JPH0373670A - Facsimile equipment - Google Patents

Abstract

PURPOSE:To transmit much image information within a short time by generating a screen for expressing the density of picture elements by the number of bits smaller than the number of quantized bits of multivalued information read out by a scanner and compressing output data. CONSTITUTION:Data corrected by an image processing part 2 are inputted to an error distributing device (screen generator) 6 to execute processing for expressing the image of 256 gradations by the number of bits (i.e., 4 bits) smaller than 8 bits. In the screen generator 6, signals supplied from an image processing part 2 and an error detector 63 are added to an adder 60. A comparator 61 compares the thresholds of plural stages supplied from a threshold generator 62 with the output of the adder 60. Consequently, binary data '0' or '1' corresponding to the output of the adder 60 smaller or larger than the threshold are inputted to a coder 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a facsimile machine, and in particular,
The present invention relates to a facsimile device suitable for obtaining high image quality equivalent to that of a digital copying machine with a large number of quantization bits.

(Conventional technology) FIG. 5 shows the configuration of a conventional digital copying machine.

In the configuration shown in FIG. 4A, the analog No. 78 of the original image read by the CCD scanner 1 is A/D converted and quantized into, for example, an 8-bit signal. The image processing section 2 performs processing such as correction according to the characteristics of the scanner 1 including the optical system, and the processed signal is supplied to the recording device 3 as an 8-bit signal.

The recording device 3 records an image of a desired density by modulating a recording device such as a laser diode according to the 8-bit signal.

Furthermore, in the configuration shown in FIG. 5(b), after the output of the image processing section 2 is converted into binary data (1-bit signal) by the binarization circuit 4, this 1-bit signal is supplied to the recording device 3. I try to do that.

The former configuration is a system in which image information is expressed as 8-bit information with 256 gradations, and the 8-bit signal can be recorded as is by the recording device 3, so that high image quality can be reproduced.

On the other hand, since the latter configuration is a method that binarizes and records the image number 1M, the configuration of the recording device 3 that accepts and processes this binary signal can be simplified, and as a result, a low-cost copying machine can be used. We were able to realize this.

Although the above configuration relates to a copying machine, a multifunction machine that has both the functions of a copying machine and a facsimile machine is generally known.

(Problems to be Solved by the Invention) By the way, when the above-described copying machine is combined with a facsimile machine to form a multifunction device, the following problems occur.

In other words, when a copying machine like the one shown in Fig. 5(a) is connected to a facsimile machine, one pixel is expressed with 8 bits, so while it has the advantage of providing high image quality, it also has the disadvantage that it is difficult to express the image. Since there is a large amount of information to be transmitted, there are problems in that the information transmission time becomes long and a large capacity memory is required to store the large amount of information.

On the other hand, when a copying machine as shown in Fig. 5(b) is connected to a facsimile machine, the read image is simplified to binary data, so the image shown in Fig. 5(a) is Compared to the configuration of a copying machine, the amount of information needed to represent the same image is small.

Therefore, the information transmission time in communication is short, and the memory capacity for storing information may also be small.

However, in the latter case, since the image is expressed in binary 1-bit format, there is a problem in that it is not possible to obtain the same high image quality as in the former case, in which the image is expressed in 256 gradations and 8 bits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a facsimile device which can solve the above problems, easily transmit images, and reproduce the transmitted images with high quality.

(Means and Effects for Solving the Problems) In order to solve the above-mentioned problems and achieve the objects, the present invention aims to increase pixel density by using a bit number smaller than the quantization bit number of multi-level information read by a scanner. a screen generator for expressing data, a coder for compressing output data of the screen generator, means for bit-plane encoding the output of the coder and transmitting it to a line, It is characterized in that it is equipped with means for expanding the data into multivalued information and supplying it to the recording device.

In the present invention having the above configuration, it is possible to compress multilevel information and express an image with a small number of bits, so that a large amount of image information can be transmitted in a short time. Furthermore, the transmitted information can be expanded again into multivalued information and recorded, making it possible to achieve high image quality.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a facsimile machine showing one embodiment of the present invention.

In the figure, an analog output from a CCD sensor 1 for image reading is converted into 8-bit 256-gradation data by an A/D converter 5 and input to an image processing section 2. The data corrected by the image processing unit 2 is input to an error diffusion device (hereinafter referred to as a screen generation device) 6 to generate a 256-gradation image using fewer bits than 8 bits (in this embodiment, 4 bits).
Processing is performed to express it in bits).

In this screen generating device 6, an adder 60 adds the signals supplied from the image processing section 2 and the error detector 63. The comparator 61 uses multiple stages (four stages in this embodiment) supplied from the threshold generator 62.
The magnitude of the output of the adder 60 with respect to the threshold value is compared. As a result, binary data of "0" or "1" is input to the coder 7 depending on whether the output of the adder 60 is below the threshold value or above the threshold value. Since there are four threshold values, the comparator 61 outputs the comparison results of the output of the adder 60 with respect to each threshold value, that is, four comparison results (4 bits).

In the error detector 63, according to the comparison result in the comparator 61, if the comparison result is "1", an error between the true value and the threshold is detected, and if the comparison result is "θ", the difference is detected by one step from the true value. An error with the lower threshold is detected. The detected error is fed back to the adder 60 and added to the output from the image processing section 2.

An example of data conversion by the screen seating device 6 having the above configuration will be explained with reference to FIG. 2. In FIG. 2, the horizontal axis is the time axis, and the vertical axis shows the degree of density of each pixel. Here, in order to simplify the explanation, one of the four thresholds
An example of conversion of image data of the same density level in the vicinity of two threshold values TH is shown.

First, since the density level of pixel number pxO is lower than the threshold value TH, data "Ow" is output to the coder 7. Then, the error e between the true value at this time and the "0" level
l, that is, the same value as the input level, is added to the next pixel pxl. Then, since the pixel pxl exceeds the threshold value TH, the output data becomes "1". The error el between the true value and the threshold value TH at this time is added to the next pixel px2.

Thereafter, similarly, depending on whether the output data is "0" or "1", the error of the input data with respect to "0 level" or the threshold value TH is detected and added to the subsequent pixels.

In this way, the 8-bit pixel data supplied from the image processing section 2 is added with the error that occurs when this pixel data is converted into 4-bit data. Therefore, since the error of the previous pixel data is reflected in the pixel data, in a certain area, the pixel data approximates the data representing the true image.

That is, in the above example, if the error is not added, the original input data (pxo to px9) are all data below the threshold TH, so even though they actually have a concentration level near the threshold TH. However, all output data becomes "0". On the other hand, when the error is fed back and added to the original input data, as shown in the figure, out of the output data indicating pixels pxO to px9, there are two "O"s, eight 1#s, and so on, and the pixel pxO When viewed through ~px9, it is possible to express an image density that can be considered to be almost the same as the true value.

Now, as described above, when 8-bit data is converted to 4-bit data and input to the coder 7, the coder 7 compresses the 4-bit data into 2-bit data.

The 4-bit data is assigned to, for example, four density types as shown in FIG. In the same figure, bits 0~
If all bits up to bit 3 are "0", it indicates white, and if all bits are "1", it indicates black.

Others are as shown. The bit data for compressing this 4-bit data into 2-bit data is as shown in FIG.

The data compressed to 2 bits according to the relationships shown in FIGS. 3 and 4 is sent to the image memory 9 via the selector 8.
and is input to the image memory 1 and stored.

The selector 8 connects the coder 7 and the image memories 9 and 11 when transmitting data, and connects the image memory 9 when receiving data.
, 11 and the decoder 14.

That is, at the time of data transmission, the 2-bit data is decomposed into a 1-bit signal compatible with the facsimile machine, so of the 2-bit data, bit 0 data is stored in the image memory 9, and bit 1 data is stored in the image memory 11. is stored in In this way, each bit is stored as one image in the image memory9.11 as a bit plane image.
The image data stored in is compressed by compression/expansion devices 10 and 12, respectively. The compressed data is first transferred to one of the image memories 9 and 11 by the transmission/reception control device 13.
is sent out to the line, and then the other image data is sent out.

