JP3101159B2 - Image transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transmission apparatus having a function of transmitting and receiving a video still image and a facsimile function.

[0002]

[Prior art]

<Background 1> A still image transmission device captures one scene of a video taken by a video camera or a video recorded in a video as a still image in an image memory, and compresses / compresses the internationally standardized still image compression / decompression method ( JPEG format) or a function that transmits data through a digital line such as an analog telephone line or ISDN, and compresses the data using an original non-standardized compression / decompression method. It has a function of storing and displaying.

<Background 2> A facsimile apparatus optically reads an original, digitizes the original, compresses and encodes the original by a standardized compression / decompression method, sends it out to a partner via a communication line, and compresses the data sent from the partner. This is a device for receiving a coded data, decoding the coded data, and recording the coded data on a sheet to obtain a document.

<Background 3> As a method for converting a halftone image such as a photograph into a binary image in a facsimile apparatus, for example, Journal of the Institute of Image Electronics Engineers of Japan Vol. 10, No. 5, (1)
981) and the “An Adaptiv
The error diffusion method shown in "e Algorithm for Gray Scale" (SID 75DIGEST) is known.

[0005]

In the still image transmitting apparatus of the background 1, although a video still image can be transmitted and received, it cannot be transmitted to a facsimile apparatus. Therefore, in order to take a hard copy of a still image, a dedicated video printer or the like must be used, which leads to an increase in cost. Further, both devices need to use this device for communication, and there is a problem that the image communication function cannot be utilized by one device. In the image data on which the pseudo halftone binarization processing such as the background 3 has been performed, black pixels are randomly arranged to express halftones. The run-length code which is the basis of the compression coding of the facsimile apparatus described in Background 2 is a method of coding the run length of white pixels and black pixels, and is the data of image data which has been subjected to the pseudo halftone binarization processing. Is not only inefficient in compression efficiency, but also causes an increase in data. Therefore, there is a problem that a large memory capacity is required to store the halftone image as it is or for a plurality of pages by the facsimile coding method. The present invention has been made in view of the above-described problems, and in an image transmission apparatus that transmits a still image, separates a luminance signal, performs resolution conversion suitable for sending to a facsimile, and performs resolution conversion. It is an object of the present invention to provide an image transmission apparatus having a function of performing halftone binarization processing as in Background 3 and performing encoding for facsimile.

The resolution conversion suitable for separating the luminance signal and sending it to a facsimile is performed because the resolution displayed on a display and the resolution printed on a printer are significantly different. The resolution handled by the apparatus is 384 dots to 768 dots in the main scanning line direction, and is 1728 dots in A4 size in the case of facsimile.

[0007]

In order to solve the above problems, an image transmission apparatus according to the present invention separates an input video signal into a luminance signal and a chrominance signal, and outputs a D / A-converted luminance signal and a luminance signal. Video signal processing means for synthesizing the color difference signal and outputting a video signal; A / D conversion means for A / D converting the luminance signal and the color difference signal processed by the video signal processing means; D / A conversion means for D / A converting the color difference signal and outputting it to the video signal processing means, and an image for storing one frame or one field of still image data digitized by the A / D conversion means A memory, and memory control means for writing digitized image data to the image memory and reading image data from the image memory;
Binary image processing for extracting a luminance signal from the image data stored in the image memory, enlarging the luminance signal at a predetermined magnification, performing pseudo halftone binarization processing, and performing encoding processing for facsimile And communication control means for performing communication protocol processing for facsimile. Further, in the image transmission device, encoding the still image data, image codec means for decoding,
And an encoding memory for storing encoded data for a plurality of frames. Said image codec means,
In the image transmission device including the encoding memory, the encoded data stored in the encoding memory is compressed data generated from the image data read by the memory control unit, and the image codec unit And generating compressed data from the image data read by the memory control means .

