JP3337723B2 - Image processing apparatus and image processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, for example, an image processing apparatus for processing black characters in an image.

[0002]

2. Description of the Related Art In recent years, color image data obtained by digitally processing color image data and outputting it to a color print to obtain a color image, and color image data obtained by color-separating a color original and electrically reading the image are obtained. There is a remarkable development of a color printing system such as a so-called digital color copying machine that performs color image copying by printing out on paper.

[0003] Further, with the widespread use of these, the demand for the printing quality of color images has been increasing. In particular, there has been a growing demand for higher printing of black characters and black fine lines and sharper printing. That is, when a black document is subjected to color separation, signals of yellow, magenta, cyan, and black are generated as signals for reproducing black, but when printed as it is based on the obtained signals, each color is reproduced by superimposing four colors. Therefore, a slight shift between colors causes color bleeding on a thin black line, and black is not seen as black or blurred, resulting in a marked decrease in print quality. On the other hand, black characters in the image, utilizing the features of thin lines, for example, the edge component is determined by determining the chromatic color or achromatic color of the image to detect the black character, to determine whether the image is in the image or non-image, to determine the There has been proposed a method of making a single black color in response thereto.

[0004]

However, in the above conventional example, the black isolated points in the image are faithfully reproduced or the thin lines or the achromatic outline portions in the image are excessively pursued in pursuit of faithful reproducibility. Also, black text processing was applied, and some originals were remarkably noticeable, which hindered high image quality.

[0005] The present invention has been made in view of the shortcomings of the conventional example described above, it is an object in the image
UCR processing for the black line drawing part according to the background degree of the image
Image that can be faithfully reproduced by applying
An object of the present invention is to provide an image processing apparatus and an image processing method .

[0006]

Means for Solving the Problems To achieve the above object,
In the image processing apparatus according to the present invention,
Input means for inputting a plurality of color component signals, and the input means
Based on the plurality of color component signals input by
Detecting means for detecting a black line drawing part in an image;
Based on a plurality of input color component signals
Determination means for determining the background degree of the
The UCR amount is determined according to the determined background degree,
A plurality of color component signals representing the black line drawing part detected by the step
On the other hand, UCR processing is performed using the determined UCR amount.
UCR processing means for applying, the UCR processing means,
If the background degree determined by the determination means is low,
The UCR amount is determined to be larger than when the background degree is high.
It is characterized by the following. In this case, the determination unit determines that the image
Calculate the average brightness and the degree of regularity of the
Then, it is preferable to determine the background degree of the image.
Further, the determination means may determine a history of luminance data of the image.
Gram, and based on the histogram,
It is also preferable to determine the background degree.

[0007] To achieve the above object, an image according to the present invention is provided.
In the image processing method, a plurality of color component signals representing an image are
An input step of inputting, and the
A black line drawing portion in the image is detected based on the number of color component signals.
A detecting step to be output and a plurality of input steps in the inputting step.
The background degree of the image based on the color component signal of
A determination step, and responding to the background degree determined in the determination step.
The UCR amount was determined in the same manner,
For a plurality of color component signals representing a black line drawing portion, the determined
UCR processing step of performing UCR processing using the determined UCR amount
And the UCR processing step includes:
If the determined background level is low, the background level is high.
It is characterized in that the UCR amount is determined to be larger than in the case.

[0008]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. First Embodiment <Overall Configuration> FIG. 2 is a side sectional view showing the internal configuration of a color copying machine according to a first embodiment of the present invention. In FIG. 1, reference numeral 201 denotes a platen glass on which a document 202 to be read is placed. The original 202 is illuminated by the illumination 203, and passes through mirrors 204, 205, and 206.
An image is projected on the CCD 208 by the optical system 207.
Here, the CCD 208 has R (red), B (blue),
It is composed of three G (green) CCD line sensors. Further, a mirror 204,
The first mirror unit 210 including the illumination 203 is driven at a speed V, and the second mirror unit 211 including the mirrors 205 and 206 is driven at a speed of 1/2 V, so that the entire surface of the document 202 is scanned. Reference numeral 212 denotes an image processing circuit which processes the read image information as an electric signal and outputs it as a print signal. 213, 214, 21
Reference numerals 5 and 216 denote semiconductor lasers.
The laser beams driven by the output signals from the semiconductor lasers 2 and emitted by the respective semiconductor lasers are transferred by the polygon mirrors 217, 218, 219, 220 for the respective prints to the photosensitive drums 225, 226, 227,
228, forming a latent image. 221, 22
2, 223 and 224 are developing units for developing a latent image with black (Bk), yellow (Y), cyan (C), and magenta (M) toners, respectively. One of the paper cassettes 229, 230, 231 and the manual feed tray 232 is selected, and the fed paper is suctioned onto the transfer belt 234 via the registration roller 233 and transported. Synchronized with the paper feed timing, the images of the respective colors are developed on the photosensitive drums 228, 227, 226, and 225 in advance, and are transferred to the paper.

The paper on which the toner of each color has been transferred is separated / separated.
The sheet is conveyed and fixed, and is discharged onto a discharge tray 236.
Here, in FIG.
0, the lower part is the printer unit 113. <Configuration of Reader Unit 100> FIG. 1 is a block diagram showing a circuit configuration of the reader unit 100 according to the first embodiment. In the figure, 101 is a CCD line sensor of the CCD 208, 102 is an analog processing circuit, 103 is an A / D converter, 104 is a shading correction circuit, 105 is an input masking circuit, a density conversion circuit, and 110 is UCR (under color removal). Circuit, 111 is a gamma correction circuit, 112 is an edge enhancement circuit, 113 is a printer unit, 124 is a memory, 125 is a companding unit, and 126 is a black character determination unit. The companding unit 125 includes an encoder unit 107, a memory 108, and a decoder unit 109. The black character determination unit 126 includes a black removal circuit 114, an edge detection circuit 115, and a determination circuit 1 again.
16, isolated point removal processing circuit 117, smoothing processing circuit 11
8, a background determination circuit 119, determination circuits 120 and 121, a selector 122, and an AND gate 123.

Next, the operation of the above configuration will be described. In the color image reading unit, while scanning the original, the reflected light from the original is color-separated by the CCD line sensor 101 for reading the color image and is input. The electrical signals corresponding to the R (red), G (green), and B (blue) color components of the color original are sampled and held by the analog processing circuit 102 for each color, and subjected to black correction, white correction, color balance, and other processing. After that, the image data is digitized by the A / D converter 103, the shading characteristics of the image reading unit are corrected by the shading correction circuit 104, and the input masking circuit 105 converts the signal into an NTSC RGB signal. Color data C (cyan), M (magenta), and Y (yellow) corresponding to the color materials are adjusted for the corrected RGB signals by the next density conversion circuit 106 in accordance with the LOG characteristics.
Is converted to The converted C, M, and Y data are compression-coded by the encoder unit 107, and are stored in the memory 108.
And expanded by the decoder unit 109.

After that, the signal is input to the UCR circuit 110 and K
The value of (black) is calculated as in the following equation (1).
That is, BK = Min (C, M, Y) (1). UCR is performed on the calculated data for each of the C, M, and Y color data. The UCR amount is determined by reference data of an LUT (look-up table), and FIG. 3 shows characteristics relating to the UCR amount. In the quantities shown in FIG.
UCR starts from the input Bk amount of about 40%,
It shows the characteristic that UCR up to 50% is performed.
Each color data thus color corrected is corrected by the γ correction circuit 111 in accordance with each printing in the color printer unit,
Edge enhancement and smoothing are performed through an edge enhancement circuit 112 which is a filter, and sent to a printer unit 113.

Next, detection of black characters / black line drawings will be described. FIG. 4 is a block diagram showing the configuration of the black removal circuit 114, and FIG. 5 is a diagram showing an image processing image by the black removal circuit 114. In FIG. 4, 41 is a maximum value detection unit, 42 is a minimum value detection unit, 43 is a subtractor, and 44 is an LUT.
(Look-up table) and 45 indicate AND circuits, respectively.

First, as described above, in each of the color separation signals R, G, and B subjected to shading correction, black is detected and removed by a black removal circuit 114 with a relatively loose threshold value.
Here, as shown in FIG. 5, the black “mountain” is removed and the data is FF (luminance). Next, in order to remove dust (isolated points) in the image by the isolated point removal processing circuit 117, a process of taking the median value in an arbitrary pixel block and replacing the median value with the pixel of interest is performed. Thereafter, the data is smoothed by the smoothing processing circuit 118 to make it easier to read the tendency of the underlying pattern.

FIG. 6 is a block diagram showing the structure of the background judgment circuit 119. In the figure, reference numeral 601 denotes an F / F (flip-flop) group, and 601-1 to 601-N indicate F / F. 602 and 603 are arithmetic units, 604 is LU
T is shown. Here, a signal for one arbitrary color of RGB is shown. Note that a well-known ND signal may be used to reduce the circuit scale. Incidentally, ND = (R + 2G + B) / 4 (2) In order to see the underlying pattern, the averaged value of the N pixels in the main scanning direction (hereinafter referred to as “DC component”) and | F (M
AX) -F (MIN) | (difference between the positions of MAX and MIN,
That is, the period) (hereinafter referred to as “AC component”) is
Check at 02,603. Normally, a regular pattern such as a halftone dot is less than 2 mm or more, so that it is appropriate to use 32 pixels at 400 dpi, that is, N = 32. After that, LUT60
In 4, the background degree is defined by the average luminance and the regularity, and processed by the UCR circuit 110. For example, as a processing method, D
If the C component is high and the AC component is small, the background degree is low (that is, the background is close to a uniform white background), so the UCR amount is increased. If the DC component is low and the AC component is high, the background degree becomes high (that is, in an image where the background is not uniform), so that the UCR amount is reduced. Here, the AC component, the DC component, and the background degree are each represented by multiple values.

Returning to FIG. 1, the edge detection circuit 115 detects an edge component and detects characters and fine lines in a flat screen or a map. The edge detection circuit 115 includes:
The NC signal obtained from the RGB signal is input. FIG. 7 is a block diagram showing the configuration of the edge detection circuit 115.
In the figure, reference numerals 70 to 73 denote FIFOs (first-in first-out circuits), 74 denotes a Laplacian, and 75 denotes an absolute value and noise removal circuit.

Next, the operation of the above configuration will be described. The input ND signal is expanded to five lines by FIFOs 70 to 73 and applied to a well-known Laplacian filter 74. Next, in the absolute value and noise removal circuit 75,
Those whose edge amount is equal to or less than the absolute value a are removed, and those whose edge amount is equal to or more than a are output as “1”.

FIG. 8 is a time chart showing the above operation. As shown, the output of the Laplacian 74 is (ii) and the output of the absolute value and noise elimination circuit 75 is (iii) for the original image (i). Thereafter, as shown in FIG. 1, the edge processing in the image or in the non-image is set independently by the determination circuits 120 and 121. FIG. 9 is a block diagram showing the configuration of the determination circuit 120, and FIG. 10 is a block diagram showing the configuration of the determination circuit 121. FIG.
In FIG. 10, 91-1 and 91-2 are FIFO, 92-1
Is a delay circuit, 93 and 95 are OR gates, 94-1.94
-2, 97-1, 97-2 are F / F, 96, 98 are AN
D gates are shown.

According to the above configuration, for example, the signal after edge detection is spread over a 3 × 3 screen, and if there is at least one edge in the pixel of interest, the edge is emphasized. If there is no component, the circuit removes the edge. This removes noise from the edges in the image,
Edges in non-images are emphasized. And the selector 12
2 output. Here, the select signal of the selector 122 is switched according to the average luminance of the arithmetic unit 602 in FIG.

FIG. 11 is a block diagram showing the configuration of the saturation determination circuit 116. In the figure, reference numeral 144 denotes a maximum value detection unit, 145 denotes a minimum value detection unit, 146 denotes a subtractor, and 147 denotes an LUT. Next, the operation of the above configuration will be described. For RGB, the maximum value MAX (R, G,
B) 548 and the minimum value MIN (R, G, B) 549 are respectively detected, the difference ΔC is calculated by the subtractor 46, and the next LUT 47 performs data conversion according to the characteristics shown in FIG. A degree signal Cr is generated.

FIG. 12 is a diagram showing characteristics of the saturation signal Cr. In FIG. 12, as ΔC is closer to “0”, the saturation is lower (closer to achromatic color), and as ΔC is larger, the degree of chromatic color is closer to “0”.
It becomes 0. In addition, the degree of change is shown to follow the figure. Therefore, the output of the AND gate 123 becomes "1" only when black is detected and an edge is detected. Thereafter, the data is processed by the UCR circuit 110 via the memory 124. The determination result obtained here enters the encoder unit 107 at the same time, and the compression ratio can be varied according to the degree of the edge based on the background degree. Furthermore, by specifying an area before copying with an undesignated digitizer, and performing character processing only on the specified area or only on the outside of the specified area, it is possible to obtain a higher quality image.

As described above, according to the first embodiment, the character in the white background is sharpened by quantifying the background degree and performing the process of changing the UCR amount according to the background.
By applying a weak UCR to the black thin line detected in the image, the original can be faithfully reproduced, and thus, high image quality can be maintained. (Second Embodiment) In the first embodiment, black is removed and then isolated points are removed and smoothing is performed in order to determine the background degree. However, in this embodiment, black removal is performed. After doing
A histogram of data is taken in an arbitrary block to quantify the background degree.

FIG. 13 shows a low background degree according to the second embodiment.
It is a figure which shows an example of a middle and large. When the frequency of high-luminance data is high, the background degree is low and the UCR amount is increased. If the frequency of data is sparse, the background degree is increased and the UCR amount is reduced. Even in this case, when the frequency of the high-luminance data is higher, the background degree is lower, and the UCR amount is further increased.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0024]

As described above, according to the present invention,
For the black line drawing part in the image, UC according to the background degree of the image
By performing the R processing, for example, a black line drawing portion in a white background
UCR processing is performed by increasing the amount of UCR, and black line drawing
UCR processing can be applied to parts with a small amount of UCR
And the black line drawing part in the white background is clearly
Faithfully reproduces the original, such as faithfully reproducing the black line drawing part of
can do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a reader unit 100 according to a first embodiment.

FIG. 2 is a side sectional view showing the internal configuration of the color copying machine according to the first embodiment of the present invention.

FIG. 3 is a diagram showing characteristics relating to a UCR amount.

FIG. 4 is a block diagram showing a configuration of a black removal circuit 114.

FIG. 5 is a diagram showing a processing image of an image by a black removal circuit 114;

FIG. 6 is a block diagram illustrating a configuration of a background determination circuit 119.

FIG. 7 is a block diagram showing a configuration of an edge detection circuit 115.

8 is a timing chart of the edge detection circuit 115. FIG.

FIG. 9 is a block diagram showing a configuration of a determination circuit 120.

FIG. 10 is a block diagram showing a configuration of a determination circuit 121.

FIG. 11 is a block diagram showing a configuration of a saturation determination circuit 116.

FIG. 12 is a diagram illustrating characteristics of a saturation signal Cr.

FIG. 13 is a diagram showing an example of low, medium, and large background degrees according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 101 CCD line sensor 102 Analog processing circuit 103 A / D converter 104 Shading correction circuit 105 Input masking circuit 106 Density conversion circuit 107 Encoder unit 108 Memory 109 Decoder unit 110 UCR circuit 111 γ correction circuit 112 Edge enhancement circuit 113 Printer unit 114 Black Removal circuit 115 Edge detection circuit 116 Re-determination circuit 117 Isolated point removal processing circuit 118 Smoothing processing circuit 119 Background determination circuit 120, 121 Determination circuit 122 Selector 123 AND gate 124 Memory 125 Companding unit 126 Black character determination unit 201 Platen glass 202 Document 203 Illumination 204, 205, 206 Mirror 207 Optical system 208 CCD 209 Motor 210 First mirror unit 211 Second mirror unit 212 Image Physical circuit section 213, 214, 215, 216 Semiconductor laser 217, 218, 219, 220 Polygon mirror 221, 222, 223, 224 Developing device 225, 226, 227, 228 Photosensitive drum 229, 230, 231 Paper cassette 232 Manual feed tray 233 Registration roller 234 Transfer belt

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-14378 (JP, A) JP-A-3-44271 (JP, A) JP-A-3-64264 (JP, A) JP-A-1- 174452 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1/46-1/64

Claims (4)

(57) [Claims] An input for inputting a plurality of color component signals representing an image.
Force means and a plurality of color component signals input by the input means.
Detecting means for detecting a black line drawing portion in the image; and a plurality of color component signals input by the input means.
Determining means for determining a background degree of the image; and a UCR amount according to the background degree determined by the determining means.
And the black line drawing part detected by the detection means is displayed.
UCR amount determined for a plurality of color component signals
UCR processing means for performing UCR processing by using UCR processing means, wherein the UCR processing means is determined by the determination means
When the background degree is low, compared to when the background degree is high.
An image processing apparatus for determining a large UCR amount . 2. The image processing apparatus according to claim 1, wherein the determination unit determines an average luminance of the image.
Calculating the degree of regularity, and calculating the image based on the average luminance and the degree of regularity.
2. The image processing apparatus according to claim 1 , wherein the background degree is determined . 3. The image processing apparatus according to claim 2, wherein the determining unit determines a luminance data of the image.
Calculating a histogram, and based on the histogram,
The image processing apparatus according to claim 1, wherein a background degree of the image is determined . 4. An input for inputting a plurality of color component signals representing an image.
And a plurality of color component signals input in the inputting step.
A detection step of detecting a black line drawing portion in the image; and a plurality of color component signals input in the input step.
Determining a background degree of the image; and determining a UCR amount according to the background degree determined in the determination step.
And the black line drawing part detected in the detection step is displayed.
UCR amount determined for a plurality of color component signals
And a UCR processing step of performing a UCR processing by using the UCR processing step, wherein the UCR processing step is determined by the determination step.
When the background degree is low, compared to when the background degree is high.
An image processing method characterized by determining a large UCR amount
Law.