JPH09270018A - Graphic plotting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a graphic plotting device capable of plotting a required line of high quality on any position of a circular arc or the like while holding its line width at a fixed value and plotting any line sort such as a broken line in a high quality state. SOLUTION: An initial value recognizing part 1 recognizes the size of a graphic such as a circle, circular arc, an ellipse, and an elliptic arc to be plotted and the width of its line. Then a circular arc segment scanning part 2 approximates a curve by a straight line, divides the straight line into plottable segments and stores the start and end points of respective segments in a segment start/end point storing part 3. A straight line coordinate generating part 4 generates a straight line passing from the start point of a certain segment up to its end point only by its line width and a normal vector generating part 5 rotates the generated straight line by 90 deg. to obtain a normal vector. On the other hand, a circular arc coordinate generating part 6 successively generates the coordinates of pixels on a circular arc in the segment and a plotting part 7 plots a normal vector started from the coordinates to be a start point and stores the plotted normal vector in a frame memory 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic drawing apparatus, and more particularly to a graphic thick line drawing apparatus for drawing a circle, an arc, an ellipse and an elliptic arc having a line width with high quality.

[0002]

2. Description of the Related Art In recent years, CAD (Computer Ai)
In ded Design) systems, computer graphics, and the like, the resolution of printers and plotters, which are devices that output figures and characters, is increasing. The higher the resolution, the more beautiful the figures and characters will be output. However, as the resolution becomes higher, the line of 1-dot width becomes very thin, which is not practical. Therefore, a function of drawing with a line having a line width of 2 dots or more is required. Further, in the CAD system, a circle, a circular arc, an ellipse, and an elliptic arc can express a curved line by combining them. Furthermore, not only the solid line, but also line types such as the one-dot chain line, the dotted line, and the broken line are often used.

The conventional graphic drawing apparatus has taken the following method when drawing a thick circle / arc.
FIG. 15 is an explanatory diagram of a drawing procedure of a conventional line segment drawing method. First, in the drawing method shown in FIG.
Since a circular arc having a line width of 1 pixel can be generated at high speed by the arc generating algorithm of reshenham, a thick line is drawn by overlapping several circular arcs. As a concrete example of this method, for example, an example of a straight line is described in JP-A-5-233821.

Next, in the drawing method shown in FIG. 15B, a contour line of an arc to be drawn is drawn in advance, and then a thick line is drawn by using a general filling process. As a specific example of this system, for example, an example of a straight line is described in JP-A-4-205575, JP-A-4-77977, and JP-A-5-67215.

Further, the drawing method shown in FIG.
A circular pixel pattern having a target line width as a diameter is drawn by moving the pixel pattern from the starting point to the ending point of the circular arc one pixel by one pixel based on the known Bresenham's circular arc generation algorithm, and painting the inside of the pixel pattern.

The drawing method shown in FIG. 15D is a method of drawing a curve by linear approximation. A specific example of this method is disclosed in, for example, Japanese Patent Laid-Open No. 4-128980.

By the way, the image quality or accuracy of the drawn circle is that the line width is constant at any position on the circumference. Also when drawing a broken line or the like, the image quality or accuracy is determined by the fact that the line segment length, line segment interval, and line width of the broken line are constant at any position on the circumference. Furthermore, it is necessary to align the shapes of the end points of each line segment with a straight line orthogonal to the drawing direction.

Considering each of the conventional drawing methods from such a point of view, first, in the drawing method shown in FIG. 15A, the number of thin lines required to keep the line width constant at any position on the circumference. Is difficult to calculate. Further, when drawing a broken line, it is difficult to control drawing of a thin line so that all end points of each line segment of the broken line are cut and aligned with a straight line orthogonal to the drawing direction.

In the drawing method shown in FIG. 15B,
When drawing a broken line, it is necessary to find the contour line including the end point shape for each line segment of the broken line, which may complicate the process when using the existing filling method, or require a huge memory. There is a problem that there is a property. In particular, when drawing the contour line of an ellipse, it is difficult to specify the parameters of the Bresenham's arc generation algorithm necessary for drawing the contour line of an ellipse whose line width is inward or outward from a certain ellipse. is there.

Since the drawing method shown in FIG. 15C uses a circular pixel pattern, the line width can be made substantially constant at any position of a circle, a circular arc, an ellipse, and an elliptic arc. However, the shape of the end point is limited to a semicircular shape. For example, when a broken line is drawn, the shape of the end point remains the shape of a semicircle of the pixel pattern, and a line segment having a length shorter than the diameter of the pixel pattern is used. However, there is a problem in that it cannot be drawn as it is.

