JP3134461B2 - Change point detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit (hereinafter referred to as a two-dimensional compression circuit) for compressing pixel data of a scanning line by two-dimensional encoding in a facsimile apparatus or the like.
A circuit for expanding pixel data compressed by dimensional encoding into pixel data before compression (hereinafter referred to as a two-dimensional expansion circuit)
The present invention relates to a change point detection circuit used in a part of the circuit.

[0002]

2. Description of the Related Art Conventionally, CCITT (International Telegraph and Telephone Consultative Committee) has recommended MH, MR and M ² R systems as coding systems for facsimile machines (Recommendations T4 and T6).

[0003] The MH system encodes pixel data of all scan lines by a one-dimensional encoding system. The one-dimensional encoding system is a white image and a black image appearing alternately on one scanning line. Is encoded by a terminating code or a makeup code or a makeup code followed by one terminating code.

[0004] Further, the MR method is a method in which pixel data of one scan line is encoded by a one-dimensional encoding method.
Maximum K-1 pieces (in the case of standard resolution, K = 2, in the case of high-resolution, K = 4) are those that encode the two-dimensional coding scheme successive scan lines, M ² R method Means that the pixel data of all the scanning lines is encoded by a two-dimensional encoding method.

Here, the two-dimensional encoding method is to encode a scan line which is a current encoding target, that is, pixel data of an encoding line, using a line encoded immediately before as a reference line. That is.

In such a two-dimensional encoding method, the following five change points (pixels on the same scanning line and different in color from the immediately preceding pixel) a ₀ , a ₁ , a ₂ , b ₁ , b ₂ are used. At the same time, three encoding modes, a pass mode, a vertical mode, and a horizontal mode, are defined according to the positional relationship between the changing points, and encoding is performed according to the code table shown in Table 1.

[0007]

[Table 1]

Here, a ₀ is defined as a change point which is a starting point on a coding line. At first, it is set to a white pixel virtually positioned immediately before the first pixel of the coding line, and thereafter, it is determined by the immediately preceding coding mode.

Also, a ₁ is defined as the first transition point on the coding line to the right of a ₀ . In addition, change point a
₂ is defined as the first transition point to the right of a ₁ on the coding line. Further, b ₁ is defined as the first change point on the reference line having a color opposite to that of a ₀ in the right of a _0.
Further, b ₂ is defined as the first change point of the right of b ₁ on the reference line.

Here, the pass mode is defined, for example, by the existence of b ₂ on the left side of a ₁ as shown in FIG. After encoding in the pass mode, a ₀ is set immediately below b ₂ (a ₀ ′) in preparation for the next encoding.

The vertical mode is defined, for example, by a relative distance | a ₁ b ₁ | between a ₁ and b ₁ being 3 or less, as shown in FIG. In this case, the relative distance | a ₁
b ₁ | are seven values represented by different symbols depending on the positional relationship between a ₁ and b ₁ , V (0), V _R (1), V _R (2), V _R
(3), one of V _L (1), V _L (2), and V _L (3). After the coding in the vertical mode, a ₀ is set at the position a ₁ (a ₀ ′) in preparation for the next coding.

The horizontal mode is defined by, for example, that the relative distance | a ₁ b ₁ | between a ₁ and b ₁ is 4 or more as shown in FIG. In this case, 001 + H (a ₀ a
₁ ) Encoding is performed using + H (a ₁ a ₂ ). Note that H (a ₀
a ₁ ) and H (a ₁ a ₂ ) mean that the distance a ₀ a ₁ and the distance a ₁ a ₂ are coded by a one-dimensional coding method, respectively. After encoding in the horizontal mode, a ₀ is set to the position a ₂ (a ₀ ′) in preparation for the next encoding.

Here, the two-dimensional encoding is performed by detecting the encoding mode. Specifically, the two-dimensional encoding is performed according to the following procedures 1 and 2. 31 and 32.
5 is a flowchart showing the contents of procedure 1 and procedure 2 in more detail.

Procedure 1 (a) When b ₁ exists on the left side of a ₁ , it is assumed that the path mode has been detected, and coding corresponding to the path mode is performed. Thereafter, are the change points a ₀ point directly below the b _2. (A) If the path mode is not detected, the procedure proceeds to procedure 2.

Procedure 2 (a) Determine the absolute value of the relative distance | a ₁ b ₁ | (A) If | a ₁ b ₁ | ≦ 3, it is assumed that the vertical mode has been detected, and encoding corresponding to the vertical mode is performed. Thereafter, the change point a ₁ is the change point a _0. (A) If | a ₁ b ₁ |> 3, it is assumed that the horizontal mode has been detected, and encoding corresponding to the horizontal mode is performed. Thereafter, the change point a ₂ are change point a _0.

[0016]

FIG. 31 and FIG.
The flowchart shown in FIG. 2 includes a case where a once-detected change point has to be detected again.
If the change point detection circuit is configured to carry out the flow charts shown in FIGS. 31 and 32 as it is, there is a problem that the circuit configuration becomes extremely complicated. The same applies to the case where a change point is detected in the M ² R method.

In view of the above, the present invention is required when compressing pixel data of a scanning line by two-dimensional encoding or when decompressing pixel data compressed by two-dimensional encoding into pixel data before compression. To provide a change point detection circuit capable of detecting a change point with a simple circuit configuration and reducing the size of a two-dimensional compression circuit and a two-dimensional expansion circuit. Aim.

[0018]

FIG. 1 is a diagram for explaining the principle of the present invention. In FIG. 1, reference numeral 1 denotes an 8-bit shift register for shifting pixel data of a reference line; This is a reference line change point detection circuit for detecting the position of the change point of the reference line within a suitable range.

Reference numeral 3 denotes a 2-bit shift register for shifting the pixel data of the coding line, and reference numeral 4 denotes a coding line change point detection for detecting the presence or absence of a change point of the coding line in the shift register 3. Circuit.

Reference numeral 5 denotes a storage circuit for storing the fact that, if necessary, when a shift point is present in the seventh bit of the shift register 1 and a 1-bit shift is performed.

Note that in this specification, "the case where a change point exists at the n-th bit" of the shift register means that
This means that the colors of the n-th bit and the (n + 1) -th bit of the shift register are different.

[0022]

According to the present invention, when this is used as a part of a two-dimensional compression circuit for performing compression by two-dimensional encoding, pixel data of a reference line and an encoded line are respectively taken into shift registers 1 and 3, Shift.

In this case, the position information of the change point of the reference line output from the reference line change point detection circuit 2 and the presence / absence of the change point of the coded line output from the coding line change point detection circuit 4 are determined. The encoding mode can be known from the information and the contents stored in the storage circuit 5.

Further, according to the present invention, when this is used as a part of a two-dimensional decompression circuit for decompressing pixel data compressed by two-dimensional encoding into pixel data before compression, the data is compressed by two-dimensional encoding. A different circuit determines which encoding mode the encoded pixel data has been encoded in, and
The pixel data of the reference line is taken into the shift register 1 and shifted.

In this case, based on the position information of the change point of the reference line output from the reference line change point detection circuit 2 and the contents stored in the storage circuit 5, the reference line is shifted to a position corresponding to the determined encoding mode. Can be shifted, and by generating pixel data using this state, the pixel data compressed by the two-dimensional encoding can be expanded to the pixel data before compression.

[0026]

Embodiments of the present invention will be described below with reference to FIGS. 2 to 26. (1) Configuration, (2) Operation when used as part of a two-dimensional compression circuit, (3) Two-dimensional The operation when used for a part of the decompression circuit and the effect (4) will be described separately.

(1) Configuration FIG. 2 and FIG. 3 FIG. 2 is a block diagram showing a main part of an embodiment of the present invention. In FIG. 2, reference numeral 6 denotes 8 bits for shifting pixel data of a reference line. , A flag which forms a current color display circuit for internally displaying a color to be compared with the color of the change point as the current color, and 8 a color between adjacent bits of the shift register 6 and the flag 7 Is a comparator for detecting a place where a change point is present by comparing the current color displayed by the.

Reference numeral 9 denotes a mask counter for instructing the comparator 8 on the range in which the comparison is to be performed. For example, when the count value of the mask counter 9 is "3", the comparator 8 operates at the lowest position. Operates to detect a change point existing from the first bit to the third bit. In other words, the comparator 8 operates so as not to detect a transition point at the fourth to seventh bits. The comparator 8 always performs comparison between 3 bits and 4 bits in addition to the comparison based on this instruction.

