JPS62241081A - Thinning device for picture signal - Google Patents

Abstract

PURPOSE:To perform recording without deteriorating the quality of picture data obtained before thinning by setting a picture element correcting circuit at the preceding stage of a thinning circuit and always securing at least a single picture element of the input picture data obtained before thinning. CONSTITUTION:The output time width of a monostable multivibrator MMV11 is decided by the density of the main scan line of input picture data. The output signal of the MMV11 is ORed with the input picture data via an OR gate 12 and an output signal (c) is sent to a thinning circuit 2 and then inputted to line memories A and B of the circuit 2 respectively to be written and read by the write and read address clocks (d) and (e) respectively. The both memories A and B are switched with each other by the memory switch signal (h) and the thinned signals are delivered from an OR gate 23 of the circuit 2 after correction of the picture element width. In such a way, the signal thinning is carried out after correction of the picture element width, therefore the minimum picture element of the input picture data is not deleted and remains.

Description

[Detailed Description of the Invention] Industrial Field of Use The present invention is used to thin out image signals (image data) from the host CPU (central processing unit) of a galley printer for monitoring during newspaper production, which can be sent to newspaper companies, etc. The present invention relates to a suitable image signal thinning device.

2. Description of the Related Art A conventional image signal thinning technique of this type will be explained by taking as an example thinning of main scanning line density, which is commonly used in newspaper companies and the like.

Now, if we consider two types of linear densities, 454 lines/inch and 681 lines/inch, a galley printer (electrostatic recording device) is made with a performance of 454 dots and 7 inches, and 681 lines/inch. From the data of (454=
681 x 2/3) Digital thinning at a ratio of 1 to 3 bits can be used to obtain a line density of 454 lines/inch.

The most desirable option is to switch to 454 lines/inch or 681 lines/inch of recording elements, but it is possible to manufacture a galley printer (electrostatic recording device) etc. with a recording head equipped with 681 lines/inch of recording elements. It is difficult to
This is because even if it could be manufactured, it would be impossible to combine two recording elements, one for 464 lines/inch and one for 681 lines/inch, into a recording head.

Therefore, a method of digitally simply thinning out one bit out of three bits of input image data is adopted.

Problem to be solved by the invention However, if one bit out of three bits is simply thinned out digitally (when thinning out 681 lines/inch to 454 lines/inch), the thinned out 1 bit contains valid data. If so, the valid data will be deleted and will no longer appear in the record. FIG. 4 is a diagram for explaining the above-mentioned relationship.

In other words, according to the conventional thinning means, when image data (white circle bits) is thinned out in the main scanning direction at a ratio of 1 bit to every 3 bits, as shown in the figure, the thinned out portions (
If valid data (black information) exists in the black circle mark),
There is a problem that when recording, the areas containing black information (black circles) change to white information (white circles) and are not recorded.

Therefore, the present invention divides image data into m pieces in the main scanning direction.
(n<mSm, n is an integer), if valid data exists among the n data that has been thinned out, then
It is an object of the present invention to provide an image signal thinning device in which the data always appears on the record without being deleted.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a pixel width of t bits set in advance at the leading edge of a black bit in all input image data (black data is 1). A pixel correction means (having a width at least one bit larger than the width to be thinned out) to secure a pixel width is provided at the front stage of the thinning means (means for thinning out image data at a ratio of m to n pieces), At least one pixel of the image data before thinning can be secured during thinning.

Operation Since the present invention provides the pixel correction means before the thinning means, the pixel width of the image data before thinning is ensured to be larger than the thinning width. Therefore, when thinning out,
At least one pixel of the image data before thinning remains without being deleted. Therefore, it is possible to perform recording without impairing the image quality of the image data before thinning.

Embodiment FIG. 1 is a block diagram showing a schematic structure of an image signal thinning device according to the present invention, and FIG. 2 is a circuit diagram showing a specific example of the structure of FIG.

In Figures 1 and 2, 1 is applied to the front edge of all input image data (black data is 1) with a width smaller than the width to be thinned out (both 1
This correction circuit 1 is a pixel correction circuit for securing a pixel width by adding a pixel width of t bits or more, which is larger than t bits.
MMV for presetting the t-bit pixel width
(Monosmople Multivibrator) 11 and its M
It comprises an OR gate 12 that adds a pixel width of t bits from MVll to the leading edge of the input image data.

2, the image data (a pixel width of t bits is secured) from the pixel correction circuit 1 is divided into m pieces and n pieces (
n<m, m, n is an integer) This thinning circuit 2 has two line memories IJA and B and an AND gate 21.2 connected to the line memories A and H, respectively.
2 and the outputs of its AND gates 21 and 22.
It is composed of an R gate 23 and the like.

FIG. 3 shows signal waveforms at each part (a=f) of the circuit shown in FIG. In the figure, g is the waveform of an output signal thinned out (by conventional thinning means) without pixel width correction, and is shown for reference.

Next, the operation of the circuit shown in FIG. 2 will be explained with reference to FIG.

When the image data (waveform &) before thinning is input to the pixel correction circuit 1, the MMVI 1 outputs a signal of waveform &.

Here, the input image data is a digital signal (NRZ) such as a facsimile image signal, and MMVl
The output time width of 1 is determined by the main scanning line density of input image data. In this embodiment, the output time width is set to twice the time width of one pixel of the line density.

The output signal (waveform b) from the MMVII is ORed with the input image data (waveform a) by the OR gate 12, and the output signal (waveform b) is outputted from the waveform C.
is output as a signal. The output signal (waveform C) is the output signal of the pixel correction circuit 1 (image data with a pixel width of t bits secured).

The output signal (waveform C) of the pixel correction circuit 1 is input to the line memo 'JA and B of the thinning circuit 2, respectively, and is used as a write address clock (waveform d) and a read address lock (waveform d).
It is written/read by waveform e).

Note that switching between the two memories is performed by a memory switching signal. Further, at the time of reading, the addresses marked with X of the write address clock (waveform d) are thinned out and the addresses to the right are sequentially shifted.

Thus, the OR gate 23 of the thinning circuit 2 outputs a thinned signal (waveform f) after pixel width correction.

As is clear from the comparison between the output signal (waveform f) and the output signal (waveform g) from the conventional thinning means,
According to the present invention, since the thinning is performed after the pixel width correction as described above, the smallest pixel of the input image data (waveform &) remains without being deleted. In other words, thinning (at least one pixel of the previous input image data is always secured).

Effects of the Invention As is clear from the above explanation, in the present invention, the pixel correction means is provided before the thinning means, so at least one pixel of the input image data before thinning is always secured, and the image before thinning is This has the effect that data can be recorded without degrading the image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image signal thinning device according to the present invention, FIG. 2 is a circuit diagram showing a configuration example embodying FIG. 1, and FIG. 3 is each part of the circuit shown in FIG. 2. FIG. 4 is a conceptual diagram for explaining the conventional thinning means. 1...Pixel correction circuit, 11...MMV
(Monosmoble Multivibrator), 2...
・Thinning circuit. Name of agent: Patent attorney Toshio Nakao et al. 12th
1 Figure M 2 - Lead memo, rikiri @a 7 dress 2 pieces 97 1 in π 1 f 3rd rg for γ! J Bigo, TA Figure 11, the owner of your order, ○○ 弡) Kte Ruco-1 ---c.

Claims (1)

[Claims] Image data is divided into m and n pieces in the main scanning direction (n<m, m, n
, is an integer), is provided with a pixel correction means that adds a pixel width of t bits, which is at least one bit larger than the width to be thinned out, to the leading edge of all input image data. Image signal thinning device.