JPH02135578A - Picture signal processor - Google Patents

Abstract

PURPOSE:To extract the contour of picture information by converting an input signal to a digital picture signal, then cyclically shifting the digital picture signal, and collecting desired signal components on a first level side or a second level side. CONSTITUTION:The picture of an original picture 11 read by a scanner part 12 is outputted as a digital picture signal, applied to a cyclic shift device 13, and cyclically shifted for a prescribed level quantity. A binary processor 14 includes a threshold value setting circuit 15 and a comparator 16, a threshold value set at a threshold value setting circuit 15 beforehand is compared with a signal applied by the cyclic shift device 13 by the comparator 16, the applied signals are distributed to the first level or the second level, and binarized. Thus, the contour line of the picture signal can be suitably extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image signal processing device, and particularly to an image signal processing device including means for digitally processing an image signal.

For example, copying machines and facsimile machines can read original documents and reproduce or transmit the image in a desired state, but they are equipped with an image signal processing device that processes the read image signals. There is. This invention is
The present invention is aimed at improving such image signal processing devices.

<Prior Art> By the way, one of the signal processing performed by an image signal processing device is contour extraction processing. JP-A-6059484 discloses an image information contour extraction method as a prior art that is of interest to the present invention. As shown in FIG. 7, the method described in the patent publication performs two binarizations based on two thresholds Ll and L2 when image information is binarized, and the intermediate area of the two binarizations is performed. Only the signal components are extracted and the contour lines are extracted.

<Problem to be solved by the invention> In the image information contour extraction method described above, when binarizing, high
Two low thresholds Ll and L2 must be set,
Setting the threshold was difficult.

For example, if the image signal to be binarized is a signal of very light text written on a white background, or a signal of dark text written on a black background, the background and text The signal level difference between the Therefore, if the level difference between the two high and low thresholds Ll and L2 is too large, the eighth
As shown in the figure, the image signal cannot be binarized at two levels,
Unable to extract contour lines. In such a case, the level difference between the two thresholds may be made smaller, but if this level difference is made too small, the image signal may fluctuate somewhat due to noise, etc. It becomes difficult to accurately extract components in the intermediate region.

The present invention was made against the background of such prior art, and from a certain aspect, it is an image signal that can digitally process an image signal and easily and quickly extract the outline of image information in the signal. The purpose is to provide processing equipment.

Further, from another aspect, the present invention provides an image signal processing device that can accurately extract an information signal even when the input image signal has a small density difference between the information signal and the background signal. The purpose is to

Means for Solving the Problems> The present invention provides a conversion means for converting an analog image signal into a digital image signal, and a cyclic shift means for cyclically shifting the digital image signal converted by the conversion means by a predetermined amount. and binarization processing means for binarizing the cyclically shifted digital image signal based on one predetermined threshold value.

In the above image signal processing device, the image signal is a first
It includes a component that changes from the level side through the intermediate level to the second level side, and the amount shifted by the cyclic shift means is determined by whether the signal component on the second level side moves to the first level side or the signal component changes from the first level side to the first level side. the signal components on the side are selected to move to the second level side, thereby transferring the signal components on the first level side and the second level side to the first level side or the second level side.
The signal components in the intermediate region can be shifted to the opposite level side, and the binarization processing means can shift the signal components to the first level side and the second level side based on the one predetermined threshold value.
It is preferable that the signal components on the level side and the signal components in the intermediate region are differentiated and binarized, and only the signal components in the intermediate region can be extracted and output.

Further, in the image signal processing device, the image signal includes a component with a small level difference between the information signal and the background signal, and the amount shifted by the cyclic shift means is a first
level or the amount of level from the second level to the background signal, which allows the information signal to be shifted toward the first level or the second level and the background signal toward the opposite level. , the binarization processing means distinguishes and binarizes the information signal concentrated on one level side and the background signal concentrated on the other level side using the one predetermined threshold value, and The signal may be extracted and output.

In the image signal processing device according to any of the above, in order to determine the amount of shift by the cyclic shift means, the document content is prescanned, the density distribution thereof is detected, and the shift amount is calculated based on the prescanning. Even if you include the means.

Effect> The digital image signal converted by the converting means is cyclically shifted by adding or subtracting a predetermined amount of signal by the cyclic shifting means. By adjusting the amount of cyclic shift, a certain signal component can be shifted toward the first level side (for example, the black level side), and a certain signal component can be shifted toward the second level side (for example, the white level side).

Therefore, by setting one threshold between the first level side and the second level side, the cyclically shifted digital image signal can be binarized based on the threshold value.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a digital copying machine employing an embodiment of the present invention.

The digital copying machine is equipped with a scanner unit 12 for reading an image of an original image 11. The scanner unit 12 is equipped with an image sensor such as a CCD, and the read image of the original image 11 is output as a digital image signal of, for example, 8 bits and 256 levels. Scanner section 1
The output of 2 is applied to a cyclic shift device 13, in which the digital image signal is cyclically shifted by a predetermined level amount. Cyclic shift means, for example, from 0 steps (first level) to 255 steps (
For example, a signal divided into 256 stages up to the second level (2nd level) is shifted by a certain level (for example, 20 stages) from the first level side to the second level side, and data overflowing from the 255th stage is returned from the 0th stage side. Shifting data cyclically.

The 8-bit digital data that has been cyclically shifted by a predetermined amount in the cyclic shift device 13 is binarized in the binarization processing device 14. The binarization processing device 14 includes a threshold setting circuit 15 and a comparator 16, and uses the threshold value set in advance in the threshold setting circuit 15 and the signal given from the cyclic shift device 13. The comparator 16 compares the given signal with the first
Sort into level or second level and binarize.

The output of the binarization processing device 14 is a 1-bit signal consisting of a combination of the first level or the second level, and this output is given to the printer section 17.

The printer section 17 includes known image forming mechanisms such as a semiconductor laser, a polygon mirror for scanning light, a photoreceptor, and a developing device. The printer section 17 forms an image based on the output of the binarization processing device 14, and as a result,
Copy 18 is obtained.

FIG. 2 is a block diagram showing the detailed configuration of the scanner section 12. As shown in FIG. The scanner unit 12 is equipped with an objective lens 121, and the data of the original image 11 is transmitted through the objective lens 121.
It is given to CD122.

The CCD 122 converts the optical signal into an electrical signal, and even
and the odd signal are provided to amplifiers 123 and 124, respectively. The signals amplified by amplifiers 123 and 124 are converted into digital signals by A/D converters 125 and 126, respectively, and both signals are combined by a combiner 127. The output of the synthesizer 127 is then given to a correction circuit 128, where shading correction, density correction, etc. are performed, and then output as an 8-bit digital signal.

The detailed configuration of the scanner section 12 is not limited to the configuration shown in FIG. 2, and other configurations may be adopted.

FIG. 3 is a circuit block diagram showing an example of the cyclic shift device 13. The cyclic shift device 13 is
For example, eight full adders 21a.

21b, 21c, 21d, 21e, 21f, 21g, 2
The 8-bit digital image signal supplied from the scanner section 12 is connected in parallel for 1h, and the most significant digit is supplied to one input terminal A of the full adder 21a, and the next and subsequent digits are sequentially connected to the corresponding full adder. Input terminal A of devices 21b to 21g
The least significant digit of the 8-bit data is supplied to the input terminal A of the full rounder 21h.

On the other hand, each corresponding digit of the subtraction data is applied to the other input terminal B of each of the full adders 21a to 21h via an inverter 22. Therefore, the eight full adders 21a to 21h shift the 8-bit data by a predetermined level based on the subtracted data and output it.

FIG. 4 is a signal waveform diagram for explaining one of the features of the device shown in FIG. 1.

To explain with reference to FIGS. 1 to 4, the 8-bit digital image signal output from the scanner section 12 is
For example, it is assumed that the signal component shown in FIG. 4 (A1) is included. In this waveform diagram, the bottom is 0 as the first level.
The white level of the rows and the top represent the black level of 255 steps as the second level. This signal component is cyclically shifted in the cyclic shift device 13 and is converted into the signal shown in FIG. 4 (A2). In other words, the signal component is cyclically shifted by a predetermined amount toward the black level.

As a result, the white and black components of the input signal are concentrated on the white level side, and the signal components in the intermediate region are concentrated on the black level side.

Threshold setting circuit 15 provided in the binarization processing device 14
One threshold value is set in the middle between the black level and the white level. Therefore, the threshold value and Figure 4 (A2
) and performs binarization processing, the result shown in Figure 4 (
A binarized signal of A3) is obtained. What appears as a high level signal in this signal is the signal component in the intermediate region in FIG. 4 (A1).

By extracting the signal component of this intermediate region, the contour line of the image information can be extracted as described in the above-mentioned Japanese Patent Laid-Open No. 60-59484.

In the cyclic shift device 13, instead of shifting the digital signal (A1) in FIG. 4 given from the scanner section 12 to the black level side, it can also shift it to the white level side. The signal waveform in this case is shown in Figure 4 (B
Shown in 1). By shifting to the white level side, the black level side component and the white level side component of the input signal can be concentrated on the black level side, and the intermediate region component can be left on the white level side. Therefore, when the cyclically shifted image data is binarized, only the outline of the image information can be extracted in white, as shown in FIG. 4 (B2).

Note that instead of changing the cyclic shift direction in the cyclic shift device 13, the output of the binarization processing device 14 may be inverted using a level inverter.

FIG. 5 is a signal waveform diagram for explaining other features of the apparatus shown in FIG. 1, and shows a case where the signal components output from the scanner section 12 have a small difference in density level. For example, FIG. 5 (A1) shows the output components of the scanner unit 12 when an original image 11 with very light-density characters written on a white background is read. Further, FIG. 5 (B1) shows the output components of the scanner unit 12 when an original image with red, blue, etc. characters drawn on dark paper is read. In such case,
Since the density level difference between the background signal and the character signal is small, it is not possible to properly binarize the signal as it is. Therefore,
By cyclically shifting the signal components to the black level side or the white level side, the background signal can be moved to the black level side and the character signal to the white level side (Figure 5 (A2)), or the background signal can be moved to the white level side. In addition, the character signal is shifted toward the black level side (Fig. 5 (B2)). In other words, the amount to be shifted by the cyclic shift device 13 is selected to be slightly larger than the level difference between the white level and the background signal, or
The amount is selected to be slightly larger than the level difference between the black level and the background signal.

As a result, by comparing the threshold value set between the black level and the white level and the signal component after the cyclic shift, as shown in FIG. 5 (A3) or (B3),
Signal components can be binarized into background signals and character signals.

FIG. 6 is a block diagram showing an example of a shift direction and shift amount determining circuit for cyclic shifting. The scanner unit 12 performs pre-scanning and scanning of the original image 11,
The 8-bit signal output from the scanner section 12 is given to the pre-scan RAM MB2 in FIG. 6, and the 8-bit signal is temporarily stored in the pre-scan RAM 31. A density distribution meter/measuring circuit 32 connected to the prescan RAM 31 measures the density distribution of the 8-bit signal in the RAM 31 and provides its output to an arithmetic circuit 33 and a comparator 34. Comparator 3
A threshold value setting circuit 35 is connected to 4, and a predetermined threshold value is given from the threshold value setting circuit.

The comparator 34 compares this threshold value with the output given from the concentration distribution meter fullJ circuit 32 and outputs the result to the arithmetic circuit 33.

The calculation circuit 33 performs calculations based on the signal provided from the concentration distribution measurement circuit 32 and the signal provided from the comparator 34 to calculate the direction of cyclic shift and the amount of shift. The output of the arithmetic circuit 33 is given to the cyclic shift device 13.

In the above embodiments, the input signal was first converted into a digital image signal and then cyclically shifted. The reason for this is that cyclic shifting can be easily performed with digital signals, and the cyclic shift device that implements it has a simple configuration. This is because it is fine.

However, the analog signal may be cyclically shifted as it is, and the cyclically shifted analog signal may be binarized based on one predetermined threshold value.

<Effects of the Invention> The present invention is configured as described above, and after an input signal is converted into a digital image signal, the digital image signal is cyclically shifted to the second level side or the second level side. Since desired signal components can be gathered together, the signal can be binarized into a desired state based on one threshold value. Therefore, it is possible to extract the outline of an image signal, or to accurately extract a signal even if the difference in density level between the background signal and the information signal is small.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a digital copying machine employing an embodiment of the present invention. FIG. 2 is a block diagram showing the detailed configuration of the scanner section 12. As shown in FIG. FIG. 3 is a diagram showing a specific circuit example of the cyclic shift device. 4 and 5 are waveform diagrams for explaining the operation of the apparatus shown in FIG. 1. FIG. 6 is a block diagram showing an example of the configuration of a circuit that determines the direction and amount of cyclic shift by pre-scanning. FIG. 7 is a waveform diagram illustrating a conventional image information contour extraction method. FIG. 8 is a diagram for explaining problems in the conventional image information contour extraction method. In the figure, 11...original image, 12...scanner section,
13... Cyclic shift device, 14... Binarization processing device, 5... Threshold setting circuit, 1... Full adder, 2... CCD. 6...A/D converter. 6... Comparator, 25° Mita original data conversion data

Claims (1)

[Claims] 1. Conversion means for converting an analog image signal into a digital image signal; cyclic shift means for cyclically shifting the digital image signal converted by the conversion means by a predetermined amount; An image signal processing device comprising: binarization processing means for binarizing the shifted digital image signal based on one predetermined threshold value. 2. The image signal processing device according to claim 1, wherein the image signal includes a component that changes from the first level side through the intermediate level to the second level side, and is shifted by the cyclic shift means. The amount is selected such that a signal component on the second level side is transferred to the first level side, or a signal component on the first level side is transferred to the second level side, thereby causing a difference between the first level side and the second level side. Move the signal component on the level side to the first level side or the second level side,
The signal component in the intermediate region can be shifted to the opposite level side, and the binarization processing means can shift the signal component on the first level side and the second level side and the intermediate region based on the one predetermined threshold value. It is characterized by being able to distinguish and binarize the signal components of the region, and extract and output only the signal components of the intermediate region. 3. The image signal processing device according to claim 1, wherein the image signal includes a component with a small level difference between an information signal and a background signal, and the amount shifted by the cyclic shift means is a first level or a background signal. is selected based on the level amount from the second level to the background signal, whereby the information signal can be shifted to the first level side or the second level side, and the background signal can be shifted to the opposite level side, The binarization processing means distinguishes and binarizes the information signal concentrated on one level side from the background signal concentrated on the other level side using the one predetermined threshold value, and converts the information signal into a binary value. It is characterized by being able to extract and output. 4. In the image signal processing apparatus according to any one of claims 1 to 3, in order to determine the amount of shift by the cyclic shift means, the document content is prescanned and its density distribution is detected. The present invention is characterized in that it includes means for calculating a shift amount based on the shift amount.