JP3248312B2 - Communication device for color still images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus for a color still image, and more particularly to a communication apparatus for transmitting a color image encoded by a lossy encoding method to a terminal station via a relay station. About.

[0002]

2. Description of the Related Art As an example of a communication method of a color still image,
An image communication method using a facsimile machine will be described. FIG.
FIG. 2 is a block diagram showing a data processing flow in an image communication method employing an irreversible encoding method. In FIG. 1, a reading device 10 including a CCD image sensor and the like
0 decomposes the read image data of the original into three primary colors of R, G, and B, and outputs analog signals corresponding to each of the three primary colors. The A / D converter 101 converts the analog signal of each color supplied from the reading device 100 into a digital signal having a predetermined number of bits (for example, 12 bits) and outputs the digital signal.

[0003] Image data read by the reading device 100 generally has distortion called shading. This shading is said to occur due to uneven illumination in the main scanning direction, uneven light amount of the image sensor due to the nature of the lens, and uneven sensitivity of the image sensor. The shading correction device 102 performs a process for correcting these non-uniformities.

[0004] The color space conversion device 103 includes image data (R, G, and G) supplied from the shading correction device 102.
B) is converted into L, a, and b signals by the CIELAB method. CIELAB is a color space expression method defined by the International Institute of Lighting (CIE). The encoding device 104 compression-encodes the color space-converted image data. Here, processes such as orthogonal transformation, quantization, and entropy encoding of data are performed.

[0005] The compression-encoded image data is transmitted to the receiver side via a line, and the receiver side first decodes the received signal into signals L, a, and b by a decoding device 105.
Next, the signals L, a, and b are supplied to the YMC converter 106, and the signals Y,
(Yellow), M (magenta), and C (cyan).

The signals Y, M, and C are supplied to a K generator 107, which removes undercolor (UC) for the purpose of reducing the consumption of ink and toner and expanding the color reproduction range, that is, improving the reproducibility of black.
The processing of R) is performed. Further, the signal subjected to the UCR processing is subjected to a digital filter processing in a two-dimensional space by a digital filter 108 in order to emphasize edges of characters and the like and to remove noise in an image.

The TRC processor 109 performs non-linear conversion for the purpose of correcting printer characteristics, such as outputting a linear input signal as a non-linear signal, and responding to a density instruction. In the case of using a printer that cannot reproduce a continuous tone or a printer that can reproduce only a smaller number of gradations than the number of gradations to be reproduced, the halftone generator 110 converts the signal supplied from the TRC processing unit 109 into a pseudo halftone Convert to data. Conversion to pseudo halftone image data includes a dither method, an error diffusion method, a conversion method using an analog screen generator, and the like. The signal subjected to the above processing is supplied to the printer 111 and output as a print image.

[0008] Parameters for processing such as orthogonal transformation, quantization, and entropy coding of data in the coding device 104 are transmitted to a receiver side for use in decoding coded image data.

[0009]

The above-mentioned conventional image communication method using a facsimile apparatus has the following problems. That is, since the encoding method in the encoding device 104 is an irreversible process, if decoding and encoding are repeated, the image quality is greatly deteriorated. Normally, such decoding and encoding are not repeated, but such a situation may occur in, for example, relay broadcasting.

In the relay broadcast, the relay station decodes the image information sent from the designated station and temporarily stored using the quantization table sent from the designated station. The encoding process is performed using the quantization table, and the encoded image information is transmitted (broadcast) to each terminal station together with its own quantization table.

Therefore, in such relay broadcasting, image information is inversely quantized at both the relay station and the terminal station, and there is a problem that image quality is particularly deteriorated.

An object of the present invention is to solve the above problems,
It is an object of the present invention to provide a color still image communication device capable of performing relay broadcasting without deteriorating the image quality of a color image processed by an encoding method including irreversible processing.

[0013]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the object, the present invention determines whether or not a protocol instruction received from an instruction station includes a color instruction and a relay broadcast instruction. Means for transferring the received image information to the terminal station without decoding the received image information when the color instruction and the relay broadcast instruction are included, and a quantization table received from the instruction station. And a means for transmitting to the terminal station.

[0014]

When there is a color instruction and a relay broadcast instruction, the received image information is transferred to the terminal station without being decoded by the relay station. Further, the quantization table transmitted from the designated station is also transferred to the terminal station. As a result, unnecessary decoding processing of the image information is not performed, so that it is possible to avoid deterioration in image quality due to repeated decoding and encoding.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 2 is a block diagram showing a hardware configuration (part 1) of the facsimile apparatus according to one embodiment of the present invention, and FIG. 3 is a block diagram showing the hardware configuration (part 2).

First, the configurations of the main control unit and the image signal processing unit will be described with reference to FIG. In FIG. 1, a main control unit 1 performs control processing of the entire facsimile machine. The CPU 10 of the main control unit 1 executes a scheduled program to control the entire facsimile machine. The ROM 11 stores the program and system data necessary for executing the program. The RAM 12 stores all data to be temporarily stored, for example, image data files and control data. A hard disk (HDD) 14 is used as a large-capacity auxiliary storage device, and the hard disk 14 is controlled by an HD control unit (HDC) 13.

The operation unit 15 includes an input unit for receiving an input from an operator, and a display unit for displaying an input instruction and a processing result based on the input. Bus interface (B
usIF) 16 is a VM connected to each processing unit described later.
The local bus 17 is an interface unit with the system bus 9 such as an E bus, and is a means for transmitting data and signals in the main control unit 1.

The image signal processing unit 2 processes input / output signals for the facsimile machine. The CPU 20 controls the image signal processing unit 2 by executing a scheduled control processing program, and executes communication with the main control unit 1. R
The OM 21 stores programs and data for controlling the image signal processing unit 2 and communicating with the main control unit 1. The RAM 22 stores data temporarily used by the image signal processing unit 2.

The image input unit 23 takes in image data read by a CCD image sensor (not shown) and performs light / dark correction and color correction such as shading correction. On the other hand, the image output unit 24 performs density correction, color correction, and the like on the image data according to the state of a printer (not shown),
Output to the printer (not shown). The color space conversion unit 25 performs color space conversion of the image data.

The enlarging / reducing unit 26 executes an enlarging / reducing process of image data. Bus interface (Bus
The IF 27 is an interface unit with the system bus 9, and the local bus 28 is a means for transmitting data and signals in the image signal processing unit 2.

Next, the configurations of the image encoding unit and the communication unit will be described with reference to FIG. In FIG. 1, an image encoding unit 3 encodes and decodes image data by a lossy encoding method. The CPU 30 executes a scheduled control processing program to control the image encoding unit 3 and execute communication with the main control unit 1. The ROM 31 stores programs and data for controlling the image encoding unit 3 and communicating with the main control unit 1. RA
In M32, data temporarily used by the image encoding unit 3 is stored.

The Huffman encoding / decoding section 33 compresses the quantized image data by the Huffman encoding method or vice versa. Processing of image data by the Huffman coding method is performed by a Huffman table stored in the table storage unit 34. This table storage unit 3
Reference numeral 4 denotes a rewritable memory.

A DCT / inverse (I) DCT unit 37 for orthogonally transforming image data performs discrete cosine transform on each block of the input image divided into M pixels vertically by N pixels horizontally.
Or the reverse process is performed. For example, if the (j, k) -th pixel value of a certain block is f (j, k) and the (u, v) -th element of the transform coefficient is F (u, v),
The DCT transform is defined by equation (1), and the inverse DCT transform is
Defined in (2).

F (u, v) = (2 / N) C (u) C (v) Σ [j = 0, N−1] Σ [k = 0, N−1] f (j, k) cos {(2j + 1) uπ / 2N {cos} (2k + 1) vπ / 2N} (1) where C (u) and C (v) are 1 / when u and v = 0.
(2 ^1/2 ), 1 when u, v ≠ 0. f (j, k) = (2 / N) {[u = 0, N-1] {[v = 0, N-1] C (u) C (v) F (u, v) cos} (2j + 1 ) Uπ / 2N {cos} (2k + 1) vπ / 2N} (2) The quantization / inverse quantization unit 35 quantizes the transform coefficient of each frequency component transformed by the DCT (discrete cosine transform) method. And vice versa. Quantization / dequantization unit 35
Is performed by a quantization table stored in the table storage unit 36. This table storage unit 36
Is composed of a rewritable memory.

In the quantization table, “M × N quantization step values” respectively corresponding to M × N transform coefficients are stored.
Is set, the conversion coefficient is divided by this step value, and further rounded off. For example, the transform coefficient (u,
If the (v) -th element is F (u, v) and the (u, v) -th element of the quantization step value is Q (u, v), the (u,
The v) th quantization index I (u, v) is defined by equation (3). I (u, v) = round {F (u, v) / Q (u, v)} Equation (3) where round means conversion to the nearest integer.

Bus interface (Bus IF) 38
Is an interface unit with the system bus 9, and the local bus 39 is a data and signal transmission unit in the image encoding unit 3.

Further, the first communication control unit 4 and the second communication control unit 5 execute G3 or G4 protocol control after the line connection. The line switching control unit 6 connects and disconnects the interfaces provided by the plurality of line control units to the first communication control unit 4 and the second communication control unit 5. The digital network interface (IF) control unit 7
An analog network interface (IF) controller 8 executes connection and disconnection to a digital network such as SDN, and executes connection and disconnection to a telephone network.

Note that, instead of the DCT / inverse DCT section 37, a transform section using other orthogonal transform such as Hadamard transform, KL transform, DST transform, Haar transform may be used. Also, the Huffman encoding / decoding unit 33 may be another entropy encoding means such as arithmetic encoding.

Next, transmission and reception operations when the facsimile apparatus having the above-described hardware is used as a relay station will be described with reference to the flowchart of FIG. In the present embodiment, an example of communication in the G4 communication mode will be described.

In FIG. 4, in step S1, the document capability list CDCL sent from the instruction station is analyzed to determine whether or not there is a color instruction. If there is no color instruction, the normal black-and-white image information receiving operation (step S20)
Perform 0). The receiving operation includes an operation for relaying the black and white image information, but the operation is well known and will not be described.

If there is a color instruction, the process proceeds to step S2,
Similarly, it is determined whether or not a relay broadcast instruction is added to the document capability list CDCL. An example of the document capability list CDCL will be described later with reference to FIG.

If there is no relay broadcast instruction, the flow advances to step S3 to receive the quantization table Ta1 sent from the instruction station and store it in the RAM 12. In step S4, the image information is received and stored in a storage area secured in the HDD 14 as an image information memory. In step S5, the RAM 1
2 is read out. In step S6, decoding is performed using the quantization table Ta1. In step S7, the decoded image information is output to the printer.

On the other hand, if the relay broadcast instruction is detected, the flow advances from step S2 to step S8 to receive the quantization table Ta1 sent from the instruction station and store it in the RAM 12. In step S9, the image information is received and stored in the image information memory. In step S10, the RAM 1
2 is read out. In step S11, terminal station data is read from the RAM 12.
This terminal station data is read from the frame received from the designated station, that is, from the document capability list
2 is stored. In step S12,
Place a call based on the read terminal data.

If the line is connected, step S13
In step S1, the quantization table Ta1 is transmitted.
In step 4, the received image information is read from the image information memory and transmitted. When the transmission of the image information is completed, in step S15, it is determined whether or not there is any terminal whose transmission has not been completed yet. If this judgment is affirmative, step S1
Return to 1. If the transmission has been completed to all the terminal stations specified in the document capability list CDCL, the process proceeds to step S16, and the broadcast ends.

In order to clarify the effect of the present embodiment, a conventional process of relay broadcasting of a color image will be described with reference to a flowchart of FIG. Note that the processing shown in FIG. 5 is subsequent to step S10 (FIG. 4). Step S10
0, the quantization table Ta1 received from the pointing station
Is used to decode the received image information. Step S110
Then, the quantization table Ta2 for the own station stored in the RAM 12 in advance is read. Step S1
At 20, the decoded image information is encoded again using the quantization table Ta2. Step S130
Then, the terminal station data is read from the RAM 12. In step S140, a call is made based on the read terminal station data.

If the line is connected, step S15
0, the quantization table Ta2 is transmitted.
At 160, the received image information is transmitted. Hereinafter, steps S170 and S180 are performed in steps S15 and S1.
6 and the description is omitted.

In the above description, the operation for relaying to a terminal station when a color instruction is given and a relay broadcast instruction is detected has been described. Not only the information but also the operation of printing the received document for the own station is performed according to the instruction from the instruction station. In this case, the received image information is decoded and printed using the quantization table Ta1.

FIG. 6 shows a frame structure of the session start response RSSP for declaring communication capability, and a document capability list CDC for notifying the relay broadcast instruction.
The frame configuration of L is shown in FIG.

In FIG. 6, the session start response RSS
P includes a communication capability as a non-standard function, and further describes a relay broadcast receiving capability and information as the communication capability. Similarly, in FIG.
The DCL includes a relay broadcast instruction as a function function, and further describes terminal station information as the content of the relay broadcast instruction. Here, an example is shown in which the short number of the terminal station registered in the relay station is indicated as the terminal station information.
The color instruction is described as information in the document profile attribute of the CDCL frame.

Next, the main functions of the facsimile apparatus of the present embodiment for executing the operation shown with reference to the flowchart will be described. In FIG. 1, a receiving unit 40 transfers protocol information (CDCL frame) among the received information to an instruction station instruction determination unit 41, and stores received image information in an image information storage unit 42. Note that a quantization table is added as header information to the received image information. The instruction station instruction determination unit 41 determines the presence or absence of a relay broadcast instruction and a color instruction with reference to the CDCL frame.

When the relay broadcast instruction and the color instruction are detected, the relay broadcast detection signal St and the color detection signal Sc are output, respectively. When both the relay broadcast detection signal St and the color detection signal Sc are supplied, the image information and the quantization table stored in the image information storage unit 42 are read out by the transmission unit 43 and transmitted to the terminal station. You.

On the other hand, when the color detection signal Sc is detected and the relay broadcast detection signal St is not detected, the image information stored in the image information storage section 42 is read out to the decoding section 44 and the image information is read out. The information is further output to the printer 45 to form a print image.

If no color instruction is detected, a normal monochrome image receiving operation is performed. That is, the received image information is transmitted through the transmission unit 43 or decoded by the decoding unit 44 and output to the printer 45. In the broadcast of a black-and-white image, the stored image information may be temporarily decoded and then encoded according to the terminal station (the dotted line in the figure).

[0044]

As is clear from the above description, according to the present invention, when relaying a color image, the transmission image is relayed to the terminal station together with the quantization table without being decoded by the relay station. The terminal station can decode the image information using the relayed quantization table. As a result, it is possible to avoid repetition of quantization / inverse quantization, which is an irreversible process, so that deterioration of transmission image information can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of main functions of a facsimile apparatus showing one embodiment of the present invention.

FIG. 2 is a block diagram of a hardware configuration (No. 1) of the facsimile apparatus showing one embodiment of the present invention.

FIG. 3 is a block diagram of a hardware configuration (part 2) of the facsimile apparatus showing one embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of the relay station.

FIG. 5 is a flowchart showing an operation of a conventional relay station.

FIG. 6 is a diagram showing an example of a session start response RSSP.

FIG. 7 is a diagram showing an example of a document capability list CDCL.

FIG. 8 is a block diagram illustrating data processing including a lossy encoding method.

[Explanation of symbols]

40: receiving unit, 41: instruction station instruction discriminating unit, 42: image information storage unit, 43: transmitting unit, 44: decoding unit

Continuation of the front page (72) Inventor Ken Umezawa 3-7-1, Funai, Iwatsuki-shi, Saitama Fuji Xerox Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/46-1 / 64 H04N 1/32

Claims (1)

(57) [Claims] 1. A color still image communication apparatus for performing relay broadcasting of image information encoded by a lossy encoding method, wherein a protocol instruction received from an instruction station includes a color instruction and a relay broadcasting instruction. Means for determining whether or not there is a color instruction and a relay broadcast instruction. Means for transmitting the received quantization table to the terminal station.