JP2866101B2 - Color image processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image processing apparatus having a marker color conversion function of converting a portion of a black character of a black-and-white document surrounded by a marker portion into the same color as a specific color. About.

(Background of the Invention) A color image such as a character image or a photographic image is optically read by being divided into red R and cyan C, and based on the read, the image is recorded on a recording paper using an output device such as an electrophotographic output device. There is a color image processing apparatus described above.

Some of such image processing apparatuses have a function of marker color conversion (a process of converting a portion of a black character of a black-and-white document surrounded by a marker portion into the same color as a specific color).

(Problems to be Solved by the Invention) When the marker color conversion is performed by the above-described apparatus, since reading and recording are performed in red / cyan or red / blue / black, the marker other than the red or blue single color marker is used. Cannot perform color conversion. That is, there is a problem that a portion surrounded by a marker portion other than red or blue is not accurately converted.

In addition, color images such as character images and photographic images are optically read by separating them into red R, green G, and blue B, and these are read as yellow Y and magenta.
There is a color image processing apparatus that converts the image data into recording colors such as M, cyan C, and black K, and records the image on recording paper using an output device such as an electrophotographic color copying machine based on the color. Such an apparatus can read and record a color original. However, in such an apparatus, no consideration has been given to performing full-color marker color conversion. That is, there has been no method for reading various marker colors or processing for accurately converting black characters into marker colors.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to realize a color image processing apparatus capable of performing full-color marker color conversion with a simple configuration.

(Means for Solving the Problems) The present invention for solving the above problems is a color image processing apparatus having a marker color conversion function of converting a portion surrounded by a marker portion of black characters of a black and white original into the same color as a specific color. An image reading means for reading an original image as a color separation image; a color code generation means for generating a color code for discriminating the color separation image of the original image into an achromatic portion and a chromatic portion in pixel units;
Color reproduction means for converting the color separation image of the original image into recording color density data corresponding to the recording color, and a marker area for detecting the area of the marker portion in the original image based on the color code from the color code generation means Detecting means for sampling the recording color density data of the marker portion and converting the recording color density data of the original image in the area surrounded by the marker portion into recording color density data corresponding to the color of the marker portion; Marker color conversion means for determining a normalization factor for each recording color from the maximum value of the recording color density data of the marker portion, and surrounding the marker portion by the normalization factor. Characterized in that it is configured to process the recording color density data of the original image in the specified area.

(Operation) In the color image processing apparatus of the present invention, the marker color conversion means obtains a normalization factor for each recording color from the maximum value of the recording color density data of the marker portion, and surrounds the marker portion with the normalization factor. Process the recording color density data of the original image in the specified area.

(Embodiment) Hereinafter, an electrical configuration of an embodiment of the present invention will be described in detail with reference to the drawings.

First, the outline of the image processing apparatus of the present invention will be described with reference to FIG. In this figure, 1 is an R-CCD for converting a red original image to an image signal, 2 is a G-CCD for converting a green original image to an image signal, and 3 is a B-CCD for converting a blue original image to an image signal. The CCD 4 converts the red image signal read by the R-CCD 1 into 8-bit digital data.
A D / D converter 5; an A / D converter for converting a green image signal read by the G-CCD2 into 8-bit digital data;
An A / D converter converts a blue image signal read by B-CCD3 into 8-bit digital data. Reference numeral 7 denotes a density converter for converting red 8-bit digital data to 6-bit digital data, 8 denotes a density converter for converting green 8-bit digital data to 6-bit digital data, and 9 denotes a blue 8-bit digital data. It is a density converter for converting to bit digital data. 10 is a color code (2-bit code indicating whether each pixel is white / black / chromatic, for example, white: 00, black: 11, chromatic: 10)
This is a color reproduction table for performing processing and color reproduction (R, G, B (reading color) → Y, M, C, K (recording color)). From the color reproduction table 10, a 2-bit color code and Y, M, C, K
Bit density data is output. Reference numeral 11 denotes a color ghost correction unit for performing color ghost correction, and reference numeral 12 denotes a marker color conversion circuit that detects a marker area of the document and converts the area into a marker color. 13 is an area detecting section for detecting a color marker section and extracting an area surrounded by the color marker section, 14 is a sampling section for sampling density data of the color marker section, and 15 is a section for sampling density data of the sampled color marker section. An averaging circuit for averaging 16 is a normalizing circuit for obtaining a normalization factor by normalizing the density data after averaging with the maximum value, and 17 is a black K according to a color marker area and a recording color of a printer unit 21 described later. Is a gate section for selectively passing density data (black density data). The gate section 17 allows the input black density data to pass through when the printer unit 21 is recording black K, and the black density data in a designated area when Y, M, and C are being recorded. Only let through. A multiplication circuit 18 converts the black density data into marker color data by multiplying the black density data passed through the gate unit 17 by a normalization factor. The multiplying circuit 18 performs multiplication only in a designated area, and passes black density data in other areas. Reference numeral 19 denotes an image processing unit which performs various image processing such as filtering, scaling, shading, and the like on the density signal;
Is a PWM multi-value conversion unit that multi-values a 6-bit density signal by pulse width modulation (PWM), and 21 is a printer that forms a color image by sequentially superimposing toner images of each color of Y, M, C, and K Unit.

Hereinafter, the operation will be described with reference to FIG. The document image is read by the image reading unit. That is, the image information (optical image) of the document is separated by the dichroic mirror into a red R color separation image, a green G color separation image, and a blue B color separation image.
These color separation images are supplied to CCDs 1, 2, and 3, respectively, and R,
It is converted to G and B analog signals. This analog signal is converted into digital data of a predetermined number of bits, in this example, 8 bits, by A / D converters 4, 5, and 6 for each pixel. When this A / D conversion is performed, shading correction is also performed based on the image data of the standard white plate.

The 8-bit data for each of R, G, and B that has been subjected to shading correction is supplied to density conversion units 7, 8, and 9. Density converter
In 7, 8, and 9, color balance and γ are corrected, and for each color, 8-bit data is converted into 6-bit data in accordance with human visual characteristics.

The output data of the R, G, B density conversion units 7, 8, 9 is applied to the color reproduction table 10. In the color reproduction table 10, a color code (two-bit data, for example, white: black, white, black, or chromatic) indicating whether each pixel belongs to a color area based on the density level of each of R, G, and B data. 00,
Black: 11, chromatic: 10) is created. The process of generating this color code is as follows.

 Generation of white code First, RGB is converted to XYZ coordinate system by the following formula.

Then, this XYZ coordinate system is expressed as L ^* a ^* b ^* by the following equation ^.
Convert to a uniform color space.

L ^* = 116 (Y / Yo) ^1/3 −16 a ^* = 500 [(X / Xo) ^1/3 − (Y / Yo) ^1/3 ] b ^* = 200 [(Y / Yo) ^1/3 − (Z / Zo) ^1/3 ] Here, Yo = 100 Xo = 98.07 Zo = 118.23.

In the uniform color space L ^* a ^* b ^* thus obtained,
Let L ^* ≧ 90 be the white area.

 Generation of achromatic (black) code First, Q is obtained from the R, G, B signals by the following equation.

Thus, the Q parameter is obtained, and Q ≦ 15 is set as a black area.

Generation of chromatic color code A chromatic color code is set by setting a region other than the white region and the black region as a chromatic color region.

In the white reproduction table 10, R, G, B → Y, M, and C are converted to LUT (R
This is performed using a look-up table (10a) constituted by OM, and density data of 6 bits each for Y, M, and C is created. Also, by converting the G 6-bit data from the density conversion unit 8, K density data is created without performing under color removal (UCR). The operation of the color reproduction table 10 will be described later in detail.

Thereafter, the color ghost correction unit 11 detects and removes color ghosts. This is because unnecessary color ghosts (color ghosts) are generated particularly around black characters during color separation. The color ghost correction detects whether a color ghost is present in a 1 × 7 window and converts the color code of the pixel in which the color ghost is detected into a color code of a correct color. This color ghost correction is performed in the main scanning direction and the sub scanning direction.

Then, the marker color conversion circuit 12 performs marker color conversion. The marker color conversion is a process of converting a portion of a black character of a document surrounded by a marker portion into the same color as that of the marker portion. That is, the area surrounded by the marker portion is detected, and the density data of the black characters in this area is converted to the Y,
The Y and Y of the marker part are synchronized with the timing of M, C and K image formation.
The output is normalized according to the concentrations of M, C, and K.

FIG. 2 is an explanatory diagram showing a state of marker color conversion. 2A shows an original before marker color conversion, and FIG. 2B shows an output result recorded by marker color conversion. As shown in this figure, the portion of the black character surrounded by the marker portion is formed in the same color as the color of the marker portion.
The marker color conversion will be described later in detail.

