JP2874592B2 - Image processing device for distinguishing text / photo / dot area - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for determining an image area in which characters, photographs, and halftone images are mixed, and more particularly to an improvement in a technique for accurately determining whether an image is a character image or another image.

[0002]

2. Description of the Related Art Generally, an image processing apparatus such as a facsimile apparatus or a photograph transmission apparatus scans a document in which a photographic image, a character image, and a halftone (dot) image are mixed, and generates an image signal in accordance with the density of pixels. Then, it is converted into a binary signal of 1, 0 and then encoded. However, in the process of converting to a binary signal, 1,1,
When the signal is converted into a binary signal of 0, when encoding the signal after the binary conversion, the coding efficiency is deteriorated and the reproducibility of the image is reduced. Therefore, the conventional image processing device solves such a problem by determining the type of each image and generating a binary signal by a conversion method suitable for the image.

With respect to image processing techniques for image type determination, US Pat. No. 4,547,811 discloses a method for distinguishing between binary images and images having gray levels, such as photographs. The method is to divide a document into blocks each having m × n pixels, and to set a maximum density level Lmax and a minimum density level L among image signal levels in the block.
min is determined and compared with the reference value P to make the next determination.

I) When Lmax−Lmin> P, the image of the block is a character image.

Ii) When Lmax−Lmin ≦ P, the image of the block is a photographic image.

Although the above method is effective for distinguishing between a photographic image and a character image in which the image density level changes continuously, the distinction between a halftone dot image as a stippled image and a character image is not sufficient.

As another image processing technique, utilizing the property that the differential amount of the boundary portion, that is, the density difference is large in a character image, a character image is used when the differential amount is large, and a character image is used otherwise. There is a way to be not. However, since the differential amount is large not only at the character but also at the boundary between the halftone dots of the halftone image, the probability that the halftone image is determined to be a character image is high.

When a halftone image is determined to be a character image and the image signal is converted into a binary signal by a binary conversion circuit corresponding to the character image, the reproducibility of the halftone image deteriorates, and the reproduced image becomes poor. It becomes dark and hard to see.

On the other hand, the applicant's specification (Japanese Patent Application No. 5-1)
No. 48176) proposes an image processing apparatus capable of accurately determining the area of a halftone image and a character image.

Generally, an image centered on a line drawing such as a character image is
Not only is the boundary between the low density and the high density clear, but also the length of the boundary is formed of continuous edges that continue at least two pixels in the same direction. On the other hand, an image formed of a stippled image such as a halftone dot image has an edge, but there are few images formed of a continuous edge continuing by two or more pixels in the same direction. The image processing apparatus described in the above specification discriminates a halftone image from a character image by detecting the continuous edge.
More specifically, the continuous edge detection circuit is configured to determine, based on an image signal corresponding to the density of pixels of an image, a continuous edge having a boundary having a large density difference of two or more pixels from image signals of pixels in the main scanning direction and the sub-scanning direction. Is detected. The first detection signal is generated when the continuous edge detection circuit detects a continuous edge from the image signal of the pixel in the main scanning direction, and the second detection signal is generated when the continuous edge is detected from the image signal of the pixel in the sub-scanning direction. Occurs. By generating at least one of the first detection signal and the second detection signal, the image signal is converted into a binary signal as a character image. When neither the first detection signal nor the second detection signal is generated, the image signal is converted into a binary signal as a halftone image by a binary conversion different from that of the first conversion circuit.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus and an image processing method which use a method for detecting continuous edges to further improve the accuracy of distinguishing a character image from a halftone dot or a photographic image. An object of the present invention is to provide a method for separating regions.

[0012]

According to the present invention, there is provided an image processing apparatus comprising: a pixel extracting circuit for extracting an image signal in a matrix area formed based on an image signal corresponding to the degree of farming of a pixel of an image; A first area discriminating circuit for discriminating whether an image in the matrix area is a photograph area or a text area, a second area discriminating circuit for discriminating whether an image in the matrix area is a halftone area, and first and second areas. And a third area discriminating circuit that uses the discrimination result of the area discriminating circuit.

The first area determination circuit determines whether the matrix area is a character area or a photograph area based on the maximum value and the minimum value of the image signal in the matrix area. The second area discriminating circuit detects a continuous edge in which a boundary portion having a large density difference continues for two or more pixels from the image signals of the pixels in the main scanning direction and the sub-scanning direction in the matrix area. When a continuous edge is detected in at least one of the main scanning direction and the sub-scanning direction, the second area conversion circuit determines the matrix area as an area other than the character area. Judge as a character area. The third area determination circuit detects a determination result of a peripheral area of the matrix area based on a determination result of the first and second area determination circuits, and determines whether the matrix area is a character area or other based on the determination result of the peripheral area. Area is determined.

More specifically, the third area discriminating circuit includes a signal indicating the result of the photograph area discriminating from the first area discriminating circuit, and a signal indicating the result of discriminating the characters and halftone dots from the second area discriminating circuit. 1. A second matrix is formed based on the first and second signals, and a third signal representing a character area and a fourth signal representing an area other than the character area according to a signal pattern in the second matrix area. Each generates a signal.

According to the present invention, not only the determination of a photographic area in a matrix area but also the determination result of a halftone dot area by continuous edge detection is used to determine a character area from the determination result around the matrix area. Accuracy of discrimination between the region and the other region is improved. Note that the image signals in the matrix area used in the first area discriminating circuit and the image signals in the matrix area used in the second area discriminating circuit need not all match. However, the image signal of the pixel of interest is commonly used.

According to the present invention, two binary conversions are performed by the outputs of the first and third region discriminating circuits. First
The binary conversion circuit converts the image signal extracted by the pixel extraction circuit into a binary signal according to the determination of the character area by the third area determination circuit. Further, the second binary conversion circuit may be configured to determine a photographic area by the first area determination circuit, or
The image signal extracted by the pixel extraction circuit is converted into a binary signal by a binary conversion different from that of the first binary conversion circuit based on the determination of the area other than the character area by the third determination means.
Therefore, optimal binary conversion according to the image area is performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, an image processing apparatus according to an embodiment of the present invention detects an image signal generating circuit 1 for generating an image signal, a line memory 2, and an image area, and determines whether the image area is a photographic area or a character candidate. A photographic image discriminating circuit 3 for determining whether the area
A dot image discriminating circuit 6 for judging whether or not the image area is a dot area, and a matrix is constructed based on the outputs of the photograph image discriminating circuit 3 and the dot image discriminating circuit 6 to further determine whether the image is a dot area or a character area , A first binarization circuit 8 corresponding to binarization of a character area, and binarization by an error diffusion method for an image determined to be a halftone dot or a photographic area. And a timing control circuit 11.

An image signal generating circuit 1 scans an original with an image sensor to generate an image signal corresponding to the pixel density, converts the image signal into a digital signal, and generates a digital multi-valued image signal (hereinafter referred to as an image signal). ) Is output. For example, 25
When an image signal of 6 gradations is generated, the image signal 10 is 8 bi
This is the signal of t. The size of one pixel is 0.125 mm /
It is a dot.

The line memory 2 stores the image signals 10 for one scanning line, and outputs the stored image signals in the order of input when the capacity becomes full. This line memory can be replaced with a shift register. Writing / reading of line memory 2 (or signal transfer of shift register)
Is controlled by the timing control circuit 11.

Image signals from the line memory 2 and the image signal generating circuit 1 are supplied to a photographic image discriminating circuit 3. The photo image discriminating circuit 3 includes a 2 × 2 matrix (first
Is determined, and it is determined whether the matrix is a photograph area or a character candidate area. The photo image discrimination circuit 3
It has a pixel extraction circuit 4 and an area determination circuit 5.

The pixel extraction circuit 4 continuously generates a 2 × 2 square matrix composed of a target pixel to be binary-converted and three reference pixels adjacent thereto based on the image signal 10 and the image signal from the line memory 2. Extract and temporarily store. FIG.
3 shows a matrix of pixels extracted by a pixel extraction circuit 4. p
(I−1, j−1) and p (i−1, j) are pixels one line before from the line memory 2 or their image signals,
(I, j-1) and p (i, j) are pixels of the image signal 10 or the image signal thereof. The pixel of interest is the newest pixel p (i, j) in the matrix, and the other three pixels are reference pixels. Here, i is the row number in the main scanning direction, j
Represents the number of the column in the sub-scanning direction. Reading and writing of an image signal in the pixel extraction circuit 4 are controlled by the timing control circuit 11.

The area judging circuit 5 detects the image signal of the matrix shown in FIG. 2 extracted by the pixel extracting circuit 4, and detects the maximum value pMAX and the minimum value pMI of the density of the image signal in the matrix.
The difference from N is calculated. Further, the area determination circuit 5 compares the difference with the density threshold value Th, and calculates
It is determined whether the matrix in FIG. 2 is a photograph area or a character candidate area. pMAX-pMIN <Th
(1) The photographic area has a small change in density because it is halftone, whereas the character area has a large change in density because it is a black and white image.
Therefore, when the formula (1) is satisfied, the area determination circuit 5 generates a determination output Ai, j = 1 representing a photograph area. If Expression (1) is not satisfied, the area determination circuit 5 generates a determination output Ai, j = 0 representing the character candidate area. Judgment output A
i and j are a halftone image discriminating circuit 6 and a matrix discriminating circuit 7
And the second binarization circuit 9.

If Ai, j = 1, the photograph image discriminating circuit 3
In the 2 × 2 matrix determined to be a photograph area, the image signal of the target pixel is binarized by the second binarization circuit 9.
On the other hand, when Ai, j = 0, the second binarization circuit 9 determines the binarization of the image signal of the pixel of interest according to the output of the matrix determination circuit 7. The 2 × 2 matrix determined as a character candidate area by the photo image determination circuit 3 may be not only a normal character area but also a halftone area. In the halftone dot area, equation (1)
Is often not satisfied. Therefore, in the embodiment of the present invention, when Ai, j = 0, the character area is not immediately determined, and
First, a character area or a halftone area is identified.

The halftone image discriminating circuit 6 detects a continuous edge at the boundary between black and white pixels in the main scanning direction and the sub-scanning direction in the 2 × 2 matrix stored in the pixel extracting circuit 4.
Generally, in the case of a halftone image, there is a property that a continuous edge is hard to be detected, and the halftone image discrimination circuit 6 utilizes this property. A continuous edge is detected from any of the four density gradient patterns (a) to (d) shown in FIG. The arrow in FIG. 3 indicates the direction in which a black pixel changes to a white pixel. The halftone dot image discriminating circuit 6 detects each density gradient pattern by the following calculation.

P (i−1, j−1) −p (i−1, j) ≧ Thx (2) and p (i, j−1) −p (i, j) ≧ Thx (3) or p (I-1, j-1) -p (i-1, j) ≤-Thx (4) and p (i, j-1) -p (i, j) ≤-Thx (5) or p (i −1, j−1) −p (i, j−1) ≧ Thy (6) and p (i−1, j) −p (i, j) ≧ Thy (7) or p (i−1, j) −1) −p (i, j−1) ≦ −Thy (8) and p (i−1, j) −p (i, j) ≦ −Thy (9) Conditional expression (2) and (3) Assuming that Equation 1, Equations (4) and (5) are Condition 2, Equations (6) and (7) are Condition 3, and Equations (8) and (9) are Condition 4, the conditions 1 to 4 are respectively the density of FIG. This corresponds to the inclination patterns (a) to (d). Thx, Thy
Are thresholds for determining the density gradient in the main scanning and sub scanning directions, respectively.

When at least one of the conditions 1 to 4 is satisfied, the halftone image discriminating circuit 6 determines the 2 × 2 matrix area in FIG. 2 as a character area, and determines the result Bi, j = Generates 0. If neither condition is satisfied, the halftone image discrimination circuit 6 determines that the image is a halftone dot region, and generates a determination result Bi, j = 1 as a second signal.

The matrix judgment circuit 7 detects the judgment result of the peripheral area of the 2 × 2 matrix of FIG. 2 based on the judgment results of the photograph image area judgment circuit 3 and the halftone image judgment circuit 6,
From the determination result of the surrounding area, it is determined whether the matrix area is a character area or another area.

More specifically, the matrix determination circuit 7 determines the determination results Bi, j from the halftone image determination circuit 6 and the determination results Ai,
j = 1 is sequentially stored, and from the stored determination results, FIG.
Is extracted. In FIG. 4, Ai, j
And only data relating to Bi, j are shown. Second in FIG.
Is the determination result B from the halftone image determination circuit 6.
i, j and the past four determination results Bi-1, j-1, Bi
-1, j, Bi-1, j + 1, Bi, j-1.
The number of past determination results in the second matrix is not limited to four, and may be more than four.

