JP2002064717A - Color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming apparatus that applies image processing, suitable for respective image areas to an original where a black/ white image and a color image are mixed. SOLUTION: The color image forming device has plural image area separation means (a photographing area discriminating circuit 31, a character area discriminating circuit 32, a dot area discrimination circuit 33 and a color discriminating circuit 34) that separate original data into the character area and the photographing area. A color mode is designated for each separated area. The configuration of the image area separation means 31, 32, 33, 34 used for the area separation is changed between a full color mode and a black/white mode. A space filter processing section 70, a color correction processing section 80, and a gradation processing section 90 apply reproduction processing, with emphasis on the resolution to the character area and apply reproduction with emphasis on the gradation to the photographing area according to the selected image area separation means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus suitable for use in an image forming apparatus such as a digital color copying machine or a color facsimile which forms an image in a full color mode and a monochrome mode. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Generally, in a digital copying machine,
An original image is read for each pixel using a CCD (charge coupled device) image sensor or the like, and an analog electric signal obtained at the output of the image sensor is converted from analog to digital (A / D) to a digital signal obtained. After performing various processes, the signals are given to a recording device to obtain a copy image. Photographs, halftone dots,
It is known that, in the case where a character and a line drawing part are mixed, in order to obtain a high-quality copy image, these image regions are automatically separated, and optimal processing is performed according to each image.

FIG. 7 is a main block diagram for explaining an example of a conventional black-and-white digital copying machine. For example, the "image area identification apparatus" disclosed in Japanese Patent No. 2617469 is a case of a black-and-white copying machine, but, as shown in FIG. Separation is performed, and a non-photograph and non-dot area is set as a “character area”, and a processing emphasizing resolution such as edge emphasis + simple binarization processing is performed.
It is configured to perform processing emphasizing gradation by smoothing + dither processing.

FIG. 13 is a main block diagram for explaining an example of a conventional color digital copying machine.
The "color image processing apparatus" disclosed in Japanese Patent Application Laid-Open No. 5-48892 is a case of a color copier, but as shown in FIG. The image data is divided into regions, and the character region and the non-halftone dot region are regarded as “character regions”, and a process emphasizing resolution is performed. In the "character area", if the color determination is an achromatic area, the parameters of UCR (under color removal: under color removal) processing can be changed so that the image is formed as a "black character area" using a single black color. It is configured as follows.

[0005] Here, both (the above-mentioned Patent No. 2,617,469)
And the algorithm of image area separation described in Japanese Patent Application Laid-Open No. Hei 5-48892. FIG. 8 is a main block diagram showing an example of the photograph area determination circuit shown in FIG. FIG. 9 is a diagram showing an example of a pattern mask for detecting a photographic region in the example shown in FIG. In the former (the above-mentioned Japanese Patent No. 2617469), "photograph area determination" for separating a character area and a photograph area is performed using a circuit as shown in FIG. The binarization circuit 151 binarizes the input image data with a relatively low level threshold value, and converts the input image data into six FIFOs (first-in first-out).
When all the pixels corresponding to the pattern mask shown in FIG. 9 are black pixels having a density equal to or higher than a predetermined threshold value, the target pixel (the pixel corresponding to the FF 44) using the memories 1 to 6 and the flip-flops FFs 14 to 77. Is determined to be a photograph area. This is based on the feature that a character image is a black character on a white background, and a photographic image is a series of pixels having a density higher than a certain level. In this method, a photographic area is not detected in a background area having a density equal to or lower than a predetermined density or in a density area close to the background, and thus is determined as a “character area”. Therefore, even in the case of a photographic original, a highlight portion having a density equal to or lower than a predetermined density is not determined as a photographic region.

FIG. 14 is a main block diagram showing an example of the character area determination circuit shown in FIG. FIG. 15 is a diagram showing an example of a pattern matching template in the example shown in FIG. The latter (Japanese Patent Laid-Open No.
No. 8892), "character area determination" for separating a character area from a photograph area is performed using a circuit as shown in FIG. Here, for data obtained by binarizing image data with a relatively high level threshold (THW),
A white edge is detected using the templates shown in the patterns 1 to 8 shown in FIG. 15, and when, for example, two or more edge patterns are detected in a region of about 3 × 3 in the counting circuit, “ White edge area ". Similarly, for data binarized with a relatively low level threshold (THB), a black edge is detected using the templates shown in patterns 9 to 16 shown in FIG. When a predetermined number or more of black edges are detected, a "black edge area" is determined. Then, a region where the white edge region and the black edge region overlap with each other is expanded by the character region determination unit 248 to be a character region. This is a detection method based on the feature that a character on a white background has a sharp change in density, and a portion where white pixels are continuous (white edge) is adjacent to a portion where black pixels are continuous (black edge).

According to this method, the black area is not detected in a background area having a density equal to or lower than a predetermined density or in a density area close to the background, so that it is determined that "non-character area" = "photograph area". In particular, in the case of a character having a relatively low density, such as a pencil-written character with a weak writing pressure, a black edge is difficult to be detected, and thus it may not be determined as a “character area”. Conversely, in a low-density region such as a highlight portion of a photographic document, no black edge is detected, and thus the region is determined to be a photographic region.

[0008] As described above, in the black-and-white machine, the quality of a character image including a character written in a pencil is rather emphasized, and in the full-color machine, the reproducibility of a photographic image including highlights is emphasized. I have. However, even full-color machines do not always copy in full color.
In the case of a black-and-white document, there is a case where copying is performed using a low-cost monochromatic black.

Some originals include a mixture of color and black-and-white images created by cutting and pasting a color image and a black-and-white image. In this case, the operator determines whether the copy image quality of the color original or the black-and-white original is prioritized, and selects the color mode to copy.
At this time, there is a problem that the reproducibility of an image suitable for the color mode not selected is sacrificed.

[0010]

SUMMARY OF THE INVENTION An object of the first invention is to provide a color image forming apparatus capable of performing image processing suitable for each image area on a document in which a monochrome image and a color image are mixed. Is to provide.

An object of the second invention is to provide a color image forming apparatus according to the first invention, which emphasizes the reproducibility of a low-density character image such as a pencil original, particularly for a black-and-white image. .

A third object of the present invention is to provide a color image forming apparatus according to the first invention, which can change an image to be emphasized for a full-color image and a monochrome image as desired.

A fourth object of the present invention is to provide a color image forming apparatus according to the first to third inventions, which can reproduce a photographic original satisfactorily.

A fifth object of the present invention is to provide a color image forming apparatus according to the first to third inventions, which can reproduce a pencil original satisfactorily.

[0015]

According to a first aspect of the present invention, an original is separated into R (red), G (green), and B (blue) colors and digitally read, and image data of the read original is read out. A full color mode in which a color image is reproduced digitally using color materials of Y (yellow), M (magenta), C (cyan), and K (black), and an image is reproduced in a single color of K from the image data. In a color image forming apparatus having a monochrome mode, a plurality of image area separating means for separating document data into a character area and a photograph area; a color mode specifying means for specifying a color mode for each of the separated areas; Change the configuration of the image area separating means used for the area separation between the mode and the black and white mode,
Image processing means for performing reproduction processing with emphasis on resolution in the character area according to the result of the selected image area separation means, and performing reproduction processing with emphasis on gradation in the photographic area;
An image is formed by changing the configuration of the image area separating means in accordance with the color mode specified for each of the areas.

According to a second aspect of the present invention, in the first aspect of the present invention, the image area separating means used in the area designated in the full color mode determines a background area or a density area close to the background area as a photographic area, The image area separating means used in the area designated as (1) determines the background or the density area close to the background as a character area.

According to a third aspect of the present invention, in the first aspect of the invention, the configurations of the image area separating means used in the full color mode area and the image area separating means used in the black and white mode area can be independently changed. It is characterized by.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the image area separating means for determining the background area or the density area close to the background area as a photographic area is based on the presence or absence of edge information. Is performed.

According to a fifth aspect of the present invention, in any one of the first to third aspects of the present invention, the image area separating means for determining the background area or the density area close to the background area as the character area is based on the continuity or density of the colored pixels. The above-mentioned determination is performed by using

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a main block diagram for explaining an embodiment of a color image processing apparatus according to the present invention. A photograph area determining circuit 31 and a character area determining circuit 32 as image area separating means are shown. In the image area separation unit 30 including a halftone area determination circuit 33, a color determination circuit 34, and a comprehensive determination circuit 35 that comprehensively determines from the image area separation results,
The image area is determined, and the spatial filter processing unit 70, the color correction processing unit 80, and the gradation processing unit 90 are configured to select appropriate image processing.

An area designating means for dividing a document into a plurality of areas has a digitizer 61 for storing divided area information and color mode information for each divided area inputted from the operation unit 62. It has an information storage circuit 40. At the time of the copy operation, the area designation information storage circuit 40
A color mode selection signal is issued for each of the divided areas as the area designation information.

Here, as the photographic area determination circuit 31, the photographic area determination circuit for a black-and-white machine described in the above-mentioned prior art is used to determine an area near the background density level of highlight as a non-photographic area. As the character area determination circuit 32, a character area determination circuit for a color machine is used.
The background density level is determined to be a non-character area.

Next, the halftone area determination circuit 33 will be described. FIG. 10 is a circuit diagram showing the halftone dot determination circuit 160 shown in FIG.
FIG. 4 is a main part block diagram showing an example of the above. FIG.
FIG. 7 is a diagram showing an example of a halftone dot detection pattern in the example shown in FIG. FIG. 12 is a diagram for explaining an example of a method of determining a halftone dot region in the example shown in FIG. The halftone dot determination can be used in both the full color mode and the black and white mode. The example shown in FIG. 10 is the method disclosed in Japanese Patent No. 2,617,469. In the binarization circuit 161, the image data is binarized at an appropriate density level, pixels having a density higher than a predetermined threshold are set as black pixels, and pixels having a lower density are set as white pixels, using the template shown in FIG. Halftone dots of various sizes are detected by the pattern matching method. The determination of the halftone dot region is made based on whether a halftone dot is detected in a certain area. In order to increase the determination accuracy, three-stage area determination is performed. This determination will be described with reference to FIG.

In the first stage, an area (E
If a halftone dot is detected within 1 (first area), it is determined to be a halftone dot region. Hereinafter, the first area composed of 8 × 8 pixels is 1
Judge as one unit. However, what is determined here is the E1 block. Next, in the second stage, if three or more blocks among the four adjacent first areas (E1 to E4) are halftone areas in the first determination, they are determined to be halftone areas. Further, in the third stage, in one of the four first areas (E1, E2, E5, E6) connected in the main scanning direction, if one or more blocks are halftone areas in the second determination, the halftone area is determined. . The result of the determination in the third stage is finally determined to be a dot area. Note that, here, the halftone dot detection was performed by the pattern matching method for the binary data. However, for the multivalued data of 3 × 3 pixels, the center pixel is compared with the four adjacent pixels or the eight adjacent pixels, A method of judging whether the level is lower (valley peak) or higher than the level (peak) and detecting an extreme value (peak) may be used.

Next, the color determination circuit 34 will be described.
FIG. 16 is a main block diagram showing an example of the color determination circuit 260 shown in FIG. 13. By using this image area separating means in the full color mode, black characters can be reproduced in high quality with a single black color. it can. Here, it is determined whether a certain pixel is achromatic or chromatic. The achromatic pixel focuses on the fact that the levels of the R, G, and B data are uniform, and the difference ΔRGB between the R, G, and B data, that is, max (R, G, B) −min (R, G, B) ) Is detected as an achromatic pixel when is smaller than a predetermined value. When the number of detected achromatic pixels is equal to or more than a predetermined number in an area of about 3 × 3 pixels, the counting section 263 determines that the area is an achromatic area.

Next, an image processing circuit for reproducing an image will be described. As shown in FIG. 1, it includes a spatial filter processing unit 70, a color correction processing unit 80, and a gradation processing unit 90. The spatial filter performs a smoothing process on a halftone dot image to prevent the occurrence of moire, and performs an edge enhancement process on an image that requires resolution, such as a character or a line drawing. In the case of a photographic image that is a continuous tone image, strong smoothing is not required as in the case of a halftone image, but the image becomes noisy and rough even if edge enhancement is applied too strongly, such as a character image. Depending on the preference, it may be selected from weak smoothing through (no filtering) or weak edge enhancement processing.

In the full-color mode, the color correction processing section 80 corrects the distortion of the color separation characteristics of the scanner and the deviation of the spectral characteristics of the color materials used in the printer from the ideal, and performs masking for ensuring appropriate color reproducibility. Circuit 81 and Y, M, C
UCR for replacing the equivalent part of
A color removal (under color removal) circuit 82 is provided. The masking circuit 81 is normally calculated in the form of a linear combination of R, G, and B data, such as X = a × R + b × G + c × B + d (X = Y, M, C). Here, the coefficients a, b, c, and d are Y,
M and C are different from each other. The UCR circuit 82 calculates as X ′ = X−min (Y, M, C) × α (X = Y, M, C). Here, the coefficient α indicates the UCR rate, which is a case where 100% is full black, and among the overlapping portions of Y, M, and C, the portion replaced by K is replaced by K.

In an image such as a photograph or a halftone dot image where importance is placed on gradation, setting the UCR rate to 100% eliminates the color depth and gives a blackish impression. To do. Conversely, in the case of a character image, particularly a black character image, if the Y, M, and C color components remain, the reproduced image becomes thicker, and if there is a shift between the color plates, the color becomes blurred and the image quality deteriorates. I do. Therefore, for character images, the UCR rate is set to 100%. Further, this circuit not only sets the UCR rate to 100% for a black character image, but also has a function of positively converting the data of the color components Y, M, and C to 0. Only to be reproduced.

The last gradation processing section 90 performs pseudo halftone processing on a photograph or a halftone dot image using a dot concentration type dither pattern in order to secure the number of gradations and stabilize the gradation. Further, simple binarization processing is performed on an image, such as a character or line drawing image, where importance is placed on resolution without performing dither processing. Here, the case where the printer can reproduce only a binary level of white or black per dot has been described. However, when multi-value output such as ternary to 256 values is possible, instead of simple binarization, It is also possible to use a simple multi-value processing or a processing that leaves a certain degree of gradation by using a dot-dispersion type dither pattern. Further, if the processing by the error diffusion method is used as the gradation processing emphasizing the gradation property, moire for the halftone dot image is reduced, so that it is not necessary to perform strong smoothing processing in the spatial filter processing, and It can be shared with filter processing.

Here, the overall judgment of the result of the image area separation processing will be described. FIG. 2 is a table showing a state of the comprehensive judgment when the color mode selection is the full color mode in the embodiment shown in FIG. In FIG. 1, a comprehensive judgment circuit 3
5, five types of area determination signals are input, and an area determination signal to be used is selected according to the color mode selection signal.
Here, the character area determination circuit 32 is used to separate the character area from the photo area, and the photo area determination circuit 31 is not used. Therefore, the photographic area determination signal is “x” (Don't care). At the top, an image area determined by a combination of area signals is shown. In the spatial filter processing, a smoothing processing (filter 1) is selected for the halftone dot area,
An edge enhancement process (filter 3) is selected for the character region, and an intermediate filter process (filter 2) is selected for the photograph region. However, character area signal =
In the case of 1 and the halftone area signal = 1, the halftone area signal is prioritized, and it is determined that it is a halftone area. In the UCR process, a UCR rate of 100% is selected only for the character area,
Further, in the case of an achromatic region, that is, in the case of a black character region, output of color components is prohibited. In other areas, low U
Selects the CR rate and does not inhibit output of color components. In the gradation processing, simple binarization processing is selected only for the character area, and dither processing is selected for the photograph and halftone dot areas.

FIG. 3 is a table showing a state of comprehensive judgment when the color mode selection is the monochrome mode in the embodiment shown in FIG. Here, the photograph region determination circuit 31 is used for separating the character region and the photograph region, and the character region determination circuit 32 is not used. Therefore, the character area signal is “×” (Don't ca
re). In the black-and-white mode, an achromatic color area signal is not required, so that it is “×” (Don't care). Here, when the photographic area signal = 1 and the halftone area signal = 1, the photographic area signal is given priority and determined as a photographic area. As for the selection of the spatial filter, the filter 1 is selected for the halftone dot region, the filter 3 is selected for the character region, and the filter 2 is selected for the photograph region, as in the case of the full color. In the black-and-white mode, since the UCR processing is unnecessary, this circuit is set to be through. Finally, in the gradation processing, simple binarization processing is selected only in the character mode, and dither processing is selected for photographs and halftone dot areas.

