JPH02249359A - Picture processor - Google Patents

Abstract

PURPOSE:To attain full color marker color conversion with fidelity by sampling the marker color at a position apart by a prescribed picture element from the end of the marker part detected by a marker area detection means. CONSTITUTION:Picture read means 1-3, color code generating means 4-9, a color reproducing means 10 converting a color decomposition image into a density data in response to the recording color, a marker area detection means 13 detecting the marker part of the original picture and extracting the area surrounded by the marker part based on the color code are provided in the processor. Moreover, a sampling means 14 sampling the color of the detected marker part from the density data and a marker color conversion means 12 converting the density data of the area surrounded by the marker part into the density data in response to the marker color are provided. Then the sampling means 14 samples the color of the marker part at a location apart by a prescribed picture element determined in advance from the end of the detected marker part. Thus, full color marker color conversion is implemented with fidelity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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) Color images such as character drawings and photographic images are optically read as red R and cyan C, and based on this, an output device such as an electrophotographic copying machine is used to print red, R, blue, etc. on recording paper. B, black K”9
There is an image processing device that records images.

Among such image processing apparatuses, some have a function of marker color conversion processing (processing of converting a portion of a black character in a black and white document surrounded by a marker to the same color as a specific color).

(Problem to be Solved by the Invention) When marker color conversion is performed using the above-mentioned device, reading and recording are performed in red/cyan or red/blue/black.
There is a problem in that color conversion cannot be performed for markers other than single-color red or blue markers. That is, there was a problem in that the portion surrounded by markers outside the red or blue storm was not converted accurately.

In addition, color images such as character drawings and photographic images can be converted into red R1 green G,
It is divided into blue B and optically read and converted into recording colors such as yellow Y, magenta M, cyan C1 black, etc. Based on this, it is printed on recording paper using an output device such as an electrophotographic color copying machine. There is a color image processing device that records images. Such an apparatus can read a color original and record in full color according to the color of the original. However, such devices do not give equal consideration to full-color marker color conversion.

That is, no consideration has been given to sampling various marker colors, processing for accurately converting black characters into marker colors, etc.

The present invention has been made in view of the above problems, and its purpose is to realize an image processing device that can faithfully perform full-color marker color conversion.

(Means for Solving the Problems) The present invention for solving the above problems includes an image reading means for separating a document image into three colors and reading the color separation images, and a method for reading the color separation images read by the image reading means. a color code generation means for generating a color code indicating whether each pixel belongs to white, an achromatic color, or a chromatic color, and converting the color separation image read by the image reading means into density data according to the recording color. detecting a marker portion of the document image based on a color reproduction means and a color code from the color code generation means;
marker area detection means for extracting the area surrounded by the marker part; sampling means for sampling the color of the marker part detected by the marker area detection means from the density data; and marker color conversion means for converting into density data according to the marker color,
The present invention is characterized in that the sampling means is configured to sample the color of the marker portion at a predetermined pixel distance from the edge of the marker portion detected by the area detection means.

(Function) In the image processing apparatus of the present invention, the color of the marker is sampled at a predetermined pixel distance from the end of the marker portion detected by the marker area detection means.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

First, an overview of the image processing apparatus of the present invention will be explained with reference to FIG. In this figure, 1 is an R-CCD that converts a red original image into an image signal, 2 is a G-CCD that converts a green original image into an image signal, 3 is a BCCD that converts a blue original image into an image signal, 4 is an A/D converter that converts the red image signal read by the R-CCDI into 8-bit digital data, and 5 converts the green image signal read by the G-CCD 2 into 8-bit digital data. A
The A/D converter 6 is an A/D converter that converts the blue image signal read by the B-CCD 3 into 8-bit digital data. 7 is a density converter that converts red 8-bit digital data to 6-bit digital data, 8 is a density converter that converts green 8-bit digital data to 6-bit digital data, and 9 is blue 8-bit digital data that is converted to 6-bit digital data. This is a density conversion unit that converts bit digital data. 10 is the color code (2 bits indicating whether each pixel is white/black/chromatic: T-F, %1)
4f white: (H7, black: 11. (f″v', ('2
: 10) Processing 1 color reproduction (R, G, B-Y, M,
This is a color reproduction table for performing C, K). From this color reproduction table 10, a 2-bit color code and Y are obtained.

A 6-bit density signal is output to each of M and C.

11 is a color ghost correction section for performing color ghost correction; 12 is a marker color conversion circuit that detects a marker area of a document and converts the area into a marker color. Reference numeral 13 denotes an area detection unit that detects a color marker portion on the document and extracts an area surrounded by the color marker portion;
15 is an averaging circuit that averages the sampled density data of the color marker part; 16 is a normalization circuit that normalizes the averaged density data by the maximum value; A normalization circuit 17 for determining a factor is a gate section that selectively passes black density data according to the color marker area and the recording color of a printer unit 21, which will be described later. When the printer unit 21 is recording black K, this gate section 17 inputs the input black color. ni, Y
, M, and C, only black data within the marker area is passed through. A multiplication circuit 18 converts the black data that has passed through the gate section 17 into marker color data by multiplying the black data by a normalization factor. Note that this multiplication circuit 18 performs multiplication only within the marker area, and passes black data in other areas. 19
20 is an image processing unit that performs various image processing such as filter processing and scaling processing on the density signal; shaded areas are processing; 20 is a pulse width modulation unit (
PWM) that multivalues a 6-bit density signal using
The multi-value conversion section 21 is a printer unit that forms a color image by sequentially overlapping toner images of each color of Y, M, C, and K.

The operation will be explained below with reference to FIG. The original image is read by an image reading section. In other words, the image information of the manuscript? ! !
(Optical image) is separated into a red R color-separated image, a green G color-separated image, and a blue B color-separated image by a dichroic mirror.

These color separated images are supplied to C0Di, 2.3 and converted into RGB analog signals, respectively. This analog signal is converted into digital data of a predetermined number of bits, 8 bits in this example, 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 imaging data of the reference white plate.

The shading-corrected RGB 8-bit data is supplied to the density conversion section. Density converter 7.8.
In step 9, color balance and γ correction are performed, and 8-bit data is converted to 6-bit data for each color.

Then, the output data of the RGB density converters 7, 8.9 is applied to the color reproduction table 10. In this color reproduction table 10, a color code (2-bit data, e.g. white: OO , black: 11, chromatic color: 10) are created. The process of generating this color code is as follows.

■Generation of white code First, RGB is converted to the xYZ coordinate system using the following formula.

Then, this XYZ coordinate system is defined as “CL” by the following formula.
a b Convert to uniform color space.

L"-118(Y/Yo)"'-16a *-
500((X/Xo)"'-(Y/Yo)"3]b
*-200 [(Y/Yo)"'-(Z/Zo)"'
] Here, Yo embroidery 100 Xo -98,07 Zo -118,23.

In the uniform color space L"a*b'" obtained in this manner, L≧90 is defined as a white region.

■Generation of achromatic (black) code First, Q is determined from the RGB signals using the following formula.

Q--o +G-o +-o
l.

In this way, the Q parameter is determined, and Q≦゛15 is defined as a black region.

■Generation of chromatic color code A chromatic color code is set by treating the area other than the white area and black area as a chromatic color area.

In addition, in the color reproduction table 10, R, G, B→Y, M
, C, and K using a lookup table (a lookup table composed of ROM), and 6 each for YMCK.
Creating bit density data.

Thereafter, the color ghost correction section 11 detects and removes color ghosts. This is because unnecessary color ghosts (color ghosts) occur especially around black characters during color separation. Color ghost correction is performed by detecting whether or not a color ghost is present using a 1×7 window, and converting the color code of a pixel in which a color ghost has been detected into the color code of the 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. This marker color conversion is a process of converting the color of the portion of the black text on the document surrounded by the marker to 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 applied to the Y, M of the marker in accordance with the Y, M, C, K image formation of the printer unit 21. , C, is normalized and output according to the density of .

FIG. 2 is an explanatory diagram showing the state of marker color conversion. Of these figures, FIG. 2A shows the document before marker color conversion, and FIG. 2B shows the output result recorded by marker color conversion. As shown in this figure, the part of the black character surrounded by the color marker is formed in the same color as the marker. still,
This marker color conversion will be explained in detail later.

Then, the image processing unit 19 performs filter processing (MTF correction,
Various image processing such as smoothing processing), scaling processing, and hatching processing are performed.

Thereafter, the PWM multi-value converter 20 performs multi-value conversion using PWM (pulse width modulation) to make it suitable for printing, and the printer unit 21 performs image formation. In this printer unit 21, Y, M.

The C and K toner images are sequentially superimposed on the photoreceptor drum,
After this, it is 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 explained with reference to FIG.

Here, the description will be made assuming that the copying machine uses a color dry development method. In this example, two-component non-contact development and reversal development are employed. In other words, the transfer drum used in conventional color image formation is not used, and the images are superimposed on the electrophotographic photosensitive drum that forms the image. In addition, in the following example, in order to downsize the device, four-color images of yellow Y, magenta M, cyan C, and black are developed on the OPC photoreceptor (drum) for image formation by four rotations of the drum. , a method in which transfer is performed once after development and is transferred onto recording paper such as plain paper will be described.

The document reading section A is driven by turning on a copy button (not shown) on the operation section of the copying machine.

The original 101 on the original table 128 is then optically scanned by the optical system.

This optical system includes a carriage 132 provided with a light source 129 such as a halogen lamp, a reflecting mirror 131, and a movable mirror unit 1 provided with mirrors 133 and 133'.
Consists of 34.

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

Optical information (image information) obtained by irradiating the original 101 with the light source 129 is transmitted to the reflecting mirror 131 and the mirror 133.1.
33' to an optical information conversion unit 137.

A standard white plate is provided on the back side of the left end of the platen glass 128. This is because the image signal is normalized to a white signal by optically scanning the standard white plate.

The optical information conversion unit 137 includes a lens 139, a prism 140, two dichroic mirrors 102 and 103, a CCD 1 for capturing a red color-separated image, a CCD 2 for capturing a green color-separated image, and a CCD 2 for capturing a blue color-separated image. It is composed of a CCD 3 that is imaged.

The optical signal obtained by the optical system is collected by the lens 139, and separated into blue optical information and yellow optical information by the dichroic mirror 102 provided in the prism 140 described above. Furthermore, dichroic mirror 103
The yellow optical information is color-separated into red optical information and green optical information.

In this way, the color optical image is decomposed by the prism 140 into three-color optical information of red, R, green, and blue.

Each color separation image is formed on the light receiving surface of each CCD, thereby obtaining an image signal converted into an electrical signal.

After the image signal is processed by a signal processing system, recording image signals of each color are output to the writing section B.

As will be described later, the signal processing system includes various signal processing circuits such as an A/D converter, a color reproduction table, a color ghost correction section, a marker color conversion circuit, and a PWM multi-value conversion section.

The writing section B (printer unit 21) has a deflector 141. As this deflector 141, in addition to a galvanometer mirror, a rotating polygon mirror, or the like, a deflector made of an optical deflector using crystal or the like may be used.

The laser beam modulated by the color signal passes through this deflector 14.
1 for deflection scanning.

When the deflection scan is started, the beam scan is detected by a laser beam index sensor (not shown) and beam modulation with a first color signal (e.g. yellow signal) is started.6 The modulated beam is charged An image forming member (photosensitive drum) 1 to which a negative charge is applied by a container 154
42 is scanned.

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

This electrostatic latent image is transferred to a developing device 14 containing yellow toner.
3 to form a yellow toner image.

Note that a predetermined developing bias voltage from a high voltage source is applied to this developing device.

Toner replenishment for the developing unit is done by the CPU for system control.
A toner replenishing means (not shown) is controlled based on a command signal from a toner replenishing means (not shown), so that toner is replenished when necessary. The yellow toner image described above is rotated with the cleaning blade 147a released from pressure, and an electrostatic latent image is formed based on the second color signal (for example, the magenta signal) in the same manner as in the case of the first color signal. Ru.

Then, by using a developing device 144 containing magenta toner, this is developed to form a magenta toner image.

Needless to say, 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 provided.
A cyan toner image is formed. Further, an electrostatic latent image is formed based on the fourth color signal (black signal), and is developed in the same manner as the previous time using the developing device 146 filled with black toner.

Therefore,. This means that multicolor toner images are superimposed on the image forming body 142.

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

As described above, the development process is a so-called non-contact two-component development process in which each toner is ejected toward the image forming body 142 while AC and DC bias voltages from a high-voltage power source are applied. Showing I-■ of jumping development.

On the other hand, 1. The recording paper P fed is conveyed onto the surface of the image forming body 142 in a state in which the timing is synchronized with the rotation of the image forming body 142. Then, by the transfer pole 151 to which a high voltage is applied from the high voltage power source,
The multicolor toner image is transferred onto the recording paper P, and the separation pole 15
separated by 2.

The separated recording paper P is conveyed to the fixing device 153, where it undergoes a fixing process and a color image is obtained.

The image forming body 142 after the transfer is transferred to a cleaning device 147
It is cleaned and visible for the next imaging process.

In the cleaning device 147, a predetermined DC voltage is applied to the metal roll 147b in order to facilitate recovery of the toner cleaned by the cleaning blade 147a. This metal roll 147b is placed on the surface of the image forming body 1420 in a non-contact state. cleaning blade 1
47a is released from pressure bonding after cleaning is completed, but in order to release unnecessary toner that is left behind at the time of release, an auxiliary roller 147C is further provided, and this auxiliary roller 147c is rotated in the opposite direction to the image forming body 142 and is pressed against the image forming member 142. As a result, unnecessary toner is sufficiently cleaned and removed.

Next, marker color conversion, which is the main part of the present invention, will be explained in detail.

First, detection of a marker area will be explained. This marker detection is performed based on the marker signal. The chromatic color code generated by the color reproduction table 10 described above is used as a marker signal.

FIG. 5 shows how the area detection unit 13 detects an area in the case of a document (shown in FIG. 4) in which chromatic markers are drawn on a white background. In this figure, the marker signal obtained when scanning as indicated by N is as shown in FIG. 5 PH. Also,
Assume that the area signal obtained during the immediately previous scan N-1 (not shown in FIG. 4) is QN-1 in FIG. Here, the AND signal QN-IXPN of both is taken, and this QN
-I Create an edge detection pulse RN from the rising edge of XPN to the falling edge. Then, a logical sum signal QN of the marker signal PN and the edge detection pulse RN
Create. This signal QN is defined as the area signal of the current scanning line N.

Similarly, the marker signal obtained when scanning as shown in FIG. 4M becomes as shown in FIG. 5PM. Further, it is assumed that the area signal obtained during the immediately previous scan M-1 (not shown in FIG. 4) is the area signal QM-1 in FIG. here,
Take the AND signal QM-IXPM of both, and calculate this QI-I
An edge detection pulse RM from the rising edge to the falling edge of XPM is created. Then, a logical sum signal QM of the marker signal PM and the edge detection pulse RM is created. This signal QM is defined as the area signal of the current scanning line M.

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

Figure 6 shows the vicinity of the blue fluorescent marker on a white original (Figure 6 b-d)
) is an explanatory diagram showing the results of actual measurement of R, G, and 88 degrees. Furthermore, FIG. 7 is an explanatory diagram showing the results of actually measuring the RlG and B concentrations near the orange fluorescent marker (FIG. 7b-d) on a white original. In these figures,
It can be seen that the chromatic color areas b to d, which are marker areas, are not suitable for sampling because the color of the marker is light at the edge of the area. However, from a position 4 to 5 pixels away from the edge, the density is almost the same as that at the center. Although the R2G and B densities have been explained in FIGS. 6 and 7, the density characteristics of Y, M, and C also exhibit similar characteristics.

Therefore, in the present invention, in order to stabilize the color data, Y, M, C, K density data of the marker is continuously sampled for 4 pixels from a fixed number of pixels (4 to 5 pixels) after the rising edge of the marker signal. . In other words, this color data sampling is performed within the marker line width, so if the marker line width is 2
01111 or more is preferable. Furthermore, 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.

For this reason, it is possible to prevent erroneous sampling of color ghosts that have not been sufficiently corrected at the edges of black characters as area signals.

FIG. 8 is an explanatory diagram showing two markers and main scanning lines g1 to g7, and FIG. 9 shows area signals and sampling start points obtained from the above-mentioned main scanning lines g and g1. As described above, the sampling start point is a certain number of pixels (4 to 5 pixels) after the rising edge of the area signal.

The marker color density data sampled in this manner is averaged by an averaging circuit 15. This is to suppress variations in the color density data of the four sampled pixels.

The color density data of the marker thus obtained is normalized. That is, Y, M, and C after averaging.

The normalization circuit 1 calculates the ratio of each of Y, M, C, and K based on the maximum value of .
6 as a normalization factor.

This normalization factor (Y", M', C', Ni') is determined by the following formula.

The black density data in the marker area that has passed through the gate section 17 is multiplied by the normalization factor obtained in this manner in a multiplication circuit 18 to obtain marker color-converted image data. That is,
When recording Y, the Ka degree data in the marker area passes through the gate section 17. This K1 degree data is multiplied by the multiplier 1.
Multiply the normalization factor Y by 8 to obtain Y included in the marker color.
Obtain component image signals. Similarly, for M and C, image signals multiplied by the normalization factor are obtained. When recording K, the density data outside the marker area passes through the gate section 17 and the multiplication section 18 as is. Then, the multiplier 18 multiplies the data in the marker area by the normalization factor K" to obtain the image signal of the component included in the marker color. Then, the printer unit 21 multiplies the data of Y, M, C, K. By sequentially superimposing toner images according to image signals and finally transferring them, a marker color is converted in the marker area, and a copied image is formed as is in other areas.

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 sampled at a certain distance from the edge of the marker, and the black characters in the marker area are detected. Marker color conversion is performed by multiplying (Ka degree data) by the normalization factor of each color component by 1- to convert it into image data of each color component. Therefore, full-color marker color conversion can be performed accurately and easily. In particular, since the sampling position is located away from the edge of the marker, the color of the marker can be sampled accurately, and the converted colors are also faithful to the original.

In the above description, the present invention was applied to a copying machine, but it goes without saying that the image processing apparatus of the present invention can be used in various other devices that process color images.

(Effects of the Invention) As described above in detail [7], the present invention detects the marker area for each scanning line in the main scanning direction, and
17 to perform marker color conversion by sampling components M, C, and multiplying the black characters (Ka degree data) in the marker area by the normalization factor of each color component and converting it to image data of each color component. . Therefore, black characters within the marker area can be accurately converted to the color of the marker. Therefore, it is possible to realize an image processing device that can faithfully perform full-color marker color conversion.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the structure of an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the state of marker color conversion, Fig. 3 is a block diagram showing the overall structure of the copying machine, and Fig. 4 is a block diagram showing the marker color conversion. An explanatory diagram showing how scanning lines are scanned during color conversion, Fig. 5 is a waveform diagram showing how a marker area signal is generated, Fig. 6 is an explanatory diagram showing the density characteristics of a blue fluorescent marker, and Fig. 7. Figure 8 is an explanatory diagram showing the density characteristics of the orange fluorescent marker, Figure 8 is an explanatory diagram showing how scanning lines are scanned during marker color conversion, and Figure 9 is a waveform showing the relationship between the marker area signal and the sampling point. It is a diagram. 1,...R-CCD 2...G-CCD3・
... B-CCD 4.5.6 ... A/D converter 7.8.9 ... Density conversion section IQ ... Color reproduction table 11 ... Color ghost correction section 12 ... Marker color Conversion circuit 13...area detection section 1
4... Sampling section 15... Average circuit 16.
...Normalization circuit 17...Gate section 18...
- Multiplication section 19... Image processing section 20...
PWM multilevel converter 21...printer unit

Claims (1)

[Claims] Image reading means for separating a document image into three colors and reading it as a color-separated image; Each pixel of the color-separated image read by the image reading means belongs to white, achromatic color, or chromatic color. a color code generating means for generating a color code indicating the color of the image; a color reproduction means for converting the color separation image read by the image reading means into density data corresponding to the recorded color; and a color code from the color code generating means. a marker area detection means for detecting a marker part of a document image based on the image and extracting an area surrounded by the marker part, and a sampling means for sampling the color of the marker part detected by the marker area detection means from the density data. and marker color conversion means for converting the density data of the area surrounded by the marker part into density data according to the marker color, and the marker color converting means converts the density data of the area surrounded by the marker part into density data according to the marker color, The image processing device is characterized in that the sampling means is configured to sample the color of the marker portion at a position a predetermined pixel apart.