JP2004078411A - Method for automatic creation of sketch drawing and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sketch drawing which automatically expresses an original image as truthfully as possible from image data. <P>SOLUTION: An apparatus for automatic creation of a sketch drawing performs setting an edge sensitive parameter for edge detection (a step 130); setting a polygonal line approximation parameter for a polygonal approximation (a step 140); and setting a dust size parameter for deleting the image data with smaller than a predetermined size (a step 150). The apparatus performs processing to the image data of the original image in response to each parameter (steps 160-190) and draws a diagram (a step 200). The drawing of the diagram to the same original image are performed twice or more on the same drawing surface by changing at least one of the parameters. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for automatically drawing a sketch image.
[0002]
[Prior art]
There are many ways to draw sketches, such as writing on paper while looking at the object, or taking a picture of the object and tracing it.However, these methods are cumbersome and require drawing. The degree of completion of a figure is greatly affected by the drawing ability of the creator. On the other hand, as an automatic drawing of a sketch image by a computer, there is a method in which data of the above photographing is taken in, the edge of an object is detected, thinned, and then a line image is approximated by a broken line to create a sketch image. However, in this method, for example, in edge detection, a sufficient edge cannot be detected depending on an image, and a line image may be interrupted, so that a sufficiently clear sketch image cannot be obtained.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and has as its object to automatically draw a sketch image which is easy to work and faithfully represents an object.
[0004]
[Means for Solving the Problems]
An automatic sketch image creation method according to the present invention is a sketch image automatic creation method for drawing a line figure by performing respective processes on image data of an original image in accordance with values of a plurality of parameters. One is changed and the drawing of the line figure is performed twice or more on the same drawing. This makes it possible to describe a line figure that captures image data as faithfully as possible.
[0005]
Preferably, in drawing a line figure, thinning is performed. Preferably, the plurality of parameters are an edge sensitivity parameter for performing edge detection, a polygonal line approximation parameter for performing polygonal line approximation, and a dust size parameter for erasing image data of a predetermined size or less. Preferably, at least one of the plurality of parameters is arbitrarily set within a predetermined range.
[0006]
An apparatus for automatically creating a sketch image according to the present invention performs a process corresponding to a plurality of parameter values on image data of an original image to draw a line graphic, and changes at least one of the plurality of parameters. Means for instructing to draw a line graphic at least twice on the same drawing. This makes it possible to describe a line figure that captures image data as faithfully as possible.
[0007]
Preferably, in drawing a line figure, thinning is performed. Preferably, the plurality of parameters are an edge sensitivity parameter for performing edge detection, a polygonal line approximation parameter for performing polygonal line approximation, and a dust size parameter for erasing image data having a predetermined size or less. . Preferably, at least one of the plurality of parameters is set arbitrarily within a predetermined range. Further, the program according to the present invention is a program for causing a computer to perform a process corresponding to a plurality of parameter values on image data of an original image to draw a line graphic, and at least one of the plurality of parameters. And a function for instructing to draw a line graphic at least twice on the same drawing.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an external view of a compact camera which is an example of an original image. 2 and 3 show line figures drawn by the automatic sketch drawing apparatus. FIG. 2 shows a line figure drawn by one drawing, and FIG. 3 shows a line figure when a predetermined parameter is changed and drawing is performed a plurality of times. In the line figure of FIG. 2, for example, the feature of the image data of the original image is not sufficiently captured for a complicated portion, such as the upper left dial portion 10 being unclear. On the other hand, when a predetermined parameter is changed and drawing is performed a plurality of times, for example, as shown in FIG. 3, the upper left dial unit 10 is drawn clearly. As described above, in the present invention, features of the original image that cannot be captured by a single drawing are captured, and a line figure expressing the original image as faithfully as possible is drawn even in a complicated portion.
[0009]
FIG. 4 is a flowchart showing a sketch image automatic creation routine executed in the sketch image automatic creation device. In step 100, the original image is scanned using a line sensor and read as image data in the automatic sketch image creation device. In step 110, the read image data is subjected to gray scaling in which all pixel data are assigned 256 density values of white (0) to black (255) in accordance with the density of the image data. In step 120, data relating to the drawing on which the line graphic is drawn is initialized. The drawing is, for example, a display screen of a computer.
[0010]
In steps 130, 140, and 150, an edge sensitivity parameter for performing edge detection, a polygonal line approximation parameter for performing polygonal line approximation, and a dust size parameter for erasing image data smaller than a predetermined size are set. . At this time, each parameter is automatically and arbitrarily set within a range from the minimum value to the maximum value of each parameter stored in the automatic sketch drawing apparatus. That is, each parameter is randomly extracted in the range from the stored minimum value to the maximum value. The stored minimum or maximum value of each parameter or each parameter may be manually set.
[0011]
In step 160, the gray-scaled image data is subjected to edge detection by a known method according to the edge sensitivity parameter set in step 130. Here, the weight matrix shown in FIG. 5 is used, and the edge intensities for all the pixels are obtained. If each of the obtained edge intensities is larger than the edge sensitivity parameter set in step 130, it is recognized as an edge, and is converted to a value of 1 as a feature point, and is converted to a value of 0 if smaller than the parameter. In step 170, the image data generated by the feature point having a value of 1 is thinned by a known method.
[0012]
In step 180, the thinned image data is approximated by a broken line in accordance with the broken line approximation parameters set in step 140. Here, as shown in FIGS. 6, 7, and 8, after the number of intersections is calculated, vectorization is performed. In the thinned image data, all the feature points are regarded as points of interest, and as shown in FIG.
Number of intersections = Σf (k) (1−f (k + 1))
Where f (8) = f (0)
The number of intersections is obtained by the following equation. As shown in FIG. 7, the feature points are calculated as any one of the numbers of intersections 1, 2, 3, and 4 indicating end points, interior points, branch points, and intersections. Note that Σ indicates the sum for k = 0 to 7.
[0013]
After the number of intersections is determined, the feature points are vectorized as shown in FIG. Here, the image data is raster-scanned, one end point is detected, and starting from that point, a pixel adjacent to the end point is searched. Direction codes are assigned to adjacent pixels detected by the search using a chain code by a known method. Then, if the detected adjacent pixel is an internal point, further adjacent pixels are searched. If the detected adjacent pixel is an end point, the end point is set as an end point, vectorization is performed between the start point and the end point by piecewise linear approximation, and a search for a new start point is performed. If the detected adjacent pixel is a branch point or an intersection, these points are set as end points, vectorized by a piecewise linear approximation between the start point and the end point, and at the same time, the point is set as a new start point in two directions. Alternatively, adjacent pixels are searched for in three directions. These operations are performed until all the feature points are vectorized.
[0014]
FIG. 9 shows an example of piecewise linear approximation in vectorization. In a feature point group 30 which is a group of feature points to which a chain code is assigned, the found start point 31 and end point 32 are connected to form a line segment 33. Next, a broken line point 34 that is farthest from the line segment 33 and the feature point group 30 is detected. If the distance 36 between the detected broken line point 34 and the line segment 33 is equal to or greater than the set broken line approximation parameter, the point is divided into two new line segments 37 and 38 as the broken line point 34. If the distance 36 is less than the broken line approximation parameter, the line segment 33 is set as the approximate straight line of the feature point group 30. Also for each of the divided line segments 37 and 38, one of the farthest broken line points is found one by one as in the case of the line segment 33. If the distance between the line segments 37 and 38 and the corresponding broken line point is less than the broken line approximation parameter, the line segment is regarded as an approximate straight line. It is repeated until it is less than the parameter.
[0015]
In step 190, dust is removed from the image approximated by the broken line in step 180. That is, image data having a size equal to or smaller than the dust size parameter set in step 150 is deleted. In step 200, the image data from which dust has been removed is drawn as a line figure on the drawing whose data has been initialized in step 120.
[0016]
In step 210, it is determined whether or not the operations in steps 130 to 200 have been executed a predetermined number of times stored in advance. If the routine has been executed a predetermined number of times, this routine ends. If it has not been executed the predetermined number of times, steps 130 to 200 are performed again. At this time, each parameter is reset every time in steps 130 to 150, and in steps 160 to 190, data processing is performed according to each reset parameter, and different line figures are formed on the same drawing in step 200. Will be drawn. Note that, in the resetting of the parameters in the second and subsequent drawing, one of the parameters may be fixed and only the other parameters may be reset. Further, the predetermined number of times in step 200 may be set manually.
[0017]
For example, in the second line drawing, the same parameters as those in the first line drawing are set in steps 130 and 150, and in step 140, a polygonal line approximation parameter having a larger value than the first parameter is set. Thus, the edge detection and thinning in steps 160 and 170 and the calculation of the number of intersections in step 180 are performed in the same manner as the first line drawing. However, in the piecewise linear approximation in the vectorization in step 180, as shown in FIG. 10, by increasing the parameter, the distance 46 between the line segment 43 and the polygonal line point 44 becomes smaller than the polygonal line approximation parameter in a smaller division. Therefore, the number of break points is different from the first time, and the line figure to be drawn is also different. In the third and subsequent line drawing, other parameters are also changed, and line figures corresponding to various parameters are drawn on the same drawing each time.
[0018]
As described above, when the drawing is performed a plurality of times by changing the parameters, as shown in FIGS. 2 and 3, features that cannot be captured by a single drawing are captured, and the original image is faithfully reproduced even in a complicated portion. The expressed line figure is drawn.
[0019]
【The invention's effect】
According to the present invention, by automatic line drawing based on the image data of the original image, a sketch image accurately capturing the characteristics of the original image can be easily obtained.
[Brief description of the drawings]
FIG. 1 is an external view of a compact camera which is an example of an original image.
FIG. 2 is a line figure obtained by a single drawing by the automatic sketch drawing apparatus.
FIG. 3 is a line figure obtained by drawing a plurality of times with parameters changed by the automatic sketch drawing apparatus.
FIG. 4 is a flowchart showing an automatic sketch drawing routine executed in the automatic sketch drawing apparatus according to one embodiment of the present invention;
FIG. 5 is a weight matrix for performing edge detection in the present invention.
FIG. 6 is a reference diagram for calculating the number of intersections in the broken line approximation of the present invention.
FIG. 7 is a diagram illustrating the relationship between the number of intersections calculated in the calculation of the number of intersections and the feature points thereof.
FIG. 8 is a reference diagram of vectorization in the folding line approximation of the present invention.
FIG. 9 is a reference diagram of the piecewise linear approximation of the present invention.
FIG. 10 is a reference diagram of a piecewise linear approximation when a polygonal line approximation parameter is changed in the polygonal line approximation of the present invention.
[Explanation of symbols]
30 Feature point groups 34, 44 Fold line points 36, 46 Distance

Claims (9)

In a sketch automatic creation method for drawing a line figure by performing respective processes according to values of a plurality of parameters on image data of an original image, at least one of the plurality of parameters is changed, and A method for automatically creating a sketch, wherein drawing of a figure is performed twice or more on the same drawing. The sketch drawing automatic creation method according to claim 1, wherein thinning is performed in drawing the line figure. The plurality of parameters are an edge sensitivity parameter for performing edge detection, a polygonal line approximation parameter for performing polygonal line approximation, and a dust size parameter for erasing image data of a predetermined size or less. The sketch image automatic creation method according to claim 1. The method according to claim 1, wherein at least one of the plurality of parameters is arbitrarily set within a predetermined range. Means for performing a process corresponding to a plurality of parameter values on the image data of the original image to draw a line graphic, and changing at least one of the plurality of parameters to draw the line graphic at least Means for instructing to perform the same on the same drawing twice or more. The sketch drawing automatic creation device according to claim 5, wherein thinning is executed in drawing the line figure. The plurality of parameters are an edge sensitivity parameter for performing edge detection, a polygonal line approximation parameter for performing polygonal line approximation, and a dust size parameter for erasing image data of a predetermined size or less. The sketch picture automatic creation device according to claim 5. The sketch picture automatic creation device according to claim 5, wherein at least one of the plurality of parameters is arbitrarily set within a predetermined range. Means for drawing a line graphic by performing respective processes on the image data of the original image in accordance with the values of the plurality of parameters, changing at least one of the plurality of parameters, A program for functioning as means for instructing drawing to be performed at least twice on the same drawing.

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