JPH1032705A - Image data processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image data processor which can erase only an isolated picture element. SOLUTION: Based on the image data of a current line and the image data of past lines stored in a line memory 10, an isolate point correcting part 9 generates a prescribed two-dimensional matrix and based on that matrix and the image data of picture elements around any specified picture element concerning the image data of the specified picture element in the image data of the current line, when the specified picture element is a black picture element and all the surrounding picture elements are white picture elements, the specified picture element is judged as the isolated black picture element but when even on black picture element exists in the surrounding picture elements, it is judged the specified picture element is not the iscolated black picture element. Then, when the specified picture element is the isolated black picture element, the isolate point correcting part 9 forcedly converts the image data of the specified picture element to the image data of white picture elements and outputs the converted image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image data processing apparatus, and more particularly to an image data processing apparatus for converting image data including a multi-tone image into binary data.

[0002]

2. Description of the Related Art Generally, facsimile, copy, OCR
The image data processing device used in the above-described method converts an analog image signal input from a line sensor such as a CCD or a contact sensor into binary image data and outputs the binary image data. In facsimile, the converted binary image data is compressed using a codec to reduce the amount of data, and transmitted to a destination via a modem. In copying, the converted binary image data is output to a printer to create a document. In such an image data processing device,
In order to display a multi-tone image on a binary display system (such as a printer capable of printing only in black or white binary), an error diffusion process of adding an error generated by binarization to image data of peripheral pixels,
In order to output the image data to printers having different numbers of dots, various processes such as a pixel density conversion process for selectively extracting each image data and its average value are performed.

[0003]

By the way, in the image data input to the image data processing apparatus, the value when input and the value after the processing are rarely different in various processes. If correct conversion is not performed due to the influence of noise from a motor for feeding a document or an oscillation amplifier in such a process, an isolated point of a black pixel may occur in a white portion of the read document. Also, when a document with a dark background such as a newspaper is read, isolated points of black pixels may occur in the background. For this reason, the document output by the printer or the like becomes difficult to see. Further, when compressing the data amount by the codec, if there is an isolated point of a black pixel, it is not compressed as continuous white pixel data, so that the compression rate of the data amount is reduced.

As a method of removing the isolated point of the black pixel, when a pixel adjacent to the black pixel in the main scanning direction is a white pixel, the black pixel is forcibly changed to a white pixel to remove the isolated black pixel. An erasing method is conceivable. However, in this method, a thin line (for example, a line having a width of one pixel) in a direction different from the main scanning direction (for example, the sub-scanning direction) may be erased by mistake.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image data processing apparatus capable of erasing only isolated pixels.

[0006]

According to a first aspect of the present invention, multi-valued data obtained by quantization is obtained for each pixel from image data constituting one screen, which is continuous in units of one line, and is successively stored in two lines. An image data processing device which converts and outputs value data, binarizes input multi-value data based on a predetermined threshold value, and outputs the binary data as binary data. Based on a line memory storing at least one line of data, binary data read from the line memory, and binary data of a line next to the line corresponding to the binary data, binary data of a specific pixel. When a predetermined number of matrices composed of binary data of a plurality of pixels and its surroundings are generated, and only binary data of a specific pixel is different from binary data of other pixels in the matrix, And gist that a isolated point correcting unit that inverts the binary data of the pixel.

According to a second aspect of the present invention, there is provided the image data processing apparatus according to the first aspect, wherein the multi-valued data is pseudo-displayed with multi-gradation while performing error diffusion processing on the input multi-valued data. And a switch for selecting either binary data output from the binarization unit or binary data output from the halftone unit, further comprising:
The gist is that the isolated point correction unit is operated when the switch is selecting binary data of the binarization unit.

[0008] The invention according to claim 3 is the invention according to claim 1 or 2.
Wherein the isolated point correction unit is constituted by a plurality of flip-flop circuits, a shift register for transferring image data of a current line, and a plurality of flip-flop circuits, and an image of a past line is provided. A shift register for transferring data and image data to be transferred to the shift register are input, and a predetermined number of matrices are formed based on image data of a specific pixel and image data of pixels surrounding the specific pixel. A determination circuit for determining whether a specific pixel is an isolated black pixel based on a matrix, and a plurality of flip-flop circuits constituting a shift register for transferring image data of the specific pixel; And a gate circuit for inputting the result and forcibly changing the transferred image data to white pixel data. And summarized in that is.

According to a fourth aspect of the present invention, in the image data processing apparatus according to the third aspect, the isolated point correction section comprises:
A selection signal corresponding to the number of pixels to be determined is input, and based on the selection signal, one isolated pixel or n consecutive isolated n pixels (n = 2, 3, 4,...) Is detected. The gist is that a matrix is generated and it is determined whether or not a specific pixel is an isolated black pixel based on the matrix.

Therefore, according to the first aspect of the present invention,
The multi-valued data is input to the binarization unit, the multi-valued data is binarized based on a predetermined threshold, and output as binary data. The line memory stores at least one line of binary data. Value data is stored. Binary data read from the line memory and binary data of a line next to the line corresponding to the binary data are input to the isolated point correction unit, and binary data of a specific pixel and a plurality of pixels around the specific pixel are input. A predetermined number of matrices consisting of binary data of
When only the binary data of the specific pixel is different from the binary data of the other pixels in the matrix, the binary data of the specific pixel is inverted and output.

According to the second aspect of the present invention, multi-level data is input to the halftone section, and pseudo multi-level display is performed while performing error diffusion processing on the multi-level data. Value data is generated. When either the binary data output from the binarization unit or the binary data output from the halftone unit is selected by the switch and the switch selects the binary data of the binarization unit , The isolated point correction unit is operated.

According to the third aspect of the invention, the image data transferred to the shift register is input to the determination circuit, and the image data of the specific pixel and the image data of the pixels surrounding the specific pixel are input to the determination circuit. , A predetermined number of matrices are formed, and it is determined based on the matrices whether or not the specific pixel is an isolated black pixel. The gate circuit is provided between a plurality of flip-flop circuits constituting a shift register for transferring image data of a specific pixel, a determination result of the determination circuit is input, and the transferred image data is forcibly converted to white pixel data. Is changed to

According to the fourth aspect of the present invention, a selection signal corresponding to the number of pixels to be determined is input to the isolated point correction unit, and based on the selection signal, one isolated pixel or an isolated pixel is selected. A matrix for detecting n consecutive pixels is generated, and it is determined based on the matrix whether the specific pixel is an isolated black pixel.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic block circuit diagram of the image data processing device. The image data processing device 1 can be used for various applications such as facsimile. Image data processing device 1
Converts analog image signals from a CCD, a contact sensor, and the like into high-quality binary image data and outputs the binary image data. In the facsimile, the converted and output binary image data is compressed by an image codec (not shown) and then transmitted to a destination via a modem.

The image data processing apparatus 1 includes an analog section 2,
Distortion correction unit 3, pixel density conversion unit 4, gamma correction unit 5, filter unit 6, halftone unit 8, binarization unit 7, isolated point correction unit 9, memory 10, output control unit 11, control circuit 12, and , A register 13 and are integrated on one chip. The image data processing device 1 includes an image signal, for example,
An image signal obtained by reading a facsimile transmission original with a line sensor is input.

The line sensor divides the transmission original into a plurality of pixels in the main scanning direction, reads the density of each pixel, and outputs an image signal having a voltage corresponding to the density. The image signal input from the line sensor is input to the analog unit 2.
The image signal is an analog value, for example, a high voltage when the pixel is black, a low voltage when the pixel is white, and an intermediate voltage when the pixel is gray. The analog unit 2 includes an A / D converter having a predetermined number of bits (for example, 8 bits).
The image signal is quantized and converted into multi-value data of a plurality of gradations (256 gradations). The converted multi-value data has a value corresponding to the density of each pixel. Then, the converted multi-value data is output to the distortion correction unit 3.

The distortion correction unit 3 reads the distortion correction data stored in advance in a memory (not shown) and
The gradation correction is performed on the multi-value data of the line based on the distortion correction data, and the multi-value data of the correction result is output to the pixel density conversion unit 4. The distortion correction data (shading data) is data for numerically correcting distortion generated in the optical system.

