JPH01132270A - Clipping system - Google Patents

Abstract

PURPOSE:To extract only data in a rectangular window out of polygon printing data so as to display or print it by obtaining an intersecting point of each side of the polygon data and each limit value of x-direction and y-direction of the rectangular widow. CONSTITUTION:When the polygon data after coordinate transformation such as enlarging, reducing, rotating or moving, that is, address values corresponding to the start point and the finish point of the respective side are transmitted sequentially from a coordinate transformation circuit 13, a decision circuit 22 decides whether the side intersects the limit values Xmin, Xmax or not, and when it intersects the limit value, the coordinate value of the intersecting point is calculated by an arithmetic part 21, and is stored in a memory buffer 24. Consecutively, the decision circuit 26 decides whether the side intersects the limit values Ymin, Ymax or not, and when it intersects the limit value, the coordinate value of the intersecting point is calculated by the arithmetic part 25, and the polygon data after clipping is calculated, and is outputted to a straight line generator 15. It is written in a frame buffer memory 16 from the straight line generator 15, and outputted to an LBP or a CRT.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is applicable to graphic displays or LBPs (laser beam printers) when printing line segments or polygons. The present invention relates to a clipping method that extracts and displays or prints only a portion contained within an arbitrary rectangular window area after conversion.

[Prior art]

Conventionally, in a graphic display or LBP,
The clipping method extracts and prints an arbitrary part of the print target, and the print data in the range where the print target is surrounded by the y-axis and straight lines parallel to the y-axis is composed of the y-axis and straight lines parallel to the y-axis. A method of clipping using a rectangular clipping area has already been developed and exists as a product.

However, at present, no method has been developed for extracting and displaying or printing only an arbitrary rectangular window area of print data in which the print object is surrounded by an arbitrary polygon.

[Problem that the invention seeks to solve]

While steering, use the graphic display or LBP.
When printing a line segment or a polygon, there are cases where it is desired to extract and print only the portion that falls within an arbitrary rectangular window area after coordinate transformation such as enlargement, reduction, rotation, and movement. In such a case, there is a problem that the above-mentioned conventional clipping method cannot deal with the problem.

The present invention has been made in view of the above points, and eliminates the above problems, and when printing line segments or polygons, after performing coordinate transformation such as enlargement, reduction, rotation, movement, etc. An object of the present invention is to provide a clipping method that extracts and displays or prints only a portion belonging to a rectangular window area.

[Means for solving problems]

In order to solve the above problems, the present invention provides a clipping method that includes a coordinate conversion circuit, a window clip circuit, etc., and converts the polygon of input arbitrary polygon print data into the starting point of each side using the coordinate conversion circuit. It is converted into polygon data indicated by the address value corresponding to the end point, and the window clip circuit calculates the intersection of each side of the polygon data with each limit value in the X direction and the y direction of the rectangular window, and the polygon print data is The system is configured to extract and output only the data within the rectangular window.

[Effect]

By configuring the clipping method as described above, only the data within the rectangular window can be extracted from the polygonal print data and output to a graphic display or LBP.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of a system that implements the polygon clipping method according to the present invention. In the figure, 11 is a computer that receives data from the host computer (HO8T) and controls each part, 12 is a memory buffer that temporarily stores data to be printed, and 13 is a computer that enlarges, reduces, rotates, and moves the print data. 14 is a window clip circuit that extracts only data within the size of the paper to be printed or an arbitrary rectangle; and 15 is a straight line generator that writes straight lines into the frame buffer memory 16. Further, the frame buffer memory 16 is an image memory that corresponds 1:1 to the resolution of the paper surface to be printed.

In the above system, polygonal data input from the host computer is subjected to coordinate transformations such as enlargement, reduction, rotation, and movement in the coordinate transformation circuit 13 under the control of the computer 11, and then is converted into an arbitrary rectangle by the wind clip circuit 14. Extract only the data in the frame buffer memory 16 from the generator 15 directly, and write it directly to the frame buffer memory 16 from the LBP or CRT.
Output to.

Figure 2 shows the X-axis limit value X a l a X a a in the extraction window clip circuit 1 in Figure 1.
t, and the Y window value 27 holds the y-axis limit value Ymla+Yam* in the window. Polygonal data after coordinate transformations such as enlargement, reduction, rotation, and movement are performed by the coordinate transformation circuit 13 (see Fig. 1);
That is, when the address values corresponding to the start and end points of each side are sent in order, the discrimination circuit 22 determines that the side has the limit value Xaln*.
Determine whether or not it intersects with Xmat, and if it intersects, arithmetic unit 2
1, calculate the coordinates of the intersection point and store it in the memory buffer 24.
Store in.

Subsequently, the discriminating circuit 26 has the side set to the limit value Y. It is determined whether or not the line intersects with +Yaat, and if it does intersect, the arithmetic unit 25 calculates the coordinate values of the intersecting point, calculates the polygon data after clipping, and outputs it to the straight line generator 15 (see FIG. 1).

FIG. 4 is a diagram showing the format of the data sent as the polygon data, and as shown in the figure, the first vertex and the last vertex are set to the address value X0. y, and the address value of each vertex is X++ yt+Xz+ 3'*+ ”
”+X□yIS.

The polygon data shown in Fig. 4 is converted to the window value x=X1 of
．． ．． ．． FIG. 5 shows a processing flow when clipping is performed by x=X1o.

First, the starting point X o r 3' o is read (step 101), and the starting point X o r 3'' is the window value x.
=X ta +, , X" It is determined whether it is inside or outside of (Step 104).For the starting point and the next point, window value x=Xa+.HX=X n m
z, and it is determined whether the area is inside or outside the area as shown in FIG. 6 (step 105). If the starting point is within and the next point is also within, output X 1+ 3' I (step 10
6).

If the starting point is inside and the next point is outside, then x=X,,I. ,
Find the intersection of ``x'' (Step 109), and output the intersection point (Step 110). Starting point is outside and next point x = X, a, x
” If it goes beyond the range of X, , then x = x,
The two intersections of al x = X and Sax are found (step 111), and the intersections are output (step 112).

If the starting point is outside and the next point is also outside, it is determined whether it is the end or not (step 113). If the above process has not been completed for all vertices, return to step 104 and repeat the process. . Also, if the above processing has been completed for all vertices, then the window value of y = Y,
,. , y=y, , , the same processing as above is performed.

As a result, each side of the polygon and each limit value Xm of the window
The intersection of lnrXrm*, + y, nl Yffi-,
Each vertex of the polygon data belonging to the window is determined. By outputting these intersection points and vertices to the direct generator 15, the direct generator 15 calculates a straight line connecting the intersection points, a straight line connecting the intersection points and the vertices, and a straight line connecting the vertices. write to. As a result, only the polygon data included in the window is extracted and written into the frame buffer memory 16.

Therefore, the data written in the frame buffer memory 16 can be displayed or printed.

〔Effect of the invention〕

As explained above, according to the present invention, each side of the polygonal data and the
Find the intersection with each limit value in the direction and y direction, extract and output only the polygon data within the rectangular window from any polygon print data, and extract only the data within the rectangle window from the polygon print data. An excellent effect can be obtained in that the image can be displayed or printed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a system that implements the clipping method according to the present invention, FIG. 2 is a functional block diagram showing details of the extraction window clipping circuit shown in FIG. 1, and FIG.
The figures are for explaining the clipping method according to the present invention, Figure 4 is a diagram showing the format of the data sent as the polygon data, Figure 5 is a diagram showing the flow of clipping processing, and Figure 6 is a diagram showing the format of the data sent as the polygon data. is the limit value X ,, m II and X
It is an explanatory diagram for determining whether it is inside or outside the area of tm l n. In the figure, 11... Computer, 12... Memory buffer, 13... Coordinate conversion circuit, 14... Wind clip circuit, 15... Direct generator, 16...
...Frame buffer memory.

Claims (1)

[Claims] Equipped with a coordinate conversion circuit, a window clip circuit, etc.
The coordinate conversion circuit converts the polygon of any input polygon print data into polygon data indicated by address values corresponding to the start and end points of each side, and the window clip circuit converts each of the polygon data. A clipping method characterized in that the intersections between the sides and each limit value in the x direction and the y direction of the rectangular window are found, and only data included in the rectangular window is extracted from the arbitrary polygon print data and output. .