JP2002171404A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus that minimizes a quantity of an area separation setting table/filter setting table and can optimally separate areas even in the case of an original with a thin density. SOLUTION: In the image processing apparatus having an original read section that reads an original to generate input data, an area separation section that uses the input data to identify a character area, a photo area or a dot area of the original, a density conversion section that converts the density on the basis of the density conversion table that is preset for the input data, and a filter section that applies filter processing to each of areas separated by the area separation section on the basis of the filter setting table set in advance, the image data read by the original read processing (S1) are processed in the order of the density conversion processing (S4) and the area separation processing (S5) and then subjected to the filter processing (S6) when the conversion density is set darker, and the image data read by the original read processing (S1) are processed in the order of the area separation processing (S2) and the density conversion processing (S3) and then subjected to the filter processing (S6) when the conversion density is set rather thinner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a scanner, a digital copying machine, or a facsimile which identifies a character area, a photographic area, or a halftone dot area from an image obtained by scanning an original. The present invention relates to an image processing apparatus that performs an optimal filtering process according to the characteristics of each area.

[0002]

2. Description of the Related Art Conventionally, in a copying machine, a facsimile, or the like, areas such as a character portion and a photograph portion in a document are identified, and optimal image processing is performed on each region based on the identification result. JP-A-6-133159 discloses a configuration of an image processing apparatus that accurately detects a halftone dot region with a simple configuration. In this configuration, first, local changes in image data in the main scanning direction and the sub-scanning direction are respectively detected, and it is determined whether or not the detected value is a halftone area based on pixels having a predetermined value or more. The smoothing filter is used to prevent the occurrence of moire in the halftone dot area, while the MTF correction filter (edge emphasis filter) is used to sharpen the non-halftone area to obtain a sharp image. It has gained.

However, in performing area separation for identifying areas such as a character section and a photograph section in a document, there are the following problems depending on the position where the area separation is performed. That is, when performing the area separation after performing the density conversion by the exposure adjustment on the input data, it is necessary to have an area separation setting table and a filter setting table for each exposure curve,
These tables can be quite large, including settings by magnification. In addition, the actual setting requires much labor and time.

On the other hand, in the case of performing area separation before performing density conversion by exposure adjustment on input data, when the document is thin, the input data is also small, so that the edge detection of the character cannot be sufficiently performed and the character emphasis is increased. Sometimes it becomes blurred characters without being performed. If edge detection is set for a thin document in order to prevent this, there is a problem in that an edge-detected image other than characters will be emphasized.

[0005]

Accordingly, the present invention addresses these problems and minimizes the size of the area separation setting table and the filter setting table provided in the image processing apparatus, and can be applied to thin originals. It is an object to provide an image processing apparatus capable of performing optimal area separation.

That is, a first object of the present invention is to perform an area separation with a minimum necessary setting table without having an area separation setting table and a filter setting table for each density conversion table. And

A second object of the present invention is to perform optimal area separation according to the density of a document.

Further, a third object of the present invention is to correctly perform area separation even on a thin original and to perform an optimum filter process on characters.

[0009]

In order to solve the above problems, the present invention provides an image processing apparatus for an image forming apparatus.
A document reading unit that reads a document and generates input data, an area separating unit that identifies a character area, a photograph area, or a halftone area of the document using the input data, and a density conversion table that is set in advance for the input data. A density conversion unit that performs density conversion based on the density conversion unit, and a filter unit that performs a filter process based on a filter setting table that is set in advance for each area separated by the area separation unit, The processing order of the region separation unit can be switched.

Further, according to the present invention, in the above-mentioned image processing apparatus, there is provided a density selecting means for selecting a density conversion table of the density conversion section based on the density of the document, and the density conversion section is selected based on the selection signal. The processing order of the region separation unit is switched.

Further, according to the present invention, in the above-mentioned image processing apparatus, the processing in the area separating section and the density converting section is basically performed in the order of the area separating section and the density adjusting section. The processing is performed in the order of the density conversion unit and the area separation unit only when the color is set to be dark.

According to the present invention, in the above image processing apparatus, the selection of the conversion density by the density selection means is set to be dark when the document density is low, and is set to be low when the document density is high. did.

In order to solve the above problems, the present invention provides a document reading unit for reading a document and generating input data, and an area separating unit for identifying a character area, a photograph area, or a halftone area of the document using the input data. A density conversion unit for performing density conversion based on a density conversion table preset for input data; and a filter based on a filter setting table preset for each area separated by the area separation unit. An image processing method in an image processing apparatus having a filter unit for performing processing, wherein input data read by a document reading unit is subjected to density conversion processing and area separation when a density setting value of a density setting unit is set to be high. Processing is performed in the order of processing, and when the density setting value is set to be light, processing is performed in the order of the area separation processing and the density conversion processing, and then the filtering processing is performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on an embodiment shown in the drawings, but the present invention is not limited thereto. FIG. 1 is a schematic front sectional view showing a configuration of a digital color copying machine 1 which is an image forming apparatus to which an image processing apparatus according to an embodiment of the present invention is applied. A document table 111 and an operation panel are provided on the upper surface of the copying machine main body 1, and an image reading section 110 and an image forming section 210 are provided inside the copying machine main body 1. An automatic double-sided automatic document feeder (RADF; Recir) is supported on the upper surface of the platen 111 so as to be openable and closable with respect to the platen 111 and has a predetermined positional relationship with respect to the surface of the platen 111
curating Automatic Documente
nt Feeder) 112 is mounted.

Further, the two-sided automatic document feeder 112 includes:
First, the original is conveyed so that one side of the original faces the image reading section 110 at a predetermined position on the original platen 111, and after the image reading on this one side is completed, the other side is moved to the predetermined position on the original platen 111. Image reading unit 11 at position
The document is inverted and conveyed toward the document table 111 so as to face the document table 111. Then, after the two-sided image reading for one document is completed, the double-sided automatic document feeder 112 discharges this document and performs a double-sided conveyance operation for the next document. The above-described operations of conveying the document and reversing the front and back sides are controlled in relation to the operation of the entire copying machine.

The image reading section 110 is disposed below the document table 111 for reading an image of a document conveyed onto the document table 111 by the automatic duplex document feeder 112. The image reading unit 110 includes document scanning bodies 113 and 114 that reciprocate in parallel along the lower surface of the document table 111,
It has an optical lens 115 and a CCD line sensor 116 which is a photoelectric conversion element.

The original scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 114 has an exposure lamp for exposing the surface of the original image, and a first mirror for deflecting a reflected light image from the original in a predetermined direction. Are reciprocated in parallel at a predetermined scanning speed while maintaining the above distance. The second scanning unit 114 is the first scanning unit 113
A second mirror and a third mirror for further deflecting the reflected light image from the document deflected by the mirror in a predetermined direction, and reciprocating in parallel with the first scanning unit 113 while maintaining a constant speed relationship Things that move.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is.

The CCD line sensor 116 photoelectrically converts the formed light image sequentially and outputs it as an electric signal. The CCD line sensor 116 is a three-line color CCD that can read a black-and-white image or a color image and output line data separated into R (red), G (green), and B (blue) color components. . The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) to perform predetermined image data processing.

Next, the configuration of the image forming section 210 and the configuration of each section related to the image forming section 210 will be described. Below the image forming unit 210, there is provided a paper feed mechanism 211 that separates sheets (recording media) P stacked and accommodated in a sheet tray one by one and supplies the separated sheets to the image forming unit 210. The timing of the paper P separated and supplied one by one is controlled by a pair of registration rollers 212 disposed in front of the image forming unit 210, and the image forming unit 21.
Transported to zero. Further, the sheet P on which an image is formed on one side is re-supplied and conveyed to the image forming unit 210 in synchronization with the image formation of the image forming unit 210.

