JP3423709B2 - Image processing method and apparatus - 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 method and apparatus, and for example, to an image processing method and apparatus for reading a color original document and expressing the difference between the colors in black and white according to the color.

[0002]

2. Description of the Related Art Conventionally, a method of expressing a color difference by a pattern difference is described in, for example, Japanese Patent Publication No. 63-59303. In Japanese Patent Publication No. 63-59303, the color of an original document is discriminated, a pattern corresponding to the discriminated color is selected from a memory storing a plurality of patterns, and the pattern is output as a single color. There is. As a result, the chromatic color portion included in the original document image is reproduced in the corresponding pattern, and the other portion outputs luminance information.

[0003]

However, in the above-mentioned conventional example, when the AE (automatic exposure) is applied, the luminance distribution over the entire surface of the original is sampled as in the usual case.
Even the area (chromatic color portion) where the luminance information of the document is not output is sampled, and there is a drawback that AE is not performed accurately.

Further, when the original has a ground color, it is desirable that this background color portion is not patterned. However, in the prior art, when the background color portion of the original is judged to be chromatic, it is replaced with a pattern. There was a problem that it was printed.

The present invention has been made in view of the above conventional example, and it is an object of the present invention to provide an image processing method and apparatus in which the background color portion of an original is prevented from being patterned.

[0006]

In order to achieve the above object, the image processing apparatus of the present invention has the following configuration. That is, input means for inputting a color image, conversion means for performing a predetermined image conversion according to color on the color image input from the input means, and base color in the color image input from the input means are detected. And a control unit that controls the conversion unit so that the predetermined image conversion is not performed on the background color detected by the detection unit.

In order to achieve the above object, the image processing method of the present invention comprises the following steps. That is, a color image is input, the background color in the input color image is detected, and for a color other than the background color in the input color image, predetermined image conversion corresponding to the color is performed and output, It is characterized in that the color of the background color in the input color image is output without performing the predetermined image conversion.

[0008]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a copying machine in which the image processing apparatus of this embodiment is used.

This copying machine is provided with a printer section 22 in the lower part and an image reading section 3 in the upper part.
A photosensitive drum 1 has a photosensitive layer for electrophotography on its surface, and is rotationally driven in the direction of arrow X. Around the photosensitive drum 1, a primary charger 4, a cleaning unit 5, and a charger 6 are provided.
And the developing device 7 are respectively arranged.

Further, the image reading section 3 includes a platen glass 8
The upper original image is read, and the image reading unit 3
Platen glass 8, document irradiation lamp 9, scanning mirror 1
0, 11, an imaging lens 12, a three-color separation blazed diffraction grating 13, a CCD 14, and the like. Further, the halogen lamp 9 for illuminating the document is configured to scan and move integrally with the scanning mirrors 10 and 11, and scans the document in the sub-scanning direction at a preset constant speed.

The reflected light from the scanned original is reflected by the lens 1.
After passing 2, the three-color separated blazed diffraction grating 13 and CCD
Color separation is performed by 14 and converted into an electrical signal, and various image processing is performed on the original reading signal. After that, the laser light modulated by the image signal is emitted from the laser scanner unit 15, and this laser light is fixed mirror 16,
The photosensitive drum 1 is irradiated by 17 and the image is exposed. Further, reference numerals 18 and 19 denote copy cassettes on which copy sheets are stacked, and 20 denotes a conveyor belt for conveying the copy sheets on which the image is transferred by the charger 6 to the fixing device 21.

The CCD 14 has a solid-state image sensor array (line sensor) consisting of three lines corresponding to the respective colors of R, G and B, and the line sensors of the respective line sensors corresponding to the three primary colors of R, G and B are provided. The interval is determined according to the angle of view.
In this way, the document surface is line-scanned by a mirror (not shown) arranged between the lens 12 and the lens 12, which is an image forming optical system, and the color image is read by the blazed diffraction grating 13 for three-color separation via the lens 12. After being separated into three color light fluxes in, the image is formed on the line sensor corresponding to each color of the CCD 14.

The outline of the one-dimensional blazed diffraction grating 13 for three-color separation will be described with reference to FIG. The one-dimensional blazed diffraction grating 13 for three-color separation has a structure in which stepped gratings are periodically repeated in the color separation direction. For example, the periodic pitch P = 60 μm and the grating thickness d ₁ = d ₂ = 3100 μ.
When m and the medium refractive index = 1.5, the incident light is transmitted and diffracted and separated into three directions as shown in the figure.

FIG. 3 is a block diagram showing the overall construction of the image processing section of the digital copying machine of this embodiment.

