JPH02249356A - Picture processor - Google Patents

Abstract

PURPOSE:To attain optional marker color conversion accurately by allowing a marker area detection means to detect a marker area based on a run length of a scanning line at picture read. CONSTITUTION:The processor is provided with picture read means 1-3, color code generating means 4-9 generating a color code representing to which of white/achromatic/chromatic color each picture element of read picture belongs and a marker area detection means 13 detecting an area surrounded by a color marker based on the color code from the means 4-9. Moreover, a marker color conversion processing means 12 converting a picture data in the marker area detected by the detection means 13 into a marker color is provided. The marker area detection means 13 applies area detection based on the run length of the color code, discriminates a part of the prescribed run length or over to be a marker area and the marker color conversion processing means 12 applies the marker color conversion of the picture data. Thus, an optional marker color conversion is implemented accurately.

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 divided into red R and cyan C and optically read, and based on this, the images are recorded on recording paper using an output device such as an electrophotographic copying machine. There is an image processing device that uses

Among such image processing apparatuses, some have a function of marker color conversion (a process of converting a portion of black text 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, since reading and recording are performed in three colors, red/cyan or red/blue/black, a single color of red or blue is used. There is a problem that color conversion other than the marker cannot be performed. That is, there was a problem in that the portion surrounded by red or extra-prefix markers was not converted accurately.

In addition, color images such as character drawings and photographic images can be converted into red R1 green G,
Separate blue B and read it optically, convert this into recorded colors such as yellow Y, magenta M, cyan C1 black,
Based on this, there is a color image processing device that records on recording paper using an output device such as an electrophotographic color copying machine. Such an apparatus can read and record color originals. However, such devices do not give equal consideration to full-color marker color conversion. That is, there has been no consideration given to reading various marker colors, processing for accurately converting black characters into marker colors, and the like.

Furthermore, when performing marker color conversion of an arbitrary color, there is a risk that color ghosts occurring at the edges of black characters may be mistaken for markers, and parts other than the designated area may be color converted.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to realize an image processing apparatus that can accurately perform arbitrary marker color conversion.

(Means for Solving the Problems) The present invention to solve the above problems includes an image reading means that separates and reads a document image into three colors, and each pixel of the image read by the image reading means is white/achromatic/ a color code generating means for generating a color code indicating which of the q colorings it belongs to; a marker area detecting means for detecting an area surrounded by color markers based on the color code from the color code generating means; and marker color conversion processing means for converting image data within the marker area detected by the marker area detection means into a marker color, and the marker area detection means performs area detection based on the run length of the color code. It is characterized by being configured as follows.

(Function) In the image processing apparatus of the present invention, the marker area detection means performs area detection based on the scanning line at the time of image reading. This area detection is performed using the run length of the color code as a reference, and determines a portion longer than a certain run length to be a marker area. Regarding the marker area detected in this way, the marker color conversion processing means performs marker color conversion of the image data.

(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 the block diagram of 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, and 3 is a B-CCD that converts a blue original image into an image signal. CCD, 4 is R-CC
An A/D converter that converts the red image signal read by the DI into 8-bit digital data, and 5 an A/D converter that converts the green image signal read by the G-CCD 2 into 8-bit digital data. 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 conversion section that converts red 8-bit digital data into 6-bit digital data, 8 is a density conversion section that converts green 8-bit digital data into 6-bit digital data, and 9 is a density conversion section that converts blue 8-bit digital data into 6-bit digital data. This is a density conversion unit that converts bit digital data. 10
is a color code (a 2-bit code that indicates whether each pixel is white, black, or a chromatic color, e.g., white = 00. black = 1)
1゜Chromatic color: 10) Processing 1 color reproduction (R, G, B-YM,
This is a color reproduction table for performing C, K). From this color reproduction table 10, the 2-bit color code and Y, M
, C, K 6-bit density signals are output. 11
12 is a color ghost correction unit for performing color ghost correction, and 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 the color marker portion on the document and extracts the area surrounded by the marker portion. This area detection section 13 also performs run length correction in the main scanning direction and sub-scanning direction and marker cutoff correction.

14 is a sampling unit that samples the density data of the color marker portion; 15 is an averaging circuit that averages the sampled density data of the color marker portion; and 16 is a normalization circuit that normalizes the density data after averaging by the maximum value. A normalization circuit 17 for determining a normalization 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. This gate part 1
7, when the printer unit 21 is recording black K, the data passes through the manual black as is, and Y,
When recording M and C, only black data within the marker area is passed. 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 is an image processing unit that performs various image processing such as filter processing and scaling processing on the density signal; shaded areas indicate processing; 20 is a pulse width modulation (P)
21 are Y, M, and C.

This is a printer unit that forms a color image by sequentially overlapping toner images of each color of K.

The operation will be explained below with reference to FIG. The original image is read by an image reading section. That is, the image information (optical image) of the document is separated into a red R color separated image, a green G color separated image, and a blue B color separated image by the dichroic mirror. These color separated images are supplied to ccDI, 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 standard white plate.

The shading-corrected R, G, and B 8-bit data are supplied to density converters 7, 8.9. 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 and 1, for example, white 20 〇, 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 expressed as L*a* by the following formula.
b” Convert to uniform color space.

L"-118(Y/Yo)"'-16a *-5
00[(X/Xo)"'-(Y/Yo)"']* b = 200[(Y/Yo)"'-(Z/Z
o)"'] Here, Yo -100 Xo -98,07 Zo -118,23 Te.

In the uniform color space L*a*b* obtained in this way,
Let L≧90 be a white area.

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

Q--o +G-o +-010 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
.

6-bit density data for each K is created.

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.

Part 11. Then, the marker color conversion circuit 12 performs marker color conversion. This marker color conversion is a process of converting 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, and the density data of the black characters within this area is sent to Y of the printer unit 21.
, M, C, K image formation, marker Y,
It is normalized and output according to the density of M, C, and K.

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, filter processing (MTF correction,
Various image processing such as smoothing processing), scaling processing, and hatching processing are performed.

Thereafter, the PWM multi-value conversion section 20 performs multi-value conversion using Pffi4 (pulse width modulation) to make it suitable for printing, and the printer unit 21 performs image formation. In this printer unit 21, Y and MCK toner images are sequentially superimposed on a photoreceptor drum, and then transferred onto a transfer paper.

Next, the overall construction 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 reduce the size of the apparatus, a four-color image of yellow Y, magenta M, cyan C, and black is developed on an OPC photoreceptor (drum) for image formation by four rotations of the drum. An example in which the image is transferred once after development to a 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.

And 1. The original 101 on the original table 128 is optically scanned by the optical system.

This optical system consists of a carriage equipped with a light source 129 such as a halogen lamp and a reflecting mirror 131;
It consists of 134.

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 mirrors 1.31. mirror 133,
133', it is led to an optical information conversion unit 137.

A marker dμ white plate is provided on the back side of the left end of the document table (platen glass) 128. This is because the image signal is normalized to a white signal by optically scanning the white plate.

The optical information conversion unit 137 includes a lens] 39, 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 blue color-separated image. (1η) is formed by the CCD 3 where the image is taken.

The optical signals obtained by the optical system are collected by a lens 139, and separated into blue optical information and yellow optical information by a dichroic mirror 102 installed in the prism 1.40 described above. Furthermore, dichroic mirror 1
03, 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 ghost correction section, a marker color conversion circuit, and a PWM multi-value conversion section, in addition to an A/D converter.

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 deflection scanning is started, beam scanning is detected by a laser beam index sensor (not shown), and beam modulation using a first color signal (for example, a yellow signal) is started. The modulated beam is applied to an image forming member (photoreceptor drum) 1 which is charged in a negative manner by a charger 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 a second color signal (for example, a 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, static i is determined based on the third color signal (cyan signal).
'I! A latent image is formed, and a cyan toner image is formed by a developing device 145 containing cyan toner. 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, multicolor toner images are formed on the image forming member 42 in a superimposed manner.

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. An example of jumping development is 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], 50 is placed on 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. transported. 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
is cleaned and prepared for the next imaging process.

In the cleaning device 147, a predetermined DC voltage is applied to the metal roll 147bi in order to facilitate recovery of the i-ner cleaned by the cleaning blade 147a. This metal roll 147b is the image forming body 142
placed in a non-contact manner on the surface of The cleaning blade 147a is released from the pressure bond after cleaning is completed, but
An auxiliary roller 147C is further provided in order to release unnecessary toner that is left behind at the time of release, and this auxiliary roller 147
By rotating and pressing c in the opposite direction to the image forming member 142, 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. That is, the chromatic code generated by the table 10 described above is used as a marker signal.

This is because in a normal black-on-white document, the area where the chromatic code occurs is considered to be the marker area and there is no problem.

However, in order to do this, it is necessary to sufficiently correct color ghosts that occur at the edges of black characters. If a color ghost that cannot be corrected remains, there is a possibility that the color ghost may be mistaken for a marker portion. Particularly, in a case where marker breakage correction is performed before detecting the marker area, when the image is enlarged and copied, the color ghost is also enlarged, and color conversion is performed in the vicinity of the color ghost. Therefore, in order to prevent such a situation, it is necessary to distinguish between the color ghost and the marker portion and perform marker color conversion.

FIG. 4 is a block diagram showing details of the area detection section 13. In this figure, 30 is a main scanning direction run length correction unit that corrects the run length in the main scanning direction, M1 to M8 are memories each for delaying one scanning line, and 31 is a main scanning direction run length correction unit 30 and a memory. This is a sub-scanning direction run length correction section that receives the outputs from M1 to M8 and corrects the run length in the sub-scanning direction. This sub-scanning direction run length correction section 31 has a memory M1.
.about.M8 applies the color code (of the pixels lined up in the sub-scanning direction) with a time delay corresponding to one scanning line at a time. Note that the run length refers to the length of codes when codes of the same value are consecutive. Reference numeral 32 denotes a marker breakage correction section that corrects cutoff or blurring of the marker, 33 a marker detection section that detects a marker section on a document using a color code, and 34 an area extraction section that extracts an area surrounded by the marker section. .

The color code (chromatic color: present, achromatic color or black: black, white: white) applied to this area detection unit 13 is applied in the main scanning direction or the sub-scanning direction in the order of white, presence, presence, black, black, black. If so, the run length correction unit 30 in the main scanning direction or the run length correction unit in the sub-scanning direction converts the chromatic color code into a black color code, such as white, black, black, black, black. Section 3] makes the correction. In this case, since a chromatic color exists adjacent to black, it can be determined that a color ghost remains at the edge of the black character. Furthermore, if a chromatic color exists surrounded by white, run length correction is not performed because it is considered that the marker portion is on a white background. Thereafter, the marker breakage correction section 32 performs marker breakage correction. Then, the marker portion detection section 33 detects the marker portion on the document.

This marker portion detection detects a run length longer than a certain value. For example, it is set so that when a chromatic color with a run length of 8 to 9 or more is present, it is determined as a marker portion. Then, the area extraction unit 34 extracts the area surrounded by the marker portion detected in this manner.

FIG. 5 is an explanatory diagram showing the appearance of a document in which chromatic markers are drawn on a white background, and FIG.
This shows how to detect an area. The marker signal obtained when scanning as indicated by N in Fig. 5 is shown in Fig. 6 P.
Suppose that the area signal obtained during the immediately previous scan N-1 (not shown in FIG. 5) is QN-1 in FIG. Here, the AND signal QN-IXPN of both
An edge detection pulse RN from the rising edge to the falling edge of this QN-1×PN is created. Then, a logical sum signal QN of the marker signal PN and the edge detection pulse RN is created. This signal QN is used for the current scan 1i.
It is assumed to be a 1N area signal.

Similarly, the marker signal obtained when scanning as shown in FIG. 5M becomes as shown in FIG. 6, P9. Further, it is assumed that the area signal obtained during the immediately previous scan M-1 (not shown in FIG. 5) is the area signal QM-1 in FIG. here,
Take the AND signal QM-IXPM of both, and calculate this QM-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. In the present invention, for the stability of color data, the Y of the marker is
Four pixels of M, C, and K density data are sampled consecutively. That is, since this color data sampling is performed within the marker line width, it is preferable that the marker line width is 2fflff1 or more. In addition, as a marker signal, 4 to 5 pixels +
This means that only those having a run length of 4 pixels - 8 to 9 pixels or more are regarded as marker signals.

FIG. 7 shows two markers and main scanning lines J71-g.

FIG. 8 is an explanatory diagram showing the main scanning lines 91 to 91 described above.
The area signal and sampling points obtained in g7 are shown. As explained above, the sampling point is a certain number of 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.

Using the maximum value of K as a reference, the normalization circuit 16 determines the ratio of each of Y, M, and C as a normalization factor.

This normalization factor (Y", M', C", ni) is obtained by the following formula. Multiply the black density data in the marker area that has passed through the gate section 17 by the normalization factor obtained in this way. A circuit 18 performs multiplication to obtain marker color-converted image data. That is,
When recording Y, density data within the marker area passes through the gate section 17. Multiplying unit 1 for this density data
Multiply the normalization factor Y° by 8 to obtain the Y included in the marker color.
Obtain component image signals. For M and C, image signals multiplied by normalization factors are obtained in the same way. 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 to obtain an image signal of the component included in the marker color. Then, by superimposing toner images according to the image signals in the order of Y, M, C, and finally transferring them in the printer unit 21, the marker color is converted in the marker area, and the other areas are copied as is. form.

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, and each color component is displayed on the black characters (K density data) in the marker area. Marker color conversion is performed by multiplying by a normalization factor and converting into image data of each color component.

Therefore, full color four-color conversion can be performed accurately and easily.

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 explained in detail above, in the present invention, the marker area is detected for each scanning line in the main scanning direction, and the Y, M and M colors of the marker are detected.
, C, and the black characters (K a degree data) in the marker area are multiplied by the normalization factor of each color component to convert into image data of each color component, thereby performing marker color conversion. Also, when chromatic color codes are continuous for a certain amount or more, it is detected as a marker part. 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 accurately perform arbitrary 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 area FIG. 5 is an explanatory diagram showing how scanning lines are scanned during marker color conversion. FIG. 6 is a waveform diagram showing how marker area signals are generated. FIG. 8 is an explanatory diagram showing how scanning lines are scanned during marker color conversion, and FIG. 8 is a waveform diagram showing the relationship between marker area signals and sampling points. 1...R-CCD 2...G-CCD3...
B-COD 4.5.6... A/D converter 7.8.9... Density conversion section] []... Color reproduction table] 1... Color ghost correction section] 2... Marker Color conversion circuit 13...Area detection section 15...Averaging circuit 17...One gate section...Image processing section 21...Printer unit 14...Sampling section 16...Normalization circuit 18 . . . Multiplying unit 20 . Area detection unit 34...Region extraction unit M1~
M8...Memory

Claims (1)

[Claims] Image reading means for separating and reading a document image into three colors, and each pixel of the image read by this image reading means is white/achromatic/
Color code generation means for generating a color code indicating which of the chromatic colors it belongs to; marker area detection means for detecting an area surrounded by color markers based on the color code from the color code generation means; and marker color conversion processing means for converting image data within the marker area detected by the marker area detection means into a marker color, and the marker area detection means performs area detection based on the run length of the color code. An image processing device characterized by being configured as follows.