JP2883095B2 - 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 into red R and cyan C, and based on this, a red R and blue are printed on recording paper using an output device of an electrophotographic copying machine. There is a color image processing apparatus for recording in 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 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 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.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a color image processing apparatus capable of accurately sampling marker colors and faithfully performing full-color marker color conversion. Is to make it happen.

(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 color-separating an original image and reading it as a color-separated image, and a color code indicating whether each pixel of the color-separated image read by the image reading means belongs to white / achromatic / chromatic colors A color code generating means for generating color data, a color reproducing means for converting the color separation image read by the image reading means into density data corresponding to a recording color, and an original based on the color code from the color code generating means. Marker area detecting means for detecting an area of a marker portion in an image, sampling means for sampling recording color density data of the marker portion, and an original image in an area surrounded by the marker portion And a marker color conversion means for converting the recording color density data into the recording color density data corresponding to the color of the marker section. The sampling means simultaneously samples the recording color density data corresponding to the color of the marker section. And sampling is performed after a predetermined number of pixels from the rising edge of the marker portion detected by the marker area detecting means.

(Operation) In the color image processing apparatus of the present invention, the sampling means simultaneously samples the recording color density data corresponding to the color of the marker part, and after a certain pixel from the rising edge of the marker part detected by the marker area detecting means. Sampling from

(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 (reading color) → Y, M, C, K (recording color)). From the color reproduction table 10, a 2-bit color code and Y, M, C, K
A bit density signal 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 on the document and extracting an area surrounded by the color marker section, 14 is a sampling section for sampling recording color density data of the color marker section, and 15 is a sampled color marker. An averaging circuit for averaging the density data of the parts, 16 is a normalization circuit for obtaining a normalization factor by normalizing the averaged density data with a maximum value, 17 is a color marker area and a printer unit 21 described later. A gate section for selectively passing black density data of black K in accordance with a recording color. The gate unit 17 allows the input black density data to pass as it is when the printer unit 21 is recording black K, and only the black density data in the marker area when recording Y, M, and C. 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 multiplication circuit 18 performs multiplication only in the marker area, and passes black density data in other areas. Reference numeral 19 denotes an image processing unit which performs various types of image processing such as filtering, scaling, and shading on the density signal
Reference numeral 20 denotes a PWM multi-level conversion unit that multi-values a 6-bit density signal by pulse width modulation (PWM), and 21 forms a color image by sequentially superimposing toner images of each color of Y, M, C, and K. It is a printer 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 into a red R color separation image, a green G color separation image, and a blue B color separation image by a dichroic mirror (not shown). These color separation images are supplied to CCD1,2,3,
The signals are converted into R, G, and B analog signals, respectively. 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 reference white plate.

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

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

Generation of white code First, R, G, and B are converted to the XYZ coordinate system by the following formula.

Then, the XYZ coordinate system is converted into the L ^* a ^* b ^* uniform color space by the following equation.

L ^* = 116 (Y / Yo) ^1/3 −16 a ^* = 500 [(X / Yo) ^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 ^* ≧
Let 90 be a white area.

Generation of achromatic (black) code First, calculate Q from the RGB signal using the following formula The parameters are obtained in this manner, and Q ≦ 15 is defined 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 color reproduction table 10, R, G, B → Y, M, C, K
(Look-up table composed of ROM) to create 6-bit density data for each of Y, M, C, and K.

Thereafter, the color ghost correction unit 11 detects and removes color ghosts. This is because unnecessary ghosts of a chromatic color (color ghosts) are generated particularly around black characters during color separation. 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. Then, the 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 portion of the black characters of the document into the same color as the marker portion. That is, the area surrounded by the marker part is detected,
The color of the marker part is sampled, and the density data of black characters in this area is normalized according to the Y, M, C, and K densities of the marker part in accordance with the Y, M, C, and K image formation of the printer unit 21. And output it.

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 reference 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 the reference 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.

By forming each color separation image on the light receiving surface of each CCD, 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, in addition to a galvanometer mirror, a rotating polygon mirror, or the like, a deflector made of an optical deflector using quartz or the like may be used. 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) 142 to which uniform charging is given by a charger 154.
It 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, as described above, so-called non-contact two-component jumping is performed in which each toner flies toward the image forming body 142 and is developed in a state where an AC and DC bias voltage from a high-voltage power supply is applied. An example of development was shown.

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 to obtain a color image on which a fixing process has been performed.

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

FIG. 6 shows a blue fluorescent marker area of a white background document (FIGS.
It is explanatory drawing which shows the measurement result which measured R, G, and B density | concentration of d) vicinity. FIG. 7 is an explanatory diagram showing the measurement results of the actual measurement of the R, G, and B densities in the vicinity of the orange fluorescent marker area (FIGS. 7b to 7d) of the 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, density data of Y, M, C, and K of the marker portion are simultaneously sampled continuously for four pixels. That is, since this color data sampling is performed within the marker line width, the marker line width is 2 m.
m or more is preferable. Also, the marker signal is 4 to 5
Pixels + 4 pixels = Only those having a run length of 8 to 9 pixels or more are regarded as marker signals. For this reason,
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.

At this time, the sampling unit 14 simultaneously samples 6-bit density data of each of Y, M, C, and K at a fixed pixel (for example, 4 pixels). As described above, by simultaneously performing sampling for each color, the color of the marker portion can be accurately read. Therefore, marker color conversion can be performed accurately.

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.

Next, the color density data of the marker portion obtained in this way is normalized. That is, based on the maximum value of Y, M, C, K after averaging, the normalization circuit 16 determines what ratio each of Y, M, C, K is included as a normalization factor. .

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 black density data in the marker area passes through the gate unit 17. The black density data is multiplied by a normalization factor Y 'in a multiplication unit 18 to obtain an image signal of a 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 marker area passes through the gate unit 17 and the multiplying unit 18 as they are. Then, the multiplication unit 18 multiplies the black density data in the marker 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 marker area, and the other areas are copied as they are. To form

As described above, the marker area is detected for each scanning line in the main scanning direction, and the Y, M, C, and K components of the marker color are simultaneously sampled at a certain distance from the marker end, and the marker area is detected. Marker color conversion is performed by multiplying a black character (black density data) by a 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.

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.

(Effects of the Invention) As described above in detail, the present invention relates to 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 document into the same color as a specific color. Image reading means for reading a document image as a color separation image by color separation, and a color code indicating whether each pixel of the color separation image read by the image reading means belongs to white / achromatic / chromatic colors. A color code generating means for generating, a color reproducing means for converting a color separation image read by the image reading means into density data corresponding to a recording color, and a color code in the original image based on the color code from the color code generating means. Marker area detecting means for detecting the area of the marker section; sampling means for sampling the recording color density data of the marker section; and recording color density data of the original image in the area surrounded by the marker section. Marker color conversion means for converting the data into recording color density data corresponding to the color of the marker section. And
The sampling means is configured to simultaneously sample recording color density data corresponding to the color of the marker portion,
In addition, this sampling is configured to be started after a predetermined pixel from the rising edge of the marker section detected by the marker area detecting means.

Although the color of the marker is often light at the end of the area of the marker, in the present invention, the recording color density data of the marker is sampled after a certain pixel from the rising edge of the marker. You can sample accurately. Therefore, the portion surrounded by the marker section can be accurately converted to the color of the marker section. Therefore, it is possible to realize a color 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 a state of scanning at the time of color conversion, FIG. 5 is a waveform diagram showing a state of generation of a marker area signal, FIG. 6 is an explanatory diagram showing a density characteristic of a blue fluorescent marker, and FIG. FIG. 8 is an explanatory diagram showing the density characteristics of the marker, FIG. 8 is an explanatory diagram showing a state of scanning of a scanning line at the time of marker color conversion, and FIG. 9 is a waveform diagram showing a relationship between a marker area signal and a sampling point. DESCRIPTION OF SYMBOLS 1 ... R-CCD, 2 ... G-CCD 3 ... B-CCD 4,5,6 ... A / D converter 7,8,9 ... Density conversion part 10 ... Color reproduction table 11 ... Color ghost correction part 12 ... Marker Color conversion circuit 13 ... Area detection unit 14 ... Sampling unit 15 ... Averaging 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) Fields surveyed (Int. Cl. ⁶ , DB name) H04N 1/387 H04N 1/60 H04N 1/46 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 black characters of a black and white original into the same color as a specific color. Image reading means for reading; color code generating means for generating a color code indicating whether each pixel of the color separation image read by the image reading means belongs to white / achromatic / chromatic colors; and the image reading means A color reproduction means for converting the color separation image read in step (a) into density data corresponding to a recording color; and a marker area detection for detecting an area of a marker portion in the original image based on the color code from the color code generation means. Means for sampling the recording color density data of the marker section; and recording color density data of the original image in the area surrounded by the marker section according to the color of the marker section. Marker color conversion means for converting into recording color density data, wherein the sampling means is configured to simultaneously sample recording color density data corresponding to the color of the marker portion, and is detected by the marker area detecting means. A color image processing apparatus characterized in that sampling is performed after a predetermined number of pixels from a rising edge of the selected marker section.