JPH03265365A - Picture communication equipment - Google Patents

Abstract

PURPOSE:To prevent the transmission of an n-value picture data not acceptable to a receiver side by sending the n-value data to be sent when the receiver side is able to accept the data. CONSTITUTION:In the case of transmission of an m-value picture data while being compressed into n-value picture data (m>n), whether or not a receiver side is able to cope with the n-value compression method is identified. That is, a scanner section 1 reads a color picture, a binarization section 2 applies binary processing to 256 gradation of picture data R, G, B, the result is sent to an encoding section 3, in which the encoding method such as MMR and MR is encoded and the picture information is sent to a communication control section 4. The communication control section 4 makes communication with a receiver, and whether or not the binarizing method of the sender side is acceptable by the receiver side is identified, and only when the picture is acceptable, the transmission is implemented. Thus, the transmission of the n-value picture data not acceptable to the receiver side is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image communication device that transmits color image information and the like.

[Prior Art] Various color facsimile devices that communicate color images have been proposed in the past.
R),,! Since the three color information of (R) and blue (B) each has 256 gradations from θ to 255, the data capacity is much larger than that of a black and white image, and the communication time is longer. It has been extremely difficult to put into practical use a device that transmits multivalued information as it is.

[Problems to be Solved by the Invention] Therefore, as a method of compressing the data capacity of a color image, each data of R, G, and B is divided into 25
Binaryization from 6 gradations to 2 gradations of 0 and 1, and further MMR
, MR, and other conventional facsimile encoding methods have been proposed.

However, when a color-binary image is received, color-processed, and printed out, the colors differ depending on the type of binarization method used when converting the original multi-valued image into a binary image, and the color image is different from the one you tried to send. An inconvenience arises in that images of different colors are printed out on the receiving device side.

For example, for an image that has been binarized using the Bayesian dither method, a receiving device that has been adjusted to reproduce appropriate colors may be binarized using the Bayesian dither method.
There is a drawback that when digitized image data is transmitted, the color of the image to be transmitted is different from the color of the image printed out by the receiving device.

The present invention aims to appropriately deal with color differences between the sending side and the receiving side that occur depending on the type of n-value conversion method when an m-value image is converted into n-value images (m>n) and transmitted. The purpose of the present invention is to provide an image communication device that can perform the following functions.

[Means for solving the problem] The present invention converts m-value image data into n-value image data (man).
In an image communication device that compresses and transmits the n
The present invention is characterized in that when transmitting value image data, it is determined whether or not the receiving side is compatible with the n-value compression method of the image data, and the transmission is performed when it is compatible.

[Operation] In the present invention, when transmitting n-value image data, it is determined whether the receiving side is compatible with the n-value compression method of the image data, and transmission is performed when it is compatible with the n-value compression method of the image data. It is possible to prevent the transmission of n-value image data that the other side cannot handle.

Furthermore, it is possible to select and transmit a compatible n-value compression method, thereby ensuring proper reproduction of an m-value image on the receiving side.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

This image communication device includes a scanner section l that reads a color image on a document, a binarization section 2 that binarizes the color image data input from the scanner section 1, and an MMR for this binarized data. , MR, etc., a communication control unit 4 that communicates with other image communication devices through a telephone line or ISDN network, and sends and receives encoded data, and a communication control unit 4 that transmits and receives encoded data. It has a decoding section 5 for decoding, an image processing section 6 for processing image data in accordance with the characteristics of a printer section 7, and a printer section 7 for printing out the image data.

FIG. 2 is a block diagram showing the configuration of the binarization section 2. As shown in FIG.

The binarization unit 2 in this embodiment uses the Bayer dither method,
Four types of binarization means 21 to 2 that perform binarization using the fattening dither method, error diffusion method, and simple binarization method
These four types of binarization means 21
In addition to selecting 24 to binarize the image data, it is also possible to send the image data to the encoding unit 3 without binarizing the image data.

FIG. 3 is a block diagram showing the configuration of the image processing section 6. As shown in FIG.

The image processing unit 6 according to this embodiment uses the Baye raw dither method,
It has four types of image processing means 61 to 64 corresponding to four types of binarization methods: the Fat-Jung dither method, the error diffusion method, and the simple binarization method. It has an image processing means 65.

The image processing section 6 selects these image processing means 61 to 64, performs image processing on the encoded image data, and sends the encoded image data to the printer section 7.

FIG. 4 is a flowchart showing an outline of the operation at the time of transmission, and FIG. 5 is a flowchart showing an outline of the operation at the time of reception.

First, at the time of transmission, the scanner unit l reads a color image, and for example, for each dot of 400 dpi, 256 gradation data of R, G, and H (0 to 25
5) is sent to the binarization unit 2 (Sl). Next, the binarization unit 2 converts each of the 256 gradations of R, G, and B of the color image data into 2
The data is converted into a value and sent to the encoder 3 (S2).In this way, the scanner unit 1 needs 8 bits each for R, G, and H for each dot, that is, a total of 24 bits. On the other hand, by binarizing, only 1 bit is required for each of R, G, and H, that is, 3 bits in total, and the data is compressed to 1/8.

Next, the encoding unit 3 encodes the image information using an encoding method such as MMR or MR, and sends the image information to the communication control unit 4 (S3). Send method information and image information to the receiver (S4)
.

On the other hand, in FIG. 5, when the communication control unit 4 receives information regarding the binarization method and image information (S11)
, The received image information is sent to the decoding unit 5, decoded by the decoding unit 5, and sent to the image processing unit 6 (S12). Image processing is performed according to the information (S13), and the image is sent to the printer section 7 and printed out (S14).

By the way, many methods have been proposed as methods for binarizing multivalued images, but each has its advantages and disadvantages, and the two methods are considered optimal in all cases and from all points of view.
No valuation method has been proposed.

Typical binarization methods include (1) Bay medium dither method;
(2) Fat Jung dither method, (3) error diffusion method,
(4) There is a simple binarization method, but the Baye medium dither method and the Fat-Jung dither method both compare the image and a threshold matrix, and if the image data is larger than the corresponding threshold, "l" , if it is smaller, it is set to "0".

FIG. 6 is an example of a threshold matrix for the Bay medium dither method, and FIG. 7 is an example of a threshold matrix for the Fat-Jung dither method.

A feature of the Bay medium dither method is that when binarized using this method, the dots tend to be dispersed, and a feature of the Fat-Jung dither method is that, conversely, the dots tend to concentrate.

FIGS. 8 and 9 are examples of image data when a flat image with a brightness of 160 is binarized using each method,
The "0" data part, that is, the dark part, is dispersed when binarized using the Bay medium dither method, whereas it is concentrated when using the fattening method.

When such two binary images are printed using, for example, an inkjet printer, the images will be quite different due to the influence of ink bleeding.

In other words, in an image binarized using the Bay medium-sized dither method, the dark areas, that is, the dots that hit the ink, are dispersed, so the ink smear is large, whereas in an image binarized using the Fat-Jung dither method, there is a large amount of ink bleeding. , because the dots are concentrated, the ink smear is small.

As a result, the image binarized using the Bay medium dither method is darker than that obtained using the Fat-Jung dither method.

In this way, if the same image processing is performed on images that have been binarized using different binarization methods, the colors will be different, so in order to obtain the optimal color image, it is necessary to It is necessary to perform image processing that is compatible with the above.

In this embodiment, as the binarization method, the Bay medium dither method,
The Fat-Jung dither method, error diffusion method, and simple binarization method are possible; in general, when the resolution is low, the Baye raw dither method provides a good image, and when the resolution is high, the Fat-Jung dither method can be used. Good images can be obtained using the dither method.

In addition, the dither method is good for halftone images such as photographs, but is not suitable for images with clear shading such as text images.Furthermore, the error diffusion method The simple binarization method has the disadvantage of large capacity, and tends to be unsuitable for halftone images.

Therefore, in this embodiment, at 52 in FIG. 4 above,
The binarization method is selected by the operator, or by automatic determination based on resolution, text mode or photo mode, or communication with the receiver.

In addition, in this embodiment, the method of binarizing the transmitted data on the transmitting side and the binarizing method that can be applied when image processing the received data on the receiving side are expressed by predetermined codes, and these are expressed as the above-mentioned code. As information regarding the binarization method, the other party'IIt! By transmitting and receiving the code information to and from 1, the binarization means 21 to 24 and the image processing means 61 to 65 are selected with reference to this code information.

FIG. 1O is a schematic diagram showing code information for the four types of binarization methods described above.

In this embodiment, a 4-bit code corresponds to each binarization method. However, as described above, codes are assigned even when binarization is not performed. By sending such code information to the partner device when transmitting image information, it is possible to identify the binarization method of the image information.

Further, FIG. 11 is a schematic diagram showing code information for notifying a partner device of the binarization method possessed by one image communication device.

This code information is obtained by taking the logical sum of the codes shown in FIG. can.

Furthermore, in this embodiment, when receiving image data, the code information representing the binarization method that the image processing section 6 can handle is also the same as the code information shown in FIG. 11.

Note that the code information shown in FIG.
shall be registered in a predetermined memory area.

FIGS. 12 and 13 are flowcharts showing operations when identifying whether or not the transmitting side's binarization method is compatible with the receiving side using a code indicating such a binarization method. , FIG. 12 shows the operation of the transmitter, and FIG. 13 shows the operation of the receiver.

First, the communication control unit 4 notifies the receiver of the code indicating the binarization method using a predetermined procedure signal (521).
.

That is, if the receiver is an image communication device compliant with 03 facsimile, a code indicating the binarization method is transmitted to the receiver using an initial identification signal of a non-standard function, for example, specific 4 bits of No. N518. Is possible.

In addition, if the receiver is an image communication device compliant with 04 facsimile, the user
It is possible to use four specific bits of the user signal to transmit a code indicating the binarization method to the receiver.

On the other hand, the receiver receives specific 4 bits of the above-mentioned NSF signal or user signal (531), and decodes this to identify the binarization method (S32).

Then, if the receiver is compatible with the binarization method (S33), it transmits the binarization code as an NSF signal or a user-user signal (534), and if it is not compatible with the binarization method, the receiver Binarized code other than encoded code is N
By transmitting an SF signal or a user-to-user signal (S35), it is notified whether or not support is possible.

Therefore, the sender receives the NSF signal or the user-to-user signal from the sender (522), identifies the specific 4 bits (S23), and determines the method for binarizing the transmitted binary code. It is determined whether the receiver is capable of responding to the request (S24.525).

After that, if the transmitter identifies that the receiver is compatible, the transmitter uses the binarization means corresponding to the binarization method to binarize the receiver.
The converted image data is transmitted (S26).

In addition, as an operation when the receiver is not compatible, in S35 above, a code (in this embodiment, the first
It is possible to transmit t t 11) shown in FIG. 1 by an NSF signal or a user-to-user signal.

At this time, the transmitter can identify the binarization method that the receiver can handle by identifying the specific 4 bits of the NSF signal or the user-to-user signal. By comparing and selecting a binarization method that is compatible with the receiver and the transmitter, binarization is performed using a binarization method that the receiver can handle, and the above-mentioned transmission operation converts the binarization method and the image. data and can be sent to the receiver.

When the communication control unit 4 on the receiving side identifies the binarization method from the other party, it transmits this binarization method to the decoding unit 5 and the image processing unit 6.The image processing unit 6 uses the transmitted binarization method. The corresponding image processing means is selected, the received image data is subjected to image processing, and sent to the printer section 7 to be printed out.

Note that by transmitting and receiving the above-mentioned code information to and from a specific image communication device in advance, the communication control unit 4
The binarization method possessed by the other party's image communication device and the compatible binarization method are registered in the memory area of , and the binarization means 21 to 24 and the image processing means 61 to 6
Alternatively, for a partner device that cannot be registered in advance, the communication protocol can be used when transmitting and receiving image information as described above.

FIG. 14 is a block diagram showing another example of the configuration of the image processing section.

More specifically, this image processing section includes a multi-value conversion section 71, a density conversion section 72, a masking section 73, a γ correction section 74, and a binary conversion section 75.

The multi-value conversion unit 71 performs multi-value conversion by smoothing processing. FIGS. 15 and 16 show examples of the configuration of a smoothing filter for image data that has been converted into a binary image using, for example, the Bay medium dither method and the fattening dither method. FIG.

In this way, by changing the multi-value conversion method depending on the type of the transmitted binary signal, a high-quality image signal can be obtained. Also, for example, for data that has been binarized by the error diffusion method, the window applied to the binary data may be moved continuously, and for data that has been binarized by the dither method, the window applied to the binary data may be moved continuously. , the window may not be moved continuously but may be moved intermittently.

The density converter 72 searches the lookup table to convert the density (cmy
) The looker 2 variables that perform the conversion into data may be different or the same depending on each binarization method.

The masking unit 73 performs masking processing to correct cloudiness of ink in the printer unit 7.

The γ correction unit 74 performs γ correction according to the characteristics of the printer unit 7, and the binary conversion unit 75 performs γ correction for printer output.
Perform value conversion.

The above masking section 73, γ correction section 74, and binary conversion section 75 may be different depending on each binarization method, or may be the same, or may have different masking parameters depending on each binarization method. The circuit is common, and only the parameters can be changed.

The image processing unit identifies the binarization method of the received image and converts it to each of the above-mentioned image processing means 61 to 65 or the multi-value conversion unit 71.
．． By selecting the density conversion section 72, masking section 73, gamma correction section 74, and binary conversion section 75, optimal image processing can be performed.

Furthermore, FIGS. 17 and 18 are flowcharts showing other examples of the above-described transmission and reception operations, with FIG. 17 showing the operation of the transmitter and FIG. 18 showing the operation of the receiver.

In this embodiment, the transmitter transmits a binary code (3
41), when the receiver receives this (SSt), if the receiver is compatible with the binarization method (352),
The transmitter returns the binarization code 553), and if it is not applicable, returns the OR code indicating all the compatible binarization methods explained in FIG. 11 (S54). When receiving (S42), compare the transmitted binary code and the received binary code 543),
If they are the same, the image data should be binarized using that binarization method and sent (546); if they are not the same, it is determined whether there is a possible binarization method among the received binarization codes. If so, select the binarization method (S45), binarize the image data, and send it (S44).
S46), if not, the image data is transmitted without being binarized (S47).

Further, as another embodiment, the image processing section may be composed of a correction section that performs correction corresponding to each binarization method, and an image processing means common to each binarization method. As an example of correction corresponding to the value conversion method, there is a method in which a look-up table is prepared according to a 3×3 dot pattern centered on the pixel of interest, and a value is made to correspond to the pixel of interest.

Furthermore, rather than simply the Bayer dither method, the same Bayer dither method may be classified into more detailed compression methods, such as a 4×4 Bayer dither method or an 8×8 Bayer dither method.

Further, in the embodiment described above, the code indicating the z-value conversion method was transmitted to the receiver using a predetermined procedure signal, but it can also be transmitted by converting the first 4 bits of the image data into a binary code.

Furthermore, in the embodiment described above, binarization is performed as n-value compression, but not only binarization but also ternarization is performed.

It may also be 4-valued or the like.

Further, in the embodiment described above, image data is input from the scanner unit l, but it may be input from a video camera, a still video, or an image database instead of a scanner.

Further, in the embodiment described above, the image is output to the printer section 7, but it may be output to a CRT, an image database, or the like.

In addition, in the above embodiment, one image data includes R, G, B
Although it handles data, it may similarly handle x, y, z or L, a*, b skews representing color data, or even Y, I, and Q used in television signals.

Furthermore, in the embodiment, when transmitting n-value data,
In order to identify whether the receiving side is compatible with the n-value conversion method of image data, a method according to the G3 recommendation or a method according to the G4 recommendation may be used.
There are many variations of such protocols that may use code in the aforementioned layers of SDN.

[Effects of the Invention] As explained above, according to the present invention, transmission is performed when the receiving side can handle the n-value image data to be transmitted. transmission can be prevented.

Furthermore, it is possible to select and transmit a compatible n-value compression method, thereby ensuring proper reproduction of an m-value image on the receiving side.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the binarization section in the same embodiment. FIG. 3 is a block diagram showing the configuration of the image processing section in the same embodiment. FIG. 4 is a flowchart showing an overview of the operation at the time of transmission in the same embodiment. FIG. 5 is a flowchart showing an overview of the operation at the time of reception in the same embodiment. FIG. 6 is a schematic diagram showing an example of a threshold matrix for the Bayer dither method. FIG. 7 is a schematic diagram showing an example of a threshold matrix for the fattening dither method. FIG. 8 is a schematic diagram showing an example of image data when binarized using the Bayer dither method. FIG. 9 is a schematic diagram showing an example of image data when binarized using the fattening dither method. FIG. 10 is a schematic diagram showing code information for four types of binarization methods in the same embodiment. FIG. 11 shows two images that the image communication device has in this embodiment.
FIG. 3 is a schematic diagram showing code information for notifying a partner device of a value conversion method. FIG. 12 is a flowchart showing the operation of the transmitter when determining whether or not the binarization method is compatible with the receiving side in the same embodiment. FIG. 13 is a flowchart showing the operation of the receiver when determining whether or not the binarization method is compatible with the receiving side in the same embodiment. FIG. 14 is a block diagram showing another example of the configuration of the image processing section in another embodiment of the present invention. FIG. 15 is a schematic diagram showing a configuration example of a smoothing filter for the Bayer dither method in the same embodiment. FIG. 16 is a schematic diagram showing a configuration example of a smoothing filter for the Fang type dither method in the same embodiment. FIG. 17 is a flowchart showing the operation of a transmitter in still another embodiment of the present invention. FIG. 18 is a flowchart showing the operation of the receiver in the same embodiment. l... Scanner section, 2... Binarization section, 3... Encoding section, 4... Communication control section, 5... Decoding section, 6... Image processing section, 7. ... Printer section, 71... Multi-value conversion section, 72... Density conversion section, 73... Masking section, 74... γ correction section, 75... Binary conversion section. Figure 1

Claims (5)

[Claims] (1) In an image communication device that compresses m-value image data into n-value image data (m>n) and transmits the compressed image data, when transmitting the n-value image data, the
Identify whether the receiving side is compatible with the value compression method,
An image communication device characterized in that it transmits data when it is available. (2) In claim (1), when there are multiple types of n-value compression methods and the n-value compression method selected from among them is compatible with the receiving side,
An image communication device characterized in that it transmits image data compressed by n-values using a value compression method. (3) In claim (1), there are multiple types of n-value compression methods, from which the receiving side selects an n-value compression method that can be supported, and transmits the image data compressed by that method. An image communication device characterized by: (4) In claim (1), the transmitting side transmits information regarding the n-value compression method to the receiving side, and the receiving side identifies whether or not it is compatible with the received n-value compression method, An image communication device characterized by notifying a transmitting side of the identification result. (5) In claim (1), the m-value image data has 256 pixels each for red, green, and blue.
It is a color image consisting of values, and the above n-value image data is
An image communication device characterized in that the red, green, and blue are binary data compressed into binary images.