JPH07334672A - Picture processor - Google Patents

Abstract

PURPOSE:To easily adjust the line width with a high precision without requiring the change of hardware like the change of a beam diameter. CONSTITUTION:An address generation part no performs pattern matching based on various pattern conditions with respect to the dot pattern around a noticed picture element out or picture data or a reference area stored in a shift register 5. When the dot pattern meets a pattern condition having a step part at this time, smoothing processing is performed; and when it meets a pattern condition of a line, line width adjustment processing is performed. Thus, the line width is easily adjusted with a high precision without requiring the change of hardware like the change of the beam diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device for adjusting the line width of an image when outputting binary image data by an electrophotographic output device.

[0002]

2. Description of the Related Art In an image output terminal (IOT) of a copying machine, a fax machine, a laser printer or the like, a CAD is used to attach toner to a portion of the drum where electric charges are stored.
(Charge area development) method, or DAD that attaches toner to the non-charged area on the drum
Some are equipped with a (Discharge Area Development) type development system. In such an apparatus, the reproducibility of the line width varies considerably depending on the device and the developing method, and the line width becomes thick or thin. For example, in the CAD method, the line width tends to be thin, and thus the thin line may disappear. On the other hand, in the DAD method, the line width tends to be thick, so that fine characters may be crushed. Therefore, conventionally, in order to adjust the line width, the beam diameter of the laser light source, the development parameter, and the like have been changed.
However, the degree of freedom is low and hardware adjustment is necessary, so that it is not easy for the user to do.

In recent years, printers with various resolutions from 240 dpi to 600 dpi have been provided. If the resolution changes, the optimum beam diameter also changes, so common IO
Even when using the T engine, you can adjust the beam diameter,
The raster output scanner (ROS) part is replaced, or an intermediate parameter that can obtain a certain output at either resolution is used. However, in the former two cases, there is a problem that the cost is increased, and in the latter case, there is a problem that the image quality is deteriorated because it is an intermediate parameter.

Further, when a plurality of printers are connected on the network, it is desirable that the outputs of the printers match the appearance. However, since the IOT characteristics of each printer connected to the network are different, a mechanism for absorbing the difference in the IOT characteristics and matching the outputs of the printers is required.

Therefore, conventionally, the following apparatus has been used as an image processing apparatus for adjusting the line width of an output image.
For example, Japanese Patent Application Laid-Open No. 62-279368 discloses a device that changes the pulse width, which is the lighting time of laser light, to change the line width by making the rise of the laser lighting signal dull.

In Japanese Patent Laid-Open No. 1-269963, the line width of an output image is adjusted by changing the development bias applied to the development sleep and the development parameters such as the peripheral speed ratio of the development sleep. It is disclosed.

[0007]

The conventional image processing apparatus described above has the following problems. First, the apparatus disclosed in Japanese Patent Laid-Open No. 62-279368 has a problem that only the pulse width in the main scanning direction can be adjusted, so that only the line width of vertical lines can be adjusted and the line width of horizontal lines cannot be adjusted. Further, in the device disclosed in JP-A-1-269963,
Since other output characteristics such as the solid (black solid) density change along with the line width, there is a problem that it is difficult to balance and there is little freedom in adjustment.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image processing apparatus capable of easily and accurately adjusting a line width without requiring a hardware change such as a change in beam diameter. Has an aim.

[0009]

In order to solve the above-mentioned problems, in the invention according to claim 1, it is determined whether or not the image data satisfies a pattern condition which defines the state of a predetermined pixel array. Pattern condition determination means, storage means for storing the content of the line width adjustment processing corresponding to the pattern condition; and when the pattern condition is satisfied, the image data is stored in the image data based on the content stored in the storage means. And a line width adjusting means for performing a line width adjusting process.

