JPH08214171A - Image communication equipment and its method - Google Patents

Abstract

PURPOSE: To realize the image communication equipment and its method in which image data for each color component are reproduced through transmission of a small information quantity. CONSTITUTION: Representative color information sets Ri, Gi, Bi are outputted to a code synthesis section 109 based on frequency distribution of colors of received color image data in a frequency distribution generating section 103 and the information is added to coding data of a luminance signal and the resulting data are transmitted. In the case of reception, the code synthesis section 109 separates the representative color information and the result is given to a color space conversion section a106. The color space conversion section a106 generates each of RGB color components based on the representative color information from the decoded luminance signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image communication apparatus and method thereof, for example, an image communication apparatus capable of color image communication and method thereof.

[0002]

2. Description of the Related Art In recent years, the development of image communication apparatuses capable of transmitting and receiving images such as facsimile machines has been remarkable. For example, even if the original image to be transmitted is a color image, by separating the luminance component and transmitting it,
An image communication device capable of obtaining a monochrome image corresponding to a color original document on the receiving side has also been developed.

An example of the block configuration of the conventional image communication apparatus as described above is shown in FIG. 7 and its operation will be described below.

In FIG. 7, reference numeral 101 indicates a red (R), green (G), and blue (B) reading a color original.
, A color image reading unit for outputting the image signal of 102, a monochromatic conversion processing unit 102 for converting the RGB signal into a luminance signal,
Reference numeral 104 is a JPEG encoding unit that performs encoding and decoding according to the JPEG baseline encoding method, and 105 is a line control unit that connects the image communication apparatus to a communication line to control the line, and also transmits / receives encoded data. , 106 is a color space conversion unit a for converting a luminance signal into an RGB signal, and 107 is RGB
Signals are cyan (C), magenta (M), yellow (Y)
The color space conversion units b and 108 for converting into a signal represented by
An image output unit such as a printer that prints out image data represented by the MY signal.

A transmission / reception process in the conventional image communication apparatus having the above-mentioned structure will be described below.

First, the operation during transmission will be described. At the time of transmission, first, a color original is read by the color image reading unit 101, and 8-bit image data of each color of RGB is output. R output from the color image reading unit 101
The GB color image signal is converted into a luminance signal in the monochromatic conversion processing unit 102. The conversion from the RGB signal to the luminance signal in the monochromatic conversion processing unit 102 is performed by the following equation (1) where the luminance signal is L.

L = 0.2990 × R + 0.5870 × G + 0.1140 × B (1) The image signal converted into the luminance signal L by the monochromatic conversion processing unit 102 is input to the JPEG encoding unit 104, and is well known. JPE
G baseline coding is performed. Then, the encoded data output from the JPEG encoding unit 104 is transmitted to the communication line via the line control unit 105.

Next, the operation at the time of reception will be described. At the time of reception, the line control unit 105 inputs the received data from the communication line. Here, it is assumed that the received data is the luminance signal L encoded by JPEG. The received data is input to the JPEG encoding unit 104, decoded into a luminance signal L by a known JPEG decoding process, and the color space conversion unit a1.
It is input to 06. The color space conversion unit a106 generates an RGB signal from the luminance signal L, and the formula of color space conversion in the conventional color space conversion unit a106 is shown in Formula (2).

R = L, G = L, B = L (2) As can be seen from the equation (2), in the conventional color space conversion, all values of R, G, and B are the same as those of the luminance signal L. The value itself was substituted.

The RGB signal generated by the color space conversion unit a is then input to the color space conversion unit b107 and converted into a CMY signal by referring to a look-up table (hereinafter referred to as LUT). The received image is printed out from the image output unit 108 by the CMY signal obtained as described above,
The reception process has ended.

[0011]

As described above, in the conventional image communication apparatus, since the color original is transmitted as the monochromatic image data having only the luminance component, the receiving side can reproduce the color difference component. There wasn't. Therefore,
There is a problem that the printout of the received image can be performed only in achromatic color.

Of course, a color image can be reproduced by transmitting and receiving all the R, G, and B color components, but the communication amount and communication time become enormous, which is not practical in terms of cost. Absent.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an image communication apparatus and method capable of transmitting a small amount of information and reproducing image data for each color component. To aim.