Next, the drawing method shown in FIG. 15D will be examined. FIG. 16 is an explanatory diagram of a drawing procedure of a conventional line segment drawing method for drawing a curve by approximating it to a short straight line. FIG.
As shown in FIG. 6, in this method, a linear pixel row that is continuous only in the X-axis direction, the Y-axis direction, and the diagonal direction is extracted from the curve to be generated, and the pixel row is divided into line segments having a desired line width. Is a method of mapping to the original image. FIG.
When a curve as shown in (A) is generated with a width of 3 pixels,
It is divided into five linear pixel rows shown in the periphery of FIG.
Each is written back as 3 pixels wide. As a result, FIG.
It is possible to obtain the 3-pixel width curve shown in FIG.

In this method, for example, when it is attempted to draw a broken line, it is considered to be possible by switching whether or not to draw each pixel in each line segment or each line segment. However, in this method, since the line width of the line segment drawn diagonally is not accurate, the image quality of the broken line is deteriorated, and each line segment of the broken line is always formed by a straight line having only three kinds of directions, so that the line segment is always drawn. There is a problem that it is difficult to align with a straight line orthogonal to the direction.

From the above, it is difficult to perform high quality drawing of circles, arcs, ellipses, and elliptic arcs by the conventional drawing method. In addition, the present situation is that little consideration is given to high-quality drawing of broken lines and dotted lines.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and draws a high quality image while keeping a desired line width constant at any position of a circle, an arc, an ellipse and an ellipse arc. In addition, a line drawing, broken line, dotted line, and other line types other than the solid line can be drawn with high quality while maintaining a constant line segment length, line segment interval, and line width for each line element. It is intended to be provided.

[0015]

According to a first aspect of the present invention, there is provided a graphic drawing device having a function of drawing a circle, an arc, an ellipse, and an elliptic arc, which is drawn from input information. Of the circle, arc, ellipse and elliptic arc recognized by the initial value recognizing means, and a circle, an arc, an ellipse and an elliptic arc as a straight line based on the size and the thickness of the line. Arc segment scanning means for sequentially generating coordinates having an arc length equal to the line segment length of an approximate straight line that can be drawn by approximation, and the coordinates generated by the arc segment scanning means are approximated to a circle, arc, ellipse and elliptic arc. A segment start point / end point storage means for sequentially holding the coordinates of the start point and the end point of a line segment, an arc coordinate generation means for generating coordinates on the arc between the start point and the end point, and a straight line connecting the start point and the end point A linear coordinate generating means for generating a mark, and a length equal to the line width recognized by the initial value recognizing means, which is orthogonal to the straight line connecting the start point and the end point based on the coordinates generated by the linear coordinate generating means. A normal vector generating means for generating a pixel row having the same, and a drawing means for generating a pixel row generated by the normal vector generating means for each coordinate generated by the arc coordinate generating means and performing drawing. It is what

According to a second aspect of the present invention, in the figure drawing apparatus according to the first aspect, the circular arc segment scanning means recognizes the size and line of the circle, circular arc, ellipse or elliptic arc recognized by the initial value recognizing means. An arc segment coordinate generation means for generating coordinates on an arc based on the thickness, a distance calculation means for calculating the moving distance of the coordinates generated by the arc segment coordinate generation means, and a circle recognized by the initial value recognition means, A segment length calculating means for calculating a line segment length that can be drawn by approximating a circle, an arc, an ellipse and an elliptic arc with a straight line based on the size of the arc, the ellipse and the elliptic arc and the thickness of the line, and the segment length calculating means The segment scanning determining means for determining whether or not the moving distance calculated by the moving distance calculating means exceeds the line segment length.

According to a third aspect of the present invention, in the graphic drawing apparatus according to the first or second aspect, the drawing means determines the occurrence of pixel omission based on the arc coordinates obtained by the arc coordinate generation means. Pixel dropout determining means, normal vector drawing means for drawing along a normal vector starting from an arc pixel, and a segment for judging whether drawing by the normal vector drawing means is completed up to the end point of the segment It is characterized in that it is provided with an end condition judging means.

According to a fourth aspect of the present invention, in the figure drawing apparatus according to any one of the first to third aspects, the arc coordinate generating means generates coordinates on the arc between the start point and the end point. At this time, only at least a part of the coordinates on the circular arc is generated according to the line type to be drawn.

[0019]

1 is a block diagram showing a first embodiment of a graphic drawing apparatus of the present invention. In the figure, 1 is an initial value recognition unit, 2 is an arc segment scanning unit, 3 is a segment start point / end point storage unit, 4 is a linear coordinate generation unit, 5 is a normal vector generation unit, 6 is an arc coordinate generation unit, and 7 is Drawing part, 8
Is an end condition determination unit, and 9 is a frame memory.

The initial value recognition unit 1 recognizes the size and line thickness of a circle, an arc, an ellipse, and an elliptic arc to be drawn. The radius is recognized as the size of a circle or an arc, and the diameters of the X axis and the Y axis are recognized in the case of an ellipse or an elliptic arc. Furthermore, in the case of an arc or elliptical arc, the coordinates of the drawing start point and the drawing end point, the coordinates of the drawing start point or the drawing end point and the central angle, or the angle from a certain direction in which the drawing start point and the drawing end point exist Etc. are recognized. These can be obtained by interpreting drawing data input from an input device such as a keyboard or a mouse, or described in a file or a page description language given from another computer.