According to the second aspect of the invention, the image data is
Pattern condition determination for determining which of a first pattern condition defining a predetermined pixel array state and a second pattern condition defining a pixel array state different from the first pattern condition is satisfied Means, a storage means for storing the content of the line width adjustment processing corresponding to the first pattern condition and the content of the smoothing processing corresponding to the second pattern condition, and the first pattern condition being satisfied. In the case, the line width adjusting means for performing the line width adjusting process on the image data based on the content of the line width adjusting process stored in the storing means, and the second pattern condition are satisfied, the storing And a smoothing unit for performing a smoothing process on the image data based on the contents of the smoothing process stored in the unit.

[0011]

According to the first aspect of the invention, first, the pattern condition determining means determines whether or not the image data satisfies the pattern condition that defines the state of a predetermined pixel array. Then, when the pattern condition is satisfied, the line width adjusting means, based on the contents stored in the storing means,
The line width adjustment process is performed on the image data.

According to the second aspect of the present invention, first, the pattern condition determining means determines whether the image data has a first pattern condition that defines the state of a predetermined pixel array and a pixel array that is different from the first pattern condition. It is determined which one of the second pattern conditions defining the state is satisfied. And
When the first pattern condition is satisfied, the line width adjusting unit performs the line width adjusting process on the image data based on the content of the line width adjusting process stored in the storage unit. On the other hand, when the second pattern condition is satisfied, the smoothing unit performs the smoothing process on the image data based on the content of the smoothing process stored in the storage unit.

[0013]

【Example】

A. Principle of Embodiment In this embodiment, a smoothing process for reducing jaggies caused by diagonal lines is performed in addition to the line width adjusting process for thickening or thinning the line width.
The principles of the smoothing process and the line width adjusting process will be described below. A-1. Smoothing Process First, the contents of the smoothing process will be described with reference to FIG. FIG. 7A shows image data before the smoothing process is performed, and each grid of the grid is a unit of one pixel. Hereinafter, the position of each pixel is the coordinate (a,
b), c, ...) And the coordinates (1, 2, 3, ...) In the sub-scanning direction.
・), For example, "b3". Pixels in which the character "black" is written are all black pixels, and pixels in which nothing is written are all white pixels. Figure 2
In (a), all pixels are all black or all white.

Next, FIG. 2B shows the image data after smoothing the pixels of FIG. 2A. In this figure, some black pixels (hereinafter referred to as intermediate pixels) are
The black part is displayed by hatching. The same figure (a),
When (b) is compared, for example, all black pixels at coordinates c4 to c7 and all white pixels at coordinates c8 to c11 in FIG.
Is converted into an intermediate pixel. The area of the black portion of these intermediate pixels becomes smaller as it goes downward in the sub-scanning direction. In addition, the pixels of the other edge portions are similarly converted.

In the smoothing process, first, a pixel to be processed (hereinafter referred to as a pixel of interest) is centered in the image data, and "1" is set in the main scanning direction.
An area of 7 "pixels and" 9 "pixels in the sub-scanning direction (hereinafter referred to as a reference area) is extracted. Then, it is determined which of a plurality of pattern conditions the dot pattern of this reference region matches, and when they match, the area of the black portion is set to a value corresponding to the pattern condition.

An example of the pattern condition used for the smoothing process is shown in FIG. 3 (a). This condition is that the coordinate “a5” in the reference region is compared with the coordinate “a5” of the pixel of interest.
5 to i5, i4, j4 ”are white pixels and have coordinates“ a6
? I6, j5 "is a black pixel. Under this condition, the black area ratio L of the target pixel is "46.0.
%, And the result of outputting the target pixel at the coordinate “i5” is as shown in FIG. The same processing is performed on the other pixels in the reference area when each pixel becomes the target pixel. Figure 4
(a) to (f) show examples of various pattern conditions and the corresponding black area ratio L. In addition, in these figures, all the omitted parts are "pixels (-) unrelated to processing".

