JPS61143884A - Line extractor - Google Patents

Abstract

PURPOSE:To extract a line having no break by selecting two connecting relations out of plural ones in case >=3 linear picture points exist nearby and deleting other connecting relations for tracking of a line. CONSTITUTION:A single line conversion processor 2 reads a frame memory 1 and rewrites the contents of the memory 1 when >=3 connecting relations exist. A line tracking device 3 reads successively the memory 1 processed by the processor 2 and searches for the picture element having just a single connecting relation. This picture element is defined as a start and also a notice point. If this notice point has a connecting relation, this point is shifted toward the direction having a connecting relation. Then the connecting relation where the notice point is not deleted after shift is checked and the shift of the notice point is repeated. When this repetitive shift is over, the number of recorded direction codes is checked. Then a line is delivered when the number of the direction codes exceeds a certain level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention creates an a picture from an image input by an image input device such as a camera, extracts a coordinate string from the fIJ picture, and draws it with a pen or the like. The present invention relates to an image processing device whose purpose is to draw figures.

Conventional technology Conventionally, as a method for extracting lines from an image, there is a method described in ``On the automatic creation of line drawing representations of figures'' (Information Processing Society of Japan Proceedings 1).
977, P403-P404) J, etc. First, in order to extract lines from an image, the original image input from a camera or the like is made into thin lines. After that, the frame memory in which the thinned image was recorded is sequentially scanned from the upper left, and after finding a pixel that forms a line (hereinafter referred to as #J pixel), the vicinity of that pixel is examined, and if there is a line drawing point nearby. For example, the coordinates of the current point are recorded in a separately prepared table, the current point is deleted from the frame memory, and the process moves to the aforementioned nearby line drawing point. This processing is repeated until the number of unerased line drawing points near the line drawing point is one, and when the number becomes other than that, the repetition of this processing is completed. When it is finished, the number of coordinates recorded in the table is checked, and if it is above a certain value, the extracted line is output as a result, and if it is less than a certain value, it is not output as an unnecessary line. Then erase the records in the table.

Problems to be Solved by the Invention In the conventional method, a line is broken at a position where there are three or more line drawing points in the vicinity of a line drawing point, resulting in a line with many breaks.

Means for Solving the Problem In order to solve this problem, the present invention, when there is a line drawing point that has three or more line drawing points in the vicinity, selects two drawing points from the connection relationship with them using an appropriate selection method. Select the bonding relationship, delete the other bonding relationships and convert them into two bonding relationships, and then trace the line based on the bonding relationship and extract the line.

Function The present invention can extract lines with few breaks by the above-described operation.

Embodiment FIG. 1 is a block diagram of a line extraction device according to an embodiment of the present invention. Reference numeral 1 in FIG. 1 is a frame memory, which records, for each pixel of an image, in which direction of the eight neighborhoods of that pixel a pixel constituting a line drawing exists. This record is 8 bits, and when there is a pixel forming a line drawing in the direction (2) defined in Figure 2, the value of the b-1st bit of this record is set to "1", otherwise it is set to "0". Figure 4 shows an example of the contents of a frame memory for recording connection relationships.Point A has three connection relationships, and point B has two connection relationships.

A blank column represents that the point does not constitute a line, and in reality, the value "0" is written.

Reference numeral 2 in FIG. 1 is a single line processing device which reads the frame memory and rewrites the contents of the frame memory in the following manner when there is a connection relationship between three or more lines. Figure 3 is an example. Point P is a point that has three or more connection relationships. Let Pkl and PF3 be a point advanced by nl pixels and a point advanced by n2 pixels in the direction of the point POk-th connection relationship, respectively. nl x n2. For example, in Figure 3, the direction extending toward the upper right = 1. In the downward extending direction = 2.

1 with the angle ψ. Set ψ to 2. The following evaluation relationship is used for linearity.

1ψ to 1-ψ2+2α to π1+1ψft1-ψ22+
2σ2πI+1ψ to 1−ψ21+(2βkK”)πI
However, 2 for α, α°C, and β are selected from −1, 0, and 1 so that the absolute value of the term containing each is the minimum.

The combination of k and l (k
"ql)" and delete the connection relationships other than the k-th and 1st connections. Deletion of connection relationships is performed for pixel P and another pixel that has the connection relationship to be deleted, and the deletion of these pixels This corresponds to the connection relationship.This is realized by setting the bit of the frame memory to 0.FIG. 5 shows how the connection relationship shown in FIG. 4 is changed after the single-line processing. With the deletion of the connection relationship between points A and B, point A
The 0th pit at point B and the 4th pit at point B are rewritten to "0".

If a point Q with a connection relationship other than 2 is found before reaching a point n2 pixels ahead from point P, use the code string in the direction from point P to Q to divide that code string into n2 pixels. Expand until . The table shows how to expand. Here, N is the length of the direction code string from point P to Q,
dn is the nth direction code of this column. In this embodiment, it is n2-8.

3 in Table 1 is a line tracing device. The line tracing device sequentially reads out the frame memory processed by the single line processing device,
Find a pixel that has only one connection relationship, and use that pixel as the starting point. Record the coordinates of the starting point in a table in the line tracing device, and use the starting point as the point of interest. If the point of interest has a connection relationship, the point of interest is moved in the direction of the connection relationship. Record the direction code of this movement in the table mentioned above. Delete the connection relationship between the point of interest after the movement and the point of interest before the movement, and the connection relationship between the point of interest before the movement and the point of interest after the movement. Next, the connection relationships of the point of interest that have not been deleted after the movement are checked, and the above-described movement of the point of interest is repeated. This repetition is repeated until a point of interest is reached at which, when moving to a new point of interest and deleting the connection relationship with the previous point of interest, no other connection relationship remains. After the above-mentioned repetition is completed, the number of recorded codes is checked, and if the number is above a certain number, it is output as a line, and if it is less than a certain number, it is regarded as an unnecessary line and is not output. The record in the table in the line tracing device is deleted, and the same process is performed by searching for a pixel that will become a newer starting point after the starting point. This is repeated until the end of the frame memory is reached. Next, the frame memory after the above-described processing is read out again from the beginning, and pixels that still have a connection relationship are searched for. If it exists, the connection relationship is always two. One of the two connection relationships is deleted and the above process is performed using that point as the starting point. After the processing, pixels having a connection relationship are searched for after the starting point, and the same processing is performed. Repeat this until the end of frame memory is reached.

Effects of the Invention As described above, according to the present invention, lines with few breaks can be extracted using a frame system that records connection relationships.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the line extraction device of the present invention, FIG. 2 is an explanatory diagram of codes given to the directions of connection relationships, and FIG. 3 is an explanatory diagram of symbols used in the above-mentioned evaluation function. Figure 4 shows an example of the connection relationship, and Figure 6 shows the connection relationship 1 after the connection relationship in Figure 4 has been processed by the single line processing device.
It is. 1...Frame memory, 2...Single line processing device, 3...Line tracing device. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A memory that stores the connection relationship between each pixel constituting an image and neighboring pixels, and reads out the memory and stores 3 pixels per pixel.
Select only two directions from among the connection relationships of pixels that have connections in more than one direction, and delete the connection relationships in other directions.
A line extraction device comprising a single line processing device that converts into a connection relationship below the direction, and a line tracing device that creates a coordinate string by tracing neighboring connection relationships from the results of the processing device. (2) The line extracting device according to claim 1, wherein the single line processing selects the most straight connecting relationship in two directions and deletes the connecting relationships in other directions.