The pixel density conversion unit 4 is provided for performing density conversion processing for converting the pixel density of each line on the data input from the distortion correction unit 3 using multi-value data. The pixel density conversion unit 4 calculates the average of a plurality of pixels adjacent in the main scanning direction of one line of image data read and input in the main scanning direction, and calculates the calculation result and the number of input pixels. The number of pixels is increased or decreased by selectively outputting the value data and the density in accordance with the conversion density. The pixel density conversion unit 4 outputs the converted multi-value data to the gamma correction unit 5.

The gamma correction section 5 reads gamma correction data stored in a memory (not shown) in advance, and performs gamma correction on the multi-value data input from the pixel density conversion section 4 based on the gamma correction data. Do. The gamma correction data is data for correcting a deviation between a photoelectric conversion characteristic of the line sensor and a change in light intensity that a person actually visually perceives. The gamma correction unit 5 outputs the multi-value data of the correction result to the filter unit 6.

The filter unit 6 is based on two lines of multi-value data stored in a memory (not shown) and one line of multi-value data input from the gamma correction unit 5.
, And outputs the filtered data to the halftone section 8 or the binarization section 7. This spatial filter performs filter processing such as edge enhancement on multi-valued data.

A threshold value is set in the binarization unit 7 in advance, and based on the threshold value, the input multi-value data is converted into binary data. The threshold value is set to, for example, an intermediate value between the all-white multi-value data and the all-black multi-value data. The binary data is, for example, “1” when the multi-valued data is larger than the threshold, and “0” when the multi-valued data is smaller than the threshold. When the binary data is “0”, that is, at the L level, the output document is white, and when the binary data is “1”, that is, at the H level, the document is black.

On the other hand, the halftone section 8 performs an error diffusion process on the input multi-valued data, and creates binary data representing a halftone in a pseudo manner. In the error diffusion processing, in order to express multi-value data as binary data, an error generated when binarizing multi-value data of a certain pixel is added to multi-value data of pixels around the pixel. It was done.

The binary data output from the binarizing section 7 and the halftone section 8 are output to the isolated point correcting section 9 via the switch SW. The switch SW is switched by a control circuit 12, which will be described later, according to an image area including the output binary data. The image area includes an area composed of characters and the like, an area composed of photographs and the like. In the character image area composed of white data and black data, by switching the switch SW to the binarizing unit 7, binary data with a clear edge can be obtained. On the other hand, in a photographic image area composed of halftone multivalued data, by switching the switch SW to the halftone portion 8, binary data capable of expressing shades in a pseudo manner is obtained.

The isolated point correction section 9 is provided to remove an isolated black pixel (isolated point) that did not exist when read by the line sensor. Isolated point correction unit 9
Is connected to a line memory 10. The line memory 10 stores image data for at least one past line. The isolated point correction unit 9 sequentially inputs the binary data of the pixels of the current line, sequentially reads out the binary data of the past line stored in the line memory 10, and based on each of the plurality of pixels of the current line and the past line. To generate a predetermined number of two-dimensional matrices.

The isolated point correcting section 9 stores the input image data of the current line in the line memory 10. The image data stored in the line memory 10 becomes the image data of the past line when the image data of the line next to the current line is input.

Based on the generated matrix, the isolated point correcting unit 9 compares the image data of the particular pixel of interest out of the image data of the current line with a plurality of image data of pixels around the specific pixel. It is determined whether or not the specific pixel is an isolated point. Specifically, when the specific pixel is a black pixel and all of the surrounding pixels are white pixels, the isolated point correction unit 9 determines that the specific pixel is an isolated point, and determines whether or not one of the peripheral pixels is an isolated point. If a black pixel exists, it is determined that the specific pixel is not an isolated point. When the specific pixel is an isolated point, the isolated point correction unit 9 forcibly converts the image data of the specific pixel into image data of white pixels, and outputs the converted image data (binary data).

By the way, in the image data of the photographic image area output from the halftone section 8, isolated black pixels are formed by error diffusion processing so as to display halftones in a pseudo manner. For this reason, when the isolated point correction unit 9 is operated on the image data of the photographic image area output from the halftone unit 8, the black pixels created for displaying the halftone are generated in the same manner as the unnecessary isolated points. It will be removed and the halftone will not be represented correctly. Therefore, the isolated point correction unit 9 operates only on the image data of the character image area output from the binarization unit 7 in accordance with the switching operation of the switch SW by the control circuit 12 described later.

With this configuration, since the isolated points are removed, the background of the output image becomes clear. When a black pixel exists around a specific pixel, for example, a line segment for one pixel in the sub-scanning direction or an arbitrary direction is not determined as an isolated point. As a result, only an isolated point is reliably erased without erroneously erasing a line segment for one pixel.

The output control unit 11 arranges the binary data input from the isolated point correction unit 9 in a format suitable for a codec and a modem (not shown), and outputs it to the outside. For example, in the case of facsimile, the binary data output to the outside is compressed by a codec according to a predetermined method. At this time, since the isolated points have been removed, the background portion is compressed as continuous white pixels, and the compression ratio is increased.

The control circuit 12 and the register 13 are
10 to 10 are provided. Register 13
Stores various data such as the pixel density to be converted, which is input from a controller for controlling the entire system such as a facsimile. The control circuit 12 outputs a control signal to each of the units 2 to 10 based on various data stored in the register 13, and each of the units 2 to 10 operates based on the control signal.

Next, the configuration of the isolated point correction section 9 will be described in detail.
As illustrated in FIG. 2, the isolated point correction unit 9 includes a plurality (two in this embodiment) of shift registers 21 and 22, a determination circuit 23, and gate circuits 24, 25 and 26. . Each of the shift registers 21 and 22 includes a plurality (five in this embodiment) of flip-flop circuits Fa1 to Fa5 and Fb1 to Fb5 connected in series. Each flip-flop circuit Fa1 to Fa5,
Clock signals CLK synchronized with the input timing of image data are input to Fb1 to Fb5, respectively. The first stage flip-flop circuit Fa1 of the shift register 21 sequentially receives the image data (binary data) of the pixels on the current line, and the first stage flip-flop circuit Fb1 of the shift register 22 reads the image data (binary data) from the line memory 10. The output image data of the past line is sequentially input.

The shift registers 21 and 22 sequentially transfer the image data based on the clock signal CLK, and hold the transferred image data. The output terminals of the flip-flop circuits Fa1 to Fa5 and Fb1 to Fb5 that constitute the shift registers 21 and 22 are connected to the determination circuit 23, and the held image data CR1 to CR5 of the current line and the image data PR1 to PR5 of the past line are stored. Output to the judgment circuit 23.

The judgment circuit 23 receives the input image data C
Based on R1 to CR5 and PR1 to PR5, a 5 × 2 two-dimensional matrix is generated as shown in FIG. Further, the selection signal SEL is input to the determination circuit 23.
The selection signal SEL is set and input according to the number of determination pixels for determining whether or not the pixel is an isolated point. In the present embodiment, the number of determination pixels is “1 pixel”, “2 pixels”,
“3 pixels” is set.

The judging circuit 23 pays attention to the specific number of judging pixels, and inputs the input image data CR1 to CR5, PR1.
From .PR5, a matrix of a predetermined number of sizes including a specific pixel and its surrounding pixels is generated. For example, FIG.
As shown in (a), when the determination pixel is “1 pixel”, the determination circuit 23 pays attention to the image data CR4 of one pixel, and the image data CR4 and the peripheral image data CR3, CR
5, a 3 × 2 one-pixel matrix including PR3 to PR5 is generated. Further, as shown in FIG. 4B, when the determination pixel is “two pixels”, the determination circuit 23 pays attention to the image data CR3 and CR4 of two pixels, and
3, CR4 and peripheral image data CR2, CR5, PR2
Generate a 4 × 2 two-pixel matrix consisting of .about.PR5. Further, as shown in FIG. 4C, when the determination pixel is “3 pixels”, the determination circuit 23 outputs the image data CR of 3 pixels.
Focusing on 2 to CR4, a 5 × 2 3-pixel matrix including the image data CR2 to CR4 and the peripheral image data CR1, CR5, PR1 to PR5 is generated.

