JPH0440746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for performing smoothing processing on a sequence of sample points and displaying the same in a system for inputting, transmitting, and displaying drawn images such as handwritten characters and figures.

First, a conventional device will be explained.

In FIG. 1, in a communication system in which a drawn image such as handwritten characters or figures is inputted to a transmitting device 101, a drawn image signal is transmitted online to a receiving device 102, and the drawn image is displayed on a display device 7. A drawing image signal output from a position coordinate detector 1 such as a tablet is sampled at a constant time rate (approximately 40 to 120 Hz) by a sampling device 2, and this coordinate information is encoded by an encoder 3. Convert and transmit
This coordinate information is compounded by a compounder 4, reproduced by linear interpolation using a linear generator 5, stored in an image memory 6, and displayed on a display device 7.

Furthermore, in order to reduce the amount of code to be transmitted, encoder 3 encodes only the coordinates of the first sample point when the coordinates of temporally consecutive sample points are the same; A method of ignoring the sample points is used (see references).

This situation is shown in FIG.

When time t is taken such that the sampling period is 1, x(t) and y(t) are the time waveforms of the x and y coordinate component signals when the curve C ₀ is input. The coordinate signal output by sampler 2 is
Q _t (X _t , y _t ) (t=1, 2...).

Although FIG. 2 shows an example in which X _t and y t are quantized by rounding down x(t) and y( _t ) to integer values, they may be rounded off or the like.

Furthermore, the encoded sample points output from the encoder 3 (hereinafter, the sample points output from the encoder 3 will be referred to as encoded sample points to distinguish them from the sample points output from the sampling device 2) are Q ₁ and Q ₆ marked with ● in Figure 2
...becomes.

On the other hand, FIG. 3 shows the positions of sample points on the xy plane. It can be seen that where the drawing speed is slow, the sample points are connected, and conversely, where the drawing speed is fast, they are discrete.

In such a system, the receiving device 102
When the resolution of the coordinates exceeds that of the transmitter 101, or when the resolution of the coordinates to be transmitted is lowered to reduce the amount of transmitted codes (see references), the receiver 102 uses the following device to display Was.

That is, the coordinates of the received sample point are transmitted to the receiving device 102.
, and an appropriate interpolation process (generally, a simple linear interpolation process is used) between the converted sample points is displayed.

We will discuss the problems when using this display processing. When the drawing input speed was high and the sampling point interval was large, the display quality did not deteriorate significantly even under the above conditions (see reference). However, when the drawing input speed is low and the sample point interval is small (in the example in Figure 3, near Q ₁ , Q ₆ , Q ₈ , and Q ₉ ), the display may be distorted, such as diagonal lines appearing as broken lines on stairs. There was a deterioration in quality, especially a lack of smoothness.

Figure 4 shows a schematic diagram when linear interpolation is performed and displayed at the sampling resolution, where P ₁ to P ₆ are the sampling points of the input curve C ₁ , and P ₁ ′ to _{P 6} ′ are the input points. curve
This is the point where C ₂ was sampled, and the point indicated by ⓓ is the point interpolated using the straight line generation algorithm. In FIG. 3, the input curve C ₁ has a high drawing input speed and therefore has a large sample point interval, but the input curve C ₂ has a small drawing input speed and therefore has a small sample point interval and is in a connected state.

FIG. 5 shows a case where the display resolution is doubled relative to the input (transmission) resolution and linear interpolation is performed with the precision of the display resolution. The input curve C ₂ has sample points that are not connected even during input, so by increasing the display resolution, it is interpolated more smoothly than when the input and display resolutions are equal (Figure 4). I understand.

On the other hand, the input curve C ₂ is displayed on a staircase rather than when the display resolution is large (Fig. 5) than when the input/display resolutions are equal (Fig. 4).
It can be seen that the deterioration in display quality due to low input resolution is noticeable.

As described above, when display processing is performed by the conventional method when the display resolution is larger than the input resolution, there is a drawback that deterioration becomes noticeable when the drawing speed is slow. Therefore, this drawback can be eliminated by inserting a simple low-pass filter (LPF) based on the time axis between the sampling device 2 and the encoder 3, or between the decoder 4 and the linear generation circuit 5. Can not do it.

Also, even if you improve the interpolation algorithm (for example, change from simple linear interpolation to curved interpolation) without changing the coordinate values of sample point _P1 , the input curve
In cases like C ₂ , it is displayed as a staircase (wavy line),
There is no difference in the lack of smoothness.

In order to eliminate these drawbacks, the present invention uses the sample point coordinates output from the compound device 4 to perform smoothing processing with the accuracy of the display resolution, and will be described in detail below with reference to the drawings. do.

In order to remove the above-mentioned deterioration and display a drawn image smoothly, it is effective to perform smoothing processing after adaptively compressing the time axis according to the drawing speed.

Therefore, for the encoded sample points that are connected by the encoder 3 and remove the sample points existing at the same coordinates, the absolute time interval is ignored, and the encoded sample point sequence is
It is assumed that the number i assigned to P _i (i=1, 2, . . . ) is a new time axis, and the smoothing process is performed based on that time axis.

