JPH08186704A - Magnified data generator in digital copying machine - Google Patents

Abstract

PURPOSE: To prevent the contour part of a character from blurring and the line width of the character from being changed by density adjustment. CONSTITUTION: This generator is provided with a magnification interpolation processing means 11 and a contour emphasis processing means 12. The contour emphasis processing means 12 is provided a first means for obtaining a minimum picture element density and maximum picture element density within the density judgment area of a prescribed size whose center is a picture element under consideration and with a second means in which a density range between the minimum picture element density and the maximum picture element is divided into the three ranges of a low density range, an intermediate density range and a high density range corresponding to a set magnifying power, the density of the picture element under consideration is converted to the minimum picture element density when a difference between the density of the picture element under consideration and the minimum picture element density is within the low density range, the density of the picture element under consideration is converted to the maximum picture element density when the difference is within the high density range and the density of the picture element under consideration is converted to the density corresponding to the difference between the density of the picture element under consideration and the minimum picture element density when the difference is within the intermediate density range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnified image data generating device in a digital copying machine.

[0002]

2. Description of the Related Art In a digital copying machine, an original image is input by a CCD or the like, the input data is multivalued, and the result is output as a multivalued image.

At the time of enlargement, in order to perform enlargement in the sub-scanning direction, the moving speed of the optical system is slowed according to the enlargement magnification, and the scanning line width on the original corresponding to one pixel is narrowed. Further, in order to perform enlargement in the main scanning direction on the multivalued data after the multivalued processing, the following enlargement interpolation processing is performed.

That is, a number of pixel data corresponding to the set enlargement magnification is interpolated between the adjacent pixels according to the density gradient of the adjacent pixels (the target pixel and the next pixel) in the main scanning direction.
Assuming that the density of the pixel of interest is ID _n , the density of the next pixel is ID _{n + 1} , and the density of the interpolation pixel is AD _m , the density AD of the interpolation pixel is AD.
_m is determined as follows.

When the number of interpolated pixels is one, that is, when the enlargement factor is two, the density AD _{1 of the} interpolated pixel is determined based on the following equation 1.

[0006]

## EQU1 ## AD ₁ = ID _n + (ID _{n + 1} -ID _n ) .1 / 2

When the number of interpolated pixels is 2, that is, when the enlargement factor is 3, the densities AD ₁ and AD _{2 of the} interpolated pixels are determined based on the following equation (2).

[0008]

[Number 2] _{AD 1 = ID n + (ID} n + 1 -ID n) · 1/3 AD 2 = ID n + (ID n + 1 -ID n) · 2/3

When the number of interpolated pixels is 3, that is, when the enlargement factor is 4, the densities AD ₁ , AD ₂ , and AD _{3 of the} interpolated pixels are determined on the basis of the following formula 3.

[0010]

## EQU00003 ## AD ₁ = ID _n + (ID _{n + 1} −ID _n ) · 1/4 AD ₂ = ID _n + (ID _{n + 1} −ID _n ) · 2/4 AD ₃ = ID _n + (ID _{n + 1-} ID _n ) ・ 3/4

[0011]

By the conventional enlargement interpolation processing described above, an enlarged image having a smooth contour without jaggies can be obtained. However, when a magnified image is obtained using the magnified image data obtained by the magnifying interpolation processing as described above, there is a problem that the outline portion of the character for which the density difference is desired to be clear is blurred. Further, when the density adjustment is performed on the enlarged image data obtained by the above-described enlargement interpolation processing, there is a problem that the line width of the character becomes thick or thin.

According to the present invention, the outline of a character is blurred,
It is an object of the present invention to provide a magnified image data generation device in a digital copying machine which can prevent the line width of characters from changing due to density adjustment.

[0013]

A first magnified image data generating device in a digital copying machine according to the present invention has a number of pixel data corresponding to a set magnifying power according to a density gradient of adjacent pixels in the main scanning direction. Is provided between the adjacent pixels, and an edge enhancement processing means for performing edge enhancement processing on the pixel data after the extension interpolation processing. The edge enhancement processing means is centered on the pixel of interest. A first means for obtaining the minimum pixel density and the maximum pixel density in a density determination area of a predetermined size, and a density range between the minimum pixel density and the maximum pixel density are a low density range and an intermediate density range depending on a set enlargement magnification. If the difference between the target pixel density and the minimum pixel density is within the low density range, the target pixel density is converted into the minimum pixel density, and When the difference between the pixel density and the minimum pixel density is within the high density range, the target pixel density is converted to the maximum pixel density, and the difference between the target pixel density and the minimum pixel density is within the intermediate range. Further comprises second means for converting the target pixel density into a density corresponding to a difference between the target pixel density and the minimum pixel density within a density range between the minimum pixel density and the maximum pixel density. Characterize.

