JPH0353765A - Picture processing device - Google Patents

Abstract

PURPOSE:To execute picture processing with high quality by providing a selection means receiving a picture discrimination signal, an area designation signal and an indication signal and passing selectively the processing result of character picture processing, contour processing, half-tone processing or gradation picture processing. CONSTITUTION:An optical image obtained by scanning an object (original) 1 optically is led to a picture read section 3 via a lens system 2 and converted into an electric signal (picture signal). The picture signal is converted into a digital picture signal in a prescribed bit at an D/A converter 4. Then only a digital picture signal corresponding to a required area (e.g. B4 size) is selected by an effective area extraction section 6. The digital picture signal is subject to resolution correction with MTF correction by a resolution correction section 7. Then the digital picture signal is fed to a picture processing section 8, where the picture processing (multi-value processing of binary or over) different from a character picture and a gradation picture is executed. The digital picture signal subject to multi-value processing is fed to a printer 10 such as electrophotographic type and the picture is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image processing device suitable for a digital copying machine, and more specifically, to an image processing device that has excellent i-distinction and reproducibility of both character strokes and gradation. The present invention relates to an image processing device.

(Background of the Invention) Generally, in an electrophotographic digital copying machine,
The image information (original image) of the original is divided into micropixels of approximately several tens of microns, the electric signal (image signal) corresponding to the density of each pixel is converted into a digital signal, and the digital image signal is processed internally. After conversion, the image is output to a recording device such as a laser, and a copy image is obtained through an electrophotographic process.

In such digital copying apparatuses, internal signal processing is often changed depending on the type of input image.

For example, when the input image is a so-called general document such as a book or a letter, the density of the characters and the color level of the background are not so important, and it is desired that the characters be reproduced sharply.

Therefore, in the case of a printer whose output is only binary (on and off), the input image information is binarized at a certain fixed level to reproduce the image. In the case of a printer capable of multi-value recording according to density, character images can be reproduced clearly by controlling the printer with emphasis on white and black output.

On the other hand, when the input image has so-called gradation, such as a photographic image, it is important to reproduce the intermediate image.
This is different from when the purpose of processing is mainly text.

For example, in the case of a binary printer, a pseudo halftone image is formed using a well-known method such as a dither method or a density matrix method, and the image is reproduced using the output. Even in the case of multilevel printers, the output characteristics are often designed to emphasize the reproduction of halftones.

Furthermore, especially in these processes, halftone drawings often used in newspapers and the like require special processing. Halftone drawings are made up of many dots, and when viewed microscopically, they do not have any mid-tone areas and are similar to character drawings.

However, since the original purpose of halftone drawings is to reproduce pseudo-halftones using dots of different sizes, it is often easier to see the output if it is reproduced as a gradation image similar to that of a photographic image. Furthermore, a certain number of lines among halftone dots is very close to the sampling pitch used in the image reading system and writing system of digital copying devices that are currently widely used.

For example, when the sampling pitch is 16 dat/mm and the number of mesh lines is 133 lines/inch, the number of mesh lines is quite close to the sampling pitch.

Under such conditions, an aliasing error occurs in sampling, which appears as a so-called moiré image, resulting in a significant deterioration in image quality. For the moiré draft, the original image is 2li
This phenomenon appears particularly clearly when ii processing is performed, but even when pseudo-intermediate representation such as dithering is used, the frequency of occurrence only decreases and does not disappear completely.

As a countermeasure to this problem, it is possible to reduce the high frequency components of the original image to reduce interference with the sampling pitch. Specifically, it is sufficient to perform smoothing using surrounding pixels.

As described above, by switching the coefficients for image processing and multi-value conversion according to the characteristics of each image, the output image can be maintained in high quality. Normally, these switching is performed by the operator himself by switching the processing mode depending on the document.

However, when copying a document such as a pamphlet that has different features such as text and photos in one image,
If text and image processing is set, the reproducibility of photographic parts will be lost, making it impossible to obtain a copy that satisfies both parties. Therefore, the overall copy quality is not good.

In order to solve this problem, it is sufficient to distinguish whether the input image information is a character image or a first-order image, and to switch the processing based on the result of the determination.

Conventionally, the so-called block-by-block discrimination method, which divides the original image into several small blocks and switches processing based on the discrimination results for each block, has been used as a means of discriminating whether it is a character image or a gradation image. ``Binarization processing method for manuscripts containing a mixture of value images and gray scale images'' (IEICE Journal VOI,
．． J67-B No. 7 (1984) I) p781
-788), and a so-called pixel-by-pixel discriminating method in which processing is performed on a pixel-by-pixel basis, even if information on surrounding pixels is incorporated, is known, for example, the technique described in Japanese Patent Application Laid-Open No. 82-104372.

(Problem to be Solved by the Invention) Among the above-mentioned discrimination means, a discrimination method that discriminates each block includes, for example, checking the dispersion of density within the block of interest, and if the dispersion is large, determining that it is a character stroke. There are methods. According to this discrimination method, if an incorrect discrimination is made, all of the blocks will be processed incorrectly, resulting in a severe deterioration in quality.

Furthermore, in general, block-by-block discrimination requires more memory to temporarily store image data than pixel-by-pixel discrimination, is expensive, and has the drawback that the signal processing thereof is also complicated.

On the other hand, the pixel-by-pixel ill separation method has advantages such as having fewer side effects of misclassification and requiring relatively little memory, but this method is difficult to distinguish between clear characters and photographs that have already been printed. It belonged to Therefore, no process has yet been proposed that automatically discriminates even characters with shading, such as halftone drawings and general handwritten characters.

Also, when performing outline processing or shading processing, characters. Character area of mixed picture of photo. Also, no device has been proposed that executes processing only on a designated area.

The present invention has been made in view of the above-mentioned problems, and its purpose is to enable image processing of halftone drawings without deteriorating the image quality, and to simplify the circuit configuration at that time. The objective is to realize an image processing device that executes high-quality image processing that is suitable for the characteristics of each image area of a mixed image, and that can perform outline processing and shading processing only on necessary parts of character areas. .

(Means for Solving the Problems) The present invention to solve the above-mentioned problems includes a character image processing means for converting an image signal obtained by scanning a document into a multi-value signal of two or more values through character image processing; contour processing means that receives the output of the character image processing means and performs outline processing on the character portion of the image signal; and shading processing means that receives the output of the character image processing means and performs shading processing on the character portion of the image signal. , a gradation image processing means for converting an image signal obtained by scanning a document into a multi-value signal of two or more values through gradation image processing, and a gradation image processing means for discriminating the image into a gradation image and a character image, and converting the image into an image? 11 mixed image discriminating means for generating separate signals, area specifying means for generating an area specifying signal for specifying an area to be subjected to contour processing or hatching processing, and an instruction signal for instructing the priority order of image processing results. Instruction input means and image discrimination signal. It is characterized by comprising a selection means that receives the area designation signal and the instruction signal and selectively passes the processing result of character image processing, contour processing, halftone processing, or gradation image processing. .

(Function) In the image processing apparatus of the present invention, character image processing and outline processing are performed on image signals obtained from a document. Shading processing and gradation image processing are performed. These image processing results are mixed image discrimination signals and instruction signals. It is selected by the area designation signal and output to the outside.

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

FIG. 1 is a configuration diagram showing the electrical configuration of an embodiment of the present invention.

First, the overall general operation of the embodiment shown in FIG. 1 will be explained.

An optical image obtained by optically scanning a subject (original) 1 is guided to an image reading section 3 via a lens system 2 and converted into an electrical signal (image signal). This image signal is converted by the A/D converter 4 into a digital image signal of predetermined bits. At the same time, the shading correction section 5 performs shading correction. Then, the effective area extraction section 6 selects only digital image signals corresponding to a necessary area (for example, B4 size, etc.). This digital image signal is subjected to resolution correction by MTF correction in a resolution correction section 7. Thereafter, the digital image signal is supplied to the image processing section 8, and different image processing (multi-value processing of two or more values) is performed for the character image and the gradation image. This image processing and image discrimination will be described later. The multivalued digital image signal is
The image is supplied to a printer 10 such as an electrophotographic printer, and an image is formed. Note that the output selection section 9 provided in the operation section of the device
Character strokes can be created by operating the . It is also possible to manually select image processing for one of the gradation images.

Further, a digitizer 11 constituting area specifying means is connected to the apparatus, and thereby specifies the area in which each process is to be executed.

