JP2817940B2 - Image processing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image processing apparatus, and more particularly, to a color image processing apparatus suitable for marker color conversion processing.

(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 this, an output device such as an electrophotographic copier is used to print red R, There is an image processing apparatus for recording in blue B and black K.

Some of such image processing apparatuses have a function of a marker color conversion process (a process of converting a portion surrounded by a marker among black characters of a black-and-white document 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 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.
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 a color original and record in full color according to the color of the original. However, in such an apparatus, no consideration has been given to performing full-color marker color conversion. That is, there has been no consideration with respect to sampling of various marker colors, processing for accurately converting black characters into marker colors, and the like.

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 an image processing device capable of faithfully performing full-color marker color conversion.

(Means for Solving the Problems) The present invention for solving the above-described problems includes an image reading unit that separates an original image into three colors and reads the image as a color separation image, and each pixel of the color separation image read by the image reading unit. Color code generation means for generating a color code indicating whether the color belongs to white / achromatic / chromatic colors, and color reproduction for converting a color separation image read by the image reading means into density data according to a recording color Means, while detecting a marker portion of the original image based on the color code from the color code generation means,
Marker area detecting means for extracting the area surrounded by the marker section; sampling means for sampling the color of the marker section detected by the marker area detecting section from the density data; and density data of the area surrounded by the marker section. Marker color conversion means for converting into density data corresponding to the marker color, wherein the sampling means detects the marker part at a position which is separated from the end of the marker part detected by the area detection means by a predetermined pixel. It is characterized in that it is configured to sample a color.

(Operation) In the image processing apparatus of the present invention, sampling of the color of the marker is performed at a predetermined pixel away from the end of the marker portion detected by the marker area detecting means.

(Example) Hereinafter, an example 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 → Y, M, C, K). The color reproduction table 10 outputs a 2-bit color code and a 6-bit density signal for each of Y, M, C, and K. 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 on the document 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 sampling section for the color marker section. An averaging circuit for averaging the density data, 16 is a normalization circuit for obtaining a normalization factor by normalizing the averaged density data with the maximum value, 17 is a color marker area and a printer unit to be described later.
A gate section for selectively passing density data of black K in accordance with 21 recording colors. The gate unit 17 allows the input black K data to pass as it is when the printer unit 21 is recording black K, and transmits only the black data in the marker area when recording Y, M, and C. Let it pass. 18
Is a multiplication circuit for converting the black data into marker color data by multiplying the black data passing through the gate unit 17 by a normalization factor. The multiplying circuit 18 performs multiplication only in the marker area, and passes black 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 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,
Converted to B analog signal. This analog signal is 1
A / D converters 4, 5, and 6 convert the digital data into digital data of a predetermined number of bits, in this example, 8 bits for each pixel. this
When A / D conversion is performed, shading correction is also performed based on image data of the reference white plate.

The RGB 8-bit data that has been subjected to shading correction is supplied to the density conversion unit. In the density converters 7, 8, and 9, color balance and γ are corrected, and 8-bit data is converted into 6-bit data for each color.

The output data of the RGB density converters 7, 8, and 9 are applied to the color reproduction table 10. In this color reproduction table 10,
A color code (two-bit data, for example, white: 00, black: 11, chromatic color) indicating whether each pixel belongs to a color area of white / black / chromatic color according to the level of each data of R, G, B : 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 ^* by the following equation ^.
b ^* Convert to 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, L ^* ≧ 90 is defined as a white region.

Generation of achromatic (black) code First, Q is obtained from the RGB signal 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.

Further, in the color reproduction table 10, R, G, B → Y, M, C, and K are performed by a look-up table (look-up table composed of a ROM), and density data of 6 bits for each of YMCK is created. .

Thereafter, the color ghost correction unit 11 detects and removes color ghosts. This is because ghosts (color ghosts) of unnecessary colors occur at the time of color separation, especially around black characters. The color ghost correction is performed by detecting whether or not a color ghost is present in a 1 × 7 window and converting 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 the color of a portion surrounded by the marker among the black characters of the document into the same color as the marker. That is, the area surrounded by the marker is detected, the color of the marker is sampled, and the density data of the black characters in this area is converted to the Y, M, C, and K of the marker in accordance with the Y, M, C, and K image formation of the printer unit 21. , C, and K are normalized and output.

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 color marker is formed in the same color as the color of the marker.
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 surface of the left end of the 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, two dichroic mirrors 102 and 103 and a CCD 1 for capturing a red color separation image, and a CC for capturing a green color separation image
It is composed of D2 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.

The signal processing system includes various signal processing circuits such as a color reproduction table, a color ghost correction unit, a marker color conversion circuit, and a PWM multi-value conversion unit, in addition to an A / D converter, as described later.

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 applied to an image forming body (photosensitive drum) 14 to which uniform charging is given by a charger 154.
2 is made to scan over.

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 non-contact two-component jumping 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, and the auxiliary roller 147c is rotated in a direction opposite to the image forming body 142, By pressing, unnecessary toner is sufficiently cleaned,
Removed.

Next, the marker color conversion which is a main part of the present invention 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.

FIG. 5 shows a manuscript with chromatic markers drawn on a white background (fourth
(Shown in the figure) shows a state of the area detection of the area detection unit 13. In this figure, the marker signal obtained when scanning is performed like _N is as shown in FIG. It is also assumed that the area signal obtained during the immediately preceding scan N-1 (not shown in FIG. 4) is QN _-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. The signal Q _N and domain signal of 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 QM _-1 in FIG. Here, a logical product signal Q _M-1 × P _M of both edge detection pulse from a rising edge to a falling edge of the Q _M-1 × P _M
To create a R _M. Then, to create a logical sum signal Q _M of the marker signal P _M and the edge detection pulse R _M. The signal Q _M and region signal of the current scan line M.

The marker area is detected as described above, but it is necessary to sample the color data of the marker.

FIG. 6 shows the vicinity of a blue fluorescent marker on a white background document (FIGS.
It is explanatory drawing which shows the measurement result which measured R, G, B density of d) actually. FIG. 7 is an explanatory diagram showing the measurement results obtained by actually measuring the R, G, and B densities in the vicinity of the orange fluorescent marker (FIGS. 7b to 7d) on a white background document. In these figures, it can be seen that, in the chromatic color regions b to d, which are marker regions, the marker is not suitable for sampling because the color of the marker is light at the end of the region. However, from a position 4 to 5 pixels away from the edge, the density is almost the same as the density at the center. 6 and 7, the R, G, and B concentrations are shown and described, but the Y, M, C, and K concentration characteristics show similar characteristics.

Therefore, in the present invention, in order to stabilize the color data, a fixed pixel (4 to 5 pixels) is set from the rising edge of the marker signal.
Thereafter, the Y, M, C, K density data of the marker is sampled continuously for four pixels. That is, since the color data sampling is performed within the marker line width, the marker line width is preferably 2 mm or more. In addition, only marker signals having a run length of 4 to 5 pixels + 4 pixels = 8 to 9 pixels or more are regarded 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.

FIG. 8 is an explanatory diagram showing two markers and main scanning lines l _{1 to} l ₇ , and FIG. 9 shows an area signal obtained at the above-described main scanning lines l _{1 to} l ₇ and a sampling start point. . As described above, the sampling start point is a fixed pixel (4 to 5 pixels) from the rising edge of the area signal.
After.

The color density data of the marker 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 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.

The multiplication circuit 18 multiplies the normalization factor thus obtained by the multiplying circuit 18 with the black density data in the marker area that has passed through the gate unit 17, thereby obtaining marker color-converted image data. That is, Y
Is recorded, the K density data in the marker area passes through the gate section 17. The K density data is multiplied by a normalization factor Y 'in a multiplication unit 18 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 K density data outside the marker area passes through the gate unit 17 and the multiplication unit 18 as they are. Then, a multiplication unit is added to the K data in the marker area.
Multiplying the normalization factor K 'by 18 to obtain K included in the marker color
Obtain the image signal of the component. And in the printer unit 21
By superimposing and finally transferring the toner image corresponding to the image signal in the order of Y, M, C, K, the marker color is converted in the marker area,
The other areas form the copied image as it is.

As described above, the marker area is detected for each scanning line in the main scanning direction, the Y, M, C, and K components of the marker color are sampled at a certain distance from the end of the marker, and the black characters in the marker area are sampled. The marker color conversion is performed by multiplying the (K density data) by the normalization factor of each color component and converting it to image data of each color component. Therefore, full-color marker color conversion can be performed accurately and easily. Especially,
Since the sampling position is located farther from the end of the marker, the sampling of the marker color is accurate, and the converted color is faithful to the document.

In the above description, the case where 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.

(Effect of the Invention) As described in detail above, in the present invention, a marker area is detected for each scanning line in the main scanning direction, and the Y, M,
The C and K components are sampled, and black characters (K
The density data) is multiplied by the normalization factor of each color component to convert the data into image data of each color component, thereby performing marker color conversion. Therefore, black characters in the marker area can be accurately converted to the marker color. Therefore, it is possible to realize an image processing apparatus capable of faithfully performing full-color marker color conversion.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention, FIG. 2 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 how scanning lines are scanned during color conversion, FIG. 5 is a waveform diagram showing how marker region signals are generated, FIG. 6 is an explanatory diagram showing density characteristics of a blue fluorescent marker, and FIG. FIG. 8 is an explanatory diagram showing the density characteristics of an orange fluorescent marker, FIG. 8 is an explanatory diagram showing the scanning line scanning during marker color conversion, and FIG. 9 is a waveform diagram showing the relationship between the marker area signal and the sampling points. is there. 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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ identification code FIG06F 15/64 340B (58) Investigated field (Int.Cl. ⁶ , DB name) H04N 1/387 H04N 1/46 H04N 1 / 60 G06T 2/00 G03G 15/01

Claims (1)

(57) [Claims] An image reading means for separating a document image into three colors and reading it as a color separation image, and determining whether each pixel of the color separation image read by the image reading means belongs to white / achromatic / chromatic colors. A color code generation unit that generates a color code indicating the following: a color reproduction unit that converts a color separation image read by the image reading unit into density data corresponding to a recording color; and a color code from the color code generation unit. Marker area detecting means for detecting a marker part of a document image based on a reference and extracting an area surrounded by the marker part, and sampling means for sampling the color of the marker part detected by the marker area detecting means from density data And marker color conversion means for converting the density data of the area surrounded by the marker part into density data corresponding to the marker color. Wherein at a position apart a predetermined given pixel from the end of the month portion sampling unit image processing apparatus characterized by being configured to sample the color of the marker portion.