JPS63221493A - Straight line drawing system for bit map - Google Patents

Abstract

PURPOSE:To easily draw a straight line by providing plural tables to display the number of dots drawn once in an X direction when plural straight lines of a special length respectively have the inclination within 45 deg. with an A axis. CONSTITUTION:A table 100 to display the number of the continuous drawing dots in the X direction when the straight line of a line length (a) has the inclination of 0-45 deg., the same table 10, to the straight line of a line length (a+b), a table 102 to the straight line of a line length (a+2b) and a table 10n to a line length (a+nb) are equipped beforehand. A processor 1 designates an inclination theta with a length (l) and the X direction to a selecting means 20. The means 20 selects the table 10n of the line length closest to the length (l) and obtains the number of dots corresponding to an angle theta out of it. Next, only the number of the dots is drawn from a starting point in the X direction. Thus, the straight line can be easily drawn.

Description

[Detailed Description of the Invention] [Summary] When drawing a straight line in a bitmap memory, a straight line length a and a straight line length are defined, and the lengths are a, a+b, a+2b,
Multiple tables are provided that display the number of dots to be drawn at one time in the X direction when each straight line of a+nb has an inclination of 0 to 45'' with the X axis, and corresponds to the length closest to the straight line length to be drawn. Select the table to be drawn, find the number of dots corresponding to the specified angle in the selected table, and draw a straight line.

[Industrial application field]

The present invention relates to an improvement of the linear drawing method in a display or print output system having a bitmap type memory.

[Conventional technology]

A graph ink display device such as a CRT uses a bitmap type memory having storage locations corresponding to pixel locations.

Conventionally, when a straight line is drawn in a bitmap memory and displayed as a display output, the position of the line to be drawn is determined by the slope and length of the line to be drawn.

FIG. 4 is an explanatory diagram of a conventional straight line drawing method.

In the figure, the O mark indicates the bitmap memory to be turned on, and each digit corresponds to a storage position in the memory.

As shown in Figure 4 (al), on the bitmap memory,
To draw a straight line with a slope of 45 degrees to the axis, move one dot from the starting point in the X direction, then move one dot in the Y direction, turn on the bitmap memory, and repeat this operation. .

Figure 4 (Drawing 4 dots at once in the X direction as shown in bl)
If you turn on 4 dots), move 1 dot in the Y direction, and then draw 4 dots at once in the X direction, you can draw a straight line with less slope.

FIG. 4(C) shows the relationship between the angle of the straight line and the number of dots drawn at one time in the X direction, when the length of the straight line to be drawn is L (expressed in the number of dots).

That is, if you draw a dot in the X direction once, you will get a straight line of length L that is parallel to the If you draw one dot at a time in the X direction, you will get a straight line with a length that makes an angle of 45 degrees with the X direction.

In this way, the dot position to be drawn is determined by the slope of the drawn straight line and its length, but in the conventional method, Bre
Sen Ham's straight line generation algorithm was used, and this algorithm was implemented using software or dedicated hardware.

FIG. 5 is an explanatory diagram of Bresen ham's straight line generation algorithm.

The straight line L' is the line you want to draw, and the points XI and x2 are the same x=
It is located on the axis of a and is the center of mutually adjacent bitmap memories with a straight line L° in between.

Let U be the intersection of the line connecting points X and X2 and straight line L, compare the distance between point xl and point U with the distance between point X2 and point U, and store the bitmap memory of the closer point. Turn on.

Therefore, in the example of FIG. 5, the bitmap memory centered at point X1 is turned on.

[Problem that the invention seeks to solve]

However, this software method using Bresen Hate's straight line generation algorithm has problems in that it takes a long processing time and that the use of dedicated hardware is expensive.

[Means for solving problems]

As shown in the principle diagram in Figure 1, the above problem occurs in the straight line drawing method in which data is written to display and output a straight line in a bitmap memory that has a storage position corresponding to the position of the pixel to be displayed and output. A straight line length a and a second straight line length are defined respectively, and a straight line having the first straight line length a, a straight line having the sum of the first straight line length a and the second straight line length, and a first straight line length a. A plurality of tables 100 to 100 displaying the number of dots to be drawn at one time in the X direction when a straight line having a length that is multiple times the sum of the lengths of the second straight line has an inclination within 45 degrees from the X axis. 107, and means 20 for selecting the table 100-107 corresponding to the length closest to the straight line length to be drawn from among the plurality of tables 10o-107.

[Effect]

According to the present invention, a straight line having a predefined straight line length a, a straight line having a straight line length a+b, and a straight line having a straight line length a+nb are connected to the X axis by 45
If the line has an inclination within 100 degrees, a plurality of tables 100 to 101 displaying the number of dots to be drawn at one time in the X direction are provided, and the line corresponds to the line length that is closest to the line length specified by the selection means 20. Tables 100 to 10I are selected. Next selected tables 100-10. ．． Find the number of dots corresponding to the specified angle.

〔Example〕

FIG. 2(a) is a diagram showing an embodiment of a bitmap linear drawing method according to the present invention.

FIG. 2(b) is a diagram showing a straight line drawing table of the present invention.

FIG. 3 is a flow chart of the present invention.

In the figure, 1 is a processor, 2 is a bitmap memory, 10
1.10□ and 10n are each a table, 2o is a selection means,
30 is a graphic display.

In the present invention, the first shortest line length a and the variable length line length are defined as straight lines parallel to the X-axis or Y-axis, and as shown in FIG. 2(b), A straight line with line length a is O~45
A table 100 showing the number of consecutively drawn dots in the X direction or Y direction when the line has an inclination of 6, and a table 101 when a straight line with line length a+b has an inclination of θ to 45°.
, table 102 when a straight line with line length a+2b has an inclination of θ~45°, and a straight line with line length a+nb has an inclination of θ~45°.
A table 10n having an inclination of 45'' is prepared and placed in advance.

Note that n is any integer, and if the inclination of the line is 45 to 90 degrees, the X direction and Y direction may be interchanged.

When the selection means 20 operates as a program operation means, when drawing a straight line on the bitmap memory 2 with a length l and an inclination of θ with respect to the and the angle θ. For example, if the starting point, coordinates, position, and end point coordinate position are input using a keyboard or a light pen, the length and angle are automatically calculated and then specified.

The selection means 20 first selects a table 1 of line lengths closest to the length l.
0.1 is selected, and then the number of dots corresponding to the angle θ is determined from the selected table 10n.

Processor 1 uses this number of dots to draw a straight line according to the flowchart of FIG.

In this case, when nothing is drawn in the bitmap memory 2, logic "0" is stored.

■Table of line lengths closest to the line length l to be drawn first 10. Select.

(2) Find the number of dots corresponding to the specified angle θ in table 10-.

■Draw this number of dots in the X direction from the starting point.

That is, specific logical data "1" is written.

- Check whether drawing of the entire line length has been completed. If not, proceed to (2); if it has been completed, finish.

■Add 1 to the Y-direction address (number of dots) and return to ■.

The straight line created in this manner is displayed on the graph ink display 30 by, for example, reading and supplying the addresses of the bitmap memory 2 by continuously scanning them.

[Effects of the Invention] As described above in detail, the present invention has the great effect that a straight line can be easily drawn by selecting a table.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention. FIG. 2 (al is a diagram showing an embodiment of a bitmap straight line drawing method according to the present invention. FIG. 2 (bl is a diagram showing a straight line drawing table of the present invention). FIG. This is a flowchart. Fig. 4 is an explanatory diagram of a conventional straight line drawing method. Fig. 5 is an explanatory diagram of Bresen ham's straight line generation algorithm. In the figure, 1 is a processor, 2 is a focus map memory, and 10
1, IQ, , 1 (1 and 1 are respectively tables, 20 is a selection means 1, and 30 is a graphic display.

Claims (1)

[Claims] In a straight line drawing method in which data is written to display and output a straight line in a bitmap memory having a storage position corresponding to the position of a pixel to be displayed and output, a first straight line length (a) and a first straight line length (a) 2
A straight line having a first straight line length (a), a straight line having a length equal to the sum of the first straight line length (a) and the second straight line length (b), each having a straight line length (b) defined; If a straight line with a length that is multiple times the length of one straight line (a) and the second straight line length (b) has an inclination within 45 degrees with respect to the X axis, it is drawn at once in the X direction. A plurality of tables (10_0 to 10_n) displaying the number of dots, and a table (10_0 to 10_n) corresponding to the length closest to the straight line length to be drawn from among the plurality of tables (10_0 to 10_n).
10_n).