JP2004320258A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for carrying out the reduction processing that prevents white / black stripes caused by the connected white pixels or black pixels so as to reduce deterioration in the image quality. <P>SOLUTION: An image processing section 22 stores the number of pixels included in each unit for thinning pixels whose pixel is 1, calculated in a control section 10 on the basis of a set reduction rate, to a register 30 and particularizes the pixel data to be thinned among image data sequentially acquired from a CODEC 18 and stored in a memory 32 on the basis of the number of pixels. Further, a comparison circuit 31 compares the particularized pixel data with the pixel data adjacent to the particularized pixel data and a resolution conversion section 33 thinnes the particularized pixel data when the result of the comparison indicates coincidence. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus for thinning out pixels based on a received reduction ratio from an image in which a plurality of pixels are arranged in a matrix and reducing the image.
[0002]
[Prior art]
Generally, an image processing apparatus performs a reduction process by thinning out appropriate pixels on an image configured by arranging a plurality of pixels in a main scanning direction and a sub-scanning direction, and also appropriately performs image processing between adjacent pixels. The enlargement process is performed by inserting an interpolation pixel.
However, when the above-described reduction processing is performed on a pseudo halftone image in which halftone is formed by alternation of black and white by performing dither processing or the like, the dither pattern is broken, and black pixels are separated in the original image. The white pixels or the black pixels which are arranged with the white pixels separated from each other may be connected to each other to cause white streaks or black streaks, thereby deteriorating the image quality. Such white streaks or black streaks are remarkable in the case of a pseudo halftone image.
[0003]
Therefore, for example, when reducing the image, the position of the pixel to be thinned out is determined for each line in the main scanning direction or the sub-scanning direction so that each pixel to be thinned out does not continue in the main scanning direction or the sub-scanning direction. There has been proposed an image processing apparatus that prevents deterioration in image quality by changing and determining pixels to be thinned out at random (for example, see Patent Document 1).
By using such an image processing apparatus, it is possible to prevent not only continuous loss of white pixels or black pixels but also generation of white streaks or black streaks due to the connection of white pixels or black pixels.
[0004]
[Patent Document 1]
JP-A-11-120341
[Problems to be solved by the invention]
However, the image processing apparatus disclosed in Patent Document 1 does not determine the pixels to be thinned out according to the data value of each pixel in the image to be processed, and thus determines the optimum thinned pixels for all the images. There is a problem that, depending on the image, the occurrence of white streaks or black streaks due to the connection of white pixels or black pixels cannot be reliably prevented depending on the image.
[0006]
The present invention has been made in view of such circumstances, and the number of pixels based on the received reduction ratio is defined as one unit, pixels to be thinned out are specified for each unit, and the data value of the specified pixel is adjacent to the pixel. An image processing apparatus that performs reduction processing to prevent the connection of white pixels or black pixels and reduce deterioration in image quality by thinning out the specified pixels when the data values are the same as at least one of the matching pixels. The purpose is to provide.
[0007]
Another object of the present invention is that when the data value of a pixel specified to be decimated is not the same as the data value of a pixel adjacent to the pixel, the data value in the vicinity of the specified pixel is the same and adjacent. It is an object of the present invention to provide an image processing apparatus capable of preventing connection of a white pixel or a black pixel which may occur when the specified pixel is thinned by thinning one of a plurality of pixels. .
[0008]
Still another object of the present invention is to detect a plurality of adjacent pixels having the same data value in each unit consisting of the number of pixels calculated based on the received reduction ratio, thereby determining the positions of the pixels to be thinned out. An object of the present invention is to provide an image processing apparatus which can provide a range and can prevent deviation of positions of pixels to be thinned out.
[0009]
Yet another object of the present invention is to reduce the number of pixels specified to be thinned out when a plurality of adjacent pixels having the same data value cannot be detected. It is an object of the present invention to provide an image processing apparatus capable of preventing deviation of positions of pixels to be thinned out.
