JPS5854778A - Automatic linear density switching control method for two-dimensional encoding facsimile equipment - Google Patents

Abstract

PURPOSE:To perform high speed and sharp facsimile transmission, by counting a vertical mode code relating to coding line, comparing it with a reference value and switching the sub-scanning line density through the result. CONSTITUTION:If a pulse of a data line located under a pulse of a reference line encoded just before a present coding line is shifted right or left by n-picture element, the vertical mode code of a VLn or VRn is given and when no shift of picture element is given, the code of V0 is given. In the codes VL and VR, the picture image is changing, then the processing of higher resolution in comparison with that of the V0 is done, the VL and VR only are counted to obtain data for the decision of density. The scanning data from a transmission scanning section 16 instructs the changeover of reading through the coding number counter of the vertical mode code VL/VR and the density deciding function in a data compressing section 17, depending whether the line density is the high resolution or the standard resolution. A data restoration section 18 at the reception side instructs the changeover of recording through the decision of density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an automatic line density switching control system in which the sub-scanning line density is automatically switched in order to change the resolution according to the density of an image in a two-dimensional encoding type facsimile machine. In particular, in facsimile machines to which the two-dimensional encoding system of 0OITT Recommendations T and 4 is applied, an automatic line density switching control method is known that performs coarseness/density determination based on the number of vertical mode encodings.

When transmitting facsimile images, one method for achieving high-quality and high-speed transmission is to switch the sub-scanning line density according to the density of the image, and use standard resolution,
There is a variable linear density switching method that reads/records at high resolution in dense areas.

This method counts the points at which white or black pixels change within a certain range, determines density, and switches the sub-scanning line density for reading or recording the next line.

This conventional method requires an image information change point counter to be provided separately from the image information compressor/decompressor. Also,
Since the number of change points within a certain range on each line is used as the criterion for line density switching, even if the currently encoded line has little change visually compared to the line immediately before it, the number of change points is large. Since the density is judged and scanning is performed at a high resolution linear density, this has an adverse effect on the transmission time, which poses a problem.

The present invention aims to solve the above-mentioned problems, and therefore, when compressing or decompressing an image signal in a two-dimensional encoding facsimile machine, it is necessary to Vertical mode code L
and VR, and compare the counted value with a predetermined reference value, and if the counted value is larger than the reference value, it is considered dense, and on the other hand, the counted value is smaller than the reference value. In this case, the density of the image is determined to be coarse or coarse, and the sub-scanning line density is switched intermittently in order to change the resolution based on the determination result.

First, a conventional linear density automatic switching control system will be briefly explained.

FIGS. 1(a) and 1(1)) are schematic configuration diagrams of an automatic selection method in the conventional method.

FIG. 1(a) shows a transmitter section, in which a read data signal of a facsimile transmission image read by a read controller 1 is given to a data compressor 2 and a change point calculator 3.

The data compressor 2 encodes the data according to a predetermined data compression method and sends it to the line via the modem 4. On the other hand, the change point counter 3 counts the number of change points in the read data, and when the change point count value in a certain range of the main scanning line is larger than a predetermined reference value, the 1III image being read has a fine change. When it is determined that the line density is the same, the line density switch 5 outputs a line density instruction signal to the reading controller 1 to reduce the feed width of the sub-scanning line. The linear density counter 3 is connected to the data compressor 2
It is composed of an asynchronous counter, etc., which operates completely independently of the input pulse, and is triggered at the leading or trailing edge of the input pulse. The counter 3 is of such construction that it produces an output signal when a reference count value is reached within a certain time period related to the main scanning time, and is cleared otherwise. Then the first
Figure (1)) shows the receiver section. A facsimile signal received via the modem 6 is restored to the original image information signal by a data restorer 7. This restored signal corresponds to the read data signal output from the read controller 1 in FIG. 2(a). Based on this restoration signal, the change point counter 8 and the linear density switch 9 operate in exactly the same way as in the case of -F arrangement (a), send a linear density instruction signal to the recording controller 10, and The original image can be reproduced by controlling the switching of the images.

As described above, in the conventional system, it was necessary to provide a dedicated change point counter for both transmission and reception.

Next, the present invention will be explained in detail.

The present invention utilizes two-dimensional encoding (
By using the Modified Read (Modified Read) method, the above-mentioned drawbacks of the conventional method can be improved and faster and clearer facsimile image transmission can be realized.

Recommendation T. The two-dimensional encoding method according to No. 4 refers to the position of each changed pixel on the currently encoded line with reference to the position of the corresponding reference pixel on the encoded line or the reference line immediately before the encoded line. This is a sequential encoding method. After encoding a coded line, the coded line is used as a reference line for the next coded line.

However, in order to prevent the spread of the part disturbed by transmission errors, the maximum T (
- Two-dimensionally encode one line, insert a one-dimensionally encoded line again, and continue the two-dimensionally encoded line. Here, K is called a parameter.

Furthermore, there are three encoding modes: vertical mode, pass mode, and horizontal mode, and encoding procedures and the like for each mode are defined. Among these, the vertical mode is one in which the relative distance between the change point to be encoded on the encoding line and the corresponding change point on the reference line is within O~3 pixels; When the change point is to the right of the change point on the reference line (Va) and when it is to the left (Vr,)
, a case of no displacement (Vo), and 1 to 3 depending on relative displacement, a total of seven types of encoding modes are defined.

The present invention was made based on the fact that when an image changes continuously over each line, this vertical mode best represents the change. In other words, the portion where the relative displacement from the corresponding change point on the reference line encoded immediately before the current encoded line is within the range of 1 to 3 pixels is defined as the density determination element of the image, and the calculation for this one line is The linear density is determined by comparing the numerical value with a certain reference value.

The present invention provides a two-dimensional encoded line (L-current encoded line,
When the number of encoding modes vL and ■R is counted in the one-dimensional encoded line with parameter K (L'-JC line), and this value is compared with a certain reference value, ( If reference value)≦(count value), then high resolution (reference value)>(count value), then standard resolution and sub-scanning line density are determined.

For example, as shown in FIG.
.

When the image has almost the same pattern across multiple scanning areas 12, such as a series of straight line images continuous in the orthogonal direction (2
V in dimensional encoding mode. mode, etc.) Read signal 1
3 can be obtained, but even if the linear density is set to high resolution or standard resolution, the effect on image quality is extremely small, so it is not enough to achieve high resolution.

In the case of the image pattern shown in Fig. 2, in the conventional line density switching control method shown in Fig. 1, each scanning line (1), (11),
Since the number of change points detected by OiD, 6v) is large, each line is regarded as a dense line, and a high-resolution line density is selected, which reduces the transmission efficiency.

However, according to the present invention, a high-resolution line density is selected for the first line (1), but there is no relative change from (1) for lines (11) to Ov), so the vertical mode can be ignored and the standard resolution line density selected. This will be explained in detail below.

FIG. 3 is a diagram for explaining the principle of the system of the present invention. In the figure, 14 indicates a screen, and 15 indicates a main scanning line.

The pulse waveforms of the reference line and data line shown at the bottom of the figure represent black pixels of a character figure located above the corresponding position. According to the encoding rules of OITT Recommendation T.4, the data located below the pulses of the reference line (
If the pulse of the encoding) line is shifted to the left by one pixel, a vertical mode code of VL1 is given, if it is shifted to the left by two pixels, it is vL2, and if it is shifted to the left by three pixels, it is given a vertical mode code of L8.

Similarly, in the case of shift to the right, ■RI, ■R2, ■R3
The vertical mode code of is given. If there is no pixel shift, a vertical mode code of Vo is given.

■L and ■几 indicate that the image is changing, so V
Requires higher resolution processing than o.

In this specific example, only ■ and ■ in one line as shown by ■ to ■ are counted and used as data for density determination.

Next, the present invention will be explained based on examples.

Figure 4 shows one of the facsimile machines implementing the method of the present invention.
In Figure 0, which is a block diagram showing the configuration of an example, 16 is a transmission scanning unit, which includes a photoelectric converter consisting of a photosensor array for converting an image into an electric signal, a photosensor array driver, a pulse motor, and a pulse motor. - Consists of a driver. 17 is a data compression unit, and 18 is a data restoration unit, which performs data compression and data restoration of image signals, respectively, according to the two-dimensional encoding method based on Recommendations T and 4, as described above, and also performs data compression and data restoration of each image signal. In the data restoration process, a vertical mode code VL/vR encoding number counter and density determination function are incorporated to control linear density switching based on the method of the present invention.

Reference numeral 21 denotes a control unit, which has mechanisms for sequence control and line control for both transmission and reception.

Reference numeral 22 denotes an interface section, which includes a modem and a network control device for connection with lines and telephones. 23 is a reception recording section, which includes a recording conversion section for electrostatic recording;
Consists of a multi-stylus driver, pulse motor, and pulse motor driver.

The density determination signals from the data compression section 17 and the data restoration section 18 control the pulse motor drivers in the transmission scanning section 16 and reception recording section 23, respectively, so that the pulse motor corresponds to a predetermined resolution. Sub-scanning line feeding is performed to provide linear density.

FIG. 5 is an operation flow diagram for the data compression section of this embodiment. The basic procedure of this flow follows Recommendation T.4. At the start of the process, it is first checked at 24 whether the scan line is the first line or the first line based on the parameter K.

In the case of these lines, one-dimensional encoding processing is performed at 25. In the case of other lines, two-dimensional encoding processing is performed using the first line or the second line as a reference pressure.
You will be moved to steps 6 onwards.

The two-dimensional encoding processing after No. 26 is divided into path mode, vertical mode, and horizontal mode encoding processing according to the positional relationship of pixels between the reference line and the encoding line.

In step 26, it is checked whether the pixel b2 corresponds to the pass mode (whether pixel b2 according to recommendation T, 4 is on the left of pixel a1).

If applicable, pass mode encoding is performed at step 27, and if not, it is further checked at step 28 whether the mode corresponds to vertical mode (whether the difference between pixel a1 and pixel b1 according to recommendation T, 4 is 3 or less).

If the vertical mode is applicable, vertical mode encoding processing is performed at 29, and if not, horizontal mode encoding processing is performed at 30.

Every time vertical mode encoding processing is performed in 29, 31 te L/
(2) Count up the R mode encoding number counter by +1. Each of the above processes is repeated while determining whether it is the end of a line or the end of a page at 32.33. Although not shown, the VL/VTI mode encoding number counter is cleared at the end of the line.

At the end of each line scan, the content Pi of the VL/VR mode encoding number counter is checked at 34, and the L/v
It is compared with the R mode encoding number reference value Q.

If Q≦Pi, an instruction signal to switch to high resolution linear density is generated at 35. Q) If it is Pi, 35 generates a signal indicating the standard resolution linear density.

Note that the density determination for the one-dimensional encoded line (K line) is based on the immediately previous two-dimensional encoded line (K-1).
Processing is performed by substituting the line density determination results.

FIG. 6 shows an example of the line density in the sub-scanning direction processed in this embodiment. The meanings of the symbols in the diagram are as follows.

Pi: VL/VR mode encoding number encoding number sequence determination for each line ■L/■R mode encoding number reference value Y: Reading/recording at standard resolution Line Z: Reading/recording at high resolution
Line to be recorded: Parameter K(1) in 22-dimensional encoding system: In any natural number diagram, line yNo, (D n −K, (n+
1)・K, (n+2)・K, etc., each line is one-dimensionally encoded, and as mentioned above, density judgment is not performed here, and the previous line is line, for example (n+1) for K
・Consistency determination Q (Pi is applied to the line K-1).

Therefore, following (n+1)・K, < (n+1 >・
The line density of the K+1 line is Z of the high resolution line. Generally, the next line after the line for which the density determination of Q=Pi or Q(Pi is obtained is Z, and the line after the density determination for Q(Pi) is Y of standard resolution.

As described above, the present invention scans at high resolution an encoded line in which the number of change points whose relative displacement with respect to the reference line is within 1 to 3 pixels is greater than the reference value. 1 (by guaranteeing the image quality for 1) and shortening the transmission time for parts with many changes but few minute changes, it is possible to actually reduce the need for facsimile transmission, which is clearer and faster than the conventional method.

Furthermore, since a two-dimensional encoding compressor or decompressor is used, no other counter is required, so there are great advantages in terms of circuit design, such as reduction in circuit scale and simplification of the device.

[Brief explanation of drawings]

FIG. 1(a), Φ) is an explanatory diagram of the conventional automatic line density switching control system, FIG. 2 is an explanatory diagram of the line density switching process in a vertical line pattern, and FIG. 3 is an explanatory diagram of the principle of the present invention. FIG. 4 is a block diagram of a facsimile machine according to an embodiment of the present invention, FIG. 5 is an operation flow diagram of the embodiment, and FIG. 6 is an explanatory diagram of processing results in the embodiment. In the figure, 16 is a transmission scanning section, 17 is a data compression section, 18 is a data restoration section, 19.20 is an L/■ mode encoding number counter and a density determination function, 21 is a control section, 22 is an interface section, 23 indicates a reception recording section. Patent applicant Hiroshi Mori, agent patent attorney of Fujitsu Ltd.

Claims (1)

[Claims] In a two-dimensional encoding facsimile machine, when compressing or decompressing an image signal, the vertical mode codes vL and ■R regarding a certain encoding line are counted, and the counted values are combined with a predetermined reference value. If the counted value is larger than the reference value, the image is considered dense, and if the counted value is smaller than the reference value, it is coarsened. An automatic line density switching control method characterized by sequentially switching sub-scanning line density to change resolution.