JP2906166B2 - Image communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to converting m-value image data into n-value image data (m>
The present invention relates to an image communication device that converts the data into n) and transmits the converted data to a receiving device.

2. Description of the Related Art Conventionally, various color facsimile apparatuses for communicating a color image have been proposed. For a color image, for example, information of three colors, red (R), green (R), and blue (B), Since each of them has 256 gradations of 0 to 255, the data capacity is much larger than that of a black and white image, and the communication time becomes longer. It was difficult.

[Problem 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 converted from 256 gradations of 0 to 255 to two gradations of 0 and 1. Binarization, MMR, MR
It has been proposed to perform encoding in a conventional facsimile.

However, when the color binary image is received and color-processed,
When printed out, the color differs depending on the type of binarization method when binarizing the original multi-valued image, and an image of a color different from the color image to be transmitted is printed out on the receiving device side. Occurs.

For example, image data binarized by a fatting dither method is transmitted to a receiving apparatus adjusted to reproduce an appropriate color for an image binarized by a Bayer dither method. In some cases, for example, there is a disadvantage that the color of the image to be transmitted is different from the color of the image printed out by the receiving device.

An object of the present invention is to enable good image communication by enabling image data that has been n-valued processed using an n-value processing method according to the function of a receiving device to be transmitted to the receiving device. And

It is another object of the present invention to make it possible to efficiently determine an n-value processing method.

Means for Solving the Invention According to the present invention, m-value image data is converted to n-value image data (m>
n) and converts the m-valued image data to n using a plurality of different n-value conversion methods in the image communication device that transmits the data to the receiving device.
Converting means capable of converting into value image data (m>n); identifying means for identifying an n-value processing method that can be supported by the receiving device by performing bidirectional communication with the receiving device;
Registering means for registering a result identified by the identifying means in a memory in association with the receiving apparatus, wherein a receiving apparatus in which the transmitting means transmits the n-value image data is registered in the memory In the case, the n-value processing method is determined based on the registered identification result, and the receiving device that transmits the n-value image data is not registered in the memory. Then, an n-ary processing method that can be supported by the receiving device is identified, and the n-ary processing method is determined based on the identification result.

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

The image communication apparatus includes a scanner unit 1 for reading a color image on a document, a binarizing unit 2 for binarizing color image data input from the scanner unit 1, and an MMR for the binarized data. , An encoding unit 3 that performs encoding such as MR,
A communication control unit 4 that communicates with another image communication device via a telephone line or an ISDN network to transmit and receive encoded data, and a decoding unit 5 that decodes the received encoded data.
And an image processing unit 6 for processing the image data in accordance with the characteristics of the printer unit 7, and a printer unit 7 for printing out the image data.

FIG. 2 is a block diagram showing a configuration of the binarizing section 2.

The binarizing section 2 in this embodiment includes four types of binarizing means 21 to 4 for performing binarization by a Bayer type dithering method, a fatning type dithering method, an error diffusion method, and a simple binarizing method.
24, and these four types of binarization means 21 to
In addition to binarizing the image data by selecting 24, it is also possible to send the image data to the encoding unit 3 without binarizing.

FIG. 3 is a block diagram showing the configuration of the image processing unit 6.

The image processing unit 6 according to this embodiment includes four types of image processing means 61 to 64 corresponding to four types of binarization methods, namely, a Bayer type dither method, a fatning type dither method, an error diffusion method, and a simple binarization method. And an image processing means 65 for an image of 256 gradations that is not binarized.

The image processing section 6 selects one of these image processing means 61 to 64, performs image processing on the encoded image data, and sends it 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 an operation at the time of reception.

First, at the time of transmission, the scanner unit 1 reads a color image and, for example, for each dot of 400 dpi,
R, G, B 256 gradation data (0-255)
It is sent to the value conversion unit 2 (S1). Next, the binarizing section 2 binarizes each of the 256 gradations of R, G, and B of the color image data and sends it to the encoding section 3 (S2). Thus, the scanner unit 1
Requires 8 bits for each of R, G, and B for each dot, that is, a total of 24 bits.
By quantifying, only one bit is required for each of R, G, and B, that is, only a total of three bits, and the data is compressed to 1/8.

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

On the other hand, in FIG. 5, when the communication control unit 4 receives the information on the binarization method and the image information (S11), it sends the received image information to the decoding unit 5 and decodes the received image information. Is sent to the image processing unit 6 (S12). In the image processing unit 6,
Image processing is performed according to the information on the binarization method received from the communication control unit 4 (S13), and sent to the printer unit 7 for printing out (S14).

By the way, many methods have been proposed as binarization methods for multi-valued images, but each has advantages and disadvantages, and in any case, no binarization method that is optimal from every viewpoint has been proposed. .

As typical binarization methods, there are (1) Bayer type dither method, (2) fatning type dither method, (3) error diffusion method, and (4) simple binarization method. In any of the fattening dither methods, the image is compared with a threshold matrix, and if the image data is larger than the corresponding threshold, the value is “1”. If it is smaller, it is set to "0".

FIG. 6 is an example of a threshold matrix of the Bayer type dither method, and FIG. 7 is an example of a threshold matrix of the fatning type dither method.

A feature of the Bayer-type dither method is that dots tend to be dispersed when binarized by this method, and a feature of the fatning-type dither method is that dots tend to concentrate on the contrary.

FIG. 8 and FIG. 9 are examples of image data when a flat image having a luminance of 160 is binarized by each method.
The portion of the "0" data, that is, the dark portion is dispersed when binarized by the Bayer dither method, whereas it is concentrated in the fatning type.

When such two binarized images are printed by, for example, an ink jet printer, the images are considerably different due to the influence of ink bleeding. That is, in the image binarized by the Bayer type dither method, dark portions, that is, dots to which ink is applied are dispersed, so that ink bleeding is large. Is concentrated, so ink bleeding is small. As a result, the image binarized by the Bayer dither method is darker than the fattening dither method.

As described above, if the same image processing is performed on an image binarized by a different binarization method, a different color is obtained. It is necessary to perform image processing conforming to.

In the present embodiment, as the binarization method, a Bayer dither method, a fatning dither method, an error diffusion method, and a simple binarization method are possible. In general, when the resolution is low, the Bayer dither method is used. When a good image is obtained and the resolution is high, a good image can be obtained by the fatning type dither method. Further, the dither method is good for a halftone image such as a photograph, but is not suitable for an image having a clear gradation such as a character image. Further, the error diffusion method has a disadvantage that the image itself is good but the data capacity after encoding is large.
The binarization method tends to be ineligible for halftone images.

Therefore, in the present embodiment, in S2 of FIG.
A binarization method is selected by an operator, automatic determination based on resolution, whether the mode is a text mode or a photo mode, or communication with a receiver.

Further, in this embodiment, a binarization method of transmission data on the transmission side and a binarization method that can cope with image processing of the reception data on the reception side are represented by predetermined codes, which are described above. By transmitting and receiving information regarding the binarization method to and from the partner device, the code information is referred to and the binarization methods 21 to 24 and the image processing means 61 to
There are 65 choices to make.

FIG. 10 is a schematic diagram showing code information for the above-described four types of binarization methods.

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

FIG. 11 is a schematic diagram showing code information for notifying the other device of the binarization method of the image communication device.

This code information is obtained by calculating the logical sum of the codes shown in FIG. 10, and by sending this to the partner device, it is possible to display what kind of binarization method the image communication device has. it can.

In this embodiment, when receiving image data,
The code information representing the binarization method that can be supported by the image processing unit 6 is the same as the code information in FIG.

The code information shown in FIG.
Registered in a predetermined memory area.

FIG. 12 and FIG. 13 are flow charts showing the operation in the case of using the code indicating the binarization method to identify whether the binarization method on the transmission side is compatible with the reception side. FIG. 12 shows the operation of the transmitter, and FIG. 13 shows the operation of the receiver.

First, the communication control unit 4 notifies a code indicating the binarization method to the receiver by a predetermined procedure signal (S2
1).

That is, if the receiver is an image communication device conforming to the G3 facsimile, the initial identification signal of the non-standard function, for example,
It is possible to transmit a code indicating the binarization method to the receiver using specific 4 bits of the NSF signal.

If the receiver is an image communication device conforming to G4 facsimile, TTC recommendation, ISDN network interface 3
It is possible to transmit a code indicating the binarization method to the receiver by using specific 4 bits of the user signal shown in Section 3, Layer 3 specification 4.5.24.

On the other hand, the receiver receives the NSF signal or user
A specific four bits of the user signal are received (S31), and by decoding this, a binarization method is identified (S32).

Then, the receiver transmits the binarized code by an NSF signal or a user / user signal (S34) when the binarization method is applicable (S33), and when the binarization method is not applicable, the receiver transmits the binary code. By transmitting a binarized code other than the binarized code by an NSF signal or a user-user signal (S3
5), Notify whether it is possible or not.

Then, the transmitter receives the NSF signal or the user signal from the receiver (S22), identifies the specific 4 bits (S23), and transmits the binary code of the transmitted binary code.
It is determined whether the receiver can respond to the binarization method (S24, S25).

Thereafter, if the transmitter identifies that the receiver is compatible, it transmits the image data binarized by the binarization means corresponding to the binarization method (S26).

In addition, as an operation when the receiver is not compatible, in S35, a code indicating a compatible binarization method registered in the communication control unit 4 as described above (the eleventh code in this embodiment).
1111) shown in the figure can be transmitted by an NSF signal or a user-user signal.

At this time, the transmitter can identify the binarization method that the receiver can support by identifying the specific 4 bits of the NSF signal or the user-user signal, and the binarization method that the receiver can support The receiver performs binarization by a binarization method that can be supported by comparing and selecting a binarization method that can be performed by the transmitter, and the binarization method and the image are transmitted by the above-described transmission operation. And data can be transmitted to the receiver.

Upon identifying the binarization method from the other party, the communication control unit 4 on the receiving side transmits the binarization method to the decoding unit 5 and the image processing unit 6. The image processing unit 6 selects a corresponding image processing unit according to the transmitted binarization method, performs image processing on the received image data, sends the image data to the printer unit 7, and prints out the image data.

By transmitting and receiving the above-described code information to and from a specific image communication device in advance, for example, the binarization method of the partner image communication device and the applicable binary The binarizing method may be registered, and the binarizing units 21 to 24 and the image processing units 61 to 65 may be selected based on the registered binarizing method. In addition, for a partner device that cannot be registered in advance, image data can be transmitted and received using a communication protocol as described above.

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

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

The multi-value processing section 71 performs multi-value processing by smoothing processing. FIG. 15 and FIG. 16 are schematic diagrams showing a configuration example of a smoothing filter for image data binarized by, for example, the Bayer dither method and the fattening dither method.

As described above, by changing the method of multi-level conversion according to the type of the transmitted binary signal, a high-quality image signal can be obtained. Further, for example, for data binarized by the error diffusion method, a window applied to the binary data may be continuously moved, or for data binarized by the dither method, Instead of moving the window continuously, the window may be moved intermittently.

The density conversion section 72 performs conversion from luminance (RGB) data to density (cmy) data by searching a lookup table. This lookup table may be different or the same for each binarization method.

The masking section 73 performs a masking process for correcting the turbidity of the ink in the printer section 7.

The γ correction unit 74 performs γ correction in accordance with the characteristics of the printer unit 7, and the binary conversion unit 75 performs binarization for printer output.

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 common. Further, the circuit may be common such that the masking parameter differs depending on each binarization method, and only the parameter may be changed.

The image processing unit identifies the binarization method of the received image, and executes the above-described image processing means 61 to 65, or the multi-level conversion unit 71, the density conversion unit 72, the masking unit 73, the γ correction unit 74, and the binary conversion method. By selecting the unit 75, optimal image processing can be performed.

17 and 18 are flowcharts showing another example of the above-mentioned transmission / reception operation. FIG. 17 shows the operation of the transmitter, and FIG. 18 shows the operation of the receiver.

In this embodiment, the transmitter transmits a binarization code (S41), and when the receiver receives the code (S51), if the binarization method is compatible with the binarization method (S52), The binarization code is returned (S53), and if it is not possible to respond, a logical sum code indicating all possible binarization methods described with reference to FIG. 11 is returned (S54). Upon receiving the return code (S42), the transmitter compares the transmitted binary code with the received binary code (S43), and if they are the same, converts the image data by the binary method. If the values are not the same, it is determined whether there is a possible binarization method in the received binarization code (S44), and if so, the binarization method is determined. A selection is made (S45), the image data is binarized and transmitted (S46). If there is no image data, the image data is transmitted without binarization (S47).

In another embodiment, the image processing unit may include a correction unit that performs correction corresponding to each binarization method, and an image processing unit common to each binarization method. As an example of the correction corresponding to each binarization method, a look-up table corresponding to a 3 × 3 dot pattern centering on the pixel of interest is prepared, and there is a method of making the value correspond to the pixel of interest.

Further, instead of the Bayer dither method, the same Bayer dither method such as a 4 × 4 Bayer dither method or an 8 × 8 Bayer dither method may be used, and the compression method may be further finely classified.

Further, in the above embodiment, the code indicating the binarization method is transmitted to the receiver by a predetermined procedure signal, but it is also possible to transmit the first four bits of the image data by using the binarization code.

Further, in the above-described embodiment, binarization is performed as n-value compression. However, not only binarization but also ternary or quaternary conversion may be performed.

Further, in the above-described embodiment, the image data is input from the scanner unit 1, but may be input from a video camera, a still video, or an image database instead of the scanner.

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

Further, in the above embodiment, R, G,
Although B data is handled, similarly, X, Y, Z or L ^* , a ^* , b ^* representing color data, and even Y, I, Q used in television signals are handled. Good.

In the above embodiment, the communication side with the transmitting side notifies the transmitting side of the n-valued compression method that can be supported by the receiving side. In this notification, for example, the TTC
The user signal of the layer 3 specification under recommendation may be used, or another signal may be used.

[Effects of the Invention] As described above, according to the present invention, image data that has been n-valued using an n-value processing method according to the function of the receiving device can be transmitted to the receiving device, and good image communication can be achieved. There is an effect that can be done.

Further, there is an effect that the determination of the n-value processing method can be further efficiently performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a binarizing unit in the embodiment. FIG. 3 is a block diagram showing a configuration of an image processing unit in the embodiment. FIG. 4 is a flowchart showing an outline of an operation at the time of transmission in the embodiment. FIG. 5 is a flowchart showing an outline of an operation at the time of reception in the embodiment. FIG. 6 is a schematic diagram showing an example of a threshold matrix of the Bayer dither method. FIG. 7 is a schematic diagram showing an example of a threshold matrix of the fattening type dither method. FIG. 8 is a schematic diagram showing an example of image data when binarized by the Bayer dither method. FIG. 9 is a schematic diagram showing an example of image data in the case where binarization is performed by the fatning type dither method. FIG. 10 is a schematic diagram showing code information for four types of binarization methods in the embodiment. FIG. 11 is a schematic diagram showing code information for notifying the other device of the binarization method of the image communication device in the embodiment. FIG. 12 is a flowchart showing the operation of the transmitter when it is determined whether or not the binarization method is compatible on the receiving side in the embodiment. FIG. 13 is a flow chart showing the operation of the receiver when it is determined whether or not the binarization method can be handled on the receiving side in the embodiment. FIG. 14 is a block diagram showing another configuration example of the image processing unit according to 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 embodiment. FIG. 16 is a schematic diagram showing a configuration example of a smoothing filter for the fattening type dither method in the embodiment. FIG. 17 is a flowchart showing the operation of the transmitter according to still another embodiment of the present invention. FIG. 18 is a flowchart showing the operation of the receiver in the embodiment. DESCRIPTION OF SYMBOLS 1 ... Scanner part, 2 ... Binarization part, 3 ... Encoding part, 4 ... Communication control part, 5 ... Decoding part, 6 ... Image processing part, 7 ... Printer part, 71 ... ... Multi-value conversion section, 72... Density conversion section, 73... Masking section, 74... Γ correction section, 75.

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the m-value image data is converted to n-value image data (m>
a conversion means capable of converting m-valued image data into n-valued image data (m> n) by a plurality of different n-value conversion methods; An identification unit that identifies an n-value processing method that can be supported by the receiving device by performing bidirectional communication with the device; and a registration that registers a result identified by the identifying unit in a memory corresponding to the receiving device. And a receiving device, wherein the transmitting unit transmits the n-valued image data,
If it is registered in the memory, an n-value processing method is determined based on the registered identification result, and the receiving device to which the transmitting unit transmits the n-value image data is not registered in the memory. In this case, the image communication apparatus is characterized in that the identification means identifies an n-value processing method that can be supported by the receiving device, and determines the n-value processing method based on the identification result. 2. The image communication apparatus according to claim 1, wherein the m-value image data is color image data.