JPH03265372A - Picture communication equipment - Google Patents

Abstract

PURPOSE:To attain proper n-value processing at a sender side by informing n-value compression method acceptable to the sender side from a receiver side. CONSTITUTION:In the case of receiving an m-value picture data while being compressed into an n-value picture data (m>n), the receiver side informs the n-value compression method acceptable to the sender side. That is, when a transmitter sends a binarizing code, a receiver returns the binarizing code when the binarizing processing is acceptable and returns an OR code representing all binarizing methods acceptable by the receiver when the informed processing is not acceptable. A transmitter selects the binarizing method to send the information, a receiver side communication control section 4 sends the binarizing processing method to a decoding section 5 and a picture processing section 6, which applies picture processing to the picture data received by the informed binarizing processing. Thus, the sender side selects the n-value compression method acceptable to the receiver side for transmission.

Description

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

[Prior Art] Various color facsimile devices that communicate color images have been proposed in the past.
The three color information of R), green (R), and blue (B) are each O~
Since it has 255 to 256 gradations, the data capacity is much larger than that of a black and white image, and the communication time is longer, making it extremely difficult to put into practical use a device that transmits such multi-valued information as it is. It became.

[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 H is compressed 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 bay medium dither method, a receiving device that is adjusted to reproduce appropriate colors may be binarized using the fattening 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 transmitting side and the receiving side that occur depending on the type of n-value conversion method α 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 Problems] The present invention provides an n-value compression method that can be applied from the receiving side to the transmitting side in an image communication device that receives n-value image data (m>n) compressed from m-value image data. It is characterized by notifying the following.

[Operation] In the present invention, when the receiving side notifies the transmitting side of the applicable n-value compression method, and the transmitting side can select the applicable n-value compression method, the n-value compression method It is possible to transmit the converted image, and it is possible to properly reproduce it on the receiving side.

Furthermore, even if the sending side cannot perform n-ary conversion that the receiving side can handle, the sending side can at least be aware of this, and, for example, cancel the transmission using n-value conversion and try transmitting using another method. You can take effective measures such as

[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 1 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 encodes received encoded data. It has a decoding section 5 for decoding, an image processing section 6 for processing two 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 Bay medium 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.

i3r! 1I is a block diagram showing the configuration of the image processing section 6. FIG.

The image processing unit 6 according to this embodiment uses a bay medium dither method,
It has four types of image processing means 61 to 64 corresponding to four types of binarization methods: a fattening dither method, an error diffusion method, and a 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 the 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, 256 gradation data (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 H 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 B for each dot, which 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 (Sll), the received image information is sent to the decoding unit 5, where it is decoded. , and sends it to the image processing unit 6 (S12). The image processing section 6 performs image processing according to the information regarding the binarization method received from the communication control section 4 (S13), and the printer section 7
and print it out (S L 4).

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) Fartoning dither method, (3) error diffusion method, and (4) simple binarization method. Bay medium dither method and Fartoning dither method both compare the image with a threshold matrix. However, if the image data is larger than the corresponding threshold value, it is set to "1", and if it is smaller, it is set to rOJ.

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 fattening dither method.

A feature of the bay medium dither method is that when binarized using this method, dots tend to be dispersed, and a feature of the fattening dither method is that, conversely, 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 pay-medium dither method, whereas it is concentrated when using the fattening method.

When such two 2m 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 dither method, the dark areas, or dots that hit the ink, are dispersed, resulting in large ink smearing, whereas in an image binarized using the fattening dither method, the dots are scattered. is concentrated, so the ink smear is small.

As a result, the image binarized using the Bay medium dither method is darker than that obtained using the fattening 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 fattening dither method, the error diffusion method, and the simple binarization method are possible; generally, when the resolution is low, the bay medium dither method provides a good image, and when the resolution is high, the fattening dither method is possible. You can get good images using this 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, in S2 of 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. By transmitting and receiving information regarding the binarization method to and from the partner device, the above-mentioned -binarization means 21 to 24 and 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 binarization method of type 41a 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 the image communication device.

This code information is the logical sum of the codes shown in Figure 1θ above, and by sending this to the other device, it is possible to display what kind of binarization method this image communication device has. 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 a code indicating the binarization method using a predetermined procedure signal (521).
.

In other words, if the receiver is an image communication device that complies with 63 facsimile, a code indicating the binarization method is sent to the receiver using an initial identification signal of a non-standard function, for example, a specific 4-bit 7 bit of the NSF signal. It is possible to send.

In addition, if the receiver is an image communication device compliant with G4 facsimile, 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 receiving @
Receive a specific 14 bits of the user signal (531) and identify the binarization method by decoding this (532)
.

Then, if the receiver is compatible with the z-value conversion method (533), the receiver transmits the binary code as an NSF signal or a user-to-user signal (334), and if it is not compatible, the receiver transmits the z-value code. Binarized code other than encoded code is N
By transmitting an SF signal or a user-to-user signal (335), it is notified whether or not support is possible.

Therefore, the transmitter receives the NSF signal or user-to-user signal from the receiver (322), identifies the specific 4 bits (S23), and determines the binarization method of the transmitted binary code. , it is determined whether the receiver is compatible or not (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 indicating a compatible 2gM method registered in the communication control unit 4 as described above (in this embodiment, l111 shown in FIG. 11) can be transmitted by NSF signals or user-to-user signals.

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
5 selections may be made. Furthermore, for a partner device that cannot be registered in advance, image information 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 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 binarized by, for example, the Bayer 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 code, 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
) conversion to data. This lookup table 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 common. Further, the circuit may be common, and only the parameters may be changed, such as using different masking parameters depending on the binarization method.

The image processing section identifies the binarization method of the received image, and each of the above-mentioned image processing means 61 to 65 (or 65)
1. Density conversion section 72, masking section 73, γ correction section 74
By selecting the binary conversion unit 75 and the binary conversion unit 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 (5
41), when the receiver receives this (S51), if the receiver is compatible with the binarization method (S52),
The binarization code is returned (553), and if the binarization method is not applicable, an OR code indicating all the compatible binarization methods explained in FIG. 11 is returned (S54). When the transmitter receives the return code (S42), it compares the transmitted binary code with the received binary code (543).
, if they are the same, binarize the image data using that binarization method.
546), and if they are not the same, determine whether there is a possible binarization method in the received binarization code (S44), and if so, select that binarization method. (S45), the image data is binarized and transmitted (546), and if there is no image data, 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 lookup table is prepared according to a 3×3 dot turn centered on the pixel of interest, and a value is made to correspond to the pixel of interest.

Furthermore, it is not just a below-bay dither method, but a 4×4 below-bay dither method, an 8×8 below-bay dither method, etc. Even if the same below-bay dither method is used, it may be a more detailed classification of compression methods. good.

Further, in the embodiment described above, the code indicating the binarization method was transmitted to the receiver using a predetermined procedure signal, but it can also be transmitted by using the first 4 bits of the image data as a binarization code.

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

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.

Further, in the above embodiment, R, G, B
Although the present invention deals with data, it may similarly handle x, y, z or L"a*b* representing color data, or even Y, 1, and Q used in television signals.

In the above embodiment, the receiving side notifies the transmitting side of the applicable n-ary compression method through communication with the transmitting side.
The user-to-user signal of the Layer 3 specification currently being recommended may be used, or other signals may be used.

[Effects of the Invention] As explained above, according to the present invention, by notifying the transmitting side of an applicable n-value compression method from the receiving side, it is possible to perform appropriate n-value compression on the transmitting side. Become.

[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 illustrating an example of a threshold matrix for the Baye-lower 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 Bay-lower dither method. FIG. 9 is a schematic diagram showing an example of image data when binarized using the fattening dither method. FIG. 1O 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 the same 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 configuration example 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 below-bay dither method in the same embodiment. FIG. 16 is a schematic diagram showing a configuration example of a smoothing filter for the fattening 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. 75...2gM conversion section.

Claims (2)

[Claims] (1) N-value image data compressed from m-value image data (
An image communication apparatus that performs reception (m>n), characterized in that the reception side notifies the transmission side of an applicable n-value compression method. (2) 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.