[0014]

In order to achieve the above-mentioned object, the present invention comprises the following constitutions.

That is, a monochromatic converting means for converting a color image signal into a monochromatic signal, a representative color determining means for determining a representative color of the color image signal, and a code for encoding the monochromatic signal converted by the monochromatic converting means. An encoding unit, a combining unit for adding the representative color information to the encoded data by the encoding unit to generate transmission information, a transmitting unit for transmitting the transmission information generated by the combining unit, and the transmitting unit. Receiving means for receiving the transmitted transmission information, separating means for separating the transmission information received by the receiving means into encoded data and representative color information, and decoding the encoded data separated by the separating means. Decoding means for obtaining a monochrome signal, and a color converter for converting the monochrome signal decoded by the decoding means into a color image signal based on the representative color information separated by the separating means. Characterized in that it has a conversion means.

For example, the representative color determining means determines the representative color based on a color frequency distribution of the color image signal.

For example, the monochrome conversion means calculates a luminance signal from at least two elements of the color image signal to obtain a monochrome signal.

For example, the monochrome conversion means calculates a luminance signal from the three color components of the color image signal to obtain a monochrome signal.

For example, the color image conversion means is characterized by calculating three color components of the color image signal from the monochromatic signal to obtain a color image signal.

For example, the color image conversion means calculates the three color components from the single color signal according to the respective ratios of the three color components of the representative color.

For example, the synthesizing means adds the representative color information as annotation information of the encoded data.

For example, the synthesizing means adds the representative color information as application attribute information of the encoded data.

Further, it is characterized by further comprising image input means for inputting the color image signal.

Further, it is characterized by further comprising image output means for outputting the color image signal converted by the color image conversion means.

[0025]

With the above configuration, when a color image is transmitted as a single color signal, representative color information which is the most characteristic color of the color image is added and transmitted. Then, it is possible to obtain a unique effect that each color component can be generated based on the representative color information from the received monochromatic signal.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings.

<First Embodiment> FIG. 1 shows a block configuration of an image communication apparatus according to the present embodiment, and the operation thereof will be described with reference to FIG.

In FIG. 1, the same components as those of FIG. 7 shown in the above-mentioned conventional example are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, a frequency distribution generation unit 103 determines the representative color of the read image by generating the frequency distribution of the color from the RGB signal of the original image input by the color image reading unit 101. And output. A code synthesizing unit 109 synthesizes or separates the coded data and the representative color signal in this embodiment as described later.

Next, the transmission operation of the image communication apparatus of this embodiment having the above-mentioned structure will be described.

First, the color image reading unit 101 reads a color original document and outputs 8-bit data of each color of RGB. The RGB color image signals output from the color image reading unit 101 are input to the monochromatic conversion processing unit 102 and the frequency distribution generation unit 103. In the monochromatic conversion processing unit 102, the input RGB signal is converted into a luminance signal. The conversion from the RGB signal to the luminance signal L in the monochromatic conversion processing unit 102 is performed according to the equation (1) shown in the above-mentioned conventional example.

The luminance signal L output from the monochromatic conversion processing unit 102 is input to the JPEG encoding unit 104. JP
The EG encoding unit 104 performs JPEG baseline encoding on the input luminance signal L. Below, JP
The encoding process in the EG encoding unit 104 will be described with reference to the flowchart in FIG.

In the JPEG encoder 104, the input luminance signal L is first subjected to raster block conversion in step S201, and the luminance signal L is divided into 8 × 8 pixel block units. Then, the luminance signal L is obtained by performing the DCT process (step S202), the quantization process (step S203), the zigzag scan (step S204), and the Huffman coding (S205) in this order.
JPEG encoded data of is generated. And JPE
The encoded data generated by the G encoding unit 104 is
It is input to the code synthesis unit 109.

On the other hand, the frequency distribution generator 103 uses the upper 4 bits of each color of the input RGB signal for the R
Generate a GB signal frequency distribution. Therefore, as the frequency distribution group obtained in the frequency distribution generation unit 103,
For example, if the B-th power of A is represented by A ^ B, there are (2 ^ 4) ^ 3 ways,
That is, it is considered that there can be 4096 groups.

Here, FIG. 5 shows an example of a table showing the frequency distribution groups obtained in the frequency distribution generation unit 103. In FIG. 5, the value of each item of R, G, B is a binary value, and the value of “X” is indefinite, that is,
“X” indicates that the value is either “0” or “1”. Then, the "number of pixels" at the right end of the table shown in FIG.
In the column, the number of pixels actually appearing for each group is counted.

Then, when the counting of all the pixels constituting the input image is completed, the frequency distribution is excluded except for the color range judged to be the background of the original document based on the obtained frequency distribution result. The RGB value that is the peak value of is determined. Then, the peak value is output as a representative value of colors in the input image (hereinafter referred to as representative color). That is, FIG.
The group in which the “number of pixels” in the table shown in (6) is the maximum except for the background is the representative color. To determine the background color of the original image, the operator may input the range of the background color from an operation panel (not shown), or the peak value in the luminance signal obtained by the monochromatic conversion processing unit 102 may be used as the background. You may judge. Further, it is not always necessary to determine the representative value of the color from all the pixels of the input image, and it may be determined from the optimum number of pixels according to the performance of the image communication device, required accuracy, and the like. .

Then, the representative color signal output from the frequency distribution generation unit 103 is input to the code synthesis unit 109. The code synthesizing unit 109 adds the input representative color signal to the input JPEG encoded data and outputs it.

The format for adding the representative color signal in the code synthesizing unit 109 is shown in FIG. 3 and will be described in detail. In FIG. 3, “COM” is a comment marker code indicating the annotation information, and is “FFF” in hexadecimal notation.
It has a value indicated by "E". In this embodiment, it is used to identify the start of the representative color signal. “Lc” is the application segment length, and the length is “000
5 ”. In addition, "Cm1", "Cm2", "Cm
3 ”is Ri, G which is the RGB value in the representative color signal.
i and Bi are stored respectively.

As described above, the code synthesizing unit 109
The encoded data output from is transmitted to the communication line via the line control unit 105, and the transmission process in this embodiment ends.

Next, the operation at the time of reception in this embodiment will be described. The coded data received from the communication line is input to the code synthesis unit 109 by the line control unit 105, and the JPEG coded data and the representative color signals Ri, Gi, Bi are separated by the COM marker.

JP separated by the code synthesizing unit 109
The EG encoded data is input to the JPEG encoding unit 104 and decoded into the luminance signal L. Hereinafter, the decoding process in the JPEG encoding unit 104 will be described with reference to the flowchart in FIG.

In the JPEG encoding unit 104, first, in step S401, the Huffman decoding process is performed on the received JPEG encoded data. And 8x8
The pixel block is restored (step S402), inverse quantization (step S403), and IDCT processing (step S4).
04) and the block raster conversion (step S405) are performed in this order to decode the JPEG encoded data and obtain the luminance signal L.

The decoded luminance signal L is stored in the color space conversion unit a.
It is input to 106 and converted into an RGB signal. On the other hand, the representative color signals Ri, Gi, B separated by the code synthesis unit 109
i is also input to the color space conversion unit a106, and the color space conversion in the color space conversion unit a106 is shown in (3) below.
Follow the formula.

R = L × Ri / (Ri + Gi + Bi) G = L × Gi / (Ri + Gi + Bi) (3) B = L × Bi / (Ri + Gi + Bi) As can be seen from the formula (3), in the present embodiment, Each RGB value to be converted is calculated from the received luminance signal L and representative color signals Ri, Gi, Bi.

The RGB signal generated by the color space conversion unit a based on the equation (3) is next input to the color space conversion unit b107 and converted into a CMY signal by referring to the LUT. Here, an example of the LUT in the color space conversion unit b107 is shown in FIG. According to the LUT shown in FIG. 6, R → C,
Conversion of G → M and B → Y is performed. The LU shown in FIG.
Although the linear conversion is performed in the example of T, the characteristics of the image output unit 108 can be included in the LUT, for example. Alternatively, the conversion may be performed using an n-th order matrix.

The received image is printed out from the image output unit 108 by the CMY signal obtained as described above, and the receiving process in this embodiment is completed.

As described above, according to this embodiment, the color image data is converted into the image data of the luminance component,
By adding representative color information, encoding and transmitting,
The receiving side can reproduce image data for each of the RGB color components. That is, since a color image can be reproduced by transmitting / receiving almost monochromatic information, the communication time and communication cost are almost 1/3 compared with the case of transmitting all three components.
Can be reduced to Further, compared to the case where only the luminance component is transmitted, the code data amount only increases by 7 bytes, and the color information can be efficiently added.

<Second Embodiment> In the first embodiment described above,
As an example of the method of generating the monochromatic image data (luminance component) in the monochromatic conversion processing unit 102, the example using the equation (1) is described. However, the present invention is not limited to this example, and in the second embodiment, an example using equation (4) shown below will be described.

The configuration of the image communication apparatus of the second embodiment is the same as that of the above-mentioned first embodiment, and the explanation thereof will be omitted.

In the second embodiment, the monochromatic conversion processing unit 102 produces the monochromatic image signal K based on the following equation (4).

K = (R × Ri + G × Gi + B × Bi) / (Ri + Gi + Bi) (4) Then, the luminance signal L in the above-described first embodiment will be described below.
Similarly to the case of 1, the JPEG encoding unit 104 performs JPEG encoding on the monochromatic image signal K, adds the representative color signal output from the frequency distribution generating unit 103, and transmits the signal.

Then, when the image signal transmitted as described above in the second embodiment is received, the monochromatic image signal K is decoded in the JPEG encoding unit 104 as in the first embodiment, and the representative signal is obtained. The color signals Ri, Gi, Bi are extracted. Then, the color space conversion unit 106 generates an RGB signal from the monochromatic image signal K. As the color space conversion method, the following expression (5) is used instead of the above expression (2).

R = K × Ri / (Ri + Gi + Bi) G = K × Gi / (Ri + Gi + Bi) (5) B = K × Bi / (Ri + Gi + Bi) Then, similar to the first embodiment described above, The RGB signal obtained by the equation (5) can be converted into a CMY signal and output.

As described above, according to the second embodiment,
It is possible to emphasize the representative color in the color original to be read and send it.

<Other Embodiments> First and second embodiments described above
In the embodiment, the example in which the COM marker is used as the identification information when the representative color signal is added to the encoded data at the time of transmission has been described. However, the present embodiment is not limited to this example, and instead of the COM marker, for example, the APPn marker indicating the application attribute information added to the image data, such as the start of the representative color signal in the JPEG encoded data. Any code may be used as long as it can be identified. Of course, a dedicated code indicating the start of the representative color signal may be defined.

Although the color image reading unit 101 has been described as inputting an image signal by scanning a color original, the present invention is not limited to this example, and an image signal from a host computer, for example, is used. , And so on, as long as an image signal can be input.

Furthermore, although an example of inputting a color image has been described, the present invention can be applied even if the input image is a monochrome image. In this case, the image output unit 108 can output an achromatic image. it can.

Although the image output unit 108 has been described as a configuration for performing print output by a printer or the like, a CRT, an external storage medium, or the like may be used as long as it has an image output configuration. However, the final image output such as CRT is RG.
Needless to say, when the B signal is used as it is, the color space conversion unit b107 can be omitted. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0059]

As described above, according to the present invention, color image data is converted into monochromatic image data, representative color information is added, and the image data is transmitted. The data can be reproduced. That is, since a color image can be reproduced by transmitting / receiving information of almost a single color, compared with the case of transmitting all three components,
The communication time and communication cost can be reduced to almost 1/3. Also, the amount of code data only increases by 7 bytes compared to the case where only the luminance component is transmitted,
It is possible to efficiently add color information.

Further, it is possible to emphasize the representative color of the read color original document and transmit it.

[0061]

[Brief description of drawings]

FIG. 1 is a diagram showing a block configuration of an image communication apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an encoding process in this embodiment.

FIG. 3 is a diagram showing a format when a representative color signal is added in the present embodiment.

FIG. 4 is a flowchart showing a decoding process in this embodiment.

FIG. 5 is a diagram showing an example of frequency distribution groups in the present embodiment.