Then, the image processing unit 19 performs various image processes such as a filter process (MTF correction and smoothing process), a scaling process, and a shading process.

After that, the PWM multi-level conversion unit 20 sets the PWM
Multi-leveling is performed by (pulse width modulation), and an image is formed in the printer unit 21. This printer unit
At 21, the Y, M, C, and K toner images are sequentially superimposed on the photosensitive drum, and then transferred to transfer paper.

Next, the overall configuration and operation of a copying machine to which the image processing apparatus of the present invention is applied will be described with reference to FIG.

Here, the description will be made assuming that the development of the copying machine uses a color dry development system. In this example, two-component non-contact development and reversal development are employed. That is, the transfer drum used in the conventional color image formation is not used, and the superposition is performed on the electrophotographic photosensitive drum on which the image is formed. Also, in the following example, in order to reduce the size of the device, yellow Y, magenta M,
A description will be given of a case in which a four-color image of cyan C and black K is developed by four rotations of a drum, and the image is transferred once after the development and transferred to recording paper such as plain paper.

The document reading unit A is driven by turning on a copy button (not shown) of the operation unit of the copying machine. Then, the document 101 on the document table 128 is optically scanned by the optical system.

This optical system includes a carriage 132 provided with a light source 129 such as a halogen lamp and a reflection mirror 131, V mirrors 133 and 1
The movable mirror unit 134 includes a movable mirror unit 134.

The carriage 132 and the movable unit 134 are caused to run on the slide rail 136 at predetermined speeds and directions by a stepping motor.

Optical information (image information) obtained by irradiating the original 101 with the light source 129 is guided to the optical information conversion unit 137 via the reflection mirror 131, mirrors 133 and 133 '.

A standard white plate is provided on the back side of the left end of the platen (platen glass) 128. This is for normalizing an image signal to a white signal by optically scanning a standard white plate.

The optical information conversion unit 137 has a lens 139 and a prism 14.
0 When two dichroic mirrors 102 and 103 and a CCD 1 where a red color separation image is captured and a green color separation image are captured
It is composed of a CCD 2 and a CCD 3 for capturing a blue color separation image.

Optical signals obtained by the optical system are collected by the lens 139, and color-separated into blue optical information and yellow optical information by the dichroic mirror 102 provided in the prism 140 described above. Further, the dichroic mirror 103 separates the yellow optical information into red optical information and green optical information. Thus, the color optical image is decomposed by the prism 140 into three-color optical information of red R, green G, and blue B.

Each color separation image is formed on the light receiving surface of each CCD, so that an image signal converted into an electric signal is obtained.
After the image signal is processed by the signal processing system, the recording image signal of each color is output to the writing unit B.

As described above, the signal processing system includes an A / D converter, a color reproduction table, a color ghost correction unit, a marker unit conversion circuit,
It includes various signal processing circuits such as a WM multi-level conversion unit.

The writing section B (printer unit 21) has a deflector 141. As the deflector 141, a deflector including an optical deflector using quartz or the like may be used in addition to a galvanometer mirror, a rotating polygon mirror, or the like. The laser beam modulated by the color signal is deflected and scanned by the deflector 141.

When deflection scanning is started, beam scanning is detected by a laser beam index sensor (not shown),
Beam modulation by the first color signal (for example, a yellow signal) is started. The modulated beam is charged uniformly by the charger 154 to the image forming body (photosensitive drum)
It is made to scan over 142.

Here, the main scanning by the laser beam and the image forming body 142 are performed.
Due to the sub-scanning due to the rotation of
An electrostatic latent image corresponding to the color signal is formed.

This electrostatic latent image is developed by a developing device 14 containing yellow toner.
3 to form a yellow toner image.
Incidentally, a predetermined developing bias voltage from a high voltage source is applied to this developing device.

CPU for system control for toner supply to the developing unit
The toner replenishing means (not shown) is controlled based on a command signal from (not shown) so that toner is replenished when necessary. The above-described yellow toner image is rotated in a state where the pressure of the cleaning blade 147a is released, and an electrostatic latent image is formed based on a second color signal (for example, a magenta signal) in the same manner as in the case of the first color signal. You. Then, by using the developing device 144 that stores the magenta toner, the developing device 144 is developed to form a magenta toner image.