Below the image forming section 210, a transfer and transport belt mechanism 213 is disposed. The transfer / transport belt mechanism 213 is provided between the drive roller 214 and the driven roller 215 to extend substantially in parallel with the transfer / transport belt 21.
6, the paper P is electrostatically attracted and transported.

Further, a fixing device 217 for fixing the toner image transferred and formed on the sheet P to the sheet P downstream of the transfer and conveyance belt mechanism 213 in the sheet conveyance path.
Is arranged. The sheet P that has passed through the nip between the pair of fixing rollers of the fixing device 217 passes through a conveyance direction switching gate 218 and is discharged by a discharge roller 219 to a discharge tray 2 attached to an outer wall of the copying machine main body 1.
20 is discharged.

The conveyance direction switching gate 218 is used to move the conveyance path of the sheet P after fixing between a path for discharging the sheet P to the copying machine main body 1 and a path for re-supplying the sheet P to the image forming unit 210. To switch selectively. The image forming unit 210 is again operated by the conveyance direction switching gate 218.
The paper P whose transport direction has been switched toward is turned over via the switchback transport path 221 and then supplied again to the image forming unit 210.

In the image forming section 210, a first image forming station Pa, a second image forming station Pb, and a third image forming station are provided above the transfer conveyance belt 216 in close proximity to the transfer conveyance belt 216. P
c and a fourth image forming station Pd are arranged in order from the upstream side of the sheet transport path. The transfer conveyance belt 216 is frictionally driven by the drive roller 214 in the direction indicated by the arrow Z in FIG. 1, grips the sheet P fed through the sheet feeding mechanism 211 as described above, and transfers the sheet P to the image forming stations Pa to. Conveyed sequentially to Pd.

Each of the image forming stations Pa to Pd has substantially the same configuration. Each of the image forming stations Pa, Pb, Pc, and Pd is a photosensitive drum 222a, 222b, or 22 that is driven to rotate in the direction of arrow F shown in FIG.
2c. And 222d respectively.

Around the photosensitive drums 222a to 222d, chargers 223a, 223b, 223c, 22 for uniformly charging the photosensitive drums 222a to 222d, respectively.
3d and developing devices 224a and 224 for developing electrostatic latent images formed on the photosensitive drums 222a to 222d, respectively.
4b, 224c, 224d and transfer dischargers 225a, 225b, 225c, 225d for transferring the developed toner images on the photosensitive drums 222a to 222d to the paper P.
Cleaning devices 226a, 226b, and 2 for removing toner remaining on photoconductor drums 222a to 222d.
26c and 226d are photosensitive drums 222a to 222d.
Are sequentially arranged along the rotation direction.

Each of the photosensitive drums 222a to 222d
Above the laser beam scanner unit 227a,
227b, 227c, and 227d are provided, respectively.

Laser beam scanner units 227a-
227d, a semiconductor laser device (not shown) that emits dot light modulated in accordance with image data, a polygon mirror (deflecting device) 240 for deflecting a laser beam from the semiconductor laser device in the main scanning direction, and a polygon mirror The fθ lens 241 and the mirrors 242 and 243 for forming an image of the laser beam deflected by 240 on the surfaces of the photosensitive drums 222a to 222d.

The laser beam scanner 227a receives a pixel signal corresponding to the black component image of the color original image, and the laser beam scanner 227b receives a pixel signal corresponding to the cyan component image of the color original image.
A pixel signal corresponding to the magenta component image of the color original image is input to 7c, and a pixel signal corresponding to the yellow component image of the color original image is input to the laser beam scanner 227d.

As a result, the electrostatic latent images corresponding to the color-converted original image information are formed on the photosensitive drums 222a to 222d.
Formed on top. The developing device 224a includes the black toner, the developing device 224b includes the cyan toner,
The developing device 224c contains magenta toner, and the developing device 224d contains yellow toner. The electrostatic latent images on the photosensitive drums 222a to 222d are developed with the toners of these colors. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

A paper-suction (brush) charger 228 is provided between the first image forming station Pa and the paper feed mechanism 211. And the sheet feeding mechanism 211
The sheet P supplied from the first image forming station Pa is securely sucked onto the transfer / conveying belt 216.
To the fourth image forming station Pd without shifting.

