two adjacent pixels according to the first embodiment is performed.

FIG. 6 is a diagram illustrating a concept of a mutual correction process of two adjacent pixels according to a third embodiment of the present invention.

FIG. 7 is a flowchart illustrating a mutual correction process of two adjacent pixels according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a monochrome digital copying machine as a fifth embodiment of the present invention.

FIG. 9 is a diagram illustrating a method of mutually correcting two adjacent pixels.

FIG. 10 is a diagram illustrating an example of an LUT used to mutually correct two adjacent pixels.

FIG. 11 shows input image data from low density to high density in FIG.
FIG. 9 is a diagram illustrating an output image of an image in the area gradation method when gradation correction is performed by an LUT of 0.

12 is a diagram illustrating an example of an output image when an input image is corrected by the LUT in FIG.

FIG. 13 is a diagram illustrating a problem when oblique lines are corrected by a general method of mutually correcting two adjacent pixels.

Claims (10)

[Claims] 1. An image area of a predetermined size comprising a plurality of pixels included in an image represented by an input image signal, wherein each of the plurality of pixels has a predetermined image component signal within a predetermined level range. Detecting means for detecting an area; correcting means for performing gradation correction on a plurality of pixels adjacent to the image according to different correction characteristic information; and an image area including a pixel of interest by the detecting means having a predetermined width. An image processing apparatus comprising: control means for performing control to prohibit gradation correction by the correction means when detecting that there is no gradation correction. 2. The control unit according to claim 1, wherein said image area does not have a predetermined width, and said plurality of pixels forming said image area each have a density lower than a predetermined density value. 2. The image processing apparatus according to claim 1, wherein gradation correction is prohibited. 3. The image processing apparatus according to claim 2, wherein the predetermined image component signal has a density and / or
2. The image processing apparatus according to claim 1, wherein the signal is a signal representing luminance. 4. The image processing apparatus according to claim 1, wherein the correcting unit performs gradation correction on odd-numbered column pixels and even-numbered column pixels adjacent to each other in the main scanning direction of the image represented by the image signal according to different correction characteristic information. The image processing device according to claim 1. 5. The image processing apparatus according to claim 4, wherein said control means prohibits gradation correction by said correction means when said image area does not have a predetermined width in the main scanning direction. apparatus. 6. The image processing apparatus according to claim 4, wherein the predetermined width of the image area is at least one pixel width in the main scanning direction. 7. An image area of a predetermined size comprising a plurality of pixels included in an image represented by an input image signal, wherein each of the plurality of pixels has a predetermined image component signal within a predetermined level range. A detection step of detecting an area; and a correction step of performing tone correction on a plurality of pixels adjacent to the image in accordance with different correction characteristic information, wherein the image area including the pixel of interest has a predetermined width by the detection step. An image processing method comprising: prohibiting tone correction in the correction step when it is detected that the image data does not have. 8. The image area does not have a predetermined width,
8. The image processing method according to claim 7, wherein when a plurality of pixels constituting the image area each have a density lower than a predetermined density value, the tone correction in the correction step is prohibited. 9. A computer-readable storage medium storing an image processing program for performing gradation correction on an input image signal, the program comprising a computer-readable storage medium having a predetermined size comprising a plurality of pixels included in the image. A code for a detection step of detecting an image area in which the plurality of pixels each have a predetermined image component signal within a predetermined level range; and a plurality of adjacent pixels of the image each having different correction characteristic information. A code of a correction step for performing tone correction according to the following: and a control for performing control for inhibiting the tone correction by the correction step when the detection step detects that the image area including the pixel of interest does not have a predetermined width. And a process code. 10. The code in the control step, wherein the correction is performed when the image area does not have a predetermined width and a plurality of pixels constituting the image area each have a density lower than a predetermined density value. 10. The storage medium according to claim 9, wherein gradation correction by a process is prohibited.