In the figure, reference numeral 100 is an amplifier circuit for amplifying the output signal of the CCD image sensor 14, which is CC
The output signal of the D image sensor 14 is amplified to a predetermined output. Reference numeral 101 is an A / D converter for converting the amplified image signal into a digital signal, and 102 is a black correction / white correction circuit for performing a black level correction and a white level correction (shading correction) described later on the digital image signal. is there. The amplifier circuit 100, the A / D converter 101, and the black correction / white correction circuit 102 are included in the input image processing unit 1000. A luminance signal generation unit 103 generates a luminance signal from the digital image signals (R _OUT , G _OUT , B _OUT ) after black correction and white correction. Reference numeral 104 denotes an AE data sampling unit that samples luminance information when performing automatic exposure, and the CPU 110 samples the luminance information stored therein to measure the luminance distribution on the document. A pattern synthesis circuit 105 synthesizes the luminance signal sampled by the AE data sampling unit 104 and the pattern signal 116 output from the pattern generation circuit 108 indicating the number of colors. 1
Reference numeral 06 is a LOG conversion unit that converts the signal output from the pattern synthesis circuit 105 into a density signal and outputs the density signal to the printer unit 22. A color discrimination circuit 107 discriminates the color of each pixel of the digital color image signal after black / white correction, and outputs the discrimination signal 117 to the pattern generation circuit 108. The pattern generation circuit 108 inputs the discrimination signal 117 from the color discrimination circuit 107, and outputs the pattern signal 116 and the HIT signal 115 which are determined corresponding to each color. 110 is a CPU for controlling the entire apparatus, 111
Is a ROM that stores programs for operating the CPU 110 and various data, and 112 is a RAM that is used as a work area during control processing by the CPU 110.

Next, the copying operation in the copying machine having the above construction will be described. In this copying machine, the color original image is read by the monochrome copying machine and the pattern corresponding to the color of the original is printed, so that the color of the original image can be discriminated even in the monochrome printed image. It is a thing.

FIG. 4 is a flow chart showing a copying operation in the copying machine according to the present embodiment.

The image reading section 3 is a CCD sensor 1 including three lines of R (red), G (green) and B (blue).
The color original is read by scanning 4 with respect to the original, and the read color image signal is converted into an analog electric signal and output (step S1). This analog image signal is amplified by the amplifier 100, sampled and held, dark level correction and dynamic range adjustment are performed, and the A / D converter 101 performs A / D conversion on R, G, and B signals. D conversion is performed. The image signal thus converted into a digital signal is subjected to shading correction by the black correction / white correction circuit 102 according to the light receiving sensitivity of the CCD sensor 14 (step S2).

The digital image signal (R
_OUT , G _OUT , B _OUT ) are input to the luminance signal generation unit 103 and converted into luminance signals (step S3). As shown in FIG. 5, the conversion method to the luminance signal is (R _OUT + G
_OUT + B _OUT ) × 1/3 is performed to generate a luminance signal. In FIG. 5, 301 denotes an adder for adding R _{OU T} input, G _OUT, the B _OUT color signals,
302 is the result of addition from the adder 301 divided by 3,
The figure shows a divider that calculates the average value of three color signals. The brightness information thus generated is sent to the pattern synthesizing unit 105 via the AE data sampling unit 104. As will be described later in detail, when a general copying operation is performed, the brightness information corresponds to the output density of the printer unit 22 from the brightness signal in the LOG conversion unit 106 via the AE data sampling unit 104 and the pattern synthesis circuit 105. The density signal is converted and the image is output by the printer unit 22.

On the other hand, the R _OUT , G _OUT , and B _OUT signals corrected by the black correction / white correction unit 102 are sent to the color discrimination circuit 107. The color discriminating circuit 107 discriminates the color region and color type of each pixel of the original image, and the discriminating signal 117 as a result of the discrimination is sent to the pattern generating circuit 108 (step S4). The pattern generation circuit 108 is a RAM, RO
It is composed of a memory such as M, and outputs a HIT signal 115 indicating a region where color patterning is performed together with a pattern signal 116 according to the color type of the discrimination signal 117. The HIT signal 115 is sent to the AE data sampling unit 104 (step S5). This makes AE
The data sampling unit 104, when sampling the luminance information, except for the area where the HIT signal 115 is output,
That is, the luminance information outside the area where color patterning is performed is sampled. In this way, the area that does not need to sample the luminance information, that is, the area where the pattern is output and the luminance information is not output is configured not to be sampled during AE (step S6).

Further, the HIT signal 115 and the pattern signal 116 output from the pattern generating circuit 108 are input to the pattern synthesizing circuit 105, where the luminance information and the pattern signal 116 are synthesized, and the chromatic color portion of the document becomes a pattern. It is changed (step S7). That is, HIT signal 1
The pattern signal 116 is output to the image area where 15 is output (color area where the corresponding pattern exists), and the luminance information is output to the area where the HIT signal 115 is not output (color area where the corresponding pattern does not exist). As described above, the image signal composited in (1) is converted from luminance to density by the LOG conversion unit 106 and sent to the printer unit 22 (step S8).

Next, the configuration of each part of the image processing of the present embodiment shown in FIG. 3 will be sequentially described.

[Black Correction / White Correction Circuit] FIG. 6 is a diagram showing the configuration of the black correction circuit of the black correction / white correction circuit 102 of the present embodiment.