The image data of FIG. 2 (b) is obtained by repeating such pattern matching for each pixel of the image data of FIG. 2 (a). By the way, the reference area may satisfy a plurality of pattern conditions. For example, if the reference area satisfies the pattern condition of FIG. 3A, the conditions of FIGS. 4D to 4F should be satisfied. In such a case, in the present embodiment, it is considered that only "the longest pattern condition of the effective portion (the portion excluding the pixels not related to the processing)" is satisfied. For example, the length of the effective part of the pattern condition of FIG.
0 ", and those of FIGS. 4D to 4F are" 9 ",
They are "3" and "4". Therefore, as long as the condition of FIG. 3A is satisfied, the black area ratio L of the target pixel is “46.
0% "is set.

By the way, the contents of image data obtained by a copying machine and the like are various, but there is a possibility that each part of the image data may satisfy short pattern conditions (FIGS. 4E, 4F, etc.). This is high, and thus smoothing processing can be performed to some extent even on complicated image data. Further, when the long pattern condition of the effective portion is simultaneously satisfied as shown in FIG. 3D or FIG. 3A, smoothing processing is performed based on the long pattern condition. A more suitable smoothing process is performed. As described above, in this embodiment, various pattern conditions for the effective portion are set, and the long pattern condition is prioritized and applied, which is effective for image data obtained by a copying machine or the like. It becomes possible to perform smoothing processing.

A-2. Limitation of smoothing process As described above, when the smoothing process is unconditionally performed on the image portion of the image data, the gradation characteristics of the halftone image subjected to the pseudo halftone process are destroyed, which causes a problem that the image quality is deteriorated. Therefore, it is necessary to limit the smoothing process. In the present embodiment, the number of times the pixel color in the reference area changes along the main scanning direction and the sub scanning direction is counted. The count result is a predetermined value (for example, "9
0 ") or more, the reference area is considered to be an image portion.

The smoothing process is partially limited for the reference area that is considered to be the image portion. That is, when the long pattern condition of the effective portion is satisfied as shown in FIGS. 4A to 4D, the target pixel is subjected to the smoothing process, but as shown in FIGS. 4E and 4F, it is short. When only the pattern condition (for example, the pattern condition in which the length of the effective portion is “4” or less) is satisfied, the smoothing process is not performed. Since the image portion is formed by repeating a short pattern, this makes it possible to avoid the smoothing process.

On the other hand, when a character or a line drawing is superimposed on the image portion, each pixel forming the character or the like is likely to satisfy a long pattern condition. When the long pattern condition is satisfied, the smoothing process is performed on the pixel. Here is the feature of the present embodiment, and when characters or line drawings are superimposed on the photographic image, or when the characters are modified by shading, the gradation characteristics of the photographic image or the shaded part are not destroyed. It is possible to apply smoothing processing to characters and line drawings.

A-3. Line Width Adjustment Process Next, the contents of the line width adjustment process will be described with reference to FIG.
FIG. 10A shows the image data before the line width adjustment processing is performed, and like the smoothing processing, first, in the main scanning direction, “17 A reference region of “9” pixels in the sub-scanning direction is extracted.

Then, it is determined whether or not the dot pattern of the reference area matches the straight line pattern condition having no step portion. When the straight line pattern conditions are met,
For example, when thickening the line width, the pixel of interest (white pixel;
The black area ratio L indicated by a circle is set to a predetermined value (for example, 50%). On the other hand, when reducing the line width, the same figure (c)
As shown in, the black area ratio L of the target pixel (black pixel; ◯ mark) is set to a predetermined value (for example, 50%). In other words, when the line width is made thicker and when the line width is made thinner, the straight line pattern conditions are different, and when the target pixel at the center is a white pixel, the line width is thickened, and the target pixel is a black pixel. In some cases, it is the case of thinning. Further, in the case of narrowing the line width, when the target line width is a 1-dot line, the black area ratio L of the target pixel is set to a predetermined value from the center of the target pixel as shown in FIG. Value of (eg 50
%) So that it is black only. Since one dot line requires special processing, it needs to be detected separately. The edge pixels are turned on from the edge direction, and the one dot line is turned on from the center. For other pixels in the reference area,
Similar processing is performed when each pixel becomes a target pixel. Further, since the pattern condition includes both vertical lines and horizontal lines, line width adjustment processing is also performed on horizontal lines (not shown).

