JPH0246068A - Picture data compressing system and facsimile equipment applying same - Google Patents

Abstract

PURPOSE:To reduce a data transmitting quantity on transmitting picture data by encoding and transmitting the direction changing quantity of the direction of a picture element changing edge in a picture element changing point on an remarked scanning line and the direction of the picture element changing edge in the picture element changing point of the picture element changing edge on a reference scanning line. CONSTITUTION:Picture data on an MR-encoded remarked scanning line are supplied to a register 41 of a first stage of an FIFO buffer 4 constituted of a direction changing code generating circuit 3 and registers 41 and 42 of 2 stages. In the direction changing code generating circuit 3, a code column on the remarked scanning line supplied from an MR encoding circuit 2 and the code column on a reference scanning line supplied from the register 42 of the second stage are compared, a shearing quantity (n) of corresponding vertical codes V(O), VR(m) and VL(m) is found, an obtained value is substituted by direction changing codes D(O), DR(n) and DL(n), and a direction changing signal is generated and is transmitted on other horizontal codes as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image data compression method for compressing the amount of data to be transmitted when transmitting characters, patterns, etc., and a facsimile device to which this method is applied.

Table 1 [Prior Art] MR (Modified ROM) code is used as a standard two-dimensional data compression method in facsimile, and the case where this is used to encode the figure "A" shown in Fig. 2 is given as an example. Let me explain briefly.

This figure 2 shows as an example a screen consisting of X = 16 pixels on the horizontal axis and 11 pixels on the vertical axis, and further to the right of the rightmost column X = 16 of this screen, as shown with diagonal lines, , assumes a column formed of all black pixels.

The pattern "A" is developed as a figure on this screen, and the MR codes obtained by scanning this screen in the horizontal axis direction are shown in Table 1 below.

This MR code is basically a vertical code, and the amount of deviation in the X-axis address of the pixel change point from white to black or black to white between the previous scanning line and the following scanning line of interest (scanning line being processed). The value m (m≦3) in parentheses above indicates this amount of deviation, so v(0) indicates that there is no deviation, and VR(m) and VL(m ) indicates that the direction of the shift is to the right or left.

■] indicates that a horizontal code (MH code) is applied, and when the amount of deviation is greater than 3 or when a new pair of white-black or black-white pixel change points occurs. W in this MH code
(p) and B (p) indicate that p pixels are consecutively white or black, respectively, and P indicates that two codes forming a pair are to be erased.

The numbers shown in the number of bits column in Table 1 above indicate the total number of bits of the code strings shown in the middle column, and Table 2 below shows the codes corresponding to the codes and their bit numbers. showed that.

The second and third terms of the MH code in the upper table of Table 2 are codes of the MH code indicating the number of consecutive white or black pixels.

[Problem to be solved by the invention]

In general graphics, pixel change points often have a continuous X-axis address shift amount of a constant value. For example, in the case of pattern "A" shown in Figure 2, the shift amount is O
2±1, and the deviation of the same value, such as ±1, continues between many scanning lines.

However, when transmitting a vertical code such as the above-mentioned MR code, that is, the difference between the X-axis address of the pixel change edge at the pixel change point on the scan line of interest and the X-axis address of this pixel change edge on the reference scan line, , it is necessary to transmit two data indicating the value of the difference in addresses and its direction.

An object of the present invention is to reduce the amount of data transmitted when transmitting image data by utilizing the above-mentioned characteristics of graphics.

[Means to solve problems]

Encodes the amount of direction change between the direction of the pixel change edge at the pixel change point on the scanning line of interest and the direction of the pixel change edge at the pixel change point of this pixel change edge on the reference scan line, and transmits this as a direction change code. I did it like that.

Then, as the direction change sign when there is no direction change, MR
V (0) sign indicating that there is no vertical sign shift, and M as the direction change sign when there is a direction change of ±n.
VR(n) sign and VL(
n) Codes can be reused.

To obtain this direction change sign, M in the reference scan line is
The difference between the R vertical code and the corresponding MR vertical code in the scan line of interest can be encoded as a direction change ■.

In order to apply the present invention to transmission in a facsimile machine, a direction in which a change in an MR vertical code in an MR code string of a scanning line of interest and an MR vertical code in an MR code string of a reference scanning line is encoded as a direction change code. A change code generation circuit is provided and configured to replace the MR vertical code in the MR code string of the scanning line of interest with this direction change code and send it out as a direction change code signal.

In addition, in order to apply to reception, an MR that decodes an MR vertical code from a direction change code in a direction change code signal of a reference scanning line and a direction change code in a direction change code signal of a scanning line of interest.
A code decoding circuit may be provided to replace the direction change code in the direction change code signal for the scanning line of interest with the MR vertical code, thereby converting it into an MR code string.

[For production]

As is clear from the example of FIG. 2, the amount of deviation between adjacent scanning lines at pixel change points in characters/patterns is often a constant value. In the case of kanji, which are more complex and have more strokes than alphanumeric characters, the reduction in data volume is even more remarkable.

In the present invention, the direction of the pixel change edge at the pixel change point on the scan line of interest and the direction of this pixel change edge on the reference scan line are determined.
By encoding and transmitting the amount of change in direction from the direction of the pixel change edge at the pixel change point of F, the amount of information to be transmitted can be reduced.

Furthermore, the amount of transmitted data can be further reduced by assigning a code with the minimum number of bits of the code to be transmitted as a code when the amount of deviation between adjacent scanning lines at pixel change points is equal as described above.

FIG. 1 shows the direction change information required when transmitting the pattern "A" shown in FIG. 2 by applying the image data compression method according to the present invention, using arrows, and pixel changes shown by thick lines. If the direction of the edge on the reference scan line is different from the direction of this changed edge on the scan line of interest, it is necessary to transmit direction change information corresponding to the arrow shown by the solid line. If there is no change in the direction of the edge, that is, for the pixel indicated by the dotted arrow, it is sufficient to transmit information indicating that there is no change in the edge direction, for example, the D(0) code to which the shortest code length is assigned, which will be described later. , MR vertical code, there is no need to transmit data indicating two types of information: the difference value of the X-axis address of the pixel change edge and its direction.

An example of image data for the "A" pattern of FIG. 2 compressed according to the present invention is shown in Table 3 below.

3 shows the number of bits when each of the displayed codes is replaced with the direction change code of the present invention as described above.

The total number of bits is 85, and when compared with the total bit number 8102 in Table 1, it is 102/85-1.2, resulting in a 20% improvement in transmission efficiency.

By the way, the compression efficiency is (16x, 11)/85=2.
1 and (16x 11)/10 for MR code
The compression efficiency is significantly increased compared to 2=1.73.

Here, "■" in the MR vertical code is shown as "D" to indicate that it is a direction change code according to the present invention, but v(0) in the MR vertical code shown in Table 2 is ), and VR(m), VL(w+
) can be used as the code for OR(m) and DL(m), respectively, and Table 2 shows the bit number column in the above table. An example of a facsimile machine to which this is applied will be described.

FIG. 3 is a block diagram of an embodiment on the transmitting side in which a facsimile machine equipped with an MR code output is provided with an input device for obtaining a direction change code according to the present invention.

Similar to a conventional facsimile machine, an image is read by a scanner l, and an MR encoding circuit 2 performs MR encoding on the obtained image signal.

The MR-encoded image data for the scanning line of interest is stored in the direction change code generation circuit 3 and the two-stage register 41.
The signal is supplied to the first stage register 4 of the FIFO bus register 4 configured by 4□.

1 in the first stage register 4 of this FIFO buffer 4
When the code string of the th scanning line is supplied from the MR encoding circuit 2, the code corresponding to v(0) is stored in advance in this first stage register 41 as an initial value. The first 1tII value v(0) is stored in register 4 of the second stage.
□, and the image data of the second and subsequent scanning lines of interest are transferred to the first stage register 4. , the code string of the previous scanning line, that is, the reference scanning line, is transferred to the second stage register 42.

In the direction change code generation circuit 3, as described above, MR
The code string for the scanning line of interest supplied from the encoding circuit 2 is compared with the code string for the reference scanning line supplied from the second stage register 4□, and the corresponding vertical code V (0
), VR (m), VL (m) (7) Calculate the amount of deviation (n), and obtain the obtained value, that is, the direction change sign (0), OR (n), DL, which corresponds to the amount of direction change.
(n), and generate and send out a direction change signal while leaving the other horizontal codes as they are.

FIG. 4 shows the configuration of an embodiment of the receiving side of the facsimile machine, in which the received direction change signal is sent from the receiving circuit 11 to the receiving side of the facsimile machine.
M
It is converted into an R code signal. Is this conversion also Ml? Vertical code V
(0), VR(n), and VL(n) with direction change sign D (
0), OR(m), and OL(m).

The MR code signal thus obtained is stored in the register 13, used as a reference code string for decoding the direction conversion signal of the next scanning line, and is outputted as a facsimile image by, for example, a plotter.

In the embodiment shown in FIGS. 3 and 4, a FIFO buffer 4 and a direction change code generation circuit 3 are provided on the transmitting side of a facsimile apparatus using conventional MR codes, and an MR code decoding circuit 12 and a register are provided on the receiving side. By adding 13 to each, it is possible to send and receive direction change signals, and by making such slight additions and modifications to facsimile machines that use conventional MR codes, the present invention can achieve a highly efficient transmission system. can be used.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an image data compression method with high compression efficiency by utilizing the fact that the amount of deviation between adjacent scanning lines at pixel change points in characters/patterns is often a constant value. In the case of kanji with a large number of strokes, compression efficiency can be further increased.

Further, by adding some components, a special effect can be achieved in that a facsimile apparatus to which the image data compression method according to the present invention is applied can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram for explaining the principle of data compression according to the present invention, Fig. 2 is an example of figures used for explanation, and Fig. 3 is a diagram of the transmitting side of a facsimile machine to which the data compression method according to the present invention is applied. Block Diagram Showing Embodiment FIG. 4 is a block diagram showing an embodiment of the receiving side of the facsimile machine. 3... Direction change code generation circuit, 4... MR code decoding circuit.

Claims (5)

[Claims] (1) Encode the amount of direction change between the direction of the pixel change edge at the pixel change point on the scanning line of interest and the direction of the pixel change edge at the pixel change point of this pixel change edge on the reference scan line, and convert this into a direction change code. An image data compression method characterized in that the image data is transmitted as . (2) V(0) sign indicating that there is no deviation of the MR vertical sign as the direction change sign when there is no direction change, and
VR(n) sign and VL(n) which indicate the amount of deviation of the MR vertical code as the direction change sign when there is a direction change of ±n
An image data compression method characterized by using codes. (3) The difference between the MR vertical code in the reference scanning line and the corresponding MR vertical code in the scanning line of interest is encoded as a direction change amount, and this is transmitted as the direction change code. Image data compression method described in 2. (4) A direction change code generation circuit that encodes a change in the MR vertical code in the MR code string of the scanning line of interest and the MR vertical code in the MR code string of the reference scanning line as a direction change code; A facsimile apparatus characterized in that the MR vertical code in the MR code string is replaced with this direction change code and transmitted as a direction change code signal. (5) An MR code decoding circuit that decodes an MR vertical code from a direction change code in a direction change code signal of a reference scanning line and a direction change code in a direction change code signal of a scanning line of interest; A facsimile apparatus characterized in that a direction change code in a direction change code signal is converted into an MR code string by replacing the direction change code with an MR vertical code.