JPS6322354B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a system for inputting and displaying drawn images such as handwritten characters and figures, and by enclosing and specifying a part of the displayed screen with a curve, the display screen within the curve is erased. It is about the method.

First, a conventional method will be explained using drawings.

FIG. 1 shows a flowchart of the basic algorithm of partial elimination.

The method for determining the rectangular area to be erased will be described below with reference to FIG.

(1) How to find the line segment l _i parallel to the y-axis As shown in Figure 2, in the discrete point sequence among the sample points P ₁ to _{P 7} on the curve C ₁ input for partial elimination, When two consecutive points are P _i (x _i , y _i ), P _i+1 (x _i+1 , y _i+1 ), (x ₁ ⁽ⁱ⁾ , y ₁ ⁽ⁱ⁾ ), (x ₂ ⁽ⁱ⁾ , y ₂ ⁽ⁱ⁾ ) as the two endpoints, find the line segment l _i parallel to the y-axis using the following equation.

x^ ₁ ⁽ⁱ⁾ = (x _i +x _i+1 )/2 x^ ₂ ⁽ⁱ⁾ = x^ ₁ ⁽ⁱ⁾ y^ ₁ ⁽ⁱ⁾ = min (y _i , y _i+1 ) y^ ₂ ⁽ⁱ⁾ = max(y _i , y _i+1 ) (1) For the final input point P _N , find the line segment l _N with P ₁ as the adjacent point. Here, in line segment l _i, y ₁ ⁽ⁱ⁾ =
In the case of y ₂ ^(i), it is unnecessary and will be removed.

(2) How to find a straight line m _k parallel to the x-axis Rearrange the y coordinates of the input points P _i in descending order of magnitude, and let the rearranged coordinates be y~ ₁ , y~ ₂ , ..., y ~ _N.

If there are two or more with the same value in the calculated y ~ _k , leave only one and renumber it, y
₁ , y ₂ , ..., y _M (M≦N). Next, M straight lines parallel to the x-axis with the obtained y _k as the y-coordinate.
m _k is determined and divided into (M-1) strip regions as shown in FIG.

(3) How to find a rectangle to be erased within a strip area As shown in Figure 4, for a line segment l that crosses between straight lines m _k and m _k+1 , l' ₁ , l' ₂ in the order of x. ,...,l′ _2R
and number it. Note that even if there are multiple line segments l' having the same x coordinate, they are numbered as independent line segments.

When the x coordinate of l' _j is x' _j , the rectangular area to be erased is x _nio = x' _2j-1 x _nax = x' _2j (1≦j≦R) y _nio = y _k y _nax = y _k+1 (1≦k≦M−1), and the shaded area corresponds to this.

FIG. 5 is a block diagram showing the configuration of a conventional circuit that implements the above-mentioned partial erasure process, where 1 is a coordinate detection device such as a tablet (hereinafter referred to as a tablet), and 2 is a device for sampling x and y coordinate outputs. Sampler, 3 is a pen-touch detection circuit, 4 is a line segment calculator that calculates the line segment shown by equation (1), 5 is a y-coordinate recording circuit that records the y-coordinates of sample points in ascending order, and 6 is a line segment calculator. A line segment memory circuit stores the coordinates of the end points of the line segment determined by the device 4, and 7 indicates the x value included between the two y coordinates output from the y coordinate recording circuit 5.
A line segment extraction circuit extracts the x coordinate of a line segment l _i of a straight line m _k parallel to the axis, and 8 is erased from the y coordinate given from the y coordinate recording circuit 5 and the x coordinate value output from the line segment extraction circuit 7. Erase area designation circuit for determining area, 9
is the video memory. Further, in the figure, solid lines indicate the flow of signals such as coordinate values, and broken lines indicate the flow of control signals.

To operate this device, first
Enter the curve that represents the area you want to erase.
At this time, the pen-touch detection circuit 3 detects the pen-touch, operates the sampler 2, the line segment calculator 4, and the line segment storage circuit 6, and the coordinates of the line segment are sequentially recorded in the line segment storage circuit 6. When the input of the erase area is completed and the pen is lifted, the pen touch detection circuit 3 detects this,
The operation of the sampler 2, line segment calculator 4, and line segment storage circuit 6 is stopped, and the operation of the line segment extraction circuit 7 is started.
The line segment extraction circuit 7 reads the y-coordinate of a straight line m _k parallel to the x-axis from the y-coordinate recording circuit 5, and inputs the y-coordinate to the line segment storage circuit 6 in order to extract the line segment l _i existing within the band-shaped area. The coordinate values of all the stored line segments l _i are read out, a comparison operation is performed, and the x-coordinates of the line segments existing within the band-shaped area are transmitted to the erasure area specifying circuit 8 . An erasure area specifying circuit 8 calculates an erasure area within the strip area and erases the video memory of the area.

In this way, in the conventional device, in order to extract line segments existing within a band-shaped area, all line segments stored in the line segment storage circuit 6 are read and judged, and this operation is repeated for each band-shaped area. Since it is necessary to return the data, processing time increases rapidly as the number of input sample points increases, resulting in poor operability.

The present invention was made to solve these drawbacks, and takes advantage of the fact that many of the line segments existing in adjacent strip areas are the same line segment or line segments with consecutive numbers. Every time a strip area is processed, the number of the line segment existing in that strip area is memorized,
This method attempts to shorten the search time by searching for a line segment existing in the next strip area based on the above-mentioned stored numbers, and will be described in detail below with reference to the drawings.

FIG. 6 is an explanatory diagram showing the interrelationship of line segments existing in two adjacent band-shaped areas, and is an explanatory diagram showing the mutual relationship of line segments existing in two adjacent band _-shaped areas, and line segments _{l i and}
The relationship between l _i and the line segments existing in the strip area of straight lines m _k and m _k+1 is that line segments l _i+1 have consecutive numbers, and l _j are the same line segment. ing.

FIG. 7 is a block diagram showing the configuration of an embodiment of the present invention, in which a line segment counter 10 and a line segment number storage circuit 1 are added to the conventional partial erase processing circuit shown in FIG.
1 is added.

First, the line segment counter 10 will be explained. The line segment counter 10 operates when an erasure area is input, and is provided to measure and record the number of intersections (including end points) of the straight line m _k belonging to the straight line group and the line segment l ₁ . In principle, it is sufficient to memorize the number of intersecting line segments of the y-coordinates where the straight line m _k exists, but in this embodiment, in order to simplify the configuration, only the number of y-coordinates is stored corresponding to all y-coordinate values. Measure the number of line segments
A counter is provided for holding. To operate the line segment counter 10, as in the conventional circuit,
First, the line segment calculator 4 calculates the coordinates of the end points of the line segment _l1 according to the input of the sample point sequence, and outputs the result to the line segment storage circuit 6 and at the same time to the line segment counter 10. Next, the line segment counter 10 receives the two end point y-coordinate signals of the line segment l ₁ output from the line segment calculator 4 (y^ ₁ ⁽ⁱ⁾ and y^ ₂ ⁽ⁱ⁾ ; however, y^ ₁ ⁽ⁱ⁾ < y^ ₂ ⁽ⁱ⁾ ), performs an operation of adding 1 to the contents of the counter corresponding to y^ ₁ ⁽ⁱ⁾ ≦y≦y^ ₂ ⁽ⁱ⁾ , and holds the result. Here, line segment l ₁ and
Considering the case where l ₂ is input as shown in Figure 8, the line segment counter state immediately after line segment l ₂ is input is as shown in Figure 9, and after l ₂ is input, is as shown in FIG. Note that the counted result is referred to when the line segment extraction circuit 7, which will be described later, operates after the erasure area input operation is completed. In other words, when the line segment extraction circuit 7 specifies a y-coordinate value, the contents of the counter corresponding to the y-coordinate are output to the line segment extraction circuit 7.

Next, the line segment number storage circuit 11 will be described.
The line segment number storage circuit 11 is a temporary storage circuit used when the line segment extraction circuit 7 extracts line segment numbers existing in each strip area, and stores the line segment number specified by the line segment extraction circuit 7. Output the line segment numbers inside to the line segment extraction circuit 7, Delete the line segment numbers specified by the line segment extraction circuit 7 from memory, Check whether all line segment numbers specified by the line segment extraction circuit 7 are stored. It has the function of searching whether or not it is true or not and outputting the result to the line segment extraction circuit 7. Line segment number storage circuit 1 at each processing time
What kind of data (line segment number) is stored in 1 depends on the operation of the line segment extraction circuit 7, so below we will explain the process by which the line segment extraction circuit 7 extracts line segments in each strip area. Explain. The first swath (i.e.
y ₁ ≦y≦y ₂ ), all the line segments (l ₁ to l _N ) stored in the line segment storage circuit 6 are processed as in the conventional circuit.
Search for. All line segment numbers extracted at this time are stored in the line segment number storage circuit 11.

For the second and subsequent band-shaped regions, line segments are extracted using the following procedure. FIG. 11 is an explanatory diagram for extracting a line segment existing in a strip area B from the stored information of the strip area A in two adjacent strip areas A and B.

In the figure, consider the point in time when processing of a band-shaped region A sandwiched between straight lines m _k-1 and m _k is completed. At this point, numbers a, b, c, and d are stored in the line segment number storage circuit 11. To process the strip area B sandwiched between straight lines m _k and m _k+1 , first, the value K of the line segment counter 10 at the y coordinate y _k corresponding to the straight line m _k is read out.

Next, the line segment with the number stored in the line segment number storage circuit 11 is searched, and for the line segment where y _k =y^ ₂ ⁽ⁱ⁾ , that number is deleted. At this time, remember the number _K1 erased.

), the line segments with numbers before and after the erased number (±1) are read out from the line segment memory circuit 6 and checked, and a line segment with y _k = y^ ₁ ⁽ⁱ⁾ exists. Then, that number is newly stored in the line segment number storage circuit 11.

When the above operations are completed, the number stored in the line segment number storage circuit 11 is set as _n1 , and n=K-
When K ₁ is set, if n=n ₁ (2), then all line segments existing in band-shaped region B have been extracted. If n>n ₁ , all the line segments stored in the line segment storage circuit 6 are searched from this time until the equation (2) is satisfied, and the line segments existing in the band-shaped area B are extracted. .

To give concrete numbers regarding FIG. 11, the number K stored in the line segment counter 10 for line segment m _k is six. In the initial state before processing the strip area B, the line segment number storage circuit 11 stores a,
Four numbers b, c, and d are stored. b and c are deleted according to the process in the previous section (i.e. K ₁ = 2)
Therefore, n=K-K ₁ =4. On the other hand, since the number n ₁ stored in the line segment number storage circuit 11 at this point is 2, n-n ₁ =2. Therefore, in this case, the two line segments are found by searching the entire line segment storage circuit 6.
e and f are extracted.

As explained above, according to the present invention, the number of comparison operations required to search the line segment memory circuit 6 is reduced to 1/M (where M is x The number of straight lines parallel to the axis is reduced to the order of
This has the advantage of improved operability.

[Brief explanation of drawings]

Figure 1 is a flowchart of the basic algorithm of partial elimination, Figure 2 is a diagram explaining how to find a line segment l _i parallel to the y-axis, and Figure 3 is a diagram explaining how to find a straight line m _k parallel to the x-axis. , FIG. 4 is an explanatory diagram of how to find a rectangular area to be erased, FIG. 5 is a block diagram showing the configuration of a conventional circuit for realizing partial erasure processing, and FIG. FIG. 7 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 8 is a schematic diagram explaining the processing of the present invention, and FIGS. 9 and 10 are diagrams used in the present invention. FIG. 11 is an explanatory diagram of the state of the line segment counter in which one of the band-shaped areas A and B in two adjacent band-shaped areas
FIG. 3 is an explanatory diagram for extracting line segments existing in the other band-shaped region B from stored information in the above. DESCRIPTION OF SYMBOLS 1... Tablet, 2... Sampler, 3... Pen touch detection circuit, 4... Line segment calculator, 5... Y coordinate recording circuit, 6... Line segment memory circuit, 7... Line segment extraction circuit, 8...
Erase area designation circuit, 9... video memory, 10... line segment counter, 11... line segment number storage circuit.

Claims (1)

[Claims] 1. In order to erase a part of a two-dimensional image stored in a video memory and displayed on a display device such as a CRT display, a position coordinate detector such as a graphics tablet is used to display the image. In a system that inputs a boundary line to define an erasure area on the entry surface of a position coordinate detector corresponding to the surface, and erases the image of the internal area surrounded by the boundary line from the displayed image, the erasure area In order to obtain the position coordinates of the boundary line for determining the boundary line, the order relationship in which the boundary line is input is saved, the coordinate values of the boundary line are sequentially detected at appropriate intervals in time or space, and the display screen is A means for obtaining a sequence of sample points expressed using a coordinate system to be described (e.g. means for successively finding a group of line segments parallel to an axis (for example, the y-axis) using two points in the sample point sequence, numbering and storing the found line segments; means for obtaining a group of straight lines parallel to the x-axis) using the first coordinate value (for example, the y-coordinate value) of each point in the sample point sequence; and each straight line belonging to the group of straight lines obtained by the means. and means for measuring and storing the number of intersections (including end points) of the line segment obtained by the above-mentioned means; means for searching and extracting line segments that cross the band-like area from the group of line segments obtained by the above-mentioned means for each of the divided band-like areas; means for storing, referencing, and erasing numbers at any time; and a plurality of rectangles connected in a strip area parallel to the second axis, which are created based on the line segments obtained by the above means. and means for converting an image stored in a video memory in a rectangular area into a predetermined value alternately from one end in the direction of a second axis.