In the actual process, the smoothing process is preferentially performed first on the dot pattern of the reference area, and then the line width adjusting process is performed. In other words, first, FIGS. 4A to 4D
It is compared with the pattern conditions etc. shown in Fig. 1 to determine whether or not they match, and if none of the pattern conditions are met, it is compared with the straight line pattern condition having no step and whether or not they match. Is determined. When performing the smoothing process, the line width adjustment process may be performed on the line to be the smoothing process by changing the ratio of the intermediate pixels shown in FIG. 2 according to the line width adjustment process. . In this case, the value of the smoothing output is the value obtained by subtracting the thinning amount from the original black area ratio L when thinning. When thickening, on the contrary, a value added to the original black area ratio L is added. As a result, if the pixel extends beyond the pixel, the pixel next to the pixel is corrected. Therefore, when adjusting the line width up to ± 50%, it is necessary to detect all edge black and white pixels.

Next, an embodiment of the present invention will be described with reference to the drawings. B. Configuration of Embodiment The configuration of this embodiment will be described below with reference to FIG. In the figure, reference numeral 1 is an image input unit, which reads an original by an image scanner or the like and outputs image data. Reference numeral 2 denotes a binary image conversion unit that converts this image data into binary image data. In this binary image data, black pixels are represented as "1" and white pixels are represented as "0". An image memory 3 stores the converted binary image data. Four
Is an address generator, which stores the binary image data in the image memory 3 by "1" pixels in the main scanning direction and "9" in the sub scanning direction.
An address signal for sequentially accessing in the main scanning direction is output with the pixel region as one unit. Thereby, the binary image data is sequentially read from the image memory 3.

A shift register 5 stores binary image data of "17" pixels in the main scanning direction and "9" pixels in the sub scanning direction. Upon receiving one unit of binary image data from the image memory 3, the shift register 5 stores the contents in "9" registers located at one end in the main scanning direction and the contents of other registers in the main scanning. Shift in the direction. The overflowed data is discarded. As a result, the binary image data of the reference area is stored in the shift register 5. The pixel at the center of the reference area, that is, the value of the target pixel is output as target pixel data CPX.

Next, 6 is an EOR (exclusive OR) circuit group, which calculates and outputs an exclusive OR between pixel data adjacent to each other in the main scanning direction and the sub scanning direction within the reference area. It is composed of many EOR circuits. 7
Is an adder, which adds the output signals of the respective EOR circuits and outputs the result. As an example, the addition result is obtained when only the pixel of interest is black (“1”) and all other pixels are white (“0”) in the reference area. First, the target pixel is adjacent to two pixels in each of the main scanning direction and the sub scanning direction. The four EOR circuits having these pixel data and the pixel data of the target pixel as input signals output "1" signals, but other EOR circuits.
The circuits all output a "0" signal. Therefore, in such a case, the addition result of the adder 7 becomes "4".

Reference numeral 8 denotes a comparator, which compares the addition result of the adder 7 with a threshold value (for example, "90") stored in the register 9, and if the addition result is equal to or more than the threshold value, becomes "1",
In other cases, the comparison signal PSL that becomes "0" is output. A look-up table 13 stores image data of all black pixels, all white pixels, and various intermediate pixels, and outputs corresponding image data when an address signal is supplied. That is, the image data output from the look-up table 13 specifies white / black in subpixel units (units smaller than one pixel). An image output unit 14 prints out an image based on the image data supplied from the lookup table 13.

An address generator 10 compares the dot pattern of the reference area stored in the shift register 5 with various pattern conditions (see FIG. 4) and matches with a high probability a pattern condition (hereinafter referred to as a definite pattern). The address signal ADL is output based on the condition). As described above, the priority (matching order) of the pattern conditions is the long pattern condition, the short pattern condition, and the straight line pattern condition. The address signal ADL designates the read address of the look-up table 13. If the address signal ADL is directly supplied to the look-up table 13, the image data having the black area ratio L corresponding to the fixed pattern condition is generated. It will be output from the lookup table 13.

The address generator 10 also outputs a long pattern match signal LMT and a short pattern match signal SMT based on the length of the effective portion of the fixed pattern condition. The long pattern match signal LMT is a signal which becomes "1" when the length of the effective portion is "5" or more or when it matches the straight line pattern condition, and otherwise becomes "0". Further, the short pattern match signal SMT is a signal that becomes "1" when the length of the effective portion is "4" or less, and becomes "0" otherwise.

If the dot pattern in the reference area does not satisfy any of the pattern conditions, the address signal AD
L is not output, and the short pattern match signal SMT and the long pattern match signal LMT become "0". Next, 12
Is a selector, which receives the signals PSL, SMT, LMT, and CPX at the selection input terminals SEL1 to SEL4,
Based on the result, any one of the address signals supplied to the data input terminals A to C is selected and output from the output terminal OUT. Here, the address of the all-black pattern of the lookup table 13 is supplied from the register 11 to the data input terminal A. Further, the data input terminal B is similarly supplied with the address of the all-white pattern. The selection conditions in the selector 12 are as shown in Table 1 below.

[0032]

[Table 1]

C. Operation of Embodiment Next, the operation of this embodiment will be described. First, the image input unit 1
When the image data is input from, the image data is converted into binary image data via the binary image conversion unit 2 and stored in the image memory 3. Next, when the address generator 4 sequentially reads out binary image data of one unit (a region of “1” pixels in the main scanning direction and “9” pixels in the sub scanning direction) in the image memory 3, the binary image data is read out. The contents are stored in the shift register 5 while being shifted. Further, in the line width adjustment processing, whether the line width is thickened or thinned is set by the line width designation signal S1. Subsequent operations differ depending on the contents of the reference area stored in the shift register 5, and therefore will be described separately.

C-1. When neither pattern condition is satisfied When the dot pattern in the reference area does not satisfy any pattern condition, both the short pattern match signal SMT and the long pattern match signal LMT become “0”. here,
If the pixel of interest is a black pixel, the pixel of interest data CPX becomes "1". In this case, according to Table 1 (a), the data input terminal A is selected by the selector 12, and the address of the all black pattern is supplied to the lookup table 13.
On the other hand, if the target pixel is a white pixel, the target pixel data CP
X becomes "0". In this case, according to Table 1 (b), the data input terminal B is selected and the address of the all-white pattern is supplied to the lookup table 13. As a result, the image data supplied to the image output unit 14 is the target pixel data C.
All black pattern or all white pattern according to PX,
An image that has not been subjected to smoothing processing or line width adjustment processing is output.

C-2. When Long Pattern Condition is Satisfied When the defined pattern condition in which the length of the effective portion is “5” or more is satisfied, the long pattern match signal LMT is set to “1”. According to Table 1 (e), in such a case, the data input terminal C is selected regardless of the values of other signals. As a result, the address signal ADL is supplied to the look-up table 13 via the selector 12, and the look-up table 13 outputs the image data relating to the intermediate pixel. That is, the image data subjected to the smoothing process is output from the image output unit 14.

C-3. When the short pattern condition is satisfied When the fixed pattern condition in which the length of the effective portion is “4” or less is satisfied, the short pattern match signal SMT is set to “1”. Here, if the number of white / black changes in the reference area is greater than or equal to the threshold value, the comparison signal PSL becomes “1”. In such a case, according to Tables 1 (c) and 1 (d), one of the data input terminals A and B is selected according to the target pixel data CPX. That is, as in the case where the dot pattern of the reference region does not satisfy any of the pattern conditions, the image output unit 14 outputs an image that has not been subjected to smoothing processing.

On the other hand, if the number of white / black changes in the reference area is less than the threshold value, the comparison signal PSL becomes "0". In such a case, according to Table 1 (f), the data input terminal C is selected by the selector 12. That is, as in the case where the long pattern condition is satisfied, the image data subjected to the smoothing process is output from the image output unit 14.

C-4. When the straight line pattern condition is satisfied When the straight line definite pattern condition is satisfied, according to Table 1 (e), in such a case, the data input terminal C is selected regardless of the values of other signals. As a result, the address signal ADL
Is supplied to the look-up table 13 via the selector 12, and the look-up table 13 outputs the image data of the intermediate pixel. That is, the image data subjected to the line width adjustment processing is output from the image output unit 14.

Which of the operations described above is executed is determined based on the contents of the reference area in the shift register 5. That is, each time new binary image data is read from the image memory 3 and the contents of the shift register 5 are updated, the selection state of the selector 12 is changed accordingly. Therefore, when the image data is stored in the image memory 3 and the character or line drawing overlaps with the image data, the short pattern match signal SMT or the long pattern match signal is kept while the comparison signal PSL is fixed at "1". The value of LMT will fluctuate.

That is, when the pixel of interest is located in the background portion of the image, the short pattern match signal SMT is "1".
Then, while the image data that has not been subjected to the smoothing process is output, when the pixel of interest is located on a character or line drawing on the image, the long pattern match signal LMT becomes “1”, and Smoothing processing is performed.

As described above, according to this embodiment, the edge of the image data (black and white change point) is obtained by the pattern matching.
To increase the line width, the target pixel (white pixel) is made black by a predetermined amount from the black pixel side, and when the line width is reduced, the black area of the target pixel (black pixel) is detected. Is reduced by a predetermined amount. At this time, since the size of the black area is determined by changing the pulse width of the PWM (pulse width modulation) lighting signal applied to the laser light source, it is possible to easily and easily without changing hardware such as changing the beam diameter. It is possible to adjust the line width with high accuracy.

Further, according to the present embodiment, the comparison signal PSL
Is fixed to "1", the selection state of the selector 12 is changed according to the states of the short pattern match signal SMT and the long pattern match signal LMT, so that smoothing processing for the background portion of the image is avoided. It is possible to perform smoothing processing on characters and line drawings superimposed on the image. In the above embodiment,
The image image condition is determined based on whether the number of times the pixel color in the reference area changes is equal to or greater than a predetermined value,
The image image conditions are not limited to those of the embodiment, and various known ones may be used.

[0043]

As described above, according to the invention described in claim 1, there is an advantage that the line width can be adjusted easily and with high accuracy without requiring a hardware change such as a change of the beam diameter. can get. According to the invention of claim 2,
There is an advantage that the line width can be adjusted easily and with high accuracy without requiring a hardware change such as the change of the beam diameter, and the jaggies occurring at the edge of the line can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the embodiment.

FIG. 3 is a diagram illustrating the operation of the embodiment.

FIG. 4 is a diagram illustrating the operation of the embodiment.

FIG. 5 is an operation explanatory diagram of the embodiment.

[Explanation of symbols]

10 address generation unit (pattern condition determination means, line width adjustment means, smoothing means) 13 lookup table (storage means) 8 comparator 7 adder 6 EOR circuit group 12 selector (line width adjustment means, smoothing means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H04N 1/40 0834-5H G06F 15/62 320 K H04N 1/40 101 Z

Claims (2)

[Claims] 1. A pattern condition judging means for judging whether or not the image data satisfies a pattern condition that defines a state of a predetermined pixel array, and a memory for storing the contents of the line width adjustment processing corresponding to the pattern condition. And a line width adjusting unit that performs a line width adjusting process on the image data based on the contents stored in the storage unit when the pattern condition is satisfied. . 2. The image data satisfies either of a first pattern condition that defines a state of a predetermined pixel array and a second pattern condition that defines a state of a pixel array different from the first pattern condition. Pattern condition determining means for determining whether or not there is a line width adjustment process corresponding to the first pattern condition, and storage means for storing the smoothing process content corresponding to the second pattern condition, When the first pattern condition is satisfied, a line width adjusting unit that performs a line width adjusting process on the image data based on the content of the line width adjusting process stored in the storage unit, the second pattern condition If the above condition is satisfied, the image processing means is provided with a smoothing means for performing the smoothing processing on the image data based on the contents of the smoothing processing stored in the storage means. Processing equipment.