JPH07131627A - Image communication device - Google Patents

Abstract

(57) [Abstract] [Purpose] Image information is transmitted at a resolution that is optimal for the characteristics of the image. An image processing unit 112 creates an image having N layers, from a low resolution image to a high resolution image, to the image data stored in the image memory 110, and stores the image in the image memory 110. . When the sender performs an operation of designating to what resolution the original document to be transmitted is to be transmitted, the encoding / decoding unit 116 creates a differential signal of an image corresponding to the designated resolution, and creates it in a layer of that resolution. And transmit the differential 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 for compressing data of transmitted / received images by using Joint-Bi-level Image Coding Experts Group (hereinafter referred to as JBIG).

[0002]

2. Description of the Related Art Conventionally, in an image communication apparatus such as a facsimile machine, a multi-valued image read from a document or the like is temporarily
The image is converted into a binary image, encoded by an encoding method such as the MH, MR, and MMR method, and sequentially transmitted in the order in which the image is read. This method is suitable for a facsimile machine that sequentially records received images on recording paper, etc.
For a device that temporarily stores a received image in a memory or the like and then outputs the image, or an image with a high spatial frequency, it cannot be said that the redundancy of image information can be reduced.

On the other hand, a method of transmitting images hierarchically from low resolution to high resolution (JBIG method)
There is. According to the JBIG method, first, a certain amount of image is once read on the transmitting side and stored in a memory. Then, a low-resolution first image is created by calculation, arithmetically encoded, and transmitted. Next, a second image having twice the resolution of the first transmitted image is created, and the difference from the first image is arithmetically encoded and transmitted. Then, by repeating this operation, the image of the resolution required on the receiving side is transmitted. Since the arithmetic coding is lossless coding, the image is reproduced on the receiving side by the reverse operation to the above.

[0004]

However, in the above-mentioned conventional image communication apparatus, the information compression of the image has to rely only on the compression by the arithmetic coding which is one of the predictive coding, and the amount of information is originally required. In the case of an image having a low spatial frequency, which requires a small amount of data, if all the image information is transmitted hierarchically, there is a problem that the information may be decompressed.

The present invention has been made in view of the above problems, and an object thereof is to provide an image communication apparatus for transmitting image information at a resolution optimum for image characteristics.

[0006]

In order to achieve the above object, the invention described in claim 1 is a means for storing image information obtained from an original image, and an image having a plurality of resolutions from the image information. And a means for designating an arbitrary resolution from among the plurality of resolutions, and transmitting an image having the designated resolution.

According to a second aspect of the present invention, in an image communication apparatus for transmitting an image hierarchically in layers for each resolution, a means for storing image information obtained from an original image, and the image information Means for creating an image having a plurality of resolutions, means for quantitatively calculating the characteristics of the image information, means for determining a resolution that matches the characteristics from the plurality of resolutions, and And a transmission unit that transmits an image in a layer corresponding to the resolution.

[0008]

In the above structure, the image information is transmitted at the optimum resolution with reduced redundancy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. [First Embodiment] FIG. 1 is a block diagram showing a configuration of a main part of an image communication apparatus (hereinafter referred to as an apparatus) according to a first embodiment of the present invention. In the figure, reference numeral 101 is a control unit including, for example, a microprocessor, and includes a CPU (central processing unit) 113, a ROM (read only memory) 114, and a RAM (random access memory).
115, a buffer memory 117, an image memory 110, an image processing unit 112, and an encoding / decoding unit 116, and controls input / output of images in this apparatus and the entire communication process. The ROM 114 stores a control program to be described later, and the RAM 115 includes the CPU 11
It is used as a work area for No. 3.

The input of image information in this apparatus is performed by the reading unit 1.
00, and the recording unit 102 outputs the image information. The reading unit 100 is composed of a CCD sensor (not shown), a document feeding system, etc., and reads image data on a document. The recording unit 102 is composed of, for example, a thermal printer, an inkjet printer, a laser beam printer, or the like, and visually records the received image data or the image data read by the reading unit 100 during the copy operation.

The image memory 110 is a memory having a large memory capacity such as a frame memory for storing the image data read by the reading unit 100, and stores one frame or a certain amount of image information. In addition, the image processing unit 112
Then, for the image data stored in the image memory 110, an image having N layers from a low resolution image to a high resolution image is created.

The encoding / decoding unit 116 encodes the image data obtained by subjecting the read image to the above-mentioned image processing according to the JBIG method, and also decodes the transmitted encoded image data. The encoding / decoding unit 116 also creates a difference signal between the image of the resolution (J) created by the image processing unit 112 and the image of the resolution (2 * J). The encoding / decoding unit 11
Reference numeral 6 is composed of predetermined hardware or software of the CPU 113.

The buffer memory 117 is a so-called FIF.
Encoding / decoding unit 116 and modem (not shown) in O format
Input and output data from. Further, the display unit 104 is
It displays phone numbers, time, and device status.
The operation panel 103 is composed of a numeric keypad for inputting a telephone number and the like, various function keys, and the like, but may be structured to include the display unit 104.

Next, the flow of processing on the transmitting side in the image communication apparatus according to this embodiment having the above-mentioned configuration will be described with reference to the flowchart shown in FIG. In step S1 of FIG. 2, the reading unit 100 reads the content of the transmission document, and in step S2, the read image is stored in the image memory 110. In step S3, data having resolutions A, B, and C are created from the data stored in the image memory 110 in order of coarse resolution. Then, the data created in step S3 is stored again in the image memory 110.

In step S4, the sender of the image data uses the operation panel 103 to perform an operation of designating to what resolution the original to be transmitted is transmitted. It should be noted that the notation for this operation may be notation such as standard, fine, and super fine as used in a normal facsimile machine, or notation for notifying the operator of other resolutions. It doesn't matter.

In step S5, the encoding / decoding unit 11
In 6, up to the resolution specified in step S4 above,
Sequentially, a differential signal between the images of resolution J and resolution 2 * J is created and transmitted. At this time, information about up to which resolution is transmitted is added to the communication protocol for each communication or page. As described above, in the present embodiment, the amount of transmission information is variable according to the determination of the sender of image data, so that useless information can be reduced and transmitted by a simple operation on the transmission side. [Second Embodiment] FIG. 3 is a block diagram showing the arrangement of an image communication apparatus according to the second embodiment of the present invention. In the figure, the same components as those of the image communication apparatus according to the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted here.

As shown in FIG. 3, the apparatus according to the present embodiment is provided with an arithmetic unit 111, and the arithmetic unit 111 calculates the characteristics of the image from the image data stored in the image memory 110. FIG. 4 is a flowchart showing the flow of processing on the transmission side of the device according to this embodiment. In step S11 of the figure, the reading unit 100 reads the image data from the transmission document, and in step S12, the read image data is stored in the image memory 110. Continuing step S
At 13, data having resolutions A, B, and C are created from the data stored in the image memory 110 in order of coarse resolution, and the created data is stored in the image memory 110 again. It should be noted that, in the present embodiment, layers having three types of resolutions will be described, but the number of resolutions is not limited as long as there are multiple types.

In step S14, the reading unit 110 is first
From the image data read by, the characteristics (K
_The calculation unit 111 calculates ₁ ). The characteristic K ₁ is quantitative data unique to the image calculated by the calculation in the calculation unit 111. Also, the above steps S14 and S1
The processing order of 3 may be reversed. here,
Image characteristics are data that indicate whether the image itself is difficult for the other side to recognize unless it is transmitted in high resolution. Considering this, as one that can be applied to both a multi-valued image and a binary image, orthogonal transformation such as Laplace transformation or Fourier transformation is performed on the read image in the horizontal and vertical directions, and the spatial frequency is calculated. Method is used. Then, by dividing this spatial frequency by the calculated number of samples, the average spatial frequency of the image can be known. The above K ₁ is the value thus calculated.

In step S15, first, the image A having the coarsest resolution as a base is transmitted. Also, step S
In S16 and S18, the value of K ₁ is compared with the thresholds L ₁ and M ₁ which are empirically set and which determine the fineness of the image. In this embodiment, these thresholds are described as two types, but the thresholds are variable according to the number of resolution layers.

The threshold value L ₁ is a threshold value between an average image and a delicate image, the threshold value M ₁ is a threshold value between an average image and a rough image, and the data K ₁ and the threshold value L ₁ are calculated in step S16. By comparison, if K ₁ is smaller, this process ends.
However, if K ₁ is larger, the process proceeds to step S17, and the difference between the resolution B and the resolution A is transmitted. Step S
At 18, K ₁ and M ₁ are compared. That is, in comparison with M ₁ , if K ₁ is smaller, this process is terminated, but K ₁
Is larger, the process proceeds to step S9, where the difference between the resolution C and the resolution B is transmitted, and this processing ends.

When transmitting this difference, if the information indicating up to which resolution is transmitted is added to the communication protocol for each communication or page, the receiving side can receive the image data without any operation. . Also, in the sequential mode assuming that the receiving side does not have a frame memory, if additional information is added for each sequence,
Even if an image with different fineness exists in one page, it can be efficiently compressed.

As described above, also in the second embodiment, the image data can be transmitted at the resolution optimum for the characteristics of the image. <Modification> A modification of the second embodiment will be described. In the second embodiment described above, the characteristic of the image is calculated by the calculation unit 111, but the characteristic in consideration of the visual characteristic of the image may be calculated from the image data stored in the image memory 110. Good. Note that the arithmetic unit 1 is also used here.
Although 11 may be hardware or software, the amount of information becomes enormous in consideration of processing a multi-valued image and the like, and it is desirable to be configured by hardware in consideration of calculation time and the like.

Therefore, the flow of processing according to this modification will be described with reference to the flowchart shown in FIG. In step S21 of FIG. 5, the reading document is read by the reading unit 100, and the image read in step S21 is stored in the image memory 110 in step S22. Also, step S2
3, data having resolutions A, B, and C, differential data between images of resolution A and resolution B, and differential data between images of resolution B and resolution C are displayed in order of coarse resolution from the data stored in the image memory 110. create. Then, the data created here is stored in the image memory 110 again.

In step S24, the calculation unit 111 calculates a characteristic in consideration of the visual characteristic of the image from the data first read by the reading unit 110. Note that the processing order of these steps S24 and S23 may be reversed. Here, the visual characteristic of an image is that the image itself is
It shows whether or not it is difficult for humans to recognize unless it is transmitted at high resolution.Generally, the visual characteristics are sensitive to the edge part of the image with high contrast, and the spatial frequency It is also sensitive to relatively expensive items.

As one of the methods for quantitatively treating this characteristic, there is a method for obtaining the variance of the luminance signal from the read image. The variance here may be obtained from the data of all one frame, but with this method, the edges and the like in the flat image are averaged and buried, so one frame is divided into several blocks. However, it is better to obtain the variance for each block and use the maximum value as a representative.

Assuming that the value of this variance is K ₂ , the larger the value, the larger the amount of change in the image for each pixel. Therefore, it is considered that human vision is sensitive, and an image with high resolution is required. It will be. Therefore, in step S25, first, the image A having the coarsest resolution as a base is transmitted. In steps S26 and S28, the value of K ₂ is compared with the thresholds L ₂ and M ₂ that determine empirically set visual characteristics of the image in advance. L ₂ is a threshold between an average image and an image to which human vision is sensitive, and M 2
₂ is the threshold value between the average image and the image insensitive to human vision.

In step S26, K ₂ and L ₂ are compared, and if K ₂ is smaller, this process ends, but K ₂
Is larger, the process proceeds to step S27, and the difference between the resolution B and the resolution A is transmitted. Next, in step S28, K ₂ and M ₂ are compared. Then, if K ₂ is small, the present process is terminated, but if K ₂ is large, the process proceeds to step S29, the difference between the resolution C and the resolution B is transmitted, and the process is terminated.

As described above, according to this modification, it is possible to transmit the image with the optimum resolution for the visual characteristics of the image. In addition, here
The difference data is transmitted every time the comparison and determination are performed, but the present invention is not limited to this, and the transmission may be started after performing all the comparison and determination by calculation. 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.

[0029]

As described above, according to the present invention,
By transmitting the image information at the resolution according to the characteristics of the image, the transmission time and the transmission cost can be significantly reduced, and high-speed communication with reduced redundancy can be performed.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a processing procedure on the transmission side of the apparatus according to the first embodiment.

FIG. 3 is a block diagram showing a configuration of an image communication device according to a second embodiment.

FIG. 4 is a flowchart showing a processing procedure on the transmission side of the apparatus according to the second embodiment.

FIG. 5 is a flowchart showing a processing procedure according to a modification of the second embodiment.

[Explanation of symbols]

 100 reading unit 101 control unit 102 recording unit 103 operation panel 104 display unit 110 image memory 111 arithmetic unit 112 image processing unit 113 CPU 114 ROM 115 RAM 116 encoding / decoding unit 117 buffer memory

Claims (5)

[Claims] 1. A means for storing image information obtained from a document image, a means for creating an image having a plurality of resolutions from the image information, and a means for designating an arbitrary resolution from the plurality of resolutions. An image communication apparatus, comprising: an image transmitting apparatus that transmits an image having the specified resolution. 2. An image communication apparatus for hierarchically transmitting an image in layers for each resolution and transmitting the image information obtained from a document image, and creating an image having a plurality of resolutions from the image information. Means, means for quantitatively calculating the characteristic of the image information, means for determining a resolution suitable for the characteristic from the plurality of resolutions, and an image in a layer corresponding to the determined resolution. An image communication apparatus comprising: a transmission unit that transmits. 3. The image communication apparatus according to claim 2, wherein the characteristic is a characteristic according to a spatial frequency of an image. 4. The image communication apparatus according to claim 2, wherein the characteristic is a characteristic according to a visual characteristic of an image. 5. The apparatus further comprises means for dividing the image into a plurality of sequences, and the transmitting means hierarchically transmits the image for each of the sequences in a layer for each of the resolutions. The image communication device according to claim 2.