JPH07122906B2 - Graphic display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device such as a graphic display device or a laser beam printer, which is a graphic display device for filling an arbitrary polygon.

2. Description of the Related Art Conventionally, the following methods have been used as methods for filling the inside of an arbitrary polygon.

(1) A method of dividing an arbitrary polygon into convex polygons and filling each convex polygon.

(2) Coordinates of points (contour points) on each side of the polygon are calculated, contour points on the same horizontal or vertical scanning line are sorted in the order of coordinates, and points between adjacent contour points are drawn. By this method, the inside of the polygon is filled.

(3) Turn the coordinates of the points (contour points) on each side of the polygon clockwise,
Alternatively, a method of sequentially calculating in a counterclockwise direction, and when two contour points on the same scanning line in the horizontal or vertical direction appear, the inside of the polygon is filled by inverting the points between the two points (for example, There is "JP-A-57-101886").

Problems to be Solved by the Invention However, each of the above methods has the following problems.

The method (1) requires a process of dividing an arbitrary polygon into convex polygons, which is slow in speed. In addition, the mechanism for managing the divided convex polygons becomes complicated.

The method (2) requires a large-scale storage means for storing the contour points, and sorting the contour point coordinates is complicated and time-consuming.

Although the method of (3) is much smaller than the method of (2), since the coordinates are stored in a table format using the y coordinate value as an index, the coordinate storage unit is large, In addition, each time a coordinate value is stored or retrieved, the presence / absence of a coordinate value is determined, writing, reading,
It is necessary to access the coordinate storage unit a plurality of times to perform an operation such as erasing.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a graphic display device which fills an arbitrary polygon at high speed with a simple operation and a small capacity storage means.

Means for Solving Problems The present invention, in order to solve the above problems, a coordinate calculation unit that sequentially calculates coordinate data of points on the sides of a polygon from the coordinate data of the vertices of the polygon, and the coordinates. A first-in-first-out type coordinate storage unit that stores the coordinate data calculated by the calculation unit, and a change in the coordinate calculation direction in the coordinate calculation unit is detected, and the coordinate data calculated by the coordinate calculation unit is stored in the coordinate storage unit. A control unit that switches between storing the data in a copy section or extracting coordinate data from the coordinate storage unit and forming a pair with the data calculated by the coordinate calculation unit and drawing a straight line connecting the two points. The graphic display device includes a straight line drawing unit that reverses display data of a point between two points on the image memory from coordinate data of the point.

Function In the present invention, in any polygon, the horizontal or vertical scanning line except the apex (singular point) intersects the contour of the polygon at an even number of times, and these intersections are grouped every two points. Paying attention to the fact that inversion of display data between two points can realize filling in a polygon having a concave portion, and the following operation is realized by the above configuration.

The coordinate calculation unit sequentially calculates coordinates of points on each side of the polygon, that is, coordinates of intersections of each side of the polygon and each scanning line by tracing the contour clockwise or counterclockwise. Initially, the coordinates of the other contour points on the same scanning line forming a set have not been calculated yet, so the control unit stores the calculated coordinate data in the coordinate storage unit. After that, when the coordinate calculation direction is reversed in the coordinate calculation section, the coordinates of another contour point on the same scanning line as the point previously calculated and stored in the coordinate storage section are sequentially calculated. The coordinate calculation direction referred to here is the direction of change in the coordinates that serve as a reference during coordinate calculation. For example, if the scanning line is parallel to the x-axis, the coordinate calculation unit calculates the coordinate while increasing or decreasing the y coordinate value by one. The changing direction of the y coordinate value at this time, that is, the positive or negative of the y coordinate increment is called the coordinate calculating direction.

This coordinate calculation direction is from the positive direction to the negative direction, or
When the direction is changed from the negative direction to the positive direction, the coordinate calculation direction is said to be reversed. It should be noted that the direction of the side may pass through the scanning line direction (y coordinate increment 0) in which the direction of the side coincides with the direction of the scanning line during the direction change. However, for the points on the side in the scanning line direction, neither the calculated coordinate data is stored nor the straight line drawing is performed.

When the coordinate calculation direction is reversed in the coordinate calculation unit, the control unit fetches the coordinate data already stored from the coordinate storage unit one by one, each time the coordinate data of the contour point is calculated by the coordinate calculation unit. Since the coordinate storage unit is a first-in, first-out type, the coordinate data is retrieved in the reverse order of storage. for that reason,
The coordinate data retrieved from the coordinate storage unit is always that of the contour point on the same scanning line as the calculated contour point.