As the second means, for example, the target pixel density is S, the minimum pixel density is L _th , the maximum pixel density is H _th, and the set enlargement magnification is α, and the first means is
The index k is calculated as (2α−1) · {(S−L _th ) / (H _th −L
_th )}-(α-1), a second index K based on the calculated first index k, if k ≦ 0, K = 0, if k ≧ 1 When K = 1 and 0 <k <1, means for obtaining based on the rule of K = k and the obtained second index K are used to set the target pixel density S to (H _th
A unit having a means for converting the density based on the formula −L _th ) K + L _th is used.

The second magnified image data generating apparatus in the digital copying machine according to the present invention provides the pixel data of the number corresponding to the set magnification in accordance with the density gradient of the adjacent pixels in the main scanning direction between the adjacent pixels. And an edge enhancement processing means for performing edge enhancement processing on the pixel data after the extension interpolation processing. The edge enhancement processing means is preset with a preset minimum pixel density. The density range between the maximum pixel density and the maximum pixel density is divided into three ranges, a low density range, an intermediate density range, and a high density range, according to the set magnification, and the difference between the target pixel density and the minimum pixel density is within the low density range. If the difference between the target pixel density and the minimum pixel density is within the high density range, the target pixel density is converted to the maximum pixel density. If the difference between the target pixel density and the minimum pixel density is within the intermediate range, the difference between the target pixel density and the minimum pixel density is determined within the density range between the minimum pixel density and the maximum pixel density. It is characterized in that the density of the pixel of interest is converted into another density.

As the contour enhancement processing means, for example, the target pixel density is S, the minimum pixel density is L _th ,
_Letting H _{th be the} maximum pixel density and α be the set enlargement magnification, the first index k is (2α−1) · {(S−L _th ) /
Means for calculating based on the formula (H _th −L _th )} − (α−1), the second index K based on the calculated first index k,
If k ≦ 0, K = 0; if k ≧ 1, K = 1, 0 <k
If <1, then means for obtaining based on the rule that K = k,
And using the obtained second index K, the target pixel density S
Is provided with a means for converting the density based on the formula of (H _th −L _th ) K + L _th .

[0017]

The first aspect of the digital copying machine according to the present invention
In the enlarged image data generation device, the pixel data of the number corresponding to the set enlargement magnification is interpolated between the adjacent pixels according to the density gradient of the adjacent pixels in the main scanning direction. Then, the contour emphasis processing is performed on the pixel data after the enlargement interpolation processing.

The contour enhancement processing is performed as follows.
That is, first, the minimum pixel density and the maximum pixel density in the density determination area of a predetermined size centered on the target pixel are obtained. Then, the density range between the minimum pixel density and the maximum pixel density is divided into three ranges of a low density range, an intermediate density range, and a high density range according to the set enlargement magnification, and the target pixel density and the minimum pixel density are When the difference between and is within the low density range, the target pixel density is converted to the minimum pixel density. When the difference between the target pixel density and the minimum pixel density is within the high density range, the target pixel density is converted to the maximum pixel density. If the difference between the target pixel density and the minimum pixel density is within the intermediate range, the difference between the target pixel density and the minimum pixel density is determined within the density range between the minimum pixel density and the maximum pixel density. The density of the pixel of interest is converted into the density of interest.

In the second enlarged image data generating apparatus in the digital copying machine according to the present invention, the pixel data of the number corresponding to the set enlargement magnification is set between the adjacent pixels in accordance with the density gradient of the adjacent pixels in the main scanning direction. Is interpolated to. And
Contour enhancement processing is performed on the pixel data after the expansion interpolation processing.

The contour enhancement processing is performed as follows.
That is, the density range between the preset minimum pixel density and the preset maximum pixel density is divided into three ranges, a low density range, an intermediate density range, and a high density range, according to the set magnification ratio. When the difference between the pixel density and the minimum pixel density is within the low density range, the target pixel density is converted to the minimum pixel density. When the difference between the target pixel density and the minimum pixel density is within the high density range, the target pixel density is converted to the maximum pixel density. When the difference between the target pixel density and the minimum pixel density is within the intermediate range, the difference between the target pixel density and the minimum pixel density is determined within the density range between the minimum pixel density and the maximum pixel density. The density of the pixel of interest is converted into the density of interest.

[0021]

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 shows an image data processing circuit of a digital copying machine.

Here, the enlargement magnification α (α
The operation of the image data processing circuit when> 1) is set will be described. Since the enlargement ratio α is set, the moving speed of the optical system is slowed in accordance with the enlargement ratio α during copying in order to perform enlargement in the sub-scanning direction, and the scanning line width on the original corresponding to one pixel is reduced. To be narrowed.

The pixel data read by the CCD 1 is converted into multi-valued data representing the density of a predetermined plurality of levels in the multi-valued processing section 2. The multi-valued pixel data output from the multi-valued processing unit 2 is sent to the enlarged image data generation unit 3. The magnified image data generation unit 3 generates magnified image data according to the set magnification. Enlarged image data generator 3
The enlarged image data obtained by the above is sent to the density adjusting unit 4. The density adjusting unit 4 obtains output data (output gradation) from the density (input gradation) of each input pixel data based on the input gradation / output gradation table. The output data thus obtained is sent to the image output unit.

FIG. 2 shows the structure of the enlarged image data generating section 3.

The magnified image data generating section 3 includes a magnifying interpolation processing section 11 and a contour emphasizing processing section 12. As described above, the enlargement interpolation processing unit 11 responds to the multi-valued pixel data from the multi-valued processing unit 2 according to the density gradient of the adjacent pixels (the target pixel and the next pixel) in the main scanning direction. , The number of pixel data corresponding to the set enlargement ratio is interpolated between the adjacent pixels. The densities of the respective interpolated pixels are determined by the method as shown in Equations 1 to 3 above.

The operation of the contour emphasis processing section 12 will be described. Let S be the density of the pixel of interest in the pixel data after the enlargement interpolation processing by the enlargement interpolation processing unit 11. The maximum pixel density H _th and the minimum pixel density L _th are detected from an area composed of pixels of n rows × m columns centering on the pixel of interest (hereinafter referred to as density determination area). N in the density determination area is a natural number of 2 or more, and m in the density determination area is a natural number of 1 or more. When the set enlargement factor is α, it is preferable to set n in the density determination area to a number obtained by n = 2α + 1. In addition, m of the density determination region is set to 3
It is preferable to set to ~ 5.

Next, the first index k is obtained by the following equation 4.

[0029]

Equation 4] k = (2α-1) · {(S-L th) / (H th -
L _th )}-(α-1)

The first index k indicates at which density position the density S of the pixel of interest is between the minimum pixel density L _th and the maximum pixel density H _th in the density determination area centered on it. It is an index.

For example, when the enlargement factor α is 2, k = _3 {(S-L _th ) / (H _th- L _th )}-1. Therefore, (S−L _th ) is 1 of (H _th −L _th ).
When it is / 3 or less, k is 0 or less (k ≦ 0). If (S-L _th) is 2/3 or more (H _th -L _th) is, k is 1 or more (k ≧ 1). (S-L _th )
Is larger than 1/3 of (H _th −L _th ) and smaller than 2/3, k becomes a value within the range of 0 <k <1.

For example, when the enlargement factor α is 3, k = _5 {(S-L _th ) / (H _th- L _th )}-2. Therefore, (S−L _th ) is 2 of (H _th −L _th ).
When it is / 5 or less, k is 0 or less (k ≦ 0). If (S-L _th) is 3/5 or more (H _th -L _th) is, k is 1 or more (k ≧ 1). (S-L _th )
Is larger than 2/5 and smaller than 3/5 of (H _th −L _th ), k takes a value within the range of 0 <k <1.

For example, when the enlargement factor α is 4, k = _7 {(S-L _th ) / (H _th- L _th )}-3. Therefore, (S−L _th ) is 3 of (H _th −L _th ).
When it is / 7 or less, k is 0 or less (k ≦ 0). If (S-L _th) is 4/7 or more (H _th -L _th) is, k is 1 or more (k ≧ 1). (S-L _th )
Is larger than 3/7 and smaller than 4/7 of (H _th −L _th ), k takes a value within the range of 0 <k <1.

Then, the second index K is obtained by the discriminant expressed by the following equation 5.

[0035]

## EQU00005 ## If k.ltoreq.0, then K = 0. If k ≧ 1, then K = 1. If 0 <k <1, then K = k.

As the second index K, the density range of the minimum pixel density L _th and the maximum pixel density H _th of the density determination area with the density S of the pixel of interest as the center is set to three values according to the enlargement ratio α. When divided into ranges, it is an index indicating which range it belongs to.

For example, when the enlargement factor α is 2,
Minimum pixel density L in the density determination area _thAnd maximum pixel density H
_thBetween the maximum and minimum density difference (H_th-L_th) 1/3 or more
Lower low density range, high density of 2/3 or more of maximum and minimum density difference
It is divided into ranges and intermediate concentration ranges in between.
When the enlargement factor α is 3 times, the minimum density determination area
Pixel density L_thAnd maximum pixel density H_thBetween and is the maximum
Low density range of 2/5 or less of degree difference, 3 / of maximum and minimum density difference
High concentration range of 5 or more and intermediate concentration range between them
Is divided into If the magnification α is 4 times, the above density
Minimum pixel density L in the judgment area_thAnd maximum pixel density H_thBetween
Is a low concentration range of 3/7 or less of the maximum and minimum concentration difference, maximum and maximum
High density range of 4/7 or more of small density difference and their middle
Is divided into intermediate concentration ranges.

[0038] Then, the difference between the concentration S and the minimum pixel density L _th of the pixel of interest (S-L _th) becomes the K = 1 when the when in a low concentration range is K = 0, and the high concentration range. When the difference between the density S of the pixel of interest and the minimum pixel density L _th is in the intermediate density range, K is between 0 and 1 (0 <K
<1).

Next, the pixel density S of interest is converted based on the following equation (6). The pixel data obtained after the conversion is sent to the density adjusting unit 4.

[0040]

[Equation 6] S ′ = (H _th −L _th ) K + L _th

The density S of the pixel of interest and the minimum pixel density L_thWith
If the difference is in the low concentration range, K = 0, so
The pixel density S'after conversion is the minimum pixel in the density determination area.
Value L _thBecomes The density S of the pixel of interest and the minimum pixel density L_thWhen
When the difference of is in the high concentration range, K = 1, so
The converted pixel density S ′ is the maximum image density in the density determination area.
Elementary value H_thBecomes

When the difference between the density S of the pixel of interest and the minimum pixel density L _th is in the intermediate density range, K takes a value within the range of 0 to 1, so that the pixel density S ′ after conversion is The value is proportional to the difference between the _target pixel density S and the minimum pixel density L _th . Therefore, the converted pixel density S ′ is between the minimum pixel density L _th and the maximum pixel value H _th in the density determination region,
The density is proportional to the difference between the _target pixel density S and the minimum pixel density L _th .

As described above, the density range of the minimum pixel density L _th and the maximum pixel density H _th in the density determination area centering on each pixel after the expansion interpolation processing is divided into three, and that density of that pixel is when the difference between the density S and the minimum pixel density L _th is within a low concentration range is converted the pixel density is a minimum pixel density L _th, the difference is high density range between the density S and the minimum pixel density L _th of the pixel When it is within the range, the pixel density is converted into the maximum pixel density H _th , and the density S of the pixel and the minimum pixel density L _th
And the pixel density is within the intermediate density range, the pixel density is converted to an intermediate value between the minimum pixel density L _th and the maximum pixel density H _th .

Therefore, of the pixels including the interpolated pixels, when the pixel of interest is within the black character area, for example,
When the target pixel density is converted to the maximum pixel density of the character area and the target pixel is outside the character area, the target pixel density is converted to the minimum pixel density outside the character area, so that the outline of the character becomes clear and The width of the lines that make up characters and the like is also constant.

In the above embodiment, n with the pixel of interest at the center
The maximum pixel density H _th and the minimum pixel density L _th are detected from the density determination area composed of pixels of rows × m columns. However, without performing such detection, the maximum pixel density H _th and the minimum pixel density L _th can be freely set,
The densities of the respective pixels after the expansion interpolation processing may be converted based on the equations 4 to 6.

