JP2000076468A - Method and device for extracting contour of picture, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the processing time by making a device efficiently perform able the processing of contour extraction concerning an optional density value. SOLUTION: A noticed pixel extracting part 20 extracts noticed pixels one by one in order from the pixel showing the max. value of a density value in a picture. In the case that the four surrounding contour sides of the noticed pixel are not contained in an existing contour line, a contour line consisting of the four contour sides is set as a new contour line, contour line connecting information DC indicating the connecting state of the new contour line is generated and also contour line management information DM including a start side selecting either one among the four contour sides of the noticed pixel and including a start density value obtained by making the density value of the noticed pixel as the start density of an effective density range is generated. When any one among the four contour sides of the noticed pixel is contained in the existing contour line, contour line connecting information DC concerning the existing contour line is updated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for extracting an outline of an image and a recording medium storing a program for extracting an outline of an image by a computer.

[0002]

2. Description of the Related Art When an image is processed by a computer, an outline of the image is sometimes extracted. The outline of the extracted image is subjected to conversion processing such as rotation, enlargement, and reduction of the image within the outline, and the image within the outline is filled with a desired color,
It is used for a process of combining an image within the outline with another image or descending.

Here, as a method of extracting the outline of an image, there is a method disclosed in Japanese Patent Laid-Open No. 5-242246. In this method, an image is scanned line by line in the main scanning direction, and a contour line in the main scanning direction is extracted in each scan. Then, if the end points of the two contour lines detected in the main scanning direction match, they are connected in the sub-scanning direction to form one contour line. By performing such processing for each line for all images, a desired contour is extracted.

[0004]

However, in the above-described conventional method for extracting contours of an image, when extracting several contours with different density values, the entire image area is scanned line by line. A process of extracting one contour line must be performed for each density value, and there is a problem that the time required for contour extraction is long.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a method and an apparatus for extracting an outline of an image, which efficiently performs an outline extraction process for an arbitrary density value and shortens the processing time. An object is to provide a recording medium on which a program is recorded.

[0006]

According to one aspect of the present invention, there is provided a method for extracting an outline of an image, comprising the steps of: (a) indicating a maximum density value in the image; Extracting a pixel of interest one pixel at a time in descending order from the pixel; and (b) when a plurality of contour sides surrounding the pixel of interest are not included in the existing contour line, a contour line composed of the plurality of contour sides Is set as a new contour line, and contour line connection information indicating the connection state of the new contour line is generated,
A start side of the new contour line in which any one of the plurality of contour sides of the target pixel is selected, and a start density in which a density value of the target pixel is set as a start density of an effective density range of the new contour line Generating contour management information including a value, and (c) when any of the plurality of contour sides of the pixel of interest is included in a predefined contour, Updating the outline connection information; and (d) when the update eliminates at least one existing outline that includes any of the outline sides of the target pixel, the existing outline disappears. Adding a density value of the pixel of interest to the contour management information on a line as an end density value indicating an end density of an effective density range of the existing contour line.

According to a second aspect of the present invention, in the method for extracting an outline of an image according to the first aspect, a pixel having the same density value in the image is set as the target pixel and the steps (a) to (d) are performed. Is repeatedly output to output the contour line connection information generated / updated.

According to a third aspect of the present invention, there is provided the image contour extracting method according to the first aspect, wherein (e) the (a) to (d)
Storing the contour management information generated by repeatedly performing the step, and extracting a contour of a predetermined density value, (f) the start density value included in the contour management information and the Specifying a contour of the predetermined density value based on the effective density range indicated by an end density value, and acquiring the start side from the contour management information for the contour, (g) the step of: Sequentially extracting contour sides from the start side according to a predetermined rule.

According to a fourth aspect of the present invention, in the image contour extracting method according to any one of the first to third aspects, the steps performed prior to the steps (a) to (d) are as follows:
(h) a step of securing a recording area for recording pixel information for all pixels constituting the image, and (i) searching for all pixels constituting the image and counting the number of pixels for each density value And (j) a step of calculating the cumulative number of pixels less than the density value for each density value based on the result of the counting, and (k) a step of extracting pixels constituting the image one by one, (l) detecting the density value of the pixel extracted in the step (k), obtaining the cumulative pixel number corresponding to the density value, and setting the cumulative pixel number at the position of the recording area corresponding to the cumulative pixel value. Recording the pixel information specifying the extracted pixels, and updating the value of the cumulative number of pixels, and performing the steps (k) to (l) for all the pixels constituting the image. It is characterized by performing repeatedly up to.

According to a fifth aspect of the present invention, there is provided an apparatus for extracting an outline of an image, comprising: (a) a pixel of interest extracting a pixel of interest one by one in descending order from a pixel having a maximum density value in the image; Extracting means, (b) when a plurality of contour sides around the pixel of interest are not included in the existing contour line, a contour line composed of the plurality of contour sides as a new contour line; Contour line connection information indicating a connection state is generated, and the start side of the new contour line in which any one of the plurality of contour sides of the target pixel is selected, and the density value of the target pixel are stored in the new Contour line information generating means for generating contour line management information including a start density value as a start density of an effective density range of a contour line; and (c) storing the contour line connection information and the contour line management information. And (d) the plurality of rings of the pixel of interest. When any one of the contour sides is included in the existing outline, the outline connection information stored in the storage unit is updated for the existing outline, and the update of the target pixel is performed by the update. In a case where at least one existing contour line that includes any one of the outline sides disappears, the attention is paid to the outline management information stored in the storage unit for the existing contour line that disappears. Updating means for additionally updating the density value of the pixel as an end density value indicating the end density of the effective density range of the existing contour line.

According to a sixth aspect of the present invention, there is provided a recording medium in which a program for extracting a contour of an image by a computer is recorded. A procedure of extracting a pixel of interest one pixel at a time in descending order, (b) when a plurality of contour sides around the pixel of interest are not included in the existing contour line,
A contour line including the plurality of contour sides is set as a new contour line, contour line connection information indicating a connection state of the new contour line is generated, and any one of the plurality of contour sides of the target pixel is set. (C) generating contour management information including a start side of the selected new contour, and a start density value having the density value of the target pixel as a start density of an effective density range of the new contour. If any of the plurality of contour sides of the pixel of interest is included in the existing contour, a procedure for updating the contour connection information for the existing contour, (d) by the update In a case where at least one existing contour line in which any of the outline sides of the pixel of interest is included disappears, the density value of the pixel of interest is determined with respect to the outline management information for the existing outline that disappears. The above Image contour extraction program for executing the steps to add as an end density value indicating the end concentration of the active concentration range of the contour line is recorded.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <1. Summary of the Invention> The above-described conventional image contour extraction method scans, in the sub-scanning direction, contour extraction processing for each line along the main scanning direction on an image plane including the main scanning direction and the sub-scanning direction. there were.

On the other hand, in the method for extracting an outline of an image according to the present invention, a pixel is sequentially extracted one by one from a pixel having the maximum density value among pixels constituting the image, and a new outline is generated. For example, an existing contour is updated.

Here, a line that is a boundary between one pixel and an adjacent pixel is called an outline side.
One pixel has four contour sides.

Therefore, it is determined whether any one of the four contour sides of a pixel sequentially extracted from the maximum density value (hereinafter, referred to as a “pixel of interest”) is included in the already generated contour line. If none of the outline sides is included in the existing outline, a new outline including the four outline sides of the pixel of interest is newly generated, while any outline is included in the existing outline. If so, the existing contour is updated so that the target pixel is included in the contour.

FIG. 1 is a diagram showing the concept of generation / update of such a contour line. In FIG. 1, 4 pixels PA of 2 × 2
The density value of the pixel PA is LV4, the density value of the pixel PB is LV3, the density value of the pixel PC is LV2, and the density value of the pixel PD is LV1.
Here, the relationship between the density values is LV1 <LV2 <LV3 <
LV4. First, when the maximum density value LV4 is extracted, the pixel PA is extracted. Then, as shown in FIG. 1A, four contour sides of the pixel PA are generated as new contour lines Ea. Next, as shown in FIG.
The pixel PB of V3 is extracted. Since the contour side in contact with the pixel PA among the four contour sides of the pixel PB is already included in the contour line Ea, the contour line Ea is updated to generate the contour line Eb. Next, as shown in FIG. 1C, the pixel PC having the density value LV2 is extracted. Since the contour side in contact with the pixel PA among the four contour sides of the pixel PC is already included in the contour line Eb, the contour line Eb is updated to generate the contour line Ec. Finally, as shown in FIG. 1D, the pixel PD having the density value LV1
Is extracted. Pixel PB among four contour sides of pixel PD
Since the two contour sides that are in contact with and PC are already included in the contour line Ec, the contour line Ec is updated to generate the contour line Ed.

In this process, four pixels PA
All the contour lines Ea to Ed existing for each density value are extracted during the processing of .DELTA.PD one pixel at a time. Therefore,
By outputting the contour when the contour for each density value is extracted, the contour for all the density values can be obtained by performing the process for each pixel for the entire image area only once. Can be.

Further, when a new contour is generated in such a process, one of the contour sides constituting the new contour can be traced later so that the contour can be tracked. Is set as the starting edge. For this reason, even if the contour is updated as the above processing proceeds, the contour having a predetermined density value can be easily extracted by tracing the contour from the start side based on a predetermined rule. it can.

Hereinafter, a detailed configuration for realizing such processing will be described.

<2. Configuration of Apparatus> FIG. 2 is a block diagram showing the configuration of an image contour extraction apparatus 100 as one embodiment of the present invention. As shown in FIG. 2, the contour extracting apparatus 100 includes a pre-processing unit 10, a target pixel extracting unit 20, a contour side determining unit 30, a contour forming unit 40, a memory 50, a contour extracting unit 60, and a storage unit 70. Have.

The storage unit 70 is for storing an image as data, and the preprocessing unit 10 is a unit for reading an image from the storage unit 70 and performing preprocessing on the image. In the pre-processing, the generation of the framed image, the assignment of the contour side numbers, and the sorting of the pixels based on the density values are performed. The details of these processes will be described later.

The pixel-of-interest extraction unit 20 sequentially extracts pixels of interest one by one in order from the pixel having the highest density value among a plurality of pixels constituting the image.

Then, the contour side judging section 30 judges whether any of the four contour sides of the target pixel is included in the already generated contour line, and determines the result as the contour line formation. Inform part 40. In determining the contour side, the contour line connection information DC stored in the memory 50 is referred to. The outline is formed by connecting a plurality of outline sides continuously, and the outline line connection information DC already describes the connection state of the plurality of outline sides forming the outline. By referring to DC, it is possible to determine whether any of the four contour sides of the target pixel is included in the already generated contour line.

FIG. 3 is a diagram for explaining the contour line connection information DC. For example, as shown in FIG. 3A, when the pixel PA is extracted as a pixel of interest and a new outline is formed by four outline sides a, b, c, and d around the pixel PA. The outline connection information DC is described in a state as shown in FIG. From the contour line connection information DC in FIG. 3B, the contour side a is connected to the contour side b, the contour side b is connected to the contour side c, the contour side c is connected to the contour side d, and the contour side d is connected to the contour side a. You can see that it is. The contour number of the contour formed by these contour sides a, b, c, and d is “1”.

Then, when the pixel PB shown in FIG. 3A is extracted as the pixel of interest, four contour sides b and 4 around the pixel PB can be obtained by referring to the contour connection information DC of FIG. The contour side b of e, f, and g is already the contour line number "1"
It can be seen that it is included in the contour line. Therefore, the use state of each contour side of the target pixel can be determined by referring to the contour line connection information DC. Note that it is impossible that one contour side is included in a plurality of contour lines at the same time.

The contour line forming section 40 includes a contour line information generating section 40
a and a contour line information updating unit 40b, when the contour side determining unit 30 determines that none of the four contour sides of the target pixel is included in the already generated contour line. Indicates that while the contour information generation unit 40a operates to generate a new contour, it is determined that any of the four contour sides of the target pixel is included in the already generated contour. The contour line information updating unit 40b
Operates to update the existing contour line. This update processing includes processing of separation, integration, and disappearance of contour lines, as described later.

When a new outline is generated, the outline information generation unit 40a changes the connection state of the outline to the outline connection information D.
C and generate contour line management information DM,
It is stored in the memory 50.

The outline information updating section 40b updates the connection state of the outline described in the outline connection information DC when updating the existing outline.

When at least one of the existing outlines has disappeared due to the update, the outline information updating unit 40b executes
The density value one higher than the density value of the current pixel of interest is stored in the column of the end density value of the outline management information DM for the disappeared outline. Here, when at least one of the existing contour lines disappears due to the update, the case where the start side registered in the contour line management information DM becomes invalid due to the addition of the pixel of interest and the case where two or more contour lines This includes the case where only one outline remains after integration and the other outline disappears. Further, when there is no more target pixel to be extracted next, the contour line information updating unit 40b stores “0” as the end density value for the contour line management information DM for which the end density value has not yet been stored. I do. Note that the process of storing the end density value in this manner is called an end process.

Since the outline connection information DC described above is the outline itself, the outline information generation unit 40a and the outline information update unit 40b describe when the new connection state is described in the outline connection information DC or when the outline connection is performed. If the contour line connection information DC is output when the information DC is updated, the contour line is output.

For example, if the density value of the image is 0 to 255, ie 25
When it is desired to extract a contour line having a density value of 126 when there are six gradations, a pixel of interest is sequentially extracted from pixels having a density value of 255, and a contour line is formed for each density value. . Then, when the processing for all the pixels having the density value of 126 is completed, a desired outline is formed in the outline connection information DC, and this may be output. In this case, the extraction of pixels having a density value of 125 or less does not need to be performed, so that efficient contour extraction is performed.

However, in this embodiment, once the outline is formed for each pixel for the entire image, the outline is formed for each pixel when the outline is to be extracted again. The contour management information DM is stored in the memory 50 in order to eliminate the necessity.

Here, the outline management information DM will be described. FIG. 4 is a diagram illustrating the outline management information DM. The numbers in each pixel shown in FIG. 4A indicate the density value of each pixel.

For example, as shown in FIG.
Is extracted as a pixel of interest, and when a new outline is formed by four outline sides a, b, c, and d around the pixel PA, the outline management information DM is shown in FIG.
Are described in the state shown in FIG. A number that does not overlap with an existing contour number is assigned to the contour number of the contour management information DM. The start side number stores the number of a contour side (that is, a start side) that becomes an extraction start point when a newly generated contour line is extracted later.

As the start side, a contour side shared with the pixel having the minimum density value among the pixels adjacent to the target pixel,
Alternatively, it is preferable to select a contour side shared with a pixel having a density value having the largest difference from the density value of the target pixel among the pixels adjacent to the target pixel. The reason is that the effective density range in which the starting side is effective can be maximized. Therefore, in the case of the density value as shown in FIG. 4A, the contour side a is determined as the start side.

The starting density value stores the density value “9” of the pixel of interest PA. The end density value stores a density value that is one higher than the density value of the target pixel when the outline with the outline number “1” is updated and disappears, that is, when the start side becomes invalid. .

The number of contour sides stores the number of contour sides forming the contour with the contour number "1". In the case of the example of FIG. 4A, the contour lines are four contour sides a, b, c, and d.
, The number of contour sides is “4”.

The contour line management information DM is stored in the memory 5.
When the contour is held at 0, when a contour having an arbitrary density value is to be extracted later, the contour extracting unit 60 determines that the start side of the contour is valid based on the start density value and the end density value of the contour management information DM. The effective density range can be known, and all the starting sides where the density value to be subjected to contour line extraction exists within the effective density range can be acquired. Then, the contour extraction unit 60
However, if the contour extraction is performed from these start sides based on a predetermined rule, the contour extraction of the image can be appropriately performed.

That is, in the device shown in FIG.
When the outline management information DM has not been stored in 0 yet, the pre-processing unit 10, the pixel-of-interest extraction unit 20, the outline side determination unit 30, and the outline generation unit 40 function to operate for each density value. As the contour is formed, the contour management information DM and the contour connection information DC are sequentially stored in the memory 50. In addition, when generating / updating the contour line connection information DC, the contour line forming unit 40 can output the contour line by outputting it.

On the other hand, the outline management information DM is stored in the memory 50.
Is already stored, the contour extraction unit 60 functions to read the contour management information DM in the memory 50 and extract the contour from the starting side registered for each contour based on a predetermined rule. The contour extracting unit 60 outputs the contour extracted.

<3. Preprocessing> The preprocessing performed in the preprocessing unit 10 will be described.

First, a framed image is generated as a first preprocessing. FIG. 5 is a diagram illustrating generation of a framed image. FIG. 5A shows an original image to be subjected to contour extraction, FIG. 5B shows an intermediate stage in generating a framed image, and FIG. 2 shows a framed image generated by the above method. FIG. 5 shows an example in which the original image is composed of 20 5 × 4 pixels, and the number in each pixel indicates the density value of that pixel.
In the following, processing on an original image as shown in FIG. 5A will be described as an example.

The preprocessing section 10 secures an image area in which the periphery of the original image of FIG. 5A is expanded by one pixel (FIG. 5B). As a result, the density value 0 is stored for all pixels that are distributed around the original image. In this way, a framed image composed of 7 × 6 42 pixels is generated as shown in FIG.

The reason for generating such a framed image is as follows.
This is because the same processing can be performed on all the contour sides of the original image to improve processing efficiency. Each contour side located on the outer peripheral portion of the original image shown in FIG.
Since it is not in contact with other pixels, density value comparison cannot be performed. Therefore, a framed image is generated so that density value comparison can be performed for all contour sides included in the original image. Note that, in the case where exception processing different from other contour sides is performed on each contour side located on the outer peripheral portion of the original image illustrated in FIG. 5A, it is unnecessary to generate a framed image.

Next, as a second preprocessing, a process of assigning a contour side number to each contour side including the framed image is performed. FIG. 6 is a diagram for explaining assignment of contour side numbers. If there are n pixels in the main scanning direction X in the framed image, the number 0 is assigned to the lower side of the leftmost pixel on the first line, and the number 1 is assigned to the right side. Then, numbers are sequentially assigned to the lower side of the second pixel on the first line, the right side, the lower side of the third pixel, the right side, and so on. Since there are n pixels in the main scanning direction X, (2n) is assigned to the lower side of the leftmost pixel on the second line, and (2n + 1) is assigned to the right side. In the same manner, numbers are sequentially assigned to the lower side of the second pixel, the right side, the lower side of the third pixel, and the right side of the second line, and the contour side numbers are allocated to all the lines.

In this way, the 7 × 6 as shown in FIG.
FIG. 7 shows a case where contour side numbers are assigned to the framed image. In FIG. 7, the thick line indicates the original image portion. Therefore, by the assignment of the contour side numbers, unique numbers are assigned to all the contour sides necessary for extracting the contour of the original image. Here, as shown in FIG. 7, a contour side number is not assigned to each contour side located at the upper end of the framed image and each contour side located at the left end, but these contour sides correspond to the contours of the original image. There is no problem because it cannot happen.

When assigning the contour side numbers only to the original image, exception processing must be performed to assign the contour side numbers to the contour sides located at the upper end and the left end of the original image. However, when assigning the contour side numbers to the framed image as described above, the numbers are assigned to all the contour sides included in the original image without performing the exception processing. Thus, the contour side numbers can be efficiently assigned, and the processing time can be reduced.

Next, as a third pre-process, a process of sorting the pixels constituting the original image based on the density value is performed.
The sort based on the density value is performed by the target pixel extracting unit 2.
0 is for enabling the pixel of interest to be sequentially extracted from the pixel having the highest density value. Therefore, any method may be used as long as it can be sorted so that one pixel can be extracted in descending order of the density value from the pixels constituting the original image. can do.

However, various known sorting methods require a lot of time for judgment processing and data exchange processing, so that sorting takes time.

Therefore, in this embodiment, it is preferable to apply the following sorting method in order to perform the sorting efficiently.

First, before performing the sorting process, coordinate values are set for each pixel of the framed image. Generally, when a coordinate value is set for each pixel in the image plane, an XY coordinate system expressed by a position in the main scanning direction X and a position in the sub scanning direction Y is used. In this case, the X coordinate and the Y coordinate are used. Must be managed. Therefore, in this embodiment, assuming that the framed image has n pixels in the main scanning direction X, one value derived by “(Y coordinate) × (n) + (X coordinate)” is represented by coordinates. Value. That is, the coordinate value is set for each pixel by sequentially assigning one number along the main scanning direction X of the framed image.
When the coordinate values are set for the framed image shown in FIG. 5C in this way, the coordinate values of each pixel are as shown in FIG. In FIG. 8, the number of each pixel is a coordinate value, and the display of the density value is omitted. The thick line in FIG. 8 indicates an original image portion.

Next, the process proceeds to the actual sorting process. First, all pixels included in the original image are searched, and the number of pixels for each density value is counted. When the number of pixels for each density value is counted for the original image shown in FIG. 5, a count result as shown in FIG. 9 is obtained. The pre-processing unit 10 temporarily stores the count result in a memory (not shown) provided therein.

Then, based on the count result shown in FIG. 9, for each density value, the cumulative number of pixels indicating a density value lower than the density value is derived. For example, from the count result in FIG. 9, the cumulative number of pixels of density value 1 is 0 because it is the number of pixels of density value 0, and the cumulative number of pixels of density value 2 is the sum of the number of pixels of density values 0 to 1. Therefore, the number of pixels having a density value of 3 is 5, which is the sum of the number of pixels having a density value of 0 to 2, and thus is 5. When the cumulative number of pixels is obtained for each density value in this manner, FIG.
become that way.

Then, a buffer area for storing the sort data is secured by the number of pixels constituting the original image.
Since the original image shown in FIG. 5 has 20 pixels,
20 buffer areas are reserved. Then, one pixel is extracted in the order of coordinate values from the pixels constituting the original image, and the density value is detected.

In the case of the original image shown in FIG. 5, a pixel having a density value 2 is first extracted as shown in FIG. Since the number of accumulated pixels corresponding to the density value 2 of the extracted pixel is 2, the coordinate value of the extracted pixel is stored at the storage position corresponding to 2 in the buffer area, that is, at the position of memory address 2. FIG.
In the case of 1, since the coordinate value of the extracted pixel having the density value 2 is 8 (see FIG. 8), the coordinate value 8 is stored at the position of the memory address 2.
Is stored. When the coordinate values are stored in the buffer area, 1 is added to the cumulative number of pixels 2 of the density value 2 to change the cumulative number of pixels of the density value 2 to 3.

Next, as shown in FIG. 12, pixels having a density value of 9 are extracted. Since the accumulated number of pixels corresponding to the density value 9 of the extracted pixel is 19, the coordinate value of the extracted pixel is stored at the storage position corresponding to 19 in the buffer area, that is, at the position of the memory address 19. In the case of FIG. 12, since the coordinate value of the extracted pixel having the density value 9 is 9 (see FIG. 8), the coordinate value 9 is stored at the position of the memory address 19. When the coordinate values are stored in the buffer area, 1 is added to the cumulative number of pixels 19 of the density value 9 to change the cumulative number of pixels of the density value 9 to 20.

Hereinafter, the same processing is repeated every time one pixel is selected from the pixels constituting the original image in the order of coordinate values. Then, when the processing for all the pixels constituting the original image is completed, the cumulative number of pixels and the buffer area for each density value are in a state as shown in FIG.

In the buffer area shown in FIG. 13B, the coordinate values of the pixels having the smaller density values are stored in the order from the smallest memory address. For example, the memory address 0, 1 stores the coordinate value of the pixel having the density value 1,
The memory addresses 2 to 4 store the coordinate values of the pixel having the density value 2. Therefore, by performing the above processing, the result of sorting the pixels constituting the original image based on the density value is stored in the buffer area.

When the above sorting method is applied, 2
Sorting can be performed without performing a judgment process of comparing the density values of two pixels or a process of replacing data, so that the time required for sorting can be reduced.

As described above, if the sort result based on the density value is stored in the buffer area, when the target pixel extracting unit 20 sequentially extracts the target pixel from the pixel having the higher density value,
It is only necessary to sequentially acquire coordinate values from the position of the largest memory address in the buffer area and extract the pixels having the coordinate values, and efficient processing can be performed.

<4. Generation and update of contour management information etc.>
Next, a description will be given of a process in which the target pixel extracting unit 20 sequentially extracts the target pixel from the pixel having the highest density value, and generates or updates the outline management information and the outline connection information.

The pixel-of-interest extraction unit 20 sequentially extracts the pixel of interest from the pixel having the highest density value based on the sort result as shown in FIG. Then, the contour side numbers of the four contour sides around the target pixel are obtained. As shown in FIG. 13B, since the coordinate values of the pixels are stored in the sorting result, the numbers of the four contour sides of the target pixel are obtained from the coordinate values. For example, suppose that the coordinate value of the pixel of interest is P, and that n pixels exist in the main scanning direction X of the framed image, and the contour side numbers on the upper, right, lower, and left sides of the pixel of interest are NU, Assuming that NR, ND, and NL, the upper contour side number: NU = (P−n) × 2 The right contour side number: NR = (P × 2) +1 The lower contour side number: ND = (P × 2 ) Left contour side number: NL = (P × 2) −1. Then, the attention pixel extraction unit 20
Sends the four contour side numbers of the pixel of interest to the contour side determination unit 30.

The contour side determining section 30 refers to the contour connection information DC in the memory 50 and determines whether or not the contour side number of the target pixel is included in the already generated contour.

The outline connection information D is stored in the memory 50.
C is not stored yet, or the contour line connection information D
As a result of referring to C, if it is determined that none of the four outline sides of the target pixel is included in the existing outline, the outline information generation unit 40a adds the outline including the four outline sides of the target pixel to the outline information generation unit 40a. Instructs it to be generated. As a result, the contour information generation unit 40a generates a new contour composed of four contour sides around the target pixel, and describes the connection state of the new contour in the contour connection information DC of the memory 50. , And the start side of the new contour is obtained and described in the contour management information DM.

On the other hand, as a result of referring to the outline connection information DC, if it is determined that any of the four outline sides of the target pixel is included in the existing outline, the outline information updating unit 40
b is instructed to update the outline connection information DC and the outline management information DM.

A process in which the contour information updating unit 40b updates the contour connection information DC and the contour management information DM will be described. FIG. 14 is a diagram illustrating a case where four contour sides of the target pixel are included in one existing contour line. In FIG. 14, the hatched pixels are the target pixels, the thin lines are the outline sides, and the thick lines indicate the outline sides included in the outline. As shown in FIG.
Of the three contour sides a, b, c, d, the contour side d is included in the existing contour line E1. When the pixel of interest is added in such a state, the existing contour line E1 is updated as shown by the thick line in FIG.

FIG. 15 is a diagram showing a process of updating the contour E1 of FIG. 14A to the contour E1 of FIG. 15 (a) to 15 (e), the left diagram is the contour connection information DC stored in the memory 50, and the right diagram is a case where a contour is formed from four contour sides of the target pixel. 3 shows a virtual connection state of the contour side of the pixel of interest temporarily stored in the memory 50.

First, when the target pixel shown in FIG. 14A is extracted, the outline connection information DC of the outline E1 and the virtual connection information are as shown in FIG. 15A. That is, the contour line E
The connection state of No. 1 is “e → d → f → g”. The connection between the four contour sides of the pixel of interest is “a → b →
c → d → a ”.

By adding the target pixel this time, the contour side d is not included in the contour line E1. Therefore, in the contour line connection information DC, the next contour side number for the contour side e with the contour side d as the next contour side (connection destination) is updated. That is, referring to the virtual connection state, since the contour side d is connected to the contour side a, the next contour side number for the contour side e is rewritten to a.
As a result, the outline connection information DC and the virtual connection information of the outline E1 are as shown in FIG.

Also, by adding the pixel of interest this time, the contour side d is not included in the contour line E1.
The contour side d in the virtual connection information is the next contour side (connection destination)
The next contour side number for the contour side c is updated. That is, referring to the outline connection information DC, the outline side d is connected to the outline side f, so the next outline side number for the outline side c is rewritten to f. As a result, the outline connection information DC and the virtual connection information of the outline E1 are as shown in FIG.

Since the contour side d is not included in the contour line E1 by adding the pixel of interest this time, the connection state of the contour side d is deleted from the contour side connection information DC. As a result, the outline connection information DC and the virtual connection information of the outline E1 are as shown in FIG.

Then, the connection state of the outline sides a, b, and c excluding the outline side d from the virtual connection information is copied to the outline connection information DC, so that the outline connection information DC of the outline E1 and the virtual connection information are obtained. Is as shown in FIG. In the contour line connection information DC of FIG.
The connection state of the outline E1 as shown by the bold line in (b) is described. Therefore, the virtual connection information may be deleted from the memory 50 when the processing up to this point is performed.

Next, when the four contour sides of the target pixel are included in two or more existing contour lines, the processing is almost the same as that described above, but there are some differences. For example, FIG. 16 is a diagram illustrating a case where four contour sides of a target pixel are included in three existing contour lines. In FIG. 15, the hatched pixels are the target pixels, the thin lines are the outline sides, and the bold lines are the outline sides included in the outline. FIG.
In (a), contour sides e, d, f, and g are included in contour line E1, contour sides t, a, and s are included in contour line E2, and contour sides m, c, and n are contour lines. It is included in line E3. In the contour line E1, each contour side is “e → d → f → g”.
In the contour line E2, each contour side is connected in the order of “t → a → s”, and in the contour line E3, each contour side is connected in the order of “m → c → n”. Have been.
In such a state, if you add the pixel of interest indicated by diagonal lines,
As shown by the thick line in FIG. 14B, the contour lines E2 and E3 are integrated with the contour line E1 and disappear.

When the contours are integrated, the contour information updating unit 40b transmits the contour management information D for each of the contours E1, E2 and E3.
With reference to M, the number of contour sides forming each contour line is acquired (see FIG. 4B). Then, only the outline having the largest number of outline sides is left, and the other outlines are deleted. For example,
Assuming that the contour having the largest number of contour sides in FIG. 16A is E1, the result of updating the contour is as shown in FIG.
As shown in (b), only the outline E1 remains, and the other outlines E2 and E3 have disappeared.

FIG. 17 shows contour line connection information in the state of FIG. 16 (a). FIG. 17A shows contour line connection information DC, and FIG. 17B shows a case where a contour line is formed from four contour sides of the pixel of interest and is temporarily stored in the memory 50. FIG. 17C shows a virtual connection state of the contour side of the target pixel, and FIG.
It is. In FIG. 17C, the columns of the starting side number and the starting density value store the number of the contour side and the density value of the pixel of interest when the respective contour lines E1 to E3 are generated. Here, these values are indicated by "-" for convenience.

By adding the pixel of interest indicated by oblique lines in FIG. 16A, the contour sides a, c, and d are not included in the contour line. Therefore, in the contour line connection information DC in FIG. 17A, the next contour side number for the contour side t with the contour side a as the next contour side (connection destination) is updated. That is, referring to the virtual connection state in FIG. 17B, since the contour side a is connected to the contour side b,
The next contour side number for the contour side t is rewritten to b.

Next, as shown in FIG. 17C, since the number of contour sides of the contour line E1 is the largest, the contour lines E2 and E3 disappear. Therefore, the belonging contour numbers E2 and E3 in the contour connection information DC in FIG. 17A are all rewritten to E1.

Next, since the contour side a is not included in the contour line, in the virtual connection state of FIG. 17B, the contour side d is set to the next contour side (connection destination). The next contour side number is updated. That is, referring to the contour line connection information DC, since the contour side a is connected to the contour side s, the next contour side number for the contour side d is a
To s. Since the contour side d is not included in the contour, the next contour side e with the contour side d as the next contour side (connection destination) in the contour line connection information DC of FIG. The contour side number is updated. In other words, referring to the virtual connection state,
Since the contour side d is drawn so as to be connected to the contour side s, the next contour side number for the contour side e is rewritten from d to s.

Next, since the contour side c is not included in the contour, the contour side m in which the contour side c is the next contour side (connection destination) in the contour line connection information DC of FIG.
Will be updated. That is, referring to the virtual connection state, since the contour side c is connected to the contour side d, the next contour side number for the contour side m is c
To d. However, since the contour side d is not included in the contour, the contour side f to which the contour side d is connected is set as the next contour side number for the contour side m in the contour line connection information DC.

Next, since the contour side c is not included in the contour line, in the virtual connection state of FIG. 17B, the next contour side of the contour side b with the contour side c as the next contour side The number will be updated. That is, referring to the contour line connection information DC, since the contour side c is connected to the contour side n, the next contour side number of the contour side b in the virtual connection state is rewritten from c to n.

Next, since the contour side d is not included in the contour line, the contour side e in which the contour side d is set as the next contour side (connection destination) in the contour line connection information DC of FIG.
The next contour side number for
To s. Since the contour side c is not included in the contour line, the contour line connection information DC shown in FIG.
, The next contour side number of the contour side m with the contour side c as the next contour side is updated from c to f. Note that this processing has already been performed once, but the same processing is performed again here to obtain the four contour sides a,
The same result can be obtained even if the process of rewriting the connection state of b, c, d is started from any contour side.

Next, since the contour sides a, c, and d are not included in the contour line, the connection information on the contour sides a, c, and d in the contour line connection information DC of FIG. to erase. Then, the connection state of only the outline side b in the virtual connection state is written in the outline connection information DC. In addition, since the contour lines E2 and E3 disappear by this processing,
In the contour line management information DM, a density value that is one higher than the density value of the pixel of interest is written in the end density value column for the contour lines E2 and E3, and the number of contour sides for these contour lines is set to 0. The effective density range for the contour lines E2 and E3 is determined, and the end processing is performed for the contour lines E2 and E3. Also, in the contour management information DM, the contour E
Update the number of contour sides for one. When this process is performed, the virtual connection state of the target pixel is deleted from the memory 50.

As a result of such processing, the outline connection information DC stored in the memory 50 becomes as shown in FIG. 18A, and the outline management information DM becomes as shown in FIG. 18B. . That is, these pieces of information indicate a state in which the contour line E1 as shown in FIG. As a result of the processing as described above, the contour line E1 becomes the contour side 16
The outlines E2 and E3 have been updated to the outlines composed of the individual pieces, and the outlines E2 and E3 have been erased by performing the end processing.

Next, two of the four contour sides of the pixel of interest are
A case where the above-described contour sides are included in the same contour line will be described. First, before performing the above processing, the contour number to which the four contour sides of the target pixel belong is acquired, and the contour number included in the same contour line among the four contour sides of the target pixel is obtained. Get the side number. Then, it is determined whether or not the connection states of the contour sides included in the same contour line among the contour sides of the target pixel are continuous. If the connection state of the contour sides included in the same contour is continuous, the contour is appropriately updated by performing the above-described normal processing.
However, if the connection states of the contour sides included in the same contour are not continuous, a hole is formed inside the contour, and a new contour is generated for the hole. .

For example, if a pixel indicated by oblique lines is extracted as a pixel of interest when a contour line as shown in the left diagram of FIGS. 19A to 19D is formed, a contour line as shown in the right diagram is obtained. Is generated. In FIGS. 19A to 19D, circles indicate the start sides of the respective contour lines. As a result of performing the above-described update processing of the contour line connection information DC, if a hole-shaped contour line that newly forms a closed loop is generated inside the existing contour line, the start edge of the contour line is determined. , The starting density value and the number of contour lines, and
Registration is performed. By performing such processing, it is possible to appropriately cope with a case where a contour is separated and a new contour is generated.

Next, a case will be described in which there is a contour side set as the start side of the existing contour line among the four contour sides of the target pixel. First, when it is determined that there is a contour side set as the start side of the existing contour line E1 among the four contour sides of the target pixel, an area for writing information of the new contour line E2 in the contour line management information DM is secured. The contents of the existing contour line E1 are copied to the area. And contour line E
The end processing is performed on the contour line E2 by writing a density value one higher than the density value of the target pixel into the end density value for the contour line management information DM for No. 2 and setting the number of contour sides to 0. Then, the density value of the target pixel is overwritten in the column of the start density value of the outline management information DM for the existing outline E1, and the start side is extracted and overwritten from the outline sides other than the four outline sides of the target pixel. . By performing such processing, it is possible to satisfactorily update the contour line information even when there is a contour side set as the start side of the existing contour line among the four contour sides of the target pixel. .

However, as shown in the left diagram of FIG. 20, when all of the four contour sides of the target pixel are included in the same existing contour line, of the four outline sides of the target pixel, Even when there is a contour side set as the start side, it is not necessary to perform the above processing, and the end processing may be simply performed on the existing contour line. As a result, the contour is updated to an appropriate contour as shown in the right diagram of FIG.

In the above description, the outline information updating unit 40b
Has conceptually shown a process of updating the outline connection information DC and the outline management information DM. Here, in order to make the contents of the above processing more understandable, a processing procedure when the above processing is performed on the original image and the framed image shown in FIG. 5 will be examined. FIGS. 21 to 30 are diagrams showing the outline management information DM and the outline connection information DC when extracting the outline for each density value. 21 to FIG.
In (a) of 0, the number of each pixel indicates the density value of each pixel of the original image portion, and the density value of the density value 0 of the frame portion is omitted. In the following description, the contour side number shown in FIG. 7 is used to refer to the contour side of each pixel, and the coordinate values shown in FIG. 8 are used to refer to each pixel.

First, the pixel-of-interest extraction unit 20 shown in FIG.
The coordinate value 9 of the memory address 19 which is the pixel having the maximum density value is obtained from the buffer area sorted as shown in FIG. Referring to the coordinate values in FIG. 8, the pixel having the density value 9 is extracted as the target pixel as shown in FIG. As shown in FIG. 21A, since the four outline sides of the target pixel are not included in the existing outline, an outline composed of the four outline sides of the target pixel is generated, and the outline management information DM and the outline The information is described in the connection information DC.

In the outline management information DM, since the outline newly generated by the four outline sides of the target pixel is the outline generated first, the outline number is 1.
Further, since the density value of the pixel having the coordinate value 2 (above the target pixel) among the neighboring pixels existing through the four contour sides of the target pixel is 0, the contour side above the target pixel is the start side.
Since the contour side number of this contour side is 4, 4 is stored as the start side number. Since the density value of the target pixel is 9 at this time, 9 is stored as the start density value, and 4 is stored as the number of contour sides.

In the outline connection information DC, the connection state of the outline formed by the four outline sides of the target pixel is described, and 1 is stored as the belonging outline number of each outline side.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
When the coordinate values 22 and 18 of the memory addresses 18 and 17 in the buffer area shown in FIG. 2B are obtained, and these pixels are set as a target pixel and a contour line is formed for the density value 8, the result is as shown in FIG. As shown in FIG.
Since the outline sides of the two pixels are not included in the already generated outline of the density value 9, a new outline is formed for each pixel. Then, the outline management information DM and the outline connection information DC are respectively shown in FIG.
The result is as shown in FIG. Since the pixel having the coordinate value 22 is first processed as the pixel of interest, the outline number of the outline formed by the four outline sides of the pixel having the coordinate value 22 is 2, and the four pixels having the coordinate value 18 are four. The contour number of the contour formed by the contour sides is 3.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
When the coordinate values stored in the memory addresses 16 to 13 of the buffer area in (b) are sequentially acquired, and these pixels are set as a target pixel, and a contour line is formed for the density value 7,
As shown in FIG. As shown in FIG.
The contour side above the pixel having the coordinate value 16 out of the four pixels having the density value 7 is a contour line having a density value 9 already generated (contour line number 1).
, The outline connection information DC and the outline management information DM for the outline number 1 are updated. In addition, since each contour side of the other pixels is not included in the existing contour line, a new contour line is formed for each pixel. As a result, the outline management information DM and the outline connection information DC are as shown in FIGS. 23B and 23C, respectively.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
(B) The coordinate value 30 stored in the memory address 12 of the buffer area is obtained, and this pixel is set as a target pixel.
When the contour line is formed for the density value 6, the result is as shown in FIG. As shown in FIG. 24A, the right contour side of the four contour sides of the pixel having the density value 6 is included in the already generated contour line having the density value 7 (contour line number 5). The outline connection information DC and the outline management information DM for the outline number 5 are updated. As a result, the outline management information DM and the outline connection information DC are respectively shown in FIG.
(B) and (c) are obtained.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
FIG. 25 shows a case where the coordinate values 32 and 24 stored in the memory addresses 11 and 10 of the buffer area in (b) are acquired, and these pixels are set as a target pixel and a contour line is formed for the density value 5. Become like As shown in FIG. 25A, the lower contour side of the pixel having the coordinate value 24 among the two pixels having the density value 5 is included in the already generated contour line (contour line number 5). For the pixel having the coordinate value 32, the left contour side is included in the already generated contour (contour line number 5), and the right contour side is already generated in the contour line (contour line number 4). ) Included. Here, when the numbers of the contour sides of the contour numbers 4 and 5 are compared, the contour of the contour number 4 is integrated with the contour of the contour number 5 because the contour number 4 is smaller. As a result, the end processing is performed on the outline management information DM for the outline number 4, the density value 6 is written in the end density value column, and the number of outline sides is updated to zero. Also, the outline management information DM and the outline connection information DC for the outline number 5 are updated. As a result, the two pixels having the density value 5 are included in the contour of the contour number 5, and the contour management information DM and the contour connection information DC are shown in FIGS. 25B and 25C, respectively. Become like

Next, the pixel-of-interest extraction unit 20 performs the processing shown in FIG.
When the coordinate values 29, 17, and 11 stored in the memory addresses 9 to 7 of the buffer area in (b) are acquired, these pixels are sequentially set as a target pixel, and a contour line is formed for a density value of 4. 26. As shown in FIG. 26A, the contour side on the right side of the pixel having the coordinate value 29 is included in the contour line of the contour number 5, and the upper contour side is included in the contour line of the contour number 2. I have. Therefore, the contour of contour number 2 is integrated with the contour of contour number 5 and disappears.
The contour side on the right side of the pixel having the coordinate value 17 is contour number 3
, And the lower contour side is contour number 5
And the left contour side is contour number 1
Are included in the outline. Therefore, the contours of contour numbers 1 and 3 are integrated with the contour of contour number 5 and disappear.
The contour side on the right side of the pixel having the coordinate value 11 is contour number 6
, And the lower side of the contour is included in the contour of contour number 5 that is generated by being integrated earlier. Therefore, the contour of contour number 6 is integrated with the contour of contour number 5 and disappears. When the three pixels having the density value 4 are processed as the target pixel in this way, the outline management information DM and the outline connection information DC are respectively shown in FIG.
The result is as shown in FIG.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
When the coordinate values 25 and 15 stored in the memory addresses 6 and 5 in the buffer area of (b) are acquired, and these pixels are sequentially set as a target pixel, and a contour line is formed for the density value 3, FIG. As shown. As shown in FIG. 27A, the upper, lower, and left contour sides of the pixel having the coordinate value 25 are included in the contour line with the contour number 5. Therefore, the coordinate value 2
The outline of outline number 5 is updated so that the pixel of 5 is included in the outline of outline number 5. The right and lower contour sides of the pixel having the coordinate value 15 are included in the contour line having the contour number 5, but the connection state is not continuous. Therefore, the process of updating the pixel having the coordinate value 15 so as to be included in the contour of the contour line number 5 is a separation process, and a new contour line (contour line number 7) is placed inside the contour line of the contour line number 5. ) Is formed. When the two pixels having the density value 3 are processed as the target pixel in this manner, the outline management information DM and the outline connection information DC are as shown in FIGS. 27B and 27C, respectively.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
When the coordinate values 23, 19, and 8 stored in the memory addresses 4 and 2 of the buffer area in (b) are acquired, these pixels are sequentially set as a target pixel, and a contour line for the density value 2 is formed. As shown in FIG. As shown in FIG. 28A, all the outline sides of the pixel having the coordinate value 23 are included in the outline of the outline number 7, and the start side of the outline is included. Therefore, the end processing is performed on the contour line of contour number 7. Also, above the pixel having the coordinate value 19,
Since the outline on the left side is included in the outline of outline number 5, the outline connection information DC and outline management information DM for outline number 5 are updated. Since the right and lower contour sides of the pixel having the coordinate value 8 are included in the contour of the contour number 5, the contour connection information D for the contour number 5 is included.
C and the outline management information DM are updated. As a result, the outline management information DM and the outline connection information DC are as shown in FIGS. 28B and 28C, respectively.

Next, the pixel-of-interest extraction unit 20 operates as shown in FIG.
When the coordinate values 26 and 10 stored at the memory addresses 1 and 0 in the buffer area of FIG. 2B are acquired, and these pixels are sequentially set as a target pixel, and a contour line is formed for the density value 1, FIG. As shown. As shown in FIG. 29A, since the contour side excluding the right side of the pixel having the coordinate value 26 is included in the contour of the contour number 5, the contour connection information DC and the contour of the contour number 5 are included. The management information DM is updated. Further, since the contour side excluding the upper side of the pixel having the coordinate value 10 is included in the contour of the contour number 5, the contour number 5
Is updated with respect to the outline connection information DC and the outline management information DM. As a result, the outline management information DM and the outline connection information DC are as shown in FIGS. 29B and 29C, respectively.

Finally, in the processing for the density value 0, when the density value 0 is used as the threshold value for extracting the contour, the extracted contour line is the outer peripheral portion of the original image. Therefore, for the density value 0, it is sufficient to output a contour line connecting the outer peripheral portion of the original image without particularly performing a process of extracting a pixel of interest and forming a contour line for each pixel. For the density value 0, the end processing is performed on the outline management information DM for each outline. FIG. 30 shows the result of the end processing.

The processing described above will be briefly described as follows. In the image, the pixel of interest is extracted one pixel at a time in descending order from the pixel having the maximum density value. And
If the four outline sides around the target pixel are not included in the existing outline, an outline composed of the four outline sides is set as a new outline, and an outline connection indicating the connection state of the new outline is set. Generate information. At this time, contour management information including a start side of the new contour and a start density value where the density value of the target pixel is set as the start density of the effective density range of the new contour is generated. On the other hand, if any of the four contour sides of the target pixel is included in the existing contour, the contour connection information and the contour management information for the existing contour are updated. If at least one existing contour line that includes any one of the outline sides of the target pixel disappears by the update, the density value of the target pixel is added to the outline management information for the existing contour line that disappears. Is stored as an end density value indicating the end density of the effective density range of the existing contour line.

By performing such processing, when all the pixels having the same density value are processed as the target pixel,
The contour line connection information DC stores the contour line of the density value. Therefore, for example, when it is desired to output a contour line for the density value 8, if all the pixels indicating the density value 8 are processed as the pixel of interest, the contour line connection information DC is output and the desired density value 8 is output. Contour line is obtained,
It is not necessary to process pixels having a density value of 7 or less. When it is desired to output the contour lines for all the density values, the contour line connection information DC is output every time the processing of all the pixels indicating each density value is performed. It is possible to obtain contour lines of all density values only by extracting and processing pixels one by one.

In this embodiment, when the contour line is formed for each density value, the contour line management information DM is generated / updated. Is completed, the contour line connection information DC is stored in the memory 50.
Even if it is erased from, if the outline management information DM is stored, the outline for an arbitrary density value can be extracted later.

<5. Contour Line Extraction> Next, after performing processing for forming a contour line while extracting the noted pixel one by one as described above, the contour line for each density value is extracted based on the contour line management information DM. The extraction process will be described.
This processing is performed in the contour extraction unit 60 of FIG.

The contour extracting section 60 refers to the contour management information DM stored in the memory 50, finds a starting edge of an effective contour at a density value to be extracted, and determines a predetermined rule (rule) from the starting edge. ) To extract a contour having a predetermined density value by tracing the contour.

Here, rules for extracting a contour line will be described. FIG. 31 is a diagram illustrating a rule for specifying the traveling direction of the start side. The start side may be located along the main scanning direction X (ie, the horizontal direction) or may be located along the sub-scanning direction Y (ie, the vertical direction). When one start side is specified, the traveling direction of the start side is determined. For example, assuming that the density values of two pixels existing on both sides of the start side are a and b, when the start side is located in the vertical direction, the density value a of the right pixel is larger than the density value b of the left pixel. If it is small, or if the start side is located in the horizontal direction and the density value a of the upper pixel is smaller than the density value b of the lower pixel, as shown in FIG.
The traveling direction of the start side is set upward or rightward. On the other hand, when the start side is located in the vertical direction and the density value a of the right pixel is larger than the density value b of the left pixel, or when the start side is located in the horizontal direction and When the density value a of the pixel is larger than the density value b of the lower pixel, the traveling direction of the start side is set downward or leftward as shown in FIG.

Next, FIG. 32 is a diagram showing a rule for specifying a traveling direction when a contour is traced and formed. FIG.
(A) shows an arrow whose traveling direction has already been determined.
Here, assuming that the density value to be extracted is a, the density value of the left pixel in front of the arrow is b, and the density value of the right pixel in front of the arrow is c, then “a ≦ b and a ≦ c” FIG. 32
32B, the course is taken in the left direction. If "a> b and a≤c", the course is taken in the straight direction as shown in FIG. 32 (c), and if "a>c", the course is taken in FIG. As shown in (d), take the course to the right. By setting such a rule, a pixel larger or equal to the density value to be extracted is always obtained on the right side with respect to the traveling direction at the time of contour extraction, and a pixel smaller than the density value to be extracted is displayed on the left side. Is always obtained. Therefore, if the contour side is traced based on the rule as described above, a contour line having a desired density value can be extracted.

An example of actually extracting a contour line having a density value of 3 based on the contour line management information DM obtained for the original image of FIG. 5 will be described below. First, FIG. 33 shows the effective density range for each contour in the contour management information DM of FIG. 30B obtained for the original image of FIG.
In FIG. 33, the contour numbers 5 and 7 include the density value 3 in the effective density range. Therefore, contour number 5,
Referring to the outline management information DM of FIG. 30B for No. 7, the start side numbers are 62 and 45, respectively. When the start side is specified from the contour side numbers allocated as shown in FIG. 7 and the contour side is traced from the start side based on the above rule, the result is as shown in FIG. FIG. 34A shows a contour extracted from the start side of the contour side number 62, and FIG.
4 (b) is a contour line extracted from the start side of the contour side number 45. Then, when the two outlines shown in FIGS. 34A and 34B are combined, an outline having a desired density value 3 is obtained.

The contour extracting section 60 extracts the contour from the start side in this way and outputs the contour. Therefore,
When the contour extraction unit 60 outputs a contour, it is not necessary to scan an image for each pixel, and the contour can be output efficiently. That is, once the contour line management information DM is generated, the contour extraction processing for an arbitrary density value can be efficiently performed by using the information, and the processing time can be reduced.

<6. Processing Sequence> Next, a description will be given of a processing sequence when the above-described processing for generating / updating the outline connection information DC and the outline management information DM is performed by a computer or the like. 35 to 38 are flowcharts showing a processing sequence for forming a contour line for each density value by a computer or the like.

First, in step S10, preprocessing is performed on the original image. That is, in this preprocessing, the generation of the framed image, the assignment of the contour side numbers, and the sorting of the pixels based on the density value are performed as described above.

Next, in step S11, a pixel of interest is extracted. The pixel of interest is extracted one pixel at a time in descending order of the density value from the pixel having the maximum density value based on the sorting result of step S10.

Then, in step S12, step S
It is determined whether four contour sides of the target pixel extracted in 11 are included in the existing contour line. This judgment is
This is performed by referring to the already generated contour line connection information DC. If none of the four contour sides of the target pixel is included in the existing contour line, “N
O ”, the process proceeds to step S13, and the target pixel 4
If any one of the two outline sides is included in the existing outline, “YES” is determined and the process proceeds to step S14.

When the process proceeds to step S13, a new outline composed of four outline sides of the target pixel is generated, and outline connection information DC and outline management information DM are generated for the new outline. Then, when the process of step S13 is performed, the process proceeds to step S41 described later (connector A).

When the process proceeds to step S14, the assigned contour number indicating the contour including the contour side of the target pixel is obtained based on the contour connection information DC. At this time, if two or more contour sides of the four contour sides of the target pixel are included in the existing contour lines, the respective belonging contour numbers are acquired. Then, when the process of step S14 is performed, the process proceeds to step S15.

Then, in step S15, step S
The belonging contour number acquired in 14 is verified, and it is determined whether or not there is a contour side included in the same contour out of the four contour sides of the target pixel. That is, when the belonging contour numbers are acquired for each of the two or more contour sides included in the existing contour out of the four contour sides of the target pixel, there are contour sides indicating the same belonging contour numbers. In this case, “YES” is determined, and in other cases, “NO” is determined. If “YES” is determined, the process proceeds to step S16, where the connection state of the contour sides included in the existing contour line is stored and stored in a memory or the like, and the process proceeds to step S17. If "NO" is determined, the process directly proceeds to step S17.

In step S17, it is determined whether or not there is a contour side registered as the start side of the existing contour line among the four contour sides of the target pixel. This determination is performed by referring to the already generated contour line management information DM and verifying whether or not the contour side numbers of the four contour sides of the target pixel are registered as the start side numbers of the existing contour lines. Will be If there is a contour side registered as the start side of the existing contour, “YES” is determined and the process proceeds to step S18. If there is a contour side registered as the start side of the existing contour, It is determined as "NO" and the process proceeds to step S21 (connector C).

In step S18, it is determined whether or not the existing contour including the contour side of the target pixel is composed of only four contour sides of the target pixel. If “NO” is determined here, the process proceeds to step S19, and if “YES” is determined, the process proceeds to step S20.

When the start side is included in the contour side of the target pixel, it is necessary to update the start side of the contour line. The reason for this is that processing the target pixel invalidates the start side included in the contour side of the target pixel. For this reason, when the start side is included in the contour side of the target pixel, a new contour is generated, and the new contour inherits the contour connection information DC of the previous contour. Since the start side is not registered in the outline management information DM about the new outline, one outline side on the new outline (however,
A contour side that is not in contact with the pixel of interest) is selected as a start side. The start density value of the new contour is set as the density value of the pixel of interest. Then, the end processing is performed on the contour lines before that. However, in practice, it is inefficient to change the information of the inherited new contour line. Therefore, in this embodiment, the following processing is performed in step S19.

An area for writing new outline information is secured in the outline management information DM, and the contents of the previous outline in which the invalid start side is registered are copied to the area (however, the outline number Is different). Then, the density value of the copied contour management information DM is set to 1
By writing the next higher density value to the end density value and setting the number of contour sides to 0, the end processing is performed on the generated new contour line. On the other hand, the density value of the current target pixel is overwritten in the column of the start density value of the contour management information DM for the existing contour in which the invalid start side is registered, and the start side is set to the four contours of the target pixel. Extract from contour side other than side and overwrite. By performing such processing, the contents of the contour line in which the invalid start side is registered can be taken over, and a new valid start side can be set efficiently. As a result, even if there is a contour side set as the start side of the existing contour line among the four contour sides of the target pixel, the contour line information can be satisfactorily updated. Then, after the process of step S19 is performed, the process proceeds to step S21 (connector C).

Further, when the start side is included in the contour side of the target pixel and the contour is composed of only four contour sides of the target pixel, for example, as shown in FIG. This is the case. In this case, the end processing may be performed on a contour line including only four contour sides of the target pixel. Therefore, in step S20, the end processing is performed on the contour line including the contour side of the target pixel. Then, after the process of step S20 is performed, the process proceeds to step S41 described later (connector A).

Next, in step S21, with reference to the outline management information DM, the outline having the largest number of outlines among the outlines including the outline of the target pixel is determined, and the outline of the outline is determined. Get the line number.

Then, in step S22, the contour number belonging to the contour including the contour side of the target pixel in the contour connection information DC is rewritten to the contour number acquired in step S21. Next, in step S23, a virtual connection state of the four contour sides of the target pixel is generated and held.

In step S24, one of the four contour sides of the pixel of interest is selected from the contour lines included in the existing contour line. In step S25, the contour side selected with reference to the contour line connection information DC is selected. The contour side registered at the next contour side number is detected. Then, in step S26, the next contour side connected to the contour side selected in step S24 from the virtual connection state is detected. Then, in step S27, it is determined whether or not the contour side detected in step S26 is included in the existing contour. If not, “NO” is determined and the process proceeds to step S28.
If it is included, “YES” is returned and step S29 is performed.
Proceed to.

In step S28, the contour side number detected in step S26 is stored in the contour side number next to the contour side detected in step S25. On the other hand, step S29
Then, referring to the contour line connection information DC, the next contour side to be connected to the contour side detected in step S26 is detected,
This contour side is defined as the contour side next to the contour side detected in step S25.

In step S30, the contour side which is the connection destination of the contour side selected in step S24 is detected with reference to the contour line connection information DC. Further, in step S31, the contour side in which the contour side selected in step S24 is registered as the next contour side is detected with reference to the virtual connection state.

Then, in step S32, it is determined whether or not the contour side detected in step S31 is included in the existing contour side. If not, "NO" is determined and the process proceeds to step S33 to include the contour side. "YE
S ", and proceeds to step S34.

In step S33, the contour side number detected in step S30 is stored in the contour side number next to the contour side detected in step S31. On the other hand, step S34
Then, with reference to the contour line connection information DC, a contour side having the contour side detected in step S31 as the next contour side is detected, and the contour side registered as the next contour side of this contour side is determined in step S30. Is the contour side detected in.

In the processing of steps S24 to S34, the update processing of the connection state of the outline side is completed for one outline side of the target pixel included in the existing outline.
Then, in step S35, it is determined whether or not there is another contour side included in the existing contour line among the four contour sides of the target pixel. In the case of "YES", the same processing is performed again on the contour side. The process returns to step S24 (connector E), and if "NO", the process proceeds to step S36 (connector F).

In step S36, it is determined whether or not there is a connection state of the outline stored in step S16. If there is a stored connection state, the determination is "YES" and the process proceeds to step S37. If there is no stored connection state, the determination is "NO" and the process proceeds to step S41.

In step S37, the stored connection state is read, and two contour sides included in the same contour are extracted. Then, in step S38, it is determined whether or not the connection state of these two contour sides is continuous. If not continuous, for example, as shown in FIG. 19, since a hole-shaped contour is formed inside the existing contour,
Proceed to step S39. On the other hand, if they are continuous, a hole-shaped contour is not formed, and the process proceeds to step S40.

In step S39, a starting side is registered for a hole-shaped contour formed inside the existing contour.
Set as a new contour line. Then, the process proceeds to step S40.

In step S40, when extracting two contour sides included in the same contour line, it is determined whether or not there is another combination. If there is another combination, a hole shape is determined for those contour sides. The process returns to step S37 again to check whether or not a contour line is formed. If there is no other combination, “NO” is determined and the process proceeds to step S41.

The processing for the pixel of interest extracted by the processing of steps S11 to S40 has been completed, and in step S41, it is determined whether or not there is a pixel to be processed as the pixel of interest next, by storing the result of sorting in the memory. The determination is made based on the address, and if there is a next pixel, “YES” is returned to step S11 (connector G). When the process for all the pixels is completed, “NO” is determined, and the process proceeds to step S42.

In step S42, since there are no more target pixels to be extracted, the end density value "0" is stored for all the outlines for which the end density values are not stored in the outline management information DM at this time. . That is, end processing is performed on all contour lines that have not been subjected to end processing. After the end processing is performed, the process proceeds to step S43.

Then, in step S43, the processing sequence ends by storing the outline management information DM generated / updated by the above processing.

By performing the above processing, the outline management information DM from which the outline for each density value can be extracted is obtained. In the case where the contour line for each density value is output in the above-described processing, when the target pixel is extracted in step S11, the density value of the target pixel is checked, and if the target pixel is different from the previous density value. For example, the configuration may be such that the contour line connection information DC at that time is output.

As described above, if the contour extraction of the image is performed in the processing form described in this embodiment, the contour extraction processing for an arbitrary density value can be efficiently performed, and the processing time can be reduced. It is already clear what can be done.

<7. Modified Example> In the above-described processing, the processing has been mainly described by exemplifying the processing for an image of 10 gradations having a density value of 0 to 9. However, the present invention is not limited to this. Needless to say, it is applicable to

Next, in the above description, in order to detect that a hole-shaped contour is newly formed inside the existing contour, it is detected whether or not the connection state of the contour sides is continuous. Was. However, it is also possible to simply detect whether or not a new hole-shaped contour line is formed by simply detecting the pattern of the image.

Next, a general computer having a display unit, a keyboard, a CPU, a memory, and the like executes a predetermined program by using the respective processing units constituting the image contour extracting apparatus 100 shown in FIG. 2 described in the above embodiment. It may be realized by executing. In this case, the original image is stored on a magnetic disk or the like, and the CP
U executes the image contour extraction program for performing the procedures shown in FIGS. 35 to 38, whereby the contour lines for each density value are sequentially formed, and the contour line connection information DC and the memory are stored in the memory. Contour line management information DM is sequentially generated / updated. When the computer performs the above-described processing, the time for the contour extraction processing by the computer is reduced. Note that the contour extraction program executed by the computer is recorded and stored on a portable recording medium such as a CD-ROM or a flexible disk or a fixed recording medium such as a magnetic disk provided in the computer. The program may read and execute a contour extraction program from a recording medium.

[0142]

As described above, according to the first aspect of the present invention, a pixel of interest is extracted one by one in descending order from the pixel having the maximum density value in the image, and the contour connection information is extracted. In the process of updating the outline management information, an outline is formed for each density value. For this reason, when extracting some contour lines for different density values,
The process of extracting all the pixels constituting the image as the pixel of interest need only be performed once. Therefore, it is possible to efficiently perform the contour extraction processing for an arbitrary density value, and to shorten the processing time. In addition, since the start side is included in the outline management information, the outline management information can be used when the outline of an arbitrary density value is extracted later.

According to the second aspect of the present invention, if pixels having the same density value in an image are processed as a pixel of interest, a contour line having that density value is obtained, so that the contour extraction processing can be performed efficiently. And the processing time can be shortened.

According to the third aspect of the present invention, it is possible to extract a contour line having a predetermined density value based on the stored contour line management information. Does not need to be generated. Therefore, the contour extraction processing can be performed efficiently, and the processing time can be reduced.

According to the fourth aspect of the present invention, pixels constituting an image can be efficiently rearranged in descending or ascending order of density value. As a result, the contour extraction processing can be performed efficiently, and the processing time can be reduced.

According to the fifth aspect of the invention, the pixel of interest is extracted one pixel at a time in descending order from the pixel having the maximum density value in the image, and the outline connection information and the outline management information are updated. In the process, the contour line is formed for each density value. For this reason, even when extracting some contours with different density values, the process of extracting and extracting all the pixels constituting the image as the pixel of interest may be performed only once. Therefore, it is possible to efficiently perform the contour extraction processing for an arbitrary density value, and to shorten the processing time.

According to the sixth aspect of the present invention, when the computer executes the predetermined image outline extraction program, the computer can efficiently extract the outline of the image and reduce the processing time. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a concept of generation / update of a contour line according to the present invention.

FIG. 2 is a block diagram showing a configuration of an image contour extraction device as one embodiment of the present invention.

FIG. 3 is a diagram illustrating contour line connection information.

FIG. 4 is a diagram illustrating contour line management information.

FIG. 5 is a diagram illustrating generation of a framed image.

FIG. 6 is a diagram illustrating assignment of contour side numbers.

FIG. 7 is a diagram showing contour side numbers for a 7 × 6 framed image.

FIG. 8 is a diagram illustrating coordinate values of respective pixels in a 7 × 6 framed image.

FIG. 9 is a diagram showing a result of counting the number of pixels for each density value in an original image.

FIG. 10 is a diagram showing the cumulative number of pixels for each density value.

FIG. 11 is a diagram illustrating a sorting process based on a density value.

FIG. 12 is a diagram illustrating a sorting process based on a density value.

FIG. 13 is a diagram showing a cumulative pixel count and a buffer area for each density value on which a sort process has been performed.

FIG. 14 is a diagram illustrating a case where four contour sides of a target pixel are included in one existing contour line.

FIG. 15 is a diagram illustrating a process of updating the contour E1 of FIG. 14A to the contour E1 of FIG. 14B.

FIG. 16 is a diagram illustrating a case where four contour sides of a target pixel are included in three existing contour lines.

FIG. 17 is a diagram showing contour line connection information in the state of FIG.

FIG. 18 is a diagram illustrating an example of contour line connection information.

FIG. 19 is a diagram illustrating an example of a case where a hole-shaped contour is formed.

FIG. 20 is a diagram illustrating an example of a case where a contour line disappears.

FIG. 21 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 22 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 23 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 24 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 25 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 26 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 27 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 28 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 29 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 30 is a diagram showing outline management information and outline connection information when extracting an outline for each density value.

FIG. 31 is a diagram showing a rule for specifying a traveling direction of a start side.

FIG. 32 is a diagram showing a rule for specifying a traveling direction when tracking and forming an outline.

FIG. 33 is a diagram showing an effective density range for each contour line in the contour line management information.

FIG. 34 is a diagram illustrating a process of tracing a contour side from a start side based on a rule.

FIG. 35 is a flowchart showing a processing sequence for forming a contour line for each density value by a computer or the like.

FIG. 36 is a flowchart showing a processing sequence for forming a contour line for each density value by a computer or the like.

FIG. 37 is a flowchart showing a processing sequence for forming a contour line for each density value by a computer or the like.

FIG. 38 is a flowchart showing a processing sequence for forming a contour line for each density value by a computer or the like.

[Explanation of symbols]

 Reference Signs List 10 preprocessing unit 20 target pixel extraction unit 30 contour side determination unit 40 contour formation unit 40a contour line information generation unit 40b contour line information update unit 50 memory 60 contour extraction unit 70 storage unit DM contour line management information DC contour line connection information

Claims (6)

[Claims] 1. A method for extracting a contour of an image, comprising: (a) extracting a pixel of interest one by one in descending order from a pixel having a maximum density value in the image; and (b) extracting a pixel of interest. If a plurality of contour sides surrounding the contour line are not included in the existing contour line, a contour line composed of the plurality of contour sides is set as a new contour line, and contour line connection information indicating a connection state of the new contour line. And the start side of the new contour line in which one of the plurality of contour sides of the target pixel is selected and the density value of the target pixel are set to the start of the effective density range of the new contour line. Generating contour management information including a starting density value as a density; and (c) when any of the plurality of contour sides of the pixel of interest is included in an existing contour, Update the contour connection information for existing contours (D) when at least one existing contour line in which any of the contour sides of the pixel of interest is included by the update disappears, or when there is no pixel of interest to be extracted, Adding a density value of the target pixel as an end density value indicating an end density of an effective density range of the formed contour line to the contour line management information for the formed contour line. Image contour extraction method. 2. The method according to claim 1, wherein the steps (a) to (d) are repeatedly performed by using pixels having the same density value in the image as the pixel of interest. A method for extracting an outline of an image, comprising outputting the updated outline connection information. 3. The method for extracting a contour of an image according to claim 1, wherein: (e) storing the contour management information generated by repeatedly performing the steps (a) to (d); When extracting the contour of the density value of (f), the contour of the predetermined density value based on the effective density range indicated by the start density value and the end density value included in the contour management information Identifying a line, acquiring the start side from the contour management information for the contour, and (g) sequentially extracting contour sides from the start side according to a predetermined rule. A contour extraction method for an image characterized by the following. 4. The method for extracting an outline of an image according to claim 1, wherein the steps performed prior to the steps (a) to (d) include: A step of securing a recording area for recording pixel information for the pixels of (a), (i) searching all the pixels constituting the image, and counting the number of pixels for each density value, (j) Based on the result, for each density value, the step of obtaining the cumulative number of pixels less than the density value; (k) the step of extracting the pixels constituting the image one pixel at a time; (l) the (k) step Detecting the density value of the extracted pixel, acquiring the cumulative number of pixels corresponding to the density value,
Recording the pixel information specifying the extracted pixel at the position of the recording area corresponding to the value of the cumulative number of pixels, and updating the value of the cumulative number of pixels, comprising: And (l) are repeated until all the pixels constituting the image are performed. 5. A device for extracting an outline of an image, comprising: (a) a pixel-of-interest extracting means for extracting pixel-of-interest one pixel at a time in descending order from a pixel having a maximum density value in the image; When a plurality of contour sides around the pixel of interest are not included in the existing contour line, a contour line including the plurality of contour sides is set as a new contour line, and a contour line connection indicating a connection state of the new contour line. Information, and the start side of the new contour line that has selected any one of the plurality of contour sides of the target pixel, and the density value of the target pixel in the effective density range of the new contour line. Contour information generating means for generating contour management information including a start density value as a start density; (c) storage means for storing the contour connection information and the contour management information; (d) Any of the plurality of contour sides of the pixel of interest When the contour line is included in the existing contour line, the contour line connection information stored in the storage unit is updated for the existing contour line, and the contour edge of any of the target pixels is included by the update. If at least one existing contour line that has been deleted disappears, or if there are no more pixels of interest to be extracted, the contour management information stored in the storage unit for the existing contour line is used. Updating means for additionally updating the density value of the pixel of interest as an end density value indicating the end density of the effective density range of the existing contour line. 6. A recording medium storing a program for extracting a contour of an image by a computer, comprising: (a) a target pixel for each pixel in a descending order from a pixel having a maximum density value in the image; (B) when a plurality of contour sides around the target pixel are not included in the existing contour line, the contour line composed of the plurality of contour sides is set as a new contour line; Contour line connection information indicating a connection state of the contour line is generated, and a start side of the new contour line that selects any one of the plurality of contour sides of the target pixel, and a density value of the target pixel. (C) generating contour management information including a start density value that is the start density of the effective density range of the new contour, and (c) any one of the plurality of contour sides of the pixel of interest is an existing contour. Embraced by The procedure of updating the outline connection information for the existing outline, (d) at least one existing outline that includes any of the outline sides of the pixel of interest by the update. In the case of disappearance, or when there is no more target pixel to be extracted, the density value of the target pixel is set to the end density of the effective density range of the existing contour line with respect to the contour management information for the existing contour line. A computer-readable recording medium on which an image contour extraction program for executing the procedure of adding the end density value is indicated.