[0010]
[Means for Solving the Problems]
The image processing apparatus according to the first invention is configured such that, based on the received reduction ratio, the number of pixels corresponding to the reduction ratio is defined as one unit, from an image in which a plurality of pixels are arranged in a matrix, and one unit for each unit. In an image processing apparatus for thinning out pixels and reducing the image, a specifying means for specifying a pixel to be thinned out for each unit, and a data value of the pixel specified by the specifying means is a data value of at least one pixel adjacent to the pixel. It is characterized by comprising a judging means for judging whether or not the value is the same, and a thinning means for thinning out the pixel specified by the specifying means when the judging means judges the same.
[0011]
In the case of the first invention, the number of pixels included in each unit for thinning out one pixel is calculated based on the received reduction ratio, and the calculated number of pixels is defined as one unit, and the pixel to be thinned out is specified for each unit. Further, it is determined whether or not the data value of the specified pixel is the same as the data value of at least one pixel adjacent to the pixel. If the data value is the same, the specified pixel is thinned out to reduce whiteness. It is possible to perform reduction processing for preventing the occurrence of connection of pixels or black pixels and reducing deterioration of image quality.
[0012]
The image processing apparatus according to a second aspect of the present invention includes a detecting unit that detects a plurality of adjacent pixels having the same data value from the vicinity of the pixel specified by the specifying unit when the determining unit determines that the pixels are not the same. , Wherein the thinning means is configured to thin one of the pixels detected by the detecting means.
[0013]
According to the second aspect, when the data value of a pixel specified to be thinned out is not the same as the data value of a pixel adjacent to the pixel, a plurality of data values adjacent to the specified pixel are identified from the vicinity of the specified pixel. By detecting one of the pixels and decimating one of the detected pixels, it is possible to prevent the connection of white pixels or black pixels that may occur when the specified pixel is decimated. Can reduce the deterioration of the image quality.
[0014]
An image processing apparatus according to a third aspect is characterized in that the detecting means is configured to detect a plurality of adjacent pixels having the same data value in each unit.
[0015]
In the case of the third invention, a plurality of adjacent pixels having the same data value are detected in each unit composed of the number of pixels calculated based on the received reduction ratio, so that the range of the positions of the pixels to be thinned is determined. This can prevent the bias of the positions of the pixels to be thinned out, and can reduce the load of the detection processing by preventing endless repetition of the above-described detection processing.
[0016]
An image processing apparatus according to a fourth aspect is configured such that the thinning-out unit thins out the pixels specified by the specifying unit when the detecting unit cannot detect a plurality of adjacent pixels having the same data value. There is a feature.
[0017]
According to the fourth aspect, as described above, when a plurality of adjacent pixels having the same data value cannot be detected, the pixels identified to be thinned out are thinned out, so that the reduction process by the thinning process can be reliably performed. In addition to this, it is possible to prevent the deviation of the positions of the pixels to be thinned out.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an image processing apparatus according to the present invention will be described in detail based on an embodiment using a multifunction peripheral. FIG. 1 is a block diagram showing a configuration example of a multifunction peripheral according to the present invention. In the figure, reference numeral 1 denotes a multifunction peripheral.
The multifunction device 1 includes a control unit 10, a ROM 11, a RAM 12, an NCU (Network Control Unit) 13, a modem 14, a reading unit 15, a display unit 16, an operation unit 17, a CODEC 18, a code memory 19, an image memory 20, an image recording unit 21, , An image processing unit 22, etc., and are connected to each other via a bus 23.
[0019]
The control unit 10 is specifically configured by a CPU (Central Processing Unit) or an MPU (Micro Processor Unit), and controls the above-described hardware via the bus 23 and is stored in the ROM 11. Various software functions are realized according to the computer program.
The ROM 11 stores various computer programs and the like necessary for the operation of the multifunction peripheral 1 of the present invention in advance.
[0020]
The RAM 12 is configured by an SRAM, a flash memory, or the like, and temporarily stores data generated when the control unit 10 executes the computer program, and the obtained magnification. If a flash memory is used as the RAM 12, the stored contents will not be lost even if the power is cut off due to a power failure, movement of the MFP 1, or the like.
The modem 14 is constituted by a facsimile modem capable of performing facsimile communication, and is also directly connected to the NCU 13. The NCU 13 is connected to the public telephone network L, connects the modem 14 to the public telephone network L as necessary, and performs facsimile communication with another facsimile apparatus via the public telephone network L. It is possible.
[0021]
The display unit 16 is configured by a liquid crystal display (LCD) or the like, and displays an operation state of the multifunction device 1, data to be notified to a user, characters input from the operation unit 17, and the like.
The operation unit 17 includes various function keys necessary for operating the multifunction device 1, keys for inputting a magnification by the user, and the like. By using the touch panel type display unit 16, some or all of the various keys of the operation unit 17 can be substituted.
[0022]
The reading unit 15 reads an original using a scanner using a CCD (Charge Coupled Device), and inputs the read image data to the CODEC 18.
The CODEC 18 encodes the image data read by the reading unit 15 and stores the encoded image data in the code memory 19.
[0023]
The code memory 19 includes a DRAM or the like, and stores image data read by the reading unit 15 and encoded by the CODEC 18, and image data obtained from another facsimile apparatus via the NCU 13 and the modem 14.
In the present embodiment, the image data to be obtained is binary image data in which each pixel is specified by binary data. The scaling factor can be calculated not only by the user but also based on the size of the recording paper to be output specified by the user.
[0024]
The CODEC 18 is configured to decode the encoded image data stored in the code memory 19, decodes the image data read from the code memory 19, and performs image processing according to an instruction from the control unit 10. It is input to the unit 22 or the recording unit 21.
Here, the control unit 10 determines whether or not to perform a reduction process on an image to be printed on a recording sheet or the like, based on a setting of a scaling ratio by a user or a setting of a size of a recording sheet by a user, When the reduction processing is executed, specifically, when the set scaling ratio is smaller than 100%, the decoded image data is input to the image processing unit 22. When the reduction processing is not executed, the CODEC 18 is output. , And causes the recording unit 21 to input the decoded image data.
[0025]
Note that the image processing unit 22 in the present embodiment has a configuration for executing only the reduction processing, and the control unit 10 stores the image data decoded by the CODEC 18 in the recording unit 21 when not executing the reduction processing. However, an image processing unit for performing the enlargement process is separately provided, and when the set scaling ratio is larger than 100%, the decoded image data is input to this image processing unit. You may make it.
[0026]
The image processing unit 22 has a configuration as described later, and, based on image data decoded by the CODEC 18, pixel data (pixel data) constituting the image data based on the reduction ratio indicated by the scaling factor stored in the RAM 12. (Data value) is appropriately thinned out, and the obtained image data is temporarily stored in the image memory 20.
[0027]
The image memory 20 includes a DRAM or the like, stores image data obtained from the image processing unit 22, and inputs the stored image data to the recording unit 21 under the control of the control unit 10.
The recording unit 21 is an electrophotographic printer, and converts the image data obtained from the CODEC 18 or the image based on the image data obtained from the image memory 20 into A3 portrait, B4 portrait, A4 portrait, B5 landscape, and hard copy. An optimum size is selected from recording paper of each size such as A5 width or an OHP (Over Head Projector) sheet and recorded.
[0028]
FIG. 2 is a block diagram illustrating a configuration example of the image processing unit 22 according to the present embodiment. The image processing unit 22 includes a register 30, a comparison circuit 31, a memory 32, a resolution conversion unit 33, and the like.
In the MFP 1 having the above-described configuration, the control unit 10 calculates the number of pixels included in one unit for thinning out one pixel based on the scaling ratio (reduction ratio) stored in the RAM 12. The acquired number of pixels is input to the image processing unit 22, and the image processing unit 22 stores the acquired number of pixels in the register 30.
[0029]
Specifically, for example, when performing a reduction process with a reduction ratio of 99%, the control unit 10 calculates 100 as the number of pixels included in one unit so as to thin out one pixel from 100 pixels, and Stores 100.
The image processing unit 22 sequentially stores each pixel data of the image data obtained from the CODEC 18 in the memory 32, and thins out the pixel data stored in the memory 32 based on the number stored in the register 30. It operates as specifying means for specifying the data value of the candidate pixel. When 100 is stored in the register 30, the image processing unit 22 determines, for each 100 pixels, the data value of one thinning-out candidate pixel for each pixel of the image data stored in the memory 32. To identify.
[0030]
Further, in the image processing unit 22, the comparison circuit 31 compares the data value of the pixel identified as the thinning candidate as described above with the data value of the pixel adjacent to the pixel in the main scanning direction, thereby performing the thinning. It operates as a judging means for judging whether or not the data value of a candidate pixel matches the data value of an adjacent pixel.
As a result of this comparison, when the data value of the pixel of the thinning candidate matches the data value of the adjacent pixel, the resolution conversion unit 33 operates as a thinning unit that thins out the data value of the specified pixel of the thinning candidate, The corresponding data values are thinned out and sequentially stored in the image memory 20.
[0031]
On the other hand, when the data of the pixel of the thinning candidate does not match the data value of the adjacent pixel (when none of the data values of two adjacent pixels on both sides in the main scanning direction match), the comparison circuit 31 sets the register 30 , The unit from the pixel of the thinning candidate to the pixel on the left side of the same line in the main scanning direction and similarly specified as the thinning candidate is defined as one unit. , The data values of two pixels adjacent to each other on both sides in the main scanning direction are sequentially compared, and the device operates as a detecting unit that detects adjacent pixels having the same data value.
That is, the detection unit detects whether or not there is a pixel in at least one of two pixels adjacent in the main scanning direction having the same data value in the detection range.
[0032]
When a pixel having the same data value and an adjacent pixel (a pixel having the same data value as an adjacent pixel) are detected as a result of the comparison by the comparison circuit 31, the resolution conversion unit 33 determines that a continuous pixel having the same data value is present. In order to thin out one of the pixel groups, corresponding data values are thinned out and sequentially stored in the image memory 20.
If the comparison result of the comparison circuit 31 indicates that no adjacent pixel having the same data value is detected in the one unit, the resolution conversion unit 33 determines the number of thinning candidates specified based on the number stored in the register 30. In order to thin out the pixels, the corresponding data values are thinned out and sequentially stored in the image memory 20.
[0033]
3A and 3B are diagrams for explaining a resolution conversion process by the image processing unit 22 according to the present embodiment. FIG. 3A shows a part of image data before resolution conversion, and FIG. Each part of the converted image data is shown.
In FIG. 3A, when the pixel at the position indicated by M1 in the figure is specified as a thinning candidate as described above, the image processing unit 22 causes the comparison circuit 31 to change the data value of the pixel M1 to the pixel M1. Is determined to be the same as the data value of both adjacent pixels. In the figure, since the data values are different on both sides, the image processing unit 22 sequentially shifts the pixel of interest one pixel at a time toward the left side of the pixel M1 in the main scanning direction while changing the data value of each adjacent pixel. When successive pixel groups (two pixels) having the same data value are detected by the sequential comparison circuit 31, the data value of a pixel adjacent to at least one of both sides in the main scanning direction is the same as the target pixel. In this case, one pixel (the pixel M2 in the figure) of the detected continuous pixel group is thinned out (see FIG. 3B).
[0034]
FIG. 3C shows a part of image data before resolution conversion in which white pixels and black pixels are alternately formed, and M1a and M1b in the figure denote pixels identified as thinning candidates, respectively. Is shown.
As shown in FIG. 3 (c), adjacent pixels having the same data value between the pixels M1a and M1b specified as the thinning candidates, that is, such a unit is defined as one unit. Is not detected, the image processing unit 22 prevents the bias in the position of the pixel to be thinned out by thinning out the pixel M1a specified as the thinning candidate by the resolution conversion unit 33, and reliably performs the resolution conversion process. Can do it.
[0035]
In the above-described embodiment, the resolution conversion processing (reduction processing) in the main scanning direction of an image has been described, but the present invention is also applicable to the resolution conversion processing in the sub-scanning direction. Further, when the above-described resolution conversion processing is performed on the pseudo halftone image, it is possible to prevent the generation of white or black vertical stripes.
Further, when the data value of the pixel specified as the thinning candidate based on the received reduction ratio is not the same as the data value of the adjacent pixel, the image processing unit 22 shifts the pixel value of the thinning candidate to the left in the main scanning direction from the pixel of the thinning candidate. To detect the presence of adjacent pixels having the same data value, but from the pixel of the thinning candidate to the right side in the main scanning direction, adjacent pixels having the same data value are configured. It may be configured to detect the presence of a pixel.
[0036]
【The invention's effect】
In the case of the first invention, the number of pixels included in each unit for thinning out one pixel is calculated based on the received reduction ratio, and the calculated number of pixels is defined as one unit, and the pixel to be thinned out is specified for each unit. Also, it is determined whether or not the data value of the specified pixel is the same as the data value of at least one pixel adjacent to the pixel. It is possible to perform reduction processing for preventing the occurrence of connection of pixels or black pixels and reducing deterioration of image quality.
[0037]
According to the second aspect, when the data value of a pixel specified to be thinned out is not the same as the data value of a pixel adjacent to the pixel, a plurality of data values adjacent to the specified pixel are identified from the vicinity of the specified pixel. By detecting one of the pixels and thinning out one of the detected pixels, it is possible to prevent the connection of white pixels or black pixels that may occur when the specified pixel is thinned out. Can reduce the deterioration of the image quality.
[0038]
In the case of the third invention, a plurality of adjacent pixels having the same data value are detected in each unit composed of the number of pixels calculated based on the received reduction ratio, so that the range of the positions of the pixels to be thinned is determined. This can prevent the bias of the positions of the pixels to be thinned out, and can reduce the load of the detection processing by preventing endless repetition of the above-described detection processing.
[0039]
According to the fourth aspect, as described above, when a plurality of adjacent pixels having the same data value cannot be detected, the pixel identified to be thinned is thinned out, so that the reduction process by the thinning process can be reliably performed. In addition to this, it is possible to prevent the deviation of the positions of the pixels to be thinned out.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a multifunction peripheral according to the present invention.
FIG. 2 is a block diagram illustrating a configuration example of an image processing unit according to the present embodiment.
FIG. 3 is a diagram for explaining resolution conversion processing by an image processing unit according to the present embodiment.
[Explanation of symbols]
1 MFP 10 control unit 22 image processing unit (specification means)
31 Comparison circuit (judgment means, detection means)
33 Resolution conversion unit (thinning means)

Claims (4)

From an image in which a plurality of pixels are arranged in a matrix, based on the received reduction ratio, one pixel is thinned out for each unit with the number of pixels corresponding to the reduction ratio as one unit, and the image is reduced in size. In the processing device,
Specifying means for specifying pixels to be thinned out for each unit;
Determining means for determining whether or not the data value of the pixel specified by the specifying means is the same as the data value of at least one pixel adjacent to the pixel;
An image processing apparatus comprising: a thinning unit that thins out the pixels specified by the specifying unit when the determining unit determines that they are the same. When the determination unit determines that the same is not the same, from the vicinity of the pixel specified by the specifying unit, a detection unit that detects a plurality of adjacent pixels having the same data value,
2. The image processing apparatus according to claim 1, wherein the thinning unit is configured to thin one of the pixels detected by the detecting unit. The image processing apparatus according to claim 2, wherein the detection unit is configured to detect a plurality of adjacent pixels having the same data value in each unit. The thinning means,
4. The image processing apparatus according to claim 2, wherein when the plurality of adjacent pixels having the same data value cannot be detected by the detecting unit, the pixels specified by the specifying unit are thinned out. apparatus.

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