JP3032704B2 - Image processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method , and more particularly to an image processing method for dividing an image into different regions and processing the divided image.

[0002]

2. Description of the Related Art As described in Japanese Patent Publication No. 58-3374, a conventional method for separating image regions is configured to recognize and separate image features in pixel units or block units. I have.

[0003]

However, in the above conventional example, when recognizing the features of an image in pixel units,
Since the determination result varies, for example, the character background of the character area is determined to be a photograph part, or a character part is detected in the photograph area. (1) The compression efficiency at the time of feeling or the like is poor. (2) Switching noise is noticeable during display. There are drawbacks such as.

In the case of recognizing the characteristics of an image in units of blocks, when the size of a block is large, the determination is rough, and the characteristics of the entire image may be impaired. Also, the image
Even if the image is divided well according to the features, the division is fine.
Sometimes too much. At that time, perform area integration processing
However, in such area integration processing,
Performing the integration process does not necessarily result in proper integration processing.
There was no problem. The present invention solves such a problem.
It is an object of the present invention to provide an image processing method .

[0005]

To solve this problem, an image processing method according to the present invention divides an image into small areas,
Oite <br/> the image processing method for performing image processing according to the characteristics of the small areas, a dividing step of dividing an image into a plurality of regions according to characteristics of the small areas, Oite divided into the dividing step The distance between the centers of two regions among the plurality of regions,
Area after integration when two areas are integrated and the two areas
An extraction step of extracting a ratio of the area to be newly integrated when integrating, the was Oite extracted to the extraction step 2
Depending on the mutual relationship between the distance between the centers and the ratio of the One region
And an integration step of determining whether or not the two areas need to be integrated.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a block diagram showing a micro judgment section constituting an image processing apparatus according to the present embodiment. Image data read by the input sensor unit 1 having a photoelectric conversion element such as a CCD and a drive system for scanning the photoelectric conversion element is:
It is sent to the A / D converter 2 successively. In the A / D converter 2,
For example, the data of each pixel is converted into 8-bit digital data. As a result, the data is quantized into data having 256 levels of gradation. Next, in the correction circuit 3,
In order to correct the sensitivity unevenness in the input sensor unit 1 and the illuminance unevenness due to the illumination light source, correction such as a shading correction is performed by digital calculation. Next, the corrected signal is supplied to the maximum / minimum operation circuit 4 in the block.

From here, image area separation is performed in pixel units or block units. In this example, an edge detection method for a character portion will be described. The intra-block maximum / minimum operation circuit 4 calculates and outputs the maximum and minimum values of the density of the pixels in the block composed of the matrix of m × n pixels (m and n are positive integers). The maximum and minimum values are supplied to the edge detection circuit 5, which compares a difference α between the maximum value and the minimum value with a threshold value S, and outputs a block determined as a character portion.

The technique of image area separation in pixel units or block units will be referred to as "micro judgment". Here, FIG. 1D shows a hardware configuration of the image processing apparatus of the present embodiment. Reference numeral 100 denotes an image data input unit for inputting digital image data to be processed by the image processing apparatus;
1 is an arithmetic and processing CPU for controlling the image processing apparatus;
102 shows an operation procedure of the CPU 101 in FIG.
R storing a processing program as shown in FIG.
OM, 103 is a RAM for temporary storage and assistance during processing of the CPU 101, 104 is an image memory for storing image data, and 105 is an image data output unit for outputting the result of image processing.

FIG. 5 shows a flow chart of the micro judgment processing of the present embodiment. First, in step S50, image data is read from the image data input unit 100 into the image memory 104. In step S51, the pixel density is quantized to 256 gradations, and in step S52, data correction such as shading correction is performed. In step S53, the maximum value Max and the minimum value Min of the pixel density within a predetermined block of m × n are selected. In step S54, the difference between the maximum value Max and the minimum value Min is compared with a predetermined threshold value S. If the difference is smaller than the threshold value, the m × n block is determined as a photograph / halftone block in step S56, and if larger, the character is determined in step S55. Decide with a block.

In step S57, it is checked whether the determination of all image areas has been completed. If not, step S53 is performed.
And the steps S53 to S57 are repeated. If the processing has been completed, the result of the micro judgment is output in step S58. Actually, this result is stored in the RAM 103. On the other hand, a method of separating an image area into a large area based on the result of the conventionally proposed micro determination of image area separation is referred to as "macro determination" with respect to the micro determination. Hereinafter, a method of performing macro judgment using the output of the above-described micro judgment will be described.

FIG. 1B is a block diagram showing an example of a macro judgment section constituting the image processing apparatus according to the present embodiment.
The result of the micro-determination is first supplied to the pre-processing circuit 6, and in order to reduce the processing load of the macro-determination, the character portion which is not detected as a character portion by the micro-determination to the extent that the data is not distorted is corrected, For example, deletion of a part that seems to be erroneously determined as a character part even though it is not a part is performed. Then, the portion left as the character portion is rectangularized by the rectangular division circuit 7 (squares are also recognized as rectangles).
And the divided rectangle is indicated by the coordinates of two corners that are point-symmetric. In this example, the position and shape of the rectangle are indicated by the coordinates of the upper left corner and the lower right corner of the rectangle, but the present invention is not limited to this.

For each of the divided rectangles, first, a distance between the center points of the other rectangles is calculated by a distance calculation circuit 8 between rectangle center points, and then a calculation circuit 9 calculates the product of the areas of the rectangles. Then, the product of the areas is divided by the square of the result of the rectangular center point distance calculation circuit 8. The result of the operation by the operation circuit 9 is sent to a comparator 10 which compares the result with a predetermined threshold T _1, and based on the result of the comparison, the two rectangles are integrated into a circumscribed rectangle to form a new rectangle.

The above integration method is performed between all the rectangles (or between a part of the rectangles) to obtain a large area image area separation determination result. Hereinafter, an example of a method in each block of the macro determination processing will be specifically described. First, as a pre-process for reducing the load of the macro judgment, the pre-processing circuit 6 employs a method of combining the processes shown in FIGS. 2A and 2B. FIG. 2A shows a process of transferring to black unless all the blocks in the eight directions of the upper, lower, left, and right directions of the white block are white. FIG. 2B shows all the blocks in the eight directions of the upper, lower, left, and right directions of the black block are black. Other than the case, the process of inverting to white is shown (black in the figure is indicated by *). In other words, FIG. 2A is a process of proceeding in the direction of increasing the area, and FIG. 2B is a process of proceeding in the direction of decreasing the area. When the processing as shown in FIG. 2A is performed, small areas or elongated areas, which are noise, are buried.
Even if the processing as shown in the figure is performed, the area once occupied is not thinned, so that the places where the judgment results vary too finely in the micro judgment can be collected.

Next, FIG. 3 shows an example of a method of dividing a black block into small rectangles in the small rectangle dividing circuit 7. Reference numeral 31 denotes scanning of an image, in which a run length of a black block is detected during this scan, and a method of cutting out a maximum rectangle having the run length as one side is shown. With this method, rectangle 3
The small rectangles are sequentially cut out from 2 to a rectangle 35.

Finally, FIG. 4A shows an example of a method of integrating the divided small rectangles by the rectangular center point distance calculation circuit 8, calculation circuit 9, and comparator 10 of the present embodiment. 41a, 4
1b shows a divided small rectangle, and each center point is 42
a, 42b. Now, the rectangular center points 42a and 42b
If the distance between them is D and the area of each rectangle is S ₁ , S ₂ ,
It is compared with a predetermined threshold T _1, when filled with equation (1) shown below, taken together the two rectangles as circumscribed rectangle (hereinafter referred to as first condition).

T ₁ <(S ₁ × S ₂ ) / D ² (1) As can be seen from equation (1), when two rectangles are to be integrated as the same area, if they are too far apart, D Are not integrated because of the large area, even if the two rectangles are separated, if the area of each rectangle is large, the possibility of the same area is high, and (S ₁ ×
S ₂ ) grows larger and is integrated.

However, the expression (1) of the integration condition is not limited to this. This equation (1) is merely an example showing that rectangles that are far apart are not integrated, but that if the area of the rectangle is large, it is recognized as the same area. An equation showing the same concept, for example, a denominator of 3 A processing method such as raising to the power is also conceivable. FIG. 6A shows a flowchart of the macro judgment processing of the present embodiment.

First, the result of the micro judgment is read from the RAM 103 at step S60. In step S61, preprocessing such as filling of a small area between blocks is performed, and in step S62, a group of the same determination result is divided into small rectangles based on the result of the micro determination. In this example, a small rectangle is created based on the character block. In step S63, the distance between the center points of two adjacent rectangles among the small rectangles divided is calculated, and in step S64, the area of both rectangles is calculated.

[0019] In step S65, the square at a rate ivy value of the distance between the product of the center points of both rectangular areas, with a predetermined threshold value T _1. If the comparison result is greater than thresholds T ₁ creates a new rectangle that is integrated in step S66 as a rectangle to be integrated. In step S67, it is determined whether or not all image areas have been processed. If not, the process returns to step S63, and steps S63 to S67 are repeated. If the determination of the end of this processing is repeated until there is no rectangle to be integrated instead of the entire area, a simple division is achieved.

When the processing is completed, the process proceeds from step S67 to step S68, and the result of the macro judgment is stored in the RAM 1 again.
03 is stored. Although not shown in this example, a process using the divided data in the RAM 103, for example, a process of performing a dither process of a different matrix between the inside and outside of the divided area is performed according to each image processing. FIG. 1C is a block diagram showing another example of the macro decision unit constituting the image processing apparatus of the present embodiment.

The operations of the pre-processing circuit 6, the small rectangular division circuit 7, and the rectangular center point distance calculation circuit 8 are the same as in the previous example.
The calculation result of the rectangular center point distance calculation circuit 8 is calculated by the comparator 11
Is compared with an arbitrary threshold value T ₂ . Here, the area S ₄ newly added to the area by integration is compared with the area S ₃ when it is assumed that the rectangles meeting the integration conditions are integrated as circumscribed rectangles by the distance calculation circuit 8 between the rectangular center points and the comparator 11. and comparing P is calculated, and the calculation result is compared with a given threshold T ₃ in the comparator 13, and if smaller integrated with rectangle circumscribing the two rectangular one new rectangular area.

This time, a method of comparing the distance between the rectangular center points with an arbitrary threshold value and then comparing the rectangular gap with an arbitrary threshold value is adopted. The above integration method is applied to all rectangles (or to a part of rectangles) to obtain a large area image area separation determination result. An example of a method for integrating the small rectangles separated in this example is shown in FIGS. 4A to 4D.

[0023] Figure 4A, as described above, the distance D between the center of the rectangle points, a method for integrating smaller than a certain threshold T ₂ (hereinafter referred to as a second condition). FIG.
If the ratio P of the area S ₄ of the newly integrated area to the area S ₃ of the rectangle after integration assuming that two rectangles have been integrated is smaller than an arbitrary threshold T _3, a method of integration (hereinafter referred to as “first 3 conditions). In the method of the second condition,
As shown in FIG. 4C, there is a disadvantage that the area (shaded area) to be newly integrated under the same integration condition is not constant. In the method of the third condition, one rectangle is formed as shown in FIG. 4D. If it is large, there is a disadvantage that a newly integrated area (shaded area) becomes large.

Therefore, in the present embodiment, a combination of the technique of the second condition and the technique of the third condition is performed to cancel each of the disadvantages. That is, the threshold T ₂ that is the second condition
By adjusting the threshold value T ₃ and the third condition, in the case of FIG. 4C, even if the second condition is passed, the region to be newly integrated under the third condition is large, and the region is not integrated. In the case of FIG. 4D, even if the third condition is passed, under the second condition, if one rectangle is large, the distance between the center points becomes large, so that it is not integrated and the disadvantage can be overcome.

FIG. 6B shows a flowchart of the macro judgment processing of the other example. The processing in steps S70 to S73 is the same as the processing in steps S66 to S63 in FIG. 6A. In step S74, the distance between the calculated center points to a determination whether a predetermined greater than the threshold value T ₂ which in step S73, the process proceeds to step S78 without the integration larger. Proceed to step S75 is smaller, the calculation of the rectangular gap, that is, a value is calculated by subtracting the sum of two rectangular areas from integrated rectangular area described above, comparing the calculation result with a predetermined threshold value T ₃ in step S76. It is greater than the threshold value T _3,
The process proceeds to step S78 without integration. If it is smaller, the two rectangles are integrated in step S77 to create one new rectangle.

In step S78, the end of the integration process is determined, and the process returns to step S73 and repeats steps S73 to S78 until there is no more image area or rectangle to be integrated. If it is determined in step S78 that the processing is to be ended, the result of the macro determination is output in step S79 in the same manner as in step S68 of FIG. 6A. With the above-described method, rectangles meeting the integration conditions are integrated as new rectangles, and as a result, rectangles can be cut out from a large area.

In the above-described embodiment, in the micro judgment, the character portion detection using the edge detection method has been described as an example, but the present invention is not limited to this. If the result of detecting a character part / halftone part by other methods is used, by macro judgment,
Naturally, those areas are cut out as a large area rectangle.
The first to third conditions described in the present embodiment are examples of conditions for integrating rectangles based on the distance between the center points and the area, and the present invention is not limited to these conditions. It is not limited to the example.

If it is desired to further shape the result of the above embodiment as a rectangle, the process of proceeding in the direction of making the area thicker and thinner as described in the pre-processing of macro judgment is repeated several times. Can be realized by: Although the macro judgment result in the above embodiment is a character portion, a large area rectangle such as a photograph or a halftone dot portion can be cut out by inverting the result and shaping it into a rectangle. By combining the above, any desired region can be cut out.

Further, in the above-described embodiment, the maximum rectangle having the run length as one side is cut out in the small rectangle division, but the technique here is not limited to this. For example, any division method such as a pyramid division method can be used, in which the entire image is divided into four, and if a black block exists in the divided region, the method is further divided into small rectangles by repeating the method of further dividing into four.

Further, in the third embodiment, when the result of the macro judgment is obtained after inverting the result of the macro judgment, a part such as a white part is also detected. If the ratio of black blocks in the rectangle is insignificant, and a condition for deleting the rectangle is added, the blank portion will not be detected. As described above, by separating the image area as a large-area rectangle, there is an effect that the compression efficiency at the time of filling is increased and the switching noise at the time of display is reduced.

[0031]

As described above, only the distance between the regions is considered.
When performing area integration processing,
There is a possibility that the area to be integrated is not constant
I will. However, according to the present invention, the distance between the regions is added.
The area after integration when the two regions are integrated and the area
Ratio of newly merged areas when two areas are merged
This disadvantage is eliminated because area integration is performed in consideration of
it can.

[Brief description of the drawings]

FIG. 1A is a block diagram illustrating a micro-determination unit included in an image processing apparatus according to an embodiment;

FIG. 1B is a block diagram illustrating an example of a macro determining unit included in the image processing apparatus according to the embodiment;

FIG. 1C is a block diagram showing another example of the macro determining unit included in the image processing apparatus according to the embodiment;

FIG. 1D is a diagram showing a hardware configuration of the image processing apparatus according to the embodiment;

FIG. 2A is a diagram showing an example of preprocessing in a macro determination unit;

FIG. 2B is a diagram showing an example of preprocessing in a macro determination unit.

FIG. 3 is a diagram illustrating an example of small rectangle division by a macro determination unit;

FIG. 4A is a diagram illustrating a method of integrating rectangles by a macro determination unit;

FIG. 4B is a diagram showing a method of integrating rectangles by a macro determination unit;

FIG. 4C is a diagram showing a method of integrating rectangles by the macro determination unit;

FIG. 4D is a diagram showing a method of integrating rectangles by a macro determination unit;

FIG. 5 is a flowchart of a micro determination process,

FIG. 6A is a flowchart of the macro determination process in FIG. 1B;

FIG. 6B is a flowchart of the macro determination process in FIG. 1C.

[Explanation of symbols]

Reference Signs List 1 input sensor 2 A / D converter 3 correction circuit 4 maximum / minimum calculation circuit in block 5 edge detection circuit 6 distance calculation circuit between rectangular center points 9 calculation circuit 10 comparators 41a, 41b small rectangles 42a, 42b rectangular center point D area increasing with distance S _1, S ₂ rectangular area S ₃ integrated rectangular area S ₄ integrated between the center of the rectangle points

Claims (1)

(57) [Claims] 1. An image processing method for dividing an image into small regions and performing image processing according to the characteristics of the small regions, comprising: a dividing step of dividing the image into a plurality of regions according to the characteristics of the small regions; two of the plurality of regions Oite divided into the dividing step
When the distance between the centers of the two areas is integrated and the two areas are integrated
The area after integration and the new area when the two areas are integrated
An extraction step of extracting a ratio of the integrated the region, the center of the two regions that are Oite extracted in said extraction step
Depending on the interrelationship between the distance between and the ratio, the two
An image processing method characterized by comprising the integration step of determining the necessity of integration area.