The mask counter 9 is required when setting the initial state and resetting after the mode determination, and is counted according to the shift of the reference line.
It is controlled not to count above "7".

Reference numeral 10 denotes a two-bit shift register for shifting the pixel data of the encoding line, and reference numeral 11 denotes a comparator for comparing colors between bits in the shift register 10 to detect the presence or absence of a change point.

Reference numeral 12 denotes a case where a change point to be detected exists at the seventh bit in the shift register 6, a shift of one bit is performed, and a case where no change point exists in the shift register 10. In fact, that is, a flag for holding that there is a change point of the comparison overflow not used for the mode determination. As shown in FIG. 0 "
Is set, and if it exists, "1" is set.
This is necessary to completely detect the pass mode.

Reference numeral 13 denotes a run-length counter for counting the run lengths of the white image and the black image. The run-length counter 13 starts counting at the same time as the start of detection of a change point. Is reset to "0" when the encoding mode detected in step (1) is other than the horizontal mode and when the encoding mode determined at the time of decompression is other than the horizontal mode.

A code output circuit 14 constitutes a two-dimensional compression circuit. The code output circuit 14 detects an encoding mode in accordance with the outputs of the comparators 8 and 11 and the contents of the flag 12, and outputs a code. 1 to output a corresponding code. In the case of the horizontal mode, one-dimensional encoding is performed after the run length is counted using the run length counter 13.

Reference numeral 15 denotes a mode determination circuit which constitutes a two-dimensional expansion circuit. The mode determination circuit 15 determines in which coding mode the pixel data to be expanded is compressed. Reference numeral 16 denotes a shift register for outputting expanded image data.

(2) Operation when used as part of a two-dimensional compression circuit. FIGS. 4 to 15 First, an initial state is set. First, the output value of the mask counter 9 is set to " 4, the pixel data of the reference line is fetched into the shift register 6 and shifted by 3 bits, as shown in FIG.
This is performed by setting the run length counter 13 to "-1".

At this time, the output value of the mask counter 9 becomes "3", the flag 12 is set to "0", and a state where there is no change point of the comparison overflow is displayed. In the flag 7, the current color to be displayed is set to "white".

When a change point at which the encoding mode can be determined is detected, a reset is performed. This is because the output value of the mask counter 9 is set to "3" as shown in FIG. A reset is performed by excluding the change point existing in the fourth bit or more counted from the least significant bit of the shift register 6 from the detection target, and inverting the current color of the flag 7 except when the pass mode is detected. Will be

Here, in this embodiment, when the reference line and the encoding line are simultaneously shifted from the initial state or the reset state, the encoding mode is detected as follows.

If the change point of the reference line is detected at the fourth bit counting from the least significant bit and the change point of the coding line is also detected, this is the state shown in FIG. By detecting such a change point, the vertical mode V
(0) is determined, and the vertical mode V
The code corresponding to (0) is output.

When the change point of the reference line is detected at the fifth bit counting from the least significant bit and the change point of the coded line is also detected, since this is the state shown in FIG. By detecting such a change point, the vertical mode V
_R (1) is determined, and the vertical mode V
_The code corresponding to _R (1) is output.

When the change point of the reference line is detected at the sixth bit counting from the least significant bit and the change point of the coded line is also detected, since this is the state shown in FIG. By detecting such a change point, the vertical mode V
_R (2) is determined, and the vertical mode V
_The code corresponding to _R (2) is output.

When the change point of the reference line is detected at the seventh bit counting from the least significant bit and the change point of the coding line is also detected, since this is the state shown in FIG. By detecting such a change point, the vertical mode V
_R (3) is determined, and the sign output circuit 14 outputs the vertical mode V
_The code corresponding to _R (3) is output.

When the change point of the reference line is detected at the third bit counting from the least significant bit and the change point of the coding line is also detected, this is the state shown in FIG. By detecting such a change point, the vertical mode V _L (1) is determined, and the code output circuit 14 outputs a code corresponding to the vertical mode V _L (1).

When the change point of the reference line is detected at the second bit counting from the least significant bit and the change point of the coding line is also detected, this is the state shown in FIG. By detecting such a change point, the vertical mode V _L (2) is determined, and the code output circuit 14 outputs a code corresponding to the vertical mode V _L (2).

When the change point of the reference line is detected in the least significant bit and the change point of the coding line is also detected,
Since this is the state shown in FIG. 12, the vertical mode V _L (3) is determined by detecting such a change point.
The code output circuit 14 outputs a code corresponding to the vertical mode V _L (3).

When the change point of the reference line is detected at the 7th and 4th bits counting from the least significant bit, and the change point of the coding line is not detected, this corresponds to FIG.
In the state shown in (1), the pass mode P is determined by detecting such a change point, and the code output circuit 14 outputs a code corresponding to the pass mode P.

The change point of the reference line is detected at the fourth bit counting from the least significant bit, and the flag 12 =
In the case where the change point of the coding line is not detected in 1, this is the state as shown in FIG. 14. The code corresponding to P is output.

Further, no change point of the reference line is detected,
If a transition point in the coding line is detected,
Since the state is as shown in FIG. 5A, the horizontal mode H can be determined by detecting such a change point.

Therefore, in this case, after the value "XXXX" of the run-length counter 13 is stored and reset, the shift register 10 is reset as shown in FIG.
The reference line and the encoding line are shifted until a change point is detected in.

At this time, the value “YYYY” indicated by the run-length counter 13 indicates the distance a ₁ a ₂ , and the previously saved “XXXX” indicates the distance a ₀ a ₁ . _{001 + H (a 0 a 1} ) + perform H (a ₁ a ₂₎ comprising coding.

In this way, two-dimensional encoding is performed. In this embodiment, however, unlike the case of a circuit that directly executes the flowcharts shown in FIGS. 31 and 32, a once-detected change point is detected again. You don't have to.

(3) Operation when used as part of a two-dimensional decompression circuit: FIGS. 16 to 26 First, an initial state is set. In the state where it is set to “0”, as shown in FIG. 16, the pixel data of the reference line is taken into the shift register 6 and shifted by 4 bits.

At this time, the output value of the mask counter 9 is "4". The flag 12 is set to "0" to indicate that there is no change point in the comparison overflow. The method of resetting is the same as in the case of compression.

Here, in the present embodiment, it is determined by the mode determination circuit 15 in which encoding mode the pixel data to be decompressed has been compressed, and the determined encoding mode is the vertical mode and the pass mode. In the case of the mode, the reference line is shifted and expanded such that a change point of the reference line is detected at a position corresponding to the encoding mode.

For example, when the pixel data to be expanded is encoded in the vertical mode V (0), as shown in FIG. As detected, the reference line is shifted while outputting the current color from the flag 7 to the shift register 16, and then the current color of the flag 7 is inverted in preparation for the next expansion.

For example, when the pixel data to be expanded is encoded in the vertical mode V _R (1), as shown in FIG. 18, the fifth bit counting from the least significant bit of the shift register 6 is used. The reference line is shifted while the current color is output from the flag 7 to the shift register 16 so that a change point is detected, and then the current color of the flag 7 is inverted for the next expansion.

For example, when the pixel data to be expanded is encoded in the vertical mode V _R (2), as shown in FIG. 19, the sixth bit counted from the least significant bit of the shift register 6 is used. The reference line is shifted while the current color is output from the flag 7 to the shift register 16 so that a change point is detected, and then the current color of the flag 7 is inverted for the next expansion.

For example, when the pixel data to be decompressed is encoded in the vertical mode V _R (3), the seventh bit counted from the least significant bit of the shift register 6 as shown in FIG. The reference line is shifted while the current color is output from the flag 7 to the shift register 16 so that a change point is detected, and then the current color of the flag 7 is inverted for the next expansion.

For example, when the pixel data to be expanded is encoded in the vertical mode V _L (1), as shown in FIG. 21, the third bit counted from the least significant bit of the shift register 6 is used. The reference line is shifted while the current color is output from the flag 7 to the shift register 16 so that a change point is detected, and then the current color of the flag 7 is inverted for the next expansion.