[0008]

The input video signal is separated into a luminance signal and a color difference signal, each of which is subjected to A / D conversion. Then, the luminance signal and the chrominance signal, which are simultaneously written into the image memory and digitized, are D / A-converted, and the D / A-converted luminance signal and chrominance signal are combined to generate a video signal. It is sent to the television receiver and displayed. Here, when the freeze switch is operated for the image to be transmitted, a still image for one frame is stored in the image memory in accordance with the operation. Only the luminance signal in the still image is enlarged by a predetermined magnification, and a pseudo halftone binarization process such as an organized dither method or an error diffusion method is performed on the result of the enlargement, and a coding process for facsimile is performed. Is performed. As the encoding process at this time, a standardized MH (Modified Huffman) system or MR (Modified Read) system can be considered, but both are compression encoding systems on the premise of a document image, and a pseudo halftone image is used. Since no compression efficiency can be expected for, a simple MH method of processing is considered appropriate. For facsimile machines that optionally support the uncompressed mode, transmitting uncompressed data is also an effective means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing one embodiment. FIG. 1 shows an image transmission apparatus compatible with an analog network according to the present invention. Reference numeral 11 denotes an input composite video signal which is a luminance signal (Y signal) and color difference signals (Cb, Cb).
r), a function of generating a horizontal / vertical sync signal by performing sync separation, and a function of generating a composite video signal from a horizontal / vertical cycle signal by mixing a luminance signal and a color difference signal, and outputting the composite video signal And a video signal processing unit having:
Reference numeral 12 denotes an A / D converter for A / D converting each of the Y / C separated signals and digitizing an image, and reference numeral 13 denotes a D / A converter for D / A converting digital image data. 14 latches the image data A / D converted by the A / D converter 12 with an external synchronization clock, and stores an image memory 15 of one-field image data based on the external synchronization signal.
This is a memory control unit that controls writing to the memory and sequentially reads image data from the image memory 15 for encoding.

Reference numeral 15 denotes an image memory corresponding to the number of display pixels, which stores one frame or one field of still image data digitized by the A / D converter 12. Reference numeral 16 denotes a function for sequentially forming image data read from the image memory 15 by the memory control unit 14 by an action of a freeze switch or the like, and performing DCT (discrete cosine transform) processing and Huffman coding based on JPEG specifications to generate compressed data. And an image codec unit having a function of reading compressed data stored in an encoding memory 18 to be described later, performing Huffman decoding and IDCT (inverse discrete cosine transform) processing based on JPEG specifications to decompress the compressed data. . Numeral 17 extracts only the luminance signal (Y signal) from the image memory 15, enlarges it to a predetermined magnification (2 to 4 times is considered appropriate), and uses a pseudo intermediate method such as the systematic dither method or the error diffusion method. This is a binary image processing unit that performs encoding for facsimile after performing tone binarization processing.

Reference numeral 18 denotes an encoding memory for selecting and storing an encoding method according to a communication mode, specifically, communication with a facsimile or a color still image transmission device, and stores compressed encoded data. Accumulate multiple frames. 1
Reference numeral 9 denotes a communication control unit having a facsimile communication protocol corresponding to a communication mode and a color still image transmission protocol processing function. Reference numeral 20 denotes a modem unit for transmitting digital data, and reference numeral 21 denotes an NCU unit for controlling an analog network.

FIG. 2 is a detailed block diagram of the binary image processing section 17. In FIG. 2, reference numeral 31 denotes a Y signal separation unit for separating and extracting Y signals of the color still image data input from the image memory 15 of FIG. 1 by the memory control unit 14, and 32 simply converts the extracted multi-tone pixels. 33 is a pseudo halftone binarization processing unit that rearranges the expanded multi-tone data in line units and performs dithering, and 34 a facsimile of the binarized pixel data. Is an encoding unit that performs encoding according to the encoding method standardized in. FIG. 3 shows quadruple enlargement of pixels in the image enlargement unit.
In FIG. 3, P indicates the luminance level of the pixel. In the pseudo halftone binarization processing unit 33, an organized dither method and an error diffusion method are effective.

Next, the operation of the image transmission apparatus will be described. First, when a communication partner is an image transmission device, a video signal input from a video input is processed by a video signal processing unit 11 to output a luminance signal (Y) and color difference signals (Cb, Cb).
r), and each is converted into a digital signal by the A / D converter 12. The memory control unit 14 stores the digital image data input from the video input into the image memory 15.
To the image codec unit 16
After performing compression encoding (for example, the JPEG method) for a color still image, the image data is stored in the encoding memory 18. By repeating this sequence, still image data of a plurality of images can be stored in the encoding memory 18. In this state, if the transmission destination is the same device or a color still image transmission device having the same communication protocol, the coded image data stored in the Modem part 20 by protocol,
The data is transmitted to the partner terminal via the NCU 21.

When the communication partner is a facsimile, the coded image data stored in the coding memory 18 is sent to the image codec section 16 to decode the coded image and, at the same time, to decode only the Y signal in the image memory 15. To D
By outputting as a video signal via the / A converter 13, a monochrome display is performed. Thus, the image to be transmitted is confirmed. Further, the monochrome image data is subjected to enlargement processing at a magnification determined by the binary image processing unit 17,
After that, after being subjected to pseudo halftone binarization processing by the binary image processing unit 17, encoding processing (MH, MR) for facsimile is performed.
Etc.) are performed. The encoded facsimile data is transmitted to the modem unit 2 by the communication control unit 19 according to a communication protocol for facsimile (ITU-T Recommendation T.30 for G3 FAX).
0, and sends it to the other party's FAX via the NCU 21.

The encoding memory 18 shown in FIG.
Has a capacity capable of accumulating a plurality of pages of compressed color still image data. By repeating the cycle of expanding the compressed still image data of a plurality of pages once in the image codec unit 16 and writing the compressed data in the image memory 15, respectively. Once the user has selected the image they want to send,
The selected image is transmitted to the binary image processing unit 17 under the control of the memory control unit 14, and can be transmitted as facsimile data.

FIG. 4 shows another embodiment of the present invention, and is a block diagram of a binary image processing section 17 in which a tone correction section 35 is added. The purpose of this is to convert the color image into a monochrome image, because the image quality of the dark part is degraded depending on the hue, so that the correction for emphasizing the dark part is performed. Is achieved. The tone correcting unit 35 generates an image with good contrast.
Also, by preparing a plurality of correction data tables, the color still image data expanded by the image codec or the color still image data input directly from the video input is passed through the Y signal separation unit 31 and the tone correction unit 35. By repeating the cycle of writing to the image memory again, the user can check the image of the correction result and can select the image to be sent.

[0017]

According to the present invention, an image input as a video signal is frozen, converted into color still image data, a luminance signal therein is extracted, and the monochrome gradation data is converted into facsimile data. By performing a series of processes of performing pseudo halftone processing and performing facsimile encoding after performing a proper resolution conversion, a halftone image can be efficiently transmitted to a facsimile. Also,
When facsimile encoding is performed on pseudo halftone binary data, no data compression can be expected. However, as in the present invention, in addition to the above series of processing, a color still image
By preparing a memory for compressing by a compression method such as PEG and storing a plurality of pages, a user can select a necessary image and send it to a facsimile .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an image transmission device according to the present invention.

FIG. 2 is a block diagram of an embodiment of a binary image processing unit in the image transmission device of the present invention.

FIG. 3 is a diagram illustrating image enlargement by the image transmission device of the present invention.

FIG. 4 is a block diagram showing another embodiment of the binary image processing unit in the image transmission device of the present invention.

[Explanation of symbols]

 Reference Signs List 11 video signal processing unit 12 A / D converter 13 D / A converter 14 memory control unit 15 image memory 16 image codec unit 17 binary image processing unit 18 encoding memory 19 communication control unit 20 modem unit 21 NCU unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/00-1/00 108 H04N 1/40-1/409

Claims (4)

(57) [Claims] 1. A video signal processing means for separating an input video signal into a luminance signal and a color difference signal, synthesizing a D / A-converted luminance signal and a color difference signal, and outputting a video signal; A / D conversion means for A / D converting the luminance signal and color difference signal processed by the means, and D / A for D / A converting the digitized luminance signal and color difference signal to output to the video signal processing means. A conversion unit; an image memory for storing one frame or one field of still image data digitized by the A / D conversion unit; and writing the digitized image data to the image memory. Memory control means for reading image data from the image memory; extracting a luminance signal from the image data stored in the image memory; Image transmission apparatus comprising: binary image processing means for performing pseudo halftone binarization processing by enlarging at a magnification and encoding processing for facsimile; and communication control means for performing communication protocol processing for facsimile . 2. An image transmission apparatus according to claim 1, further comprising image codec means for encoding and decoding said still image data, and an encoding memory for storing encoded data for a plurality of frames. . 3. The image transmission device according to claim 2, wherein the encoded data stored in the encoding memory is compressed data generated from the image data read by the memory control unit. 4. The image transmission device according to claim 3, wherein said image codec means generates compressed data from the image data read by said memory control means.