When the character image candidate area is determined by the photo image determination circuit 3 and Ai, j = 0, the matrix determination circuit 7 stores the determination result Bi, j. And that B
When the determination result in the matrix of FIG. 4 including i and j includes at least one 0, the character candidate area of the matrix of FIG. 2 is finally determined to be a character area, and the determination result Ci, j is output as a third signal. = 0 is generated. When Ai, j = 0 and all the determination results in the matrix of FIG. 4 including Bi, j are 1, the matrix determination circuit 7 finally determines the character candidate region as a halftone dot region, A judgment result Ci, j = 1 is generated as a signal.

On the other hand, if the photographic area is determined by the photographic image discriminating circuit 3 and Ai, j = 1, 1 data or Ai, j data (= 1) is stored in the matrix of FIG. In this case, the matrix determination circuit 7 determines the determination result Ci, j = 1 regardless of the content of the second matrix.
Occurs.

The matrix judgment circuit 7 increases the accuracy of the judgment result in the halftone dot image judgment circuit 6 and enables stable area judgment.

If Ci, j = 0, the first binarizing circuit 8
, Binarizes the image signal p (i, j) of the pixel of interest by a binary conversion adapted to the character image, and when Ci, j = 1, the second
The binarization circuit 9 binarizes the image signal p (i, j) of the target pixel by an error diffusion method. Image signal p to each binarization circuit
For (i, j), an image signal extracted and stored by the pixel extraction circuit 4 is used.

The pixel extracting circuit 4 needs to hold a 2 × 2 matrix while the area determining circuit 5 is operating and the halftone image determining circuit 6 is operating. There is no need to hold the matrix while the binarization circuits 8, 9 are operating. In this case, the target pixel p (i,
A register for reading and storing only j) from the pixel extraction circuit 4 may be provided, and the output of the register may be supplied as an image signal to each binarization circuit.

In the above image processing circuit, the photographic image discriminating circuit 3, the halftone image discriminating circuit 6, and the matrix discriminating circuit 7 can be constituted by computer circuits using a CPU, respectively. It is also possible to configure a circuit with.

FIG. 5 is a detailed circuit diagram showing the area determining circuit 5 of the photographic image determining circuit 3 of FIG. In the figure, a maximum value detection circuit 51 and a minimum value detection circuit 52
Matrix image signal p (i-1, j-
1), p (i-1, j), p (i, j-1), p (i,
The maximum value pMAX and the minimum value pMIN of j) are detected. The subtraction circuit 53 subtracts the maximum value pMAX by the minimum value pMIN. The comparison circuit 54 compares the subtraction value with the threshold value Th and determines whether Expression (1) holds. Comparison circuit 54
Generates the first output Ai, j described above.

FIG. 6 is a circuit diagram showing the halftone image discriminating circuit 6 of FIG. In the figure, four image signals from a pixel extraction circuit 4 are supplied to a main scanning direction edge detection circuit 62 and a sub scanning direction edge detection circuit 63, respectively.

The main scanning direction edge detection circuit 62 is 2 × 2
The difference between the image signals of adjacent pixels is detected using two vectors (patterns (a) and (b) in FIG. 3) in the main scanning direction of the matrix, and the absolute value of the two detected difference signals is used as a determination threshold Th.
If it is larger than x, it is determined that there is a continuous edge. In this case, the condition 1 or 2 of the above equations (2) to (5) is satisfied, and the output 0 is generated. When the conditions 1 and 2 are not satisfied, the main scanning direction edge detection circuit 62 generates an output 1. The sub-scanning direction edge detection circuit 63 detects a difference between image signals of adjacent pixels using two vectors (patterns (c) and (d) in FIG. 3) in the sub-scanning direction of a 2 × 2 matrix, and If the absolute value of the difference signal is larger than the determination threshold Thy, it is determined that there is a continuous edge. In this case, the condition 3 or 4 of the above equations (6) to (9) is satisfied,
Generates output 0. When the conditions 3 and 4 are not satisfied, the sub-scanning direction edge detection circuit 63 generates the output 1. The AND gate 64 is connected to the edge detection circuit 6 in the main scanning direction.
2 and the output of the sub-scanning direction edge detection circuit 63,
The judgment result Bi, j is output.

FIG. 7 is a detailed circuit diagram of the main scanning direction edge detection circuit 62. In the figure, a subtraction circuit 611 is supplied with image signals p (i-1, j-1) and p (i-1, j), performs subtraction on the left side of the above equation (2), and outputs a difference signal. Is output. The subtraction circuit 612 outputs the image signal p (i, j-1) and p
(I, j) is supplied, the left side of Expression (3) is subtracted, and a difference signal is output. The difference signal from the subtraction circuit 611 is supplied to comparators 614 and 615, and the difference signal from the subtraction circuit 612 is supplied to comparators 616 and 617.

The reference value generation circuit 610 generates a reference value Thx, and the reference value Thx is supplied to comparators 615 and 617. The sign inversion circuit 613 inverts the sign of the reference value Thx, and the reference value -Thx is compared with the comparators 614 and 6.
16. Therefore, the comparators 615 and 617 compare the right side and the left side of the above-described equations (2) and (3), respectively, and if the equations (2) and (3) are respectively satisfied, the output Y becomes 1; become. Further, the comparators 614 and 616 compare the right and left sides of the above equations (4) and (5), respectively, and if the equations (4) and (5) are respectively satisfied, the output Y becomes 1; Become.

The NAND gate 619 is connected to the comparator 6
The outputs of 15 and 617 are input, and 0 is output if the equations (2) and (3) are simultaneously satisfied. NAND gate 618
The outputs of the comparators 614 and 616 are input, and equation (4)
If (5) is satisfied at the same time, 0 is output. AND gate 620 outputs a first detection signal of 0 when at least one of the outputs of NAND gates 618 and 619 is 0.

Therefore, when the edge detection direction is the main scanning direction shown in the patterns (a) and (b) of FIG. 3, if a continuous edge is detected in any one of the patterns, AND
The first detection signal from gate 620 goes to 0 and goes to 1 if no continuous edge is detected.

FIG. 8 is a detailed circuit diagram of the edge detection circuit 63 in the sub-scanning direction. The sub-scanning direction edge detection circuit 63 has the same circuit configuration as the main scanning direction edge detection circuit 62.
The image signals p (i−1, j−1) and p (i, j−1) are supplied to a subtraction circuit 631, and the image signals p (i−1, j) and p (i−1, j)
(I, j) is supplied to the subtraction circuit 632. Thereafter, the reference value generation circuit 630, the sign inversion circuit 633, the comparators 634, 635, 636, 637, and the NAND gate 6
The operations of 38, 639 and AND gate 640 are the same as the operations of the corresponding circuits of main scanning direction edge detection circuit 62.

Therefore, when the edge detection direction is the sub-scanning direction shown in patterns (c) and (d) of FIG. 3, if a continuous edge is detected in any one of the patterns, the second detection signal is set to 0. And becomes 1 if no continuous edge is detected.

FIG. 9 is a circuit diagram showing the matrix judgment circuit 7 of FIG. In the figure, a register 71 sequentially stores the determination result from the halftone image determination circuit 6 and Ai, j = 1. The signal of Ai, j = 0 when the photographic area is determined is not stored. The register 71 stores the determination results for two lines, and sequentially shifts to the left in the figure by the shift pulse from the shift control circuit 72. The shift control circuit 72 outputs a shift pulse in synchronization with a control signal from the timing control circuit 11. The AND gate circuit 73 outputs the determination results Bi-1, j-1, Bi-1, j, Bi- stored in the five storage bits in the hatched portion of FIG.
1, j + 1, Bi, j-1 and Bi, j as inputs,
The output is supplied to the OR gate circuit 73. The OR gate circuit 74 generates a third signal Ci, j from Ai, j and the output of the AND gate circuit 72. When Ai, j = 1, or when all five determination results supplied to the AND gate circuit 73 are 1, Ci, j = 1, and FIG.
Is determined as a photograph and a halftone dot area, and Ai, j =
If 0 and at least one of the five determination results is 0,
Ci, j = 0, and the matrix of FIG. 2 is finally determined to be a character area.

If Ci, j = 0, the first binarizing circuit 8
, Binarizes the image signal p (i, j) of the pixel of interest by a binary conversion adapted to the character image, and sets Ai, j = 1 or Ci, j
If j = 1, the second binarization circuit 9 binarizes the image signal p (i, j) of the target pixel by an error diffusion method. In practice, it is desirable that one of the outputs of the first and second binarization circuits 8 and 9 is selected by the selection circuit shown in FIG.

In FIG. 10, the selection circuit 10 has a first and a second output Ai, j from the photographic image discrimination circuit 3 and a third output Ci, j from the matrix judgment circuit 7, and the first and second outputs Ai, j. One of the outputs of the binarization circuits 8 and 9 is selected. That is, when Ci, j = 0, the output of the first binarizing circuit 8 is selected, and when Ai, j = 1 or Ci, j = 1, the selecting circuit 10 selects the second binarizing circuit 9. Select the output of

The image processing apparatus according to the present invention is not limited to the embodiment described above. For example, the pixel extraction circuit 4 may be separated from the photo image determination circuit 3. Further, the pixel extraction circuit 4 extracts a 2 × 2 matrix image signal, but may extract a matrix of other size. In this case, it is not necessary for the halftone image discrimination circuit 6 to perform the area judgment using all the image signals used in the area judgment circuit 5 of the photo image judgment circuit 3. That is, the area determination circuit 5
For example, a 3 × 2 matrix may be used, and the halftone dot discrimination circuit 6 may use a 2 × 2 matrix including the pixel of interest in the 3 × 2 matrix.

In the image processing apparatus shown in FIG. 1, the area determining circuit 5 and the halftone image determining circuit 6 of the photographic image determining circuit 3 operate in parallel. 2 × 2 determined as a character candidate area by the image area determination circuit 3
The region determination processing may be performed only on the matrix.

[0050]

As described in detail above, according to the present invention,
The first area determination circuit determines whether the extracted matrix area is a photograph area or a character candidate area, and determines whether the second area determination circuit is a halftone area or a character area based on an image signal in the matrix area. And the third area determination circuit finally determines whether the area is a character area or a halftone area from the determination results of the first area determination circuit and the second area determination circuit. There is an effect that the accuracy of the determination is high.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a matrix extracted by a pixel extraction circuit.

FIG. 3 is a diagram showing a density gradient pattern for detecting a continuous edge.

FIG. 4 is a diagram illustrating a matrix configured by a matrix determination circuit.

FIG. 5 is a circuit diagram showing an area determination circuit used in the embodiment of the present invention.

FIG. 6 is a circuit diagram showing a halftone image discrimination circuit used in the embodiment of the present invention.

FIG. 7 is a detailed circuit diagram showing a main scanning direction edge detection circuit of the halftone image discrimination circuit of FIG. 6;

8 is a detailed circuit diagram showing a sub-scanning direction edge detection circuit of the halftone image discrimination circuit of FIG. 6;

FIG. 9 is a circuit diagram showing a matrix determination circuit used in an embodiment of the present invention.

FIG. 10 is a circuit diagram showing a selection circuit used in an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image signal generating circuit 2 line memory 3 photographic image discriminating circuit 6 halftone dot discriminating circuit 7 matrix discriminating circuit 8 first binarizing circuit 9 second binarizing circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-356869 (JP, A) JP-A-63-205238 (JP, A) JP-A-3-1722843 (JP, A) JP-A-5-205 22588 (JP, A) JP-A-5-344330 (JP, A) JP-A-1-227576 (JP, A) JP-A-4-336874 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (10)

(57) [Claims] 1. A pixel extracting means for extracting an image signal in a matrix area formed on the basis of an image signal corresponding to the density of pixels of an image, and based on a maximum value and a minimum value of the image signal in the matrix area. A first area determining means for determining whether the matrix area is a text area or a photograph area; and a boundary area having a large difference in agricultural level from image signals of pixels in the main scanning direction and the sub-scanning direction in the matrix area. Detecting a continuous edge that continues for more than a pixel, determining the matrix area as a region other than a character region when the continuous edge is detected in at least one of the main scanning direction and the sub-scanning direction, and not detecting the continuous edge A second area determination unit that determines the matrix area as a character area; and a determination result of the first and second area determination circuits.
Detecting the determination result of the peripheral area of the matrix area,
A third area determination circuit that determines whether the matrix area is a character area or another area based on the determination result of the peripheral area. 2. The image processing apparatus according to claim 1, wherein the first area determination unit detects a difference between a maximum value and a minimum value of an image signal in the matrix area, and the first area determination unit determines whether the difference is larger than a reference value. The image processing apparatus according to claim 1, further comprising: a determination unit configured to determine whether the matrix area is a photograph area or a character area. 3. The first area detection means, wherein the second area determination means detects the continuous edge from an image signal of a pixel in the main scanning direction in the matrix area, and generates a first detection signal; A second detection unit that detects the continuous edge from an image signal of a pixel in the sub-scanning direction in the matrix area and generates a second detection signal; and at least one of the first and second detection signals is generated. And determining means for determining the matrix area as a character area when both of the first and second detection signals are not generated, and determining the matrix area as a character area when neither the first nor the second detection signal is generated. Image processing device. 4. The image processing apparatus according to claim 1, wherein said matrix area is a 2 × 2 matrix. 5. The area determination matrix comprising a determination result of a peripheral area of the matrix area based on a determination result of the first and second area determination circuits. 2. The image processing apparatus according to claim 1, wherein it is determined whether the matrix area is a character area or another area based on a signal pattern of a determination matrix. 6. The third area determination means, when a character area is determined by the first area determination means, based on a signal pattern of the area determination matrix, the matrix area is a character area or another area. 6. The image processing apparatus according to claim 5, wherein it is determined whether the area is an area, and if the first area determination unit determines a photograph area, the matrix area is not determined as a character area. 7. A pixel extracting means for extracting an image signal in a matrix area formed on the basis of an image signal corresponding to the density of pixels of an image, and based on a maximum value and a minimum value of the image signal in the matrix area. A first area determining means for determining whether the matrix area is a text area or a photographic area; and a two-pixel boundary part having a large density difference from image signals of pixels in the main scanning direction and the sub-scanning direction in the matrix area. Detecting a continuous edge that continues above, determining the matrix area as an area other than a character area when the continuous edge is detected in at least one of the main scanning direction and the sub-scanning direction, and determining when the continuous edge is not detected. A second area determination unit that determines the matrix area as a character area; and a determination result of the first and second area determination circuits.
Detecting the determination result of the peripheral area of the matrix area,
A third area determination circuit that determines whether the matrix area is a character area or another area based on the determination result of the peripheral area; and a third area determination unit that determines the character area.
A first binary conversion unit that converts the image signal extracted by the pixel extraction unit into a binary signal; and a determination of the photographic region by the first region determination unit or a determination by the third determination unit. A second binary conversion unit that converts the image signal extracted by the pixel extraction unit into a binary signal by a binary conversion different from the first binary conversion unit, by determining an area other than the character area; An image processing apparatus including: 8. The first binary conversion means executes a binary conversion suitable for a character image, and the second binary conversion means
The image processing apparatus according to claim 7, wherein a binary conversion suitable for a halftone image is performed. 9. A pixel extracting means for extracting an image signal in a first matrix area configured based on an image signal corresponding to a density of pixels of an image, and a pixel extracting means for extracting an image signal in the first matrix area. First area determining means for determining whether the first matrix area is a character area or a photograph area and generating a character area determination signal and a photograph area determination signal; and a main scanning direction in the first matrix area. And a continuous edge in which a boundary portion having a large density difference continues for two or more pixels from an image signal of a pixel in the sub-scanning direction, and when the continuous edge is detected in at least one of the main scanning direction and the sub-scanning direction, the first A second area discriminating means for generating a second signal when the continuous edge is not detected; and a second area discriminating means for generating a second signal based on the photographic area judgment signal, the first signal and the second signal. of A third area discriminating means for forming a matrix and generating a third signal representing a character area and a fourth signal representing an area other than the character area, respectively, according to a signal pattern in the second matrix area; A first binary conversion unit that converts an image signal extracted by the pixel extraction unit into a binary signal in accordance with the third signal, and a photographic region determination signal and the fourth signal, An image processing apparatus comprising: a second binary conversion unit that converts the image signal extracted by the pixel extraction unit into a binary signal by a binary conversion different from the first binary conversion unit. 10. The first area discriminating means, means for detecting a difference between a maximum value and a minimum value of an image signal in the first matrix area, and according to whether the difference is larger than a reference value. And the first
Determine whether the matrix area is a photo area or a text area,
The image processing apparatus according to claim 9, further comprising: a determination unit configured to generate the character area determination signal and the photograph area determination signal.