JPH0318195B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for finding a part of a figure indicated by a cursor in a device equipped with a CRT and displaying figures on the screen. To explain in more detail, in the above-described apparatus, a figure is usually composed of a plurality of pixels.
Furthermore, in order to operate the device, there are cases where it is desired to select a specific pixel within this figure using a cursor. The present invention relates to a method for finding the pixel closest to the cursor position. The present invention mainly consists of
Since the present invention is often used in CAD (Computer Aided Design) devices, the present invention will be explained using a CAD device as an example. In CAD equipment, CRT
Various designs are performed while interacting with a computer while displaying figures on the screen. When performing such design operations, you may want to point a cursor at a part of a figure displayed on a CRT and specifically display or recognize that part. In order to recognize the part of the figure pointed to by the cursor and specially display this part, it is necessary to calculate the distance between the cursor and each pixel and select the pixel with the closest distance. The following methods (a) and (b) are known as methods for finding the pixel closest to this cursor.

(b) A method of calculating the distance from the cursor for all pixels of a figure and detecting the desired pixel as a result.

According to this method, distance calculations must be performed for all pixels. Typically, CAD
Since the number of pixels displayed on the device is large, method (a) requires a huge amount of calculation. As a result, there is a drawback that it takes a long time to extract the pixel closest to the cursor.

(b) A method in which the CRT screen is divided into N equal parts in the X and Y directions into several blocks, and the distance from the cursor is calculated only for pixels within the block where the cursor exists.

Although this method reduces the amount of calculations compared to method (a) above, it still requires a large amount of calculations.
It takes a long time to extract a given pixel. Depending on the position of the cursor, at worst four blocks may have to be searched. Also, where a pixel belongs changes depending on the state of the screen (enlargement, reduction, parallel movement), so
There is also the drawback that the BIT indicating which block exists must be updated for each RERAINT operation.

The present invention has been made in view of the points explained above. To summarize the present invention, the first step is to search for the presence or absence of maximum or minimum coordinate data in an area that moves as the cursor moves, and to detect the maximum or minimum coordinate data in this search. Then, at that point, a second step of shrinking to a new area touching the pixel corresponding to the detected maximum or minimum coordinate data with the cursor as the center is performed, and the first and second steps are repeated to expand the area. A third step of successively reducing the size up to a preset size and recognizing the pixels remaining in the smallest area as the pixels closest to the cursor position.

The operation of the present invention will be explained in detail below using the drawings. FIG. 1 shows an example of a display on a CRT screen of a CAD device. In the figure, numeral 1 is a cursor that can be set at any position on the CRT by the person operating the CAD device using a joy stick or the like. _A1 to _A6 are pixels.
In FIG. 1, each pixel is expressed as an independent figure (circle or triangle), but it may be divided into finer levels (line segments). For example, pixel _A5 may be divided into four straight lines. However, in the field of CAD devices that create electrical circuit diagrams, etc., each pixel is often a figure representing a transistor, IC, diode, etc., rather than a single straight line.

For example, if you select pixel A ₂ on such a CRT screen and try to modify it, first
A ₂ needs to be recognized by the computer. To do this, cursor 1 is moved to pixel A ₂ , but cursor 1 must be moved to pixel A ₂
Superimposing it on the line is a nerve-wracking operation. Therefore, as described above, the computer searches for the pixel closest to the cursor, and the pixel obtained as a result of the search is selected. The present invention was developed because the conventional search method has drawbacks.

All pixels are given names based on input from the CAD device operator, and this information is managed as a two-dimensional database. Also, each pixel has a maximum and minimum (MIN-MAX) value in the definition space. Add explanation. Assume that each pixel is arranged on the XY plane. Each pixel is
Since it occupies a certain area on a plane, there are maximum and minimum values on the x-coordinate and maximum and minimum values on the y-coordinate of this occupied area. When inputting each pixel to a CAD device, a computer calculates its maximum and minimum coordinate values, and each pixel is managed as a database along with its name information. The concept of this database is shown in Figure 3. For example, in Figure 1, the maximum and minimum values of pixel A ₆ are
They are Xn, Yn and Xm, Ym. Therefore, if the name of this pixel is _A6 , the maximum and minimum coordinate values are stored as shown in Figure 3.

Based on the CRT display and database status as described above, the display graphic detection method of the present invention operates as follows.

The operation when selecting, for example, pixel _A2 in FIG. 1 will be explained. First, move the cursor to the vicinity of pixel _A2 using a joystick or the like.
The operation up to this point is the same as the conventional one. However, the search operation described below is different from the conventional one.

In the present invention, an area is set that moves as the cursor moves. This area is, for example, as shown in _B1 to _B3 in FIG. That is, the largest area is a rectangular area based on the + mark of the cursor. Here, FIG. 2 is an enlarged view of the vicinity of the cursor in FIG. 1.

First, the computer searches within the largest area _B1 at the position where the cursor has been moved. What to search for is the third
This is whether or not the maximum and minimum coordinate values of each pixel in the database shown in the figure are included in the area _B1 .

The computer sequentially scans the database and, when it detects the maximum or minimum coordinate value belonging to this area _B1 , changes the area to be searched at that point. How to change it is to reduce the size of the area to a size that is centered on the origin 0 of the cursor and touches the pixel corresponding to the detected maximum or minimum coordinate data.

To explain specifically using FIG. 2, it is assumed that a database is searched and the maximum value of pixel _A1 is detected. At that point, the search area is reduced to area _B2 adjacent to pixel _A1 , as shown in FIG.

The computer then searches again within this reduced area. As a result, the computer detects the minimum value of pixel _A2 , so the search area becomes _B3 , which is even smaller.

Next, the computer searches within this area _B3 , but as a result, the other maximum and minimum coordinates can no longer be detected, so this pixel _A2 is recognized as the pixel to be sought. An explanation will be added regarding the fact that this pixel _A2 is the pixel closest to the cursor.

In the present invention, when a certain search area is searched and the maximum or minimum coordinate value is detected, the search range is immediately reduced at that point. Therefore, there is a possibility that other pixels exist in the certain search area, but even if the operation of detecting other pixels is omitted, the present invention reliably detects the pixels closest to the cursor position. It is possible to select pixels that are

The reason is simple. This is because the size of the search area to be reduced is the size that touches the detected pixel as shown in FIG.

A supplementary explanation will be provided using FIG. 2. For example, when searching in search area _B1 , when pixel _A1 is detected first, the search area is immediately reduced to search area _B2 adjacent to pixel _A1 , even though pixel _A2 exists. Next, when searching in this search area _B2 , the pixel _A2 closest to the cursor is detected.

If pixel A ₂ is detected first in search area B ₁ , it will be searched immediately in search area B ₃ , so the coordinates can no longer be detected and the pixel
A ₂ is the pixel closest to the cursor.

The flow of such operation is shown in FIG.

As explained above, according to the present invention, the following effects can be obtained.

(a) Since the search range is narrow as described in FIG. 2, the search time is shortened compared to the conventional case.

Although the first search range _B1 is a rectangle matching the size of the cursor in FIG. 2, it is not limited to this. That is, it may be larger or smaller than the cursor size. Further, the shape may be other than a rectangle.

(b) The results of a search as described in (a),
When a certain coordinate value is detected for the first time, the search range is immediately reduced at that point, so there is no need to search the remaining area in area _B1 , and the search time is further shortened.

(c) Since the maximum and minimum coordinate values of the database are used to determine whether an object belongs to the search range, it is not affected by the shape of the pixel and the scanning speed is fast.

Note that if the area of the search range is made infinitely small, it is impossible to predict when the search will end. Therefore, in the present invention, a certain limit is set for the area (B ₃ in FIG. 2) when the search range is reduced, and the search ends within that range.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a display example of a CRT screen of a CAD device, Figure 2 is an enlarged view of the cursor area in Figure 1, Figure 3 is a diagram showing the concept of a database, and Figure 4 is a diagram showing the invention of the present invention. FIG. 3 is a diagram showing an example of an operation flow. 1...Cursor, _A1 to _A6 ...Pixels, _B1 to _B3 ...
…area.

Claims (1)

[Scope of Claims] 1. A device that displays each pixel on a CRT by providing maximum and minimum coordinate data on a display plane for each pixel, and which displays a plurality of pixels displayed on a CRT screen. In the method of detecting the pixel closest to the cursor position, the first step is to search for the presence or absence of the maximum or minimum coordinate data in an area that moves as the cursor moves; When the maximum or minimum coordinate data is detected, a second step of reducing the cursor to a new area touching the pixel A1 corresponding to the detected maximum or minimum coordinate data at that point; and the first step; a third step of repeating the second step, successively reducing the area up to a preset size, and recognizing that the pixel remaining in the smallest area is the pixel A2 closest to the cursor position; How to detect displayed figures.