Then, the determination circuit 23 determines whether the specific pixel is an isolated point based on the image data included in the generated matrix. Based on the determination result, the determination circuit 23 determines the inversion signals WC1 to WC1 of a predetermined level.
WC3 is output. For example, as shown in FIG. 5, when it is determined that the specific pixel is not an isolated point, L level inversion signals WC1 to WC3 are output, and when it is determined that the specific pixel is an isolated point, according to the number of determined pixels. As shown in FIG. 5, the inverted signals WC1 to WC3 are set to H level and output.

For example, when the number of determination pixels is “1 pixel”,
The determination circuit 23 determines whether or not a specific pixel is an isolated point based on the generated one-pixel matrix. If it is determined that one specific pixel is an isolated point, the determination circuit 23 outputs only the determination signal WC1 at the H level.

Similarly, when the number of pixels to be determined is "2 pixels", the determination circuit 23 determines whether or not two specific pixels are isolated points based on a two-pixel matrix. , The determination signals WC1 and WC2 are set to H level and output. When the number of pixels to be determined is “3 pixels”, the determination circuit 23 determines a specific 3 pixel based on a 3 pixel matrix.
It is determined whether or not the pixel is an isolated point. If the pixel is an isolated point, the determination signals WC1 to WC3 are output at the H level.

The judgment signal WC output from the judgment circuit 23
1 to WC3 are input to the gate circuits 24, 25, and 26, respectively. The gate circuits 24 to 26 are respectively inserted and connected between the second to fifth flip-flop circuits Fa2 to Fa5 of the shift register 21.
Each of the gate terminals 24 to 26 has an inverting input terminal, and the determination signal WC1 to WC3 is input to the inverting input terminal.

Each of the gate circuits 24 to 26 outputs a judgment signal WC
When 1 to WC3 are each at the L level, the input image data CR2 to CR4 are output as they are to the next-stage flip-flop circuits Fa3 to Fa5, respectively. On the other hand, when the determination signals WC1 to WC3 are at the H level, the gate circuits 24 to 26 output the input image data CR2 to CR
Regardless of R4, it outputs an L-level signal to the next-stage flip-flop circuits Fa3 to Fa5.

Each of the determination signals WC1 to WC3 is at the L level when the specific pixel is an isolated point. When the image data is at the H level, black is displayed on the document, and when the image data is at the L level, white is displayed on the document. Therefore, when the specific pixel is an isolated point, each of the gate circuits 24 to 26 forcibly outputs image data corresponding to white to the flip-flop circuits Fa3 to Fa5 at the next stage.

That is, the isolated black pixel in the character image area is
It is converted to white pixels and output. Also, each judgment signal WC
1 to WC3 are set to L level and output when the specific pixel is an isolated point according to the number of determination pixels. Therefore, it is determined whether or not one to three specific pixels are isolated points. If the isolated pixels are isolated points, they are converted to white pixels and erased.

As described above, the present embodiment has the following advantages. (1) The isolated point correction unit 9 sequentially inputs the binary data of the pixels of the current line, sequentially reads out the binary data of the past line stored in the line memory 10, and stores a plurality of binary data of the current line and the past line. A predetermined number of two-dimensional matrices are generated based on the pixels. Then, based on the generated matrix, the isolated point correction unit 9 compares the image data of the specific pixel of interest out of the image data of the current line with the image data of pixels around the specific pixel.
It is determined whether or not the specific pixel is an isolated point. Specifically, when the specific pixel is a black pixel and all peripheral pixels are white pixels, the isolated point correction unit 9 determines that the specific pixel is an isolated point, and at least one black pixel is included in the peripheral pixels. If exists,
It is determined that the specific pixel is not an isolated point. When the specific pixel is an isolated point, the isolated point correction unit 9 forcibly converts the image data of the specific pixel into image data of white pixels and outputs the converted image data (binary data). did. When a black pixel exists around a specific pixel, for example,
A line segment for one pixel in the sub-scanning direction or any direction is not determined as an isolated point. As a result, isolated points can be reliably removed without erroneously erasing a line segment for one pixel.

The present invention may be carried out as follows in addition to the above embodiment. (1) In the above embodiment, the isolated point correction unit 9 generates a three-pixel matrix from a one-pixel matrix based on the selection signal SEL, detects isolated black pixels from one to three pixels, and generates a white pixel. Although the pixel is converted to a pixel, the present invention may be implemented as a configuration for generating only one pixel matrix or for generating one pixel matrix and two pixel matrix.

Further, a circuit may be configured so as to generate a four-pixel matrix or more. At this time, the shift register 2 is set in accordance with the size of the matrix to be generated.
It goes without saying that the number of flip-flop circuits constituting the first and second circuits 22 is appropriately changed.

(2) In the above embodiment, the shift register 21 for transferring the image data of the current line and the shift register 22 for transferring the image data of the past line are provided to generate a maximum 5 × 2 matrix. Although the isolated point is determined by using the above method, the isolated point may be determined by providing a matrix of 3 or more shift registers and generating a 5 × n (n is the number of shift registers) matrix.

(3) In the above embodiment, an isolated point is detected and converted into a white pixel. However, if the background of the character image area is black, the isolated white pixel is detected as an isolated point. , May be implemented as a configuration for converting to black pixels. Further, a circuit that converts an isolated black pixel into a white pixel and a circuit that converts an isolated white pixel into a black pixel may be provided, and one of the circuits may be selected based on the state of an image. .

[0047]

As described in detail above, according to the present invention, it is possible to provide an image data processing apparatus capable of erasing only isolated pixels.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image data processing apparatus according to an embodiment.

FIG. 2 is a circuit diagram of an isolated point correction unit.

FIG. 3 is an explanatory view showing a generated matrix.

FIGS. 4A, 4B, and 4C are explanatory diagrams showing matrices to be generated.

FIG. 5 is an explanatory diagram showing a state of a determination signal output from a determination circuit.

[Explanation of symbols]

Reference Signs List 7 binarization section 8 halftone section 9 isolated point correction section 10 line memory 21, 22 shift register 23 determination circuit 24 to 26 gate circuit Fa1 to Fa5, Fb1 to Fb5 flip-flop circuit SEL selection signal SW switch

Claims (4)

[Claims] 1. An image data processing device which takes in multi-value data obtained by quantization from image data constituting one screen, which is continuous in units of one line, and converts the data into binary data in sequence and outputs the binary data. A binarizing unit (7) for binarizing input multi-valued data based on a predetermined threshold value and outputting the same as binary data; and a line memory for storing at least one line of the binary data. (10), based on the binary data read from the line memory (10) and the binary data of the line next to the line corresponding to the binary data, the binary data of the specific pixel and its surroundings A predetermined number of matrices composed of binary data of a plurality of pixels are generated. When only the binary data of a specific pixel is different from the binary data of other pixels in the matrix, the binary data of the specific pixel is generated. An image data processing apparatus comprising: an isolated point correction unit (9) for inverting and outputting inverted data. 2. An image data processing apparatus according to claim 1, wherein the halftone section generates binary data for pseudo-displaying multiple gradations while performing error diffusion processing on the input multivalued data. 8) and a switch (SW) for selecting either the binary data output from the binarization unit (7) or the binary data output from the halftone unit (8), An image data processing apparatus wherein the isolated point correction section (9) is operated when the switch (SW) is selecting binary data of the binarization section (7). 3. The image data processing device according to claim 1, wherein the isolated point correction unit is configured by a plurality of flip-flop circuits and transfers image data of a current line. Shift register (21), a plurality of flip-flop circuits (Fb1 to Fb5), and a shift register (22) for transferring image data of a past line; and an image transferred to the shift registers (21, 22). Data is input, a predetermined number of matrices are formed based on image data of a specific pixel and image data of pixels surrounding the specific pixel, and it is determined whether the specific pixel is an isolated black pixel based on the matrix. And a plurality of flip-flop circuits constituting a shift register (21) for transferring the image data of the specific pixel. (Fa
2 to Fa5), and a gate circuit (24 to 26) for inputting the judgment result of the judgment circuit and forcibly changing the transferred image data to white pixel data. . 4. The image data processing device according to claim 3, wherein the isolated point correction unit (9) inputs a selection signal (SEL) corresponding to the number of pixels to be determined, and outputs the selection signal (SEL) to the selection signal (SEL). One isolated pixel or n consecutive isolated pixels (n = 2, 3, 4,
..) Is generated, and an image data processing apparatus is configured to determine whether a specific pixel is an isolated black pixel based on the matrix.