It goes without saying that a predetermined developing bias voltage is applied to the developing device 144 from a high-voltage power supply.

Similarly, an electrostatic latent image is formed based on the third color signal (cyan signal), and a developing device 145 containing cyan toner is formed.
As a result, a cyan toner image is formed. Further, an electrostatic latent image is formed based on the fourth color signal (black signal), and is developed by the developing device 146 filled with black toner in the same manner as the previous time.

Therefore, a multicolor toner image is formed on the image forming body 142 in an overlapping manner.

Here, the formation of a multicolor toner image of four colors has been described, but it goes without saying that a two-color or single-color toner image can be formed.

As described above, in the state where the AC and DC bias voltages are applied from the high-voltage power supply,
An example of so-called two-component non-contact development in which each toner is caused to fly toward the image forming body 142 for development has been described.

On the other hand, the recording paper P fed from the paper feeding device 148 via the feed roll 149 and the timing roll 150 is the image forming body 1
The image forming body is synchronized with the rotation of 42.
Conveyed over 142 surfaces. Then, the multicolor toner image is transferred onto the recording paper P by the transfer pole 151 to which the high voltage is applied from the high voltage power supply, and is separated by the separation pole 152.

The separated recording paper P is conveyed to the fixing device 153, where a fixing process is performed to obtain a color image.

The image forming body 142 after the transfer is cleaned by the cleaning device 147, and is prepared for the next image forming process.

In the cleaning device 147, a predetermined DC voltage is applied to the metal roll 147b in order to easily collect the toner cleaned by the cleaning blade 147a.
The metal roll 147b is arranged on the surface of the image forming body 142 in a non-contact state. After the cleaning is completed, the cleaning blade 147a is released from the pressure contact.However, at the time of release, an auxiliary roller 147c is further provided to release unnecessary toner that is left behind. By pressing, unnecessary toner is sufficiently cleaned,
Removed.

 Next, the marker color conversion will be described in detail.

First, detection of a marker area will be described. This marker detection is performed based on the marker signal. The chromatic color code generated by the above-described color reproduction table 10 is used as a marker signal. This is because the original is a black character on a white background, and the chromatic portion may be regarded as a marker portion.

FIG. 5 shows a manuscript with chromatic markers drawn on a white background (fourth
2 shows the state of the area detection by the area detection unit 13 in the case of FIG. Marker signal obtained when scanning as in FIG. 4 N is as shown in Figure 5 P _N. It is also assumed that the area signal obtained during the immediately preceding scan N-1 (not shown in FIG. 4) is Q _N-1 in FIG. Here, a logical AND signal Q _N-1 × P _N of both creates the Q from the rising edge of the _N-1 × P _N to the falling edge edge detection pulse R _N. Then, to create a logical sum signal Q _N of the marker signal P _N and the edge detection pulse R _N. This signal Q
_Let N be the area signal for the current scan line N.

Similarly, the marker signal obtained when scanning as in FIG. 4 M is as shown in Figure 5 P _M. It is also assumed that the area signal obtained during the immediately preceding scan M-1 (not shown in FIG. 4) is Q _M-1 in FIG. here,
A logical product signal Q _M-1 × P _M of both creating an edge detection pulse R _M of from a rising edge to a falling edge of the Q _M-1 × P _M. Then, to create a logical sum signal Q _M of the marker signal P _M and the edge detection pulse R _M. This signal Q _M is used as an area signal of the current scanning line M.

The area of the marker section is detected as described above, but it is necessary to sample the color data of the marker section.
In the present invention, in order to stabilize the color data, four pixels of the YMCK density data of the marker part are continuously sampled after a certain pixel (4 to 5 pixels) from the rising edge of the marker signal. That is, since the color data sampling is performed within the marker line width, the marker line width is preferably 2 mm or more. As the marker signal, 4 to 5 pixels + 4 pixels = 8 to 9
This means that only those having a run length longer than a pixel are considered as marker signals. Therefore, it is possible to prevent a color ghost in which the edge of a black character is not sufficiently corrected from being erroneously sampled as a region signal.

Sampling is performed simultaneously for four colors. As described above, since sampling is performed simultaneously for four colors, sampling accuracy is improved.

Figure 6 is an explanatory view showing the two markers and the main scanning lines l ₁ to l _7, FIG. 7 shows the area signal and the sampling points obtained in the main scanning lines l ₁ to l ₇ described above. As described above, the sampling point is located a certain pixel after the rising edge of the area signal.

