JPH0664443B2 - Vector drawing method - Google Patents

Description

The present invention relates to a vector drawing method in computer graphics or the like.

[Conventional technology]

FIG. 6 is an explanatory diagram showing a known conventional vector drawing method, and specifically expresses the Bresenham line segment generation algorithm. In the figure, 21 is coordinate x, 22 is coordinate x + 1, 23 is coordinate x + 2, 24 is coordinate y,
25 is the coordinate y + 1, 26 is the coordinate y + 2, 27 is the true line segment to be drawn, 28 is the reference pixel whose coordinate is (x, y), 29 is the pixel 28 and the true line segment 27 Error, 30 is pixel at coordinates (x + 1, y), 31 is coordinates (x + 1, y + 1)
, 32 is the inclination of the line segment, and here, assuming that the true line segment 27 is from coordinates (x ₁ , y ₁ ) to (x ₂ , y ₂ ), the value α is α = (y ₂ −y ₁₎ it will become _{/ (x} 2 -x _1).
Further, 33 is a new error between the pixel 30 and the true line segment 27, and 34 is a new error between the pixel 31 and the true line segment 27.

Next, the operation will be described. Some reference coordinates (x,
Assuming that the value of the error 29 between the pixel 28 of y) and the true line segment 27 is e ₀ , the x coordinate is incremented by 1, so that the error 29 has a value of the gradient 32 of the line segment α = (y ₂ − _{y 1) / (x 2 -x} 1)
Increase by minutes. Therefore, the next pixel may be determined by the new error.

If the pixel 30 with coordinates (x + 1, y) is selected as the next pixel, the new error value e _{1 of the} error 33 becomes the error for selecting that pixel, and the pixel 31 with coordinates (x + 1, y + 1) is selected. Then the new error 34 value (e ₁ −
1) is the error when selecting that pixel. Therefore, in the case of FIG. 5, the pixel 31 at the coordinate (x + 1, y + 1) with a small error is selected. Hereinafter, a vector is drawn by continuously performing this process.

[Problems to be solved by the invention]

Since the conventional vector drawing method is configured as described above, there is a problem that an arithmetic operation is required every time each of the pixels 30 and 31 is selected, and the processing takes time.

The present invention has been made to solve the above problems, and an object thereof is to obtain a vector drawing method capable of drawing a short vector within a certain range at high speed.

[Means for solving problems]

The vector drawing method according to the present invention uses the bit "1" to increase the x-direction and y-direction components, the bit "0" to increase only one of the directional components, or the bit "0" to increase the x-direction and y-direction components. , A relative change bit of 1 bit unit that indicates an increase in only one direction component by bit “1”, and the relative position of each pixel is defined by 1 bit unit for each vector within a predetermined range. The pixel relative position determination information described in 1. is prepared in advance in the pixel position determination table, and each pixel position of the vector is determined according to the relative change bit of the corresponding pixel relative position determination information. .

[Work]

In the vector drawing method according to the present invention, when drawing a vector, if the vector is within a predetermined range, the pixel relative position determination information of the corresponding pixel position determination table is referred to, and the pixel is changed according to the relative change bit. Vectors are drawn fast by arranging pixels without computing the positions individually.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 1 is coordinate x, 2 is coordinate x + 1, 3 is coordinate x
+31, 4 is coordinate y, 5 is coordinate y + 1, 6 is coordinate y + 31,
7 is a true line segment to be drawn, 8 is the start point of the vector having coordinates (x, y), 9 is the end point of the vector having coordinates (x + n, y + m), and 10 is the determined pixel.

FIG. 2 is an explanatory diagram showing an example of a pixel position determination table. 11 is this pixel position determination table, 12 is the starting point coordinates (x, y), and the ending point coordinates are (x + 1, y), ( x
+ 2, y) ... (x + 31), (x + 1, y + 1), (x + 2, y)
+1) …… (x + 31, y + 1) …… (x + n, y + m) ……
It is the pixel relative position determination information of each vector which is (x + 31, y + 31). As described above, in this pixel position determination table 11, all pixel relative position determination information 12 regarding vectors whose vector inclination α is in the range of 0 ≦ α ≦ 45 ° and 32 dots or less are stored in the above-mentioned order, for example. Therefore, they are arranged neatly. Further, FIG. 3 is an explanatory view showing the details of the pixel relative position determination information 12, 13 is a relative change bit in units of one bit, and this relative change bit 13 is
One pixel relative position determination information 12 is formed by 32 bits. This relative change bit is "1" indicating that both the x direction and the y direction change from the previous pixel, and "0" indicates that it changes only in the x direction and not in the y direction. The bit pattern corresponds to the starting point of the corresponding vector.

Therefore, the data amount of the pixel relative position determination information 12 stored in the pixel position determination table 11 is equal to the number of end points, and 32 + 31 + 30 + ... + 1-1 = {32 × (32 + 1) / 2} −1 = 527. Yes, the table size is 527 x (32/8) = 2108 (bytes).

Next, the operation will be described. The coordinates of the starting point 8 are (x, y),
An example of drawing a vector (here, n ≧ m, n ≦ 31, m ≦ 31) in which the coordinates of the end point 9 is (x + n, y + m) will be described according to the flow chart of FIG. First, the length of the vector is obtained in step ST1. Here, n ≦ 31, m
From the condition of ≤31, it is found that this vector is a short vector within 32 dots. Therefore, the determination process at the next step ST2 is negative (FAULT), and the process proceeds to step ST3. Here, if the result of the determination processing in step ST2 is true (TRUE), a straight line is drawn by the conventional Bresenham algorithm.

Next, in step ST3, the method will be described below in the process of obtaining the location (offset) of the pixel relative position determination information 12 corresponding to this vector. The total number of data stored in the pixel position determination table 11 is 527 as described above, and the table size is 2108 (bytes). Next, when the offset of the table corresponding to the start point (x, y) 8 and the end point (x + n, y + m) 9 is obtained, Becomes

Here, FIG. 5 shows that at a general angle of 0 ° to 360 °,
The pointer for selecting the pixel 10 is shown in units of 45 °. At step ST4, the area to which the vector corresponds is determined according to FIG. 5, and only the range of 0 ° to 45 ° is specified. The pixel selection method is determined in order to apply the data of the pixel position determination table to all angles. In this example, the vector inclination α is 0 ≦ α ≦
Since it is 45 °, it can be seen that, with respect to the reference pixel 8 having the coordinates (x, y), the coordinates of the pixel selected next are either (x + 1, y) or (x + 1, y + 1).

Next, in step ST5, the pixel position determination information 12 is shifted right one bit from the offset obtained in step ST3, and if "1" is set in the relative change bit 13, the pixel (x +
1, y + 1) is selected, and if the relative change bit 13 is "0", pixel (x + 1, y) is selected. Thereafter, this operation is repeated n times to set the coordinates of each pixel 10 on the bit map memory. In the graphic display, a vector is drawn on the basis of the data set on the bit map memory.

In the above embodiment, the pixel relative position determining information has a 4-byte 32-bit structure and the vector length is limited to 32 bits. However, it may be increased or decreased according to the memory size. It has the same effect as the example.

[Effects of the Invention] As described above, according to the present invention, a vector within a predetermined range is referred to by the pixel relative position determination information prepared in the pixel position determination table, and according to its relative change bit. Since the pixels are arranged and drawn, it is not necessary to individually perform arithmetic operations for deciding the pixel positions, and it is possible to draw a complicated vector diagram at high speed. In the pixel relative position determination information, bit “1” increases the x-direction and y-direction components, and bit “0”
For increasing only one direction component, or for bit "0" for increasing x direction component, y direction component, and for bit "1" indicating increase in only one direction component Since it is formed by the above, the data capacity is small, the number of times of memory access of the table is small, and in combination with the above point, the drawing speed can be further increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a vector drawing system according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the configuration of a pixel position determination table, and FIG. 3 is an explanation showing the configuration of pixel relative position determination information. FIGS. 4 and 5 are flow charts showing the operation, FIG. 5 is an explanatory view showing a pixel selection guide in 45 ° units, and FIG. 6 is an explanatory view showing a conventional vector drawing system. 10 is a pixel, 11 is a pixel position determination table, 12 is pixel relative position determination information, and 13 is a relative change bit.

Claims (1)

[Claims] 1. In a vector drawing method for drawing a vector on a graphic display, in the pixel position determination table, a bit "1" is used to increase an x-direction component and a y-direction component, and a bit "0" is added to one direction component. Or a predetermined change is formed by a plurality of 1-bit relative change bits indicating an increase in the x-direction component and the y-direction component at bit "0" and an increase in only one direction component at bit "1". For each vector within the range, pixel relative position determination information describing the relative position of each pixel of the vector in 1-bit units is stored, and when drawing the vector within the predetermined range, the pixel position The position of each pixel is determined according to the corresponding pixel relative position determination information read from the determination table, and the vector is converted into the graph. Vector drawing method, characterized in that drawing on the click display.