The circular arc segment scanning unit 2 scans the coordinates on the circular arc by a length equal to the optimum line segment length for approximating a circle, a circular arc, an ellipse, and an elliptic arc by a straight line.
This line segment length section is called a segment, and the line segment length is called a segment length. The segment length should be calculated from the radius and line width for circles and arcs, and from the X-axis and Y-axis diameters, the ratio of the X-axis diameter to the Y-axis diameter, and the line width for ellipses and elliptical arcs. You can The start point and end point of the segment are obtained by scanning the arc coordinates for a length equal to the segment length. The segment start point / end point storage unit 3 temporarily holds the coordinates of the start point and end point of the segment obtained by the arc segment scanning unit 2.

The linear coordinate generation unit 4 generates linear coordinates from the start point to the end point of the segment held in the segment start point / end point storage unit 3 by, for example, DDA or the like.
The normal vector generation unit 5 rotates the pixel row corresponding to the linear coordinates generated by the linear coordinate generation unit 4 by 90 ° only for the line width, and thereby the normal vector orthogonal to the straight line connecting the start point and the end point of the segment. To generate. Arc coordinate generation unit 6
Generates the coordinates on the arc between the start point and the end point of the segment held in the segment start point / end point storage unit 3. For example, Bresenha can be used to generate the coordinates on the arc.
For example, an arc generation algorithm of m can be used.

The drawing unit 7 draws a pixel array forming a normal vector with each coordinate on the arc generated by the arc coordinate generation unit 6 as the starting point of the normal vector generated by the normal vector generation unit 5. At this time, if there is a pixel that is not drawn between adjacent normal vectors, that pixel is also drawn. The end condition determination unit 8 determines whether or not the drawing from the drawing start point to the drawing end point is completed, and while the drawing up to the drawing end point is not completed, the processing of the arc segment scanning unit 2 and thereafter is executed. Make it repeat. The frame memory 9 is
The image drawn by the drawing unit 7 is held.

FIG. 2 is an explanatory diagram showing an example of a drawing procedure in the first embodiment of the graphic drawing apparatus of the present invention. Here, a case where an arc having a certain line width from the drawing start point to the drawing end point is drawn will be described as an example. Initial value recognition unit 1
Recognizes the radius of the arc to be drawn, the drawing start point, the drawing end point, the line width, and the like.

The arc segment scanning unit 2 scans from the start point on the arc for the maximum arc length that can be considered that the angles formed by the tangents of the pixels on the arc are substantially equal in the arc, and obtains the end point of the segment. FIG. 2 shows some of the segments. For example, a point a on an arc is used as a starting point, and an end point b of the segment obtained by scanning is obtained. The obtained coordinates of the start point a and the end point b of the segment are temporarily stored in the segment start point / end point storage unit 3.

Next, the straight line coordinate generation unit 4 scans a straight line passing from the start point a to the end point b of the segment stored in the segment start point / end point storage unit 3 by the line width, and the coordinates of the pixels on the straight line are scanned. To occur. The normal vector generation unit 5 rotates the coordinates generated by the linear coordinate generation unit 4 by 90 ° around the segment start point a to generate a normal vector aa ′.

On the other hand, the circular-arc coordinate generating section 6 has a start point a of the segment stored in the segment start point / end point storage section 3.
The coordinates of the pixels on the arc ab between the end point b and the end point b are sequentially generated from the point a. The drawing unit 7 regards the coordinates of each pixel on the arc ab generated by the arc coordinate generation unit 6 as the starting point of the normal vector and sets the normal vector aa ′ generated by the normal vector generation unit 5. Draw the constituent pixel columns. FIG.
In, the drawn normal vector is indicated by a thin arrow. At this time, if there is a pixel that is not drawn between adjacent normal vectors, that pixel is also drawn. In this way, the drawing of the segment between the start point a and the end point b is completed.

The end condition judging unit 8 confirms that the end point b is not the drawing end point, and starts the processing of a new segment having the point b as the start point. In the same manner, division into segments and drawing processing in each segment are performed in the same manner. In this way, an arc having the designated line width is drawn in the frame memory 9 from the drawing start point to the drawing end point.

The outer circumference of the arc thus drawn is
Since the pixels on the arc generated by the arc coordinate generation unit 6 are used as they are, the deterioration of the image quality is small. Further, since the line width is drawn by the normal vector, it is accurate and constant at any position on the circumference, and the end point shape is a straight line and orthogonal to the drawing direction.

Further, by processing the normal vector while switching between drawing and suppressing according to a specific pattern, a broken line, a dotted line, a chain line, etc. can be drawn with high accuracy. FIG.
FIG. 3 is an explanatory diagram of an example of drawing a broken line in the first embodiment of the graphic drawing apparatus of the present invention. In FIG. 3, for simplicity, each segment is assumed to include six normal vectors, and processing is performed while switching between drawing and inhibition every 5 dots. In such processing, for example, the coordinates of the pixels on the arc generated by the arc coordinate generation unit 6 are converted into the drawing unit 7
It is sufficient to control so that after sending five, the five are discarded without being sent. With such a simple control, as shown in FIG. 3, it is possible to draw a high-quality broken line in which the width and length of each line element, the interval between line elements, and the shape of line elements are uniform. The coordinates of the pixels on the arc generated by the arc coordinate generation unit 6 are drawn by the drawing unit 7.
It is possible to change the length of the line element and the interval between the line elements, and to draw the chain line such as the one-dot chain line and the two-dot chain line, simply by changing the rule (specific pattern) sent to the. This specific pattern may be given in advance by a numerical value, or may be given a function, for example, to be determined according to the line width or dynamically determined according to the radius or curvature.

It is also possible to draw multiple lines such as double lines by removing pixels when the normal vector is generated. The width between the lines at this time is also constant. Further, wavy lines are possible by periodically changing the pixels to be removed, and it is also possible to combine these with line types such as broken lines.

FIG. 4 is a block diagram showing a second embodiment of the graphic drawing apparatus of the invention. In the figure, the same parts as those in FIG. Reference numeral 11 is a segment length calculation unit, 12 is an arc segment coordinate generation unit, 13 is a movement distance calculation unit, and 14 is a segment scanning determination unit. In the second embodiment, a specific example of the arc segment scanning unit 2 in the above-described first embodiment is shown. Processing of a segment will be mainly described in detail using this embodiment.

The segment length calculation unit 11 calculates the segment based on the coordinates of the drawing start point and the drawing end point of the curve recognized by the initial value recognition unit 1, the line width, and in the case of an ellipse, the X-axis and Y-axis diameters. Calculate the segment length, which is the length of The arc segment coordinate generation unit 12 sequentially generates the coordinates of pixels on the arc. The coordinates of pixels on an arc can be generated using, for example, the well-known Bresenham arc generation algorithm. Moving distance calculation unit 1
3 calculates the moving distance from the coordinates of the pixel that is the start point of the segment to the coordinates of the pixel generated by the arc segment coordinate generation unit 12. The segment scanning determination unit 14 compares the segment length obtained by the segment length calculation unit 11 with the movement distance calculated by the movement distance calculation unit 13 to determine the end of the scanning of the segment. The generation unit 12 sends the start point and end point of the segment to the segment start point / end point storage unit 3.

Next, the operation of the graphic drawing apparatus according to the second embodiment of the present invention will be described. FIG. 5 is a flowchart showing an example of the operation of the segment length calculation unit according to the second embodiment of the present invention. In S31, it is determined whether the drawn curve is a circle or a circular arc, or an ellipse or an elliptic arc. If it is a circle or an arc, the radius recognized by the initial value recognition unit 1 is the radius used in the calculation of the maximum approximate straight line length below. If it is an ellipse or an elliptic arc, in S32, the radius used for the calculation of the maximum approximate straight line length from the values of the major axis and minor axis diameters of the ellipse recognized by the initial value recognition unit 1 (hereinafter, this radius is It is called the radius according to the diameter). This processing will be described later.

Next, in S33, based on the radius of the circle, or in the case of an ellipse, the radius corresponding to the diameter calculated in S32, the longest approximate straight line length within a range in which image quality deterioration is not recognized even if linear approximation is performed. Ask for. This processing will also be described later.

Then, in S34, the initial value recognition unit 1
The line width recognized in step S3 is compared with the maximum approximate straight line length calculated in step S33, and the smaller one is set as the segment length.
That is, if the maximum approximate straight line length is greater than or equal to the line width, S3
In 5 the segment length is the line width, and if the line width is longer than the maximum approximate straight line length, the segment length is set to the maximum approximate straight line length in S36. In this way, the segment length calculation unit 11 calculates the segment length.

FIG. 6 is an explanatory diagram of an example of the operation of radius calculation according to the diameter at the time of segment length calculation in the second embodiment of the present invention. In order to easily obtain the radius according to this diameter, in this example, the region is divided into a sharp curve region and a gentle curve region, and a radius corresponding to the radius is determined for each region for convenience. As shown in FIG. 6, the intersection with the major axis and its vicinity are defined as the steep curve region 2, and the intersection with the minor axis and its vicinity are defined as the gentle curve region 1. Then, the threshold Th for dividing into two regions
Has a ratio of the major axis diameter to the minor axis diameter of 4: 1 or less, that is, A ≦ 4.
In the case of xB, it is half of the short axis (B / 2), and is larger than 4: 1.
4). Although only the first quadrant is shown in FIG. 6, the same applies to the other quadrants.

FIG. 7 is a flow chart showing an example of the operation of calculating the radius according to the diameter when calculating the segment length in the second embodiment of the present invention. The calculation operation of the radius according to the diameter by the method shown in FIG. 6 is shown in FIG. First, in S41, the ratio of the major axis and minor axis diameters (A /
If B) is less than 1.5, it is regarded as a circle, and the radius of the minor axis B is adopted as the radius in S42.

When the ratio (A / B) of the diameters of the major axis and the minor axis is 1.5 or more, it is regarded as an ellipse, and each quadrant is divided into two regions as shown in FIG. Calculate the radius. In S43, it is determined whether or not it is included in the region 2. If it is determined that it is included in the region 2, in S44, the radius of half the short axis (B / 2) is set regardless of the value of the diameter. When it is included in the region 1, the diameter ratio is sequentially determined in S45 and S47. If the ratio (A / B) of the major axis diameter to the minor axis diameter is 1.5 or more and less than 2.5 in S45, the radius corresponding to the diameter is determined to be the major axis diameter A and the minor axis diameter B in S46. Be sum When the ratio (A / B) of the diameters of the major axis and the minor axis is 2.5 or more and less than 3.5 in S47,
In S48, the radius corresponding to the diameter is set to twice the sum of the diameter A of the major axis and the diameter B of the minor axis. If it is more than that, S4
In FIG. 9, the radius corresponding to the diameter is set to be three times the sum of the major axis diameter A and the minor axis diameter B. The value of the radius according to these diameters is an example, and may be another value.

When the figure to be drawn is an ellipse or an ellipse, the radius corresponding to the diameter was calculated as described above. If the figure to be drawn is a circle or a circular arc, the radius is recognized by the initial value recognition unit 1. Based on these radii or radii corresponding to the diameters, the longest approximated straight line length is obtained within a range in which the image quality deterioration is not so much recognized even if the linear approximation is performed. FIG. 8 is a flowchart showing an example of the operation of calculating the maximum approximate straight line length based on the radius in the second embodiment of the present invention. Here, the radius corresponding to the diameter is also simply called the radius.

The maximum approximate straight line length is divided into three cases by S51 and S53 depending on the radius, and S5 and S5 respectively.
It is calculated by the calculation formula derived from the experiments shown in 2, S54 and S55. That is, the radius is 400 in S51.
If it is smaller than 400, the maximum approximate straight line length is set to 5 + 0.0625 × radius in S52. Further, in S53, the radius is 400 or more and 10
It is determined whether it is less than 00, and if it is within the range, S54
In, the maximum approximate straight line length is 25 + 0.03125 × radius. When the radius is 1000 or more, the maximum approximate straight line length is 50 + 0.00781 × radius. S52, S5
4, the coefficients used to multiply the radius used in S55 are 2 ⁻⁴ , 2 ⁻⁵ , and 2 ⁻⁷ , respectively, which improves the calculation speed by making the binary multiplication by the computer possible by the shift. The maximum approximate straight line length thus obtained is compared with the radius, and the shorter one is adopted as the segment length.

FIG. 9 is an explanatory diagram showing an example of the coordinates of pixels generated by the arc segment coordinate generator and the arc segment in the second embodiment of the present invention. The arc segment coordinate generation unit 12 is, for example, a well-known Bresenham.
Based on the arc generation algorithm of 1), the coordinates of the pixels shown by circles in FIG. 9 are generated in order from the start point of the segment. In FIG. 9, the pixel at the starting point of the segment is indicated by ●, and the pixels that are sequentially generated are indicated by ◯. In addition, the pixel at the end point of the segment is indicated by ⊚.

Coordinates of pixels hatched with ◯ are sequentially generated from the pixel ● at the start point of the segment. Each time, the movement distance calculation unit 13 calculates the movement distance from the pixel at the start point of the segment. Then, the segment scan determination unit 14 compares the segment length obtained by the segment length calculation unit 11 with the movement distance calculated by the movement distance calculation unit 13 to determine the end point of the segment. In FIG. 9, if the moving distance calculated by the moving distance calculating unit 13 reaches the segment length at the time when the pixel coordinates indicated by ⊚ are generated, the segment scanning determining unit 14 detects this and It is determined that the pixel indicated by is the end point of the segment. In addition, the segment scanning determination unit 14
If the drawing end point is reached before the movement distance reaches the segment length, the drawing end point is determined to be the end point of the segment. When the end point of the segment is detected, the coordinates of the start point and end point of the segment are calculated from the arc segment coordinate generation unit 12 and the segment start point / end point storage unit 3
Send to

FIG. 10 is an explanatory diagram of an example of the operation of the moving distance calculating section. In this example, in order to reduce the calculation error of the movement distance, the movement distance calculation unit 23 uses the 2
The calculation is performed using the distance between these two coordinates as far back as the pixel coordinates. As shown in FIG. 10, when a pixel (hereinafter referred to as the next pixel) Pn that is newly generated from a pixel (hereinafter referred to as the current pixel) Pn that is generated last at the present time is generated, the movement distance calculation unit 13 First, the provisional movement distances Pn to Pn + 1 to the next pixel are calculated. At this time, the unit distance between adjacent coordinates is 1 in both the x-axis direction and the y-axis direction.
Then, since the image has pixels in a grid pattern, the provisional movement distance is either 1.0 or √2. Furthermore, the movement distances Pn-1 to Pn from the pixel (hereinafter referred to as the previous pixel) generated before the current pixel held by the movement distance calculation unit 13
And the moving distances Pn to Pn + 1 to the next pixel are newly calculated based on the previous temporary moving distances Pn to Pn + 1. That is, the moving distance values of consecutive pixels are 1.0 and √.
Only in the case of 2 or √2 and 1.0, these are collectively set to √5 by Pythagorean theorem.

In the example shown in FIG. 11, Pn-1 to Pn =
1.0, Pn-Pn + 1 = √2, Pn-1 to Pn + 1
= √5, Pn to Pn + 1 = (√5-
1.0) is output as the movement distance. After the movement distance is calculated, the value of Pn to Pn + 1 (√5-1.0) is Pn + 1.
It is held in the moving distance calculation unit 23 for the calculation of the moving distance from to Pn + 2.

FIG. 11 is a flow chart showing an example of the operation of the moving distance calculating section. In S61, the provisional movement distance to the next pixel generated by the arc segment coordinate generation unit 12 is input. Hereinafter, the value of this provisional movement distance is Dn. Further, the movement distance from the previous pixel held in the movement distance calculation unit 13 is input. Hereinafter, the value of this moving distance is defined as Dp.

The moving distance calculation unit 13 determines the provisional moving distance Dn.
And, the case is divided according to the value of the moving distance Dp, and the added distance in each case is obtained. In S62, it is determined whether or not the provisional movement distance Dn is 1. When the provisional movement distance Dn is 1, it is further determined in S63 whether the movement distance Dp is √2. Moving distance Dp
Is not √2, in S64, the addition distance from the current coordinate Pn to the next coordinate Pn + 1 is set to 1 and added to the cumulative distance. If the moving distance Dp is √2, S
At 65, the addition distance from the current coordinate Pn to the next coordinate Pn + 1 is set to √5-√2 and added to the cumulative distance. S6
If it is determined in 2 that the provisional movement distance Dn is not 1, it is further determined in S66 whether the movement distance Dp is 1. If the moving distance Dp is 1, S67
In, the addition distance from the current coordinate Pn to the next coordinate Pn + 1 is set to √5-1 and added to the cumulative distance. If the moving distance Dp is not 1, in S68, the addition distance from the current coordinate Pn to the next coordinate Pn + 1 is set to √2,
Add to cumulative distance.

The second embodiment shows an example of the configuration of the arc segment scanning unit 2 in the first embodiment. The processing after the coordinates of the pixel of the start point and the point of the end point of the segment are stored in the segment start point / end point storage unit 3 is the same as that of the above-described first embodiment, and therefore the description thereof is omitted here.

FIG. 12 is a block diagram showing the third embodiment of the thick graphic line drawing apparatus of the present invention. In the figure, the same parts as those in FIG. 21
Is a pixel omission determination unit, 22 is a normal vector drawing unit, and 23 is a segment end condition determination unit. In the third embodiment, a concrete example of the drawing unit 7 in the above-described first embodiment is shown. A drawing process mainly using a normal vector will be described in detail using this embodiment.

The pixel omission determination unit 21 is provided with an arc coordinate generation unit 6
On the basis of the coordinates of the pixels on the arc generated in step 1, it is determined whether or not pixel omission occurs when drawing with the normal vector generated by the normal vector generation unit 5, and the coordinates of the pixels on the arc are determined. At the same time, the determination result is transmitted to the normal vector drawing unit 22.

The normal vector drawing unit 22 draws the normal vector generated by the normal vector generation unit 5 based on the coordinates of the pixel on the circular arc generated by the circular arc coordinate generation unit 6 with that pixel as the starting point. To do. If the pixel omission determination unit 21 determines that pixel omission occurs, the pixel omission is also removed.

The segment end condition judging unit 23 judges whether or not the pixels on the circular arc generated by the circular arc coordinate generating unit 6 have reached the end point of the segment. The coordinate generation unit 6 is instructed to generate the coordinates of the pixel on the next arc.

Next, an example of the operation in the third embodiment of the present invention will be described using a specific example. Here, a process after the pixel coordinates of the start point and the end point of the segment are stored in the segment start point / end point storage unit 3 will be described. As a specific example, it is assumed that the coordinates of the pixel  at the start point and the pixel ∘ at the end point of the segment are stored in the segment start point / end point storage unit 3 as shown in FIG.

FIG. 13 is an explanatory diagram of a process of creating a normal vector according to the third embodiment of the present invention. The straight-line coordinate generation unit 4, based on the coordinates of the start point and end point pixels of the segment held in the segment start point / end point storage unit 3, as shown in FIG. Generate pixel coordinates. In FIG.
The generated pixels are indicated by circles and crosses. The distance from the start point of the segment to the coordinates of the generated pixel can be calculated in the same manner as the processing in the moving distance calculation unit 13 in the above-described second embodiment. Then, by comparing the calculated distance with the line width, it is possible to determine whether or not a pixel on a straight line corresponding to the line width has been generated.

The normal vector generating unit 5 calculates the line width based on the coordinates of the pixels generated by the linear coordinate generating unit 4.
Rotate them 90 ° around the start of the segment,
In FIG. 13, a normal vector that is orthogonal to the end point direction of the segment and has a length of the line width is generated as in the pixel row indicated by ●.

FIG. 14 is an explanatory diagram of a segment drawing process based on a normal vector according to the third embodiment of the present invention. After the normal vector is generated in the normal vector generation unit 5, the circular-arc coordinate generation unit 6 uses, for example, Br.
The coordinates of pixels on the arc from the start point to the end point of the segment are sequentially generated using the esenham arc generation algorithm or the like. Then, the normal vector drawing unit 22 draws the normal vector generated by the normal vector generation unit 5 using the coordinates generated by the arc coordinate generation unit 6 as the starting point of the normal vector. The drawing of this normal vector is performed for each coordinate generated by the arc coordinate generation unit 6.

However, when the pixels on the arc move obliquely as shown in FIG. 14, pixel omission occurs like the pixels indicated by Δ in FIG. Therefore, the pixel omission determination unit 2
1 detects that the pixel has moved diagonally based on the coordinates of the pixel on the arc generated by the arc coordinate generation unit 6 and determines that the pixel is missing. Pixels with missing pixels are filled in the normal vector drawing unit 22 to remove missing pixels.

The generation of the coordinates of the pixel on the arc by the arc coordinate generation unit 6 is performed until the segment end condition determination unit 23 determines the end point of the segment, and when the end point of the segment is reached, the drawing in the segment is ended. This allows
Drawing in one segment is performed as shown in FIG. At this time, the pixel missing portion indicated by Δ is also filled. Since the drawn only segment length figure draws the normal vector starting from the pixel on the arc, the shape of the figure formed by the pixel at the end of the normal vector is also an arc, which improves the image quality. it can. Further, since the normal vector according to the line width is used, the line width is uniform.

Further, the above processing is performed for each segment until the end condition judging section 8 recognizes the final end point,
A line from the drawing start point to the drawing end point is drawn. At this time, at the boundary of each segment, a normal vector is generated so as to be inside the curve, so that the ends of the two segments are drawn so as to be adjacent to each other or slightly overlap. Therefore, no pixel dropout occurs between the segments.

In the above-mentioned example, since the normal vector is generated inside the curve, it is assumed that the arc or elliptic arc is scanned in the counterclockwise direction around the center of the circle or ellipse, and when the normal vector is generated. Is rotated 90 ° counterclockwise around the start point of the segment. Of course, the configuration may be such that a circular arc or an elliptic arc is scanned in the clockwise direction and the normal vector is rotated. Further, the scanning direction of the arc or the elliptical lake and the rotation direction of the normal vector may be different, and the end point of the normal vector may be drawn according to the pixel on the arc generated by the arc coordinate generation unit 6. .

Further, as described in the above-mentioned first embodiment, according to the present invention, it is possible to draw a broken line, a dotted line, a chain line, etc. by performing processing while switching drawing and suppression according to a specific pattern. In such a drawing / suppression switching process, for example, when the coordinates of the pixel on the arc are generated in the arc coordinate generation unit 6, only the coordinates of the pixel on the arc of the drawing portion are passed to the drawing unit 7. In addition to the configuration, the normal vector drawing unit 22 in the drawing unit 7 may also be configured to draw while drawing a normal vector while determining whether to draw the normal vector according to a specific pattern. it can.

In the second embodiment described above, an example of the internal configuration of the arc segment scanning unit 2 is shown, and in the third embodiment, an example of the internal configuration of the drawing unit 7 is shown. You may comprise combining.

[0063]

As is apparent from the above description, according to the present invention, a desired line width is kept constant at any position of a circle, a circular arc, an ellipse, and an elliptic arc, and pixels on the inner and outer circumferences have a circular arc. Is used, it is possible to draw a graphic with good image quality. Further, the end point shape can be drawn by a straight line orthogonal to the drawing direction. Further, even when a broken line or the like is drawn, it is possible to draw only by simple control, and the drawn broken line or the like is obtained in which the line elements are aligned and the intervals between the line elements are aligned, and the like. The effect is that you can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a graphic drawing apparatus of the present invention.

FIG. 2 is an explanatory diagram of an example of a drawing procedure in the first embodiment of the graphic drawing apparatus of the present invention.

FIG. 3 is an explanatory diagram of an example of drawing a broken line in the first embodiment of the graphic drawing apparatus of the present invention.

FIG. 4 is a block diagram showing a second embodiment of a graphic drawing apparatus of the invention.

FIG. 5 is a flowchart showing an example of operation of a segment length calculation unit in the second embodiment of the present invention.

FIG. 6 is an explanatory diagram of an example of a radius calculation operation according to a diameter when calculating a segment length according to the second embodiment of the present invention.

FIG. 7 is a flowchart showing an example of an operation of calculating a radius according to a diameter when calculating a segment length according to the second embodiment of the present invention.

FIG. 8 is a flowchart showing an example of an operation of calculating a maximum approximate straight line length based on a radius in the second embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an example of pixel coordinates generated by an arc segment coordinate generation unit and an arc segment according to the second embodiment of the present invention.

FIG. 10 is an explanatory diagram of an example of an operation of a moving distance calculation unit.

FIG. 11 is a flowchart showing an example of the operation of the movement distance calculation unit.

FIG. 12 is a block diagram showing a third embodiment of the thick graphic line drawing apparatus of the present invention.

FIG. 13 is an explanatory diagram of a process of creating a normal vector according to the third embodiment of the present invention.

FIG. 14 is an explanatory diagram of a segment drawing process based on a normal vector according to the third embodiment of the present invention.

FIG. 15 is an explanatory diagram of a drawing procedure of a conventional line segment drawing method.

FIG. 16 is an explanatory diagram of a drawing procedure of a conventional line segment drawing method for drawing a curve by approximating it to a short straight line.

[Explanation of symbols]

1 ... Initial value recognition unit, 2 ... Arc segment scanning unit, 3 ... Segment start / end point storage unit, 4 ... Linear coordinate generation unit, 5 ...
Normal vector generation unit, 6 ... Arc coordinate generation unit, 7 ... Drawing unit, 8 ... End condition determination unit, 9 ... Frame memory, 11 ...
Segment length calculation unit, 12 ... Arc segment coordinate generation unit, 13 ... Moving distance calculation unit, 14 ... Segment scan determination unit, 21 ... Pixel omission determination unit, 22 ... Normal vector drawing unit, 23 ... Segment end condition determination unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Shimada 430 Sakai Nakai-cho, Ashigagami-gun, Kanagawa Green Tech Nakakai Fuji Xerox Co., Ltd. Within

Claims (4)

[Claims] 1. An initial value recognition for recognizing the size and line thickness of a circle, an arc, an ellipse or an elliptic arc drawn from input information in a graphic drawing device having a function of drawing a circle, an arc, an ellipse or an elliptic arc. And a line segment length of an approximate straight line that can be drawn by approximating a circle, an arc, an ellipse, and an elliptic arc with a straight line based on the size and thickness of the circle, arc, ellipse, and elliptic arc recognized by the initial value recognition means. Arc segment scanning means for sequentially generating coordinates having an arc length equal to and a segment for sequentially holding the coordinates generated by the arc segment scanning means as coordinates of a start point and an end point of a line segment approximating a circle, arc, ellipse, or ellipse arc. Start point / end point storage means, arc coordinate generation means for generating coordinates on the arc between the start point and end point, linear coordinate generation means for generating coordinates on a straight line connecting the start point and end point, and the straight line A normal vector generation means for generating a pixel row orthogonal to a straight line connecting the start point and the end point based on the coordinates generated by the coordinate generation means and having a length equal to the line width recognized by the initial value recognition means; A graphic drawing apparatus comprising: drawing means for generating a pixel array generated by the normal vector generation means for each coordinate generated by the arc coordinate generation means and performing drawing. 2. An arc segment coordinate generation means for generating coordinates on the arc based on the size of the circle, arc, ellipse and elliptic arc and the thickness of the line recognized by the initial value recognition means. A distance calculating means for calculating a moving distance of the coordinates generated by the arc segment coordinate generating means, and a circle, an arc based on the size and line thickness of the circle, arc, ellipse and elliptic arc recognized by the initial value recognizing means. A segment length calculating means for calculating a line segment length that can be drawn by approximating an ellipse and an elliptic arc with a straight line, and whether the moving distance calculated by the moving distance calculating means exceeds the line segment length calculated by the segment length calculating means. The graphic drawing apparatus according to claim 1, further comprising a segment scanning determining unit that determines whether or not the drawing is performed. 3. The drawing means draws along a normal vector starting from an arc pixel and a pixel missing determination means for judging occurrence of pixel omission based on the arc coordinates obtained by the arc coordinate generation means. 3. The normal vector drawing means, and the segment end condition judging means for judging whether or not the drawing by the normal vector drawing means is completed up to the end point of the segment. Drawing device. 4. The arc-coordinate generating means, when generating the coordinates on the arc between the start point and the end point, generates only at least a part of the coordinates on the arc according to the line type to be drawn. The graphic drawing apparatus according to any one of claims 1 to 3.