The color density data of the marker section sampled in this way is averaged by the averaging circuit 15. This is to suppress variation in the color density data of the sampled four pixels.

The color density data of the marker part thus obtained is normalized. That is, based on the maximum value of Y, M, C, and K after averaging, the ratio of each of Y, M, C, and K is included as a normalization factor in the normalization circuit 16. Ask.

This normalization factor (Y ', M', C ', K') is obtained by the following equation.

Image data obtained by multiplying the black density data of the specified area (the specified area inside or outside the marker area) having passed through the gate unit 17 by the normalization factor obtained in this way by the multiplying circuit 18 and performing marker color conversion Get. That is, when printing Y, the black density data of the designated area passes through the gate unit 17. The black density data is multiplied by a multiplier 18 into a normalization factor Y '.
To obtain an image signal of the Y component included in the marker color. Similarly, image signals obtained by multiplying the normalization factors for M and C are obtained. When recording K, the black density data outside the designated area (the area other than the designated area described above) passes through the gate unit 17 and the multiplying unit 18 as they are. Then, the multiplication unit 18 multiplies the black density data of the designated area by the normalization factor K 'to obtain an image signal of the K component included in the marker color. Then, the printer unit 21 superimposes and finally transfers the toner images corresponding to the image signals in the order of Y, M, C, and K, so that the marker color is converted in the designated area, and the other areas are copied as they are. To form

As described above, in the present invention, the normalization factor is obtained by sampling the Y, M, C, and K components of the color of the marker, and the black character (black density data) in the designated area is multiplied by the normalization factor of each color component. The marker color conversion processing is performed by converting the image data into image data of each color component. Thus, full-color marker color conversion can be performed accurately and easily because of the image processing using the normalization factor.

In the above description, the case where the image processing apparatus of the present invention is applied to a copying machine has been described. However, it goes without saying that the image processing apparatus of the present invention can be used for other apparatuses for processing various color images. Nor.

(Effect of the Invention) As described in detail above, in the present invention, a normalization factor is obtained for each recording color from the maximum value of the recording color density data of the marker portion, and the normalization factor is surrounded by the marker portion. The recording color density data of the original image in the area is processed. Therefore, a full-color marker color conversion can be easily performed with a simple circuit configuration, and a color image processing apparatus capable of accurately converting black characters in a designated area to the color of a marker portion can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention, FIG. 3 is an explanatory diagram showing the state of marker color conversion, FIG. 3 is a configuration diagram showing the overall configuration of a copying machine, and FIG. FIG. 5 is an explanatory diagram showing a state of scanning of a scanning line in color conversion, FIG. 5 is a waveform diagram showing a state of generation of a marker area signal, and FIG. 6 shows a state of scanning of a scanning line in marker color conversion. FIG. 7 is a waveform diagram showing the relationship between the marker area signal and the sampling point. 1 ... R-CCD, 2 ... G-CCD 3 ... B-CCD 4,5,6 ... A / D converter 7,8,9 ... Density conversion unit 10 ... Color reproduction table 11 ... Color ghost correction unit 12 Marker color conversion circuit 13 Area detection unit 14 Sampling unit 15 Average circuit 16 Normalization circuit 17 Gate unit 18 Multiplication unit 19 Image processing unit 20 PWM multi-value conversion unit 21 Printer unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/387 H04N 1/46 H04N 1/60 G03G 15/01

Claims (1)

(57) [Claims] 1. A color image processing apparatus having a marker color conversion function for converting a portion surrounded by a marker portion of a black character of a black-and-white document into the same color as a specific color, an image reading means for reading an original image as a color separation image. And a color code generation means for generating a color code for discriminating the color separation image of the original image into achromatic and chromatic portions in pixel units; and converting the color separation image of the original image into recording color density data corresponding to the recording color. Color reproducing means for converting, marker area detecting means for detecting the area of the marker part in the original image based on the color code from the color code generating means, sampling the recording color density data of the marker part, and Marker color conversion means for converting recording color density data of an original image in an area surrounded by the marker portion into recording color density data corresponding to the color of the marker portion; A normalization factor is obtained for each recording color from the maximum value of the recording color density data of the marker section, and the recording color density data of the original image in the area surrounded by the marker section is processed by the normalization factor. A color image processing apparatus comprising: