JPH01119874A - Drawing recognizing device - Google Patents

Abstract

PURPOSE:To detect a line cut part and to connect it by obtaining the candidate of the line cut part on a shape line beforehand, discriminating it from a line segment with characteristics for the shape line, and performing a labeling and a propagation processing. CONSTITUTION:Two opening end points to approximate in a prescribed distance are detected, a linear element to be connected to them is registered as the shape line cut candidate, and a shape line cut candidate label is added. Next, the linear element obviously different from the shape line is extracted, and a non-shape line label is added. Next, the processing to propagate the non-shape line label for the linear element to which the label is not added is performed, thereafter, the processing to propagate the shape line cut candidate label for the linear element, to which the label is not added, is performed. Further, based on the characteristics on the lines which the shape line and the non-shape line, the shape line is extracted. Finally, trailing is started from the linear element which is obviously not the shape line, and the linear element to constitute the respective types of symbols is extracted, and the symbol composed of the series of the linear elements which have been extracted is recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for detecting line breaks on shape lines in drawing data in which line figures representing a shape and line figures constituting various symbols for expressing the dimensions of the shape coexist. Even if it is occurring,
The present invention relates to a drawing recognition device that is capable of extracting shape lines that form a loop, and is also capable of extracting and recognizing various symbols for representing the dimensions of shapes.

2. Description of the Related Art Conventional drawing recognition devices extract loop-forming lines from image data of machine parts drawings input through scanners, and also extract various symbols such as dimension lines, dimension extension lines, leader lines, and dashed lines. There is a system to extract and recognize it.

Below, methods for extracting and recognizing shape line loops and various symbols in the conventional example will be described.

(1) Thinning processing is performed on line figures excluding characters in the input image data, and approximate encoding is performed into line elements.

(2) Extract short line elements with open end points and recognize arrow shapes of dimension lines.

(3) From the arrow figure obtained in (2), a dimension line figure is extracted by linearly tracing the line element corresponding to the axis of the arrow.

In this case, the condition for terminating tracking is either reaching the other arrow figure or reaching an open end point.

(4) Extract a straight line element other than an arrow shape whose both ends are open end points, and use this as a dimension extension line.

(5) Among the remaining line elements, line elements constituting a closed figure are extracted as shape lines.

(6) Short line elements having open end points that are connected to the shape line are considered as dashed line candidates, and those that form a pair on a straight line are extracted as dashed lines.

(For example, application to drawing reading device TO8GRAPH5 parts drawings (1), (2) Information Processing Society of Japan 33rd National Conference Proceedings, 5S-2~3.1986) Problems to be solved by the invention Techniques in conventional examples Then, there are the following problems.

(1) In conventional systems where drawings are input using a scanner, line breaks may occur on the input image data due to the quality of the input drawings or the influence of the binarization threshold during scanner input. Easy to do. In the conventional example, when the line break occurs on the shape line and a closed loop is not formed,
The shape line cannot be extracted.

(2) In the conventional example, a method is adopted in which lines forming a closed loop are extracted from the remaining line segments as shape lines. For this reason, even if there are no line breaks on the shape line, for example, whiskers caused by noise generated during scanner input or line thinning processing may appear on the true shape line in a pattern similar to the arrow. In this case, a part of the shape line is extracted as a dimension line, so the shape line may not be extracted.

(3) Due to the influence of the line thinning process, line elements (hereinafter referred to as ambiguous line elements) that also serve as multiple symbol constituent elements appear, particularly at locations where multiple line segments intersect at shallow angles. Since this ambiguous line element is removed when the first symbol is separated and extracted, the second and subsequent symbols are divided in the middle =4-, resulting in the inability to extract them. In addition, line elements with short arrows may not appear due to the thinning process, and may not be extracted using the conventional method of tracing the axis of the arrow from the arrow shape to obtain a dimension line.

(4) In drawings such as mechanical drawings in which a wide variety of line figures are drawn at arbitrary angles and where these line segments intersect at arbitrary points, on feature points that should originally be open end points, Other line segments may be drawn so as to touch or intersect, and the feature point may not appear as an open end point.

For this reason, in the conventional example in which both ends of the dimension extension line are open end points, extraction cannot be performed.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention registers in advance a line element that connects two open end points close to each other within a certain distance as shape line break candidates, and a shape line break candidate label adding processing unit that gives a candidate label; a non-shape line label adding processing unit that gives a non-shape line label to a line element that clearly does not indicate a shape; If the candidate label and the non-shape line label overlap, a shape line break candidate deletion process that changes the shape line break candidate label to the non-shape line label and deletes the registered shape line break candidate. a non-shape line label propagation processing unit that propagates the non-shape line label to unlabeled line elements; and a non-shape line label propagation processing unit that propagates the shape line break candidate label to unlabeled line elements. A shape line break candidate label propagation processing unit to propagate, and a shape to give shape line loop candidate labels to all line elements to which the non-shape line labels and shape line break candidate labels have not been attached or propagated. A line loop candidate labeling processing unit, a shape line loop extraction processing unit that extracts shape line loops while ensuring consistency in the drawing based on features on shape lines and non-shape lines, and a shape line loop extraction processing unit that extracts shape line loops while ensuring consistency in the drawing, a shape line break connection processing unit that detects and connects the line break point when
a symbol component line element extraction unit that starts tracing from a line element that is clearly not a shape line and extracts a plurality of line elements that constitute various symbols other than shape lines; and a symbol that recognizes the series of extracted line elements. It is equipped with a configuration called a recognition section.

According to the above configuration, the present invention first detects two open end points that are close to each other within a certain distance, registers the line elements connected to them as shape line break candidates, and assigns a shape line break candidate label. do.

Next, line elements that are clearly not shape lines are extracted and given non-shape line labels. At this time, a line element for which a shape line break candidate label and a non-shape line label overlap is deleted from the shape line break candidates, and the shape line break candidate label is changed to a non-shape line label. Next, a process is performed to propagate the non-shape line label to unlabeled line elements, and then a process is performed to propagate the shape line break candidate label to unlabeled line elements. Shape line loop candidate labels are assigned to all line elements to which no labels have been assigned even through the label propagation process. Furthermore, a shape line is extracted based on features on the shape line and a line that is not a shape line. Note that if a line break occurs on the shape line, the line break point is detected and connection processing is performed. Finally, tracing is started from a line element that is clearly not a shape line, a process is performed to extract multiple line elements that constitute various symbols other than shape lines, and a symbol composed of the series of extracted line elements is extracted. recognize.

As described above, even when a line break occurs on the shape line, a shape line loop can be extracted, and various symbols representing the dimensions of the shape can be recognized.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a block diagram of an embodiment of the drawing recognition device of the present invention. In this embodiment, the drawing to be recognized is a mechanical drawing (two-dimensional processing drawing).

In FIG. 1, drawing data 12 is, for example, image data obtained by inputting the machine drawing using a scanner.
After performing the line thinning process, extract open end points and branch points that are feature points on the line figure, and approximately encode the line figure connecting the feature points with line elements consisting of straight lines, circles, and arcs, The feature points and line elements are expressed in a graph structure. Note that hereinafter, the feature points will be referred to as nodes, and the line elements will be referred to as elements.

The drawing recognition device 1 of this embodiment extracts shape lines in a drawing based on the data of the elements and nodes extracted as described above.

The extraction result can be confirmed on the monitor 13, for example.

In the drawing recognition apparatus of one embodiment configured as described above, the operation thereof will be explained for each processing section below.

(1) Shape line line break candidate labeling processing unit 2 Generally, shape lines are drawn as thick, thick lines, so line breaks occur less frequently on drawing data than dimension lines and dimension extension lines that are drawn as thin, thin lines. Extremely low. Moreover, most line breaks on the shape line occur when the line is drawn across the erased trace of the line segment on the drawing, and are approximately the width of the line of a writing instrument. Therefore, it is considered that the line breaks that occur on the shape line are equal to or less than the constant interval Lc. FIG. 2 shows an example of a line break pattern of a shape line handled in this embodiment. Second
The distances LL, L2, and L3 between the two open end points shown in FIGS. (a), (b), and (c) are all equal to or less than the above-mentioned constant distance Lc. In addition, even in cases where line breaks occur continuously, as shown in Figure (d),
It is sufficient that the distances L4 and L5 between the two open end points are equal to or less than the above-mentioned constant distance Lc.

This processing unit extracts combinations of elements connected to open end nodes that satisfy the above conditions as shape line break candidates, and stores them in the shape line break candidate list 1.
A shape line break candidate label is assigned to the corresponding element.

As shown in FIG. 3, if there are multiple open end nodes satisfying the above conditions for the open end node N1 of interest, all element combinations (L
l, L2), (LL, L3), and (L2.L3) are extracted as shape line break candidates.

(2) Non-shape line labeling processing unit 3 In the drawing recognition device of this embodiment, by labeling an element that is clearly not a shape line and propagating the label, the label is not propagated until the end. The remaining Niremen I. is considered a shape line loop candidate. This processing section first extracts non-shaped lines (dimension lines, dimension extension lines, -dot-dashed lines, leader lines, etc.) in the mechanical drawing, and performs a process of assigning non-shaped line labels.

Generally, many non-shaped lines in mechanical drawings have open end points. In this processing unit, among the elements mentioned above that are clearly not shape lines, the following is applied to end line elements (elements connected to open end point nodes that are not assigned shape line break candidate labels). Perform the process of adding a non-shape line label according to the procedure.

[Focus] All open end nodes [Conditions] No shape line break candidate label is assigned to the element connected to the open end node of interest.

[process] Add a non-shape line label to the corresponding element.

(3) Shape Line Break Candidate Deletion Processing Unit 4 During the non-shape line labeling processing described in the non-shape line labeling processing unit 3, a situation as shown in FIG. 4 may occur. For example, in FIG. 4(a), although the element combination (LL, L2) has already been registered as a shape line break candidate by the process of the shape line break candidate labeling processing unit 2, By focusing on one open end point N3, we can see that the condition for a non-shape line label is also not satisfied. In such a situation, this processing section gives priority to the non-shape line label and replaces the shape line break candidate label assigned to L2 with the non-shape line label. Along with this, the label is similarly changed for the second element L1 on the other side, and the information on the combination of elements (L1, L2) in the shape line break candidate list is deleted.

However, as shown in FIG. 4(b), if L2 constitutes a combination of multiple elements and line break candidates, the shape line break candidate labels of the other elements L1 and L3 are changed. Instead, only the registration of the combination including the corresponding element L2 in the shape line break candidate list is deleted.

(4) Non-shape line label propagation processing unit 5 This processing unit narrows down shape line loop candidates by performing the propagation process of the non-shape line labels labeled by the non-shape line labeling processing unit 3 in the following manner. I do.

[Focus] All nodes other than open end points (hereinafter referred to as internal nodes) [Conditions] (a) One or more non-shaped line labels or non-shaped line propagation labeling elements given by the following [processing] are connected Doing things.

(b) Only one labeling element other than non-shaped lines and non-shaped line propagation labels is connected.

(c) The element corresponding to (b) above must be connected to the internal note of interest at the end point.

[Processing] Add a non-shape line propagation label to the element that meets the above [condition].

FIG. 5 shows a part of the pattern in which the non-shape line label is propagated through the above process. Figure 5(a).

In (b) and (c), elements El, E2, and E3 connected to the internal node N1 of interest are given non-shape line labels or non-shape line propagation labels, and elements connected to the internal node N1 of interest at their end points. It is assumed that none of the above labels is attached to L1. In this way, an element that connects only one end point to a node that is connected only by non-shape lines cannot be a shape line, so
A non-shape line propagation label will be propagated to the element L1.

However, as shown in FIG. 6, if the element L2 that corresponds to the above-mentioned condition 1 already has a shape line breakage candidate label by the shape line breakage candidate label assignment processing unit 2, the shape line breakage candidate label As described in the deletion processing unit 4, the shape line break candidate label is changed to a non-shape line label and deleted from the shape line break candidate list.

In order to simplify the algorithm, this processing does not perform element tracking processing, but performs the above-mentioned processing on each internal node. Therefore, depending on the order of focus on each internal node, it is possible that the label propagation may not be completed completely. Therefore, in this process, each time the above process is performed for all internal nodes, it is checked whether label propagation has actually been performed, and if propagation has been performed at even one location, the process is repeated again for all internal nodes. The above processing is performed on . This cycle is repeated until no label propagation occurs at all.

(5) Shape line break candidate label propagation processing unit 6 This processing unit performs the propagation process of the shape line break candidate label assigned by the shape line break candidate label assignment processing unit 2 in the following manner.

[Focus] All internal nodes [Conditions] (a) Shape line break candidate labels or the following [Processing]
One or more elements to which the shape line break candidate propagation label given by is connected.

(b) Only one element to which a non-shape line, non-shape line propagation, shape line break candidate, or shape line break candidate propagation label is attached is connected.

(c) The element corresponding to (b) above is connected to the node of interest at the end point.

[Processing] A shape line break candidate propagation label is assigned to the element that meets the above [condition].

Note that in this process as well, similarly to the non-shape line label propagation processing section 5, the above process is repeated until no label propagation is performed at all.

(6) Shape line loop candidate extraction processing unit 7 As described above, first, after assigning and propagating non-shape line labels to all elements that are definitely not contour lines, Shape line break candidate labels were assigned and propagated to all elements with the possibility of . Therefore, by the above process starting from all the open end points in the drawing, some sort of label has been given to all the elements that do not form a loop. In this processing section, first, all elements to which no labels have been assigned at this point are regarded as shape line loop candidates, and are assigned shape line loop candidate labels. Therefore, as shown in FIG. 7(a), if there is no line break on the shape line, all the elements constituting the true shape line are (
It will be included in area C). The remainder of the region (C) contains nests, closed loop elements, etc. that are incidental to dimension lines and extension lines. These are gradually identified and removed by the shape line loop extraction processing section 8. On the other hand, as shown in FIG. 7(b), if a line break occurs on the shape line, the elements constituting the true shape line are included in the areas (B) and (C). become. In such a case, as before, an approach is taken in which the attributes are gradually clarified as the process of the shape line loop extraction processing section 8 progresses.

As a result of the labeling and propagation processing described above, element groups that are shape line loop candidates and shape line break candidates were extracted. These elements are a group of elements that do not have any open end points if the line break candidate locations are considered to be logically connected. Therefore, these element groups are divided into paths that form a closed loop with no branch points, and
Paths are broadly divided into paths from one branch point to another.

Note that this path is called a loop candidate element, and the branch point is called a loop candidate node.

Next, processing for extracting loop candidate elements and loop candidate nodes is performed in the following manner.

[Conditions for all elements of interest] (a) Either a shape line loop candidate, a shape line break candidate, or a shape line break candidate propagation label is assigned.

(b) In [Processing] (b) below, the processed flag must not be set.

[Processing] (a) Track and extract elements that have either of the above labels on both sides of the above element of interest.

Tracking is continued until the element returns to the first element of interest or reaches a node (referred to as a loop candidate node) to which a plurality of elements having the above-mentioned labels other than the element being tracked are connected. A series of traced and extracted elements is set as a loop candidate element.

(b) Set a processed flag on all elements constituting the path extracted in [Processing] (b) above.

(7) Shape line loop extraction processing unit 8 This processing unit performs a process of determining whether or not each loop candidate element obtained by the shape line loop candidate extraction processing unit 7 is a true shape line, Shape-19= Determine and extract line loops. To this end, this embodiment focuses on the following features.

○Inflection Point Node A node in which only two elements are connected with an opening angle of a certain value or more at their end points is called an inflection point node. As shown in FIGS. 8(a) and 8(b), bending point nodes often appear on the shape line, and provide a significant feature in identifying the shape line. In the machine drawing, as shown in Figure 8 (C), it also appears on the leader line, but the two elements connected to this are given non-shape lines and non-shape line propagation labels, so they can be easily identified. A distinction can be made between

○Semi-inflection point note In the image data that has been subjected to line thinning processing, Fig. 9 (a
) and (b), whisker-like line elements may occur at the original bending point nodes, and such nodes are called quasi-bending point nodes.

Quasi-inflection point nodes provide substantially similar characteristics to the inflection point nodes.

○Arrow side direction connection node As shown in FIGS. 10(a), (b), (c) and (d), a loop candidate element that intersects with a diagonal arrow having an open end point, or as shown in FIG. 10(e) ), (f
) and (g), loop candidate elements intersecting diagonal arrows connecting via horizontal elements with open endpoints are clearly shape lines. On the other hand, for example, as shown in FIG. 10(h), if an arrowhead exists on an element that is in the loop candidate element group,
Clearly, the loop candidate element that includes this element is not a shape line. In this way, arrows are very important clues for detecting accidental loops caused by dimension lines and extension lines. However, in image data that has been subjected to line thinning processing, part of the arrowhead may be lost, or conversely, due to the occurrence of noise or the above-mentioned whisker-like elements,
It may have a shape similar to an arrow, so care must be taken when handling it.

In this processing section, in order to reliably extract the arrows shown in FIGS. 10(a) to (g), diagonal elements with open end points and diagonal elements connected via horizontal elements with open end points are used. After tracing the element until it reaches the node to which the loop candidate element connects, and confirming that the arrowhead exists near the node,
The above node is extracted as an arrow side connection node.

O Arrow Forward Connection Node When an arrowhead as shown in FIG. 10(h) exists on a loop candidate element, the node to which the arrowhead connects is
It is called an arrow rate direction connection node. As mentioned above, in image data obtained by performing line thinning processing, a loose candidate element having an arrow forward direction node is not necessarily a true shape line, but there are multiple arrow forward direction nodes on a loop candidate element. If a directional connection node exists, there is a strong possibility that it is not a shape line.

O Non-shape line connection node A node in which elements belonging to each loop candidate element are connected in the form shown in FIGS. 11(a) and (b), for example, is called a non-shape line connection node. That is, in FIG. 11(a), elements L1 and L2 belong to loop candidate elements, and element E
1 is an element having a non-shape line label, and elements L1 and El form a straight line, and in the same figure (
In b), elements Ll and L2 are elements belonging to loop candidate elements, El and E2 are elements having non-shape line labels, and elements Ll, El and L2゜E2 each form a substantially straight line. . It is rare for such a non-shape line connection node to appear on a true shape line, and there is a strong possibility that elements Ll and L2 are not shape lines. However, as mentioned above, the 11th
A whisker-like element E1 as shown in Figure (C) may appear at a node on the shape line. Therefore, in order to distinguish them from such whisker-like elements, the elms E1 and E2 shown in FIGS. 11 (a> and (b)) are assumed to have sufficient length.

○Loop candidate element connection direction As shown in FIG. 12(a), in a loop candidate node N1 to which a plurality of loop candidate elements Ll, L2, and L3 are connected, for example, two loop candidate elements L
When 1 and L2 form a straight line, as mentioned above,
There is a strong possibility that loop candidate L3 is not a shape line. However, as shown in FIG. 12(b), two sets of loop candidate elements Lay, L2 and L3. When both L4 form a substantially straight line, it cannot be determined which straight line component is the shape line.

This processing section focuses on the above characteristics and extracts shape line loops in the following manner. First, for each loop candidate element, the degree to which it is a shape line and the degree to which it is not a shape line is measured. Next, we comprehensively evaluate the measurement results of the above characteristics,
For each loop candidate element, a shape line loop label is given if it is definitely a shape line, and a non-shape line loop label is given if it is definitely not a shape line. Note that if it is ambiguous whether the line is a shape line or a non-shape line, an unknown label is assigned without forcing the distinction. Thereafter, focusing on each loop candidate node, a process of propagating a shape line loop label or a non-shape line loop label is performed for the loop candidate element to which an unknown label has been assigned, while ensuring consistency throughout the drawing.

A method for propagating the above labels will be described below.

First, as shown in FIG. 13(a), a loop candidate node N1 includes two loop candidate elements L1 and L2 having shape line loop labels, and L3 having an unknown label.
When connected, it is impossible for the shape lines to intersect in a two-dimensional processing drawing, so there are no loop candidates)
・L3 is clearly not a shape line. Therefore, while changing the unknown label of L3 to a non-shape line loop label,
3 is deleted from the loop candidate element, N1 is deleted from the loop candidate node, and the loop candidate elements L1 and L2 are merged. In addition, in this case, the loop candidate node N1 is
Even if other loop candidate elements having unknown labels other than L3 are connected, the handling is the same. Also, the first
As shown in FIG. 3(b), when a loop candidate element L3 having an unknown label and loop candidate elements L1 and L2 having non-shape line loop labels are connected to a loop candidate node N1, a shape line is connected in the middle. Since it is impossible for the line to break at , the loop candidate element L3 is clearly not a shape line. In this case as well, the unknown label of L3 is changed to a non-shape line loop label, and Ll, L
2 and L3 are deleted from the loop candidate element, and N1 is deleted from the loop candidate node. In addition, in this case, the loop candidate node N1 has, in addition to Ll and L2,
Other loop candidate elements having non-shape line loop labels may be connected. Furthermore, Fig. 13(c)
As shown in , when Ll with a shape line loop label, L3 with an unknown label, and L2 with a non-shape line loop label are connected, the shape line is not disconnected in the middle, so L3 is unknown. The label is changed to a shape line loop label, L2 is deleted from the loop candidate element, N1 is deleted from the loop candidate node, and the loop candidate elements L1 and L3 are integrated. In this case,
Loop candidate elements having a plurality of non-shaped line loop labels including L2 may be connected to the loop candidate node N1.

On the other hand, as shown in FIG. 13(d), when loop candidate element L4 having a shape line loop label is connected to loop candidate elements L3 and L5, all of which have unknown labels, the situation at this point is No processing is performed because it is not clear. Similarly, in FIG. 13(e), loop candidate element L4 having a non-shape line loop label is connected to loop candidate elements L3 and L4, all of which have unknown labels, and label propagation is prevented. Not performed. However, the processing in the unclear connection states as shown in FIGS. 13(d) and (e) is postponed to the first stage.
By performing the propagation process in the obvious connection states as shown in FIGS. 3(a), (b), and (c) first, the following situation occurs.

In FIG. 14(a), the connection state centered on the loop candidate node N2 is exactly the same as in FIG. 13(d), and the label is not propagated independently, but the loop candidate node N1
Since the connection state centered on L3 is exactly the same as in FIG. 13(a), as mentioned earlier, the loop candidate element L3
unknown label is changed to non-shape line loop label. As a result, the loop candidate node N2 shown in FIG. 14(a)
Since the connection state centered on is the same as that shown in FIG. 13(c), the unknown label of the loop candidate element L5 can be changed to the shape line loop label. In addition, in FIG. 14(b), loop candidate node N
The connection state centered on node 2 is exactly the same as in FIG. 13(e), and the connection state centered on loop candidate node N1 is exactly the same as in FIG. 13(a), so loop candidate element L3 is unknown. The label is changed to a non-shape line loop label. As a result, the connection state centered on the loop candidate node N2 shown in FIG. 14(b) becomes the same as that shown in FIG. can be changed to a non-shape line loop label. In this way, even if the connection state of a single loop candidate node cannot be determined, reliable information can be propagated throughout the drawing by matching the connection relationships. In addition, FIG. 14(c), (d), (e) and (f) are
Fig. 13 is a combination of (b) and (d), (b) and (e), (c) and (d), (C) and (e),
Similarly, label propagation processing can be performed.

By propagating the above process to all loop candidate elements with unknown labels in the drawing and repeating it until all loop candidate nodes are deleted, multiple Only loop candidate elements remain. In addition, by the above processing,
Any loops caused by dimension lines or extension lines are removed.

Next, it is determined whether each loop candidate element having the above-mentioned shape line loop label is a true shape line. At this point, only the elements constituting the nest are mixed in the loop candidate elements having the shape line loop label, and it is necessary to determine and remove the nest. Nests are similar in shape to small holes, but small holes are easily distinguished because they have horizontal and vertical center lines and dimension lines marked to indicate their location and radius (or diameter). , and remove them from the loop candidate elements.

Through the above processing, all loop candidate elements constituting the true shape line can be extracted.

Note that if there are no elements having a shape line break candidate or a shape line break candidate propagation label among all the elements constituting these loop candidate elements, these are extracted as shape line loops.

Note that the labels of all elements constituting the extracted shape line loop are unified as shape line labels, and the labels of all other elements are unified as non-shape line labels.

(8) Shape line break connection processing section 9 This processing section has shape line break candidates and shape line break candidate propagation labels in the loop candidate elements extracted by the shape line loop extraction processing section 8. Processing is performed only if the element exists. In this embodiment, as described above, the locations registered as shape line break candidates have been treated as being logically connected. After performing connection processing at the line break locations, the loop candidate elements are extracted as shape line loops. The results of connection processing performed on the line breaks on the shape lines shown in FIGS. 2(a), (b), (c), and (d) are
Shown in Figures (a>, (b), (c) and (d)).

As described above, even when a line break occurs on a shape line, a shape line forming a loop can be extracted. In this case as well, the labels of all elements constituting the extracted shape line loop, including the element with the line break connection described above, are changed to shape line labels, and the labels of all other elements are changed to non-shape line labels. Unify.

3l- (9) Symbol component line element extraction unit As above 10,
In drawing data that includes a mixture of line figures that represent shapes and line figures that constitute various symbols that represent the dimensions of the shape,
We were able to extract the shape line element that has the most significant feature of forming a loop. Therefore, all line elements except shape line elements consisting of straight lines, arbitrary combinations of circular arcs, and circles constitute various symbols for expressing the dimensions of shapes, and include dimension lines, extension lines, and drawers. The process of extracting line elements constituting symbols such as lines and dashed-dotted lines can now be performed linearly and with considerable force.

This processing unit performs a process of extracting line elements constituting various symbols, and at that time, performs processing in order from the longest element among the elements having the above-mentioned non-shaped line labels. This is because the longer the element, the more stable the inclination angle of the element indicating the tracking direction is due to the influence of distortion caused by the 114II line conversion process at the intersection of line segments.

The outline of the tracing and extraction processing of symbol constituent line elements is shown below.

[Focus] all elements (However, in descending order of element length) [conditions] (a) Must have a non-shaped line label.

(b) The flag must not be set by [Processing] (c) below.

[Processing] (a) Connected elements are linearly traced in both directions of the element of interest until reaching one of the nodes shown in [Tracing End Conditions] below.

(b) Give the same classification number to each of the above-mentioned series of tracked elements.

(c) Set a flag for the series of tracked elements.

[Tracing End Conditions] Elements with non-shape line labels are traced until one of the nodes below is reached.

(B) Open end node (B) Node to which traceable elements are not connected (C)
Node to which multiple traceable elements are connected (D) Node to which elements with shape line labels are connected. However, as shown in FIG. 16(a), two elements L
The supplementary angle of 1 and L2 is less than or equal to f (LL, L2), and the leg length VL of the perpendicular line from node N2 to the line segment connecting two nodes N1 and N3 is less than or equal to g (Ll, L2) In this case, it is assumed that L2 can be traced to Ll. Note that f (Ll, L2> is the threshold value of the angle calculated from the lengths of elements L1 and L2, and g (Ll, L2) is the threshold value of the perpendicular line calculated from the lengths of elements L1 and L2. This is the threshold of leg length.

Note that this processing unit takes into account the occurrence of ambiguous elements due to line thinning processing, and as shown in FIG. In this case, tracking is continued only if the length of element L2 is equal to or less than a certain length and a traceable element L3 is connected to the opposite node N2. Furthermore, as shown in FIG. 16(c), if element L2, which has already been assigned a classification number in [processing] 2), reaches the connected node N1 during tracking, as before, element L2 Tracking is continued only if the length of is less than a certain length and the traceable element L3 is connected to the opposite node N2.

In this case, multiple classification numbers will be given to element L2.

(10) Symbol Recognition Unit 11 This processing unit finally recognizes a symbol constituted by a series of line elements having the same classification number, based on the classification number given in the symbol constituent line element extraction unit 10.

In mechanical drawings, except for irregular shape lines,
Various symbols have a very strong correlation with the inclination angle of their constituent elements. This processing unit recognizes symbols by paying attention to this.

First, in the shape line loop extraction processing unit 8, when extracting arrow side direction connection nodes and arrow forward direction connection nodes, a series of elements forming the symbols shown in FIGS. 10(a) to (g) are extracted. ing. In this processing section, as shown in (a) to (d) in the same figure, an element in a diagonal direction that connects to an open end point, and an arrowhead shape that connects in the vicinity of a node where that element intersects an element having a shape line label. Extract elements as dimension lines. In addition, as shown in (e) to (g) of the same figure, diagonal line elements connected via horizontal line elements connected to open end points, and nodes where these elements intersect elements with shape line labels. Arrowhead-shaped elements connected in the vicinity are similarly extracted as dimension lines. Note that the above recognition process does not necessarily require an element forming an arrowhead shape, since it is conceivable that the arrowhead shape may not appear due to the influence of the thinning process. However, as shown in FIG. 17, for diagonal elements connected via horizontal elements with open end points, arrowhead-shaped elements are usually not drawn, but since they do not intersect elements with shape line labels, as shown in FIG. It can be easily distinguished from the states shown in (e) to (g). Note that the elements shown in FIG. 17 are recognized as leader lines. In addition, as shown in FIGS. 18(a) and (b), if diagonal elements with the same classification number intersect with an element having a shape line label at one end point, the intersection If arrowhead-shaped elements are connected near a node, it is similarly recognized as a dimension line. Note that even in this case, the arrowhead-shaped element does not necessarily have to exist.

Next, horizontal and vertical symbols having the same classification number are recognized. As shown in FIGS. 19(a) to (d), among the non-shaped line elements having the same classification number, as described in the shaped line loop extraction processing unit 8, the arrowhead-shaped elements are connected in the forward direction. the dimension line,
Recognize orthogonal elements as dimension extension lines.

Finally, as shown in FIGS. 20(a) and 20(b), when long and short elements repeatedly appear on a straight line, they are recognized as a dashed line.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) List candidates for line break points on the shape line in advance,
By performing labeling and propagation processing to distinguish line segments that have features that are clearly not shape lines, even if a line break occurs on a shape line, the broken line can be detected and connected, and the shape Lines can be extracted.

(2) In objects such as mechanical drawings, where a wide variety of line segments are drawn at arbitrary angles and these line segments intersect at arbitrary locations, closed loops occur everywhere.
A method that simply tracks elements would require complicated stack processing, and efficient processing cannot be expected. By performing labeling and propagation processing as in the present invention, processing can be performed at high speed with a small storage capacity, thereby improving processing efficiency.

(3) Since the drawing recognition device of the present invention can recognize ambiguous elements that occur due to the influence of the thinning process, it is possible to completely separate and recognize a plurality of symbols via ambiguous elements.

(4) Even if some or all of the arrowhead-shaped line segments do not appear due to the thinning process, the dimension lines and dimension extension lines can be reliably recognized.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a drawing recognition device according to an embodiment of the present invention, FIG. 2 is a diagram showing line break patterns on shape lines, and FIG. 3 is a pattern in which shape line break candidates form a plurality of combinations. Figure 4 is an explanatory diagram showing the deletion of shape line break candidates that is sometimes performed during labeling, Figure 5 is an explanatory diagram of the label propagation path, and Figure 6 is a diagram showing the deletion of shape line break candidates that is sometimes performed during label propagation processing. An explanatory diagram of candidate deletion, Fig. 7 is a diagram of the inclusion relationship between various labeling elements and shape lines, Fig. 8 is an explanatory diagram of bending point notes, Fig. 9 is an explanatory diagram of quasi-bending point nodes, and Fig. 10 is an illustration of the inclusion relationship between various labeling elements and shape lines. 11 is an explanatory diagram of a non-shape line connection node, FIG. 12 is an explanatory diagram of a loop candidate element connection direction, and FIG. 13 is an explanatory diagram of a shape line and a non-shape line connection node. An explanatory diagram showing how shape line loop labels are propagated. Figure 14 is an explanatory diagram showing how shape lines and non-shape line loop labels are propagated due to consistency within the drawing. Figure 15 is a line break point on a shape line. Figure 16 is a diagram of the connection state of traceable elements, Figure 17 is an illustration of leader lines, and Figure 18 is a diagonal dimension line with no open end points. Explanatory diagram showing, No. 19
The figure is an explanatory diagram showing dimension lines and dimension extension lines made up of horizontal and vertical elements, and FIG. 20 is an explanatory diagram showing a dashed-dotted line. DESCRIPTION OF SYMBOLS 1...Drawing recognition device, 2...Shape line break candidate labeling processing unit, 3...Non-shape line labeling processing unit, 4
- Shape line break candidate deletion processing section, 5... Non-shape line label propagation processing section, 6... Shape line break candidate label propagation processing section, 7... Shape line loop candidate extraction processing section, 8.・
Shape line loop extraction processing section, 9.. Shape line break connection processing section, 10.. Symbol component extraction section, 11.. Symbol recognition section, 12.. Drawing data, 13.. Monitor. Name of agent Patent attorney Toshio Nakao (1 person) Figure 10 (CL) (b) (C2 (CH2 Figure 11 (α)) (b)
(c) Figure 12 (a,) (I)) Ward C) Issakumi 11 Smoke □-□ ＼ノ区q Peng

Claims (1)

[Claims] After thinning processing is performed on the line figures representing the shape and the line figures constituting various symbols for expressing the dimensions of the shape, open end points and branch points, which are feature points on the line figures, are extracted. At the same time, in drawing data in which the line figure connecting the feature points is encoded as a line element, a line element connecting two open end points close to each other within a certain distance is registered in advance as a shape line break candidate. a shape line break candidate label adding processing section that gives a shape line break candidate label; a non-shape line label adding processing section that gives a non-shape line label to a line element that is not a line clearly indicating a shape; If the shape line break candidate label and the non-shape line label overlap, the shape line break candidate label is changed to the non-shape line label, and the registered shape line break candidate is deleted. a break candidate deletion processing unit; a non-shape line label propagation processing unit that propagates the non-shape line label to unlabeled line elements; A shape line break candidate label propagation processing unit that propagates to elements, and a shape line loop candidate label for all line elements to which the non-shape line labels and shape line break candidate labels have not been assigned or propagated. a shape line loop candidate labeling processing unit that assigns a shape line loop candidate label; a shape line loop extraction processing unit that extracts shape line loops based on features on shape lines and non-shape lines; , a shape line line break connection processing unit that detects and connects line breaks, and a symbol configuration that starts tracing from a line element that is obviously not a shape line and extracts multiple line elements that constitute various symbols other than shape lines. A drawing recognition device comprising a line element extraction unit and a symbol recognition unit that recognizes the series of extracted line elements, and extracts and recognizes various symbols including shape lines.