JPH0347532B2 - - 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 in order to obtain an 8-connected chain figure, and 4 calculates a difference with respect to the 8-direction chain array obtained by the chain detection unit 3 to generate a differential chain array. 5 is a differential chain encoding unit that performs encoding for data compression on the differential chain sequence obtained by the differential chain calculating unit 4; 6 is a communication control unit that performs line communication control; Reference numeral 7 denotes a differential chain decoding unit that decodes the handwritten figure signal received by the communication control unit 6 into an 8-connected chain string, and 8 indicates a video memory, for example, that stores the handwritten figure or the received figure as a dot image. 9 is an image display section such as a CRT display for displaying the contents of the image storage section 8, and 10 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 position coordinates at a constant cycle, and obtains the position coordinate signals Xi, 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, the X coordinate, Y coordinate at each sampling time ti,
Changes in coordinates are monitored by the chain detection section 3, and the second
When a displacement of magnitude 1 occurs as shown in the figure, the displacement becomes an 8-direction freeman chain of magnitude 1 (0
~7 code). This 8-direction Freeman chain code is based on the direction of the line segment connecting the center position A0 and each grid point A1 to A8 whose absolute value of the relative coordinate of X or Y with respect to this center position A0 is 1. It is determined. Then, the difference chain calculation section 4 calculates the difference between the chains,
A differential chain sequence is output.

Based on the results of the differential chain calculating section 4, the differential chain encoding section 5 encodes the freeman chain code as it is for the chain immediately after the start of the stroke, as shown in FIG. As for the columns, each differential chain is encoded by assigning a Huffman code based on the probability of occurrence of the differential chain as shown in FIG. For example, if the differential chain encoding format is D
In the case of 1, the code length is 3 bits “0, 0, 0”
Assign. At the end of the stroke, an end symbol (En) is assigned and encoded. Furthermore, at the start of a stroke, the starting point coordinates are encoded as absolute coordinates. The communication control unit 6 converts the data encoded by the differential chain encoding unit 5 to the line 1.
Performs communication control for transmission or reception through 0.

Further, the data related to the handwritten figure received by the communication control section 6 is decoded by the differential chain decoding section 7, and expanded into an 8-direction Freeman chain sequence. An image storage unit 8 such as a video memory stores an 8-direction freeman chain sequence related to an input or received handwritten figure as a dot image, and based on this, a handwritten figure image is displayed on an image display unit 9 such as a CRT display. .

Since the conventional handwritten figure transmission device is configured as described above, the data compression rate for the chain train is not sufficient, and when transmitting data at a low transmission rate of about 300 bits/second, it is difficult to handle fast handwriting. However, the disadvantage was that there was a significant transmission delay 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 assigning a Huffman code to a differential chain sequence based on the probability of occurrence of the differential chain, Classify into multiple groups based on the value, and for each difference chain, classify the immediately preceding difference chain into a predetermined number of groups, and use a Huffman code determined in advance for each group based on the probability of appearance. The object of the present invention is to provide a handwritten figure transmission device that can realize transmission by highly efficient encoding.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 5 shows 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; 2 is the coordinate detection unit 3 is an A/D conversion section which A/D converts and samples the position coordinate signals X and Y obtained in section 1, and also samples the up/down signal Z of the pen at the position coordinates; X coordinates Xi and Y at each time ti obtained by the D converter 2
A chain detection unit monitors changes in the coordinate Yi and detects an 8-direction Freeman chain of size 1 in order to obtain an 8-connected chain figure. and a differential chain calculation unit 11 that calculates and generates a differential chain sequence, and 11 is a differential chain classification unit that classifies each differential chain into a plurality of groups according to its value for the differential chain sequence obtained in the differential chain calculation unit 4. Section 12 is differential chain classification coding for encoding each differential chain by assigning a Huffman code prepared separately for each group to which the immediately preceding differential chain belongs, based on the results of the differential chain classification section 11. Department. Then, the differential chain encoding means 2 is processed by the differential chain classification section 11 and the differential chain classification code section 12.
0 is configured.

6 is a communication control unit that performs overall communication control for transmitting or receiving data through the line 10; 13 is a communication control unit that performs the previous differential chain that has already been decoded for the handwritten figure signal received by the communication control unit 6; a differential chain classification decoding unit for classifying by value, finding the next differential chain from the corresponding code table, and finally converting the handwritten figure signal into a Freeman chain sequence in eight directions;
9 is an image storage unit that stores the 8-direction freeman chain sequence related to the input or received handwritten figure as an image; 9 is an image display unit that displays the handwritten figure image stored in this image storage unit 8; and 10 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 at a predetermined sampling frequency are input into the coordinate detection section 1, these signals are converted into quantum signals at the A/D conversion section 2. and converted into discrete values. Next, in order to obtain an 8-connected chain figure,
Changes in the coordinates Xi and Y coordinates Yi are monitored by the chain detection unit 3, and when a change of magnitude 1 as shown in FIG. code). Then, the difference chain calculation section 4 calculates the difference between the chains, and outputs a difference chain sequence. Each of these differential chains is divided into differential chain classification section 1
1, they are classified into a plurality of groups as shown in FIG. 6 according to their values. This Figure 6 shows the case of classification into two groups A and B, where the values of each differential chain are -1, 0, 1.
Types of times are group A, other times are group B
It is said that Generally speaking, considering the tendency of difference chains to appear, in the case of relatively smooth pen movement, the difference chains often consist of 0, +1, and -1 in a concentrated sequence. On the other hand, in the case of sudden pen movements or complicated pen movements, the values of the differential chain sequence do not concentrate much on specific values. By classifying these two states and applying a Huffman code obtained from the appearance probability to each state, more efficient encoding can be achieved than in the conventional case where the value of the immediately preceding chain is not considered. You can expect it. The differential chain classification encoding section 12 classifies each differential chain according to the group of the immediately preceding differential chain, as shown in FIG. Then, encoding is performed using a separately prepared Huffman code table. This Huffman code table is shown in FIG. 8, and is set based on the appearance distribution of the group to which the differential chain belongs. For example, if the differential chain classification encoding format is DA2, that is, the differential chain to be encoded is “2”, and the immediately preceding differential chain (“0”) group is A,
A 6-bit code "001000" is assigned to the differential chain "2". In addition, at the start point of a stroke, the start point coordinates are encoded as absolute coordinates, and for the first Freeman chain following it, a Huffman code based on the appearance distribution of Freeman chains is directly assigned, and at the end of the stroke, the end symbol En
encode. The data encoded in this manner is sent to the line 10 through the communication control section 6.

On the other hand, from the other party's handwritten figure transmission device to line 10
The handwritten figure data sent through the communication control unit 6 is sent to the differential chain classification decoding unit 13.
is input. In the differential chain classification decoding unit 13, the starting point coordinates are obtained from the absolute coordinates for the beginning of the stroke, and the next chain data is decoded using the Huffman code shown in FIG. 4 as a "Freeman chain". It will be done. The subsequent data is divided into several groups (two groups in Figure 6) as in the case of the above encoding, as shown in Figure 6, according to the value of the immediately preceding difference chain as a "difference chain." Classification)
Decoding is performed using Huffman codes for each group. That is, as shown in FIG. 7, an 8-direction chain array is obtained conversely from the obtained differential chain array.

The image storage unit 8 stores the Freeman chain sequence of size 1 obtained by the chain detection unit 3 or the chain sequence obtained by the differential chain classification decoding unit 13 as a handwritten figure, and the contents are displayed on the image display unit 9. Is displayed.

In this embodiment, for each differential chain in the differential chain sequence, the immediately preceding differential chain is classified into a predetermined number of groups.
Since each group is encoded using a Huffman code that is determined in advance based on the probability of occurrence, a higher data compression rate can be obtained and lower transmission There is no longer any transmission delay for the bit rate on the receiving side.

In the above embodiment, a case has been described in which Freeman chains are directly detected sequentially in the chain detection section, but the basic principle of the present invention is to roughly obtain sample points even at a lower sampling frequency than in the above embodiment, and Of course, the present invention can also be applied to a case where a chain train is generated by performing linear interpolation processing between points.

Further, in the above embodiment, a case has been described in which the value of the immediately preceding difference chain is divided into two groups, but the compression effect can be improved by increasing the number of groups to be classified. For example, as shown in FIGS. 9a and 9b, the values of each differential chain may be classified into three or four groups, and a different Huffman code may be used for each group. .

Furthermore, the previous differential chain code (-3 to 4)
The difference chain may be encoded by classifying the eight types into separate groups.

Increasing the number of groups to classify will improve the compression effect, but the codes to be stored and the encoding/decoding process will become more complicated. All you have to do is decide.

〔Effect of the invention〕

As described above, according to the present invention, for the difference chains of the obtained Freeman chain sequence, each difference chain is classified into a plurality of groups according to its value, and each difference chain is classified into a plurality of groups based on the difference chain immediately before it. Since encoding is performed using a Huffman code prepared separately for each group according to the group to which it belongs, there is an effect that transmission by highly efficient encoding can be realized compared to the conventional method.

[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 an explanatory diagram of differential chain encoding, FIG. 4 is a diagram showing an example of a Huffman code table for a freeman chain and a differential chain, and FIG. FIG. 6 is an explanatory diagram of classification of differential chains, FIG. 7 is an explanatory diagram of differential chain classification encoding, and FIG. 8 is an example of a Huffman code table for classified differential chains. The figure shown in FIG. 9 is an explanatory diagram showing another example of classification of differential chains. 1... Coordinate detection section, 2... A/D conversion section, 3...
...Chain detection unit, 4...Difference chain calculation unit,
20...Differential chain encoding means. 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 converter that samples and A/D-converts the coordinate signal regarding the pen position obtained in the coordinate detector at a constant cycle; and a coordinate signal of the pen at each sample point obtained in the A/D converter. Size 1 of 8 from the pen's up/down signal
a chain detection unit that detects a directional Freeman chain; a difference chain calculation unit that calculates a differential chain from the 8-direction Freeman chain code detected in the chain detection unit; A handwritten handwritten item characterized by comprising a differential chain encoding means for classifying the immediately preceding differential chain into a predetermined number of groups and encoding each group using a Huffman code determined in advance based on the probability of occurrence. Graphic transmission device.