FIG. 6 is a diagram showing an example of an LUT for converting an RGB signal into a CMY signal in the present embodiment.

FIG. 7 is a diagram showing a block configuration of a conventional image communication device.

[Explanation of symbols]

 101 color image reading unit 102 monochromatic conversion processing unit 103 frequency distribution generation unit 104 JPEG encoding unit 105 line control unit 106 color space conversion unit a 107 color space conversion unit b 108 image output unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 11/04 Z 9185-5C G06F 15/66 310

Claims (18)

[Claims] 1. A monochromatic conversion unit that converts a color image signal into a monochromatic signal, a representative color determination unit that determines a representative color of the color image signal, and a code that encodes the monochromatic signal converted by the monochromatic conversion unit. Encoding means, combining means for adding the representative color information to the encoded data by the encoding means to generate transmission information, transmitting means for transmitting the transmission information generated by the combining means, and the transmitting means Receiving means for receiving the transmitted transmission information, separating means for separating the transmission information received by the receiving means into encoded data and representative color information, and decoding the encoded data separated by the separating means. Decoding means for obtaining a monochrome signal, and a color converter for converting the monochrome signal decoded by the decoding means into a color image signal based on the representative color information separated by the separating means. Image communication apparatus comprising: the converting means. 2. The image communication apparatus according to claim 1, wherein the representative color determining unit determines the representative color based on a color frequency distribution of the color image signal. 3. The image communication apparatus according to claim 1, wherein the monochromatic conversion means calculates a luminance signal from at least two elements of the color image signal to obtain a monochromatic signal. 4. The image communication apparatus according to claim 3, wherein the monochromatic conversion unit calculates a luminance signal from the three color components of the color image signal to obtain a monochromatic signal. 5. The image communication apparatus according to claim 1, wherein the color image conversion means calculates the three color components of the color image signal from the single color signal to obtain a color image signal. 6. The color image conversion means converts 3 from the single color signal according to a ratio of each of the three color components of the representative color.
The image communication apparatus according to claim 1, wherein a color component is calculated. 7. The image communication apparatus according to claim 1, wherein the synthesizing unit adds the representative color information as annotation information of the encoded data. 8. The image communication apparatus according to claim 1, wherein the synthesizing unit adds the representative color information as application attribute information of the encoded data. 9. The image communication apparatus according to claim 1, further comprising image input means for inputting the color image signal. 10. The image communication apparatus according to claim 1, further comprising image output means for outputting the color image signal converted by the color image conversion means. 11. A monochromatic conversion step of converting a color image signal into a monochromatic signal, a representative color determination step of determining a representative color of the color image signal, and a code for encoding the monochromatic signal converted by the monochromatic conversion step. An encoding step, a combining step of adding the representative color information to the encoded data by the encoding step to generate transmission information, a transmitting step of transmitting the transmission information generated by the combining step, and a transmitting step A receiving step of receiving the transmitted transmission information, a separation step of separating the transmission information received by the receiving step into encoded data and representative color information, and decoding the encoded data separated by the separating step. A decoding step of obtaining a monochromatic signal, and a converter for converting the monochromatic signal decoded by the decoding step into a color image signal based on the representative color information separated by the separating step. Image communication method characterized by having a chromatography converting step. 12. The image communication method according to claim 11, wherein the representative color determining step determines the representative color based on a color frequency distribution of the color image signal. 13. The image communication method according to claim 11, wherein the monochrome conversion step calculates a luminance signal from at least two elements of the color image signal to obtain a monochrome signal. 14. The image communication method according to claim 13, wherein in the monochromatic conversion step, a luminance signal is calculated from three color components of the color image signal to obtain a monochromatic signal. 15. The image communication method according to claim 11, wherein in the color image conversion step, three color components of the color image signal are calculated from the single color signal to obtain a color image signal. 16. The image communication method according to claim 11, wherein the color image conversion step calculates three color components from the single color signal according to a ratio of each of the three color components of the representative color. 17. The image communication method according to claim 11, wherein in the combining step, the representative color information is added as annotation information of the encoded data. 18. The image communication method according to claim 11, wherein in the combining step, the representative color information is added as application attribute information of the encoded data.