Next, the operation of the image processing section 8 will be mainly explained.

Now, in the present invention, the image processing section 8 performs multivalue processing according to the input image. In the present invention, pixel-by-pixel discrimination is employed as image discrimination processing performed during multi-value processing.

The digital image signal after MTF correction in the resolution correction section 7 is first supplied to a character image processing section 20 which functions as a multi-value processing means, and is converted into an image peculiar to character images such that characters etc. are clearly reproduced. Processing is performed. Further, the halftone processing section 21 performs image processing that emphasizes halftones (gradation characteristics).

Since it is sufficient to convert character images to 21ii, the digital image signal is binarized using a fixed threshold value.

Note that for character images, contour processing in which only the outline of the character is extracted and only the outline (white) is output, and halftone processing in which a halftone pattern is superimposed on the character and output are also performed. Reference numeral 22 denotes a contour processing section that performs contour processing on the image signal that has undergone character image processing, and 23 represents a shading processing section that performs shading processing on the image signal that has undergone character image processing.

The outline processing and shading processing need only be performed on the character area, and do not need to be performed on the photographic area.

So, depending on the discrimination result, is it a character area? ．． It is sufficient to process only the +J cut area. Therefore, in this embodiment, this processing is executed after the processing by the character image processing section 20.

Further, the outline processing and the shading processing may not need to be performed on the entire character, but only on a desired part of the characters. In such a case, the digitizer 11 specifies the area. Then, only the characters within the area designated by the digitizer 11, the processing content selected by the output selection section 9 among the halftone processing or outline processing is applied to the image selector 25.
pass through. Of course, if the area is not designated by the digitizer 11, the processing contents according to the determination results and selection results of the output selection section 9 and the mixed image determination section 24 are passed through the image selector 25.

The image signal is further supplied to a mixed image discrimination section 24, and the image discrimination output obtained thereby (in this example, 1-bit data) is supplied to an image selector 25 as its control signal. Therefore, the above-mentioned character images and gradation images are selected according to the image content by this image discrimination output.

That is, when it is determined that it is a character image, the image discrimination output becomes "0" and the output of the character image processing circuit 20 is selected, and when it is determined that it is a gradation image, the image discrimination output becomes "1". Therefore, the output of the halftone processing circuit 21 is selected.

Here, reference numeral 9 indicates an output selection section provided in the operation section of the digital copying apparatus.

The output selection unit 9 has three types of selection switches: character mode, gradation mode, and mixed mode, and when character mode or gradation mode is selected, the output result from the mixed image discrimination unit 24 is Regardless, the output to the printer 10 is only in the fixed selection mode.

On the other hand, when the mixed mode is selected, one of the gradation image processing data and text processing data is automatically selected for each pixel by the image discrimination output from the above-mentioned mixed image discrimination section 24. Output.

Therefore, even when character images and gradation images coexist on the same document, output quality can be maintained by selecting the mixed mode.

The output selection section 9 can also select whether to perform outline processing and shading processing on characters.

That is, as a result of this selection, the image selector 25 selects one of character double processing (A), character image outline processing (B), and character image shading processing (C).

For example, if you select mixed mode and text outline processing,
Based on the determination result, the output (B) of the contour processing section 22 and the output (D) of the halftone processing section 21 are selected by the image selector 25 and output.

Further, in this case, if an area is designated by the digitizer 11, the outline processing result will be selected only for the character portion within the designated area.

Here, the mixed image discrimination section 24 will be explained with reference to FIG. 2 and subsequent figures. The mixed image discriminating section 24 described above is composed of first and second discriminating means 30 and 40.

That is, the first discrimination means 30 is a means for roughly discriminating an input image into a character image and a gradation image to obtain a first image discrimination output. On the other hand, the second discrimination means 40 to which the output for each first image I'll is supplied re-discriminates the image discrimination output of the gradation image included in the first image discrimination output that specifically corresponds to the character image. This is a means for obtaining a second image discrimination output related to a character image and a gradation image.

First, the first determining means 30 will be explained with reference to FIG.

The first determining means 30 uses a low-pass filter 31 for the pixel of interest and a low-pass output for the pixel of interest to a reference value RE.
It consists of a comparator 32 that compares with F, and a level determination circuit 33 that further determines the level of the comparison output regarding the pixel of interest.