For example, when pixel data to be expanded is encoded in the vertical mode V _L (2), as shown in FIG. 22, the second bit counted from the least significant bit of the shift register 6 is used. The reference line is shifted while the current color is output from the flag 7 to the shift register 16 so that a change point is detected, and then the current color of the flag 7 is inverted for the next expansion.

For example, when pixel data to be expanded is encoded in the vertical mode V _L (3), a change point is detected in the least significant bit of the shift register 6 as shown in FIG. As described above, the shift register 16
Shifts the reference line while outputting the current color to
Thereafter, the current color of the flag 7 is inverted for the next decompression.

For example, when pixel data to be expanded is encoded in the pass mode P, the flag 1
When 2 = “0”, as shown in FIG. 24, the shift register 16 is shifted from the flag 7 so that the change point is detected at the seventh and fourth bits counted from the least significant bit of the shift register 6. Shift the reference line while outputting the current color. In this case, the current color of the flag 7 is not inverted.

For example, when the pixel data to be expanded is encoded in the pass mode P, the flag 1
When 2 = “1”, as shown in FIG. 25, the shift register 16 is shifted from the flag 7 so that a change point is detected at the fourth bit counting from the least significant bit of the shift register 6.
Shift the reference line while outputting the current color. In this case, the current color of the flag 7 is not inverted.

On the other hand, when the pixel data to be decompressed is encoded in the horizontal mode H, FIG.
As shown in (a), the reference line is output from the flag 7 to the shift register 16 using the run-length counter 13 until the count value “XXXX” indicates the distance a ₀ a ₁ . , The current color of the flag 7 is inverted, and the run-length counter 13 is reset to “0”.

[0065] After that, subsequently, as shown in FIG. 26 (b), using a run-length counter 13, the count value "YYYY" until indicates the distance a ₁ a _2, from the flag 7 to the shift register 16 On the other hand, the reference line is shifted while outputting the current color, the current color of the flag 7 is inverted, and the run-length counter 13 is reset to “0”.

In this manner, the pixel data compressed by the two-dimensional encoding is expanded. In this embodiment, as in the case of the two-dimensional encoding, the once detected change point is detected again. You don't have to.

(4) Effects According to the present embodiment, a case where pixel data of a scan line is compressed by two-dimensional encoding, or a case where pixel data compressed by two-dimensional encoding is expanded to pixel data before compression The change point once detected is prevented from being detected again, and the required change point can be detected with a simple circuit configuration. Eliminates the need to use complex circuits that need to detect change points again,
The size of the two-dimensional compression circuit and the two-dimensional expansion circuit can be reduced.

[0068]

As described above, according to the present invention, pixel data of a scan line is compressed by two-dimensional encoding, or pixel data compressed by two-dimensional encoding is expanded to pixel data before compression. In this case, the change point once detected is not required to be detected again, and the required change point can be detected with a simple circuit configuration. Does not need to be configured as a complicated circuit that must be detected again, and the two-dimensional compression circuit and the two-dimensional expansion circuit can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram showing a main part of one embodiment of the present invention.

FIG. 3 is a diagram illustrating a method of using a flag for holding a change point of a comparison overflow in a case where an embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 4 is a diagram illustrating a state in which an initial state is set when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 5 is a diagram illustrating a method of resetting a mask counter when the embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 6 is a diagram showing a state in which a vertical mode V (0) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 7 is a diagram showing a state in which a vertical mode V _R (1) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 8 is a diagram showing a state in which a vertical mode V _R (2) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 9 is a diagram showing a state in which a vertical mode V _R (3) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 10 is a diagram showing a state in which a vertical mode V _L (1) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 11 is a diagram illustrating a state in which a vertical mode V _L (2) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 12 is a diagram showing a state in which a vertical mode V _L (3) is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 13 is a diagram illustrating a state in which a path mode P is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 14 is a diagram illustrating a state in which a path mode P is detected when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding.

FIG. 15 is a diagram for explaining a state in which a horizontal mode H is detected and a measure to be taken in that case when one embodiment of the present invention is used in a part of a two-dimensional compression circuit that performs compression by two-dimensional encoding. FIG.

FIG. 16 is a diagram showing a case where an initial state is set when one embodiment of the present invention is used in a part of a two-dimensional expansion circuit for expanding two-dimensional code data.

FIG. 17 is a diagram showing an embodiment of the present invention in which a two-dimensional code is expanded
FIG. 11 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the vertical mode V (0) when used in a part of the dimension expansion circuit.

FIG. 18 is a diagram showing an embodiment of the present invention, in which a two-dimensional code is expanded 2
Pixel data to be extended in the case of using a portion of the dimension decompression circuit is a diagram showing an extended operation when it is determined that it is encoded by the vertical mode V _R (1).

FIG. 19 shows an embodiment of the present invention in which a two-dimensional code is expanded 2
Pixel data to be extended in the case of using a portion of the dimension decompression circuit is a diagram showing an extended operation when it is determined that it is encoded by the vertical mode V _R (2).

FIG. 20 is a diagram illustrating an embodiment of the present invention, in which two-dimensional codes are expanded.
Pixel data to be extended in the case of using a portion of the dimension decompression circuit is a diagram showing an extended operation when it is determined that it is encoded by the vertical mode V _R (3).

FIG. 21 is a diagram showing an embodiment of the present invention, in which a two-dimensional code is expanded 2
FIG. 8 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the vertical mode V _L (1) when used in a part of the dimension expansion circuit.

FIG. 22 is a diagram showing an example of expanding the two-dimensional code according to an embodiment of the present invention.
FIG. 8 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the vertical mode V _L (2) when used in a part of the dimension expansion circuit.

FIG. 23 shows an embodiment of the present invention, in which a two-dimensional code is expanded 2
FIG. 11 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the vertical mode V _L (3) when used in a part of the dimension expansion circuit.

FIG. 24 shows an embodiment of the present invention in which a two-dimensional code is expanded 2
FIG. 9 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the pass mode P when used in a part of the dimension expansion circuit.

FIG. 25 shows an embodiment of the present invention in which a two-dimensional code is expanded 2
FIG. 9 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the pass mode P when used in a part of the dimension expansion circuit.

FIG. 26 shows an embodiment of the present invention, in which a two-dimensional code is expanded 2
FIG. 11 is a diagram illustrating an expansion operation when it is determined that pixel data to be expanded is encoded in the horizontal mode H when used in a part of the dimension expansion circuit.

FIG. 27 is a diagram for describing a change point defined in the two-dimensional encoding method.

FIG. 28 is a diagram for describing a pass mode defined in the two-dimensional encoding method.

FIG. 29 is a diagram for describing a vertical mode defined in the two-dimensional encoding method.

FIG. 30 is a diagram for describing a horizontal mode defined in the two-dimensional encoding method.

FIG. 31 is a flowchart showing an encoding procedure by the MR method.

FIG. 32 is a flowchart showing an encoding procedure by the MR method.

[Explanation of symbols]

 Reference Signs List 1 8-bit shift register 2 Reference line change point detection circuit 3 2-bit shift register 4 Encoding line change point detection circuit 5 Storage circuit

Claims (2)

(57) [Claims] 1. An 8-bit first shift register (1) for shifting pixel data of a reference line, and a change point of the reference line within a necessary range in the first shift register (1). A reference line change point detection circuit (2) for detecting a position, and a 2-bit second shift register (3) for shifting pixel data of an encoding line
A coding line change point detection circuit (4) for detecting the presence or absence of a change point of the coding line in the second shift register (3); and the first shift register (1)
If there is a change point in the 7th bit of
A change point detection circuit characterized by being provided with a storage circuit (5) for storing the fact that a shift by bits has been performed, if necessary. 2. A current color display circuit for internally displaying a color to be compared with a color of a change point as a current color, wherein a current color display circuit is provided for a reference line between adjacent bits of the first shift register (1). A first comparison circuit for comparing a color with the current color;
The reference line change point detection circuit (2) comprises a comparison range designating circuit for designating a bit range of the first shift register (1) to be compared with the first comparison circuit. The coding line change point detection circuit (4) comprises a second comparison circuit for comparing the color of the coding line between adjacent bits of the second shift register (3) with the current color. The change point detection circuit according to claim 1, wherein: