JPS6295072A - Transmission device for picture data - Google Patents

Abstract

PURPOSE:To largely reduce the quantity of the data for transmitting all pictures by resolving a picture element signal consisting of plural bits into bit pictures every bit, applying a highly efficient encoding to every bit picture, and optionally selecting the bit picture to be transmitted. CONSTITUTION:In the picture data AD0-AD3 quantized by four bits, there are a bit plane selecting means 13 for selecting one or more than two bit planes Bit0-Bit3 according to a character or a picture tone such as a half tone picture and data transmitting means 3-13 for transmitting M picture elements of a series of the bit data of the bit planes Bit2, Bit3 selected by the bit plane selecting means. The picture data AD0-AD4 quantized by the four bits for one picture element are encoded and compressed in their respective bit planes by modified Haffman encoders 3-6 and stored in line memories 7-10. The information of a character picture area and a half tone area is previously applied to a controller 13 and the controller 13 controls the selection of a selector 11 in accordance with this information.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image data transmission device, and more particularly to an image data transmission device that transmits image data information quantized with N bits per pixel.

[Prior Art] Conventionally, a so-called digital copying device converts an original image into an electrical signal using a photoelectric conversion element such as a COD, reads the signal, and transmits the read data to an image reproduction device for printing (copying). is proposed. On the reading side of this type of device, one pixel is converted into one bit of °°0'' or °°.
In many cases, the signal is converted to a 1' logic level and transmitted to an image reproduction device. However, in cases where text and photographic images are mixed on a document, there is no problem as long as the characters can be read, but there is a drawback in that the reproducibility of the photographic images is lacking. Since subtle shading cannot be obtained with image data of 1 bit per pixel, efforts are being made to improve the reading and reproduction of gradation images by increasing the density of document reading and increasing the number of gradations. . However, transmitting multi-gradation image data as is has the disadvantage that not only the amount of information becomes enormous, but also the scale of the hardware becomes large. In order to deal with such problems, multi-tone image data is decomposed into screens (bit planes) for each gradation bit, and a series of bit data for each bit plane is processed using conventional methods such as MH and MR methods. A method has been proposed in which high efficiency encoding is performed using a binary data encoding method and the data is transmitted. However, when using such a method, it is possible to obtain a relatively high image encoding compression rate for bit planes with heavy bit weights (bit planes close to the most significant bit MsB and MSH), but on the other hand, For light bit planes (LSB and bit planes close to the LSB), the encoding compression rate becomes 1 or less. That is,
Depending on the coding compression, the amount of data may increase, and the overall compression rate cannot be as high as expected.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide image information containing a mixture of characters and halftone images with less processing or configuration. An object of the present invention is to provide an image data transmission device that can efficiently transmit image data.

[Means for Solving the Problem] As a means for solving this problem, for example, the image data transmission apparatus of the embodiment shown in FIG. 1 uses image data AD quantized with 4 bits per pixel.

An image data transmission device for transmitting information of ~AD3, the image data ADo~AD quantized by the 4 bits.
3, one or two or more bits to be transmitted depending on the image tone, such as a character or a halftone image.
o'' Bit plane selection means 13 that selects Bit 3, and a series of bit data of bit planes Bit 2 and Bit 3 selected by the bit plane selection means, for example, M
Data transmission means 3 to 13 are provided for transmitting data pixel by pixel.

Preferably, the data transmission means is a data encoding means 3 that performs MH encoding on uniform bit data to be transmitted.
~6.

[Operation] In the configuration shown in FIG. 1, the image data ADo-AD4 quantized at 4 bits per pixel is encoded and compressed for each bit plane by modified Huffman (MH) encoders 3 to 6, and then stored in the line memory 7. ~10 is stored. On the other hand, the controller 13 is given information on the character image area and the halftone area in advance, and the controller 13 controls the selection of the selector 11 in accordance with this information. That is, for image data in the character image area, bit plane data B from the most significant bit (MSB) to 2 bits is used.
it3. Since transmitting Bit 2 is sufficient as image information, the selector 11 first transmits bit plane Bit 3.
The operation of transmitting a series of bit data corresponding to M pixels of information, and then transmitting a series of bit data of bit plane Bit2 for M pixels of information is repeated. In addition, for image data in the halftone area, all bits of bit plane data Bit
Since halftones can be reproduced satisfactorily by transmitting o''Bit3, the selector 11 repeats the operation of transmitting each series of hit data starting from bit plane Bit3 to bit plane BitO for each M pixel of information.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an image data transmission device according to an embodiment. In the figure, 1 is an image sensor (CCD) that reads the original image, 2 is an A/D converter that converts the analog signal output from the image sensor l into digital signals ADo to AD3 quantized with 4 bits per pixel, and 3
6 to 6 are encoders that perform coding compression using the Modified Huffman (MH) method on bit data for consecutive M pixels of each human brain; 7 to 10 are line memories (FIFOs) for temporarily storing encoded data; 11 is a selector that connects any one of encoded data Bit3 to Bito at input terminals A to D to output terminal O according to the control input of select terminal S, 12 is a data transmission buffer, and 13 is a controller for selector 11. .

In the configuration shown in FIG. 1, each pixel has 4 hits (
For simplicity of explanation, the image data A Do ” A D 4, which has been quantized with 16 gradations and 4 bits, is encoded and compressed by Modified Huffman (MH) encoders 3 to 6 for each bit plane, and is stored in a line memory. 7-1
Stored at 0. on the other hand.

The controller 13 is given information on the character image area and the halftone area in advance, and the controller 13 controls the selection of the selector 11 according to this information. That is, for the image data in the character image area, bit plane data Bit3. Since transmitting Bit2 is sufficient as character image information, the selector 11 first serially transmits the series of bit data M pixel information of bit plane Bit3, and then serially transmits the series of bit data M pixel information of bit plane Bit2. The operation of serially transmitting the data is repeated. In addition, in the case of a halftone image, the lower bit plane, especially the bit plane Bito
etc. are frequently 'o'.

“In order to repeat the bits of 1 pass, if this is MH encoded by encoder 6, on the contrary, this bit plane is A/D
The number of bits may be greater than the image data ADO from the converter 2. On the other hand, if one halftone dot image is a dithered image, the halftone information also appears on the upper bit plane, so there is an advantage in transmitting only the upper bit plane in such a case as well. Furthermore, for the image data in the halftone area, all bit plane data Bito
- If Bit 3 is transmitted, the halftone image will be reproduced well, so the selector 11 starts from bit plane Bit 3 and then selects the bit plane Bit.

The operation of serially transmitting each series of bit data iM pixel information is repeated.

FIG. 2 is a diagram showing a mode of MH encoding for each bit plane. In encoders 3 to 6, each A/D conversion output A
The run lengths of D3 to ADo are MH-transformed to form a coded compressed (MH) code.

FIG. 3 is a flowchart showing the control procedure of the controller 13. This flow is inputted by the generation of a synchronization signal 5YNC which has a certain relationship with the main scanning synchronization signal H3YNC of CCD 1. In step S1, it is determined whether the reading area is a character area. Whether or not an area is a character area can be specified in advance, for example, by specifying that lines A to B of the document are character areas. If it is determined in step S1 that it is a character area (or halftone image area), the process advances to step S2, where the selector 11 selects only S←A and B. Further, if it is determined in step S1 that the area is not a character area, the process proceeds to step S3, and the selector 11 is caused to select S, -A, B, C, and D.

FIGS. 4(a) and 4(b) are diagrams showing a mode in which the image data of each human brain is transmitted in one inclination. Since the image data of each bit plane has a variable length, the image information outside each M pixel is separated by a recoat 91.

FIG. 5 is a block diagram of another embodiment.

In this embodiment, only one encoder 3 is placed after the selector 11.

[Effects] As described above, according to the present invention, a pixel signal consisting of a plurality of bits is decomposed into bit screens (planes) for each bit, high-V rate encoding is applied to each bit screen, and transmission Since the bit screen to be transmitted can be arbitrarily selected, the total amount of data required for image transmission can be greatly reduced. For example, bit screens with a small amount of information (LSB and LSB)
Bits close to SB) are not transmitted, and screens with a large amount of information (bits close to SB) are not transmitted.
By selecting and transmitting only the bits near MSB and MSH, not only can the amount of data to be transmitted be greatly reduced, but also significant image deterioration occurs when the transmitted signal is decoded and the image is reproduced. High-quality reproduced images including halftones can be obtained without any problems.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing the image data transmission head of the embodiment, FIG. 2 is a diagram showing the mode of MH encoding for each bit plane, and FIG. 3 is a flowchart showing the control procedure of the controller 13. m4 Figures (a) and (b) are diagrams showing how image data of each bit plane is transmitted in sequence, and Figure 5 is a block diagram of another embodiment. In the figure, 1...image sensor (CCD), 2...A
/D converter, 3 to 6... Encoder, 7 to lO... Line memory (FIFO), 11... Selector, 12.
... Data transmission buffer, 13... Controller test.

Claims (2)

[Claims] (1) In an image data transmission device that transmits image data information quantized with N bits per pixel, the N
bit plane selection means for selecting one or more bit planes to be transmitted according to the image tone from the bit-quantized image data, and a series of bit data of the bit planes selected by the bit plane selection means. An image data transmission device characterized by comprising a data transmission means for transmitting data pixel by pixel. (2) The image data transmission apparatus according to claim 1, wherein the data transmission means includes data encoding means for encoding a series of bit data to be transmitted.