Note that when transmitting image data to a line, it goes without saying that it is communicated to the other station using a protocol that the image data constitutes a set of two images.

On the other hand, data received via the line and transmission/reception control device 13 is expanded by compression/expansion devices 10 and 12, respectively, and stored in image memories 9 and 11. image memory 9,
The data stored in 11 is sequentially read out and input to decoder 14 via selector 8. The decoder 14 performs the opposite conversion (expansion) to the data conversion performed by the coder 7, and outputs 4-bit data.

Based on this 4-bit data, a pulse width for lighting the recording laser diode of the recording device 3 is set. Then, in the recording device 3, the laser diode is turned on for a scheduled lighting time according to this pulse width, and an image having a desired density is recorded.

Note that if the image data read by the scanner 1 is not transmitted but is simply copied by the recording device 3,
The output of the screen generator 6 can be directly supplied to the recording device 3 by switching the front switch S to the opposite side from the illustrated state.

Next, an example of bit-plane encoding of a document image will be explained. In Figure 6, there are four types of manuscript DOC (white, gray, 1
．． Ash 2. An example of the case where the density type (black) is included is given as an example. When such a document DOC is recorded using a conventional facsimile machine, the black part and the gray 2 part, which is close to black, are uniformly recorded as black, as shown in FIG. The gray 1 portion is uniformly recorded as white.

On the other hand, in the facsimile machine of the present invention, the image data of the original DOC is expressed as 2-bit data as shown in FIG. It is developed as an image. The numbers in the figure indicate bit data.

The image data of bit O representing each density is shown in the same figure (C
), and the image data of bit 1 is shown in (d) of the same figure.

When these two images are combined and recorded, the original document DO
Images faithful to C can be reproduced.

In this embodiment, the amount of information representing the density of the pixel is compressed using a screen generator that converts the 8-bit data input from the image processing section 2 into 4-bit data. Not limited. In short, the screen generator can output data that can express the density of one pixel using data with a smaller number of bits than the number of quantization bits of the scanner read data supplied via the image processing section 2. good.

As described above, in this embodiment, the multivalued data read and quantized by the scanner device is transferred to the screen generator 6.
Therefore, the data is compressed into multi-level data with a smaller number of bits than the number of quantization bits.

The multivalued data compressed by the screen generator 6 is further compressed by the coder 7 so that the compressed data can be decomposed into 1-bit data compatible with facsimile machines using bit plane representation. Therefore, it has become possible to transmit multi-valued image data with less error relative to the true image density using a facsimile machine.

(Effects of the Invention) As is clear from the above description, according to the present invention, an image can be expressed using data with a smaller number of bits than the number of quantized bits in the scanner device, and even though the number of bits is smaller, High-quality recording that approximates the image expressed by the number of quantized bits in a scanner device can be obtained. Further, the data can be transmitted by a facsimile machine after further compressing the amount of information, and a high-quality image can be reproduced at the destination.

In this way, by combining a copying machine capable of reproducing high image quality with a facsimile machine, an inexpensive multifunction device can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of data conversion in a screen generator, and FIGS. 3 and 4 show bit data and density types and examples of bit data allocation. FIG. 5 is a block diagram showing the configuration of a digital copying machine, and FIG. 6 is an explanatory diagram of bit plane encoding. DESCRIPTION OF SYMBOLS 1...Scanner, 2...Image processing unit, 3...Recording device, 6...Screen generation device, 7...Coder,
8... Selector, 9.11... Image memory, 10.
12...Compressor/expander, 14...Decoder

Claims (1)

[Claims] (1) In a facsimile machine having a recording device that is supplied with multi-value data quantized according to the original density and reproduces an image of a desired density based on the data, it reads the original image and converts each pixel into multi-value data. a screen generator that outputs data expressing the density of one pixel with a smaller number of bits than the number of quantization bits in the scanner; and a screen generator that compresses the output data of the screen generator. a coder for bit-plane encoding the output of the coder and sending it to a line; and a means for expanding bit-plane-encoded data input from the line into multi-level information and supplying it to the recording device. A facsimile machine characterized by: