JPH02140057A - Picture processor and image forming device - Google Patents

Abstract

PURPOSE:To discriminate a character part and a color halftone part in an object picture in an excellent way and to form a picture of the character part while increasing the resolution and the gradation of the halftone part by providing a black character edge generating circuit and a black character correction circuit or the like. CONSTITUTION:A signal from a color original reader 1 is separated into R, G, B colors via an amplifier 5 and a color separation circuit 7, and a luminance signal Y and chrominance signals I, Q are calculated by a YIQ signal calculation circuit 10. Then the signal Y is inverted by an inverter 30 and converted into a darkness signal inverse of Y and black character edge signals E1, E2 are outputted via a black edge generating circuit 40 and a black character edge generating circuit 60. Moreover, the signals I, Q are inputted to a black level discrimination circuit 50 via an achromatic signal calculation circuit 20, and a T signal representing a black level is outputted, an image area signal generating circuit 70 receives W and Y signals to output an image area discrimination signal Z. Then a black character correction circuit 80 obtains C, M, Ye, K signals and correction processing is applied. Thus, a character and a line picture part are discriminated in an excellent way with high accuracy to form a picture.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image processing device and an image forming device, and in particular,
Concerning optimal processing of color images.

[Conventional technology]

2. Description of the Related Art In recent years, full-color images have been increasing not only in the fields of printing and design, but also in offices and the like, and color copying apparatuses that faithfully read and output color originals have become widespread. These color copying machines are required to simultaneously output full-color images with high gradation and output color text documents clearly and with high resolution. On the other hand, methods such as dithering and halftone dot modulation are known as methods for outputting full-color images with high gradations, but when these methods are applied to characters and line drawings, the resolution is significantly lowered and the character quality is degraded. On the other hand, binary processing is suitable for reproducing text and line drawings well, but it is well known that when this is applied to halftone dots or photographic images, the gradation drops significantly and the image quality deteriorates considerably. This is the place. Therefore, in order to achieve both character quality and halftone quality, a number of proposals have been made.For example, (1) In the case of Jikai 61-11719, the color-separated original signal Y (yellow) 9M (magenta) , Y, M, and C signals are subtracted according to the size of the old (black component) calculated from C (cyan) and the size of the edge component, and the signal is increased by a factor of BK, so that the edges of black characters are (2) replaces each color component with the black rate component as much as possible to improve the quality of the characters.In addition, (2) applies edge emphasis (limb emphasis) to the entire image without reducing the midtone gradation. Attempts have also been made to improve the quality of characters.Furthermore, (3)
There are various methods, such as a method in which an operator separately specifies a character area, a halftone dot area, and a photo area, and switches between high resolution processing and high gradation processing according to the specified input.

[Problem to be solved by the invention]

According to the conventional method described above, in the first case, the outline of the black character is replaced with a solid black, but for example, large hair or eyelashes may be mistakenly judged as black characters, or each of the yellow, magenta, and cyan colors in the halftone dots may be The areas where the halftone dots overlapped were also judged as black characters, leaving unnecessary black dots among the halftone dots, and the image quality was not satisfactory. In the second case, the sharpness is improved, but since only four colors are superimposed on each other in the black text area, color shift occurs and the quality of the text is not sufficient. In the third method, each area can be processed, for example, an area designated as a black character part is processed with high resolution using only black, and an area with color halftones is processed with halftone processing, but each time the operator The operation was extremely complicated because the position had to be specified with high precision.

In view of the above-mentioned points, one object of the present invention is to provide an image processing device that can satisfactorily discriminate between a character portion and a color halftone portion in a target image.

In addition, the present invention improves the resolution of character parts in the target color image (
Another object of the present invention is to provide an image forming apparatus that can form images with high gradation in intermediate tone parts.

[Means to solve the problem]

In order to achieve the above object, the color image processing device of the first invention of the present application includes a first color image processing device for determining the edge portion of the target image.
A second means for determining color components near the edge portion, and a determining means for determining the target image based on the outputs of the first means and the second means.

Further, the color image processing device according to the second invention of the present application includes: a first means for detecting a high frequency component of a target image; a second means for detecting a color component around a pixel of interest of the target image; 11. A determination means for determining the characteristics of the target image based on the detection result of the second detection means.

In order to achieve the above-mentioned object, a color image forming apparatus according to another aspect of the present application includes a discriminating means for discriminating a character part in a target color image to be formed, a color image forming means whose resolution can be switched, and a color image forming apparatus according to another aspect of the present invention. [Embodiment] The embodiment of the present invention described below is characterized in that it has a control means for controlling the resolution of the color image forming means based on the discrimination by the discrimination means. Although an image processing apparatus is disclosed, the present invention is not limited to such a copying machine (it goes without saying that it can be applied to various devices).

(Embodiment 1) FIG. 1 is a block diagram showing a circuit configuration of a first embodiment of the present invention. In Figure 1, R (red) and G (green).

The B (blue) signal is a color signal for one pixel read by the color document reading device. The color original reading device l may be one in which a mosaic filter is bonded to a CCDI, for example. In this embodiment, a dot-sequential color signal is output from the CCDI, and this output is amplified by an amplifier 5 and separated into RGB by a color separation circuit 7. 1
0 is the RGB signal, the luminance signal Y and the color signal? , Q is a circuit for calculating. The luminance signal Y is inverted by an inverter 30 and converted into a darkness signal Y to obtain an edge signal of a black character, and then edges are extracted by a Laplacian in a black edge generation circuit and KE is output. ? , Q signal is a signal representing a color difference from an achromatic color, and is input to an achromatic signal calculation circuit 20, which outputs an achromatic signal W using a lookup table. The larger the value of the W signal, the more achromatic the color. The W signal and the y signal are input to the black level determination circuit 50 and are dark achromatic.

That is, the black level is output as a T signal with a value of two or more values. The black character edge generation circuit generates black character edge signals E, , E2 according to the black level signal from the black edge signal KE.
Output. E1 signal emphasizes the edges of black letters,
2 is a signal for removing color shift at the edges of black characters. The image area signal generation circuit 70 determines the bright chromatic color and its vicinity from the W signal and the Y signal as the image area, and generates an image area determination signal Z.
Output. In the black character correction circuit 80, R, G, B
C (cyan), 1M (magenta), Ye (yellow), and K (black) signals are obtained from the signals. Next, the image area signal Z
is an area where is not output, and black text edge E
The following correction is performed on the signal in the area where 1°E2 occurs. That is, E 2 is added to C, M, and Y, and E is added to K as correction signals, and the resultant signals are output to an output device such as a next-stage printer. Further, P is a printer line number signal, which indicates the resolution.

Next, the blocks of each circuit shown in FIG. 1 will be explained.

In FIG. 1, 70 is Y whose input signal is an RGB signal;
This is I and Q signal calculation means. Next, using Figure 2, Y
, I, Q signal calculation circuit will be explained. In Figure 2, 11. 12. 13 is a multiplier that multiplies R and B signals by a predetermined parameter aij (i, j=1°2.3). 14 is a memory that stores aij, and 15 is a multiplier 11 for the parameters to be multiplied by the R, G, and B signals. 12. This is a selector for selecting each multiplier to set it to 13.

16 is a multiplier 11. 12. An adder 17 adds the outputs of the adder 16, and a selector 17 selects the output of the adder 16 into Y, I, and Q signals. The Y, I, and Q signals are
=a,,XR+a +2XG+a 13xI3s I=
a21XR+a 22XG+a23X B SQ =
a 3Hx R+ a 32x G 10a 33 x
It is represented by B.

In FIG. 2, the selector 15 selects R of one input pixel,
A set of three coefficients for the G and B signals, namely (ao+
a12+ a+3)s (azz a221 a23)
% (afflla:+z, a*s) are generated sequentially.

Therefore, the adder 16 inputs RlG of one pixel,
In response to the B signal, Y, I, and Q signals are sequentially output. The selector 117 outputs the Y signal to line a, the I signal to line b, and the line C from the input sequential Y, I, and Q signals.
outputs a Q signal.

In FIG. 1, 20 is an achromatic color signal calculation circuit.

FIG. 3 shows the internal configuration of the achromatic signal W calculation circuit.

2I is a multiplier that outputs the square of I, and 22 is a multiplier that calculates the square of Q. 23 is a multiplier 21. An adder that adds the outputs of 22 and outputs (1' + Q"),
24 outputs W according to the input (F + Q")
Decide on your look and up while on the table. look·
The output W of the up table 24 is determined by the following formula.

30 is the aforementioned inverter which inverts the Y signal and outputs the Y signal.

Reference numeral 40 designates the aforementioned black edge fiKE generation circuit, and shows the internal configuration of the black edge generation circuit shown in FIG.

31, 32, 33, and 34.35 are line buffers centered on the pixel of interest. 36 is an arithmetic circuit for calculating the edge amount, and performs the following arithmetic operation. Assuming that the value stored in the line buffer is Xij (il j=1.2.3.4.5), the pixel of interest is represented by x33=Y, and the edge fiKE is calculated using the following equation.

KE:=x33 (X+1+x15+xs++xss
)/450 is the aforementioned black level determining circuit, and FIG. 5 shows the internal configuration of the black level determining circuit. 51 is a multiplier that multiplies y and W; 52 performs threshold processing on the output U of the multiplier 51; if u<To, then 0; if To≦u<T 1, then 1; and T
This is a threshold processing circuit that outputs 2 as the black level signal T if l<u<T2, and 3 if T2<u.

Reference numeral 60 denotes the edge signal calculation circuit described above, which combines the black edge signal KE from the black edge generation circuit 40 and the black level determination circuit 5.
From the black level signal T from 0 to two types of edge signals E
Output l * E 2.

The configuration of the edge signal calculation means according to FIG. 6 is shown.

61 is a comparator that compares the input KE with the threshold value stored in the memory 62; if KE is greater than the threshold value! , otherwise outputs 0. 62 is a memory that stores predetermined threshold values. 63 is an edge signal E from KE, T, and the output of the comparator 61;

This is an arithmetic circuit that calculates . When the output of the comparator 61 is O, E, when = O1l, E, = α, XKE is calculated by the calculation circuit 63.
outputs. α1 is a constant determined timely according to the value of T, and El is expressed using such α1. 64 is a comparator that compares KE with the threshold value stored in the memory 65; if KE is larger than the threshold value, 11; otherwise, O
Output. 65 is a memory that stores predetermined threshold values.

66 is an edge signal E2 from KE, T and the output of the comparator 64.
This is an arithmetic circuit that calculates . 0 is stored in the memory 65 as a threshold value, and when the output of the comparator 64 is 0, E 2 = K
When Ex (-1)xα2.1 E2=I(EXα2
The arithmetic circuit 66 outputs. α2 is a constant determined timely according to the value of T, and E2 is expressed using α2.

In FIG. 1, numeral 70 denotes an image area determination circuit, which shows the configuration of the image area determination circuit shown in FIG. 71 is a multiplier that obtains the X signal by multiplying the Y signal and the W signal obtained by inverting the W signal. 72 is a predetermined threshold value and
This is a threshold processing circuit that compares signals and outputs a magnitude relationship between the threshold value and the X signal. 73, 74, and 75 are line buffers that store the output of the threshold processing circuit 72. 76
is the line buffer 73 around the pixel of interest. 74.75
This circuit reads out the value of and determines whether the pixel of interest is in the image area.

If it is an image area, 1 is output as the image area signal Z, otherwise O is output as the image area signal Z.

In FIG. 1, 80 is a black character correction circuit, which shows the black character correction circuit shown in FIG. 81 is cyan (Co) from the R, G, and B signals using a known technique.

This is a circuit that calculates magenta (Mo), yellow (Yo), and black (Ko) signals, and internally contains R, G,
A circuit that converts B to Y, M, and C, a color masking circuit, and a UCR process to create black (K o )
Contains a circuit that outputs a signal. 82 outputs 1 from the black level signal T and image area determination signal Z if the black level is not O and the image area determination signal Z is 0, and otherwise outputs 0. 83 is ``I' = E if the output of 82 is 1
I + E2 = If E2 is 0, then E, ' = O, E
This is a selector that outputs 2=0. 84 is E to Co signal
85 is an adder that adds E2' signal to Mo signal.
The adder 86 adds the E2' signal to the Mo signal, and the adder 87 adds the Ko multiplied signal E, / signal. Reference numeral 88 denotes a circuit that receives the E and / signals as input signals and generates a printer line number signal P indicating the output resolution of the printer based on processing in the vicinity of the pixel of interest. The printer line number signal generation circuit according to FIG. 9 is shown. 881 is a comparator that outputs O when the E, / signal is 0, and outputs l otherwise. Output is O
When , it indicates output at low resolution, and when it indicates output at high resolution. Line buffers 882, 883, and 884 store the output of the comparator 881 for the pixel of interest and its neighboring pixels, for example, 5×5 pixels. 88
In the OR circuit 5, if the pixel of interest and even one pixel in its vicinity are outputting at high resolution, it outputs l indicating that the pixel of interest is to be output at high resolution; otherwise, the pixel of interest is output at a low resolution. Outputs 0 indicating that the resolution is to be output.

By using such a circuit, it is possible to prevent frequent switching of the output of the printer line number signal generation circuit, which will be described later.

Next, FIG. 12 shows an example of an image forming apparatus (laser printer) that forms an image using an image signal output from the above-mentioned apparatus. In the embodiment shown in FIG.
The gradation is reproduced by a method called M modulation. In Figure 12, 201 indicates the master clock
- A latch unit that latches a digital video signal according to the clock VK frequency-divided by the FF 205, 202 a D/A converter that converts the latched digital video signal into an analog signal, and 225 a dynamic output of the D/A converter 202. Dynamic range adjustment means 206 is a flip-flop for controlling the phase of the master clock, and the CPU 222
213 is a flip-flop that divides the clock whose phase is controlled by 206, and 224 controls the phase of the master clocker by the output from the flip-flop 213. This is a triangular wave generating means for outputting a triangular wave according to the output. Comparator 204 compares the output of dynamic range adjustment means 225 and the output of triangular wave generation means 208, and outputs the comparison result. Triangular wave is generation means 2
08 is a bias adjustment means for adjusting the bias component of the triangular wave. In this 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, depending on the output of the CPU 222. Switching is performed. 222 is a CP that controls each circuit.
226 is R in which the operating program is stored.
It's OM.

Further, 227 is a RAM used as a work area when the CPU 222 operates.

229 is a drum-shaped electrophotographic photoreceptor that rotates in the direction of the arrow. The photoreceptor 229 is first uniformly charged by a charger 230, and then the photoreceptor 229 is charged with a blinking modulated laser beam 231 corresponding to the modulation signal E output from the comparator 204.
The light is scanned and exposed in a direction substantially perpendicular to the rotation direction of 29. The electrostatic latent image thus formed on the photoreceptor 229 is developed and visualized by the developer 232.

The formed visible toner image is transferred onto a transfer material 234 by a transfer charger 233. The visible toner image transferred to the transfer material 234 is fixed by a fixing device (not shown), while the toner remaining on the photoreceptor 229 after transfer is removed by a cleaning device 235.
removed and cleaned. Thereafter, the charge remaining on the photoconductor 229 is eliminated by the discharge light from the lamp 236, and the above steps are repeated again.

In this example, the toners are Y, M, and C.

Four colors of K are prepared, and the four colors are printed sequentially. That is, full-color image formation is performed.

Laser beam 231 is emitted from semiconductor laser 237. Thus, the semiconductor laser 237 is connected to the comparator 204.
The laser beam 231 is driven by a drive circuit 241 to which a pulse width modulation signal E is applied, and emits a laser beam 231 blinking modulated in accordance with the modulation signal E.

Laser beam 231 emitted from semiconductor laser 237
is scanned by a scanner 238 such as a rotating polygon mirror or a galvano mirror. 239 is a lens for forming a dot-like image of the laser beam 231 on the photoreceptor 229, and 240 is a mirror for folding the optical path.

FIG. 13 is a diagram showing another example of the internal configuration and peripheral configuration of the triangular wave generating means 208 shown in FIG. 12, and is an example of a circuit used when performing the above-mentioned pulse width modulation to form an image. This is what is shown.

The digital video signal Vin from the interface is latched and synchronized with the video clock VCLK by the latch 301. This image signal D v+. 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 a resistor 303 and then sent to two comparators 304a.

It is input to one input terminal of 304b. In addition, in this example, two systems of triangular wave generation circuits whose basic configuration is an integrating circuit are prepared, each synchronized with VCLK and having different periods;
The outputs of flip-flops 305 and 313 are integrated.

Here, the frequency of TXCLK is a relatively high frequency a where resolution is important, for example, a frequency for 400 dpt. On the other hand, the PHCLK frequency is a relatively low 5 frequency (however, a>b) where gradation is important, for example, 20 Odpi.
It is set to the desired frequency.

These divided 50% duty clocks are passed through buffers 306a and 306b to resistors 307a and 306b.
307b and an integrating circuit composed of capacitors 308a and 308b, forming a triangular wave. And capacitor 309
a, 309b.

The bias amount is adjusted by resistors 310a and 310b, and is input to the other input terminal of the aforementioned comparators 304a and 304b, and compared with the analog video signal AV.
Two systems of pulse width modulation signals Ea and Eb are obtained.

These two signals Ea and Eb are input to the switch 318, and according to the control signal CIS from the CPU 322, the selector circuit 318 selects Ea for the text portion and Eb for the photo ()1-tone image) portion. It is switched with . This switching is performed by the operation of the CPU 322 in synchronization with a signal corresponding to the signal P in FIG.

Note that 354 is a switching circuit that switches the output of the counter 352 or the address output from the CPU via the address bus in accordance with the switching signal 5etect;
is a counter that counts VCLK. 358 is a D-FF 350 based on the address output from the selector 354 and the data output from the CPU via the data bus.
This is a circuit that outputs a signal to.

The CPU 222 sets addresses and data in the selectors 354 and 358, respectively, in order to switch the outputs of the comparators 304a and 304b according to the P output from the black character correction circuit 80 shown in FIG.

Therefore, according to the configuration of the embodiment shown in FIG.
The PU 222 can perform desired corrections when switching between the two outputs of the comparators 304a and 304b in accordance with 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 outputted by the triangular wave generating means input to the comparator 204 is changed, but in the embodiment shown in FIG. 13, two comparators 304a are used.

304b is provided, and the outputs of these two comparators are switched by a switch 318.

Therefore, the responsiveness of the circuit is improved.

In the above-mentioned apparatus, edges are emphasized for areas determined to be text portions, and edges are not emphasized for areas determined to be halftone color images. Further, for areas determined to be text areas, frequency a, which requires high resolution, is automatically selected, and for areas determined to be color images, frequency b, which requires gradation, is automatically selected. This further improves the quality of the reproduced image.

(Embodiment 2) Next, an embodiment will be described in which the black character correction circuits 1 and s'''C1 in FIG.

FIG. 10 shows a black character correction circuit using binary processing.

91 uses known technology to obtain R, G, B signal power 1, cyan (Co), magenta (Mo), yellow (Y
o) This is a circuit that calculates black (Ko). 92 is black 1. AND that outputs 1 when the % level signal T is a value other than 0 and the image area signal is O, otherwise outputs O
It is a circuit. 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. When the printer line number signal P is 1, the selectors 94, 95, 96, 97 are set to 0. O
, O, Ko, and when P is O, each Co.

This is a selector that outputs Mo, Yo, and O.

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

FIG. 11 shows a black character correction circuit using binary processing.

101 uses known technology to extract cyan (Co), magenta (Mo), yellow (
Yo).

This is a circuit that calculates black (K o ). 102 is an AND circuit that outputs 1 when the black level signal T is a value other than 0 and the image area signal is 0, and outputs O otherwise. 103 is a printer line number signal generation circuit that determines the printer line number from the output of the AND circuit 102 near the pixel of interest. 104 is a printer line number generation circuit 10
This dither processing circuit performs known dither processing only when the output of circuit 103 is 0, and passes the applied signal when the output of circuit 103 is 1.

In the above embodiment, first, black areas are extracted based on brightness information and saturation information of the document, and edge components of the document are further extracted to determine black edge portions.
By referring to nearby color information and automatically distinguishing between black text, color images, and black lines in halftone dots based on the degree of black edges and the degree of nearby color information, it is possible to eliminate operator intervention by referring to nearby color information. It is possible to achieve both high-quality halftones or halftone dots and black characters without causing any distortion.

That is, in this embodiment, when determining the characteristics of a target image, not only the high frequency components of the target image and the color components of the image of interest of the target image (but also the surrounding color components are detected, so the halftone dots are detected). There is no fear that a black dot portion where halftone dots of each color overlap in the formed color image will be erroneously determined to be a black character.

Therefore, predetermined color characters and other images, for example, color images formed with halftone dots, can be determined separately. As a result, it is possible to suppress the color shift of black characters, reduce the erroneous detection that a dot of each color in a color halftone image is erroneously detected as a black character, and greatly improve the quality of black characters. Furthermore, even in a document containing a mixture of text and color images, both can be automatically distinguished.

(Example 4) In the above example, the case of extracting black characters was explained, but when extracting red characters, first YIQ
The calculation circuit outputs the value of the R signal as the value of the luminance signal Y. In the above embodiment, the Y signal uses R, G, and B signals, and Y=a 11 XR + a 12 xG0a13X
B, but at this time each parameter is aII
=L aI□=Q, B, 3=Q.

Also, as mentioned above, the look-up table for determining the W signal from the ■ signal and Q signal in the achromatic signal calculation circuit is
The setting is not limited to this, and the following equation may be used. However, in the following equation, a and b are constants.

Any other parameter may be used as long as it is a signal indicating the degree of chromatic color or achromatic color.

Next, another embodiment of the achromatic color signal calculation circuit shown in FIG. 3 will be described using FIG. 4. In Figure 4, 19
1 is a circuit that calculates the maximum value of the R, G, and B3 signals, and 192 is a circuit that calculates the minimum value of the R, G, and B3 signals. 193 is R output from 191,
From the maximum value of the G and B3 signals, the R output from 192
, G, B3 This is a subtracter that subtracts the minimum value of the signal.

An inverter 194 inverts the output of the subtracter 193 and outputs an achromatic signal W.

In addition, various other methods can be applied to determine the degree of achromatic color.

In the embodiment, edges in the target image are determined as one method for detecting high frequency components of the target image, but the present invention is not limited to this, and a circuit that simply extracts high frequency components of image information may be used. .

As explained above, according to the embodiment, it has been realized that characters of a predetermined color and other images can be determined. As a result, we were able to suppress the color shift of black characters, reduce the false detection of black characters in halftone images, and significantly improve the quality of black characters. Furthermore, even for documents containing a mixture of text and color images, it is possible to automatically distinguish between text and color images without the need for an operator's intervention, resulting in improved operational efficiency.

In this embodiment, the image area determination circuit shown in FIG. 1, the internal configuration of which is shown in FIG. For example, in addition to the CCDI, a dedicated sensor may be provided to detect nearby color components.

〔Effect of the invention〕

As explained above, the first aspect of this application. According to the second aspect of the invention, it is possible to discriminate between characters, line drawing parts, and color image parts with good accuracy.

Further, according to the color image forming apparatus of the present invention, it is possible to form images of characters, line drawings, and color image portions satisfactorily.

[Brief explanation of the drawing]

1 is a diagram of an image processing device implementing the present invention, FIG. 2 is a YIQ signal calculation circuit in FIG. 1, FIG. 3 is an achromatic signal calculation circuit in FIG. 1, and FIG. 4 is a diagram of an image processing device in FIG. 5 is the black level determination circuit in FIG. 1, FIG. 6 is the edge signal calculation circuit in FIG. 1, FIG. 7 is the image area determination circuit in FIG. 1, and FIG. 8 is the black level determination circuit in FIG. Figure 9 shows the configuration of the black character correction circuit in the figure, Figure 9 shows the printer line number generation circuit in Figure 8, Figure 1O shows the black character correction circuit (binary processing), and Figure 11 shows the configuration of the black character correction circuit (dither processing). 12 is a diagram showing an example of a printer, FIG. 13 is a diagram showing the configuration of 208 shown in FIG. 12,
FIG. 14 is a block diagram showing the configuration of another embodiment of the achromatic color signal calculation circuit in the first ffl. l・・・・・・・・・・・・・・・・・・・・・・・・
......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...
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・Converter soj Figure 7 Breast level doubt j Constant circuit force / θ ) Condolence/4 Figure

Claims (8)

[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, and determining the target image based on the outputs of the first means and the second means. An image processing apparatus characterized by comprising: determination means for performing. (2) a first means for detecting a high frequency component of a target image; a second means for detecting a color component around a pixel of interest of the target image; based on the detection results of the first and second detecting means; 1. An image processing device comprising: determination means for determining characteristics of a target image. (3) The image processing apparatus according to claim (1) or (2), wherein the color component is a chromatic color or a component indicating a degree of chromatic color. (4) The image processing apparatus according to claim 1 or 2, wherein the determining means is a means for determining a character line drawing area and a halftone dot image area in the target image. (5) a discriminating means for discriminating a character part in a target color image to be formed; a color image forming means whose resolution can be switched; and a control means for controlling the resolution of the color image forming means based on the discrimination by the discriminating means; An image forming apparatus comprising: (6) The image forming apparatus according to claim 5, wherein the determining means is a means for determining a black character portion in a target color image. (7) The control means is a means for controlling the resolution to be higher when the character portion in the color image is discriminated by the discrimination means than when the character portion is not discriminated. The image forming apparatus according to item (5). (8) The image forming means includes modulation means for PWM modulating a given image signal in synchronization with a predetermined periodic signal, and the image forming means is means for controlling resolution by switching the frequency of the periodic signal. The image forming apparatus according to claim 5, characterized in that: