JPS6242273A - Drawing control system by xor mode - Google Patents

Abstract

PURPOSE:To attain a picture processing method which has no omitted joining point of vectors at a necessary part when a closed pattern is drawn, by controlling the drawing of a start point at the joining point according to the tilt of two adjacent vectors. CONSTITUTION:The Y coordinates Y0 and Y1 of the start and end points of a vector are loaded on register 1 and 2 respectively. A comparator 3 compares both coordinates Y0 and Y1 with each other. Then coordinate tilt information Y0>Y1, Y0<Y1 or Y0=Y1 is delivered to a register 4. A decoder 6 reads out the tilt information from a register 4 and 5 and the tilt information of the register 4 is held by the register 5. Thus the register 5 always holds the preceding tilt information, i.e., the tilt information on the preceding vector. The decoder 6 knows vector changes from the tilt of the present vector given from the register 4 and the tilt of the preceding vector given from the register 5 for drawing control of a start point. Thus the drawing processing is possible with no omission of the vector at a desired position and the joining point of vectors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drawing control method using the XOR mode when drawing a closed figure to be filled in using the XOR mode.

[Technical Background of the Invention] In recent years, graphics processing systems using computers have been widely used. In these systems, the operation of filling inside a closed figure is frequently used, and this processing has traditionally been performed pixel by pixel using a microprocessor. However, since this method requires a large amount of processing time, it has recently been considered to perform this processing using hardware.

By the way, in the closed figure shown in FIG. 4, the closed figure always has a pair of line-symmetric points, as indicated by the symbols A and .

Therefore, it is possible to detect whether the figure is a closed figure based on whether or not the pair of points are present, and by using this method, it is possible to cause the hardware to perform the filling process of the closed figure.

[Problems with the background art] However, when the closed figure in Figure 4 is drawn in XOR (exclusive OR) mode, the connection point between the line segment (vector) and the line segment (vector) is as shown in Figure 4. The force field has a disadvantage in that it can be handled as shown in Fig. 3, and it interferes with the closed figure detection process described above.

[Object of the Invention] In view of the above-mentioned drawbacks, the object of the present invention is to provide a drawing method using an XOR mode that allows drawing processing to be performed without leaving vectors of necessary parts and connection points of the vectors when drawing a closed figure. The purpose is to provide a control method.

[Summary of the Invention] The present invention achieves the above object by controlling whether or not to draw the starting point of the connection point of two adjacent vectors based on the slope of two adjacent vectors when drawing a closed figure in the XOR mode. The goal is to achieve the following.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of a drawing control device to which the drawing control method using the XOR mode of the present invention is applied.

Register 1 is the Y location w of the starting point of one line segment (vector)
yo is stored, and register 2 stores the Y coordinate Y1 of the end point of the vector. Comparator 3 receives YO from registers 1 and 2.

Yl is input, the two are compared, and the slope of the vector, which is the result of the comparison, is output to the register 4.

Register 4 stores the slope of the current vector, and register 5 stores the slope of the previous vector. The decoder 6 determines whether or not to draw the start point of the current vector based on the slope of the current vector and the slope of the previous vector, and outputs a write signal 100 if the start point of the current vector is to be drawn.

Next, the operation of this embodiment will be explained. First, when drawing a closed figure in the XOR brane, the closed figure is composed of several vectors as shown in FIG. The Y-axis slopes of these vectors are positive, negative, and O (no slope).
It can be said that a closed figure is composed of a combination of these three.

That is, in Figure 2, a indicates a positive slope, b indicates a negative slope, and C indicates O (no slope). Table 1 shows whether or not the starting point of the vector is drawn based on the combination of these three. It is determined as shown in .

Table 1 The left column of Table 1 shows changes in the vector, and the right column shows whether or not to draw the starting point of the current vector when there is a vector change shown in the left column. . In this case, when the start point of the current vector is drawn, the connection point between the current vector and the previous vector is omitted, and when the start point is not drawn, the connection point between the two vectors is drawn without being combined.

Registers 1 and 2 in FIG. 1 are loaded with the Y coordinate YO9 of the starting point of the vector and the Y coordinate Y1 of the ending point by a microprocessor (not shown). The comparator 3 compares both Y coordinates and obtains tilt information YO>Yl or YO<Yl or YO=
Y1 is output to register 4. Note that when YO>Yl, the slope of the vector is 0, when YO<Yl, the slope of the vector is -, and when YO=Y1, the slope of the vector is O.

The decoder 6 reads the slope information from the register 4 and the register 5, and at this time, the slope information of the register 4 is held in the register 5. Therefore, the register 5 always holds the previous slope information, that is, the slope information of the previous vector.

The decoder 6 calculates the change in the vector from the slope of the current vector from the register 4 and the slope of the previous vector from the register 5, determines whether or not to draw the starting point of the current vector based on Table 1, and draws the starting point of the current vector. If so, a write signal 100 is output.

FIG. 3 shows an example of drawing in which whether or not to draw connection points between vectors is controlled by the apparatus shown in FIG. 1. Figure 3 (A> does not draw a start point because the vector changes from 10 to 10, so a point remains at the connection point. In (B), a start point is drawn because the vector changes from + to -. , connection points can be handled.The same applies hereafter, but Figure 3 (F) is a special example, and unlike Table 1, because horizontal lines are not originally drawn when drawing the figure). Although the connection points are behind, there is no problem because such cases are not actually drawn.

According to this embodiment, for example, the connecting point of a vector whose slope changes from a curve to - is drawn without being missed, so that the problem shown in C of FIG. 4 does not occur.

Even when drawn in the XOR mode, a closed figure always has a pair of symmetrical points, and the closed figure can be recognized by hardware. Therefore, it becomes possible to fill in a closed figure at high speed using hardware.

E. Effects of the Invention] As described above, according to the drawing control method using the XOR mode of the present invention, when drawing a closed figure in the XOR mode, it is possible to determine whether or not to draw the starting point of a connecting point based on the slope of two adjacent vectors. By controlling this, it is possible to perform drawing processing that cannot handle the vectors of the necessary parts and the connection points of the vectors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a drawing control method to which the XOR mode drawing control method of the present invention is applied, and FIG. 2 is a diagram showing an example of a closed figure drawn by the apparatus shown in FIG.
FIG. 3 is a diagram showing an example of a vector drawn by the apparatus shown in FIG. 1, and FIG. 4 is a diagram showing an example of a conventional closed figure drawn in the XOR mode. 1.2, 4.5...Register 3...Comparator 6...Decoder agent Patent attorney Book 1) Search Figure 4 (F) OO No. 3 o,! , fJ<8ri'yo・1 ・Menya (Hero figure

Claims (1)

[Claims] Y-coordinate holding means for holding the Y-coordinates of the starting point and ending point of a vector; vector inclination detecting means for detecting the inclination of the vector by comparing the Y-coordinates of the starting point and the ending point; A slope holding means that holds the current vector and the previous vector separately, and a start point drawing determining means that determines whether or not to draw a starting point at the connection point of both vectors in response to the change in the slope of the current vector and the previous vector. The XOR is characterized in that, depending on the change state of the slopes of the two vectors, control is performed so as not to draw the start points of the two vectors in the XOR mode.
Drawing control method based on mode.