JPH04352290A - Straight line drawing device - Google Patents

Abstract

PURPOSE:To provide the straight line drawing device which draws a straight line at a high speed. CONSTITUTION:A drawing point quantity determination variable register 43 outputs a negative or nonnegative value at a specific period and specific frequency, a drawing point quantity determination variable and drawing point quantity control part 47 outputs the quotient (n) of the integral division of the numbers of (x)-axial and (y)-axis drawing points or a value n+1 according to the output value, and a horizontal line drawing part 51 draws a horizontal line of the number (n) or (n+1) of drawing points in each (y) coordinate value. Then the horizontal line is drawn at a time up to the coordinate point where the (x) coordinate and (y) coordinate vary at the same time, so the straight line is drawn at a high speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straight line drawing device applied to a graphics display system for displaying images on a bitmap display.

0002

2. Description of the Related Art Conventionally, Bresenham's line segment algorithm has been known as an algorithm for drawing straight lines. The above algorithm can be used, for example, in "Computer Graphics", by J.D. Foley et al.
Translated by Atsumi Imamiya, published by Japan Computer Association (1984)
, pp. 443-446.

[0003] This type of algorithm will be explained below based on the flowchart shown in FIG. Here, the starting point coordinates of the straight line to be drawn are (x1, y1), and the ending point coordinates are (
x2, y2), and for simplicity, x1<x2, y1<y
2, and the slope of the straight line is a value between 0 and 1. In addition,
If the numbers of grid points in the x-axis direction and y-axis direction from the start point to the end point are Δx and Δy, respectively, Δx=x2−x1
+1, Δy=y2−y1+1.

First, x1, y are the initial values of variables x, y.
Set 1. Furthermore, the initial value of the drawing point determination variable d is set to d=Δy−Δx (S401). Next, the sign of the drawing point determining variable d is determined (S402), and if it is negative, Δy is added to this drawing point determining variable d (S403).
On the other hand, if it is non-negative, Δy−Δx is added (S404
) and increase the value of the variable y by 1 (S405)
.

[0005] After that, one point indicated by the coordinates (x, y) is drawn (S406), and the value of the variable x is increased by 1 (S407). The process from S402 onward is repeated until the result is YES (S408). An example of a straight line drawing device that applies the above algorithm is the one shown in Figure 5.
A configuration as shown in is possible.

In FIG. 5, reference numeral 10 denotes a drawing section that outputs the coordinates of a drawing point. 11 is a register that stores the value Δy−Δx. 12 is a register that stores the value Δy. Reference numeral 13 denotes a drawing point determination variable register for storing a drawing point determination variable d, and the value Δy−Δx is stored as an initial value.

Reference numeral 14 denotes an adder that adds the contents of the register 11 and the contents of the drawing point determination variable register 13. 15
is an adder that adds the contents of the register 12 and the contents of the drawing point determination variable register 13. A selector 16 selects and outputs one of the addition results of the adders 14 and 15 based on a switching control signal from a drawing point determination variable/coordinate change amount control unit 17, which will be described later.

Reference numeral 17 indicates a switching control signal to the selector 16 based on the sign s of the drawing point determining variable d output from the drawing point determining variable register 13, and a switching control signal x from the previous drawing point to the next drawing point. This is a drawing point determination variable/coordinate change amount control unit that calculates and outputs the amount of change in coordinates and y coordinates. 1
Registers 8 and 19 respectively store the x and y coordinates of the drawing point, and the value x1 or the value y1 is stored as an initial value.

Reference numeral 20 inputs the drawing point determination variable/coordinate change amount control unit 1 to the x and y coordinates stored in the registers 18 and 19.
This is an x, y coordinate calculation unit that adds the amount of change output from 7 to obtain the coordinates of the drawing point, updates the registers 18 and 19, and outputs the coordinates of the drawing point. 21 indicates that the coordinate x of the drawing point stored in the register 18 is the coordinate x of the end point.
This is an end determination unit that determines whether the straight line drawing process has ended or not by checking whether the straight line has become larger than 2 or not.

Reference numeral 22 denotes a control section that controls the operation of the drawing section 10 from when the activation signal is input until the end judgment section 21 judges that the drawing process has ended. With this configuration, based on the control of the control unit 22, the drawing point determination variable/coordinate change amount control unit 17 and the selector 16 execute S402, and the adders 14 and 15 execute S404 and S403, respectively. The x, y coordinate calculation unit 20 executes S405 to S407, and the end determination unit 21
By executing S408, the x, y coordinates of the drawing point from the starting point to the ending point are output from the x, y coordinate calculation unit 20.

[0011] Therefore, based on the values of the above x and y coordinates,
By mapping an image memory (not shown), a straight line from the starting point to the ending point is drawn.

0012

[Problems to be Solved by the Invention] However, the above-mentioned conventional line drawing device has the problem that it takes a long time to draw a straight line because the coordinates of the drawing points are determined one by one. . In particular, the above problem is, for example, G
UI (graphical user interface)
An interactive operating environment called ce) and CAD
With the spread of (computer aided design) systems and the increase in resolution of graphics display systems, this problem is becoming more prominent.

In view of the above points, the present invention aims to provide a straight line drawing device that can draw straight lines at high speed without using arithmetic elements capable of high speed operation.

[0014]

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a straight line drawing device for drawing a straight line connecting a starting point and an ending point. A partial straight line drawing means in the coordinate axis direction is provided for drawing a partial straight line consisting of a predetermined number of drawing points in the direction of the other coordinate axis for each coordinate value between the starting point and the end point in the coordinate axis with the smaller number of drawing points in the direction of the other coordinate axis. It is characterized by

[0015]

[Operation] With the above configuration, the coordinate axis direction partial straight line drawing means can draw each straight line between the starting point and the ending point in the coordinate axis which has the smaller number of drawing points in the coordinate axis direction between the starting point and the ending point, of the first coordinate axis and the second coordinate axis. For each coordinate value, a partial straight line consisting of a predetermined number of drawing points in the direction of the other coordinate axis is drawn. That is, the drawing process is performed only once for each predetermined number of drawing points that have the same coordinate value on one side.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Here, the starting point coordinates of the straight line to be drawn are (x1, y1), the ending point coordinates are (x2, y2), and for simplicity, x1 < x2, y1 < y2, and the slope of the straight line is 0.
and 1. Note that the number of grid points in the x-axis direction and y-axis direction from the start point to the end point are Δx and Δ
If y, Δx=x2-x1+1, Δy=y2-y1
+1. Further, the width of the straight line to be drawn is assumed to be h.

FIG. 1 is a block diagram showing the configuration of a straight line drawing device. In FIG. 1, 31 inputs the values Δx and Δy, the quotient n of integer division Δx/Δy, and the value (n+1)・Δy−Δ
This is an initial value calculation unit that calculates x and the value n·Δy−Δx. Note that the above quotient n is the basic number of drawing points, and the number of drawing points of a straight line drawn in the x-axis direction is n or n as described later.
Set to +1.

Reference numeral 32 denotes an initial value correction section that calculates the value x1-(h-1)·n/2 based on the above-mentioned quotient n and the straight line width h, and outputs the value x1-(h-1)·n/2. Note that if the straight line width h is 1, the starting point x
The coordinate x1 will be output as is. 40 is a drawing unit that performs drawing processing. 41 is a register that stores the value n·Δy−Δx output from the initial value calculation unit 31.

Reference numeral 42 is a register that stores the value (n+1)·Δy−Δx output from the initial value calculation unit 31. 4
3 is a drawing point number determining variable register that stores the drawing point number determining variable D, and the value (n+1)·Δy−Δx output from the initial value calculation unit 31 is stored as an initial value.

Reference numeral 44 denotes an adder that adds the contents of the register 41 and the contents of the drawing point number determining variable register 43. 4
5 is the contents of register 42 and drawing point number determination variable register 4
This is an adder that adds the contents of 3. 46 selects and outputs one of the addition results of the adders 44 and 45 based on a switching control signal from a drawing point number determining variable/drawing point number control unit 47, which will be described later, and updates the contents of the drawing point number determining variable register 43. This is an additional value selector.

47 is a drawing point number determining variable/drawing point number control which outputs a switching control signal to the addition value selector 46 and the number of drawing points n or n+1 in the x-axis direction based on the sign s of the drawing point number determining variable D. Department. Reference numeral 48 denotes a drawing point number correction section which multiplies the drawing point number n or n+1 outputted from the drawing point number determination variable/drawing point number control section 47 by the straight line width h and outputs the result. Note that if the width h of the straight line to be drawn is 1,
The value n or n+1 output from the drawing point number determining variable/drawing point number control unit 47 is output as is.

