JPH0620062A - Graphic plotting device - Google Patents

Abstract

PURPOSE:To eliminate a need to plot each graphic element in the order like drawing with one stoke by subjecting each of plural graphic elements constituting a closed curve to start point processing and end point processing. CONSTITUTION:A processor 1 sends definition data of graphics constituting the closed curve to a coordinate generating circuit 4 by the program stored in a main memory 2 and instructs the start of plotting. The coordinate generating circuit 4 receives this graphic definition data to calculate the coordinate displacement in accordance with the definition and outputs plotting coordinates P, coordinate displacement information PD, a start point signal STP, and an end point signal EDP. A flag generating circuit 5 receives coordinate displacement information PD, the start point signal STP, and the end point signal EDP from the coordinate generating circuit 4 and generates a flag value FV in accordance with these inputs and an internally provided flag definition table 54. The flag definition table 54 is retrieved by two values of an incoming direction ID and an outgoing direction OD.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic drawing apparatus, and more particularly to a graphic drawing apparatus for drawing a graphic in which the inside of a closed curve is filled on a computer display or a printer.

[0002]

2. Description of the Related Art Conventionally, in a graphic drawing apparatus, a process of setting a closed curve on a bitmap memory and filling its internal area has been performed. As one of the methods, there is a closed curve filling method called an edge flag algorithm. Since this method is relatively easy to implement in hardware and can perform high-speed processing as compared with other closed curve filling methods, there is an LSI for closed curve filling processing using this algorithm.

The edge flag algorithm requires the use of a working memory in the course of processing. At this time, the working memory is assumed to have the same two-dimensional coordinates as the frame buffer memory. Therefore, the storage element on the working memory corresponding to a certain drawing coordinate is called a pixel, like the storage element on the frame buffer memory.

By the way, the definition of the inside of the closed curve is performed as follows for filling. "When we consider an infinitely thin line that defines a closed curve, it is inside if the midpoint of the pixel is inside the closed curve and not at the boundary. The midpoint is on the boundary and the inside of the closed curve is immediately to the right (x Increasing direction)
Pixels at, and pixels whose center is along a horizontal edge and the inside of the closed curve is directly below (in the direction of increasing y) are also inside. The method of filling the inside of the closed curve by the edge flag algorithm will be described with reference to FIG.

(1) First, drawing coordinates of graphic elements such as a plurality of line segments and curves forming a closed curve are sequentially generated one by one using a DDA (digital differential analyzer) or the like. In FIG. 9, the closed curve is composed of four line segments, and the drawing coordinates are P0,
It is generated in the order of P1, ..., P19, P20.

(2) Next, a flag value is determined based on the positional relationship between one drawing coordinate and the coordinates before and after the drawing coordinate. For example, P1 is connected to P0 and P2, and the flag value is determined for each drawing coordinate by such a connection relationship.

(3) Next, the pixel corresponding to the drawing coordinate on the working memory is operated based on the flag value. Specifically, the flag value is added to the original pixel value, and the result is used as the new pixel value.

(4) Next, with respect to the drawing coordinates corresponding to all the graphic elements (four line segments) that form the closed curve, (1) to (3) are repeated until the operation by the flag value is completed.

FIG. 9A shows the state of the working memory after the processes up to (4). The circle (∘) pixel is the pixel generated as the drawing coordinate, and the value in the circle is the pixel value after being manipulated by the flag value.

(5) Next, the working memory is scanned,
The filled area is determined based on the value of each pixel written therein (scan processing). Whether each pixel is filled or not is determined by the number of turns (a value obtained by adding the values of the pixel of interest and all the pixels on the left side of the pixel of interest). In this case, a pixel whose number of turns is not 0 is determined to be a filled pixel.

(6) Next, fill data is given to the pixel in the frame buffer memory corresponding to the fill pixel in the working memory obtained in (5). FIG. 9 (B)
Is the fill data result drawn by the frame buffer memory. The X circles are filled pixels, and the simple mark (∘) indicates pixels that were generated as drawing coordinates but were not filled.

However, there are some problems in actually implementing this algorithm. One of them is the treatment of the definition start point and the definition end point of the closed curve. At the definition start point of the closed curve, there is no previous drawing coordinate required in (2). Similarly, at the definition end point, there is no drawing coordinate after one. Therefore, the flag value cannot be determined at the definition start point and the definition end point. Therefore, in the prior art, it is assumed that the definition start point P0 and the definition end point P20 must have the same coordinates, the flag value is not determined in the process (2) for the start point P0, and only the connection direction from P0 to P1 is stored. Keep it. Then, after the processing is completed up to the end point P20, the P stored previously as the connection direction from the end point is further stored.
The connection direction from 0 to P0 is given, the flag value at the end point is determined, and the processing is completed.

When the closed curve is composed of graphic elements such as a plurality of line segments and curves, the drawing coordinates are generated at the definition start point of the closed curve (= the first graphic element) due to the same restrictions as the above-mentioned problems. From the start point) to the definition end point (= the end point of the last graphic element) in a single stroke, and at the connection point between graphic elements as well as other drawing coordinates, The flag value is calculated based on the positional relationship. Therefore, the half scan line method, which requires the use of special flag values at the connection points of graphic elements, cannot be used.

Here, the half scan line method is the next point at which the parameter given to the coordinate generation circuit for generating the drawing coordinates of each figure element is calculated, and the value of the parameter is corrected, and the drawing is performed by this corrected parameter. The method of generating the flag by using the coordinates has an effect of obtaining the filling result according to the definition regarding the inside of the closed region. At this time, at the start point and the end point of the graphic element, it is necessary to use a flag value determined according to the traveling direction of the graphic element.

When the half scan line method cannot be used, the drawing coordinates are distributed on both sides of the true locus of the given graphic element, and the pixels outside the defined closed area in the filled result are also set as the filled pixels. I will end up. Figure 9
P11, P13, P17, and P19 in (B) are pixels that are outside the closed region and are filled.

This problem is dealt with by using the definition of the filled area different from the definition of the inside of the closed area described above. Where the filled area is
It is defined as "inside the closed curve and on (the pixel generated as)." In order to carry out this definition, in addition to the first working memory for storing the flag value as the working memory, the second working for indicating that these pixels are pixels generated on the closed curve. Use memory. When performing the operation with the flag value for the first working memory, at the same time, for the second working memory, pixels are set to indicate that these coordinates are on the boundary of the closed curve. An operation of including the pixel in the filled pixel is performed using the first working memory. In the case of FIG. 9B, a pixel with a simple circle (◯) is also determined to be a filled pixel.

[0017]

As described above, in the conventional graphic drawing apparatus, in the drawing by the edge flag algorithm, the drawing coordinates must be continuous when the flag value is determined from the definition of the closed curve. was there. Therefore, when the closed curve is defined by a plurality of graphic elements, it is required that the end points and the start points of the respective graphic elements are connected and drawn continuously in a single stroke. Further, since the flag value is obtained only from the positional relationship between the pixel of interest and the pixels before and after it, the half scan line method cannot be used, and pixels outside the true boundary of the area within the closed curve are also filled pixels. Therefore, when there are mutually exclusive closed curves that share a boundary line, pixels on the shared boundary line are determined to belong to a plurality of closed areas at the same time, and may be filled in multiple times. further,
The conventional method requires the second working memory for additional work in addition to the originally required first working memory. This causes the cost to increase due to the increase in the memory capacity, increases the number of memory accesses, and causes the drawing speed to decrease.

[0018]

The graphic drawing apparatus of the present invention is, for each graphic element forming a closed curve, drawing coordinate information, coordinate displacement information of these graphic elements, a starting point signal indicating the starting point of these graphic elements, and an end point. And a coordinate definition circuit that generates an end point signal that indicates a coordinate value, and a flag definition table that defines a flag value for each drawing coordinate based on the traveling direction information and the approach direction information, and the coordinate displacement information when the starting point signal is an inactive level. According to the approach direction information based on the coordinate displacement information when the end point signal is the inactive level, and based on the approach direction information based on the start direction information when the active level is active level. A flag generation circuit for generating the flag value and an address corresponding to the drawing coordinates of each graphic element of the closed curve. A working memory for storing pixel values, a memory control circuit for storing a pixel value determined according to the flag value at an address corresponding to each drawing coordinate of the working memory, and the working memory And a processor that reads out pixel values at each of the drawing coordinates and generates fill data for the closed curve.

Further, a function for generating an access control signal including a pending request, a pending removal, and a pending cancellation instruction is added to the flag generation circuit, and the memory control circuit receives the drawing data for the working memory by the access control signal. It is configured by adding a function of instructing write reservation, cancellation of write reservation, and cancellation of reserved drawing data.

[0020]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1A and 1B are a block diagram of a first embodiment of the present invention and an internal block diagram showing a concrete example of a flag generation circuit of this embodiment, respectively.

In this embodiment, drawing coordinate information P, coordinate displacement information PD of these graphic elements, a start point signal STP indicating the start point of these graphic elements, and an end point are set for each graphic element which receives the graphic definition data and forms a closed curve. End point signal EDP shown
The start point signal STP is provided with a coordinate generation circuit 4 for generating the following, selectors 51 and 52 latch circuits 53, and a flag definition table 54 that defines a flag value FV for each drawing coordinate P based on the traveling direction information OD and the approach direction information ID. Is the inactive level, the traveling direction information OD based on the coordinate displacement information PD, the active level is the traveling direction information OD based on the ending direction information EDD, and the end point signal EDP is the inactive level, the traveling direction information is based on the coordinate displacement information PD. In order to store the pixel value in the flag generation circuit 5 that generates the flag value FV according to the approach direction information ID based on the start direction information STD when the ID is the active level and the address corresponding to the drawing coordinate P of each graphic element of the closed curve. Of the work memory 7 and the drawing coordinates P of the work memory 7 The memory control circuit 6 for storing the pixel value determined according to the flag value FV at the address and the graphic definition data according to the program are supplied to the coordinate generation circuit 4, and the pixel value of each drawing coordinate is read from the working memory to fill the closed curve. Processor 1 for generating
And a frame buffer memory 3 for storing fill data and a main memory 2 for storing a program and data for drawing graphics. The flag definition table 54 is, for example, as shown in FIGS.
The contents are as shown in.

Next, the operation of this embodiment will be described.
FIG. 3 is a processor 1 for explaining the operation of this embodiment.
9 is a flowchart showing the processing of the coordinate generation circuit 4.

First, the processor 1 sends the definition data of the figure forming the closed curve to the coordinate generation circuit 4 by the program stored in the main memory 2 to instruct the drawing start. When the coordinate generation circuit 4 receives the graphic definition data, it calculates the coordinate displacement according to the definition (step S11) and outputs the drawing coordinate P, the coordinate displacement information PD, the start point signal STP and the end point signal EDP (S12). Here, the coordinate displacement information PD is the drawing coordinate P being output at a certain time.
Is information indicating the displacement of the next drawing coordinate.
In the example of FIG. 4, when the drawing coordinate is P1, the next coordinate is P2, and the coordinate displacement is (dx = + 1, dy = + 1).
Becomes This is encoded by the code of the direction definition shown in FIG. 2 (A), and the coordinate displacement information = 3. The start point signal STP and the end point signal EDP are "1" for the first drawing point and the last drawing point when drawing a figure, respectively.
Is the signal. In FIG. 4, the start point signal STP becomes “1” when the drawing coordinate is P0, and the end point signal ED when P16.
P becomes "1". These signals are supplied to the flag generation circuit 5
Is input to. After the output of each signal, the coordinate displacement PD is added to the drawing coordinate P, and the data becomes the drawing coordinate data (S13).

The flag generation circuit 5 receives the coordinate displacement information PD, the start point signal STP, and the end point signal EDP from the coordinate generation circuit 4, and generates a flag value FV according to the inputs of them and the flag definition table 54 contained therein. here,
The flag definition table 54 has an approach direction ID and a traveling direction OD.
It is a table searched by two values of.

Basically, the traveling direction OD is the coordinate displacement information PD input at that time, and the approaching direction ID is 1.
It is the coordinate displacement information PD before the rotation. However, the approach direction ID is not defined when drawing the start point, and the traveling direction OD cannot be defined when drawing the end point. Therefore, by switching the inputs of the selectors 51 and 52 using the start point signal STP and the end point signal EDP, and selecting the start direction STD and end direction EDD which are defined in advance at the time of drawing the start point and the end point, an undefined state does not occur. To do so. In the case of FIG. 4 as the start direction STD and the end direction EDD, the direction of “4”,
The direction is “0”.

The memory control circuit 6 receives the drawing coordinate P from the coordinate generating circuit 4 and the flag value FV from the flag generating circuit 5, and follows the flag value FV in an address corresponding to the coordinate P on the working memory 7. Do the operation. There are three types of flag values, "+1", "-1", and "0", and the memory control circuit 6 adds the flag value to the pixel value and sets the result as a new pixel value.

When the drawing of all the figures on the working memory 7 is completed (S3), the processor 1 performs the scanning process (S).
4) Start. This is the same as the processing in the prior art,
The information on the working memory 7 generated in the above process is read out, and the area to be filled is determined according to the contents,
The fill data is written in the corresponding frame buffer memory 3.

In this embodiment, the flag values of the drawing start point and the drawing end point of each figure can be determined when the drawing coordinates of these points are generated, so that the closed curve becomes a single stroke like the prior art. You don't have to be. For example, the closed curves in FIG. 4A have P0 to P4, P4 to P8, and P8 to P1.
If it is composed of four graphic elements 2, P12 to P16, there is no need for a drawing order relationship between the respective graphic elements. Looking at P4, since it is the end point in the figures P0 to P4, the approach direction = 3, the advancing direction = the ending direction = 4, and the flag value is -1 + 0 = -1. This final flag value is a value equal to the flag value obtained when drawing is performed continuously with P3-P4-P5, and the same can be said for other drawing coordinates. All that is required is that the end point and the start point of each graphic element are finally arranged in a single stroke and form a closed graphic.

FIGS. 5A and 5B are a block diagram of the second embodiment of the present invention and an internal block diagram showing a concrete example of the flag generation circuit of this embodiment.

This embodiment is different from the first embodiment shown in FIG. 1 in that an access control signal AC from the flag generation circuit 5a to the memory control circuit 6a is newly provided and the flag definition table 54a. Is to use the up / down flag UD generated from the approach direction ID as the third input to the. Accordingly, the contents of the flag definition table 54a are as shown in FIG.

Next, the operation of this embodiment will be described.
FIG. 7 is a flow chart showing the processing of the coordinate generation circuit and the memory control circuit for explaining the operation of this embodiment. The operations of the processor 1 and the coordinate generation circuit 4 are the same as in the first embodiment.

The flag generation circuit 5a obtains the flag value FV and the access control signal AC by referring to the flag definition table 54a using the approach direction ID, the advancing direction AD, and the up / down flag UD. Here, the up / down flag UD is a flag that holds the vertical moving direction before that when the approach direction ID is in the horizontal direction (“2”, “6” direction), and when it is “0”, it is directed upward (“7”, "0", "1" direction), and when it is "1", downward ("3", "4", "5")
Direction).

The access control signal AC is a signal indicating an instruction to the memory control circuit 6a, and the content of the instruction is four types of "pending request", "pedging removal", "pending release", and "normal". Memory control circuit 6
a is a flag p and an access control signal A contained therein.
Drawing with respect to the working memory 7 is controlled by C and.
When the access control signal AC is the "pending request RQ", the memory control circuit 6a latches the drawing coordinate P and the flag value FV which have been input at that time, and does not perform drawing. Then, a flag p indicating that the drawing has been bent is set (S25). The drawing request latched by the "bending removal RQ" is deleted (S26). The “pending release RL” executes the drawing request latched by the “pending request RQ”. After the drawing is executed, the flag p is reset (S2
8). In "normal NO", when the flag value is "0", nothing is done. When the flag value is other than "0", the required drawing is executed and the flag p is reset (S29).

After the drawing on the working memory 7 is completed, the processor performs the scanning process. Here, the access control will be specifically described with reference to FIG. In FIG. 8A, two line segments are drawn. First, the line segment Q0-Q6
Looking at it, since the point Q0 is the starting point, the approach direction = starting direction = 4, the flag value is “−1”, and the access control is “pending request RQ”. Therefore, the memory control circuit 6a latches the drawing coordinate of Q0 and the flag value of "-1". Further, the up / down flag UD of the flag generation circuit 5a becomes "1". In Q1 and Q2, the flag value is "0", the access control is "normal NO", and the memory control circuit 6a
Does nothing. Since it moves horizontally, the up / down flag UD also does not change. In Q3, the flag value is "0", the access control is "pending removal RM", and the drawing request for Q0 latched until then is invalidated. The result of the above sequence is equivalent to the flag value at Q0 being "0".

Next, looking at the line segments R0-R6, R0 to R2 are the same as Q0 to Q2. However, in R3, the flag value is "0", the access control is "pending release RL", and the drawing request of R0 which has been latched until then is executed. That is, the flag value at R0 is "-1".

The half scan line method is used here in order to more accurately represent the figure after painting. The resulting drawing coordinates are generated on the defined line segment or on the right side of the line segment, as shown in FIG.
When the two line segments in FIG. 8A are combined so that Q6 and R0 have the same drawing coordinates and the space between these two line segments is filled,
It becomes like FIG. 8 (B). From the definition of the region by the above-mentioned closed curve, the vertices indicated by double circles (⊚) are not subject to be filled, and the method according to the present invention is not subject to be filled. However, if the flag value is obtained only from the coordinate displacement of the front and rear drawing coordinates as in the prior art, this vertex will also be included in the filled area.

In these embodiments, the contents of the flag definition tables 54, 54a are constructed by using the direction codes of 8 directions as shown in FIGS. However, as is clear from FIGS. 2 and 6, it is easy to compress the table because the input to this table is not required to be in 8 directions but to be in 4 directions. Further, it is possible to consider a definition in which the upper and lower sides and the left and right sides are interchanged in the definition of the inside of the closed curve, but it is possible to easily cope with them by exchanging some values in the flag definition table.

[0039]

As described above, according to the present invention, the start point processing and the end point processing are performed for each of a plurality of graphic elements that form a closed curve. This has the effect of eliminating the need to draw in such an order. For example, in the case of a figure such as a rounded rectangle, it is possible to draw a straight line part at the tip and then draw a rounded part. In addition, the half scan line method can be realized by obtaining the flag values of the start point and the end point in each graphic element on the spot, and delaying the drawing by the flag value by using the access control. Even if the figure to be composed is a line segment, you can set a flag value to accurately fill only the inside of the defined area, so even if multiple areas that share the boundary line are adjacent There is an effect that it is not attempted to paint multiple pixels or to leave unpainted.

Furthermore, in the prior art, the working memory is 2
However, the present invention requires only one working memory. If the fill rule is the odd-even rule, the working memory is 1 bit / pixel. In the prior art, the second working memory also only indicates whether or not the pixel is on the boundary.
Bits / pixel required. Therefore, in the case of using the odd rule, the conventional technology requires a total of 2 bits / pixel,
The present invention has an effect that the filling processing can be performed with half the memory capacity of the conventional one. In addition, since the number of times of accessing the memory can be reduced, there is an effect that higher speed processing can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention and an internal block diagram showing a specific example of a flag generation circuit thereof.

FIG. 2 is a diagram showing the contents of a flag definition table of the embodiment shown in FIG.

FIG. 3 is a flowchart of processing for explaining the operation of the embodiment shown in FIG.

FIG. 4 is a diagram showing an example of a graphic drawn by the embodiment shown in FIG.

FIG. 5 is a block diagram of a second embodiment of the present invention and an internal block diagram showing a specific example of a flag generation circuit thereof.

6 is a diagram showing the contents of a flag definition table of the embodiment shown in FIG.

FIG. 7 is a flowchart of processing for explaining the operation of the embodiment shown in FIG.

FIG. 8 is a diagram showing an example of a graphic drawn by the embodiment shown in FIG.

FIG. 9 is a diagram showing an example of a graphic drawn by a conventional graphic drawing apparatus.

[Explanation of symbols]

 1 processor 2 main memory 3 frame buffer memory 4 coordinate generation circuit 5, 5a flag generation circuit 6, 6a memory control circuit 7 working memory 51, 52 selector 53 latch circuit 54, 54a flag definition table 55 gate circuit

Claims (2)

[Claims] 1. A coordinate generation circuit for generating, for each graphic element forming a closed curve, drawing coordinate information and coordinate displacement information of these graphic elements, a start point signal indicating the start point of these graphic elements, and an end point signal indicating the end point thereof. A flag definition table that defines a flag value for each drawing coordinate based on the traveling direction information and the approaching direction information is provided. Direction information by information,
When the end point signal is an inactive level, the approach direction information based on the coordinate displacement information, and when the end level signal is an active level, a flag generation circuit that generates the flag value according to the approach direction information based on the start direction information, and each graphic element of the closed curve. A working memory for storing a pixel value at an address corresponding to a drawing coordinate; and a memory control circuit for storing a pixel value determined according to the flag value at an address corresponding to each drawing coordinate of the working memory. A graphic drawing apparatus, comprising: a processor that reads pixel values at the drawing coordinates from the working memory and generates fill data for the closed curve. 2. A flag generation circuit is provided with a pending request,
A means for generating an access control signal including an instruction of pending removal and pending cancellation is added, and the memory control circuit reserves writing of drawing data to the working memory according to the access control signal, cancels writing reservation, and reserved drawing data. 2. The graphic drawing apparatus according to claim 1, further comprising means for instructing cancellation of.