In this way, the coordinate data of two points on the same scanning line (the coordinate data newly calculated by the coordinate calculation section and the coordinate data retrieved from the coordinate storage section) are obtained, and the straight line drawing section determines both points and both points. The display data on the image memory at the points between are inverted.

Thereafter, the control unit switches between the process of storing the coordinate data in the coordinate storage unit and the process of extracting the coordinate data from the coordinate storage unit and the straight line drawing process each time the coordinate calculation direction is reversed in the coordinate calculation unit.

The above operation is performed for all sides of the given polygon, and when the coordinate calculation unit finishes calculating the coordinates of all points on the polygon sides,
Filled polygons are generated.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the graphic display device of the present invention. Reference numeral 1 denotes a coordinate calculation unit that sequentially calculates the coordinates of points on the sides of a polygon, 2 is a first-in-first-out type coordinate storage unit that stores the calculated coordinate data, and 3 is a coordinate data storage unit 2 that stores the coordinate data. A control unit for switching between the storage process, the extraction of the coordinate data from the coordinate storage unit 2 and the straight line drawing process, 4 is a straight line drawing unit for reversely drawing the display data on the image memory between the two designated points, An image memory 5 stores display data.

The operation of the graphic display device of the embodiment of the present invention configured as described above will be described using the example of FIG.

In the following description, the horizontal direction is the x-axis direction, the vertical direction is the y-axis direction, the right direction is the x-axis positive direction, and the upper direction is the y-axis positive direction. In addition, for simplicity, the image is a monochrome binary image.

The coordinate calculation unit 1 sequentially calculates the coordinates of the intersection of each side of the polygon and the scanning line from the given polygon vertex coordinate data 6 along the contour. The direction of tracing the contour may be clockwise or counterclockwise, but in the following description, the case where the coordinate calculation is performed while tracing the contour counterclockwise will be taken as an example. Therefore, the coordinates are calculated on the side AB, the side BC, the side CD,
It is performed in order of side DA. The calculation method is based on the known DDA.
(Digital Differential Analyze) algorithm is used.

First, the coordinate calculation unit 1 sets the coordinate of the point on the side AB to the y coordinate of 1
Decrease each and calculate sequentially. The control unit 3 stores the calculated coordinate data in the coordinate storage unit 2. The coordinate data stored in the coordinate storage unit 2 need only be the x coordinate value.

In the coordinate calculation unit 1, when the coordinate calculation of the point on the side AB is completed and the coordinate calculation of the point on the side BC is started, the coordinate calculation direction on the side AB is the downward direction in which the y coordinate is gradually decreased. In contrast,
The coordinate calculation direction on the side BC is an upward direction in which the y-coordinate sequentially increases, and the coordinate calculation direction is reversed. The control unit 3 detects the reversal of the coordinate calculation direction, and switches the process of storing the coordinate data in the coordinate storage unit 2 to the process of extracting the coordinate data from the coordinate storage unit 2 and the straight line drawing process. That is, each time the coordinate calculation unit 1 calculates the coordinate data, the coordinate data stored in the coordinate storage unit 2 in the previous coordinate data storage process is taken out one by one. Since the coordinate storage unit 2 is of a first-in, first-out type, the coordinate data is retrieved in the reverse order of storage. Therefore, the y-coordinate value of the extracted coordinate data changes opposite to that at the time of storage. That is, the changing direction of the y coordinate when the coordinate data of the point on the side AB that has been stored once is taken out is the coordinate calculation direction on the side BC (direction in which the y coordinate is increased by 1).
Matches Since the point B is common to the side AB and the side BC, naturally, the y coordinate of the point B is the same, and the point on the side BC calculated by the coordinate calculation unit 1 changes from the same y coordinate in the same direction. And the y coordinate of the coordinate data of the point on the side AB taken out from the coordinate storage unit 2 every time the coordinate is calculated by the coordinate calculation unit 1. In this way, the coordinates of the same y coordinate, that is, the coordinates of two points on the same scanning line are obtained. The straight line drawing unit 4 inverts the display data on the image memory of the two points thus obtained and the points between them. When the image memory is initially set to white for all dots, it becomes black due to inversion.

When the coordinate data is extracted from the coordinate storage unit 2 and the straight line drawing process is performed up to the point E on the side BC, all the coordinate data in the coordinate storage unit 2 is consumed and the coordinate storage unit 2 becomes empty. At that time, the control unit 3 returns to the process of storing the coordinate data calculated by the coordinate calculation unit 1 in the coordinate storage unit 2 again.

After that, the control unit 3 reverses the coordinate calculation direction in the coordinate calculation unit 1, or every time the coordinate storage unit 2 becomes empty during the coordinate data extraction and straight line drawing process, the coordinate data storage process and the coordinate data are processed. Switching between data extraction and straight line drawing processing. Therefore, after the point E, the coordinate calculation unit 1 sets the side BC
While calculating the upper point, the coordinate data is stored, and the coordinate calculation unit 1 shifts to the coordinate calculation of the point on the side CD, and when the coordinate calculation direction is reversed (upward → downward), the coordinate The process proceeds to data extraction and straight line drawing processing. Side
Point F during CD coordinate data extraction and straight line drawing processing
Since the coordinate storage unit 2 is emptied again at, the storage process of the coordinate data is performed after the point F up to the point D where the coordinate calculation direction is reversed. When the coordinate calculation unit 1 shifts to the coordinate calculation of the point on the side DA, the coordinate data fetching and the straight line drawing process are performed with the reversal of the coordinate calculation direction (downward → upward). At this time, the inside of the triangle DAF is filled, but since the triangle DAF has already been filled with black, it is returned to white by inversion.

When the coordinate calculation unit 1 finishes calculating the coordinates of all points on the polygonal contour, the generation of the filled polygon is completed.

By the above operation, each point on the scanning line L (y = Y) that crosses the recess is smeared as follows.

(1) Coordinate calculation unit 1 coordinates of point α on side AB (Xα, Y)
Is calculated and the x coordinate value is stored in the coordinate storage unit 2.

(2) Coordinate calculation unit 1 coordinates of point β on side BC (Xβ, Y)
Is calculated, the x-coordinate Xα of the point α is retrieved from the coordinate storage unit 2, and the display data of the two points (Xα, Y), (Xβ, Y) and the point between them are inverted. When the initial state of the image memory is initially set to all white, the line segment αβ is filled with black.

(3) Coordinate calculation unit 1 coordinates of point γ on side CD (Xγ, Y)
Is calculated and the x coordinate value is stored in the coordinate storage unit 2.

(4) Coordinate calculation unit 1 coordinates of point δ on side BC (Xδ, Y)
Is calculated, the x-coordinate Xγ of the point γ is retrieved from the coordinate storage unit 2, and the display data of the two points (Xγ, Y), (Xδ, Y) and the points between them are inverted. That is,
In (2), since the line segment αβ including the line segment γδ is blackened out, the line segment γδ is inverted to return to white at this time.

In the example of FIG. 2, the description has been made of the case where an arbitrary polygon is filled with horizontal line segments, but the case of filling it in the vertical direction can be similarly realized.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to realize high-speed filling of an arbitrary polygon with only very simple processing. Furthermore, by realizing the coordinate storage unit with a first-in / first-out type memory, it is possible to realize with a small-scale memory corresponding to the height of the polygon to be displayed at most (length in the y-axis direction), and the coordinate storage unit. There is an effect that operations such as data presence / absence determination, data reading, and writing can be realized at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram of a graphic display device according to an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram of the device. 1 ... coordinate calculation unit, 2 ... coordinate storage unit, 3 ... control unit,
4 ... Straight line drawing section, 5 ... Image memory, 6 ... Polygon vertex coordinate data.

Claims (1)

[Claims] 1. A coordinate calculation unit for sequentially calculating coordinate data of points on a side of a polygon from coordinate data of vertexes of the polygon, and a first-in first-out type that stores the coordinate data calculated by the coordinate calculation unit. Of the coordinate storage unit and the change in the coordinate calculation direction in the coordinate calculation unit and store the coordinate data calculated by the coordinate calculation unit in the coordinate storage unit, or store the coordinate data from the coordinate storage unit. A control unit that takes out the data, calculates a pair with the data calculated by the coordinate calculation unit, and switches whether to draw a straight line connecting the two points, and a point between the two points on the image memory based on the coordinate data of the two points. And a straight line drawing unit for inverting the display data of the figure.