FIG. 6 is a block diagram showing the configuration of an embodiment of the present invention, in which a display processing circuit 8 is added to the conventional image communication device shown in FIG. here,
Taking the original signal shown in FIG. 2 as an example, the x and y coordinate values of the encoded sample points input to the display processing circuit 8 are as shown in FIG. It can be seen that it is compressed. For the encoded sample point sequence {P _i } with the time axis adaptively compressed in this way, if P ₁ is the point P N immediately after pen-down is the point P _N is pen-up, then ``P^ ₁ = P ₁ P^ _i =P _i-1 +2P _i +P _i+1 )/4 P^ _N =P _N (Formula 1) However, the smoothing process of (2≦i≦N-1) is performed, and the point sequence that has been smoothed is {P _i } is subjected to linear interpolation and displayed.

Here, it is assumed that this smoothing process is performed with an accuracy equal to or higher than the display resolution.

FIG. 8 shows a schematic diagram of the sample points shown in FIG. 4 displayed after performing the above smoothing process on a display surface having _{twice the} resolution _. ˜P ₆ ′ are sample points after each smoothing process is performed.

In this way, the display processing circuit 8 performs the smoothing process on the encoded sample points, and then performs linear interpolation, thereby displaying a screen smoothed in accordance with the display resolution. In particular, when the encoding sampling changes stepwise (as mentioned above, the drawing speed is often slow) like curve C ₂ shown in Figure 5, the displayed curve can be almost completely smoothed. can.

Furthermore, as can be seen from FIG. 8, although this smoothing process does not correctly reproduce the coordinates of the encoded sample points received by the receiving device 201, the absolute position of drawing information such as characters is Since the apparent smoothness is more important than the coordinates, it is not a big problem that the coordinates of the encoded sample points are not correctly reproduced.

As explained above, by using a combination of selective removal of sample points by the encoder 3 and fixed smoothing processing by the smoothing processing circuit 8, the overall characteristics of the input drawn image signal can be improved. This has the advantage that smoothing processing that changes adaptively can be performed.

Further, the smoothing process used in the present invention is very simple, and can be calculated by using three given sample points, regardless of the sample points and the algorithm for interpolating the sample points. Note that since the denominator of division in Equation 1 is 4, operations can be performed by bit shifting when using a microcomputer, and operations can be performed by extracting only the upper bits when using wired logic. This has the advantage of simplifying the configuration.

Furthermore, by performing smoothing processing, when communicating between devices having display screens with different resolutions, it is possible to effectively utilize the resolution of the receiving device 102 by simply performing display processing on the receiving device 102.
Moreover, there is an advantage that the amount of transmitted codes does not increase.

Note that even if noise is superimposed on the drawn image signal in the transmitter 101, the noise removal effect can be obtained by applying this display processing method. In that case, the resolution of the display need not exceed the resolution of the input.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the configuration of a conventional image communication device, Figure 2 is a schematic diagram showing the relationship between image signals and sample points, and Figure 3 is a diagram showing the relationship between sample points on the x-y plane. A diagram showing the position, Figure 4 is a schematic diagram when linear interpolation is performed and displayed at the sampling resolution, Figure 5 is a schematic diagram when the display resolution is doubled, and Figure 6 is an embodiment of the present invention. FIG. 7 is a schematic diagram showing the x and y coordinates of encoded sample points output from the encoder, and FIG. 8 is a schematic diagram showing the case where smoothing processing is performed. 1... Coordinate detector, 2... Sampling device, 3...
Encoder, 4... Decoder, 5... Straight line generation circuit, 6
... Image memory, 7 ... Display device, 8 ... Display processing circuit, 101 ... Transmission device, 102 ... Receiving device, C ₀ , C ₁ , C ₂ ... Input curve, Q ₁ to Q ₂₀ ... Sample points, P ₁ to P ₆ , P ₁ ′ to _{P 6} ′... (encoded) sample points,
P ₁ to _{P 6} , P ₁ ′ to _{P 6} ′... Sample points subjected to smoothing processing.

Claims (1)

[Claims] 1. In a method for inputting, transmitting, and displaying drawn images such as handwritten characters and figures, the transmitting side samples the position coordinates of the drawn image at fixed time intervals and uses the sampled input. If the position coordinates of the points are consecutively the same, the points are sent as a position coordinate point sequence, excluding duplicates, and the receiving side performs smoothing processing on the received position coordinate point sequence, and then A display processing method for a drawn image signal, characterized in that a new position coordinate point sequence obtained by smoothing processing is made to correspond to the display resolution of a display device, and a straight line is interpolated between two consecutive points. 2 The smoothing process is performed using the following formula: ``P^ ₁ =P ₁ P^ _i =P _i-1 +2P _i +P _i+1 )/4 P^ _N =P _N , where 2≦i≦N-1 , P ₁ and P _N are the pen-down point and pen-up point for the point sequence {P _i }, P ₁ ,
P ₁ and P _N are the points of the point sequence {P _i } that have been smoothed. A display processing method for a drawn image signal according to claim 1, characterized in that the method uses: