JPS603676B2 - Intersection extraction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for extracting intersections of characters, etc.

Character recognition is performed based on feature points such as stroke generation points, vanishing points, start points, end points, and intersections.

In the prior art, an image memory storing quantized image information is scanned using a 3×3 mask to perform thinning processing, and intersections are extracted from the thinned image information. However, this type of intersection extraction method has the drawback that the thinning process requires a very large number of processing steps and that intersections cannot be extracted reliably. SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and to provide an intersection extraction method that has features such as being able to significantly reduce processing steps and increasing recognition accuracy.

Therefore, the intersection extraction method of the present invention includes an image input device, a quantization device that quantizes the image information from the image input device, an image memory in which the nasalized image information is stored, and the image memory in a predetermined manner. In the intersection extraction method, the intersection extraction method includes a scanning device that scans in a direction, and extracts intersections of characters using scanning information output from the scanning device, a first scanning memory in which scanning information output from the scanning is stored; a second scanning memory in which the next scanning information of the scanning information in the first scanning memory is stored; a predetermined color element having a predetermined width or less has a predetermined length or more based on the contents of the first scanning memory and the second scanning memory; Stroke detection means for detecting whether the strokes are continuous or irregular; end point/start point identification means for identifying a stroke start point candidate point and a stroke end point candidate point based on the contents of the first scanning memory and the contents of the second scanning memory; and the above-mentioned stroke detection means. means for registering a stroke end point candidate point or stroke female point candidate point as a stroke end point or stroke start point when a stroke is detected, and whether or not the stroke start point exists within an intersection check zone set with the stroke end point as a reference. The invention is characterized by having means for checking whether the The present invention will be explained below with reference to the drawings. Figure 1 is a diagram explaining the generation point, vanishing point, end point, and start point of a stroke. Figure 2 is a diagram explaining intersection extraction using the end point and start point. Figure 3 is a diagram explaining intersection point extraction using the end and start points. 4 is a block diagram of one embodiment of the present invention, FIG. 5 is a diagram explaining the identification of the generation point, vanishing point, start point, end point, and end point. FIG. 6 is an intersection check for intersection detection.・A diagram showing the zones, FIG. 7 is a diagram showing the intersection detection logic when using the intersection check zone of FIG. 6, FIG. 8 is a diagram showing an example of the intersection check zone, and FIG. FIG. 9 is a diagram showing the intersection detection logic when using the intersection check zone of FIG. 8; The figure in FIG. 1 is binarized, and the shaded area indicates a logical "1" area. When writing characters with a writing instrument, the line width of the stroke is generally below a certain value, and the stroke length is above a certain value. In FIG. 1, S indicates the black width setting value, and R indicates the black length setting value. Scan the first row (horizontal row at the top) with a horizontal scanning line, then the second row, and then the third row, the fourth row, etc. from the top. When scanning downward, if a black line thinner than the width setting value S continuously extends downward and is longer than the length setting value R, the point Gv is established as the stroke generation point. Point Ev is established as the end point of the stroke when the stroke moves downward to position P, where the width is larger than the width setting value S. The line connecting points Gv and Ev protrudes upward. It represents the stroke where the width is large.When the width reaches the width position P2,
v is established as the starting point. The point Tv is established as a vanishing point where black, which is narrower than the width setting value S, disappears and changes to white.
However, if the distance between point Fv and point Tv in the vertical direction is less than or equal to the length setting value R, point Fv and point Tv are canceled. The line connecting point Fv and point Tv represents a downwardly protruding stroke. Points Gv, Ev, Fv, and Tv are the middle points of black, respectively. scan the first column (leftmost column) with a vertical scan line, then scan the second column;
If the figure is scanned from left to right in the following order, 3rd column, 4th column, etc., the starting point Th and vanishing point Th
is obtained. FIG. 2 is a diagram illustrating intersection extraction using an end point and a starting point.

The figure shown is the first row (horizontal row at the top) of horizontal scanning lines.
, then the second row, and then the third row,
When the figure is scanned from top to bottom as in the fourth line, etc., when the scanning line reaches a branch point, the line width becomes larger than the width setting value S, and the end point Ev is detected. As the scanning line moves further downward, the width becomes smaller than the width setting value S, and the starting point Fv or Fv2 is detected. Finally, the width setting value S
Vanishing points Tv, , Tv2 where the narrower black disappears are detected. If Onnadai point Fv or Fv2 exists within the intersection check zone A set with the end point Ev as a reference, points XE and YE+2 are determined as intersections. However, x8 indicates the X-direction component of the end point Ev, and YE indicates the Y-direction component of the end point Ev. FIG. 3 explains intersection extraction using end and start points.

If the line width of the handwriting is much smaller than the width setting value, the intersection cannot be extracted using the method shown in FIG. To deal with such a case, there is a black part smaller than the width setting value S on the n-th scanning line, and a plurality of black parts that touch this black part exist on the n+1-th scanning line. If so, it is determined that there is a branch, and point J3 is set as the intersection. Note that J, , J2, and J3 each indicate the midpoint of the above black portion. These points J, , J2, and J3 are named end and start points. Note that J, , J2 are the starting points of the stroke. FIG. 4 is a block diagram of one embodiment of the present invention, in which 1 is a form, 2 is an image input device, 3 is a quantization circuit, 4 is an image memory, 5h is a horizontal scanning device, 5v is a vertical scanning device, 6h is a feature point extraction device that extracts feature points based on output information from the horizontal scanning device 5h, 6v is a feature point extraction device that extracts feature points based on output information from the vertical scanning line 5v, and 7-1 is a feature point extraction device that extracts feature points based on output information from the horizontal scanning device 5h. 1 scanning memory, 7-2 is the second
a scanning memory; 8 a continuous condition determination circuit; 9 a width measurement circuit;
10 is an AND gate, 11 is a line length counter, 12 is a line length condition setting circuit, 113 is a comparison circuit, 14 is an end point/start point identification circuit, 15 is a generation point/vanishing point identification circuit, 16 is an end/start point identification circuit, 17h 17 is a data memory for the feature point extraction circuit 6h, 17v is a data memory for the feature point extraction device, 18 is a start point/end point coordinate arithmetic circuit, 19 is a check zone setting circuit, and 20 is a comparison circuit.

The image input device 2 converts the optical signal from the form into an electrical signal, and outputs this electrical signal to the quantization circuit. Quantization circuit 3
binarizes the analog signal output from the image input device 2 into black and white information, and sends the binarized image information to the memory 4. The image memory 4 can be considered to store binary image information of one character. The horizontal scanning device 5h scans the image memory 4 from top to bottom with horizontal scanning lines going from left to right, and the vertical scanning device 5v scans the image memory 4 from top to bottom with vertical scanning lines going from top to bottom. It scans from the beginning to the right. Since the feature point extraction circuit 6h and the feature point extraction circuit 6v have the same configuration, only the feature point extraction circuit 6h will be described. Scanning information is stored in the first scanning memory 7-1 and the second scanning memory 7-2 in the following manner. In the first scanning cycle, the scanning information of the first row is stored in the first scanning memory 7.
-1, and the scanning information of the second row is stored in the second scanning memory 7-2. In the second scan cycle, the second
The scanning information on the row is stored in the first scanning memory 7-2, and the scanning information on the third row is stored in the second scanning memory 7-2. Similarly, in the nth scanning cycle, the scanning information of the nth row is stored in the first scanning memory 7-1, and the scanning information of the n11th row is stored in the second scanning memory 7-2. The continuity condition determination circuit 8 determines whether or not there is a continuous black area in the first scanning memory 7-1 and the second scanning memory 7-2. FIG. 5 shows an example of the states of the first scanning memory 7-1 and the second scanning memory 7-2, and the shaded areas indicate black areas. When the first scanning memory 7-1 and the second scanning memory 7-2 are in the state shown in FIGS. 5' to 5', the continuity condition determining circuit 8 determines that there is continuity. The width measurement circuit 9 measures whether the width of the black area in the second scanning memory 7-2 is within a width setting value S. The relationship between the width setting value S and the actual width W of the black area may be configured to have a hysteresis characteristic. That is, the actual width W of the black area
When the width of the black area expands to W, the width setting value S becomes S, and when the actual width W of the black area is reduced to W2, the width setting value S becomes S2
It is said that Of course, S, > S2, and W, > W2
It is. The AND gate 10 outputs a logic "1" signal when the continuity condition determination circuit 8 determines that there is continuity and the width measurement circuit 9 determines that there is a black area whose width is equal to or less than the width setting value S. The count value of the line length counter 11 is incremented by 1 every time the AND gate 10 outputs a logic "1". When the end point or vanishing point is detected, the line length counter 11
is cleared to zero. The line length condition setting circuit 12 sets a length setting value R (see FIG. 1). It is also possible to change this length setting value R according to the size of the width setting value S. The comparison circuit compares the count value of the line length counter 11 and the length setting value R of the line length condition setting circuit 12, and outputs logic "1" when the former is greater than or equal to the latter. The logic "1" signal of the comparison circuit 13 can be considered to be a write permission signal for the data memory 17h. The continuity condition determination circuit 8, the width measurement circuit 9, the AND gate 10, the line length counter 11, the line length condition setting circuit 12, and the comparison circuit 13 are configured to detect whether a predetermined number or more of black elements having a line width equal to or less than a predetermined value are consecutively connected. These devices can be considered to constitute a stroke detection device. Although not shown, a plurality of stroke detection devices are actually prepared. The end point/start point identification circuit 14 determines that a black area with a line width larger than the width setting value exists in the first scanning memory 7-1 and a black area with a line width less than the width setting value S that is in contact with this black area is scanned in the second scan. If it exists in the memory 7-2, it is determined that there is a starting point, and the coordinate value of the midpoint of the black area in the second scanning memory 7-2 is recorded.

FIGS. 5C and 5C show an example of a state in which it is determined that there is a starting point. In addition, the end point/start point identification circuit 14 determines whether a black area whose width is less than or equal to the width setting value S exists in the first scanning memory 7-1 and a black area whose line width is larger than the width setting value S that is in contact with this black area is scanned in the second scanning. If it exists in the memory 7-2, it is determined that there is an end point, and the coordinate values of the midpoint of the black area in the first scanning memory 7-1 are recorded. FIG. 5 2 shows an example of a state in which it is determined that there is an end point. The generation point/vanishing point identification circuit 15 detects that a black area whose width is less than the width setting value exists in the second scanning memory 7-2 as shown in FIG. If it does not exist, it is determined that there is a point of occurrence, and the coordinate value of the midpoint of the black area in the second scanning memory 7-2 is recorded.

Further, the generation point/vanishing point identification circuit 15 detects the presence of a black area with a line width less than the width setting value S in the first scanning memory 7-1 as shown in the opening of FIG. area is second
If it does not exist in the scanning memory 7-2, it is determined that there is a vanishing point, and the coordinate values of the midpoint of the black area in the first scanning memory 7-1 are recorded. The end/start point identification circuit 16 identifies branching and joining of characters when the line width of the characters is narrow.

The ending/starting point identification circuit 16 is configured, for example, as shown in FIG.
A black area with a line width less than or equal to the width setting value S exists in the scanning memory 7-1, and a plurality of black areas having line widths less than or equal to the width setting value S that are continuous with this black area are stored in the second scanning memory 7-1. 2, it is determined that there is a branch, and the first scanning memory 7
-1, record the coordinates of the midpoint of the black area as the coordinates of the intersection. Furthermore, when the condition is opposite to that shown in FIG. 5, the ending/starting point identification circuit 16 identifies that there is a connection, and records the coordinates of the central ending/starting point as the coordinates of the intersection. This end/start point identification circuit 16
is unnecessary if it is guaranteed that the green width is always constant. When a plurality of originating points or starting points are identified by the ending point/onnadai point identification circuit 14, the originating point/vanishing point identification circuit 15, or the end/starting point identification circuit 16, one stroke for each originating point or starting point. Detection devices are assigned, and these stroke detection devices check whether each occurrence point or starting point is a stroke origination point or a stroke starting point. What is a stroke detection device?
As mentioned earlier, the continuity condition determination circuit 8, the width measurement circuit 9,
It is composed of an AND gate 10, a line length count 11, a line length condition setting circuit, and a comparison circuit 13, and there are a plurality of them, although not shown. Start point/end point coordinate calculation circuit 18
calculates the difference between the end point of the stroke and the start point of the stroke by dividing it into an x component and a Y component.