On the other hand, a static eliminator 229 is provided almost directly above the drive roller 214 between the fourth image forming station Pd and the fixing device 217. An AC current is applied to the static eliminator to separate the paper P electrostatically attracted to the conveyor belt 216 from the transfer conveyor belt 216.

In the digital color copying machine having the above configuration, cut sheet-shaped paper is used as the paper P. The sheet P is sent out from the sheet cassette and fed to the sheet feeding mechanism 2.
When the paper P is fed into the guide of the paper feed conveyance path 11, the leading end of the paper P is detected by a sensor (not shown),
It is temporarily stopped by the pair of registration rollers 212 based on a detection signal output from this sensor.

Then, the paper P is fed onto the transfer / conveying belt 216 rotating in the direction of arrow Z in FIG. 1 at the timing of each of the image forming stations Pa to Pd. At this time, since the transfer conveyor belt 216 has been given a predetermined charge by the attraction charger 228 as described above, the paper P
While passing through each of the image forming stations Pa to Pd,
It is transported and supplied stably.

In each of the image forming image stations Pa to Pd, a toner image of each color is formed, and is superposed on the support surface of the paper P conveyed by being electrostatically attracted and conveyed by the transfer conveyance belt 216. When the transfer of the image by the fourth image forming station Pd is completed, the sheet P is sequentially separated from the transfer conveyance belt 216 by the discharging device from the leading end thereof, and is guided to the fixing device 217.
Finally, the sheet P on which the toner image is fixed is discharged onto a sheet discharge tray 220 from a sheet discharge port (not shown).

In the above description, the laser beam is scanned and exposed by the laser beam scanner units 227a to 227d, thereby performing optical writing on the photosensitive member. However, a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used instead of the laser beam scanner unit. L
The ED head is smaller in size than the laser beam scanner unit, has no moving parts, and is silent. Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

Next, the configuration and functions of an image processing section for color image information mounted on a color digital copying machine will be described with reference to FIG. FIG. 2 is a block diagram schematically showing a functional configuration of an image processing unit included in the color digital copying machine 1.

An image processing unit included in the digital copying machine 1 includes an image data input unit 40, an image processing unit 41, an image memory 43 including a hard disk device or a RAM (random access memory), and an image data output unit. Unit 42, central processing unit (CPU) 44, image editing unit 4
5 and external interface units 46 and 47.

The image data input unit 40 reads a monochrome document or a color document image, and can output three line color CCDs 40a capable of outputting line data separated into RGB color components, and line data read by the color CCD 40a. Correction circuit 40b for correcting the line image level of the color CCD 40a of three lines
A line matching unit 40c such as a line buffer for correcting a deviation of the image line data read by the sensor color correcting unit 40d for correcting the color data of the line data of each color output from the three-line color CCD 40a; An MTF correction unit 40e that corrects the change in the signal so as to have a sharp edge, and a γ that corrects the visibility by correcting the brightness of the image.
It comprises a correction unit 40f and the like.

The image processing section 41 includes an image data input section 40
A monochrome data generating unit 41a for generating monochrome data (black and white data) from RGB signals which are color image signals input from the printer, and converting the RGB signals into YMC signals corresponding to each recording unit of the recording apparatus, and performing density conversion An input processing unit 41b, an area separation unit 41c that separates whether the input image data is a character part, a halftone photograph, or a photographic paper photograph, and a lower color based on a YMC signal output from the input processing unit 41b Black generation unit 4 that performs a removal process to generate black
1d, a color correction circuit 41e for adjusting each color of a color image signal based on each color conversion table, a zoom processing circuit 41f for performing magnification conversion of input image information based on a set magnification, and a spatial filter 41g, multi-valued It comprises a halftone processing section 41h for expressing gradation such as error diffusion and multi-value dither.