The purpose of the low-pass filter 31 is to reduce the high frequency components of the input image signal, thereby making it possible to roughly distinguish between character images and gradation images.

When the high frequency components of the input image information are reduced, when the input image is a photographic image or a halftone line drawing, the density of the pixel of interest is dispersed to each point, so that every pixel exhibits a certain density Na or higher.

As an example of a halftone image, as shown in FIG. 3(A), the difference in density between dots and non-dots clearly appears.

When this is passed through a low-pass filter 31 and the high frequency is reduced to some extent, a signal (approximating a sine wave) corresponding to the repeating pitch of the mesh line drawing is generated at the DC level Na' above a certain level Na, as shown in FIG. 3(B). signal) are superimposed.

On the other hand, even if characters, line drawings, etc. are passed through the low-pass filter 31, since there are many background parts, a region with a density lower than that of Na remains.

Therefore, the comparator 32 determines the density of the pixel of interest using a reference value REF having a predetermined level that is less than or equal to Na.

This reference value REF needs to be set to a value that is considerably lower than the threshold value used when binarizing character strokes and slightly higher than the background level. This is because if it is too low, it becomes indistinguishable from the background (ground) texture level, and if it is too high, when the halftone line drawing is filtered and dispersed, there will be some that are lower than this reference value REF, resulting in erroneous classification.

Therefore, it is preferable to set the reference value REF after detecting the background level by introducing a so-called automatic density adjustment function that determines the background level from the preliminary reading of the original.

In the case of photographs and halftone drawings, the comparison output is "1",
In the case of character drawings and line drawings, it is rOJ.

Next, in the level determination circuit 33, the comparison output obtained from the comparator 32 is re-determined.

In this re-judgment process, a check window of a certain size is set up around the pixel of interest, and only when all the pixels existing within that window are equal to or higher than the reference value REF mentioned above, does the pixel of interest change its gradation level. As a picture, "I'l1 is cut off."

As a result of this processing, in the case of a halftone image, the density is widely dispersed and it is determined as a gradation image, so in this case, the halftone processing circuit 21 is selected.

On the other hand, even if character images are dispersed such as the background, a value lower than the base value remains, and since a part of the check window is applied to this portion, the pixel of interest is determined to be a character image as expected.

FIG. 4 shows an example of the low-pass filter 31, and in this example, a 3×3 convolution filter configured in a cross shape is used.

The convolution filter used as a low-pass filter is a process that returns the pixel of interest and its surrounding pixels by applying a certain weight C to the original pixel of interest. In this example, the pixel of interest and the pixels above, below, left, and right are It is simply added, divided by 5, and averaged.

Therefore, the pixel of interest a. The filtered output a'-th is a'-(1/5)*Σ(c 111 a , 1).

Here, c1 is 1 only for the pixel of interest and four pixels on the upper, lower, left, and right sides, and is 0 for the other diagonal components.

Here, the reason why a cross-shaped type with a weight of 1 is adopted as the low-pass filter 31 is as follows.

First, regarding the size of the filter, the larger the filter size, the more dispersed the results will be, making it possible to handle even coarse dots. However, since the overall density level at that time gradually decreases, it becomes difficult to determine the threshold value, and misjudgment becomes more likely to occur. Additionally, as the filter size increases, hardware constraints also increase.

For this reason, in this example, the size is set to 3×3 in consideration of hardware constraints.

The reason why the filter shape is made into a cross shape will be explained with reference to FIG.

In this figure, the center portion is a mesh dot, and the diagonal lines are a mesh pattern. Also, a collection of small dots is the minimum unit of reading.

Generally, in the case of halftone drawings, halftone lines are often arranged in a 45 degree direction. In the case of a cross shape, the result of filtering spreads nicely into a diamond shape along the mesh structure as shown in the figure. Therefore, no matter which pixel the window is placed on, there is no extremely low part and it is determined as a halftone image as expected.

On the other hand, if a filter that disperses in an X-shape (the 6th
If Figure (A)) is used, as shown in Figure 6(B), when the mesh lines are fine, the density in a certain area will be averaged to the dots of the adjacent mesh line, and the density will be considerably high. On the other hand, the filter action does not reach the valleys of the X-shape, so the density in these valleys remains low.

Therefore, if a part of the window falls over this valley, this part falls below the reference value, and the pixel of interest is incorrectly determined to be not a gradation image. This can occur regardless of the shape of the window.

From the above, it can be seen that a cross shape is appropriate as the shape of the filter.

Further, in order to distribute the dots evenly, it is desirable that the coefficients of each filter are all 1 (ie, equal).

It is expected that this low-pass filter 31 will effectively disperse even fairly coarse halftone lines.

Please note that the meshwork is too coarse or the dots are extremely small (
In other words, if the image is thin (thin), there remains a possibility that it will be misidentified as a character part that is within the range of the filter.

Since the dots that can cause such misjudgment are always independent minute dots, if necessary, an independent dot detection circuit can be provided as post-processing after the low-pass filter 31, thereby further improving the halftone image detection ability.

This post-processing involves, for example, checking the surrounding pixels of a pixel that has been determined to be black, and if they are all white, determining that they are independent dots,
Means such as halftone processing can be adopted.

The filter mentioned here has a 3 x 3 cross shape in order to maximize the effect with the minimum amount of hardware, but it must have enough resolving power to resolve the difference between the density after dispersion by the filter and the background density. For example, a filter with a larger structure can also be used.

In that case, halftone dots can be smoothed more efficiently than when the size is 3×3. In this case, in order to achieve more uniform smoothing, a cross-shaped filter is used that extends from the Shome pixel by n pixels (n is an integer of 1 or more) in the vertical and horizontal directions, and the total number of filters is 4n+
It is preferable to use a filter that returns the average value of one pixel to the pixel of interest.

Here, a specific example of the low-pass filter 31 will be explained with reference to FIG.

The digital image signal is supplied to cascade-connected latch circuits 31a and 3lb for IH (H indicates a horizontal scanning period), and the original digital image signal and the IH and 2H delayed digital image signal are supplied to amplifiers 31c, 31d, and 31e. The signals are simultaneously supplied to the 3-line memory 31f via the 3-line memory 31f.

Among the digital image signals for 3 lines obtained from the 3-line memory 31f, the digital image signal of the n-1 line is processed by a pair of latch circuits 31g with a delay time τ of 1 pixel.
, 31h and then supplied to the adder 31n.

Similarly, the n-line digital image signal passes through three latch circuits 31t, 31j, 31k, and then reaches the adder 3.
1n. Then, the digital image signal obtained on the n+1 line is transmitted through a pair of latches 31ρ1 31
The signal is supplied to the adder 31n via the input signal m.

In this way, by using a plurality of latch circuits, all the digital image signals of each pixel shown in FIG. 6 can be obtained simultaneously. The fully added digital image signals are reduced to 175 by the coefficient unit 31o at the subsequent stage. Coefficient unit 3
As 1o, a ROM or the like can be used.

Next, the level determination circuit 33 will be explained. As the level determination circuit 33, a cross-shaped 7×7 checking window is used as shown in FIG. This window extends by 3 pixels in the top, bottom, left, and right directions, and if all of the i112 pixels including the pixel of interest a1 are larger than the above-mentioned reference value REF, the pixel of interest is determined to be a gradation image.

The reason why the window size is set to 7×7 will be explained with reference to FIG.

Generally, characters and line drawings often run parallel to the paper surface (that is, parallel to main scanning or sub-scanning). At this time, if the outline of the boundary is not clearly processed as a character part, it will become blurred and difficult to see if it is subjected to gradation processing, for example.

As shown in the figure, if the area starts from the n-th pixel,
Due to the action of the low-pass filter 31, the density is dispersed up to n-1 pixels. If the window size is 7.times.7, and the arm of the window is up to n-2 pixels, there will be a portion lower than the reference value, and the pixel of interest will be determined to be a character image.

In other words, up to n+1 pixel rows are determined to be character parts. That is, in a boundary portion (outline portion), up to two pixels inside the boundary portion are reliably determined to be character portions.

Due to the effect of this window, a clear image can be obtained without blurring the outline at the border.

As is clear from the description of FIG. 9, the window size used in the level determination circuit 33 is preferably larger than the window size of the low-pass filter 31. When the size of the low-pass filter 31 is assumed to extend by n pixels in the vertical and horizontal directions, the window for level determination has a structure in which an integer m is larger than n and extends by m pixels in the upper, lower, left, and right directions.

FIG. 10 shows a specific example of the structure of the level determination circuit 33.

Since the level determination circuit 33 also has a window structure, it is basically the same as the filter structure shown in FIG. However, since the input to the level determination circuit 33 is the determination output of the low-pass filter 31, it is a 1-bit signal indicating whether it is a character image or a gradation image.

However, the number of windows used in the level judgment circuit 33 is 7.
Since the size is 7×7, it is necessary to delay by 7 lines and 7 pixels. Therefore, the number of latch circuits used for IH delay and one pixel delay increases accordingly.

33a to 33f are latch circuits for IH delay;
g is a memory for 7 lines. and 33h to 33j
, 33r to 33t are latch circuits for delaying four pixels.

Although these latch circuits are composed of four latch circuits each connected in cascade, they are shown as one latch circuit for convenience in the drawings. 33k to 33Q indicate latch circuits for one pixel.

These seven lines of digital image signals are each delayed by a predetermined pixel by a plurality of latch circuits, and
By deriving the output from each predetermined position, digital image signals of each pixel corresponding to the window shown in FIG. 8 can be obtained simultaneously in time.

Therefore, when the corresponding digital image signals are ANDed in the AND circuit 33u, an image discrimination output in which the pixel of interest becomes "1" is obtained at the output terminal only when the density level of all the pixels is equal to or higher than the reference value.

In this way, in the first discriminating means 30, the character stroke group,
A first image discrimination output corresponding to the photographic image and the halftone image group is obtained.

By the way, under certain conditions, a character image may be recognized as a character image or as a gradation image.

For example, as shown in FIG. 11(A), when the input image is the character image "Sono", if this is passed through the low-pass filter 31, it will be output as shown in FIG. 11(B). In other words, when a character becomes smaller than a certain degree, the inside of the character may become considerably blurred due to the action of the low-pass filter.

At this time, if there is a pixel of interest inside the character, and all of the pixels in its vicinity exceed the reference density due to this filter effect, the pixel of interest will be processed as a pixel of a gradation image. As a result, even if an image is recognized as a character image, as shown in FIG. 12, for example, there are parts inside the character that are erroneously determined to be gradation images.

In this way, the inside of a small character may be misidentified as a gradation image, and as a result, the quality of the character may deteriorate significantly.

Here, in a real halftone drawing or photographic drawing, the part that is judged to be a gradation drawing occupies a certain area, so it is actually not possible for such a gradation drawing to appear in a certain area. There isn't. In other words, when a result for each ill is obtained in which gradation images are scattered in a very small area, there are actually no gradation images for each small area, so it is difficult to distinguish between them. It can be determined that the result is a misclassification.

Therefore, as shown in FIG. 2, a second determining means 40 is provided. This second discrimination means 40 re-identifies the gradation picture included in the above-mentioned character picture as a character picture.

In order to re-recognize a gradation image included in a character image as a character image, it is sufficient to check the gradation image discrimination area and determine whether it occupies a certain size.

To do this, it is sufficient to memorize the image data of a certain area for the pixel of interest, and calculate the table or area of the closed area of the gradation image discrimination part.

In order to perform this discrimination process, in principle it is necessary to store image data in both the main scanning direction and the sub-scanning direction. There is.

As a result, it is sufficient that the memory has a maximum capacity of one bit indicating whether the image is a character image or a gradation image and one line of memory. Furthermore, experiments have revealed that the correction effect is sufficient even with only main scanning.

FIG. 13 shows a second discriminating means 40 that has achieved such processing.
An example is shown below.

The first image discrimination output output from the first discrimination means 30 is supplied to the input terminal.

As mentioned above, the first image discrimination output is "1" when it is a gradation image.
The output is "0" when it is a character stroke.

The length of the gradation image of the first image discrimination output is counted by a counter 40a. Therefore, the counter 40a is set at "1" and reset at "0", and is counted up in synchronization with the dot clock CK. The counter output a is compared in a comparator 40b with a reference value b associated with the reference length L (FIG. 14(A)).

L is preferably about 2ffil1.

The pulse comparison output exceeding the reference value b becomes "1", and at this time a single control pulse p is output from the pulse generating means 40d (FIG. 14(B)).

On the other hand, the dot clock CK is also supplied to the address counter 40e to form a horizontal address, and the address data is latched in the latch circuit 40f.

The latch pulse is formed based on the rising edge of the first image discrimination output.

40g indicates this rising edge detection circuit.

One of the address data of the address counter 40e and the rising address data latched by the latch circuit 40f is selected by the address selector 40h by the control pulse p. In this example, it is assumed that the latched address data is selected when the control pulse p is obtained. Address data selected by address selector 40h is supplied to first line memory 40i.

A control pulse p is supplied to the first line memory 40i as a write enable pulse. Therefore, when the control pulse p is obtained, data "1" at a predetermined level is written at the latched address in synchronization with the rising point 0 of the first image discrimination output.

On the other hand, in the second line memory 40j, the first image discrimination output is written to the address obtained from the address counter 40e in synchronization with the dot clock CK (see FIG.
C)).

Data is read from the line memories 40i and 40j as shown in FIG. That is, in the next first line, data is simultaneously read from the line memories 40i and 40j (FIGS. 15(A) to 15(C)).

The output of the line memory 40i passes through a NAND circuit 40k
It is supplied to the set terminal S of the S-type flip-flop 40n. Similarly, each output of the line memories 40i and 40j is supplied to an input negation type NAND circuit 401l, and the output is further passed through a NAND circuit 40m to a flip-flop 401l.
0n reset terminal R.

As a result, a second image discrimination output as shown in FIG. 15(D) is obtained at the output terminal 400.

When the second discrimination means 40 is configured in this way, as shown in FIG. 11, even when both gradations are recognized in the first image discrimination output, the length in the main scanning direction is a predetermined length L. Only when the above is the case, is the image showing the gradation image as the final image discrimination output? 1 separate output rlJ can be set up.

Therefore, if the length is less than the predetermined length L, even if it is determined to be a gradation image, it will eventually be re-identified as a character image.

As a result, input documents can be identified and processed with precision and efficiency not previously possible. Furthermore, halftone drawings, which have been considered difficult in the past, can now be distinguished as gradation drawings by using the low-pass filter 31 and window processing for level determination.

In addition, character information with low contrast, such as handwritten characters, can be clearly determined to be a character part by comparing it with the background texture information, and there will be no erroneous I'll classification within the character, so input images can be correctly identified. Can be processed.

In addition, in the above example, only the length of the gradation image part was evaluated and determined, but similarly, a correction circuit that incorrectly judges an extremely short character part to be classified as ill is further provided, and the 111-part results can be calculated. You may modify it to make it closer to reality.

Based on the final discrimination result obtained in this way, in the case of a character image, the viscous that has passed through the character image processing unit 20, or the contour processing unit 22, and the shading processing unit 23 is selected, and in the case of a gradation image, the result is selected. selects the result passed through the halftone processing section 21. An image output can be obtained by sending the result to a printer.

Next, an example of a mechanism of a digital copying apparatus to which the image processing apparatus of this embodiment is applied will be described with reference to FIG. 16.

When you turn on the copy button on the device, the document reading section A
is driven. First, the original 1 on the original table 111 is optically scanned by the optical system.

The optical system moves integrally with a carriage 114 provided with a light source 115 and a reflecting mirror 116, and a mirror carriage 114, and directs light reflected from the document 1 by the light source 115 to one mirror 119 of a V mirror to be described later. mirror 11
7 and the V mirror 119 moved in the same direction at a speed of 172 of the speed of the mirror 117, +f't5 at IIQ'
3E will be given. Calimeter 114 and V mirror 119,1
19' is driven by a stepping motor 120 and runs on a sliding rail (not shown). As the light source 115, a halogen lamp or a commercially available warm white fluorescent lamp can be used.

A white marker plate 110 is provided on the upper surface side of the left end of the document table 111 . This is done by scanning the standard white plate 110,
This is to normalize the image signal to the reference white signal.

An optical image obtained by irradiating the original 1 with the light source 115 is guided to the optical information conversion unit 100 via the reflecting mirror 117 and the mirrors 119 and 119'. This optical information conversion unit 100 is composed of a lens 100a and a CCD 101 that functions as an image reading means.

