JPH042999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a handwritten figure transmission device that transmits handwritten figures.

[Prior art]

Conventionally, there has been a device of this type as shown in FIG. In the figure, 1 is a coordinate detection unit, 2 is an A/
D converter, 3 is each time obtained by A/D converter 2
Monitor changes in the X coordinate Xi and Y coordinate Yi at ti,
A chain detection unit detects an 8-direction freeman chain of size 1 to obtain an 8-connected chain figure, and 4 is a chain that performs encoding for data compression on the 8-direction chain array obtained by the chain detection unit 3. An encoding unit 5 is a communication control unit that modulates and demodulates the data obtained by the chain encoding unit 4 as necessary and performs overall communication control in order to transmit the data through a line; 7 is a communication control unit 6 is a chain decoding unit that decodes the handwritten figure signal received by 6 into an 8-connected chain string; 6 is an image storage unit such as a video memory that stores the handwritten figure or the received figure as a dot image; 8 is an image storage unit such as a video memory; An image display unit, such as a CRT display, displays the contents of the image storage unit 6, and 9 is a line.

Next, the operation will be explained.

A handwritten figure is input through the coordinate detection section 1 to the A/D conversion section 2 as pen position coordinates (X, Y) and pen up/down signals (Z). Next, the A/D converter 2 samples the pen's position coordinates at regular intervals, and obtains the position coordinate signals Xi and Yi at each time ti and the up/down signal Zi of the pen at this time. Next, in order to obtain an 8-connected chain figure,
Changes in coordinates and Y coordinates are monitored by the chain detection unit 3, and when a displacement of magnitude 1 as shown in FIG. 2 occurs, the displacement is of magnitude 1 consisting of codes 0 to 7
It is displayed in an 8-way freeman chain. This 8-way freeman chain cord has a center position
A0 and each grid point A1 whose absolute value of its X or Y relative coordinate with respect to this center position A0 is 1.
It is determined by the direction of the line segment connecting ~A8.

The chain array in eight directions obtained by the chain detecting section 3 is then encoded for data compression by the chain encoding section 4. In this encoding method, for example, a Huffman code is assigned to the difference chain of the 8-direction Freeman chain based on the probability of appearance of the difference value, and for the start point of the stroke, a code indicating the start and its absolute coordinates are assigned. The stroke is encoded using X and Y, and at the end of the stroke, a code indicating the end is output.
The data encoded in this manner is modulated and transmitted as necessary in the communication control section 5.
Furthermore, when receiving data, the communication control section 5 demodulates the data and controls the overall communication. Further, the chain encoded by the chain encoding section 4 is sent to the communication control section 5, and at the same time, is also sent to the image storage section 6 and written into the image storage section 6. The contents of this image storage section 6 are then displayed on the image display section 8. Chain decoding section 7
The communication control unit 5 demodulates the received data as necessary and decodes the obtained signal, and writes information regarding the chain array obtained by this decoding to the image storage unit 6.

Since the conventional handwritten figure transmission device is configured as described above, very high-speed coordinate input, that is, very high-speed A/D, is required to always obtain 8-connected figures.
Conversion and chain detection were required. For example, if the resolution of the device is 4 dots/mm, the maximum writing speed is 1000.
In order to maintain this resolution down to mm/sec, the sampling frequency had to be as high as 4000 Hz. In addition, there is a drawback that the detection of the chain is easily affected by noise, and the detection of the 8-connected chain may not be in time for high-speed writing. Furthermore, when the transmission bit rate is low, the data compression rate is not very high, so there are disadvantages such as noticeable transmission delays on the receiving side.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and instead of directly sequentially detecting the 8-connected chain, the input coordinates are sampled at a constant period to obtain sample points. A linear interpolation process is applied to the relative coordinates between each sample point, and the relative coordinates are decomposed into 8 connected interpolation chains of size 1, and the resulting 8 connected interpolation chains have a size of M×N. A window is set, and when the chain train passes the outer frame of the window, a window chain code corresponding to the passing position is generated, and encoding is performed for this window chain train. It is an object of the present invention to provide a handwritten figure transmission device that can reliably generate an 8-connected chain even during high-speed handwriting, and can also increase the data compression rate and transmit data without delay even at a low transmission bit rate. It is said that

[Embodiments of the invention]