For example, in the case where the multilevel halftoning processing section 2 generates multilevel halftoning data representing densities of 255 levels from 0 to 254, the maximum pixel density H _{th is set} to 254 and the minimum pixel density L is set to 254.
You may set _th to 0. Further, an arbitrary value A may be set to the minimum pixel density L _th within the density range of 0 to 254, and an arbitrary value B larger than A may be set to the maximum pixel density H _th within the density range. .

[0047]

According to the present invention, it is possible to prevent the outline portion of a character from being blurred and the line width of the character from changing due to density adjustment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image data processing circuit of a digital copying machine.

FIG. 2 is a block diagram showing a configuration of an enlarged image data generation unit.

[Explanation of symbols]

 1 CCD 2 Multi-value processing unit 3 Enlarged image data generation unit 11 Enlargement interpolation processing unit 12 Edge enhancement processing unit

Claims (4)

[Claims] 1. An enlargement interpolation processing means for interpolating a number of pixel data corresponding to a set enlargement magnification between the adjacent pixels according to a density gradient of adjacent pixels in the main scanning direction, and a pixel after the enlargement interpolation processing. A contour enhancement processing unit that performs a contour enhancement process on the data is provided, and the contour enhancement processing unit obtains a minimum pixel density and a maximum pixel density in a density determination region of a predetermined size centered on the pixel of interest. And the density range between the minimum pixel density and the maximum pixel density is divided into three ranges, a low density range, an intermediate density range, and a high density range according to the set enlargement magnification, Is within the low density range, the target pixel density is converted to the minimum pixel density, and when the difference between the target pixel density and the minimum pixel density is within the high density range, the target pixel density is changed. Maximum image above When the difference between the target pixel density and the minimum pixel density is within the intermediate range, the target pixel density and the minimum pixel density are converted within the density range between the minimum pixel density and the maximum pixel density. An enlarged image data generation device in a digital copying machine, comprising: a second means for converting the density of a pixel of interest into a density according to the difference between 2. The second means, wherein the target pixel density is S, the minimum pixel density is L _th , the maximum pixel density is H _th, and the set enlargement magnification is α, and the first index k is (2α -1) · {(S-L th) / (H th -L th)} -
Means for calculating based on the equation (α-1), the second index K based on the calculated first index k, k ≦ 0
If K = 0, if k ≧ 1, K = 1 if K ≧ 1, and if K <k if 0 <k <1, means for obtaining based on the rule and the obtained second index K are used to obtain the pixel of interest. The enlarged image data generating device in a digital copying machine according to claim 1, further comprising: a unit for converting the density S based on the formula (H _th −L _th ) K + L _th . 3. Enlargement interpolation processing means for interpolating a number of pixel data corresponding to a set enlargement magnification between the adjacent pixels according to a density gradient of adjacent pixels in the main scanning direction, and pixels after the enlargement interpolation processing A contour enhancement processing unit that performs a contour enhancement process on the data is provided, and the contour enhancement processing unit sets a density range between a preset minimum pixel density and a preset maximum pixel density as a set magnification factor. Accordingly, when the difference between the target pixel density and the minimum pixel density is within the low density range, the target pixel density is set to the minimum pixel density. If the difference between the target pixel density and the minimum pixel density is within the high density range after conversion, the target pixel density is converted to the maximum pixel density, and the difference between the target pixel density and the minimum pixel density is in the intermediate range. If within, then Enlarged image data generation apparatus in a digital copying machine which converts the pixel of interest density to the density corresponding to the difference between the target pixel density and the minimum pixel density within the density range between the small pixel density and the maximum pixel density. 4. The contour emphasis processing means sets the first index k to S, the target pixel density is S, the minimum pixel density is L _th , the maximum pixel density is H _th, and the set enlargement magnification is α. 2α-1) · {(S-L _th ) / (H _th- L _th )}-
Means for calculating based on the equation (α-1), the second index K based on the calculated first index k, k ≦ 0
If K = 0, if k ≧ 1, K = 1 if K ≧ 1, and if K <k if 0 <k <1, means for obtaining based on the rule and the obtained second index K are used to obtain the pixel of interest. 4. The enlarged image data generating device in a digital copying machine according to claim 3, further comprising: a means for converting the density S based on the formula of (H _th −L _th ) K + L _th .