FIG. 4 is a main block diagram for explaining another embodiment of the color image processing apparatus according to the present invention.
FIG. 5 is a table showing a state of the comprehensive judgment when the priority document selection is a character document in the full-color mode in the embodiment shown in FIG. FIG. 6 is a table showing a state of the comprehensive judgment when the priority original is selected as a photo original in the monochrome mode in the embodiment shown in FIG. In the example shown in FIG.
The overall judgment of the image area separation processing result can be changed by the priority original selection signal. The priority document selection signal is to give priority to the reproducibility of a text document even in the full color mode, to the reproducibility of a photo document, or to the reproducibility of a photo document in the black and white mode. , A selection signal for giving priority to a text document. Based on the priority document selection value, an image area separation circuit for determining whether to use a character area or a photograph area is selected.

FIG. 2 corresponds to a case where the priority document selection is a photo document in the full color mode. FIG.
Corresponds to a case where the priority document selection is a character document in the monochrome mode. FIG. 5 shows how the overall determination is made when the priority document selection is a text document in the full-color mode. Here, a photograph area determination circuit 31 is employed as a circuit for separating a character area from a photograph area.
Similarly, FIG. 6 shows a state of the overall judgment when the priority original is selected as a photo original in the black and white mode. The character area judgment circuit 32 is employed as a separation circuit for a character area and a photograph area. I have. By employing the priority document selection function in this way, the image quality can be adjusted according to the user's preference.

[0034]

As is clear from the above description, (1) In the first aspect of the present invention, an original is separated into R (red), G (green), and B (blue) and read digitally. From the read image data, Y (yellow), M
A color image having a full-color mode for digitally reproducing a color image using (magenta), C (cyan), and K (black) color materials, and a black-and-white mode for reproducing an image in K color from image data. In the forming apparatus, the configurations of a plurality of image area separating means for separating the original data into a character area and a photograph area and the image area separating means used in the full color mode and the black and white mode are changed, and the result of the selected image area separating means is changed. Image processing means for performing reproduction processing with emphasis on resolution in the character area and reproduction processing with emphasis on gradation in the photographic area, and means for dividing the document into a plurality of areas and designating at least a color mode for each of the divided areas And the configuration of the image area separating means is changed in accordance with the color mode assigned to the area to form a copy image. The document to be mixed, it is possible to provide a color image forming apparatus amenable image processing suitable for respective image regions.

(2) In the invention according to claim 1, in the invention according to claim 1, in the original area in which the full-color mode is designated, the background or a density area close to the background is determined as the photograph area, and the monochrome mode is designated. Since the density area is determined to be a character area in the original area, a color image forming apparatus that emphasizes the reproducibility of a low-density character image such as a pencil original, particularly in a monochrome original area, is provided. Can be.

(3) The invention according to claim 3 is such that, in the invention according to claim 1, the configurations of the image area separating means used for the full color mode area and the image area separating means used for the black and white mode area can be independently changed. With this configuration, the image to be emphasized can be changed in the full-color mode area and the black-and-white mode area according to preference.

(4) A fourth aspect of the present invention, according to the first to third aspects of the invention, is configured to detect the presence or absence of edge information as image area separating means for determining a background area or a density area close to the background area as a photographic area. Therefore, the photographic document can be reproduced well.

(5) According to the invention of claim 5, in the invention of claims 1 to 3, the continuity or density of the colored pixels is detected as an image area separating means for determining a background area or a density area close to the background area as a character area. With such a configuration, a pencil manuscript can be satisfactorily reproduced.

[Brief description of the drawings]

FIG. 1 is a main block diagram for explaining an embodiment of a color image processing apparatus according to the present invention.

FIG. 2 is a table showing a state of comprehensive judgment when a color mode selection is a full color mode in the embodiment shown in FIG. 1;

FIG. 3 is a table showing a state of an overall judgment when a color mode selection is a monochrome mode in the embodiment shown in FIG. 1;

FIG. 4 is a main part block diagram for explaining another embodiment of the color image processing apparatus according to the present invention.

FIG. 5 is a table showing a state of a comprehensive determination when priority document selection is set to a text document in the full-color mode in the embodiment shown in FIG. 4;

FIG. 6 is a table showing a state of a comprehensive determination in a case where priority document selection is set to a photo document in the monochrome mode in the embodiment shown in FIG. 4;

FIG. 7 is a main block diagram for explaining an example of a conventional monochrome digital copier.

FIG. 8 is a main block diagram illustrating an example of a photograph area determination circuit illustrated in FIG. 7;

9 is a diagram illustrating an example of a pattern mask for detecting a photographic area in the embodiment illustrated in FIG. 7;

10 is a main part block diagram illustrating an example of a halftone dot area determination circuit illustrated in FIG. 7;

FIG. 11 is a diagram illustrating an example of a halftone dot detection pattern in the example illustrated in FIG. 7;

12 is a diagram illustrating an example of a method of determining a halftone dot region in the example illustrated in FIG. 7;

FIG. 13 is a main part block diagram for explaining an example of a color digital copying machine according to the related art.

FIG. 14 is a main part block diagram illustrating an example of a character area determination circuit illustrated in FIG. 13;

FIG. 15 is a diagram illustrating an example of a pattern matching template in the example illustrated in FIG. 13;

FIG. 16 is a main block diagram showing an example of a color determination circuit shown in FIG. 13;

[Explanation of symbols]

10, 110, 210 ... scanner, 20, 220 ... delay memory, 30, 140, 230 ... image area separation unit, 31, 1
50: photo area determination circuit, 32, 240: character area determination circuit, 33, 160, 250: halftone area determination circuit, 3
4,260: color judgment circuit, 35,270: comprehensive judgment circuit, 40: area designation information storage circuit, 50: CPU, 60
... Pressing plate, 61 ... Digitizer, 62 ... Operation unit, 120,2
80 spatial filter processing unit, 121, 281 smoothing processing unit, 122, 282 edge enhancement processing unit, 130, 3
00: gradation processing unit, 131, 301: dither processing unit, 1
32,302... Simple binarization processing unit, 151,161,2
41, 244... Binarization circuit, 152, 247.
162: pattern matching section, 163, 164, 16
5 halftone area determination unit, 170 OR, 180, 283
303 ... selector, 190, 310 ... printer, 242
... White edge detectors, 243, 246, 263.
245: black edge detection unit, 248: character area judgment, 26
1 ... ΔRGB calculation circuit, 262… Achromatic pixel detection circuit,
264: achromatic region determination unit, 290: color correction processing unit, 2
91: Masking circuit, 292: UCR circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H027 EB02 EB04 FA28 FA35 2H030 AA02 AD07 AD12 AD14 5C077 MP02 MP05 MP06 MP08 NN08 NN19 PP02 PP03 PP27 PP28 PP32 PP33 PP38 PP43 PP47 PP55 PQ08 PQ17 RR02 SS05 TT06 5C079 HA13 H13H03B LA21 LA31 LA34 LB15 LC04 MA19 NA04 NA05 PA01 PA02 5L096 AA02 AA06 FA06 FA44 FA45 GA55

Claims (5)

[Claims] An original is composed of R (red), G (green),
Color separation into B (blue) is performed and digitally read, and digitally converted from image data of the read original using Y (yellow), M (magenta), C (cyan) and K (black) color materials. In a color image forming apparatus having a full-color mode for reproducing a color image and a black-and-white mode for reproducing an image in a single color of K from the image data, a plurality of image area separations for separating document data into a character area and a photograph area Means, a color mode specifying means for specifying a color mode for each of the separated areas, and a configuration of the image area separating means used for the area separation between a full color mode and a black and white mode. According to the result of the separating means, the character area is subjected to a reproduction process emphasizing resolution,
And image processing means for performing reproduction processing with emphasis on gradation in the photographic area, and forming an image by changing the configuration of the image area separating means in accordance with the color mode specified for each area. Characteristic color image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein the image area separating means used in the area designated in the full color mode determines a background area or a density area close to the background area as a photographic area, The image area separating means used in the area designated in (1) determines the background or the density area close to the background as a character area. 3. The color image forming apparatus according to claim 1, wherein a configuration of an image area separating unit used in the full color mode area and an image area separating unit used in the black and white mode area can be independently changed. A color image forming apparatus. 4. The color image forming apparatus according to claim 1, wherein said image area separating means for determining a background area or a density area close to the background area as a photograph area is based on the presence or absence of edge information. A color image forming apparatus. 5. The color image forming apparatus according to claim 1, wherein the image area separating unit that determines a background area or a density area close to the background area as a character area is based on continuity or density of the colored pixels. A color image forming apparatus, wherein the determination is made by using