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

FIG. 3 shows a configuration diagram of a handwritten figure transmission device according to an embodiment of the present invention, in which 1 is a coordinate detection unit that detects the position coordinates (X, Y) of the pen and the up/down state of the pen; is the coordinate detection section 1
10 is the above-mentioned A/D conversion unit that A/D converts and samples the position coordinate signal (X, Y) obtained in , and also samples the up/down signal (Z) of the pen at the position coordinate. From the coordinates (Xi, Yi) of each sample point obtained by the A/D converter 2 and the up/down signal (Zi) of the pen, the relative coordinates of each sample point and the sample point immediately before it are subjected to linear interpolation processing. Therefore, it is an interpolation chain generating section that decomposes into 8-connected chain arrays, and the 8-connected chain arrays are made up of interpolation chains of size 1 connecting interpolation grid points. 11 sets a window consisting of M×N interpolation grid points for the interpolation chain sequence generated in the interpolation chain generating section 10, and when the interpolation chain sequence passes through the outer peripheral frame of the window, the window is set at that position. A window chain generation section 12 generates a corresponding window chain; 12 is a window chain encoding section that performs encoding for data compression on the window chain sequence obtained in the window chain generation section 11; 5 is a window chain encoding section 5; A communication control unit that modulates and transmits the handwritten figure signal encoded in the encoding unit 12 as necessary, demodulates the received data if demodulation is necessary, and also controls the overall communication. , 14 are received by the communication control unit 5,
a window chain decoding unit that decodes demodulated handwritten figure data into a window chain;
3 is a window that performs linear interpolation processing on the window chain sequence generated in the window chain generation unit 11 or the window chain sequence obtained in the window chain decoding unit 14 to generate an 8-connected chain sequence of size 1. The chain interpolation unit 6 is an image storage unit such as a video memory, which stores the 8-connected chain array of size 1 obtained in the window chain interpolation unit 13 as dot images of handwritten figures and received figures. , 8 is an image display section such as a CRT display for displaying the contents of the image storage section 6, and 9 is a line.

Next, the operation will be explained.

After the pen position coordinates (Xi, Yi) and the signal (Zi) indicating the up/down state of the pen at each time ti are input to the coordinate detection unit 1 at a sampling frequency of about 30Hz, these signals are converted into A/ D converter 2
is quantized and converted into discrete values at .
Next, in the interpolation chain generation section 10, each time
The start and end of the stroke are detected from each signal Xi, Yi, and Zi at ti, and the continuation point of the stroke is detected from each sample point (X(i-1), Y(i-
1)), and an 8-connected chain sequence (interpolated chain sequence) is output from the interpolation grid points obtained by linear interpolation processing.

A method for quickly realizing the process of finding interpolated grid points from relative coordinates in this case will be described below.

First, as shown in Figure 5, the x coordinate of relative coordinates
By comparing the positive and negative signs of the dx and y coordinates dy and the magnitude of their absolute values, the relative coordinates (dx, dy) are classified into one of the eight octants shown in FIG. 4. From the relationships shown in Figures 4 and 5, relative coordinates belonging to octants other than the octant are projected onto the octant, and interpolation grid points and interpolation are performed for the relative coordinates (dx, dy) at that time. The chain is determined and finally back-projected onto each responding octant to determine the actual interpolation grid points and interpolation chain.

Next, a method for obtaining interpolated grid points and interpolated chain sequences from the relative coordinates of the octant will be described.

In general, if you examine the distribution of relative coordinates (difference between the previous sample point coordinate and the current sample point coordinate) when handwritten figures are sampled at about 30 Hz, most of them are within 16 dots in absolute value. Therefore, the relative coordinates (dx,
It is sufficient to store an interpolation chain of up to an absolute value of 16 as a table for dy).

Regarding the relative coordinates of the octant shown in FIG. 6, an interpolation chain table as shown in FIG. 8 is referred to. For example, (3, 2) as shown in Figure 7.
When the relative coordinates are given, the (3, 2) coordinates of the interpolation chain table in FIG. 8 are used to find the corresponding chain length and interpolation chain sequence. In other words, since chain length = 3, 2 stored in the table
Obtain the chain sequence {1, 0, 1} of the upper 3 bits in the interpolation chain sequence of bytes. The actual interpolation grid points are determined as shown in FIG. 7 based on the chain direction relationship shown in FIG. 4.

If the relative coordinates exceed the range of the table of the interpolation chain generator 10, as shown in FIG. In the explanation, the relative coordinates are divided by Lx = 16, Ly = 16), the intermediate point coordinate string is calculated, and from the obtained relay point coordinates, the distance between the sample point and the relay point, and between the relay points is calculated. The interpolation chain generation unit 10 calculates the difference coordinates of
generates an interpolation chain.

In Figure 9, after calculating the coordinates of one relay point T1, the generation of the interpolation chain between Pi and T1 is
The interpolation chain sequence is searched from the relative coordinates (dx1, dy1) with respect to Pi, and the interpolation chain generation process for the interval T1 to Pi+1 is performed by searching the interpolation chain sequence from the relative coordinates of Pi+1 with respect to T1 (dx2, dy2), and generating the interpolation chain. I'm trying to make it happen.

For the interpolation chain sequence generated in the interpolation chain generation section 10 in this way, the window chain generation section 11 generates M× as shown in FIG.
A window of size N is set, and when the interpolation chain train passes through the outer peripheral frame of the window, a window chain code corresponding to the passing position is generated. FIG. 10 shows a case where the window size is 5×7. In this case, there are a total of 20 peripheral points of the window, and therefore window chain codes in 20 directions are given. In the case of the figure, one window chain {3} is generated for the interpolation chain sequence {1, 2, 1} in eight directions.

In addition, at the end of the stroke, in the case of a 5x7 window, the window internal coordinates indicating the pen position at the end of the stroke are calculated from E0 to E0 as shown in Fig. 11.
Expressed with 15 types of E14 codes.

Then, the window chain sequence obtained by the window chain generating section 11 is subjected to the following encoding in the window chain encoding section 12 for data compression.

That is, a Huffman code corresponding to the appearance distribution of the differential window chain is assigned to the differential window chain, which is the difference between the window chain codes, and encoded. The absolute coordinates are encoded, and at the end of the stroke, an end code (En) indicating the end of the stroke and a window internal code (E0 to E14) are encoded with a fixed length of 4 bits.

The signal encoded by the window chain encoding section 12 is transmitted by the communication control section 5 to another handwritten figure transmission device through a line.

On the other hand, the handwritten figure data received by the communication control unit 5 is transmitted to the window chain decoding unit 14.
Three states are determined: the beginning of the stroke, the middle of the stroke, and the end of the stroke. At the beginning of the stroke, the absolute coordinates of the starting point are determined, and at the end of the stroke, the window internal code (E0 to E14) is displayed following the end code. In the middle of the stroke, it is decoded into a window chain sequence. In the window chain interpolation unit 13, the window chain obtained in the window chain generation unit 11 and the window chain decoding unit 14 is decomposed into eight-way chains. The window chain is decomposed into an 8-way chain with reference to the conversion table shown in FIG. 8 obtained in this window chain interpolation section 13
The directional chain sequence is written into the image storage section 6 as a handwritten graphic image, and its contents are displayed on the image display section 8.

In this embodiment, sample point coordinates sampled at a low speed of about 30 Hz are subjected to linear interpolation processing at high speed to generate an interpolation chain train in eight directions. It is not necessary, and an 8-connection chain can be reliably generated for any fast writing without adversely affecting the resolution. Furthermore, we set a window for the above interpolated chain string, converted it to a window chain string, and encoded the window chain obtained by this, so 8
The data compression rate is higher than that of a directional chain, and there is almost no transmission delay on the receiving side.

FIG. 13 shows another embodiment for generating an interpolation chain according to the present invention. In this embodiment, an interpolation chain is directly determined by only integer addition and subtraction according to the flow chart shown in the same figure. I have to.

The operation for generating an interpolation chain will be described below in accordance with this flowchart.

First, the octant is determined in step A, and then each relative coordinate is projected onto the first octant (step B), and then the following processing is performed.

Here, the formula (1) for interpolation chain generation is as follows: Formula (1) = 2*N*dy-(2*I+1)*dy dx, dy: relative coordinates I: integer value of Y coordinate (0, 1, ...) N: X coordinate value (1, 2, ..., N) This equation (1) is a straight line with slope dy/dx, that is, a straight line connecting two sample points and two interpolation grid points that sandwich this straight line. This is a formula for determining which interpolation grid point of the above two interpolation grid points the intersection with the straight line connecting I can do it.

First, as initial settings, N=1, I=0
(Step C), equation (1) is set to 0 (Step D), and the difference δ is calculated as δ=2*dy−dx (Step E).

Next, it is determined whether the X coordinate value N is greater than or equal to dx+1 (step F), and if it is less than dx+1, the process proceeds to the next interpolation chain generation step (steps G to P).
Moreover, if it is dx+1 or more, the coordinates are updated (step Q).

In the interpolation chain generation step, the value of equation (1) above plus the value of the difference δ is set as a new value of equation (1) (step G), and whether this value is positive or negative is determined (step H ). If this value is positive or 0, add 1 to the integer value I of the Y coordinate and the integer value N of the X coordinate (step J), and newly calculate the difference by 2.
*Reset to the value of (dy−dx) (step L),
Generate interpolation chain {1} (step N).

Furthermore, if the value of equation (1) obtained in step G above is negative, 1 is added only to the X coordinate value N (step I), and the difference is reset to a new value of 2*dy (step K), generate an interpolation chain {0} (step M).

Then, the interpolation chain {0} or {1} obtained in steps M and N is converted into an eight-way Freeman chain according to the octant value (steps O and P), and the process returns to step F. By repeating these operations, the relative coordinates (dx, dy) are decomposed into interpolation chain sequences.

The interpolation chain sequence thus obtained is encoded in the same manner as in the above embodiment.

In this embodiment, as in the above embodiment, an 8-connected interpolation chain can be reliably generated for any fast handwriting, and data can be compressed with high efficiency.

In the above embodiment, the interpolation chain generation section converts all interpolation chain sequences into Freeman's 8-direction chains and outputs them, and the window chain generation section applies a window to the 8-direction chain sequence. The interpolation chain generation section outputs the octant number, chain length, and intra-octant chain code (0 or 1) for each sample point without converting it to an 8-way chain, and the window chain generation section 12 directly converts the window chain from these. may be generated.

〔Effect of the invention〕

As described above, according to the present invention, instead of directly detecting an 8-connected chain, linear interpolation processing is performed on the relative coordinates between each sampling point obtained by sampling at a slower speed than in the past. This method generates an interpolated chain sequence using It is possible to reliably generate an 8-connected chain even for writing,
Furthermore, there is an effect that the data compression rate can be significantly increased during encoding.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional handwritten figure transmission device.
FIG. 2 is an explanatory diagram of an 8-connected chain, FIG. 3 is a configuration diagram of a handwritten figure transmission device according to an embodiment of the present invention, FIG. 4 is an explanatory diagram of octant numbers and chain codes within the octant, and FIG. Figure 6 is an explanatory diagram of the area where the interpolation chain table is prepared. Figure 7 is an example of relative coordinates, interpolation chain rows, and interpolation grid points. 8 is an explanatory diagram of the interpolation chain table, FIG. 9 is an explanatory diagram of the interpolation chain generation process when the relative coordinates exceed the range of the interpolation chain table, and FIG. 10 is an explanatory diagram of the interpolation chain generation process. FIG. 11 is an explanatory diagram of the window internal code used to end a stroke. FIG. 12 is a diagram showing a conversion table from the window chain to an eight-way freeman chain sequence. FIG. 7 is a diagram showing a flowchart for generating an interpolation chain according to another embodiment. 1... Coordinate detection section, 2... A/D conversion section, 10
. . . Interpolation chain generation section, 11 . . . Window chain generation section, 12 . . . Window chain encoding section. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A handwritten figure transmission device that encodes and transmits the sample point coordinates of a handwritten figure input from a tablet with a pen, comprising a coordinate detection unit that detects the coordinates indicated by the pen and the up/down state of the pen; An A/D conversion section samples the pen position coordinates obtained in the coordinate detection section at a constant cycle; an interpolation chain generation unit that generates an interpolation chain sequence by linear interpolation processing that calculates relative coordinates between a sample point and the sample point immediately before it and decomposes the relative coordinates into interpolation chains of size 1 connecting interpolation grid points; M× for the interpolation chain sequence from the interpolation chain generation unit
A window chain generation unit that sets a window consisting of N interpolation grid points and generates a window chain corresponding to the passing position when the interpolation chain train passes through the outer peripheral frame of the window; A handwritten figure transmission device comprising: a window chain encoding unit that encodes a window chain string for data compression.