JPH08321946A - Image processing unit - Google Patents

Abstract

PURPOSE: To discriminate a character part and a color intermediate tone part in an object image in an excellent way. CONSTITUTION: The processing unit is provided with a 1st means (40) discriminating an edge part of an image being an object of the embodiment of this application, a 2nd means (79) discriminating a color component in the vicinity of the edge, and a discrimination means (80) discriminating the object image on the basis of outputs of the 1st and 2nd means to solve the problem above. Thus, the processing unit discriminates a line drawing part and a color image part in an excellent way with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to optimal processing of color images.

[0002]

2. Description of the Related Art Recently, not only in the fields of printing and design,
The number of full-color images has increased even in offices and the like, and along with this, color copying machines that faithfully read and output color originals have become widespread. These color copying machines are required to output a full-color image in high gradation and output a color character original clearly and in high resolution. On the other hand, although a dither method and halftone dot modulation are known as methods for outputting a full color image with high gradation, when these methods are applied to characters and line drawings, the resolution is remarkably lowered and the character quality is deteriorated. On the other hand, binary processing is suitable for good reproduction of characters and line drawings, but it is well known that if this is applied to halftone dots and photographic images, the gradation will be significantly reduced and the image quality will be significantly deteriorated. It is the place. Therefore, many proposals have been made to achieve both the character quality and the halftone quality. For example, (1) JP 61-1171 A
In 9, the Y, M, and C signals are subtracted according to the size of BK (black component) calculated from the color-separated original signals Y (yellow), M (magenta), and C (cyan) and the size of the edge component. , BK signal is increased so that each color component is replaced with a single black component as much as possible in the edge portion of the black character to improve the quality of the character. Also,
(2) Attempts have also been made to apply edge emphasis (circular part emphasis) to the whole area to improve the quality of characters without lowering halftone gradation. Furthermore, there are various methods such as (3) a method in which the operator separately specifies the character area, the halftone dot area, and the photograph area, and switches the high resolution processing and the high gradation processing according to the designated input.

[0003]

According to the above-mentioned conventional method, in the first case, although the outline of a black character is replaced by a single black, for example, human hair or eyelashes is erroneously determined as a black character, or a halftone dot is used. The overlapping portions of the yellow, magenta, and cyan halftone dots in the inside were also judged to be black characters, and unnecessary black dots remained in the halftone dots, and the image quality was not sufficient. In the second case, the sharpness is improved, but since the black character portion is overlaid with four colors, color deviation occurs and the character quality is not sufficient. In the third method, for example, an area designated as a black character portion can be processed in high resolution with a single black, and a halftone processing can be performed in a color halftone area. However, the operation was extremely complicated because the position must be specified with high precision.

In view of the above points, it is an object of the present invention to provide an image processing apparatus capable of satisfactorily discriminating a character portion and a color halftone portion in a target image.

[0005]

In order to achieve the above object, the color image processing apparatus of the first invention of the present application is a first means for discriminating an edge portion of a target image, and a color near the edge portion. It is characterized by having a second means for judging the component, a judging means for judging the target image based on the outputs of the first means and the second means.

The image processing apparatus of the second invention of the present application is the first means for detecting the high frequency component of the target image, the second means for detecting the color component around the target pixel of the target image, And a determination unit that determines the characteristics of the target image based on the detection results of the first and second detection units.

The image processing apparatus of the third invention of the present application extracts the first signal corresponding to the brightness information of the color image and the second and third signals corresponding to the color information from the input signal. Extracting means, first generating means for generating a fourth signal representing the edge portion of the color image based on the first signal, and representing an achromatic portion of the color image based on the second and third signals Second generating means for generating a fifth signal,
Third generation means for generating a sixth signal representing the presence of a chromatic color component in the input signal based on the second and third signals, based on a combination of the fourth, fifth and sixth signals And a determination unit for determining a black line drawing portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments of the present invention described below, an image processing apparatus suitable for application in color copying is disclosed, but the present invention is not limited to such a copying machine, and various kinds of copying machines can be used. Of course, it can be applied to the equipment.

(Embodiment 1) FIG. 1 is a block diagram showing a circuit configuration of a first embodiment of the present invention. R in FIG.
The (red), G (green), and B (blue) signals are color signals for one pixel read from the color original reading device. The color original reading device 1 uses, for example, a mosaic filter CC
What is attached to D1 may be used. In this embodiment, a dot-sequential color signal is output from the CCD 1.
The output is amplified by the amplifier 5 and is then converted into RGB by the color separation circuit 7.
Is color separated. Reference numeral 10 is a circuit for calculating a luminance signal Y and color signals I and Q from RGB signals. The luminance signal Y is a signal for obtaining an edge signal of a black character, is inverted by the inverter 30 and is converted into a darkness signal Y ', and thereafter, the edge is extracted by Laplacian by the black edge generation circuit and KE is output.
The I and Q signals are signals representing the color difference from the achromatic color and are input to the achromatic color signal calculation circuit 20 to output the achromatic color signal W using a look-up table. The larger the value of the W signal, the more achromatic the color is. The W signal and the Y'signal are input to the black level determination circuit 50 and are dark achromatic colors. That is, the black level is output as a T signal with a binary value or more.
The black character edge generation circuit outputs the black character edge signals E ₁ and E ₂ from the black edge signal KE according to the black level signal. The E ₁ signal strengthens the edge of the black character, and E ₂ is a signal for removing the color shift of the edge of the black character. The image area signal generation circuit 70 determines a bright chromatic color and its vicinity as an image area from the W signal and the Y signal, and outputs an image area determination signal Z.
The black character correction circuit 80 obtains C (cyan), M (magenta), Ye (yellow) and K (black) signals from the R, G and B signals. Next, the following correction is performed on the signal in the area where the image area signal Z is not output and where the black character edges E ₁ and E ₂ are generated. That is,
Add E ₂ to C, M and Y as correction signals and E ₁ to K,
Output to an output device such as a printer for the settlement. Further, P is a printer line number signal, which indicates the resolution.

Next, a block of each circuit shown in FIG. 1 will be described.

In FIG. 1, reference numeral 70 is a Y, I, Q signal calculating means using RGB signals as input signals. Next, the Y, I, Q signal calculation circuit will be described with reference to FIG. In FIG. 2, reference numerals 11, 12, and 13 are multipliers for multiplying each R, G, and B signal by a predetermined parameter aij (i, j = 1, 2, 3). Reference numeral 14 is a memory for storing aij, and reference numeral 15 is a selector for selecting each multiplier in order to set the parameters for multiplying the R, G, B signals in the multipliers 11, 12, 13. 16 is a multiplier 11, 1
An adder 17 that adds the outputs of 2 and 13 is an adder 16
Is a selector for selecting the output of each of the Y, I, and Q signals. The Y, I and Q signals are R, G and B signals and the parameter ai
j, Y = a ₁₁ × R + a ₁₂ × G + a ₁₃ × B, I =
a ₂₁ × R + a ₂₂ × G + a ₂₃ × B, Q = a ₃₁ × R + a ₃₂ ×
It is represented by G + a ₃₃ × B.

In FIG. 2, the selector 15 is a set of three coefficients for the R, G, B signals of one pixel to be input, that is, (a ₁₁ , a ₁₂ , a ₁₃ ), (a ₂₁ , a ₂₂ , a ₂₃ ). ,
(A ₃₁ , a ₃₂ , a ₃₃ ) are sequentially generated.

Therefore, the adder 16 sequentially outputs Y, I, and Q signals for the R, G, and B signals of one pixel that are input. The selector 117 outputs the Y signal, the Y signal, the I signal, the Q signal, the I signal, the I signal, and the Q signal.

In FIG. 1, reference numeral 20 is an achromatic signal calculation circuit. FIG. 3 shows the internal structure of the achromatic signal W calculation circuit.
Reference numeral 21 is a multiplier that outputs the square of I, and reference numeral 22 is a multiplier that calculates the square of Q. Reference numeral 23 is an adder that adds the outputs of the multipliers 21 and 22 and outputs (I ² + Q ² ). Reference numeral 24 is a look-up circuit that determines the output W according to the input (I ² + Q ² ).
It's an up table. Look up table 2
The output W of 4 is determined by the following equation.

[0015]

[Outside 1]

Reference numeral 30 denotes the above-mentioned inverter which inverts the Y signal and outputs the Y'signal.

Reference numeral 40 denotes the above-mentioned black edge amount KE generation circuit, which shows the internal configuration of the black edge generation circuit according to FIG.
Reference numerals 31, 32, 33, 34, and 35 are line buffers centering on the pixel of interest. Reference numeral 36 denotes an arithmetic circuit for calculating the edge amount, which performs the following arithmetic operation. If the value stored in the line buffer is xij (i, j = 1, 2, 3, 4, 5), the pixel of interest is represented by x ₃₃ = Y ′, and the edge amount KE is calculated by the following equation. Ask.

KE = x ₃₃ − (x ₁₁ + x ₁₅ + x ₅₁ + x ₅₅ ) / 4

Reference numeral 50 denotes the above-mentioned black level determination circuit, and FIG. 5 shows the internal structure of the black level determination circuit. Reference numeral 51 is a multiplier for multiplying W by Y ', 52 is threshold value output u of the multiplier 51, ₀ if u <T ₀ , ₁ if T ₀ < u <T 1,
A threshold processing circuit that outputs ₂ as a black level signal T if T ₁ <u <T _{2 and} 3 if T ₂ < u.

Reference numeral 60 denotes the above-mentioned edge signal calculation circuit,
Two types of edge signals E ₁ and E ₂ are output from the black edge signal KE from the black edge generation circuit 40 and the black level signal T from the black level determination circuit 50.

FIG. 6 shows the configuration of the edge signal calculating means. Reference numeral 61 is a comparator for comparing the input KE with the threshold value stored in the memory 62, and outputs 1 if KE is larger than the threshold value, and outputs 0 otherwise. Reference numeral 62 is a memory that stores a predetermined threshold value. 63 is an arithmetic circuit for calculating the edge signal E ₁ from KE, T and the output of the comparator 61. When the output of the comparator 61 is 0, E ₁ = 0,
When 1, the arithmetic circuit 63 outputs E ₁ = α ₁ × KE. α
₁ is a constant that is timely determined by the value of T, and E ₁ is expressed using such α ₁ . 64 is KE and memory 65
A comparator for comparing the threshold values stored in 1. outputs 1 if KE is larger than the threshold, and 0 otherwise. 65
Is a memory for storing a predetermined threshold value.
66 is an edge signal E ₂ from the output of KE, T and the comparator 64.
Is an arithmetic circuit for calculating 0 is stored in the memory 65 as a threshold value, and when the output of the comparator 64 is 0, E ₂ = KE
The arithmetic circuit 66 outputs E ₂ = KE × α ₂ when × (−1) × α ₂ , 1. α ₂ is a constant that is timely determined by the value of T, and E ₂ is expressed using such α ₂ .

In FIG. 1, 70 is an image area determination circuit,
The configuration of the image area determination circuit according to FIG. 7 is shown. Reference numeral 71 is a multiplier for multiplying the W signal by reversing the Y signal and the W signal to obtain the X signal. Reference numeral 72 is a threshold processing circuit that compares a predetermined threshold value with the X signal and outputs the magnitude relation between the threshold value and the X signal. 73, 74, 75
Is a line buffer for storing the output of the threshold processing circuit 72. Reference numeral 76 is a peripheral line buffer 73, 7 for the pixel of interest.
It is a circuit that reads out the values of 4, 75 and determines whether or not the pixel of interest is in the image area. If it is in the image area, 1 is output, and if not, 0 is output as the image area signal Z.

In FIG. 1, reference numeral 80 denotes a black character correction circuit, which shows the black character correction circuit according to FIG. Reference numeral 81 is a circuit for calculating cyan (Co), magenta (Mo), yellow (Yo), and black (Ko) signals from the R, G, and B signals by using a known technique. To Y,
It includes a circuit for converting to M and C and a color masking circuit, and a circuit for performing UCR processing and outputting a black (Ko) signal. Reference numeral 82 outputs 1 from the black level signal T and the image area determination signal Z if the black level is not 0 and the image area determination signal Z is 0, and outputs 0 otherwise. 83 is 8
The selector outputs E ₁ ′ = E ₁ and E ₂ ′ = E ₂ if the output of 2 is 1, and outputs E ₁ ′ = 0 and E ₂ ′ = 0 if 0. 84
Is an adder for adding the E ₂ ′ signal to the Co signal, and 85 is M
o The signal 'in adder for adding the signals, 86 is E ₂ in Yo signal' E ₂ by an adder for adding the signals, 87 denotes an adder for adding the E ₂ 'signal to the Ko signal. Reference numeral 88 is a circuit which receives the E ₁ ′ signal as an input signal and generates a printer line number signal P indicating the output resolution of the printer based on the processing in the vicinity of the pixel of interest. 9 shows a printer line number signal generation circuit according to FIG. 881 outputs 0 when the E ₁ 'signal is 0,
Otherwise, it is a comparator that outputs 1. When the output is 0, the low resolution output is shown, and when the output is 1, the high resolution output is shown. Reference numerals 882, 883 and 884 are line buffers for storing the output of the comparator 881 for the pixel of interest and its neighboring pixels, for example, 5 × 5 pixels. The 885 OR circuit outputs 1 which indicates that the pixel of interest is output at high resolution when the pixel of interest and its neighborhood indicate even one pixel output at high resolution, and otherwise outputs the pixel of interest at low level. Outputs 0, which indicates that the image is output at the resolution.

By using such a circuit, it is possible to prevent the output of the printer line number signal generating circuit described later from frequently switching.

Next, FIG. 12 shows an example of an image forming apparatus (laser printer) for forming an image by the image signal output from the above-mentioned apparatus. In the embodiment shown in FIG. 12, gradation is reproduced by a method called PWM modulation. In FIG. 12, reference numeral 201 denotes a latch unit that latches a digital video signal according to a clock V _K obtained by dividing a master clock by a JK-FF 205, 202
Is a D / A converter for converting the latched digital video signal into an analog signal, and 225 is a D / A converter 2
A dynamic range adjusting means for adjusting the dynamic range of the output of 02, 206 is a flip-flop for controlling the phase of the master clock, and a CPU
The flip-flops 222 and 213 divide the clock whose phase is controlled by 206, and the reference numeral 224 controls the phase of the master clock by the output from the flip-flop 213. It is a triangular wave generating means for outputting a triangular wave according to the output. The comparator 204 outputs the output of the dynamic range adjusting means 225 and the triangular wave generating means 208.
And output the comparison result. The triangular wave is a bias adjusting means for adjusting the bias component of the triangular wave in the generating means 208. In the present embodiment, the output of the triangular wave generating means 208 can be switched between a first triangular wave having a relatively high frequency and a second triangular wave having a lower frequency than the first triangular wave, and depending on the output of the CPU 222. Switching is performed. Reference numeral 222 is a CPU that controls each circuit, and 226 is a ROM that stores an operation program.

Reference numeral 227 is a RAM used as a work area when the CPU 222 operates.

Reference numeral 229 is a drum-shaped electrophotographic photosensitive member which rotates in the direction of the arrow. The photoconductor 229 is first uniformly charged by the charger 230, and then the laser beam 231 is modulated by blinking in accordance with the modulation signal E output from the comparator 204.
Then, the photosensitive member 229 is scanned and exposed in a direction substantially perpendicular to the rotating direction of the photosensitive member 229. The electrostatic latent image formed on the photoconductor 229 is visualized by the developing device 232.

The formed visible toner image is transferred to the transfer charger 2
It is transferred to the transfer material 234 by 33. The visible toner image transferred to the transfer material 234 is fixed by a fixing device (not shown),
On the other hand, the toner remaining on the photoconductor 229 after the transfer is removed and cleaned by the cleaning device 235. After that, the electric charges remaining on the photoconductor 229 are eliminated by the elimination light of the lamp 236, and the above steps are repeated again.

In this embodiment, the toner is Y, M,
Four colors of C and K are prepared, and printing for four colors is performed in a frame sequential manner. That is, full-scale image formation is performed.

The laser beam 231 is a semiconductor laser 237.
Is emitted from. The semiconductor laser 237 is driven by the drive circuit 241 to which the pulse width modulation signal E output from the comparator 204 is applied, and the modulation signal E
The laser beam 231 that is blink-modulated in accordance with is emitted.

The laser beam 231 emitted from the semiconductor laser 237 is scanned by a scanner 238 such as a rotary polygon mirror or a galvano mirror. 239 is the laser beam 2
A lens for forming a point image on the photoconductor 229;
Is a mirror for breaking the optical path.

FIG. 13 shows the triangular wave generating means 2 shown in FIG.
10 is a diagram showing another configuration example of the internal configuration of No. 08 and its peripheral configuration, showing an example of a circuit used when performing image formation by performing the pulse width modulation. The digital video signal Vin from the interface is latched 301
Then, the video clock VCLK is latched and synchronized. The image signal D _vin is converted into an analog video signal AV by the D / A converter 302. The output of the D / A converter 302 is converted to a voltage level by the resistor 303 and then input to one input terminal of the two comparators 304a and 304b. Also, in this example, two systems of triangular wave generating circuits having an integrator circuit as a basic configuration are prepared, and each PHCL is synchronized with VCLK and has different cycles.
J / K flip-flop 3 that divides K and TXCLK by 2
The outputs of 05 and 313 are integrated. Here, the frequency of TXCLK is a relatively high frequency of a for which resolution is important, for example, a frequency for 400 dpi. On the other hand, the frequency of PHCLK is set to be a relatively low b frequency (where a> b) where gradation is important, for example, a frequency for 200 dpi. These frequency-divided 50% duty clocks are passed through the buffers 306a and 306b to the resistor 3
An integrating circuit composed of 07a and 307b and capacitors 308a and 308b produces a triangular wave. Then, the bias amount is adjusted by the capacitors 309a and 309b and the resistors 310a and 310b, and the above-described comparators 304a and 304b are adjusted.
Of the pulse width modulation signals Ea and Eb of two systems, which are input to the other input terminal of the
Becomes

The switch 318 supplies the two signals E
The selector circuit 318 switches a and Eb to Ea for the character portion and Eb for the photograph (halftone image) portion by the control signal CIS from the CPU 322. This switching is performed by the operation of the CPU 322 in synchronization with the signal corresponding to the signal P in FIG.

354 is a switching circuit for switching the output of the counter 352 or the address output from the CPU via the address bus according to the switching signal select, and 352 is a counter for counting VCLK. Three
58 is an address and CPU output from the selector 354
D based on the data output from the
-A circuit that outputs a signal to the FF350.

The CPU 222 responds to the P output from the black character correction circuit 80 shown in FIG.
Selectors 354 and 35 for switching the output of 4b.
Address and data are set in 8 respectively.

Therefore, according to the configuration of the embodiment shown in FIG. 13, the CPU 222 can make a desired correction when switching the two outputs of the comparators 304a and 304b according to the output of the black character correction circuit 80.

Further, in the embodiment shown in FIG. 12 described above, the frequency of the triangular wave output by the triangular wave generating means input to the comparator 204 is changed, but in the embodiment shown in FIG. 304
b is provided, and the outputs of these two comparators are switched by the switch 318. Therefore, the responsiveness of the circuit is improved.

In the above apparatus, the edge is strengthened for the area determined to be the character portion, and the edge is not strengthened for the area determined to be the halftone dot color image. It Further, in the area determined to be the character portion, the frequency of a requiring high resolution is automatically selected, and in the area determined to be the color image, the frequency of b requiring gradation is automatically selected. As a result, the reproduced image quality is further improved.

(Embodiment 2) Next, an embodiment will be described in which black character processing in the vicinity of the extracted characters and line drawing components of a predetermined color is performed in the black character correction circuit of FIG.

FIG. 10 shows a black character correction circuit by binary processing. 91 is a known technique for converting R, G, B signals into cyan (Co), magenta (Mo), yellow (Yo),
This is a circuit for calculating black (Ko). An AND circuit 92 outputs 1 when the black level signal T has a value other than 0 and the image area signal is 0, and outputs 0 otherwise. Reference numeral 93 determines the number of printer lines from the output of the AND circuit 92 near the pixel of interest. This is a printer line number signal generation circuit. The selectors 94, 95, 96, 97 respectively output 0, 0, 0, Ko when the printer line number signal P is 1.
Is output, and when P is 0, Co, Mo, Yo, 0 is output.

(Embodiment 3) Next, an embodiment will be described in which the black character correction circuit in FIG. 1 performs black character processing in the vicinity of the extracted characters of a predetermined color and line drawing components.

FIG. 11 shows a black character correction circuit by binary processing. 101 is an R, G, B signal using a known technique,
Cyan (Co), Magenta (Mo), Yellow (Y
o) and black (Ko). 102
Indicates that the black level signal T is a value other than 0 and the image area signal is 0
It is an AND circuit that outputs 1 when, and 0 otherwise. 103 is an AND circuit 102 near the pixel of interest
Is a printer line number signal generation circuit that determines the number of printer lines from the output of. Reference numeral 104 is a printer line number generation circuit 1
This is a dither processing circuit which performs known dither processing only when the output of 03 is 0 and makes the given signal through when the output of the circuit 103 is 1.

In the above embodiment, first, the black area is extracted by the lightness information of the document and the information again, and the edge component of the document is further extracted to determine the black edge portion and color information in the vicinity. , And automatically distinguishing the black character from the color image and the black thin line in the halftone dot based on the degree of the black edge and the degree of the color information in the vicinity, without the need for the operator's hand. It is possible to achieve both high-quality halftone or halftone dots and black characters.

That is, in the present embodiment, when the characteristics of the target image are discriminated, not only the high frequency component of the target image and the color component of the target image of the target image but also the peripheral color components thereof are detected. In the color image formed by dots, there is no fear of erroneously determining that a black dot portion in which halftone dots of each color overlap is a black character.

Therefore, it is possible to separately judge a predetermined color character and another image, for example, a color image formed by halftone dots. As a result, it is possible to suppress the color shift of the black character, reduce the false operation of erroneously detecting that the dot in which each color dot in the color halftone image overlaps is a black character, and significantly improve the quality of the black character. Further, even in a document in which characters and color images are mixed, both of them can be automatically discriminated.

(Embodiment 4) In the above embodiment, the case of extracting a black character has been described, but in the case of extracting a red character, first, the value of the R signal is set as the value of the luminance signal Y in the YIQ calculation circuit. Is output. In the above-described embodiment, the Y signal uses R, G, B signals, and Y = a ₁₁ × R + a ₁₂ × G
It was calculated by + a ₁₃ × B, but at this time, each parameter is
It suffices if a ₁₁ = 1, a ₁₂ = 0, and a ₁₃ = 0.

Further, the lookup table for obtaining the W signal from the I signal and the Q signal in the achromatic color signal calculating circuit has been described above, but the present invention is not limited to this and may be set using the following equation. However, in the following equation, a and b are constants. Other parameters may be used as long as they are signals indicating the degree of chromatic color and achromatic color.

[0048]

[Outside 2]

Next, another embodiment of the achromatic color signal calculation circuit shown in FIG. 3 will be described with reference to FIG. In FIG. 4, 191 is a circuit for calculating the maximum value of the R, G, B3 signals, and 192 is a circuit for calculating the minimum value of the R, G, B3 signals. Reference numeral 193 is a subtractor for subtracting the minimum value of the R, G, B3 signals output from 192 from the maximum value of the R, G, B3 signals output from 191. 1
The inverter 94 inverts the output of the subtractor 193 and outputs the achromatic signal W.

Further, in order to determine the degree of achromatic color, not limited to this, various other methods can be applied.

In the embodiment, the edge in the target image is discriminated as one method of detecting the high frequency component of the target image, but the present invention is not limited to this, and a circuit for simply extracting the high frequency component of the image information is used. May be.

As described above, according to the embodiment, it is possible to determine a predetermined color character and other images. As a result, it was possible to suppress the color shift of black characters, reduce the false detection of black characters in a halftone dot image, and significantly improve the quality of black characters. Further, even for a document in which characters and color images are mixed, it is possible to automatically determine characters and color images without the need for an operator, and it is possible to improve scanning efficiency.

In the present embodiment, the image area determination circuit of FIG. 1 whose internal configuration is shown in FIG. 7 is used as the means for determining the color components near the edges, but the present invention is not limited to this configuration, and other configurations, for example, In order to detect the color components near the edge, for example, a CCD
In addition to 1, the dedicated sensor may be provided.

[0054]

As described above, the first, second and third aspects of the present application are described.
According to the third aspect of the invention, it is possible to accurately and satisfactorily distinguish the character / line drawing portion and the color image portion.

[Brief description of drawings]

FIG. 1 is a diagram of an image processing apparatus embodying the present invention.

FIG. 2 is a diagram showing a YIQ signal calculation circuit in FIG.

3 is a diagram showing an achromatic signal calculation circuit in FIG.

FIG. 4 is a diagram showing a black edge generation circuit in FIG.

5 is a diagram showing a black level determination circuit in FIG.

6 is a diagram showing an edge signal calculation circuit in FIG.

7 is a diagram showing an image area determination circuit in FIG.

FIG. 8 is a diagram showing a black character correction circuit in FIG.

9 is a diagram showing a printer line number generation circuit in FIG.

FIG. 10 is a black character correction circuit (a diagram showing binary processing.

FIG. 11 is a block diagram showing the configuration of each black character correction circuit (dither processing).

FIG. 12 is a diagram showing an example of a printer.

13 is a diagram showing a configuration of 208 of FIG.

FIG. 14 is a block diagram showing the configuration of another embodiment of the achromatic color signal calculation circuit in FIG.

[Explanation of symbols]

 1 Color Document Reading Device 10 YIQ Signal Calculation Circuit 20 Achromatic Color Signal Calculation Circuit 80 Black Character Correction Circuit 103 Printer Line Number Signal Generation Circuit 204 Comparator

Claims (5)

[Claims] 1. A first means for determining an edge portion of a target image, a second means for determining a color component near the edge portion, a first image based on outputs of the first and second means. An image processing apparatus, comprising: a determination unit that performs the determination. 2. A first means for detecting a high frequency component of a target image, and a second means for detecting a color component around a target pixel of the target image.
And a determining unit that determines the characteristics of the target image based on the detection results of the first and second detecting units. 3. The image processing apparatus according to claim 1, wherein the color component is a chromatic color or a component indicating a degree of the chromatic color. 4. The image processing apparatus according to claim 1, wherein the determination means is means for determining a character line drawing area and a halftone dot image area in the target image. 5. A first signal corresponding to brightness information of a color image from the input signal and second and third signals corresponding to color information.
Extracting means for extracting the signal of No. 1, first generating means for generating a fourth signal representing the edge portion of the color image based on the first signal, and generating the fourth image of the color image based on the second and third signals. Second generating means for generating a fifth signal representing the achromatic portion, and third generating means for generating a sixth signal representing the presence of a chromatic color component in the input signal based on the second and third signals. An image processing apparatus comprising: a generation unit and a determination unit that determines a black line drawing portion based on a combination of the fourth, fifth, and sixth signals.