JPS61189775A - Coding and transmitting method for picture signal - Google Patents

Abstract

PURPOSE:To decrease the number of coding phenomena to improve the compressing performance without changing the quality of the transmitted pictures and to shorten the coding/transmitting time, by giving a converting process to the level plain signal of a pre-scan line. CONSTITUTION:The level plain signals corresponding to the picture elements #7 and #8 are equal to '1' at level '0' (picture signal equal to level '0'). Thus no coding is carried out. While the picture signal of a pre-scan line #9 is equal to '0' and also equal to a level signal '0' with which the coding is through. Therefore the level plain signal of level '1' is equal to '0' and replaced with the level plain signal '1' of #10. Here the level plain signal 3 of a pre-scan line which is used for coding is equal to 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0. While the level plain signal 8 of the present scan line is equal to 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0 respectively. In a coding mode 11, #5 and #11 of the signal 8 and the virtual changing point of the termination are coded into VL1, VL1 and V0 respectively. In the same way, #3 of the signal 9 and the virtual chainging point of the termination are coded into V0 and V0.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image signal encoding and transmitting method for encoding and transmitting a multivalued image signal obtained by scanning an image having multicolor or multitone signals. It is something.

[Conventional technology]

FIG. 3 is an explanatory diagram for creating a level plane signal from a four-level image signal used in the conventional encoded transmission method. Figure (f) shows an image signal 6 of a scanning line to be encoded, and in this example, the number of pixels in one scanning line is 14 (indicated by 1 to 14 in the figure). In addition, (b) to (e) and (X) to (j) in the same figure are respectively similar to (a) in the same figure.
) and (f), level plane signals 2 to 5 and T to 10 of levels O to 3 of the image signal 1.6 are shown. As shown in FIG. 4, the value of the level brain signal is 1 when the image signal of the pixel to be encoded is equal to the level value, and 0 when it is different.

Figure 5 shows this level plane signal as Modified.
An example of encoding using the Read encoding method (hereinafter referred to as MR encoding method) is shown. This MR encoding method (References: For Kaneji, Kobayashi, Yamazaki, Shiroo:' CCITT
, SGX ■ (Facsimile) Tsukube meeting report °.

Journal of the Institute of Image Electronics Engineers, 9, 1. p, p, 24-30
(1980)) is the standard two-dimensional encoding system for black-and-white binary digital facsimile machines.
This method is recommended by the ITT, and the position of each point of change from white to black or from black to white on the encoded line is mapped to the corresponding reference line on the encoded line or directly above it. It is encoded in relation to the reference point position.

Figures (,), (d) and 100 million) are at level 0.
The pre-scanning line level brain signals 2, 3 and 4 of 1 and 2 are at the level 0.3 and 4 of the same figure, respectively.
The current scanning line level brain signals 7°8 and 9 of levels 1 and 2 are shown in FIG.

FIG. 6 shows the coding elements and code words of this coding method. In the figure, &o is a reference point or starting point on the encoding line, and this position is determined by the previous encoding mode. A is the next change point to the right of the above reference point or starting point a0 on the coding line, 1□ is the next change point to the right of the above change point a1 on the coding line, b is the above reference point. Point or starting point a. To the right of point a. The first change point on the reference line, b2, which is the opposite color of , is the next change point on the reference line to the right of the above change point b1. The horizontal correlation of the level plane signals is then indicated by the horizontal mode code word. M (&O
a, ) and M(a, a2) are code words representing the length and color of lines 'O'l and 'L'2, respectively, and are white or black MK (Modified Huffman).
A code is used. On the other hand, the vertical correlation of the level plane signal is determined by the reference points a on the current scanning line and the previous scanning line. ~62 + b1 + b2 The positional relationship of the comrades, that is, whether the changing point 1□ is located directly below, to the right, or to the left of the changing point b1. How many pixels is changing point 1 shifted from directly below the changing point b1? Indicated by

Next, this encoding operation will be explained according to FIGS. 3 to 6.

Using the conversion method shown in Figure 4, Figures 3(a) and (f)
From the image signal in the same figure (b) to (e), (JZ>~0
) to obtain the level plane signal. Furthermore, level 0
, 1.2 using the MR encoding method.

In this case, the level 3 signal is not encoded. This means that the level 3 signal should be at level 0.
This is because all the signals at levels 0 to 2 become O, and the content of the signal at level 3 can be known from the signals at levels 0 to 2. Furthermore, the white and black signals in the MR encoding system are made to correspond to the level plane signals O and 1, respectively. For convenience of explanation, the pixels of each scan line are numbered Φ1 to ÷14 in order from the left end.

In such an MR encoding method, the starting point a is at the starting end of each scanning line. white, that is, O, on the left side of the first pixel.
virtualize. Here, the level plane signals of the current scanning line level O are sequentially 0, 0, 0 from the left end as shown in FIG.
, 0.0, 0, 1, 1, 0, 0, 0, 0° 0.0, the change point a is equal to the level plane signal T divided by 7. The changing point a2 is ◆9 of this signal 7, the changing point b□ is ≠7 of the level plane signal 2 of the previous scanning line level O, and the changing point b2 is also the signal ÷10 of the signal 2. In this case, the change point a is directly below the change point b'), &1b
1"O, ◆7 of the level plane signal 7 of level O is encoded as v(0) with the code word "l#.

The next encoded element is ÷9 of the level plane signal T of level O, and in this case, the starting point a0° and the change point a1 are the sum of the signal 7 and the 7. φ9, change point b1 is ≠ of the above signal 2
It becomes 10. Therefore, +9 of the level plane signal 7 at level O of the current scanning line is encoded as a code word @010'' by adding vL(1).

Furthermore, in the MR encoding method, a virtual change point is considered at the end of the scanning line for both the current scanning line and the previous scanning line, so in the case of Fig. 5,
A hypothetical change point on the right side of level plane signal 7 of level O of the current scanning line is encoded as V (0).

Similarly, +5 and +7 of the signal 8 of the current scanning line level 1
．． +9. +11 and the terminal virtual change point are respectively vL(
1), V(0), Vh(1), VL(1)
, V(0), the level 2 signal 9 divided by 3. ÷5
．． ÷12. and the virtual change points at the end are v(0), vL(1
), ■(0), and v(0).

FIG. 7(1)l(b) shows the encoding mode and final code sequence in this case, respectively. In the same figure, the four-level image signal consisting of 14 pixels in Fig. 3(f) is shown in Fig. 7(b).
This means that encoding can be performed using a 21-bit code sequence 13 indicated by K.

On the other hand, on the decoding (receiving) side, code sequence 13 in FIG. 7(b)
Since the encoding mode sequences 10 to 12 shown in the figure (,) are obtained by decoding, the level plane signal sequences 2 to 12 of the previous scanning line are decoded.
4 to each level plane signal series 7 to 9 of the current scanning line.
can be obtained. If the table shown in FIG. 4 is used to perform inverse conversion to the above and read out, the four-level image signal 6 of the current scanning line shown in FIG. 3(f) is finally obtained. At this time, level 3
The signal 10 is unnecessary because it can be known from the signals at levels O to 2.

[Problem that the invention seeks to solve]

Since the conventional image signal encoding and transmission method is as described above, as is clear from FIG. 5, the same pixel may be encoded many times using different level planes. For the pixel of , VL(1
), the same < ML(1) is encoded at level 2, resulting in a large number of encoding events and a problem of lowering the compression efficiency of encoding.

This invention was made to solve the above-mentioned problems, and by applying signal conversion to the level plane signal of the previous scanning line, the number of encoding events is reduced and the quality of the transmitted image is changed. The object of the present invention is to provide an image signal encoding method that can greatly improve compression performance without causing any problems, and can thereby greatly shorten code transmission time.

[Means for solving problems]

In the image signal encoding and transmission method according to the present invention, each pixel is converted into each level signal of m values from an image signal of m values (m≧3) obtained by scanning an image having multicolor or multitone signals. Create m types of level plane signals indicating whether they are equal or not, and calculate the horizontal correlation of each level plane signal of the encoded scanning line itself and the same level of the level plane signal and the scanning line that has already been encoded and transmitted. The above-mentioned image signal is encoded using the vertical correlation with the plane signal, and the level plane signal of the pixel of the previous scan that has the same image signal as the level signal that has already been encoded and transmitted is used as the level plane signal of the previous scan. Among the level plane signals of the relevant level of the neighboring pixels currently being scanned on the scanning line, the signal of the nearest pixel is substituted, and encoding is performed.

[Effect]

In this invention, the number of encoding events can be reduced by converting the level plane signal of the previous scanning line. Therefore, the image signal can be significantly compressed without changing the image quality of the transmitted image, ie, the color tone or gradation, and the transmission time of the code transmission time can be shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an example in which the same four-level signal used to explain the conventional encoding and transmitting method is MR encoded according to the encoding and transmitting method of the present invention. In the same figure, (a) to (e) are level plane signals 2 and 7 of the previous scanning line and current scanning line of level 0, respectively, and encoding mode 10, which is the same as the conventional example in Fig. 5. It is.

Further, (d) to (f) are level plane signals 3 and 8 and encoding mode 11 of the previous scanning line and current scanning line of level 1, respectively. Here ÷7. The level plane signal corresponding to the pixel ÷8 is not encoded at the current level because the level plane signal is 1 at level O (the image signal is equal to level signal O). Therefore, the previous scanning line level plane signal +7. +8 is also ignored. Also, the image signal of the previous scanning line ÷ 9 is O, and this is equal to the level signal O that has been encoded, so the level plane signal of level 1 created according to FIG. 4 is O, but
It has been replaced with a level plane signal 1 of +10. Therefore, the previous scanning line level plane signal 3 used during encoding is 0, 0, 0, 0, 0, 1, 1° 1.1, 0, 0.0
Therefore, the level plane signal 8 of the current scanning line is 0, 0, 0.
,0,1,1,1,1,0,0,0.0.

Then, encoding mode 11 is φ5 of signal 8. 11° and the virtual change point at the end is VL (1) + VL (1)
e V(0).

Similarly, for the level 2 signal, the level plane signal 4 of the previous scanning line is 0.0.1, 1, 1, 1, 1, 1, and the level plane signal 9 of the current scanning line is 0.0, 1, 1. ,1゜1
．． 1.1, φ3 of signal 9, and the virtual change point at the end are encoded as V(0) and V(0). Therefore, as shown in FIG. 2(b), the four-level image signal 6 of FIG. 3(f) is encoded as a code sequence 13 of 14 btt.

The decoding side decodes code sequence 13 in Figure 2 (Fig.
Obtain encoding mode sequences 10 to 12 of a).

So, first of all, the first OV (0), VL (1)
, V(0) and the current scan line level plane signal 7 at level O can be obtained from the previous scan line level plane signal 2 at level 0 in FIG. At level 1, from the obtained level plane signal T of level O of the current scanning line and the image signal of the previous scanning line, in the same way as on the transmitting side, the level plane signal 8 of the previous scanning line of level 1 is 0.0,0°. 0.0,1,1
, 1, 1.0, 0, 0, and the current scanning line level 10 level plane (W No. B,
! : 0゜0.0,0,1,1,1,1,0,0,0
．． Get 0.

Similarly, the level plane signal 9 of the current scanning line of level 2 is obtained as shown in FIG. 1(5).

Therefore, using FIG. 4, 4 of the current scanning line shown in FIG.
A value image signal 6 can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, when encoding a level plane signal of a multilevel image signal, the number of encoding events is reduced by applying signal conversion to the level plane signal of a scanning line that has already been transmitted. compression performance can be greatly improved. Further, as the encoding method, a binary signal encoding method used in facsimile, such as MR encoding method, can be applied, and the device configuration can be shared, and the cost can be reduced.

Furthermore, in the apparatus using the method of the present invention, the 1 t capacity is
By limiting the image signal to O and 1 in the hardware and encoding and decoding only the level plane signal of level 0, it is possible to communicate with a binary image signal encoding and decoding device. effective.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method for creating a level plane signal from a four-level image signal and its coding result in an image signal coding and transmission method according to an embodiment of the present invention, and FIG. 2 is a code diagram of this embodiment. Figure 3 is an explanatory diagram showing how a level plane signal is created from a quaternary image signal using the conventional encoding method. Figure 4 is an explanatory diagram showing the creation method. , FIG. 5 is an explanatory diagram showing an example of encoding the level plane signal sequence in FIG. 3, and FIG. 6 is an explanatory diagram showing the correspondence between encoding elements and code words of the MR encoding method used for encoding in FIG. 7 are explanatory diagrams showing the encoding mode and the final code sequence. 2-5, 7-10... Level plane signal. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent Applicant: Mitsubishi Electric Corporation (12 people) No. 1 (a) Repe J Shi On, Oisashi Shokuhoku Seibu Repe Shirup Shi Ichinshin et al. (2
)('b)shiheru0drunkttt line level plane! 8(
7) (c) Encoding mode of public level 0 (10) (d) Collapse of level 1 Llr line level full > t(3) (e)
Level 1 issue (8)
) (f) Level 1 code t-) - (11) (9) Level 2 IQ ν1. Search + & Level - Sea 1s
(4) (h) Lehe71/2/l sli! - Scan line level play sea 8'3 (9) (L) Shihelshi 2n Bamboo number I Shimoichido (12) Figure 4 procedural amendment (voluntary) Indication of case Amendment of Patent Application No. 1987-29751 Representative Hitoshi Katayama, Section 5, Subject of amendment (1) Detailed description of the invention in the specification (2) Drawing 6, content of amendment (1) Line 18 of page 7 of the specification r21 bit J is corrected to ``22 bit J. (2) Figure 7 is corrected as shown in the attached sheet. 7. At least one document containing the corrected figure 7 of attached documents 1) , Ω

Claims (3)

[Claims] (1) M types of levels indicating whether each pixel is equal to each level signal of m values from an image signal of m values (m≧3) obtained by scanning an image having multicolor or multitone signals Create a plane signal and use the horizontal correlation of each level plane signal itself of the encoded scanning line and the vertical correlation between this level plane signal and the level plane signal of the same level of the scanning line that has already been encoded and transmitted. In the image signal encoding transmission method for encoding the image signal, level plane signals of pixels of already scanned scanning lines having an image signal equal to the level signal for which encoding transmission has already been completed are scanned in the same manner. 1. A pixel signal encoding and transmission method, characterized in that the pixel signal is replaced with the closest pixel signal among the level plane signals of the relevant level of the adjacent pixel currently being scanned on the line, and further encoding is performed. (2) In the scanning line that is currently being encoded, for a pixel of an image signal that is equal to the current level signal that is being encoded and transmitted, that pixel will be corresponded to when encoding the level plane signal of the subsequent level. 2. The method of encoding and transmitting an image signal according to claim 1, characterized in that the level plane signal is not encoded. (3) The method for encoding and transmitting an image signal according to claim 1 or 2, wherein the encoding is performed using an MR (Modified Read) encoding method.