The image signal photoelectrically converted by the CCDIOI is outputted to the writing section B after being subjected to the various signal processing described above in the signal processing system.

The writing section B has a deflector 150. As the deflector 150, in addition to a galpano mirror or a rotating polygon mirror, a deflector made of an optical deflector using a crystal plate or the like may be used. The laser beam modulated by the image signal passes through this deflector 15.
Deflection scanning is performed by 0.

The modulated beam scans (main scans) over a photosensitive drum (image forming body) 160 that is uniformly charged by a charger 121 . An electrostatic latent image corresponding to the image signal is formed on the drum 160 by this main scanning and the sub-scanning by the rotation of the drum 160.

The electrostatic latent image is developed by a developing device 123 containing black toner.

On the other hand, the recording paper fed from the paper feeder 141 via the feed roll 142 and the timing roll 143 is conveyed to the lower side of the drum 160 in a state in which the timing is synchronized with the rotation of the drum 160. Black toner is transferred onto the recording paper by the transfer pole 130 to which a high voltage is applied, and then separated by the separation pole 131.

The separated recording paper is conveyed to the fixing device 132, where it is not fixed and then discharged.

The drum 160 after the transfer is cleaned by the cleaning device 126 and is prepared for the next image forming process. here,
127 is a cleaning blade, and 128 and 129 are metal rolls to which a predetermined DC voltage is applied.

In the above description, the image processing apparatus of this embodiment is applied to a digital copying machine, but the present invention is not limited to this. That is, it goes without saying that the present invention can be applied to various devices that process text and gradation images.

(Effects of the Invention) As described in detail above, in the present invention, a mixed image in which a character image (including a character image with shading) and a gradation image are mixed is classified as full based on the image discrimination result, and the character In addition to selecting different processing for text and gradation pictures, it is now possible to perform outline processing and shading processing only on specified areas of character pictures. That is, the contour processing and the shading processing are performed and selectively output only in the desired area when the image is disconnected from the Bunyu painting.

Therefore, it is possible to realize an image processing apparatus that can perform high-quality single image processing suitable for each image, and can perform outline processing and shading processing only on character image areas.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the electrical groove structure of an embodiment of the present invention;
FIG. 2 is a block diagram showing the configuration of the discrimination circuit, FIG. 3 is an explanatory diagram for explaining the operation of the low-pass filter, FIG. 4 is a diagram showing the horizontal configuration of the low-pass filter, and FIGS. Figure 6 is an explanatory diagram explaining the characteristics of the low-pass filter, Figure 7 is a configuration diagram showing the electrical configuration of the low-pass filter, Figure 8 is a diagram showing the configuration of the level judgment circuit, and Figure 9 is a diagram showing the level determination circuit. An explanatory diagram explaining the characteristics of the iIl constant circuit, Fig. 10 is a configuration diagram showing the electrical configuration of the level judgment circuit, Fig. 11 is an explanatory diagram of the filter effect, and Fig. 12 explains the result of image discrimination. FIG. 13 is a diagram showing the configuration of the second discriminating means, FIGS. 14 and 15 are explanatory diagrams of the operation of the second discriminating means, and FIG. 16 is a diagram to which the image processing apparatus of this embodiment is applied. 1 is a configuration diagram showing the mechanical configuration of a copying machine. 1... Subject 2... Lens 3... Image reading section 4... A/D converter 5... Shading correction section

Claims (1)

[Scope of Claims] Character image processing means for converting an image signal obtained by scanning a document into a multi-valued signal of two or more values through character image processing; a contour processing means for performing contour processing on a portion; a shading processing means for receiving the output of the character image processing means and performing shading processing on the character portion of the image signal; gradation image processing means for converting the image into a multivalued signal of two or more values through image processing; mixed image discrimination means for discriminating the image into gradation image and character image and generating an image discrimination signal; and contour processing or shading. an area specifying means for generating an area specifying signal for specifying a region to be processed; an instruction input means for generating an instruction signal for instructing the priority of image processing results; receiving an image discrimination signal, an area specifying signal and an instruction signal; 1. An image processing apparatus comprising: a selection means for selectively passing a processing result of character image processing, outline processing, halftone processing, or gradation image processing.