JP2001203883A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the conversion processing of resolution and to improve the image quality of an output image. SOLUTION: This image processor performs the conversion of resolution to the input image data and produces the output image data. A storage part of the image processor stores an input pattern, and an output pixel pattern that is previously decided, in response to the input pixel pattern and according to the resolution conversion rate. A matching part secures the matching between an input reference pattern, i.e., a pixel pattern of a reference area and the input pixel pattern that is previously decided by defining each pixel of a pixel pattern of the input image data as an attentional pixel and referring to the reference area that is previously decided to the attentional pixel. Then a resolution processing part performs conversion of resolution, by using the output pixel pattern corresponding to the input pixel pattern that is fit to the input reference pattern via the pattern matching as the output image data on the attentional pixel, corresponding to the input reference pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an image processing apparatus that performs image processing in a digital printer, a digital facsimile, and the like.

[0002]

2. Description of the Related Art Conventionally, binary (1 bit) image data is formed from a document read by a digital copying machine or the like, and the formed image data is subjected to resolution conversion as necessary to output an image. An image processing apparatus to be formed has been developed. Such an image processing apparatus, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-329483, outputs a smooth image by reducing jaggies at a step portion in a density-converted output image. There is.

[0003] The image processing apparatus disclosed in the above publication detects the type of a step in image data and the length of the step by pattern matching when performing resolution conversion on binary image data. . The image processing apparatus is configured to form an output image by interpolating image data with interpolation data set in advance corresponding to the type and length of the detected step.

[0004]

However, in the resolution conversion by the conventional pattern matching, even when the resolution in the main scanning direction is different from that in the sub-scanning direction, the resolution conversion rate is different between the main scanning direction and the sub-scanning direction. It was the same. Therefore, the resolution after resolution conversion remains different between the main scanning direction and the sub-scanning direction.
Further, the interpolation process needs to be performed only in one scanning direction. That is, in this case, a two-step process is performed.

The image processing apparatus disclosed in the above publication has means for detecting the type of a step in image data by pattern matching, and means for detecting the length of the detected step. Then, a step is interpolated based on these detection results. Also in this image processing apparatus, the resolution conversion rates in the main scanning direction and the sub scanning direction are the same. Therefore, when the resolution in the main scanning direction is different from the resolution in the sub-scanning direction, the resolution after resolution conversion is still different between the main scanning direction and the sub-scanning direction.
In order to obtain a desired resolution, it is necessary to perform an interpolation process only in one scanning direction.

As described above, the conventional image processing apparatus has a problem that the resolution conversion is a two-step process, and the resolution conversion process is complicated.

[0007] In view of the above problems, the present invention provides:
An object of the present invention is to simplify a resolution conversion process when converting a resolution by pattern matching. Also,
An object of the present invention is to improve the image quality of an output image by performing a process more suitable for image data in the resolution conversion process.

[0008]

According to the present invention, there is provided an image processing apparatus for performing resolution conversion on input image data to form output image data. A storage unit that stores a predetermined pixel pattern, and each pixel in the pixel pattern of the input image data is set as a target pixel, and a reference region that is a region on the pixel pattern of the input image data including the target pixel is referred to. Performing pattern matching between an input reference pattern that is a pixel pattern in the reference area and an input pixel pattern that is a pixel pattern that can appear in the reference area and that is stored in the storage unit, and that matches the input reference pattern. A matching unit for specifying an input pixel pattern;
Resolution conversion is performed by using output pixel patterns stored in the storage unit corresponding to the specified input pixel patterns in accordance with the conversion rate of resolution conversion as output image data of the target pixel corresponding to the reference area. And a resolution conversion unit that performs the following.

In the above configuration, the storage unit stores the input pixel pattern and the output pixel pattern determined in advance corresponding to the input pixel pattern in accordance with the conversion ratio of the resolution conversion.

Then, using this input pixel pattern,
Pattern matching is performed in the matching unit.
In this pattern matching, each pixel in the pixel pattern of the input image data is set as a target pixel, a reference region predetermined for the target pixel is referred to, and an input reference pattern which is a pixel pattern in the reference region and This is performed by determining the matching with the input pixel pattern.

The resolution conversion unit sets an output pixel pattern corresponding to an input pixel pattern matching the input reference pattern as output image data of a target pixel corresponding to the input reference pattern, based on a result of the pattern matching. I do. Thereby, a desired resolution conversion is performed.

In this configuration, the output pixel pattern corresponds to the input pixel pattern and is set according to the conversion rate of the resolution conversion. Therefore, the resolution of the input image data is converted to the desired resolution of the output image data by a one-step process, that is, a process of setting the output pixel pattern corresponding to the input pixel pattern that matches the input reference pattern as the output image data of the target pixel. can do. That is, resolution conversion can be realized by simpler processing.

Further, since the output pixel pattern can be more appropriately interpolated in accordance with the output resolution and set to a more suitable pixel pattern, the image quality of the output image can be improved.

In the image processing apparatus according to the present invention, in the above image processing apparatus, the output pixel pattern may further include a main image data for the input image data having different resolutions in a main scanning direction and a sub scanning direction. It is preferable that the resolution in the scanning direction and the resolution in the sub-scanning direction are set so as to form the same output image data.

[0015] In the above configuration, the output pixel pattern determines the target pixel of the input image data whose resolution in the main scanning direction and the resolution in the sub-scanning direction are different from each other. It is set so that resolution conversion is performed to equal output image data.

Thus, input image data having different resolutions in the main scanning direction and the sub-scanning direction can be converted into output image data having the same resolution in the main scanning direction and the sub-scanning direction by one-step processing. it can.

In the image processing apparatus according to the present invention, in the above image processing apparatus, the output pixel pattern may further include a main image data having a resolution in the main scanning direction and a resolution in the sub scanning direction equal to each other. It is preferable that the resolution in the scanning direction and the resolution in the sub-scanning direction are set so as to form the output image data different from each other.

In the above-described configuration, the output pixel pattern determines the pixel of interest of the input image data having the same resolution in the main scanning direction and the resolution in the sub-scanning direction, and the resolution in the main scanning direction and the resolution in the sub-scanning direction. It is set so that the resolution is converted to different output image data.

Thus, input image data having the same resolution in the main scanning direction and the sub-scanning direction can be converted into output image data having different resolutions in the main scanning direction and the sub-scanning direction by one-step processing. it can.

According to another aspect of the present invention, there is provided an image processing apparatus for performing resolution conversion on input image data to form output image data.
A storage unit that stores a predetermined pixel pattern, and each pixel in the pixel pattern of the input image data is set as a target pixel, and a reference region that is a region on the pixel pattern of the input image data including the target pixel is referred to. Performing pattern matching between an input reference pattern that is a pixel pattern in the reference area and an input pixel pattern that is a pixel pattern that can appear in the reference area and that is stored in the storage unit, and that matches the input reference pattern. A matching unit that specifies an input pixel pattern, and is stored in the storage unit corresponding to the specified input pixel pattern, and forms an output pixel pattern based on a common basic pattern for a conversion rate of resolution conversion. The formed output pixel pattern is used as output image data of the pixel of interest corresponding to the reference area. It is characterized in that it comprises a resolution conversion unit which performs resolution conversion by.

In the above configuration, the input pixel pattern and a predetermined basic pattern corresponding to the input pixel pattern (corresponding to one to one) regardless of the conversion ratio of the resolution conversion are stored in the storage unit. ing.

Then, pattern matching is performed by a matching unit using the input pixel pattern.
In this pattern matching, each pixel in the pixel pattern of the input image data is set as a target pixel, a reference region predetermined for the target pixel is referred to, and an input reference pattern which is a pixel pattern in the reference region and This is performed by determining the matching with the input pixel pattern.

The resolution conversion unit forms an output pixel pattern based on the basic pattern corresponding to the input pixel pattern that matches the input reference pattern based on the result of the pattern matching, and the output pixel pattern corresponds to the input reference pattern. Is set as output image data of the pixel of interest. Thereby, a desired resolution conversion is performed.

In this configuration, different from setting an output pixel pattern for each resolution conversion rate, a common combination of an input pixel pattern and a basic pattern is set for each resolution conversion rate, and this basic pattern is converted. Thus, an output pixel pattern can be formed. Therefore, since it is not necessary to form an output pixel pattern according to each resolution conversion rate, the memory capacity can be reduced.

An image processing apparatus according to the present invention is an image processing apparatus for forming an output pixel pattern based on the basic pattern described above, further comprising: a resolution conversion unit that determines a predetermined rule according to a conversion rate of the resolution conversion. It is preferable that the output pixel pattern is formed by converting the basic pattern according to the following.

In the above arrangement, the basic pattern is converted in accordance with a predetermined rule to form an output pixel pattern. That is, an output pixel pattern can be formed by performing a certain process on the basic pattern. Therefore, it is possible to simplify the processing while reducing the memory capacity described above.

An image processing apparatus according to the present invention is an image processing apparatus for forming an output pixel pattern based on the above-mentioned basic pattern, further comprising: in said resolution conversion section, said basic pattern being a predetermined one of said basic patterns. When the output pattern matches the basic pattern, the pixel pattern stored in the storage unit corresponding to the basic pattern is preferably set as the output pixel pattern.

In the above configuration, when the basic pattern is a predetermined basic pattern (specific basic pattern) such as a pixel pattern having no step, a predetermined basic pattern is specified for the specific basic pattern. Let the pixel pattern be the output pixel pattern. This makes it possible to set only a basic pattern for which it is preferable to set an individual output pixel pattern from the viewpoint of image quality of an output image as a specific basic pattern, and to set an appropriate pixel pattern for each specific basic pattern as an output pixel pattern. Can be. As a result, it is possible to improve the image quality of the output image while minimizing the increase in the memory capacity.

In order to solve the above-mentioned problems, an image processing apparatus of the present invention performs resolution conversion on input image data to form output image data.
A storage unit that stores a predetermined pixel pattern, and each pixel in the pixel pattern of the input image data is set as a target pixel, and a reference region that is a region on the pixel pattern of the input image data including the target pixel is referred to. A first pattern matching between an input reference pattern that is a pixel pattern in the reference area and an input pixel pattern that is a predetermined pixel pattern among the pixel patterns that can appear in the reference area and is stored in the storage unit; Performing the input reference pattern, if the input reference pattern matches the input pixel pattern, expands the reference region, an extended input reference pattern that is a pixel pattern in the expanded reference region, and a pixel pattern that can appear in the extended reference region And performs a second pattern matching with the extended input pixel pattern stored in the storage unit. A matching unit, is characterized in that it comprises a resolution conversion unit for performing resolution conversion on the basis of the result of the second pattern matching.

Further, the image processing apparatus of the present invention is an image processing apparatus for performing resolution conversion based on the result of the second pattern matching described above, and the resolution conversion unit further comprises: When the extended input reference pattern matches a predetermined extended input pixel pattern among the extended input pixel patterns, an output pixel pattern stored in the storage unit corresponding to the extended input pixel pattern, Preferably, resolution conversion is performed by using output image data of the pixel of interest corresponding to the reference region.

In the above configuration, the matching section first refers to a predetermined reference area for the target pixel. Then, first pattern matching is performed between an input reference pattern, which is a pixel pattern in the reference area, and a predetermined input pixel pattern (specific pattern), and when the input reference pattern matches the specific pattern, the reference is performed. Expand the area. Then, the second pattern matching is performed on the extended reference area. The resolution conversion is performed by the resolution conversion unit based on the result of the second pattern matching. When the input reference pattern and the specific pattern do not match, the same processing as that of each of the above-described image processing apparatuses can be performed without expanding the reference area.

In this configuration, by performing the first pattern matching on the input reference pattern with the specific pattern in advance, the expanded reference area is used as a reference area for referencing the surrounding pixel patterns at the time of resolution conversion. It can be determined whether or not it should be used.

That is, for example, a pixel pattern having no step is set as a specific pattern, and if the input reference pattern matches this pixel pattern, the second pattern matching is performed using the expanded reference area. Is performed based on the resolution. Thus, in the second pattern matching, the presence or absence of a step in a wider area can be detected, and the resolution conversion can be performed in consideration of this. Therefore, the image quality of the output image can be further improved.

An image processing apparatus according to the present invention is an image processing apparatus for performing resolution conversion based on the result of the above-mentioned second pattern matching. It is preferable to extend the image data in the main scanning direction or the sub-scanning direction.

In the above configuration, for example, when there is no step in the main scanning direction or the sub-scanning direction in the input reference pattern, the reference area is expanded in the main scanning direction or the sub-scanning direction to check for the presence or absence of the step. be able to.
That is, it is possible to confirm the presence or absence of a step in the extended reference area extended only when a step in the main scanning direction or the sub-scanning direction cannot be detected in the reference area. This makes it possible to set a more suitable output pixel pattern for the target pixel while suppressing the complexity of the process and the increase in the memory capacity.

An image processing apparatus according to the present invention is an image processing apparatus for performing resolution conversion based on the result of the above-mentioned second pattern matching. Preferably, the extension width of the reference area is determined according to the resolution in the direction and the resolution in the sub-scanning direction.

When the resolution in the main scanning direction and the resolution in the sub-scanning direction of the input image data are different, if the expansion width in the main scanning direction and the expansion width in the sub-scanning direction are set in the same manner,
An image range that can be referred to from a difference in resolution may be different from each other between the main scanning direction and the sub-scanning direction, that is, a rectangular image range may be referred to. At this time, since the main scanning direction and the sub-scanning direction cannot be uniformly referred to, it is not preferable to set the output pixel pattern based on the extended input reference pattern.

Therefore, in the above configuration, the expansion width for expanding the reference area is determined according to the resolution of the input image data in the main scanning direction and the resolution in the sub-scanning direction. This allows
Since the image range to be referenced can be appropriately set to, for example, a square, an extended input reference pattern with more accurate information can be obtained, and a more appropriate output pixel pattern can be set.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

First, a digital copying machine 30 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing a configuration of a digital copying machine 30 employing a reversal development method. The digital copier 30 includes a scanner unit 31, a laser printer unit 32, a multi-stage paper feeding unit 3
3, and a sorter 34 are provided. Hereinafter, each unit will be described.

The multi-stage paper feed unit 33 includes the first cassette 5
1, a second cassette 52, a third cassette 53, and a fourth cassette 55 that can be added by selection. In the multi-stage paper feed unit 33, the sheets stored in the cassettes of each stage are taken out one by one from the top, and the sheets are
It is conveyed toward the laser printer unit 32.

The scanner section 31 includes a document table 35 made of transparent glass, a double-sided automatic document feeder (hereinafter, referred to as RDF) 36, and a scanner unit 40.

The RDF 36 can set a plurality of originals at one time, and automatically sets the set originals by one.
The sheets are fed to the scanner unit 40 one by one. The RDF 36 is configured to cause the scanner unit 40 to read one side or both sides of the document according to an operator's selection.

The scanner unit 40 includes a lamp reflector assembly 41 for exposing a document, a plurality of reflection mirrors 43 for guiding a reflected light image from the document to a photoelectric conversion element (hereinafter, referred to as a CCD) 42, and a And a lens 44 for forming the reflected light image on the CCD 42.

The scanner unit 40 reads an original image while moving along the lower surface of the original table 35 in the scanner section 31. Also, R
When the DF 36 is used, the RDF is stopped in a state where the scanner unit 40 is stopped at a predetermined position below the RDF 36.
The original image conveyed by 36 is read.

The image data obtained by reading the original image by the scanner unit 40 is sent to an image processing device described later, where the image data is subjected to each processing, and then temporarily stored in a buffer memory of the image processing device. Then, in accordance with the output instruction, the image data stored in the buffer memory is given to the laser printer unit 32, whereby an image is formed on a sheet.

The laser printer section 32 includes a manual tray 4
5, a laser writing unit 46, and an electrophotographic processing unit 47 for forming an image.

The laser writing unit 46 includes a semiconductor laser (not shown) for outputting a laser beam according to the image data read from the buffer memory, and a polygon mirror (not shown) for deflecting the laser beam at a constant angular velocity. And an f-θ lens (not shown) for correcting the laser beam deflected at a constant angular velocity so as to be deflected at a constant angular velocity on the photosensitive drum 48 of the electrophotographic process unit 47.

The electrophotographic process unit 47 includes a photosensitive drum 48, and a charger, a developing device, a transfer device, a peeling device, a cleaning device, and the like disposed around the photosensitive drum 48.
A static eliminator (not shown) and a fixing device 49 are provided.

The laser writing unit 46 emits a laser beam based on the image data read from the buffer memory and scans the laser beam. Then, the surface of the photosensitive drum 48 in the electrophotographic process section 47 is irradiated with the laser beam, so that an electrostatic latent image is formed on the surface. The electrostatic latent image is visualized with toner by the above-described developing device or the like, so that a toner image is formed on the surface of the photosensitive drum 48.

This toner image is electrostatically transferred onto a sheet conveyed from the multi-stage sheet feeding unit 33 or the manual feed tray 45. Then, the toner image transferred on the paper is
The image is fixed as an image by the fixing device 49.

A transport path 50 is provided downstream of the sheet on which the image is fixed in the transport direction. This transport path 50 is
The transport path 57 leading to the sorter 34 and the multi-stage paper feed unit 3
3 and a transport path 58 leading to the third path. The sheet on which the image has been formed by this is fed from the fixing device 49 to the transport path 50/5.
7 to the sorter 34 or the transport path 50
A reversing conveyance path 50 of the multi-stage paper feeding unit 33 via
a.

Next, the above-described image processing apparatus will be described in detail with reference to FIG. FIG. 2 is a schematic block diagram illustrating a configuration of the image processing apparatus. The image processing apparatus includes an input unit 1, a bitmap memory 2, a central processing unit (hereinafter, referred to as a central processing unit).
A matching processing unit (matching unit,
A resolution conversion unit 4, a read-only memory (storage unit, hereinafter referred to as ROM) 5, a buffer memory 6, and an output unit 7. Hereinafter, the operation of each unit will be described.

The image data sent from the scanner unit 40 is input from the input unit 1 to the image processing device. Then, the input image data is stored in the bitmap memory 2.

The image data stored in the bitmap memory 2 is subjected to pattern matching with a pixel pattern previously stored in the ROM 5 by the matching processing unit 4. Then, the resolution is appropriately converted based on the result of the pattern matching, and an output pixel pattern is formed. This output pixel pattern is stored in the buffer memory 6.
The details of pattern matching in the matching processing unit 4 and formation of an output pixel pattern based on the pattern matching will be described later.

By performing such processing, the output pixel pattern stored in the buffer memory 6 is output to the above-described laser writing unit 46 (see FIG. 1) via the output unit 7 according to an output instruction. .

The above processing is controlled by the CPU 3. The method of pattern matching and resolution conversion described later is stored in the ROM 5 and executed by the CPU 3.

Next, the above-described resolution conversion will be described. In the following, input image data (data input to the image processing apparatus via the input unit 1 (see FIG. 2)) and output image data (output pixel pattern, output from the image processing apparatus to the output unit 7 (FIG. 2)) ) Is binary (1 bit) data.

The resolution conversion is basically performed according to the following procedure. First, a target pixel is set in the input image data. Further, information on a pixel arrangement (pixel pattern) of neighboring pixels (reference area) in a predetermined range including the target pixel is set as an input reference pattern.

Pattern matching is performed on this input reference pattern, that is, it is determined which of the preset pixel patterns (input pixel patterns) the input reference pattern matches. Then, predetermined processing is set in advance in accordance with the suitable input pixel pattern.

More specifically, an input pixel pattern and an output pixel pattern corresponding to the input pixel pattern are set in advance.
Then, an output pixel pattern corresponding to the input pixel pattern matched by the pattern matching is output as an output pixel pattern after resolution conversion for the target pixel.

In the following, an input reference pattern which is a pixel pattern of a reference area and a preset input pixel pattern to be subjected to pattern matching with respect to the input reference pattern are not specifically distinguished. ,
These are referred to as input reference patterns.

[Embodiment 1] First, resolution conversion is performed on input image data having different resolutions in the main scanning direction and the sub-scanning direction so that the main scanning direction and the sub-scanning direction have the same resolution. The case where the output pixel pattern is set so as to be described below.

FIGS. 3A and 3B show an example in which the resolution of input image data having different resolutions in the main scanning direction and the sub-scanning direction is converted to an output pixel pattern of the same resolution. FIG. 3A shows an input reference pattern, and FIG. 3B shows an output pixel pattern for a target pixel. Here, a pattern having a step is shown as the input reference pattern in FIG. In the following, it is assumed that the hatched portions in the figure are black pixels, and the non-hatched portions are white pixels.
It is also assumed that the pixel marked with “印” in the figure is the pixel of interest.

Here, a case is shown in which input image data having a resolution of 200 dpi in the main scanning direction and 100 dpi in the sub-scanning direction is converted into an output pixel pattern having the same resolution of 600 dpi in both the main scanning direction and the sub-scanning direction. The input reference pattern is a pixel pattern formed in an area of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction (reference area) composed of a central pixel of interest and 8 pixels in the vicinity thereof in the input image data.

With reference to this input reference pattern, resolution conversion is performed by pattern matching so that the target pixel has a desired output resolution. For this purpose, the output pixel pattern of the target pixel is set in advance for all pixel patterns that can be formed in the reference area. The setting of the pixel pattern that can be formed in the reference area will be described later.

Then, the pixel pattern of the input reference pattern is specified by pattern matching, and the output pixel pattern for the target pixel set for the input reference pattern is determined.

Here, the input resolution in the main scanning direction is 20
Since the resolution is 0 dpi and the output resolution is 600 dpi, it is necessary to convert the resolution in the main scanning direction to three times. Since the input resolution in the sub-scanning direction is 100 dpi and the output resolution is 600 dpi, the resolution in the sub-scanning direction is 6 dpi.
You need to double the resolution. Therefore, the output pixel pattern for the target pixel is a pixel pattern having a size of 3 pixels in the main scanning direction × 6 pixels in the sub-scanning direction. Note that the arrangement of the white pixels and the black pixels in the output pixel pattern of the target pixel in FIG. 3B is an example of what is set in advance as corresponding to the input reference pattern in FIG. The pattern corresponding to the input reference pattern shown in FIG. 3A is not limited to this, and can be appropriately changed and set.

As a comparative example, a case of the conventional method will be described with reference to FIGS. 4 (a) to 4 (c). FIGS. 4A to 4C are conceptual diagrams illustrating an example of performing the same resolution conversion as described above by a conventional method. FIG. 4A is an input reference pattern, and FIG. FIG. 4C shows the pixel pattern of the pixel of interest in Process 1 and FIG. 4C shows the output pixel pattern of the pixel of interest in Process 2.

In this method, first, in process 1, an input reference pattern is specified by pattern matching, and the resolution of the target pixel is tripled in both the main scanning direction and the sub-scanning direction according to the specified input reference pattern. That is,
The target pixel is converted into a pixel pattern of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction. This means that the target pixel has been converted to a resolution of 600 dpi in the main scanning direction and 300 dpi in the sub-scanning direction.

Next, as processing 2, the resolution is converted by a method such as simply converting the sub-scanning direction to double (simple double or simple double interpolation), and the resolution of the target pixel in the sub-scanning direction is further increased by two. Convert resolution twice. As a result, an output pixel pattern of 600 dpi is obtained in both the main scanning direction and the sub-scanning direction.

As described above, in the conventional method, first, the processing 1
By performing pattern matching in which the same number of pixel patterns are set in the main scanning direction and the sub-scanning direction of the pixel of interest, the resolution of the main scanning direction and the sub-scanning direction is converted to the same size. As a result of the processing 1, the resolution in either the main scanning direction or the sub-scanning direction is not the desired resolution. Therefore, as the process 2, a process such as simple doubling is required to match the output resolution. Therefore, the conventional method requires a total of two steps of processing.

On the other hand, in the method according to the above-described embodiment, the size of the output pixel pattern is set according to the output resolution in both the main scanning direction and the sub-scanning direction. Therefore, a desired resolution conversion can be realized only by the resolution conversion based on the pattern matching. Thereby, for the input image data whose resolutions in the main scanning direction and the sub-scanning direction are different from each other, the main scanning direction and the sub-scanning direction of the output image can be converted into the same resolution by only one-step processing. .

FIG. 4B, which is an example of the output pixel pattern of the system according to the present embodiment, is compared with FIG. 4C, which is an example of the output pixel pattern of the conventional system.
Is an output pixel pattern with a larger backlash. This is because in the conventional method, processing 2
This requires a method such as simple doubling, so that it is difficult to set the output pixel pattern to a more suitable pixel pattern. Conversely, in order to set the output pixel pattern to a more suitable pixel pattern by the conventional method, it is necessary to perform pattern matching also in the process 2, which complicates the resolution conversion.

On the other hand, in the method according to the present embodiment, it is possible to set a more suitable fine output pixel pattern in accordance with the output resolution by simpler processing. Therefore, the method according to the present embodiment also has an effect that the quality of an output image can be improved.

As described above, in the method according to the above-described embodiment, in the image processing apparatus which performs resolution conversion on input image data to form output image data, RO
M (see FIG. 2) 5 stores a predetermined input pixel pattern and a predetermined output pixel pattern corresponding to the input pixel pattern according to the conversion ratio of the resolution conversion.

The matching processing section 4 (see FIG. 2)
Sets each pixel in the pixel pattern of the input image data as a target pixel, refers to a predetermined reference region for the target pixel, and performs pattern matching between the input reference pattern in the reference region and the input pixel pattern. Do.

Then, the matching processing unit 4 performs resolution conversion by using an output pixel pattern corresponding to an input pixel pattern that matches the input reference pattern by pattern matching as output image data of the target pixel.

In particular, the output pixel pattern is determined by comparing output image data having the same resolution in the main scanning direction and the resolution in the sub-scanning direction with respect to input image data having different resolutions in the main scanning direction and the sub-scanning direction. Is set to form. That is, the size of the output pixel pattern is set according to the output resolution in both the main scanning direction and the sub-scanning direction.

Thus, input image data having different resolutions in the main scanning direction and the sub-scanning direction are converted into the same resolution in the main scanning direction and the sub-scanning direction of the output image data by one-step processing. It becomes possible. Also,
Since the interpolation pixel pattern more suitable for the output resolution can be set, it is possible to improve the image quality of the output image.

Next, setting of a pixel pattern that can be formed in the reference area will be described with reference to FIGS.

As described above, for all input reference patterns (input pixel patterns) that can be formed in the reference area,
The output pixel pattern of the target pixel is set in advance. When the reference area has a size of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction, the type of the input reference pattern has 9 bits, that is, 2 ⁹ = 512 types of pixel patterns exist. Then, as shown in FIG. 5, an output pixel pattern is set for each input reference pattern. Here, FIG. 5 is a conceptual diagram illustrating an example of a correspondence relationship between an input reference pattern and an output pixel pattern. In addition,
FIG. 5 shows only a part of the correspondence and omits the others.

In this case, since the input reference pattern and the output pixel pattern are in one-to-one correspondence, the output pixel pattern for the target pixel can be easily determined by pattern matching. However, in this case, a large memory capacity such as the ROM 5 (see FIG. 2) is required to store all input reference patterns and output pixel patterns.

Here, among the 512 types of input reference patterns, there is a group that becomes the same pixel pattern by inversion, rotation, and black / white inversion. This will be described with reference to FIG. FIG. 6 is a conceptual diagram showing a set of pixel patterns having a specific relationship with a parent input reference pattern which is a basic input reference pattern.

The set of pixel patterns shown in FIG. 6 is obtained by inverting the main input reference pattern in the vertical direction (main scanning direction), inverting the horizontal direction (sub-scanning direction), inverting black and white,
It is a set of pixel patterns having a relationship of 0 ° rotation and a combination thereof. Specifically, for the parent input reference pattern,, +, +, +,
++, +, +, ++, +,
A total of 16 patterns (including the parent input reference pattern) having the respective relationships of ++, ++, and +++ can be classified into the same group.
Then, similarly, the output pixel pattern for the target pixel is
A total of 16 patterns (including the parent output pixel pattern) for the parent output pixel pattern corresponding to the parent input reference pattern can be classified into the same group.

Therefore, only the parent pattern (parent input reference pattern and parent output pixel pattern) is stored in the ROM 5 (FIG. 2).
), And the other pixel patterns may be set so as to recognize which of the above 16 types is in the state. FIG. 7 shows an example of a parent output pixel pattern corresponding to the parent input reference pattern, and a pixel pattern when each of the parent output pixel patterns is in each of the 16 types of states.
FIG. 7 shows a case where the target pixel is converted into a pixel pattern of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction.

As a result, as compared with the case where output pixel patterns are stored for all input reference patterns,
The memory capacity of the ROM 5 (see FIG. 2) can be reduced.

Here, a flow of processing for determining an output pixel pattern for an input reference pattern by the above-described method will be described with reference to FIG. FIG. 8 is a flowchart showing a flow of processing for determining an output pixel pattern for an input reference pattern using a parent pattern.

First, the input reference pattern is collated and recognized as to which parent input reference pattern, and which of the above 16 types is in relation to the parent input reference pattern (step S1). S1). Then, a preset parent output pixel pattern is specified for the recognized parent input reference pattern (step S2). The specified parent output pixel pattern is converted into the same state as the state of the input reference pattern with respect to the parent input reference pattern (any of the above 16 states) (step S).
3). That is, if the input reference pattern is in a vertical inversion relationship with respect to the parent input reference pattern, the output pixel pattern is also obtained by performing a vertical inversion conversion on the identified parent output pixel pattern with respect to the target pixel. It is determined as an output pixel pattern.

As described above, in the above method, the ROM 5
(See FIG. 2) stores a parent input pixel pattern that is a basic pixel pattern as an input pixel pattern, and a parent output pixel pattern corresponding to the parent input pixel pattern as an output pixel pattern.

Further, the matching processing section 4 (see FIG. 2)
Performs pattern matching between an input reference pattern and a parent input pixel pattern that has been subjected to a predetermined conversion.

Then, the matching processing unit performs the same conversion as the above-described conversion performed on the parent input pixel pattern on the parent output pixel pattern corresponding to the parent input pixel pattern that matches the input reference pattern by pattern matching. The resolution conversion is performed by using the obtained pixel pattern as output image data of the target pixel corresponding to the input reference pattern.

Thus, the output pixel pattern can be determined with respect to the input reference pattern while reducing the memory capacity of the ROM 5 (see FIG. 2).

In this embodiment, the reference area of the input reference pattern is 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction.
Although the description has been given of the pixel size, the reference area of the input reference pattern can be changed as appropriate. Also,
Various pixel patterns to be set in advance are stored in the ROM 5 (see FIG. 2) as a storage unit. This storage unit is not limited to the ROM 5, but may be any as long as it can store pixel patterns. Further, here, the case where the input image data and the output image data are binary has been described, but these may be multi-valued. The same applies to the following.

[Second Embodiment] Next, based on input image data having the same resolution in the main scanning direction and the sub-scanning direction, output pixel patterns having different resolutions in the main scanning direction and the sub-scanning direction are set. Will be described.

FIGS. 9A and 9B show output images having different resolutions in the main scanning direction and the sub-scanning direction from input image data having the same resolution in the main scanning direction and the sub-scanning direction. FIG. 9A is a conceptual diagram showing an example of resolution conversion into a pixel pattern. FIG.
(B) shows an output pixel pattern for the target pixel. Here, a pattern having a step is shown as the input reference pattern of FIG.

Here, input image data having a resolution of 100 dpi in both the main scanning direction and the sub-scanning direction is
A case where the output pixel pattern is converted into an output pixel pattern having a resolution of 300 dpi in the main scanning direction and 600 dpi in the sub-scanning direction is shown. As in the case of the first embodiment, the input reference pattern is a pixel pattern formed in an area of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction composed of a central target pixel and 8 pixels in the vicinity thereof. And

Referring to this input reference pattern, resolution conversion is performed by pattern matching so that the target pixel has a desired output resolution. Therefore, as in the first embodiment, the output pixel pattern of the target pixel corresponding to the input reference pattern is set in advance.

Then, the pixel pattern of the input reference pattern is specified by pattern matching, and the output pixel pattern of the target pixel set for the input reference pattern is determined.

Here, the input resolution in the main scanning direction is 10
Since the resolution is 0 dpi and the output resolution is 300 dpi, it is necessary to convert the resolution in the main scanning direction to three times. Since the input resolution in the sub-scanning direction is 100 dpi and the output resolution is 600 dpi, the resolution in the sub-scanning direction is 6 dpi.
You need to double the resolution. Therefore, the output pixel pattern for the target pixel is a pixel pattern having a size of 3 pixels in the main scanning direction × 6 pixels in the sub-scanning direction.

As a comparative example, a case of the conventional method will be described with reference to FIGS. 10 (a) to 10 (c). FIGS. 10A to 10C are conceptual diagrams showing an example of performing the same resolution conversion as described above by a conventional method. FIG. 10A shows an input reference pattern and FIG.
0 (b) shows the pixel pattern obtained by the processing 1, and FIG. 10 (c) shows the output pixel pattern of the target pixel obtained by the processing 2.

In this method, first, in process 1, an input reference pattern is specified by pattern matching, and the resolution of the target pixel is tripled in both the main scanning direction and the sub-scanning direction according to the specified input reference pattern. That is,
The target pixel is converted into a pixel pattern of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction. This means that the target pixel has been converted to a resolution of 300 dpi in both the main scanning direction and the sub-scanning direction.

Next, as processing 2, the sub-scanning direction is
The resolution is converted by a method such as double, and the resolution of the pixel of interest in the sub-scanning direction is further doubled. Thus, 300 dpi in the main scanning direction and 600 dpi in the sub-scanning direction.
Is obtained.

As described above, the conventional system requires a total of two steps of processing, as in the case of the comparative example of the first embodiment.

On the other hand, in the method according to this embodiment, the main scanning direction and the sub-scanning direction of the input image data have the same resolution, and the resolution of the output image data is between the main scanning direction and the sub-scanning direction. If they are different, settings are made so that the output pixel patterns match the output resolution.

Thus, even when the output resolution is different between the main scanning direction and the sub-scanning direction, the main scanning direction and the sub-scanning direction of the output image data are converted into the desired output resolution by one-step processing. It is possible to do. That is, as in the case of the first embodiment, input image data having the same resolution in the main scanning direction and the sub-scanning direction is converted into an output pixel pattern having different resolutions in the main scanning direction and the sub-scanning direction by one step. Can be converted.

Further, in the method according to the present embodiment, similar to the case of the first embodiment, a finer output pixel pattern suitable for the output resolution is set by simpler processing (setting of an interpolation pixel pattern). And the effect of improving the image quality of the output image can be achieved.

As a method of determining an output pixel pattern from an input reference pattern, a method similar to that of the first embodiment can be used.

[Modification 1] Next, a modification of the first and second embodiments will be described.

In this modification, the reference area of the input reference pattern in the input image data is a common area (here, an area of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction) regardless of the resolution conversion rate. The basic pattern of the output pixel pattern for the target pixel, which is determined corresponding to the input reference pattern of the common reference region, is used at an arbitrary resolution conversion rate. Then, an actual output pixel pattern is set by converting the basic pattern according to a certain rule according to the resolution conversion rate.

A specific example of the resolution conversion will be described with reference to FIG. 11A and 11B are conceptual diagrams showing the resolution conversion of the present modification. FIG. 11A shows a basic pattern of an output pixel pattern for a target pixel, and FIG. 3 shows an output pixel pattern of the first embodiment.

Here, the basic pattern of the output pixel pattern shown in FIG.
3 times in the sub-scanning direction (referred to as a resolution conversion rate of 3 × 3, hereinafter also referred to as 3), that is, 3 times in the main scanning direction.
This is obtained by converting the resolution into an output pixel pattern of three pixels in the sub-scanning direction. Using this as a basic pattern, the basic pattern is converted in accordance with each resolution conversion rate to form an output pixel pattern.

For example, FIG.
× 6, that is, an output pixel pattern of 3 pixels in the main scanning direction × 6 pixels in the sub-scanning direction. This output pixel pattern is obtained by converting a pixel pattern obtained by converting the output pixel pattern of FIG. 11A, which is a basic pattern, according to a certain rule (here, simple enlargement (simple double) in the sub-scanning direction). It is set as a pixel pattern.

When an output reproduced image is formed using the pixel patterns shown in FIGS. 11A and 11B as output pixel patterns, FIG. 12A and FIG.
The output reproduction image shown in FIG. FIG. 12 (a)
11A and FIG. 12B, FIG.
Portions respectively corresponding to the output pixel patterns of FIG. 2B are surrounded by double lines.

In the conventional method, pattern matching (processing 1 of the conventional method in the first and second embodiments, FIG.
It is necessary to set the correspondence between the input reference pattern and the output pixel pattern in (a) and FIG. 10 (a) according to the resolution conversion rate. Further, the number of pixels in the main scanning direction and the sub-scanning direction in the output pixel pattern by the pattern matching (the above processing 1) was the same.

On the other hand, in the method according to the present modification, the correspondence between the input reference pattern and the output pixel pattern in the pattern matching may be such that one set of basic patterns is always set regardless of the resolution conversion rate. Therefore, in this method, the memory capacity of the ROM 5 (see FIG. 2) can be significantly reduced.

When the resolution conversion rate is different from that of the basic pattern, that is, when the number of pixels of the desired output pixel pattern is different from the number of pixels of the basic pattern,
By converting the basic pattern according to a certain rule, it becomes possible to obtain output pixel patterns corresponding to each resolution. That is, in this method, the number of pixels of the output pixel pattern in the main scanning direction and the sub-scanning direction can be appropriately changed according to the resolution conversion rate.

As described above, in the above-described method, the ROM (see FIG. 2) is used in the image processing apparatus that converts the resolution of input image data to form output image data.
Stores a predetermined input pixel pattern and a predetermined output pixel pattern corresponding to the input pixel pattern.

The matching processing section 4 (see FIG. 2)
Sets each pixel in the pixel pattern of the input image data as a target pixel, refers to a predetermined reference region for the target pixel, and performs pattern matching between the input reference pattern in the reference region and the input pixel pattern. Do.

Then, the matching processing section 4 forms an output pixel pattern based on a basic pattern corresponding to the input pixel pattern that matches the input reference pattern by pattern matching, and this output pixel pattern corresponds to the input reference pattern. The resolution conversion is performed by using the output image data of the target pixel.

That is, the setting of the reference area is common regardless of the resolution conversion rate, and the setting of the output pixel pattern sets the basic pattern and converts the basic pattern according to the resolution conversion rate.

As a result, the setting of the output pixel pattern for the input reference pattern can be simplified. In other words, the reference area does not need to be changed with respect to the resolution conversion rate, and if only the basic pattern is set without setting the output pixel pattern, the output pixel pattern can be formed by conversion according to a certain rule. Become.
Thereby, the memory capacity of the ROM 5 (see FIG. 2) can be reduced.

In the above, the case where the basic pattern is converted based on a certain rule (for example, simple double) when setting the output pixel pattern from the basic pattern has been described. On the other hand, only a specific basic pattern (a basic pattern requiring another setting (detailed setting); hereinafter, referred to as a specific basic pattern) is converted differently from the above rule (hereinafter, referred to as a specific conversion). May be performed.

The conversion in this case will be described with reference to FIGS. 13 (a) to 13 (d) and FIGS. 14 (a) to 14 (d). FIG. 13A shows a basic pattern.
FIG. 13B shows an output pixel pattern obtained by converting a basic pattern, and FIG. 13C and FIG.
Indicates output pixel patterns obtained by converting the basic pattern by a method different from that in the case of FIG. FIGS. 14A to 14D show output reproduction images when FIGS. 13A to 13D are output pixel patterns, respectively. FIG.
13 (a) to FIG. 1 in FIGS. 13 (a) to 14 (d).
The portion corresponding to the output pixel pattern of FIG. 3D is a range surrounded by a double line.

Here, as the specific basic pattern, for example, there is a pattern in which no step appears in the pixel pattern as shown in FIG. When this specific basic pattern is converted into an output pixel pattern having a resolution conversion rate of 3 × 6 based on the above rule (simple doubling), the result is as shown in FIG.

However, depending on the relationship with peripheral pixels, an output reproduction image such as that shown in FIG. 14B may be formed corresponding to the output pixel pattern shown in FIG. 13B. In this case, since the step is relatively large, FIG.
4 (c) and FIG. 14 (d) are more preferable. That is, in this case, as the output pixel pattern,
13 (c) and 13 (d) respectively corresponding to FIGS. 14 (c) and 14 (d) are preferable.

As in the above-described example, there may be a specific basic pattern that should be converted by a specific conversion set separately, rather than converted based on a certain rule, like the other basic patterns. In this case, it is preferable to separately set the specific conversion only for the specific basic pattern.

At this time, since the conversion is separately set only for the necessary basic pattern, an increase in the memory capacity can be suppressed as much as possible. Then, a higher-quality output image can be obtained.

Note that the specific basic pattern and the specific conversion for the specific basic pattern may be set in advance and stored in the ROM 5 (see FIG. 2) or the like. And it is determined whether or not it is a specific basic pattern by pattern matching,
If it is a specific basic pattern, a specific conversion is performed; if it is not a specific basic pattern, a certain rule (for example, simple double)
The conversion may be performed based on.

As described above, in the present system, when the basic pattern matches a predetermined specific basic pattern among the basic patterns, the matching processing unit 4 (see FIG. 2) Is determined as an output pixel pattern.

As a result, it is possible to separately set an output pixel pattern only for a necessary pixel pattern for each resolution conversion rate. That is, in the setting of the output pixel pattern, a setting different from the conversion from the basic pattern according to a certain rule is separately set only for a necessary pixel pattern. As described above, since only necessary pixel patterns are set, it is possible to obtain a higher-quality output image while minimizing the use of the memory.

[Modification 2] Next, another modification of the first and second embodiments will be described.

In the present modification, when the input reference pattern in the basic reference area conforms to a predetermined pixel pattern (specific pattern, input pixel pattern), the extension of the reference area of the input reference pattern in the extended reference area is performed. Performs pattern matching with the input reference pattern.

First, a case where the reference area is extended in the main scanning direction will be described with reference to FIGS. 15A to 15F and FIGS. 16A to 16D. Here, it is mainly assumed that the input resolution in the main scanning direction and the input resolution in the sub-scanning direction are equal. However, the present invention can be applied to the case where the resolutions in the main scanning direction and the sub-scanning direction are different from each other as described later.

FIGS. 15A to 15F are conceptual diagrams showing examples of specific patterns. FIGS.
FIG. 6D is a conceptual diagram showing a case where an extended reference area is set for the specific pattern in FIG. Note that the “*” mark in FIGS. 16A to 16D indicates that either a white pixel or a black pixel may be used.

Here, a case where there is no step in the main scanning direction in the input reference pattern will be described. For such an input reference pattern, an extended input reference pattern is formed by extending the reference area in the main scanning direction. Then, the presence or absence of a step is confirmed for the extended input reference pattern, and an appropriate output pixel pattern of the target pixel is set based on the result. Note that the output pixel pattern of the target pixel is set in advance corresponding to the extended input reference pattern.

The description will be made with reference to a specific example. In the reference area of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction, as an input reference pattern having no level difference in the main scanning direction, except that all pixels are white pixels or all pixels are black pixels, FIG. Six types shown in FIGS. 15A to 15F can be considered. When the input reference pattern conforms to these pixel patterns (specific patterns), pattern matching is performed with an extended input reference pattern obtained by extending the input reference pattern in the main scanning direction.

As the extended input reference pattern, for example, as shown in FIGS. 16 (a) to 16 (d), a pixel pattern appearing in an extended reference area obtained by extending the reference area by two pixels before and after in the main scanning direction, respectively. I do. Even if the input reference pattern is the specific pattern shown in FIG. 15A where no step is present, if a step is detected for the extended input reference pattern, for example, the pattern changes from FIG. 16A to FIG. 16D. As shown, a step is detected in a plurality of cases. As described above, an output pixel pattern suitable for the target pixel of the extended input reference pattern (specific extended pattern) for which a step is detected is set in advance.

The flow of the above processing will be described with reference to FIG. FIG. 17 is a flowchart illustrating a flow of a process of performing resolution conversion on a specific pattern.

First, pattern matching (first pattern matching) is performed between an input reference pattern in a reference region consisting of a central pixel of interest and its neighboring pixels (step S11). Then, it is determined whether or not the input reference pattern matches the specific pattern, that is, whether or not a step exists in the input reference pattern (step S12).

If the input reference pattern does not conform to the specific pattern in step S12, resolution conversion is performed using a normal output pixel pattern (step S1).
3).

On the other hand, if the input reference pattern matches the specific pattern in step S12, pattern matching (second pattern matching) with the extended input reference pattern in the extended reference area obtained by expanding the reference area is performed. It is determined whether or not a step exists in the reference pattern (step S14). If there is no step in the extended input reference pattern in step S14, resolution conversion is performed using a normal output pixel pattern (step S13). If there is a step in the extended input reference pattern in step S14, resolution conversion is performed using an output pixel pattern predetermined in correspondence with the extended input reference pattern (step S15).

Next, a case where the reference area is extended in the sub-scanning direction will be described with reference to FIGS. 18 (a) to 18 (f) and FIGS. 19 (a) to 19 (d). As described above, here, it is mainly assumed that the resolutions in the main scanning direction and the sub-scanning direction are the same, but the present invention can also be applied to the case where the resolutions in the main scanning direction and the sub-scanning direction are different from each other.

FIGS. 18A to 18F are conceptual diagrams showing examples of specific patterns. FIGS.
FIG. 9D is a conceptual diagram showing a case where an extended reference area is set for the specific pattern in FIG. Note that the “*” mark in FIGS. 19A to 19D indicates that either a white pixel or a black pixel may be used.

Here, a case where there is no step in the sub-scanning direction in the input reference pattern will be described. For such an input reference pattern, the reference area is extended in the sub-scanning direction to form an extended input reference pattern. Then, whether or not there is a step with respect to this extended input reference pattern as described above,
That is, it is determined whether or not it is a specific expansion pattern, and an output pixel pattern for the target pixel is set.

The following is a description using a specific example. In the reference area of 3 pixels in the main scanning direction × 3 pixels in the sub-scanning direction, as an input reference pattern having no level difference in the sub-scanning direction, except that all pixels are white pixels or all pixels are black pixels, FIG. Six types shown in FIGS. 18A to 18F can be considered. When the input reference pattern conforms to these pixel patterns (specific patterns), pattern matching is performed with an extended input reference pattern obtained by extending the input reference pattern in the sub-scanning direction.

As the extended input reference pattern, for example, as shown in FIGS. 19A to 19D, a pixel pattern appearing in an extended reference area obtained by extending the reference area by two pixels before and after the main scanning direction, respectively. I do. Even if the specific pattern shown in FIG. 18A has no step as the input reference pattern, when the step is detected for the extended input reference pattern, for example, the pattern changes from FIG. 19A to FIG. 19D. As shown, a step is detected in a plurality of cases. As described above, an output pixel pattern suitable for the target pixel of the extended input reference pattern for which a step is detected is set in advance.

The flow of this processing is described in FIG.
Since the description is based on the description based on, the description thereof is omitted.

As described above, in the basic reference region, the presence or absence of a step is confirmed by expanding the reference region only when a step cannot be detected in the main scanning direction or the sub-scanning direction.
Then, when a step exists in the extended input reference pattern in the extended reference area, an output pixel pattern suitable for the step is set as a corresponding target pixel. This makes it possible to set a more suitable output pixel pattern while suppressing the complexity of the pattern matching process.

Here, the case where there is no step in the main scanning direction or the sub-scanning direction in the input reference pattern as the specific pattern has been described. However, the present invention is not limited to these and other specific patterns can be set to set the output image. Image quality can be improved.

Further, FIGS. 20 (a) to 20 (c),
FIGS. 21 (a), 21 (b), 22 (a) and 2
A method of expanding the reference area to an appropriate size and performing pattern matching when input resolutions in the main scanning direction and the sub-scanning direction are different from each other based on 2 (b) will be described. FIG. 20 is a conceptual diagram showing the relationship between the input resolution in the main scanning direction and the sub-scanning direction and the image range of the reference image (input image). FIG. 21A and FIG.
FIGS. 22B and 22A and 22B are conceptual diagrams showing the relationship between the input resolution in the main scanning direction and the sub-scanning direction and the extended reference area.

If the resolution in the main scanning direction and the resolution in the sub-scanning direction of the input image data are different from each other, the number of input reference pixels in the reference area is the same in the main scanning direction and the sub-scanning direction, that is, the reference area is square. Even so, the image range of the reference image corresponding to the reference area is different from a square. That is, the image range of the reference image becomes narrower in the direction where the input resolution is higher.

The details are as follows. FIG. 20 (a)
As shown in the figure, a case is considered where the number of input reference pixels in the reference area is equal in three pixels in the main scanning direction and three pixels in the sub scanning direction, that is, the reference area is a square. At this time, the input resolution is 100 dpi in the main scanning direction and 100 dpi in the sub-scanning direction.
As shown in FIG. 20B, the corresponding image range of the reference image is a square. On the other hand, assuming that the input resolution is 200 dpi in the main scanning direction and 100 dpi in the sub-scanning direction, as shown in FIG. 20C, the corresponding image range of the reference image is long in the sub-scanning direction where the input resolution is low, and Becomes a rectangular image area that is short in the main scanning direction.

In such a case, even if the reference area is expanded by the above-described method, the reference area may not be optimal due to a difference in input resolution between the main scanning direction and the sub-scanning direction. .

Therefore, when the reference area is extended in the case where there is no step in the input reference pattern, the size of the extended reference area in the main scanning direction and the sub-scanning direction is determined according to the relationship (ratio) between the respective input resolutions. It is preferable to change it.

The change of the size of the extended reference area will be specifically described. For example, FIG. 21 (a) and FIG.
As shown in (a), the size of the basic reference area is 3 pixels in the main scanning direction × 3 pixels in the sub scanning direction, and the input resolution is 200 dpi in the main scanning direction and 100 dpi in the sub scanning direction, and 700 dpi in the main scanning direction. , Sub-scanning direction 9
Consider the case of 00 dpi.

As shown in FIG. 21A, when the input resolution is 200 dpi in the main scanning direction and 100 dpi in the sub-scanning direction, and there is no step in the input reference pattern in the reference area, for example, the reference area is moved forward and backward in the main scanning direction. 5 pixels each, and two pixels before and after in the sub-scanning direction. That is, the reference area is an extended reference area of 13 pixels in the main scanning direction × 3 pixels in the sub-scanning direction and 3 pixels in the main scanning direction × 7 pixels in the sub-scanning direction, as shown in FIG.

When the input resolution is 700 dpi in the main scanning direction and 900 dpi in the sub-scanning direction and there is no step in the input reference pattern in the reference area as shown in FIG. , And three pixels before and after in the sub-scanning direction. That is, the reference region is an extended reference region of 7 pixels in the main scanning direction × 3 pixels in the sub-scanning direction and 3 pixels in the main scanning direction × 9 pixels in the sub-scanning direction, as shown in FIG.

That is, when the extended reference area is formed by extending the reference area, the extended width in the high input resolution direction is made larger than the extended width in the low input resolution direction in the main scanning direction and the sub-scanning direction. (Increase the number of pixels).

As described above, by changing the size of the extended reference area to an appropriate size corresponding to the difference in input resolution, more accurate pixel pattern information of the input image can be obtained. Therefore, it is possible to set a more appropriate output pixel pattern.

In the above description, a specific extension pattern having no step in the extended reference pattern has been described. However, the specific extension pattern is not limited to this, and a preset pattern can be used.

[Modification 3] Next, Embodiments 1 and 2
This is still another modification of the first embodiment, and a combination of the processes of the first and second modifications will be described with reference to FIG. FIG. 23 is a flowchart showing the flow of the processing of this modification.

First, pattern matching (first pattern matching) is performed between an input reference pattern in a basic reference area including a central target pixel and its neighboring pixels (step S21). Then, it is determined whether or not the input reference pattern matches the above-described specific pattern (step S22).

If the input reference pattern does not match the specific pattern in step S22, it is determined whether or not the basic pattern for the target pixel matches the specific basic pattern (step S2).
3).

Here, when the target pixel conforms to the specific basic pattern, that is, when the output pixel pattern of the detailed setting corresponding to the resolution conversion rate is set for the target pixel, the corresponding output Resolution conversion is performed by the pixel pattern (step S24).

If the target pixel does not conform to the specific basic pattern, that is, if the output pixel pattern of the detailed setting is not set for the target pixel, the basic pattern corresponding to the target pixel is set to Conversion is performed according to a predetermined rule in accordance with the resolution conversion rate in the main scanning direction and the sub-scanning direction, and resolution conversion is performed using the converted output pixel pattern (step S25).

On the other hand, if the input reference pattern conforms to the specific pattern in step S22, the reference area is extended according to the relationship (ratio) between the input resolutions in the main scanning direction and the sub scanning direction, and the extended input With reference to the reference pattern, it is determined whether or not the extended input reference pattern matches the specific extended pattern by pattern matching (second
(Step S2)
6).

In step S26, if the extended input reference pattern does not match the specific extended pattern, the flow shifts to step S23, and thereafter, the same processing as described above is performed.

In step S26, if the extended input reference pattern conforms to the specific extended pattern, resolution conversion is performed using an output pixel pattern predetermined in correspondence with the extended input reference pattern (step S2).
7).

In this case as well, the setting of the basic reference area is common regardless of the resolution conversion rate. Also, the formation of output pixel patterns other than the detailed settings
A basic pattern is set in advance for an input reference pattern, and conversion is performed from the basic pattern according to a predetermined rule according to a resolution conversion rate. In addition, only an output pixel pattern of a detailed setting is set in advance only for a pixel pattern necessary from the viewpoint of improvement of image quality, and a conversion different from the conversion from the basic pattern according to a certain rule is separately set. The extended input reference pattern used in step S26 is set in advance according to the relationship (ratio) between the input resolutions in the main scanning direction and the sub-scanning direction.

[0171]

As described above, the image processing apparatus according to the present invention stores an input pixel pattern and an output pixel pattern which is predetermined according to the input pixel pattern in accordance with the conversion ratio of the resolution conversion. In this configuration, resolution conversion is performed by using pattern matching to set an output pixel pattern corresponding to an input pixel pattern that matches the input reference pattern as output image data of a target pixel corresponding to the input reference pattern.

In this configuration, the output pixel pattern corresponds to the input pixel pattern and is set according to the conversion rate of the resolution conversion. Therefore, the resolution of the input image data is converted to the desired resolution of the output image data by a one-step process, that is, a process of setting the output pixel pattern corresponding to the input pixel pattern that matches the input reference pattern as the output image data of the target pixel. can do. That is, resolution conversion can be realized by simpler processing.

Further, since the output pixel pattern can be more appropriately interpolated according to the output resolution and set to a more suitable pixel pattern, the image quality of the output image can be improved.

The image processing apparatus according to the present invention is the image processing apparatus described above, further comprising an output pixel pattern for converting input image data having different resolutions in the main scanning direction and the sub-scanning direction from each other. It is preferable that the setting is made such that the image data is converted into output image data having the same resolution in the sub-scanning direction.

Thus, input image data having different resolutions between the main scanning direction and the sub-scanning direction can be converted into output image data having the same resolution in the main scanning direction and the sub-scanning direction by one-step processing. it can.

The image processing apparatus according to the present invention is the image processing apparatus according to the above-mentioned image processing apparatus, further comprising an output pixel pattern for input image data having the same resolution in the main scanning direction and the resolution in the sub-scanning direction. And the resolution in the sub-scanning direction are preferably set so as to be converted into output image data different from each other.

Thus, input image data having the same resolution in the main scanning direction and the sub-scanning direction can be converted into output image data having different resolutions in the main scanning direction and the sub-scanning direction by one-step processing. it can.

As described above, the image processing apparatus of the present invention
An input pixel pattern and a basic pattern predetermined corresponding to the input pixel pattern are stored, and an output pixel pattern is determined by pattern matching based on the basic pattern corresponding to the input pixel pattern that matches the input reference pattern. The resolution conversion is performed by forming the output pixel pattern as the output image data of the target pixel corresponding to the input reference pattern.

In this configuration, unlike the conventional configuration in which an output pixel pattern is set for each resolution conversion rate, a common combination of an input pixel pattern and a basic pattern is set for each resolution conversion rate. An output pixel pattern can be formed by converting the pattern. Therefore, since it is not necessary to form an output pixel pattern according to each resolution conversion rate, the memory capacity can be reduced.

An image processing apparatus according to the present invention is an image processing apparatus for forming an output pixel pattern based on the basic pattern described above, further comprising the step of converting the basic pattern in accordance with a predetermined rule in accordance with the conversion rate of resolution conversion. To form an output pixel pattern.

In the above arrangement, the basic pattern is converted according to a predetermined rule to form an output pixel pattern. That is, an output pixel pattern can be formed by performing a certain process on the basic pattern. Therefore, it is possible to simplify the processing while reducing the memory capacity described above.

An image processing apparatus according to the present invention is an image processing apparatus for forming an output pixel pattern based on the above-mentioned basic pattern, and further comprising a special basic pattern when the basic pattern conforms to a predetermined specific basic pattern. Preferably, a pixel pattern predetermined for the pattern is used as the output pixel pattern.

In the above configuration, only a basic pattern for which it is preferable to set an individual output pixel pattern from the viewpoint of the image quality of an output image is used as a specific basic pattern, and an appropriate pixel pattern is output for each specific basic pattern. Can be set as a pattern. As a result, it is possible to improve the image quality of the output image while minimizing the increase in the memory capacity.

As described above, the image processing apparatus of the present invention
A first pattern matching is performed between an input reference pattern that is a pixel pattern in the reference area and an input pixel pattern that is a predetermined pixel pattern among the pixel patterns that can appear in the reference area, and the input reference pattern becomes the input pixel pattern. When the reference area is matched, the reference area is extended, and an extended input reference pattern that is a pixel pattern in the extended extended reference area and a second pattern matching between the extended input pixel pattern that is a pixel pattern that can appear in the extended reference area are performed. In this configuration, resolution conversion is performed based on the result of the second pattern matching.

Further, the image processing apparatus according to the present invention, when the extended input reference pattern matches a predetermined extended input pixel pattern among the extended input pixel patterns, outputs the output pixel pattern corresponding to the extended input pixel pattern. It is preferable to perform resolution conversion by using output image data of a target pixel.

In the above configuration, the first pattern matching is performed, and if the input reference pattern is a predetermined one, the reference area is extended. Then, the second pattern matching is performed on the extended reference area. The resolution conversion is performed by the resolution conversion unit based on the result of the second pattern matching. Thus, in the second pattern matching, the presence or absence of a step in a wider area can be detected, and the resolution conversion can be performed in consideration of this. Therefore, the image quality of the output image can be further improved.

An image processing apparatus according to the present invention is an image processing apparatus which performs resolution conversion based on the result of the above-described second pattern matching. It is preferable to extend in the scanning direction or the sub-scanning direction.

In the above configuration, for example, when there is no step in the main scanning direction or the sub-scanning direction in the input reference pattern, the reference area is expanded in the main scanning direction or the sub-scanning direction, respectively, and the presence or absence of the step is confirmed. be able to.
This makes it possible to set a more suitable output pixel pattern for the target pixel while suppressing the complexity of the process and the increase in the memory capacity.

An image processing apparatus according to the present invention is an image processing apparatus which performs resolution conversion based on the result of the above-mentioned second pattern matching. Preferably, the extension width is determined according to the resolution in the sub-scanning direction.

As a result, the image range to be referred to can be appropriately set to, for example, a square, so that an extended input pixel pattern with more accurate information can be obtained, and a more appropriate output pixel pattern can be set. Become possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a digital copying machine employing a reversal development system according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 3 illustrates an example of resolution conversion of input image data having different resolutions in the main scanning direction and the sub-scanning direction into an output pixel pattern of the same resolution in the first embodiment of the present invention. It is a conceptual diagram, (a) is a conceptual diagram which shows an input reference pattern, (b) is a conceptual diagram which shows the output pixel pattern of a target pixel.

FIG. 4 shows a conventional method as a comparative example of the present invention.
FIG. 7 is a conceptual diagram showing an example when input image data having different resolutions in the main scanning direction and the sub-scanning direction is converted into an output pixel pattern of the same resolution, and FIG. FIG. 3B is a conceptual diagram illustrating a pixel pattern of a target pixel according to a process 1, and FIG. 3C is a conceptual diagram illustrating an output pixel pattern of the target pixel according to a process 2.

FIG. 5 is a conceptual diagram illustrating an example of a correspondence relationship between an input reference pattern and an output pixel pattern in the first embodiment.

FIG. 6 is a conceptual diagram showing a set of patterns having a specific relationship with a parent input reference pattern that is a basic input reference pattern in the first embodiment.

FIG. 7 is a conceptual diagram showing an example of a parent output pixel pattern corresponding to a parent input reference pattern in the first embodiment, and a pattern when each of the parent output pixel patterns is in 16 types of states.

FIG. 8 is a flowchart illustrating a flow of a process of determining an output pixel pattern for an input reference pattern using a parent pattern in the first embodiment.

FIG. 9 is a diagram illustrating output pixels having different resolutions in the main scanning direction and the sub scanning direction from input image data having the same resolution in the main scanning direction and the sub scanning direction in the second embodiment of the present invention. It is a conceptual diagram which shows an example at the time of resolution conversion into a pattern, (a) is a conceptual diagram of an input reference pattern,
(B) is a conceptual diagram of an output pixel pattern of a target pixel.

FIG. 10 shows a conventional method as a comparative example of the present invention, in which, from input image data in which the main scanning direction and the sub-scanning direction have the same resolution, outputs having different resolutions in the main scanning direction and the sub-scanning direction. FIGS. 7A and 7B are conceptual diagrams illustrating an example of resolution conversion into a pixel pattern. FIG. 7A is a conceptual diagram of an input reference pattern, FIG. It is a conceptual diagram of the output pixel pattern of a pixel.

FIGS. 11A and 11B are conceptual diagrams illustrating resolution conversion as a first modification in the embodiment of the present invention, in which FIG. 11A is a conceptual diagram of a basic pattern of an output pixel pattern for a target pixel;
(B) is a conceptual diagram of an actual output pixel pattern obtained by converting a basic pattern.

FIGS. 12 (a) and (b) respectively show FIGS.
FIG. 12A is a conceptual diagram showing an output reproduction image based on the output pixel patterns of FIG. 11B and FIG.

13A is a conceptual diagram showing a basic pattern, FIG. 13B is a conceptual diagram showing an output pixel pattern obtained by converting the basic pattern, and FIGS. FIG. 10 is a conceptual diagram of an output pixel pattern obtained by converting a basic pattern by a method different from that of FIG.

FIGS. 14 (a) to (d) respectively show FIG. 13 (a).
FIG. 14 is a conceptual diagram showing an output reproduction image of the output pixel pattern of FIG.

FIGS. 15A to 15F are conceptual diagrams showing examples of specific patterns in a second modification of the present invention.

FIGS. 16A to 16D are conceptual diagrams showing extended reference areas for the specific pattern of FIG.

FIG. 17 is a flowchart illustrating a flow of a process of performing resolution conversion on a specific pattern in a second modified example.

FIGS. 18 (a) to (f) are conceptual diagrams showing examples of specific patterns in a second modification of the present invention.

FIGS. 19A to 19D are conceptual diagrams showing extended reference areas for the specific pattern in FIG. 18A.

FIG. 20 is a conceptual diagram showing a relationship between an input resolution in a main scanning direction and a sub-scanning direction and an image range of a reference image in a second modified example.

FIGS. 21 (a) and (b) are conceptual diagrams showing the relationship between the input resolution in the main scanning direction and the sub-scanning direction and the extended reference area in the second modified example.

FIGS. 22A and 22B are conceptual diagrams showing a relationship between an input resolution in a main scanning direction and a sub-scanning direction and an extended reference area in a second modified example.

FIG. 23 is a flowchart illustrating the flow of a process according to a third modified example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Input part 2 Bit map memory 3 Central processing unit (CPU) 4 Matching processing part (matching part, resolution conversion part) 5 Read-only memory (storage part, ROM) 6 Buffer memory 7 Output part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Nakamura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Noriyuki Yasuoka 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Masaaki Otsuki 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term within Sharp Corporation (reference) 2C362 CB07 CB12 5B057 CD05 5C076 AA21 AA22 BA07 BB04 BB40 CA10

Claims (10)

[Claims] 1. An image processing apparatus for performing resolution conversion on input image data to form output image data, comprising: a storage unit for storing a predetermined pixel pattern; and each pixel in the pixel pattern of the input image data. Is referred to as a target pixel, a reference region which is a region on the pixel pattern of the input image data including the target pixel is referred to, and an input reference pattern which is a pixel pattern in the reference region and a pixel pattern which can appear in the reference region A matching unit that performs pattern matching with an input pixel pattern stored in the storage unit and specifies the input pixel pattern that matches the input reference pattern; and the specified input pixel according to a conversion rate of resolution conversion. The output pixel pattern stored in the storage unit corresponding to the pattern corresponds to the reference area. The image processing apparatus characterized by comprising a resolution conversion section that performs resolution conversion by the output image data of the serial pixel of interest. 2. The output pixel pattern according to claim 1, wherein the resolution in the main scanning direction and the resolution in the sub scanning direction are equal to each other for the input image data having different resolutions in the main scanning direction and the sub scanning direction. The image processing apparatus according to claim 1, wherein the image processing apparatus is set to form output image data. 3. The output pixel pattern according to claim 1, wherein the resolution in the main scanning direction and the resolution in the sub scanning direction are different from each other for the input image data having the same resolution in the main scanning direction and the resolution in the sub scanning direction. The image processing apparatus according to claim 1, wherein the image processing apparatus is set to form output image data. 4. An image processing apparatus for performing resolution conversion on input image data to form output image data, comprising: a storage unit for storing a predetermined pixel pattern; and each pixel in the pixel pattern of the input image data. Is referred to as a target pixel, a reference region which is a region on the pixel pattern of the input image data including the target pixel is referred to, and an input reference pattern which is a pixel pattern in the reference region and a pixel pattern which can appear in the reference region A matching unit that performs pattern matching with an input pixel pattern stored in the storage unit and specifies the input pixel pattern that matches the input reference pattern; and the storage unit corresponding to the specified input pixel pattern. Output pixel pattern based on a common basic pattern with respect to the conversion rate of the resolution conversion. Down to form an image processing apparatus, characterized in that it comprises a resolution conversion unit which performs resolution conversion by the output pixel pattern the formation, and the output image data of the target pixel corresponding to the reference area. 5. The output pixel pattern according to claim 4, wherein the resolution conversion section converts the basic pattern according to a predetermined rule according to a conversion rate of the resolution conversion to form the output pixel pattern. Image processing device. 6. The resolution conversion unit, wherein when the basic pattern conforms to a predetermined basic pattern among the basic patterns, the resolution conversion unit stores the basic pattern in the storage unit in correspondence with the basic pattern. The image processing apparatus according to claim 4, wherein a pixel pattern is the output pixel pattern. 7. An image processing apparatus for performing resolution conversion on input image data to form output image data, wherein: a storage unit for storing a predetermined pixel pattern; and each pixel in the pixel pattern of the input image data Is referred to as a target pixel, a reference region which is a region on the pixel pattern of the input image data including the target pixel is referred to, and an input reference pattern which is a pixel pattern in the reference region and a pixel pattern which can appear in the reference region Performing a first pattern matching with an input pixel pattern that is a predetermined pixel pattern stored in the storage unit, and expanding the reference area when the input reference pattern matches the input pixel pattern; An extended input reference pattern that is a pixel pattern in the extended extended reference area; A matching unit that performs a second pattern matching with an extended input pixel pattern that is a pixel pattern that can be stored in the storage unit; and a resolution conversion unit that performs a resolution conversion based on the result of the second pattern matching. An image processing apparatus characterized by the above-mentioned. 8. The resolution conversion section, when the extended input reference pattern matches a predetermined extended input pixel pattern among the extended input pixel patterns in the result of the second pattern matching. The resolution conversion is performed by using an output pixel pattern stored in the storage unit corresponding to an input pixel pattern as output image data of the target pixel corresponding to the reference area. The image processing apparatus according to any one of the preceding claims. 9. The image processing apparatus according to claim 7, wherein when the reference area is extended, the reference area is extended in a main scanning direction or a sub scanning direction of the input image data. apparatus. 10. The method according to claim 1, wherein when the reference area is extended, an extension width of the reference area is determined according to a resolution of the input image data in a main scanning direction and a resolution in a sub-scanning direction. 10. The image processing device according to any one of 7 to 9.