A / D converted CCD image sensor 1
The digital color image signal from 4 has a large variation between pixels when the amount of light input to the CCD image sensor 14 is small. If this is output as it is as an image, streaks and unevenness occur in the data part of the image, so it is necessary to correct the variations in the output of this black part. Therefore, correction is made by a circuit as shown in FIG.

Prior to the reading operation of the original, the original scanning unit of the image reading unit 3 is moved to a black plate having a uniform density arranged in the non-image area at the leading end of the original table 8 and the lamp 9 is turned on. The black level image signal is input to the black correction circuit. Now, the circuit 77aB relating to the blue signal B _IN will be described. In order to store one line of this image data in the black level RAM 78a, the A input of the selector 82a is selected, the gate 80a is closed, and the gate 81a is opened.
That is, the data line is connected to 151a → 152a → 153a. On the other hand, the address 155a of the RAM 78a is initialized by HSYNC, and the signal 623 to the selector 83a is output so that the output 154a of the address counter 84a for counting VCLK is input, and the black level signal for one line is stored in the RAM 78a. Stored in. (The above is called the black reference value capture mode).

Thus, when actually reading the image, R
The AM 78a enters the data read mode and the data line 15
The black reference value of the RAM 78a is read and input to the B input of the subtractor 79a on a line 3a → 157a for each line and for each pixel. That is, at this time, the gate 81a is closed and the gate 80a is open. Further, the selector 86a has an A output. Therefore, the output 156a from the black correction circuit is
With respect to the black level data DK (i), for example, in the case of a blue signal, it is obtained as B _IN (i) −DK (i) = B _OUT (i) (called a black correction mode). Similarly, green G _IN and red R _IN are also controlled by 77aG and 77aR.

Further, for the purpose of this control, the control lines 621 to 625 of the respective selector gates are I / O of the CPU 110 (FIG. 3).
Latch 85a assigned as O causes CPU 110
Under the control of. The RAM 78a can be accessed by the CPU 110 by selecting the B input of the selectors 82a and 83a and the B output of the selector 86a.

FIG. 7 is a block diagram showing the configuration of the white correction circuit of the black correction / white correction circuit 102 of this embodiment.

CCD for reading the original at the time of color correction
When 14 is at the reading position (home position) of the uniform white plate, that is, before the copying operation or the reading operation, the exposure lamp 9 is turned on and the pixel data of the uniform white level is stored in the correction RAM 178a for one line, for example. Therefore, the selector 182a selects A, the gate 180a is closed, and the gate 181a is opened. Thus the data line is 1151a
→ 1152a → 1153a. On the other hand, RAM
Inverted H is applied to the address input 1155a of 178a.
Initialized by SYNC, the A input of the selector 183a is output so that the output 1154a of the address counter 184a that counts VCLK is input, and the white level signal (white reference value) for one line is stored in the RAM 178a. Here, the capacity of the RAM 178a is 16 if the main scanning direction has a length in the longitudinal direction of A4 size, for example.
pel / mm 4752 (= 16 × 297 mm) pixels (W _{0 to} W
₄₇₅₁ ), that is, at least 4752 bytes are required.

Next, other than the pattern replacement mode in which the color area of the read image is replaced with a pattern (hereinafter referred to as a normal mode)
Then, for the reading value Di of the i-th pixel for W _i ,
Since the image data is 8 bits, the shading correction coefficient P ₀ = FFH (H represents a hexadecimal number) is used, and the corrected data D _O should be D _O = D _i × FFH / W _i. is there.

On the other hand, in the pattern replacement mode,
Trading correction coefficient is P₁And then W _iI-th corresponding to
Image reading D_iData D after correction for_O’
D_O′ = X0 ≦ x ≦ FFH = FFHx> FFHx = D_i× P
/ W_ix ≧ 0 However, P₁> It should be like FFH.
The correction coefficient P₁For AE data described later
As described in the description of the sampling unit 104,
Obtained by scanning and reading the draft image in advance
Be done. Also, data sampling operation and sampling
For the histogram of the group data, see FIGS.
As will be described later with reference to FIG.
Since it is H ", the above-mentioned correction coefficient P₁Is P₁= (FFH / D
0H) × FFH = 138_HAlso, for example, the background level is B0_H
Then, P₁= (FFH / B0_H) × FFH, which
The correction table is as shown in Fig. 19, and the input level
The output level becomes "FFH" at "B0H". That is, the ground
The skin will fly.

Therefore, the CPU 110 latches the latch 185a.
Signals 701 to 705 from the gates 180a and 181
a is opened, and further, the B inputs of the selectors 182a and 183a and the B output of the selector 186a are set to be selected, and the RAM 178a is made accessible by the CPU 110. Next, CPU 110 may, FFH / W ₀ to the top pixel W ₀ data _{RAM178a, P 1 / W 0,} W i to _{FFH / W i, P 1 /} W i ... sequentially calculates, in the normal mode The correction value for the pattern replacement mode is stored in the RAM 178a, and the correction value for the pattern replacement mode is stored in the RAM 187a. Therefore, when storing the data for the normal mode, the B input of the selector 183 is selected, the gate 181a is opened, the gates 189a, 180a, 188a are closed, and R
Write the correction value to AM178a. On the other hand, in order to store the data for the pattern replacement mode, the gate 181
a, 180a, 188a are closed, the gate 189a is opened, and the correction value may be written in the RAM 187a. When the processing for the blue component of the color component image is completed in this way, writing is similarly performed in the corresponding RAMs of the green component and red component circuits 177aG and 177aR.

Next, the case of the normal mode (without pattern replacement) will be described. The gate 180a is opened, the gates 188a, 181a and 189a are closed, and the RAM 178 is opened.
The data FFH / W _i is read from a. This makes 11
It is input to the multiplier 179a through 53a → 1157a, multiplied by the original image data 1151a input to the other input terminal of the multiplier 179a, and output.

On the other hand, in the pattern replacement mode,
Gates 180a, 181a, 189a are closed, gate 1
Data P ₁ / W _i from RAM 187a by opening 88a
Is read and passes 1158a → 1157a, and the multiplier 1
79a, and the original image 1151a input from one of the input terminals is multiplied and output. Here, it is assumed that the multiplier 179a is designed so that the output becomes FFH if the operation result exceeds FFH. Further, the switching control of each of these gates can be performed prior to the reading of the original by the CPU 110 because it is known in advance whether the process for the original will perform pattern replacement.

[Description of AE Data Sampling Unit 104] Next, the AE data sampling unit 104 will be described.

FIG. 8 is a block diagram showing the configuration of the AE data sampling section 104 of this embodiment. In the figure, 601 is a counter, 602 and 604 are selectors,
Reference numeral 603 is a RAM, 605 is a flip-flop, and 606 is a buffer. The counter 601 generates an address when storing the brightness information in the RAM 603. The selector 602 selects the address of the counter 601 when the select signal 610 is “1” and selects the RAM 60.
3 and outputs the luminance information selected by the selector 604 to R
Store in AM603. At this time, the luminance signal in which the HIT signal is set in the MSB is selected. Thus, RAM6
The luminance information is stored in 03, in other words, it is sampled. Further, the MSB of the data of the RAM 603 stores the luminance signal and the HIT signal whose delay relationship is adjusted. Therefore, by checking the data of the MSB of the RAM 603, the data is the luminance information of the color-determined area. It will be possible to determine whether or not there is.

Next, the data in the RAM 603 is transferred to the CPU 11
When 0 is read, the select signal 610 is set to “0”,
Input the address bus of the CPU 110 to the RAM 603,
When the CPU 110 reads, the gate of the buffer 606 is opened and the data of the RAM 603 is read. When the luminance information is directly output to the pattern synthesizing circuit 105, the select signal 610 is set to “1”, the selector 604 outputs the luminance signal, and the flip-flop 605 outputs the luminance signal to the pattern synthesizing circuit 105. The clock of the flip-flop 605 is VCK
(Video transfer clock), and the clock of the counter 601 is also the same VCK.

That is, the AE data sampling section 104
Then, the luminance signal once stored in the RAM 603 is stored in the CPU 110.
However, since the data whose MSB of the read data is "1" is within the color determination area, the data is discarded and AE data is created only by the luminance signal outside the color determination area.

Next, the color discrimination circuit 107 will be described.
In this embodiment, a hue signal is used as the color discrimination method. This is because even if the color is the same, but the saturation and brightness are different, accurate determination can be performed. First, an outline of the color detection method in the color discrimination circuit 107 will be described.

FIG. 9 is a diagram for explaining a color plane for hue conversion.

The input R, G and B data are each 8 bits and have a total of 2 ²⁴ color information. Therefore, using such enormous information as it is becomes expensive due to its circuit scale.

In the present embodiment, the above-mentioned hue is used, and although it is different from the hue which is usually expressed, it is called hue here. It is known that the color space is represented by saturation, lightness, and hue, as is known in Munsell's solid and the like. It is necessary to first convert the R, G, B data into plane or two-dimensional data.
Common part of R, G, B, that is, the minimum value min of R, G, B
Since (R, G, B) is an achromatic component, min (R,
G, B) is subtracted from each R, G, B data, and the remaining information is used as a chromatic color component to convert the three-dimensional input color space into a two-dimensional color space. As shown in FIG. 9, the converted plane is divided into 6 from 0 ° to 360 °, and the order of the sizes of R, G, and B to be input, that is, R>G>
B, R>B> G, G>B> R, G>R> B, B>G>
The hue value is obtained by using a LUT (look-up table) or the like based on the information of R, B>R> G and the maximum value or the intermediate value of the input R, G, B.

Next, the structure of the color discrimination circuit 107 will be described.

FIG. 10 shows a color discrimination circuit 1 according to this embodiment.
It is a block diagram which shows the structure of 07.

In the figure, 401 is a max.mid.min detection circuit, 402 and 403 are subtractors, 404 is a hue detection circuit, 415 and 416 are color judgment circuits, 405 and 406 are window comparators, 410 is an AND gate, Reference numerals 407 denote CPUs, respectively. The color determination circuits 415 and 416 have the same configuration.

Next, the operation of the color discrimination circuit 107 will be described.

The R _OUT , G _OUT , and B _OUT data that is input is first input to the max.mid.min detection circuit 401 that determines the magnitude of the data. This compares each input data using a comparator, and depending on the comparison result, the max (maximum) value, m
Outputs the id (center) value and min (minimum) value. Further, the output value of each comparator is output as the order signal 420. As described above, the max, mid, and min values output in this way subtract the a minimum color value from the max and mid values by subtracters 402 and 403 in order to subtract the achromatic color component from the max and mid values. , Order signal 4 to the hue detection circuit 404
It is input together with 20. The hue detection circuit 404 is a RAM
Alternatively, it is a randomly accessible storage element such as a ROM, and in the present embodiment, the lookup table is configured using the ROM. A value corresponding to the angle of the plane as shown in FIG. 9 is stored in advance in the ROM, and the hue value is output according to the input order signal (max-min) value and (mid-min) value. . The output hue value is then input to the window comparators 405 and 406. The values set in the window comparators 405 and 406 are, when the hue value of the color data originally to be patterned is input by the data input means (not shown), the hue data value is used as an offset value by the CPU 407. The value to be set. Now, assuming that the value set in the comparator 405 is a _1, with respect to the hue data input from the hue detection circuit 404, when (hue data) <a ₁ , “1” is output from the comparator 405 and set in the comparator 406. When the calculated value is a ₂ (a ₁ > a ₂ ), “1” is output from the comparator 406 when (hue data)> a ₂ . Thus, the subsequent AND gate 410 outputs "1" when a _1> (hue data)> a _2, this is the output of the color determination circuit 415.

Further, by the same operation as the color judgment circuit 415, the color judgment circuit 416 judges a color different from the color judged by the color judgment circuit 416. In the present embodiment, the types of colors to be determined are configured as two types, but the present invention is not limited to two types and may be three or more types.

[Pattern Generating Circuit] Next, the pattern generating circuit 108 will be described.

FIG. 11 is a block diagram showing the configuration of the pattern generation circuit 108 of the present embodiment, and FIG. 12 is a diagram showing the correspondence relationship between the color of the original image and the output pattern.

In FIG. 11, reference numeral 801 is a sub scanning counter, 802 is a main scanning counter, and 803 is a pattern RO.
M is shown respectively. ROM803 for this pattern
A dot pattern corresponding to each color as shown in FIG. 12, for example, is written in advance. In FIG. 12, the pattern of each figure is pattern data of 16 × 16 dots. The pattern ROM 803 generates a pattern by repeatedly outputting the pattern corresponding to the color determination signal 117 according to the signals from the main scanning counter 802 and the sub scanning counter 801. Main scanning counter 8
An initial value 02 is loaded by the horizontal synchronizing signal HSYNC, counts the video clock CLK to generate an address in the main scanning direction, and the sub-scanning counter 801
Initial value is loaded by ITOP signal and horizontal sync signal HSY
An address in the sub-scanning direction is output by counting NC.

The outputs of the counters 801 and 802 are each 4
The color judgment signal 117 consists of 5 bits, and a total of 13 bits.
Bit data is input as an address of the pattern ROM 803. That is, the structure is such that a pattern of 16 dots × 16 dots can be generated for the read 32 kinds of colors.

The output from the pattern ROM 803 has a data length of 8 bits, of which the MSB
The (most significant bit) is used as a control signal (HIT signal 115) in the pattern synthesizing circuit 105 described later, and this MSB is normally "0", and is always "1" when generating a pattern. The data is written so that The pattern ROM 803 may be replaced with a rewritable memory such as a RAM. Also, RA
Even if M or the like is used, its capacity and bit allocation of addresses are the same as those of the ROM.

[Pattern Synthesis Circuit] Next, the configuration of the pattern synthesis circuit 108 will be described.

FIG. 13 is a block diagram showing the structure of the pattern synthesizing circuit 105 of this embodiment. In the figure,
A selector 501 is an AE data sampling unit 104.
Luminance signal sampled by the pattern generation circuit 1
One of the pattern signals 116 generated in 08 is selected according to the HIT signal 115 from the pattern generation circuit 108. Since the area where the HIT signal 115 is "1" is the area where the original image is determined to be chromatic, the pattern signal 116 corresponding to that color is selected and L
In the region where the HIT signal 115 is “0”, the luminance signal is output to the OG conversion unit 106 and is output to the LOG conversion unit 106 as it is.

[LOG Converter] Next, the LOG converter 10
The configuration of No. 6 will be described.

The LOG converter 106 is a ROM or R
It is made up of a lookup table such as AM. In this embodiment, a ROM is used for simplicity. From the sampled AE data, the CPU 110 selects an appropriate LOG conversion table and performs LOG conversion.

FIG. 14 shows the LOG converter 10 of this embodiment.
6 is a diagram showing a specific example of LOG conversion characteristics in FIG. In the figure, (A) shows a conversion characteristic in which the input density and the output density are linear. Further, for example, when the AE data is sampled, it is determined that the document is a document such as characters, and if it is desired to eliminate the fog on the white background of the document, the LOG conversion characteristic as shown in (B) is selected. That is, when the input density is large (white) to some extent, the output density is "0", that is,
Replace it with white to eliminate the fog. Also, AE
At the time of data sampling, if a certain density level is concentrated in the document, select the characteristic shown in (C),
Widen the dynamic range of a certain concentration level.

As described above, according to the present embodiment, when performing color patterning, it is determined whether or not the sampled luminance information is within the color determination area, and it is not within that area, and AE In the case of applying, the luminance distribution on the entire surface of the original is sampled to form a color pattern. Further, when the luminance information of the document is within the color judgment area, the luminance information sampled for the AE is not used, so that the accurate AE is obtained.
Can be realized.

<Second Embodiment> Next, as a second embodiment, AE in the case of expressing a difference in color by a difference in black and white density will be described.

The basic idea is the same as that of the above-mentioned embodiment, and accurate AE is applied by dropping the AE sampling data in the area where the color density conversion is performed. The circuit configuration in this case is as follows:
08 is changed to a luminance generation circuit, and the pattern R
Instead of the pattern corresponding to each color described above, the brightness data corresponding to each color may be written in the OM 803.

<Third Embodiment> Next, a third embodiment will be described.

In the third embodiment, regarding the AE in the case of performing the color density conversion, the luminance information for performing the AE is sampled by directly sampling the luminance on the original in the area where the color density conversion is not performed. A description will be given of a case where normal AE is applied to the output image as a result by sampling the luminance information of the image after conversion for the region to be converted. For example, when the density after the color density conversion is close to black, the overall output image becomes relatively blacker, which has the effect of applying AE to the overall output image.

FIG. 15 is a block diagram showing the configuration of the image processing apparatus according to the third embodiment of the present invention, and the portions common to FIG. 3 are designated by the same numbers. In FIG. 15, reference numeral 721 denotes a luminance generation circuit, which has a configuration in which luminance data corresponding to a color is written in the pattern ROM 803 instead of the pattern, as described in the second embodiment. Reference numeral 722 denotes a luminance synthesizing circuit, which is used for the luminance signal generation unit 103.
The brightness signal on the original generated by the HIT signal 1 and the brightness signal 723 expressing the difference in color as the difference in brightness.
The selection is made by means of 15 and can be realized by replacing the pattern signal 116 input to the selector 501 in FIG. 13 with the luminance signal 723 from the luminance generation circuit 721.

Reference numeral 720 denotes an AE data sampling unit, which is the same as the configuration described in the first embodiment, and additionally has a color discrimination circuit 107.
The determination signal 117 indicating the type of color determined by is input. The input discrimination signal is M in FIG.
It is input to bits other than the HIT signal, which is SB. For example, if the RAM 603 has an 8-bit configuration, bit 7 is the HIT signal, bits 5 and 6 are the discrimination signals, and bit 0 is the bit.
~ 4 becomes the luminance signal. Further, although the delay relationship among the HIT signal, the color classification signal, and the luminance signal is not described, all delay relationships will be combined when actually realized.

In the above-described embodiment, when the entire surface of the original document has a background color such as a light pink color, the background color is also replaced with the pattern, and the entire surface of the printed sheet becomes a pattern image. The image becomes difficult to see. An embodiment will be described in which an excellent patterned output image can be obtained even on such an original.

<Fourth Embodiment> FIG. 16 is a block diagram showing the arrangement of an image processing unit according to the fourth embodiment of the present invention.
The same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 16, during pre-scan for AE,
The CPU 110a causes the AE data sampling unit 730 to use the RAM 101a to generate a density histogram on the document as shown in FIG. The basic circuit operation of the AE data sampling unit 730 is the same as that of the first embodiment described above.

Next, the AE data sampling section 730 will be described with reference to FIG. The AE data sampling unit 730 samples the image signal I _out, which has been subjected to shading correction by the input image processing unit 1000 and converted into a luminance signal, for each line, and the level thereof is determined by the CPU 11
0a detects the level range of the read image data by creating a reading histogram, and performs AE correction so as not to determine the color of the background level of the document.
Image data is sampled by the circuit shown in FIG.

The sampling of the AE-corrected image data is performed by prescanning the original image before the actual reading operation of the original image. That is,
The gate 2103 is opened by the signal 1701 to store one line of the image data I _out , which has been subjected to the shading correction and converted into the luminance signal I _out , in the RAM 2105.
At 702, the gate 2104 is closed. That is, the data line is connected to 2110 → 2111, while the RAM 2105
The address 211 of the selector 2 is initialized by the inverted HSYNC signal and the output 2113 of the address counter 2101 for counting VCLK is input.
A selection signal 1700 for 102 is output. The luminance signal data for one line is stored in the RAM 2105 (the above is the image data sample mode).

When the image is read, the RAM 21
05 becomes the data read mode, and the data line 2111 →
In the path 2115, the image data sampled for one line is read into the CPU 110a of FIG. 16 through the data bus (D-Bus). At this time, the CPU 110a
The image data read in is not all pixel data for one line, but one pixel for every 1 mm, that is, 16 pixels, and data for 293 pixels / line in the A4 longitudinal direction is read by the CPU 110a. Furthermore, in the sub-scanning direction,
Same as main scanning direction, 1mm interval, ie 1 in 16 lines
The above-mentioned image data sample mode is executed once
Data of (293 pixels / line) × 206 lines = 60358 pixels is sampled from a 4 size original.

At this time, the gate 2103 is closed by the selection signal 1701, and the gate 2 is opened by the selection signal 1702.
104 is opened. In addition, the selector 2102 causes the selection bus 1700 to select the address bus (AB
(us) B input is selected, and the address line 2114 → 21
An address is input to the address input of the RAM 2105 via the 12 route. Here, the selection signals 1700 to 1702 of each selector gate for this control are I of the CPU 110a.
It is output from the latch circuit 2106 assigned as / O.

By the way, as described above, the data sampled from the A4 size original is processed by the CPU 110a to create a histogram. For example, for a manuscript, such as a newspaper, whose background is slightly dark and contains characters, etc.
A histogram as shown in 8 is created. That is, FIG.
8, the luminance peak of the background portion appears at the luminance data value “E0H”, and the luminance peak of the character portion appears at the luminance data value “25H”. Here, when the color of the background portion is suppressed because it is not patterned, the luminance signal I is corrected so that the peak value “E0H” of the background becomes “FFH”.
alone was added to the _out, for the distribution of the histogram of the background portion is a Gaussian distribution distribution, thus completely become impossible to skip the background portion. Therefore, the parameter l of the spread of the bottom of the histogram distribution of the background part
Considering (H = 10H), a correction (in FIG. 19) is added so that “D0H” becomes “FFH”.

In this embodiment, the correction is performed by adding the correction shown in FIG. 19 to the LOG table of the LOG conversion unit 106 described above. In FIG. 19, the characteristics are normal, those for converting the image level “D0H” into “FFH”, and those for the image “B0 with a deeper background level”.
The table shows the values for converting "H" to "FFH" to remove the background.

FIG. 20 shows the background signal processing section 73 of the embodiment.
18 is a block diagram showing the configuration of No. 1 and includes a comparator 141, a register 142, and an AND gate 14 as shown in FIG.
It consists of three. As the operation, first, the CPU 10
1a sets the background level value "D0H" obtained by the AE prescan in the register 142 before the main scan. During the main scan, the comparator 141 compares the video signal generated by the luminance signal generation unit 103 with the value “D0H” set in the register 142. When the video signal is smaller than the set value "D0H", that is, when it is darker than the set value, the high level signal is set to A.
When it is output to the ND gate 143 and is larger than the set value “D0H”, that is, when it is brighter than the set value, a low level signal is output to the AND gate 143, and the color discrimination circuit 10
The color discrimination signal 117 output from the No. 7 is controlled to be turned on / off. The color discrimination signal 117 controlled in this way
Are output to the pattern generation circuit 108 in the subsequent stage. The subsequent operation and control are the same as those in the above-described embodiment, and thus the description thereof is omitted. Further, this configuration can be applied to the case where the above-described color is converted into luminance. In this way, "D0H" to "FFH" are set as the background luminance signal area, and the output of the image data in this area is suppressed to realize the AE.

As described above, according to the fourth embodiment, since the background color of the original is detected and the background color is not patterned, only the image of the necessary portion is patterned to obtain an easily viewable image. To be

[Other Embodiments of White Correction Circuit of Black Correction / White Correction Circuit] FIG. 21 is a block diagram showing a configuration of a white correction circuit of another embodiment of the black correction / white correction circuit of the present invention. The parts common to those of the white correction circuit of the above-described embodiment shown in FIG. 7 are indicated by the same numbers, and the description thereof is omitted.
Here, a multiplier 190a is further inserted between the multiplier 179a and B _OUT, and a signal from the data bus (DBUS) is further input to the multiplier 190a via the register 191a. Then, the signal line 1156 from the multiplier 179a
Until D _i × FFH / W _i is output to a, control is performed in the same manner as in the conventional example, and thereafter, the CPU 110 causes the register 191 to operate.
Data which is "1" in the normal mode is set to a and is output to the B input of the multiplier 190a, and in the pattern replacement mode, the CPU 110 sets, for example, "P" in the register 191a.
A signal corresponding to ₁ / FFH ”is set and the multiplier 190a
Output to B input B. As a result, D _i × FFH / W _i is output to B _OUT when not in the pattern replacement mode, and D _i × P ₁ / W _i is output to B _OUT in the pattern replacement mode. Here, it is assumed that the multiplier 190a is designed so that its output becomes "FFH" if the operation result exceeds "FFH". The method of obtaining the correction coefficient P ₁ and the data of the correction table of the LOG conversion unit 106 are the same as those in the above-described embodiment.

In addition, another embodiment of this white correction circuit
Then, the CPU 110 can access the data in the RAM 178a.
The same control as above is performed until it becomes available, and then C
The PU 110 has the first pixel W in the normal mode.₀Against FFH /
W₀, Next pixel W_iAgainst FFH / W_iAnd so on
In the pattern replacement mode, for example,
If the correction factor is larger than “FFH”, P₁Then, the beginning
Pixel W₀On the other hand, P ₁/ W ₀, W_iAgainst P₁/ W_iSay
It is also possible to calculate data sequentially and replace the data.
Yes. This procedure is shown in the flowchart of FIG.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can also be applied to the case where it is achieved by supplying a program for implementing the present invention to a system or an apparatus.

[0081]

As described above, according to the present invention, it is possible to prevent the background color portion of a document from being patterned.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a copying machine in which an image processing unit according to the present invention is used.

FIG. 2 is a diagram for explaining a diffraction grating of a CCD sensor.

FIG. 3 is a block diagram showing a configuration of an image processing circuit according to the first embodiment.

FIG. 4 is a flowchart illustrating an image processing procedure in the image processing circuit according to the present embodiment.

FIG. 5 is a block diagram showing a configuration of a luminance signal synthesizing unit according to the embodiment.

FIG. 6 is a block diagram showing a configuration of a black correction circuit according to an embodiment.

FIG. 7 is a block diagram showing a configuration of a white correction circuit according to the embodiment.

FIG. 8 is a block diagram showing a configuration of an AE data sampling unit according to the embodiment.

FIG. 9 is a diagram illustrating a color plane for hue conversion.

FIG. 10 is a block diagram showing a configuration of a color discrimination circuit according to an embodiment.

FIG. 11 is a block diagram showing a configuration of a pattern generation circuit according to an embodiment.

FIG. 12 is a diagram showing correspondence between colors and patterns.

FIG. 13 is a block diagram showing a configuration of a pattern synthesizing circuit according to the embodiment.

FIG. 14 is a diagram showing a specific example of a LOG conversion circuit according to an embodiment.

FIG. 15 is a block diagram showing a configuration of an image processing circuit according to a second embodiment of the present invention.

FIG. 16 is a block diagram showing a configuration of an image processing circuit according to another embodiment.

17 is a block diagram showing the configuration of the AE data sampling unit of FIG.

FIG. 18 is a diagram showing an example of a luminance histogram of a character original image with a background color.

FIG. 19 is a diagram showing an example of data of a base color correction table.

20 is a block diagram showing a configuration of a background signal processing unit in FIG.

FIG. 21 is a block diagram showing a configuration of a color correction circuit according to another embodiment.

FIG. 22 is a flowchart for explaining white correction according to another embodiment.

FIG. 23 is a diagram showing an example of correction table data used in a LOG conversion unit.

[Explanation of symbols]

14 CCD sensor 101 A / D converter 102 black correction / white correction circuit 103 Luminance signal generator 104,730 AE data sampling unit 105 pattern synthesis circuit 106 LOG converter 107 color discrimination circuit 108 pattern generation circuit 110 CPU 115 HIT signal 116 pattern signal 404 Hue detection circuit 601 counter 602, 604 selector 610 Select signal 731 Background signal processing unit 1000 Input image processing unit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shizuo Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-2-295364 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) H04N 1/46-1/64 G06T 1/00 510 G06T 5/00 100

Claims (6)

(57) [Claims] 1. An input unit for inputting a color image, a conversion unit for performing a predetermined image conversion according to a color on the color image input from the input unit, and a background in the color image input from the input unit. An image processing comprising: a detection unit that detects a color; and a control unit that controls the conversion unit so that the predetermined image conversion is not performed on the background color detected by the detection unit. apparatus. 2. The image processing apparatus according to claim 1, wherein the conversion means converts the pattern image into a pattern image corresponding to a color. 3. The image processing apparatus according to claim 1, wherein the conversion unit converts a density image having a density corresponding to a color. 4. A color image is input, a background color in the input color image is detected, and a predetermined image conversion corresponding to the color is performed for colors other than the background color in the input color image. An image processing method comprising outputting the output color without performing the predetermined image conversion for the color of the background color in the input color image. 5. The image processing method according to claim 4 , wherein in the predetermined image conversion, a pattern image having a pattern corresponding to a color is converted. 6. The predetermined image conversion is to convert to a density image having a density corresponding to a color.
4. The image processing method according to item 4 .