The check zone setting circuit 19 determines the size of the intersection check zone and the position of the intersection check zone relative to the end point of the stroke. Comparison circuit 2: Based on the calculation result from the onnadai point/end point coordinate calculation circuit 18 and the intersection check zone information from the check zone setting circuit 19, determine whether the start point exists in the intersection check zone. Check whether there is an intersection and if there is an intersection,
Output the coordinates. Figure 6 shows intersection check zone A.
An example of this is shown below.

The intersection check zone A in Figure 6A is used when scanning the characters in the image memory 4 from left to right with vertical scanning lines, and the intersection check zone A in Figure 6 This is used when scanning characters in the image memory 4 from top to bottom using horizontal scanning lines. In addition, the 6th
In the figure, the minimum rectangular frame has a one-to-one correspondence with the mesh points. Stroke end point Eh (×6,
Intersection check zone A set based on Y8)
If the stroke start point Fh (×s, Ys) exists within
There is said to be an intersection. Similarly, the stroke end point Ev(X
If the stroke start point Fv (Xs, Ys) exists within the intersection check zone A set with E, Y8) as a reference, it is determined that an intersection exists. Figure 7 shows the start point/end point coordinate calculation circuit 1 when using the intersection check zone shown in Figure 6.
8 and the logic executed by the comparison circuit 20.

FIG. 8 shows another example of the intersection check zone A, and FIG. 9 shows the logic that is executed when the intersection check zone A shown in FIG. 8 is used. Next, the operation of the embodiment shown in FIG. 4 will be described by taking as an example the case where the figure shown in FIG. 1 is scanned from top to bottom using vertical scanning lines.

When scanning is performed from top to bottom, the generation point Gv is first identified by the generation point/vanishing point identification circuit 15, and its coordinates are recorded. Line length counter 1 every time one line is scanned
When the count value of 1 is incremented to 11 and the count value of the line length counter 11 becomes equal to or greater than the length setting value, the comparator circuit 13 outputs a write permission signal and confirms the coordinate value of the generation point Gv and that it is the generation point. The indicated feature point type is written into the data memory 17h.

When the scanning line reaches position P, the end point Ev is identified by the end point/start point identification circuit 14, and its coordinates are recorded. At this point, the comparison circuit 13 is outputting a write permission signal, so the coordinate values of the end point in the end point/start point identification circuit 14 and the feature point type indicating the end point are stored in the data/memory 17.
written to h. When the end point is detected, line length counter 1
1 is cleared to zero. When the scanning line comes to position P2,
The starting point Fv is identified by the ending point/starting point identification circuit 14 and its coordinates are recorded. Since the line width becomes less than the width setting value S again, the line length counter 11 starts counting again, and when the count value becomes larger than the length setting value R, the coordinates of the starting point Fv and the feature point type indicating that it is the starting point are displayed. is written to data memory 17h. When the vanishing point Tv is identified by the generation point/vanishing point identification circuit 15, its coordinate values and feature point type indicating that it is a vanishing point are stored in the data memory 17h.
written to. After the scanning of one character is completed, the stroke end point Ev in the data memory 17h is determined and the starting point
The stroke start point Fv is then read out and sent to the start point/end point coordinate calculation circuit 18.

The logic shown in FIG. 7 or 9 is executed by the start point/end point coordinate arithmetic circuit 18, the check/zone setting circuit 19, and the comparison circuit 20 to check whether an intersection exists or not. Next, the operation in FIG. 4 will be explained using an example in which the figure in FIG. 2 is scanned from top to bottom using vertical scanning lines.

When scanning starts, the generation point Gv is first identified by the generation point/vanishing point detection circuit 15, and when it is detected that the generation point Gv is the stroke generation point, the coordinates of the generation point Gv and its type are stored as data. It is written to the memory 17h. As the scanning progresses and the end/start points J, , J2, J3 are identified by the end/start point identification circuit 16, the coordinates of the end/start points J,, J2, J3 are recorded. When it becomes certain that the points J, , J2 are the starting points of the stroke, the point J3 is written into the data memory 17h as an intersection, and the points J, , J2 are written into the data memory 17h as the starting points of the stroke. Point J,, J2
After it is confirmed that is the starting point of the stroke, the vanishing points Tv, , Tv2 are identified by the generation point/vanishing point identification circuit 15, and the vanishing points Tv, , Tv2 are immediately stored in the data memory 17h. written. In this case, when the coordinates of point J3 written as an intersection in data memory 17h are read out, they pass through start point/end point coordinate arithmetic circuit 18 and comparison circuit 20 and are output. The above explanation is for scanning the image memory 4 from top to bottom using horizontal scanning lines, but the same operation is performed when scanning the image memory 4 using vertical scanning lines. . As is clear from the above explanation, the intersection extraction method of the present invention is
This method has the advantage of being able to significantly reduce the number of processing steps compared to a method that performs line thinning processing, as well as being able to extract intersections with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the generation point, vanishing point, end point, and starting point of a stroke; FIG. 2 is a diagram for explaining intersection extraction using the end point and starting point; FIG. 3 is a diagram for explaining intersection extraction using the ending and starting points. FIG. 4 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a diagram explaining the identification of the generation point, vanishing point, start point, end point, and end point. Figure 6 is a diagram showing the intersection check zone for intersection detection. Figure 7 is the intersection check zone of Figure 6. 8 is a diagram showing another example of the intersection check zone. FIG. 9 is a diagram showing the intersection detection logic when the intersection check zone of FIG. 8 is used. It is. 1... Form, 2... Image input device, 3
...Quantization circuit, 4... Image memory,
5h...Horizontal scanning device, 5v...Vertical scanning device, 6h and 6v...Feature point extraction circuit, 7-1
. . . 1st scanning memory, 7-2 . . . 2nd
Scanning memory, 8... Continuous condition judgment circuit, 9...
...Width measurement circuit, 10...AND gate,
11...Line length counter, 12...Line length condition setting circuit, 13...Comparison circuit, 14...End point/start point identification circuit, 15...Generation point/vanishing point identification circuit, 16
...End point identification circuit, 17h and 17v...
...Data memory, 18...... Start point/end point coordinate calculation circuit, 19... Check zone setting circuit, 20...
Comparative circuit. 1 figure, 72 figures, 4 figures, 5 figures, 5 figures ■ 7 figures, 8 figures? figure

Claims (1)

[Claims] 1 comprising an image input device, a quantization device that quantizes image information from the image input device, an image memory in which the quantized image information is stored, and a scanning device that scans the image memory in a predetermined direction, In an intersection extraction method for extracting character intersections using scanning information output from the scanning device, a first scanning memory stores the scanning information output from the scanning device; a second scanning memory in which scanning information of is stored; a stroke for detecting whether or not a predetermined color element having a predetermined width or less continues for a predetermined length or more based on the contents of the first scan memory and the second scan memory; a detection means, an end point/start point identification means for identifying a stroke start point candidate point and a stroke end point candidate point based on the contents of the first scanning memory and the contents of the second scanning memory; and a stroke end point candidate point when the stroke detection means detects a stroke; Or an intersection characterized by having means for registering a stroke start point candidate point as a stroke end point or a stroke start point, and means for checking whether the stroke start point exists within an intersection check zone set with the stroke end point as a reference. Extraction method.