Reference numeral 49 is a register for storing the x coordinate of the end point of a horizontal line drawn by the horizontal line drawing section 51, which will be described later.
1)·n/2 is stored. A register 50 stores the y-coordinate of a horizontal line drawn by the horizontal line drawing unit 51, and the value y1 is stored as an initial value.

Reference numeral 51 denotes a horizontal line drawing section that draws a horizontal line in the x-axis direction based on the contents of the registers 49 and 50 and the number of drawing points n.h or (n+1).h output from the drawing point number correction section 48. be. This horizontal line drawing section 51 is
Also, the contents of the register 49 are updated to the value n output from the drawing point number determination variable/drawing point number control section 47 or a value obtained by adding n+1, and the contents of the register 50 are updated to a value obtained by adding 1. It has become.

61 is the variable l which is the number of times the horizontal line is drawn.
This is a register that stores the value of oop, and the value Δy is set as the initial value.
is stored. Reference numeral 62 denotes a control unit that controls the operation of the drawing unit 40, which subtracts the value of the variable loop stored in the register 61 by 1 every time a horizontal line is drawn once after the activation signal is input, and When the value becomes 0, the drawing operation is stopped.

In the above configuration, the operation performed by the linear drawing device when the activation signal is input to the control section 62 will be explained based on the flowchart shown in FIG. First, the initial value calculation unit 31 calculates the quotient n of the integer division Δx/Δy based on the input values Δx and Δy (S201), and further calculates the value n・Δy−Δx and the value (n+1)・Δy −Δ
Calculate x and store it in registers 41 to 43 (S20
2).

On the other hand, the initial value correction section 32 calculates the value x1-(h
-1)·n/2 is calculated and stored in the register 49, and the values y1 and Δy are stored in the registers 50 and 61, respectively (S203). Next, the drawing point number determining variable/drawing point number control unit 47 determines the sign of the drawing point number determining variable D (
S204), if negative, the value n+1 is output as the number of drawing points to the horizontal line drawing unit 51 and the number of drawing points correction unit 48, and the number of drawing points correction unit 48 calculates the value (n+1)·h and outputs it to the horizontal line drawing unit 51. Output. Therefore, the horizontal line drawing unit 51 moves from the coordinates (x, y) to the coordinates (x+(n+1)・h−1,y
) (S205), the value stored in the register 49 (the x-coordinate of the end point of the next horizontal line to be drawn) is increased by n+1 (S206). Further, the drawing point number determining variable/drawing point number control unit 47 outputs a switching control signal to the addition value selector 46 to select the adder 45, and the contents of the drawing point number determining variable register 43 are (n+1)・Δy−Δx will be updated to the value increased by (
S207).

In more detail, the drawing of the horizontal line is, for example, from the coordinates (x, y) to the coordinates (x+(n+1)·
This is performed by generating an address of an image memory (not shown) corresponding to the drawing point for each coordinate up to h-1, y), and writing drawing data into a storage area indicated by the address. In this way, even when the drawing data is written for each drawing point, the addition process by the adders 44 and 45 only needs to be performed once for drawing one horizontal line, so the drawing time is short. I'll try it. Note that when the image memory is accessed by byte or word, the drawing data included in the same byte or word can be written simultaneously, which reduces the number of times the image memory is accessed, further shortening the drawing time. be able to.

On the other hand, in S204, the drawing point number determining variable D
If is non-negative, the drawing point number determination variable/drawing point number control unit 4
7 outputs the value n as the number of drawing points, and the drawing point number correction unit 48
calculates and outputs the value n・h, and the horizontal line drawing unit 51 draws a horizontal line from the coordinates (x, y) to the coordinates (x+n・h−1, y) (S208), and then stores the value in the register 49. The stored value is increased by n (S209). Also,
The drawing point number determining variable/drawing point number control unit 47 outputs a switching control signal to the addition value selector 46 to select the adder 44, and the contents of the drawing point number determining variable register 43 are n.Δ
The value is updated to a value increased by y-Δx (S210).

After that, the horizontal line drawing section 51 registers the register 50.
The value stored in (y-coordinate of the next horizontal line to be drawn)
is increased by 1 (S211). In addition, the control unit 62 decreases the value of the variable loop stored in the register 61 by 1 (S212), and determines whether loop=0, that is, whether horizontal lines at all y coordinates have been drawn (S213). ), the steps from S204 onward are repeated until the result is YES.

FIG. 3 shows an example of a straight line actually drawn by the above operation. As shown in the figure, the starting point coordinates (0, 0
) to the end point coordinates (19, 5), the number of drawing points in the y-coordinate direction is 5+1=6, so 6
The horizontal line of the book will be drawn. Also, the number of drawing points in the x-coordinate direction is 19+1=20, and 20/6=3 with a remainder of 2, so there are 4 horizontal lines with 3 drawing points and 4 drawing points.
If two horizontal lines are drawn, a straight line as shown in the figure will be drawn.

That is, by the above operation, the value of the drawing point number determining variable D changes to take a negative value and a non-negative value at a predetermined period and frequency, and three values are changed depending on whether it is negative or non-negative. Alternatively, by drawing four horizontal lines, a straight line connecting the starting point coordinates (0,0) to the ending point coordinates (19,5) is drawn. Further, if a value of 2 or more is set as the value h indicating the width of the straight line to be drawn, the number of drawing points correction unit 48
By multiplying the number of drawing points of the horizontal line by h, vertically adjacent horizontal lines partially overlap, so a straight line with a predetermined width is drawn. In addition, the initial value correction unit 32
The initial value set in the register 49 is the value x1-(h-1)
- By correcting to n/2, the horizontal line is offset in the x-axis direction, so that the starting point coordinates and the ending point coordinates are located at the center line of the linear locus with width. In addition,
If the number of drawing points is multiplied by h, some parts will protrude from the starting point and the ending point, but a drawing suppressing means may be provided to prevent these protruding parts from being drawn. Also, instead of multiplying the number of drawing points by h, for example,

[0032]

[Math 1]

If this is done, the width of the straight line can be made almost constant regardless of the gradient of the straight line, but it is preferable to approximate it by h times from the viewpoint of drawing speed. As mentioned above,
Instead of calculating the x and y coordinates in x coordinate units each time, it calculates only the coordinate points where the x and y coordinates change simultaneously in y coordinate units, and draws the distance horizontal line to the next changing point at once. , high-speed straight line drawing is performed.

Furthermore, by multiplying the number of drawing points by a predetermined value,
It is also easy to draw straight lines of any width. In addition,
In the above embodiment, an example was shown in which x1<x2, y1<y2, and the slope of the straight line is between 0 and 1. By reversing the relationship between the coordinates and the y-coordinate, it is possible to draw straight lines with any inclination.

Furthermore, although an example has been shown in which the number of drawing points is determined to be n or n+1 by evaluating the value of the drawing point number determining variable D, the present invention is not limited to this. In addition, the number of drawing points may be switched to n or n+1 a predetermined number of times depending on the quotient n and the remainder of the integer division Δx/Δy. In this case, there is no need to perform processes such as addition and determination each time each horizontal line is drawn, so that drawing can be performed even faster.

Furthermore, in the above embodiment, an example was shown in which the number of drawing points of all horizontal lines from the starting point to the ending point is n or n+1, but in this case, it is not necessary to connect the starting point and the ending point geometrically. The point closest to the virtual line may not be drawn. Even in that case, points that are significantly shifted will not be drawn, so it is fully applicable to ordinary graphics display systems.

However, in order to make the horizontal line follow a more geometrical virtual straight line, for example, the number of drawing points of the horizontal line including the starting point or the ending point may be set as follows. That is, if the integer division Δx/Δy is divisible and the quotient n is an even number, the number of drawing points of the horizontal line including the starting point or the ending point is set to n/2 or n/2+1, respectively, and the coordinates (x1+n/2, y1+1) to coordinates (
x2-n/2-1, y2-1), or coordinates (x1+n
/2+1, y1+1) to the coordinates (x2-n/2, y2-
While drawing up to the drawing point in 1) as above, if the integer division Δx/Δy is not divisible or the quotient n is an odd number, the number of drawing points of the horizontal line including the start point or the end point is both n/2 + 1. and the coordinates between them (x1+n/2
+1, y1+1) to coordinates (x2-n/2-1, y2-
The configuration may be such that up to the drawing point 1) is drawn as described above.

[0038]

[Effects of the Invention] As explained above, according to the present invention,
A predetermined number of drawing points in the direction of the other coordinate axis for each coordinate value between the start point and the end point in the coordinate axis with the smaller number of drawing points in the direction of the coordinate axis between the start point and the end point of the first coordinate axis and the second coordinate axis. By providing partial straight line drawing means in the coordinate axis direction that draws a partial straight line consisting of This has the effect that it can be significantly shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a straight line drawing device.

FIG. 2 is a flowchart showing operations performed by the linear drawing device.

FIG. 3 is an explanatory diagram showing an example of drawn straight lines.

FIG. 4 is a flowchart showing a conventional algorithm for drawing straight lines.

FIG. 5 is a block diagram showing the configuration of a straight line drawing device to which the same algorithm is applied.

[Explanation of symbols]

31 Initial value calculation section 32 Initial value correction section 40 Drawing section 41, 42, 49, 50, 61 Register 43
Number of drawing points determining variable registers 44 and 45 Adder 46 Addition value selector 47 Number of drawing points determining variable/number of drawing points control unit 48
Drawing point number correction section 51 Horizontal line drawing section 62 Control section

Claims (7)

[Claims] Claim 1: In a straight line drawing device that draws a straight line connecting a starting point and an ending point, the starting point and A straight line drawing device comprising a partial straight line drawing means in a coordinate axis direction for drawing a partial straight line consisting of a predetermined number of drawing points in the other coordinate axis direction for each coordinate value between end points. 2. The straight line drawing device according to claim 1, further comprising: reducing the number of drawing points included in the partial straight line from the larger number of drawing points in each coordinate axis direction between the starting point and the end point to the smaller number of drawing points. a first number equal to a quotient obtained by dividing an integer by the number of drawing points, or a second number that is one more than the quotient, and a partial straight line consisting of the first number of drawing points; partial straight line drawing control means for controlling the ratio of the number of times of drawing and the number of times of drawing a partial straight line consisting of a second number of drawing points to be approximately equal to the ratio of the dividend to the remainder in the integer division; A straight line drawing device characterized by: 3. The linear drawing device according to claim 2, further comprising: an initial number of drawing points approximately 1/1 of the first number;
1. A straight line drawing device comprising an initial drawing point number setting means for setting the number of points. 4. The straight line drawing device according to claim 2, further comprising a partial straight line in the direction of the coordinate axis between the start point and the end point, which has a larger number of drawing points in the direction of the coordinate axis between the start point and the end point. The distance in the direction of the other coordinate axis from the connecting virtual straight line is
A straight line drawing device comprising initial partial straight line drawing means for drawing a partial straight line consisting of drawing points whose distance is smaller than 1/2 of the distance between adjacent drawing points. 5. In place of the drawing point number setting means in the straight line drawing device of claim 2, the number of drawing points included in the partial straight line is set to a first number equal to a predetermined multiple of the quotient of the integer division, or the second of a predetermined multiple of a number that is one more than the quotient;
A straight line drawing device comprising a drawing point number setting means for setting the number of drawing points to the number of drawing points. [Claim 6] A starting point whose coordinates are (x1, y1);
In a line drawing device that draws a straight line connecting an end point whose coordinates are (x2, y2), the value Δx=x2-x1+1 and the value Δy=y2-y1+
Based on 1, the quotient n of integer division Δx/Δy, the value n・Δy
−Δx, and an initial value calculating means for calculating the value (n+1)・Δy−Δx, and a first value calculating means for calculating the value n・Δy−Δx
a second register that stores the value (n+1)・Δy−Δx, and a second register that stores the value (n+1)・Δy−Δx as an initial value.
A third register that stores Δy−Δx, a fourth register that stores the starting point coordinate values x1 and y1 as initial values, and a fifth register, and a sixth register that stores the value Δy. , a first adder and a second adder that add the contents of a third register to the contents of the first register and the second register, respectively, and the first adder, or One of the addition results of the second adder is selectively switched to the third adder.
a selector that outputs and stores the value in the third register; outputs a switching control signal to the selector based on the sign of the value stored in the third register; Switching to output the number of drawing points
a drawing point number control means, the number of drawing points output from the switching/drawing point number control means, the contents of the fourth register,
and a straight line in the x-axis direction based on the contents of the fourth register and the fifth register.
x-axis direction straight line drawing means for updating the contents of the registers to a value obtained by adding 1 to the addition result and the contents of the fifth register, respectively; and subtracting the contents of the sixth register by 1, and A straight line drawing apparatus, comprising: a control means for repeatedly performing the operations of the respective parts until 0 becomes zero. 7. In addition to the straight line drawing device according to claim 6, a value x1-(h-1).multidot. n
/2 and stores the calculation result in the fourth register as a corrected initial value; and the number of drawing points output from the switching/drawing point number control means and the value h.
A straight line drawing device comprising: a drawing point number correcting means for multiplying by the number of drawing points and outputting the product as a corrected drawing point number to the x-axis direction straight line drawing means.