Each color image data which has been subjected to halftone processing is temporarily stored in the image memory 43. The image memory 43 stores 8 bits and 4 colors (32 bits) serially output from the image processing unit 41.
4) hard disk (rotary storage medium) that sequentially receives image data of each bit, temporarily stores the data in a buffer, converts the 32-bit data into 8-bit 4-color image data, and stores and manages the image data for each color. 43a, 4
3b, 43c and 43d. Further, since the positions of the image forming stations are different, each color image data is temporarily stored in a delay buffer memory (semiconductor memory) 43e of the image memory 43, and the image data is sent to each laser scanner unit by shifting the time of each color image. Adjust the timing to prevent color shift. Further, the image memory 43 includes an image combining memory 43f for combining a plurality of images.

The image data output section 42 is provided with the halftone processing section 4
1h, a laser control unit 42a that performs pulse width modulation based on each color image data, and a laser scanner unit of each color that performs laser recording based on a pulse width modulation signal corresponding to an image signal of each color output from the laser control unit 42a (LSU) 42b, 42c,
42d and 42e.

A central processing unit (CPU) 44 controls an image data input section 40, an image processing section 41, an image memory 43, an image data output section 42, an image editing section 45 described later, and external interface sections 46 and 47. Is controlled based on the sequence.

The image editing unit 45 performs a predetermined image editing on the image data once stored in the image memory 43 via the image data input unit 40, the image processing unit 41, or an interface described later. The editing operation of the image data is performed using the image combining memory 43f.

Further, the external interface unit 46
It is a communication interface means for receiving image data from an external image input processing device (communication portable terminal, digital camera, digital video camera, etc.) provided separately from the digital copying machine 1.

The image data input from the external interface unit 46 is also input to the image processing unit 41 to perform color space correction and the like, so that the image data can be handled by the image forming unit 210 of the digital copying machine 1. Hard disk 43b, 43c, 43d, 43e
Will be stored and managed.

The external interface unit 47 is a printer interface for inputting image data created by the personal computer 2,
A black-and-white or color FAX interface for receiving received image data. The image data input from this interface 47 is already a CMYK signal,
Of the hard disks 43b, 43c, 43d, and 43e.

FIG. 3 is a diagram showing a state in which the operation of each part of the entire apparatus of the digital copying machine 1 is managed by a central processing unit (CPU) 44.

The image data input unit 40, the image processing unit 41,
The details of the image memory 43, the image data output unit 42, and the central processing unit (CPU) 44 are the same as those described with reference to FIG. 2 and will not be described here.

The central processing unit 44 manages the respective drive mechanisms constituting the digital copying machine 1 such as the RADF, scanner, laser printer and the like by sequence control, and outputs control signals to the respective units.

Further, an operation board unit 48 comprising an operation panel is connected to the central processing unit 44 in a mutually communicable state, and indicates the copy mode contents set and inputted by the operator in accordance with the operation of the operation panel. The control signal is transferred to the central processing unit 44 to control the entire digital color copying machine 1 to operate according to the set mode.

Also, control signals indicating various operating states of the digital color copying machine 1 are transferred from the central processing unit 44 to the operation board unit 48, and the operation board unit 48 side uses the control signals to operate the apparatus at present. The operating state is displayed on a display unit or the like so as to show the operator what state it is in.

The relationship between the area separation processing and the density conversion processing according to the present invention will be described below with reference to FIGS. First, the relationship between the operation of the area separation unit and the operation of the density conversion unit will be described with reference to FIG. 4, which is a flowchart schematically showing the flow of the area separation processing and the density conversion processing.

In the document reading section, a document reading process (S1) such as shading, line alignment, or the like is performed on data obtained by reading a document.
In the RGB image data, the order of the subsequent area separation processing and density conversion processing is switched according to the information of the density adjustment values (exp1 to exp7) set by the density selection unit.

Specifically, in the case of a light original such as one written with a pencil, the user sets the density adjustment value to dark eyes (exp5 to exp7) so that the original is printed dark. In this case, after performing the density conversion processing in the input processing unit (density conversion unit) (S4), the area separation unit performs the area separation processing (S4).
5) After that, the filter processing (S6) is performed by the filter processing unit including the spatial filter.

On the other hand, in the case of other originals, the user adjusts the density adjustment value to the normal value (exp4) or the lighter density (exp1 to exp1).
exp3). In this case, after performing the area separation processing in the area separation unit (S2), the density conversion unit performs the density conversion processing (S3), and then performs the filter processing (S6) in the filter processing unit including the spatial filter.

FIG. 5 shows an image obtained when a thin line pair image is read by a scanner on the left side, and data values of its cross section are shown on the right side. The upper side shows data before exposure adjustment, and the lower side shows data after exposure adjustment. As shown in the figure, as shown in the upper part, the read data obtained by capturing the image (original) by the scanner and before performing the exposure adjustment process is a light read data as a whole, and a difference in density is unlikely to appear. For this read data, as shown in FIG. 6, when the document density is low, exposure adjustment is performed using an exposure curve (exp5) in which a density adjustment value is set so that an output value becomes larger than an input value. By applying
As shown in the lower part, the density of the scanner read data can be increased, a difference in the density appears, and the edge is easily detected by the area separation processing.

Referring to FIG. 7, a description will be given of the processing result when the area separation processing is actually performed. In the figure, the upper part shows an image obtained by subjecting the scanner read data to area separation without performing exposure adjustment, and the lower part shows an image obtained by subjecting the scanner read data to area separation after performing exposure adjustment. Is shown. In the figure, the part displayed in gray is the area detected as an edge. In the upper image before the exposure adjustment, the edge detection such as the line pair of 7.1 is insufficient, and the detection of the line pair of 8.0 is inferior. , The edge detection of the line pair is greatly improved even at 8.0.

Based on the above segmentation results, an emphasis filter process as shown in FIG. 8A is performed on an area detected as an edge, and an area detected as a halftone portion is performed on an area detected as an edge. A smoothing filter process as shown in FIG.

[0060]

As described above, according to the present invention, the processing order of the density conversion processing in the density conversion section and the area separation processing in the area separation section is switched, and the area separation processing is performed on a document having a high density. After applying the density conversion process to the original document with low density, the density conversion process is first performed and then the region separation process is performed, so that the area separation process can be performed even for the original document with low density. It is not necessary to have an area separation setting table and a filter setting table for each density conversion table, and the number of area separation setting tables and filter setting tables can be reduced, and the setting labor of the tables can be reduced. it can.

Further, according to the present invention, by switching the processing order of the density conversion section and the area separation section based on the density conversion table selection signal of the density selection means, the optimum area separation adapted to the density of the document can be achieved. Then, the best image quality can be obtained by applying the optimum filter.

Further, according to the present invention, the area is separated after the density conversion by the density selecting means only when the density is set to a darker level, so that a thin document can be reliably detected and a sharp image can be obtained. Reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a front sectional view illustrating the structure of a digital color copying machine to which an image processing apparatus according to the present invention is applied.

FIG. 2 is a block diagram of an image processing unit included in the digital color copying machine of FIG. 1;

FIG. 3 is a block diagram of the digital color copying machine shown in FIG.
FIG. 4 is a state diagram in which operations are managed by U.

FIG. 4 is a flowchart illustrating a relationship between a region separation process and a density conversion process according to the present invention.

FIG. 5 is a view for explaining image data before and after exposure adjustment.

FIG. 6 is a diagram showing an example of an exposure adjustment curve.

FIG. 7 is a view for explaining results of area separation before and after exposure adjustment.

FIG. 8 is a diagram illustrating an example of a filter coefficient.

[Explanation of symbols]

Reference Signs List 1 digital color copier 40 image data input unit 40a color CCD 40b shading correction circuit 40c line alignment unit 40d sensor color correction unit 40e MTF correction unit 40f γ correction unit 41 image processing unit 41a monochrome data generation unit 41b input processing unit 41c area separation Unit 41d Black generation unit 41e Color correction circuit 41f Zoom processing circuit 41g Spatial filter 41h Halftone processing unit 42 Image data output unit 42a Laser control unit 42b-e Laser scanner unit for each color 43 Image memory 43a-d Hard disk (rotary storage medium) 43e Delay buffer memory (semiconductor memory) 43f Image synthesis memory 44 Central processing unit (CPU) 45 Image editing unit 46, 47 External interface unit 48 Operation board unit 110 Image reading 111 Platen 112 Image Automatic Document Feeder 113, 114 Document Scanning Body 115 Optical Lens 116 CCD Line Sensor 210 Image Forming Unit 211 Paper Feeding Mechanism 212 Registration Roller 213 Transfer Conveying Belt Mechanism 214 Driving Roller 215 Driven Roller 216 Transfer Conveying Belt 217 Fixing Device 218 Transport direction switching gate 219 Discharge roller 220 Discharge tray 221 Switchback transport path 222a to 222d Photoconductor drum 223a to 223d Charger 224a to 224d Developing device 225a to 225d Transfer discharger 226a to 226d Cleaning device 227a to 227d Laser beam Scanner unit (LSU) 228 Paper suction charger 240 Polygon mirror 241 fθ lens 242 to 243 Mirror P Paper Pa to Pd Image Forming station

Continued on the front page (72) Inventor Norio Tomita 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Ayumu 22-22 Nagaikecho, Nagano-cho, Abeno-ku, Osaka-shi Inside Sharp Corporation (72) Inventor Shoichi Fukudome 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka, Japan (72) Inventor Yuki Manabe 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (Reference) 5B057 AA11 CA06 CA07 CA08 CA12 CB06 CB07 CB08 CB12 CE06 CE11 CH18 DB02 DB08 DB09 5C077 LL17 MP02 MP06 PP01 PP15 PP27 PP43 PQ08 PQ23 TT06

Claims (5)

[Claims] An original reading section for reading an original and generating input data, an area separating section for identifying a character area, a photograph area or a halftone area of the original using the input data, A density conversion unit that performs density conversion based on the obtained density conversion table, and a filter unit that performs filter processing based on a filter setting table that is set in advance for each area separated by the area separation unit, An image processing apparatus, wherein the processing order of the density conversion unit and the region separation unit can be switched. 2. A density selecting unit for selecting a density conversion table of the density conversion unit based on a density of a document, and switching a processing order of the density conversion unit and the area separation unit based on the selection signal. The image processing apparatus according to claim 1, wherein: 3. The order of processing in the area separating section and the density converting section is basically such that the processing is performed in the order of the area separating section and the density adjusting section, and only when the density is set to a high level by the density selecting means. 3. The image processing apparatus according to claim 2, wherein the processing is performed in the order of: a density converter; 4. The selection of the conversion density by the density selection means,
4. The image processing apparatus according to claim 3, wherein the image processing apparatus is set to be dark when the document density is low, and is set to be low when the document density is high. 5. An original reading section for reading an original and generating input data, an area separating section for identifying a character area, a photograph area or a halftone area of the original using the input data, Image processing comprising: a density conversion unit for performing density conversion based on a density conversion table obtained by the image processing unit; and a filter unit for performing filter processing based on a preset filter setting table for each area separated by the area separation unit. An image processing method in an apparatus, wherein input data read by a document reading unit is processed in the order of a density conversion process and a region separation process when a density setting value of a density setting unit is set to be high, and the density setting value is An image processing method characterized in that when it is set to be thin, processing is performed in the order of area separation processing and density conversion processing, and then filtering processing is performed.