JPH02249354A - Picture processor - Google Patents

Abstract

PURPOSE:To attain conversion of marker color in full color by sampling each component of the marker color at a position of a density peak level in a marker area and applying marker color conversion based on the density data. CONSTITUTION:Picture read means 1-3 applying 3 color decomposition to an original picture and reading the result as a color decomposition picture, color code generating means 4-9 generating a color code representing to which of white/achromatic/chromatic color each picture element of a read color decomposition image belongs, a color reproducing means 10, a marker area detection means 13, a sampling means 14, and a marker color conversion means 12 are provided in the processor. Then the marker area detection means 13 detects the area based on the scanning line at picture read, the sampling means 14 samples the density data of the marker at the position of the density peak level in the marker area, and the marker color conversion processing means 12 applies marker color conversion of the picture data based on the sampled density data. Thus, full color marker color conversion is applied.

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 into red R and cyan C, and based on this, they are recorded on recording paper using an output device such as an electrophotographic copying machine. There is an image processing device that does this.

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, red or blue color conversion is performed. There is a problem in that color conversion cannot be performed for anything other than single-color markers. 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, 1 photographic images, etc. can be converted into red R1 green G,
Blue B is read out optically, and this is converted into recording colors such as yellow Y, magenta M, and cyan C1 black, and based on this, recording is performed using a printing device such as an electrophotographic color copying machine. There is a color image processing device that records on paper. Such an apparatus can read and record color originals. However, in these devices, no consideration was given 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.

The present invention has been made in view of the above-mentioned problems, and its first objective is to realize an image processing apparatus capable of performing full-color marker color conversion.

(Means for Solving the Problems) The present invention to solve the above problems includes an image reading means for separating a document image into three colors and reading it as a color separation image, and each pixel of the color separation image read by the image reading means. color code generation means for generating a color code indicating whether the color belongs to white, achromatic color, or chromatic color; and color reproduction for converting the color separation image read by the image reading means into density data according to the recorded color. means for detecting a marker part of a document image based on the color code from the color code generating means, and a marker area detecting means for extracting an area surrounded by the marker part; It has a sampling means for sampling density data, and a marker color conversion means for converting the density data of the area surrounded by the marker part into the density data sampled by the sampling means, and the sampling means converts the density data into which the color is reproduced. The present invention is characterized in that sampling is performed at the position of one novel peak of the density data of any one of the colors.

(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. Regarding the marker area detected in this way, the sampling means samples the density data of the marker at the position of the density peak level within the marker area, and based on the sampled density data, the marker color conversion processing means converts the marker of the image data. Perform color conversion.

(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 5 converts the red image signal read by the DI into 8-bit digital data, and 5 is an A/D converter that converts the green image signal read by the G-CCD 2 into 8-bit digital data. The 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 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 indicating whether each pixel is white/black/chromatic, e.g. white-00, black; 1)
1゜Chromatic color: 10) Processing 1 color reproduction (R, G, B-4YM
, C, K). From this color reproduction table 10, the 2-bit color code and Y,
A density signal of 6 bits each for M, C, and K is output. 1
Reference numeral 1 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 a document and converts the area into a marker color. 13 is an area detection unit that detects the color marker and extracts the area surrounded by the marker; 14 is a sampling unit that samples the density data of the color marker; and 15 is a normalization unit that normalizes the sampled density data. A normalization circuit 16 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 the printer unit 20, which will be described later. When the printer unit 20 is recording black K, this gate section 16 allows the manually-powered black data to pass through as is, and when recording Y, M, and C, it passes only the black data within the marker area. Let it pass. 17 is gate part 1
This is a multiplication circuit that converts black data into marker color data by multiplying the black data that has passed through the color filter 6 by a normalization factor. Note that this multiplier 17 performs multiplication only within the marker area, and passes black data in other areas. 18 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; 1 is a PWM multi-value that converts the 6-bit density signal into multi-values by pulse width variation E (PWM); The conversion section 20 is a printer unit that forms a color image by sequentially overlapping toner images of each color of Y, M, and CK on a photoreceptor drum.

The operation will be explained below with reference to FIG. First, a document image is read by an image reading section. That is, the image information (optical image) of the original 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 (not shown). These color separation images are supplied to C0DI, 2.3 and converted into R, G, and B analog signals, respectively.

This analog signal is sent to an A/D converter 4 for each pixel.
．． 5.6, the data is converted into digital data of a predetermined number of bits, 8 bits in this example. 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 R, G, and B 8-bit data are supplied to a density conversion section.

The density conversion section performs color balance and γ correction, and also converts 8-bit data into 6-bit data for each color.

Then, R, G, B density conversion section 7.8. The output data of 9 is applied to a color reproduction table 10.

In this color reproduction table 10, a color code (2
Bit data, for example white = 00° black: 11. Chromatic color: 1
0) is 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 L*a* by the following formula.
b″′Convert to uniform color space.

L*-118(Y/Yo)"3-16a" = 5
00[(X/Xo)"'-(Y/Yo)"3]b"
-200[(Y/Yo)"'-(Z/Zo)"
] Here, Yo ``100 Xo =98.07 Zo =118.23.

The uniform color space L*a*b'l obtained in this way
', L≧90 is defined as a white area.

■Generation of achromatic (black) code First, calculate Q from the R, G, and B signals using the following formula.

Q praise R-o +G-o +
Bo 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
.

Each 6-bit density data is created.

Thereafter, the color ghost correction section 11 detects and removes color ghosts. This is because unnecessary color ghosts occur especially around black characters during color separation. Color ghost correction detects whether or not a color ghost is present using a 1×7 window, and converts the color code of a pixel in which a color ghost is 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 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 20.
Marker Y, M, according to M, C image formation.
It is normalized and output according to the concentration of C.

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

Thereafter, the PWM multi-value conversion unit 19 performs multi-value conversion using PWM (pulse width modulation) to make it suitable for printing, and the printer unit 20 performs image formation. In this printer unit 20, 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. , L2 will be described in which the image is transferred once after development and transferred onto recording paper such as plain paper.

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 light source 129 such as a halogen lamp, a carriage 132 provided with a reflecting mirror 131, and a 1-4J moving mirror unit 134 provided with mirrors 133 and 133'.

The carriage] 32 and the movable unit 134 are caused to travel on a slide rail 136 at predetermined speeds and directions, respectively, by a stepping motor 135.

Optical information (image information) obtained by irradiating the original [0] with the light source]29 is transmitted to the reflecting mirror 131. mirror 133,
1.33' to an optical information conversion unit 13.7.

On the back side of the left end of the platen glass 128 is a white plate 1.
38 are provided. This is because the image signal is normalized to a white signal by optically scanning the white board 138.

The optical information conversion unit 137 includes a lens 139, a prism 140, and two dichroic mirrors 102.1.03.
and a CCD 1 that captures a red color-separated image, a CCD 2 that captures a green color-separated image, and a CCD 3 that captures a blue color-separated image.

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 into three color optical information of red R1 green G and blue B by the prism 1.40.

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 20) 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 1.
41 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 (photosensitive drum) 1 which is charged with a negative charge 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 using the system controller) and CP for the roll.
A toner replenishing means (not shown) is controlled based on a command signal from U (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 44 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 old 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 body 142 in an overlapping 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.

Toner replenishment to the developing devices 143, 144, 145, and 146 is performed based on a command signal from the CPU as described above, and a predetermined amount of toner is replenished.

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 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. Ru. Then, the multicolor toner image is transferred onto the recording paper P by the transfer pole 151 to which a high voltage is applied from the high voltage power source, and the separation pole 152
separated by

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

The image forming body 142 after the transfer is transferred to the cleaning devices 1 and 4.
7 to prepare 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 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 142 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 147e is rotated in the opposite direction to the image forming body 142 and is pressure bonded thereto. 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 the 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 indicated by PN 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, the AND signal QN-1xpN of both is taken, and this QN-IX
An edge detection pulse R from the rising edge to the falling edge of PN is created. And marker signal P
A logical sum signal QN of N and edge detection pulse RN is created. 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-I XPM of both, and calculate this QM-
Create an edge detection pulse RM from the rising edge to the falling edge of IXPIJ. Then, a logical sum signal QM of the marker signal P 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, M, and C of markers are determined at the peak level of the marker signal.

Sample K concentration data. That is, since this color data sampling is performed at the peak level position of the marker, there is no limitation on the marker line width.

Furthermore, since it is at the peak level, the color of the marker is also stable. 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. 6 is a characteristic diagram showing density levels of Y, M, and C in a certain scanning line. Here, a case will be described in which the peak sampling unit 14 detects the peak value of the yellow level and performs sampling using the peak value. For example, the peak sampling unit 14 samples yellow density data from several pixels within the chromatic color area, and sets the position immediately before the pixel where the level first decreases as the sampling point. Then, the concentrations of Y and MC are sampled at this sampling point. Note that this sampling point may be detected at the peak level position of another color.

Next, the marker color density data obtained in this manner is normalized. That is, the normalization circuit 16 calculates the ratio of the concentrations of Y, M, C, and K based on the maximum value of the concentrations of Y, M, and C as a normalization factor. I ask for it.

These normalization factors (Y', M', C', Ni') are obtained by the following formula. Multiply the black density data in the marker area that has passed through the gate section 16 by the normalization factor obtained in this way. A circuit 17 performs multiplication to obtain marker color-converted image data. That is,
When recording Y, the data passes through the KiJ 1 degree data small data recording section 1-6 in the marking area. This [one-time data multiplication section] multiplies the normalization factor Y by -7, and then
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 161 and the multiplication section 17 as is. Then, the multiplier 17 multiplies the data in the marker area by a normalization factor to obtain an image signal of the 1 (component) of the marker color.

Then, the printer unit 20 prints Y, M, C, K.
By overlapping toner images according to the image signals on the image forming body 142 in the order of , and finally transferring them to transfer paper, an image is formed in which the marker color is converted in the marker area and the other areas are copied as is. .

As described above, in the present invention, 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 the peak portion within the marker area. Marker color conversion is performed by multiplying the black characters (Km degree data) by the normalization factor of each color component and converting it into image data of each color component. Therefore, full-color marker color conversion can be performed accurately and satisfactorily.

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 in detail above, in the present invention, a marker area is detected for each scanning line in the main scanning direction, and Y, M, and C of the marker colors are detected at the position of the density peak level within the marker area. ,K
Marker color conversion is performed by sampling the components and multiplying the black characters (Ka degree data) in the marker area by the normalization factor of each color component to convert into 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 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. FIG. 5 is an explanatory diagram showing how scanning lines are scanned during color conversion, FIG. 5 is a waveform diagram showing how marker area signals are generated, and FIG. 6 is an explanatory diagram showing the relationship between marker areas and sampling points. 1...R-CCD 2...G-CCD3...
・B-CCD 4.5.6...A/D converter 7, 8. 9... Density conversion unit 10... Color reproduction table] 1... Color ghost correction unit 1.2... Marker color conversion unit 13... Area detection unit 1
4... Sampling section 15... Normalization circuit 16.
...Gate section 17...Multiplication section 18...Image processing section

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 reference area and extracting an area surrounded by the marker part; a sampling means for sampling density data of the area surrounded by the marker part; and marker color conversion means for converting the density data of the reproduced area into density data sampled by the sampling means, the sampling means converting the peak level of the density data of any one of the reproduced density data into the density data sampled by the sampling means. An image processing device characterized by being configured to perform sampling at a position.