JPH08251406A - Image forming device - Google Patents

Abstract

PURPOSE: To reduce the image processing time by discriminating to which of nine kinds of images such as a line drawing, a half tone image a continuous tone image, and their combinations an input image corresponds and selecting automatically the image processing suitable for the input image based on the result of discrimination. CONSTITUTION: An image scanner 400 provides the output of R, G, B image data. An image separation device 76, an image type discrimination device 77 and a system controller 50 discriminate input image data equipment to one page obtained by preliminary scanning to be made up of only a line drawing, only an intermediate tone image, only a continuous tone image, a line drawing and an intermediate tone image, a line drawing and a continuous tone image, an intermediate tone image and a continuous tone image, or a line drawing and an intermediate tone image and a continuous tone image in total nine ways. The system controller 50 is available of the nine ways of arithmetic systems and designates a processing mode corresponding to any of the nine ways of images through a filter 71, a color correction device 72, a selector 73 and a gradation processing circuit 74. Thus, the operator is relieved from the trouble of mode changeover and an excellent reproduced image is obtained in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image signal processing in an image processing apparatus such as a digital copying machine.

[0002]

2. Description of the Related Art In recent years, digital color image forming apparatuses have been remarkably improved in function, and the image type (line image / halftone image) is automatically determined for each fine region of an input image and the image is reproduced by switching the calculation. Not only the image quality but also the gradation of halftone images and the resolution of line drawings are improved. The image calculation mode at this time is called a halftone automatic separation mode, and the image calculation method is switched and used for each fine region. Therefore, in the case of an image in which a line image and a halftone or continuous tone image are mixed, the determination of the fine area is not always performed 100% correctly, but a substantially good reproduced image can be obtained. You can However, significant image deterioration is recognized at the erroneously determined portion.

In order to determine the image type on the original,
Image input (for example, an operation called prescan in a copying machine) may be performed, and image processing corresponding to the image type may be performed in the next second image input based on the determination result. This results in the document being scanned once, which increases the time from the start to the end of image reading.

[0004]

Therefore, the original image is
When only one of line drawing, halftone (printing) image, and continuous tone (photograph) image is selected, the operator preliminarily selects which operation is to be used for line drawing, halftone image, or continuous tone image. As a result, the reproducibility of the original image is high. However, this is a very troublesome task for the operator. In order to avoid the troublesomeness of the operator to switch the mode in this way, in Japanese Patent Laid-Open No. 4-207760, an image data processing method is adopted in which the size and density of characters are judged in a facsimile machine. Although an automatic setting is disclosed, this is limited to a character image and does not correspond to a halftone image or a continuous tone image. Further, although it has already been possible to automatically determine whether the input image is color or black and white and switch the color mode for each page, the image calculation mode is not switched.

According to the present invention, there is no need to increase the troublesomeness of selecting an image forming mode in a digital image forming apparatus.
The first purpose is to perform image processing more suited to the type of input image, such as line drawing mode, halftone mode, and continuous tone mode, as well as the automatic halftone separation mode. A second object is to shorten the time required for processing.

[0006]

Means for Solving the Problems Input means for inputting an image signal, means for performing an operation to embody the input image signal, and the arithmetic means is a first operation suitable for embodying a line drawing. A method or parameter, a second computing method or parameter suitable for embodying a halftone image, and a third computing method or parameter suitable for embodying a continuous tone image, respectively. Have one or more types, these in the image of one page,
Only the first operation is used, only the second operation is used, only the third operation is used, the first and second operations are switched and used, the first and third operations are switched and used, and Nine different calculation methods of switching and using the second and third calculations, and switching and using the first, second and third calculations, and means for selecting which of these methods is adopted, One page of input image data
Data, only line drawing, half tone only, continuous tone only, line drawing and half tone, line image and continuous tone, half tone and continuous tone, line image and half tone and continuous It is characterized by further comprising: a page image type determination means for determining which one of the nine key types, and a means for determining the selection of the selection means according to the determination result.

[0007]

In the digital image forming apparatus, the image forming mode is set.
Image processing suitable for the type of input image, such as line drawing mode, halftone mode, continuous tone mode, etc., as well as automatic halftone separation mode, without increasing the complexity of selecting modes. Since it is done automatically, a good reproduction image can be obtained and
The troublesomeness of the operator to switch the mode is avoided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. FIG.
2 shows the configuration of an electric circuit system of the 1-drum type digital color copying machine shown in FIG.

First, the digital color copying machine shown in FIG. 2 will be described. In FIG. 2, 100 is a laser printer and 2 is a laser printer.
00 is an automatic document feeder, 300 is an operation board, 400
Is an image scanner.

The image scanner 400 mechanically drives the image reading portion arranged below the contact glass 401 in the left-right direction in the drawing, and sub-scans it. The light emitted from the illumination lamp 402 is reflected on the surface of the original placed on the contact glass 401 according to the density of the original image. The reflected light, that is, the detected light image passes through a large number of mirrors and lenses, and the dichroic prism 410.
Incident on. The dichroic prism 410 splits the incident light into three colors of R, G and B according to the wavelength. The three separated lights are one-dimensional CCD images that are different from each other.
Incident on the di-sensor. Each of the three one-dimensional image sensors provided in the image scanner 400 generates an analog image signal representing the brightness of each color component of R, G, B of one line in the main scanning direction on the original image. These analog image signals are digital data, that is, R image data and G image data, respectively.
The image data and the B image data are converted and supplied to the image data processing device (70 to 77 in FIG. 1). By the sub-scanning of the image reading unit, the R, G, B image data is changed to the one in which the position (line) is sequentially updated in the sub-scanning direction of the document. That is, a two-dimensional image is read.

The ADF 200 is an image scanner 200.
It is located above. It is possible to hold a large number of originals placed on the original table 210. When performing the paper feeding operation, the calling roller 212 comes into contact with the upper surface of the uppermost document,
The original that rotates and comes into contact is fed out. Reference numeral 312 is a separation roller for avoiding double feed. The original fed out to a predetermined position is further conveyed on the contact glass 401 of the image scanner by the drive of the pull-out roller 217 and the conveying belt 216, and when it reaches a predetermined reading position, that is, the front end of the original makes contact. Stop when the left edge of the glass is reached. Here, conversion of the analog image signal of the one-dimensional image sensor into R, G, B image data and sub-scanning, that is, reading of the original image is started. When the reading is completed, the conveyance belt 216 is driven again, so that the original on the contact glass is discharged and the next original is sent to the reading position. Calling roller 212
An optical sensor 211 for detecting whether or not there is a document on the document table is provided in front of. Also, the separation roller 2
An optical sensor 214 for detecting the leading edge and the size of the document is provided between 13 and the pullout roller 217. The optical sensor 214 is composed of a plurality of sensors arranged at different positions in the main scanning direction (direction perpendicular to the paper surface of FIG. 1), and the combination of the detection states of these sensors allows the document size in the main scanning direction to be determined. That is, the document width is detected. Further, a drive motor (not shown) is provided with a pulse generator according to the rotation amount, and the control device of the ADF controls the number of pulses generated by the pulse generator while the document passes through the optical sensor 214. Is measured, and the document size in the sub-scanning direction, that is, the document length is recognized from the measured value.

The calling roller 212 and the separation roller 21
3 is driven by the paper feed motor, and the pull-out roller 217 and the conveyor belt 216 are driven by the conveyor motor. The optical sensor 215 arranged downstream of the pullout roller 217 is a registration sensor.

Next, the laser printer 100 will be described. Reproduction of an image is performed on the photosensitive drum 1. Around the photosensitive drum 1, a charging charger 5, a writing unit 3,
The developing unit 4, the transfer drum 2, the cleaning unit 6 and the like are provided.

The surface of the photosensitive drum 1 is first charged with a charging char.
It is uniformly charged to a high potential by the corona current generated by the jar 5. The writing unit 3 is provided with a laser diode, and when the laser light emitted by the laser unit is applied to the surface charged with the high potential, the charging potential changes according to the intensity of the light. A potential distribution is formed on the photosensitive drum 1 according to the presence or absence of laser light irradiation. The laser light emitted by the laser diode of the writing unit 3 is reflected by the polygon mirror 3
It is irradiated onto the surface of the photosensitive drum 1 through b, the lens 3c, the mirror 3d and the lens 3e.

The polygon mirror 3b is rotationally driven at a constant speed at a high speed by the electric motor 3a. The control device of the printer 100 turns on / off the laser diode according to a binary signal (binary recording image data; recording / non-recording) in pixel units. Therefore, the potential distribution formed on the photosensitive drum 1 corresponds to the image represented by the recorded image data. That is, an electrostatic latent image is formed. This electrostatic latent image is
The developing unit 4 downstream of the writing unit 3 visualizes the toner. In this embodiment, the developing unit 4 is provided with four sets of developing devices 4M, 4C, 4Y, and 4BK, and each developing device has M
(Magenta), C (cyan), Y (yellow) and B
Toners of different colors K (black) are held.

In the case of this printer, any one of the four developing devices is selectively energized so that the electrostatic latent image is M,
It is visualized with C, Y or BK color toner.

On the other hand, the transfer paper held in the cassette 11 is fed out by the paper feed roller 12 and is transferred to the registration roller 1.
It is sent to the surface of the transfer drum 2 via 3 and moves with the rotation of the transfer drum 2 in a state of being superposed on the surface. Then, in the state of being close to the surface of the photosensitive drum 1,
The toner image formed on the photoconductor drum 1 is transferred to the surface of the transfer paper by the bias of the transfer charger 7.

In the case of the single color mode, the transfer paper on which the toner image has been transferred is separated from the transfer drum 2 and fixed by the fixing device 9.
Then, the sheet is fixed on the sheet and is discharged onto the sheet discharge tray 10. Full color
In the case of the mode, it is necessary to superimpose the four colors of BK, M, C and Y on one sheet of transfer paper. In that case, first, a toner image of BK color is formed on the photosensitive drum 1, and the toner image is transferred onto the transfer paper. Then, the transfer paper is not separated from the transfer drum 2, and then M is transferred onto the photosensitive drum 1. Forming a color toner image,
The toner image is transferred again to the transfer paper. Further, for the C color and the Y color, the toner image is formed on the photosensitive drum 1 and transferred to the transfer paper. That is, one color image is formed on the transfer paper by repeating the process of forming and transferring the toner image four times. When the transfer of all toner images is completed, the transfer paper is separated from the transfer drum 2, the toner image is fixed by the fixing device 9, and then the transfer paper is discharged to the paper discharge tray 10.

FIG. 1 shows an outline of the structure of the electric component part of the apparatus shown in FIG. The control of the entire apparatus is controlled by a system controller 50 including a micro computer or the like. The system controller 50 performs not only control of the entire apparatus, but also calculation method of image processing and switching of parameters, and settings for that purpose. Synchronous control circuit 60
Generates a clock pulse as a reference of control timing, inputs various signals for synchronizing signals between the control units, and outputs various control signals and timing signals. In this example, the main scanning synchronization signal which is the source of the scanning timing appears in synchronization with the scanning position of the polygon mirror of the laser printer 100.

The image scanner 400 is a one-dimensional image.
The image signal of each color of R, G, B read by the sensor is A /
D-converted, 8-bit color image information, that is, R,
Output as G and B image data. These image data are subjected to various kinds of processing in the image processing units (70 to 77), converted into recorded image data, and then output to the laser printer 100. Further, as will be described later, image input for image type determination (prescan) is performed prior to image input for image formation.

The image processing unit (70 to 77) has a γ
Correction 70, filter 71, color correction 72, selector 73,
Various processes such as gradation processing 74, chromatic / achromatic judgment 75, image separation 76, page image type judgment 77, etc., and a judgment unit are provided. In the γ correction 70, each of the R, G and B image data is corrected using a look-up table.

The filter 71 performs smoothing for the purpose of removing moire generated when a halftone image is input. Therefore, it is desirable not to perform the smoothing process when the possibility of moire is low. Therefore, in this embodiment,
In the line drawing mode, continuous drawing mode, and line drawing /
In continuous tone mode, it is set to through (no smoothing processing to remove moire), and in half tone mode, smoothed.
In other cases, the fine area determination result is used to switch between smoothing and smoothing.

In the color correction 72, a masking equation or the like is used to convert into information of each color of C, M, Y or C, M, Y, BK.
Since the spectral characteristics of the scanner-input data are different from others,
The conversion parameters are switched between those for continuous-tone images and those for others. However, there is no need to switch when an image whose color data is guaranteed as a standard image is input from the outside. The value of Bk is C, M, Y for each pixel.
It is calculated from the minimum value of the value of (1), but the minimum value itself is output for a line drawing, and a black amount smaller than that for a line drawing is output in order to improve gradation in halftone or continuous toning. Further, this Bk value is subtracted from C, M, and Y (under color removal: UCR; Under Color Remove) to obtain the final output of color correction. In addition, in the case of a black line drawing, an image having no color blur can be obtained by using a color determination result of image separation, which will be described later, in the case of a black line drawing.

As described above, in the present embodiment, only one image forming unit is provided, and the color image can be obtained by changing the developing device to correspond to the image forming color to obtain a color image.
The output of 2 only needs one color at a time. Therefore UCR
In order to easily achieve the above, Bk and any one of C, M and Y colors are output. In order to output these, in the system controller 50, the parameters suitable for the image forming color are set at the image forming timing. The selector 73 selects any one of C, M and Y or Bk.

In the gradation processing 74, an input image data is drawn as a line drawing.
For halftone and continuous tones, gray balance adjustment is performed by dither processing and a look-up table method in order to match the gradation characteristics of the printer. This output is sent to the laser printer 100.

In the above description, different calculation methods are used for line drawing, half-tone drawing, and continuous-tone drawing, but it is not optimal for any image type, but any image is used. A unified processing mode that can obtain a relatively good image for the seed may be provided as one selection mode. For example, in the filter 71, smooth smoothing is performed, and in the color correction 72, an intermediate parameter for halftone image and continuous tone, or a parameter assuming either one, UC
A mixed unified mode, such as setting the R amount to an intermediate value for line drawings and halftones and continuous tones, is selected within the page by selecting the operator or determining the inline image / halftone image / continuous image to be described later. You may make it select automatically, when a mixing degree is comparatively high.

The function of the chromatic / achromatic judgment 75 is shown in FIG. 8 for each R, G, B for each pixel output from the scanner 400
The bit image data is tone-balanced for each color by the γ correction 70 (FIG. 1). Achromatic judgment 7
5, the difference unit 75a first calculates the difference between the two R, G, B image data, and the comparator 75b calculates the maximum value (d [i, j] = ΔRGB) among the three sets of differences. ) Is removed. Next, in the comparator 75c, a threshold value T determined by 4 × 4 distribution units corresponding to 4 lines × 4 pixel matrix of d [i, j]
d [i, j] larger than h1 is "1" and small d
[I, j] is binarized to "0" and written in the line buffer memory 75d by the shift register method. Next, in the counting / comparing circuit 75e, the number of "1" pixels in the binary data matrix corresponding to the 4x4 pixel matrix of the shift output of the line buffer memory 75d (4x4 = 16 d [I,
j], which is larger than Th1) is counted.
When this number is larger than the threshold value Th2, this 4 × 4 pixel block is determined to be a chromatic block,
The signal = "1" is output to the AND gate 75f. When it is less than or equal to the threshold Th2, the signal is set to "0".
To the output 75f. This signal is used as a switching signal for black line image processing in the image separation mode, and is also used for chromatic / achromatic judgment for each page of the image.

The signal representing chromatic / achromatic color relating to the 4 × 4 pixel block is switched for each 4 × 4 pixel block by the AND gate 75f. The frequency counter 75g cumulatively counts the number of chromatic blocks, and the continuity counter 75g
Reference numeral h denotes two sets of counters, the first set of which is cleared by the output of the counting / comparing circuit 75e when it is achromatic, so that the number of consecutive chromatic blocks in the main scanning direction is counted. The other set counts the number of consecutive chromatic blocks in the sub-scanning direction. That is, if even one block is chromatic in the main scanning direction, this main scanning line is chromatic, and if all blocks are chromatic, the main scanning line is achromatic, and the number of consecutive chromatic main scanning lines (Scanning direction) is counted, and the count value is cleared when an achromatic main scanning line appears. A controller (not shown) for the chromatic / achromatic judgment 75 reads the count data of the frequency counter 75g and clears the frequency counter 75g every time a line sync pulse is generated, and the read count data shows the maximum frequency up to that point. It is checked if it is larger than the value, and if it is larger, the frequency maximum value is updated to it. Also, the count data of the first set of the continuity counter 75h is read every time a line synchronization pulse is generated and the first set counter is cleared, and the read count data is the maximum continuous number in the main scanning direction up to that point. It checks if it is larger than the value and if it is larger, it updates the maximum value. Further, the count data of the second set of the continuity counter 75h is also read every time the line synchronization pulse is generated, and it is checked whether the read count data is larger than the maximum value of the continuous number in the sub-scanning direction till then. If it is larger, the maximum value is updated to it. Then, when any one of these three sets of maximum values reaches a preset value, it is determined that the original is chromatic. The result of this determination is sent to the filter 71, the color correction 72, the gradation processing 74 and the system controller 50 to switch between the black and white mode and the color mode.

FIG. 4 shows the function of the image separation 76. In the image separation 76, it is determined for each minute region block whether it is a line drawing, a halftone image, or a continuous toning image. γ correction 7
The output of the G image data from 0 is received, and the two units, the edge separation 76a and the halftone dot separation 76b, determine whether or not the image is an edge and whether it is a halftone dot. The G image data is used because it is suitable for recognizing the shape of the image which has the closest brightness among the R, G and B image data. However, if R, G, B image data is converted into CIE X, Y, Z, lightness L *, chromaticity a *, b *, etc., and Y or L * is used, a higher level is obtained. A performance judgment can be obtained.

In the edge separation 76a, it is determined whether or not dark pixels (edge pixels) having a contrast are continuous, and continuous bright pixels are continuously present around the dark pixels. In this, first, the G image data is ternarized into bright, dark, and intermediate based on a predetermined threshold value.
This result is subjected to a pattern matching determination with a 3 × 3 data matrix for determining a bright portion and a dark portion for each 3 × 3 pixel matrix unit to determine whether or not the pixel of interest in the center is a bright portion edge. , A first determination is made as to whether or not it is a dark edge. Next, using a 3 × 3 density filter (coefficient matrix) for bright portion enhancement, the pixel of interest is converted into a 3 × 3 data matrix in which the bright portion is emphasized, and 3 × 3
By using a density filter (coefficient matrix) for dark part enhancement, the target pixel is converted into a 3 × 3 data matrix in which dark parts are emphasized, each of which is binarized and binarized bright part emphasis 3 × Similarly to the 3 data matrix, the 3 × 3 matrix of the binarized data obtained by ANDing the binarized dark area emphasizing 3 × 3 data matrix is expanded to the 4 × 4 matrix to obtain the original A final determination is made as to whether the center pixel (pixel of interest) of the 3 × 3 matrix is an edge. Here, the pattern matching is performed with 3 × 3, the density filter is performed with 3 × 3, and the expansion is performed with 4 × 4, but it is possible to increase or decrease it.

In the halftone dot judgment 76b, the halftone dot shape is recognized and judged. When the central pixel of the 3 × 3 pixels is extremely darker or brighter than the surrounding pixels, this central pixel is set as a target pixel, and when it is dark, it is called a valley peak and when it is bright, it is called a mountain peak. The determination of the halftone dot shape is performed by this peak, and the determination of whether it is extremely dark or bright with respect to the surroundings is performed by comparing the minimum value of the difference with the surrounding pixels with a predetermined threshold value. If the result is 4 × 4 pixels and even one pixel is a peak pixel, this block is defined as a halftone dot block, and further, 4 × 4 pixels are defined as one block and three blocks are connected by 3 × 3 blocks. When the above is a halftone dot block, the center block of interest is corrected and determined as a halftone dot block. Here again, the unit such as 3 × 3 or 4 × 4 is used for the determination, but the size may not necessarily be the size.

In the image type determination 77, first, the edge determination 7
6a and halftone dot determination 76b, the image type determination of the fine block is performed as shown in FIG. That is, a pixel that is an edge and is not a halftone dot is a line drawing portion, a pixel that is not an edge and a halftone dot is a halftone image portion, and image data that is a pixel that is not an edge and is not a halftone dot is less than a predetermined threshold value. When it is dark, it is the continuous image part, and the rest is the background part. Note that it is not necessary to use the same determination unit for the final determination of the edge determination and the halftone determination. This is because the same determination result may be output for each pixel for each determination unit.

In the image type determination 77, page image type determination is also performed. That is, the determination result of each of the line drawing portion, the half-tone image portion, and the continuous image portion is calculated as the chromatic / achromatic determination 75 (the above 75
Similar to (f to 75h), it is performed by counting continuity and frequency. That is, the above-described functions 75f to 75h of the chromatic / achromatic determination 75 are set as three sets, and the continuity and the frequency are similarly counted for each of them, and when any of them becomes equal to or more than the set value, the determination is made to the system controller 50. give. If the image separation 76 outputs these determination results for each pixel, the counter is operated for each pixel, and if they are output in block units, the counter is incremented in synchronization with this block signal.

The system controller 50 performs a full-line drawing process if only the line drawing is the result of the page drawing type judgment result (this occurs as soon as the judgment is established by the end of the image output of the entire page). If it is only a halftone image, it is a mode in which full-scale halftone processing is performed, and if it is only a continuous surface, it is a continuous image mode in which full-scale continuous image processing is performed. Similarly, if the line drawing and the halftone image are determined, the line drawing / halftone image mixed processing is performed using the result of the image separation, or the unified mode is performed. When the line drawing and continuous drawing, the halftone and continuous drawing, the line drawing, halftone and continuous drawing, and the like are determined, the mode is switched in the same manner.

That is, image separation 76 and image type determination 77
And the system controller 50, based on the input image data for one page, the image consists of only a line drawing, only a half tone image, only a continuous tone image, and a line image and a half tone image. It is determined which one of nine types of line drawings and continuous tones, half tones and continuous tones, line drawings and half tones and continuous tones, and a processing mode corresponding to this is determined by the filter 71. , Color correction 72, selector 73, and gradation processing 74. This image processing apparatus expresses a first operation method or parameter suitable for expressing a line drawing, a second operation method or parameter suitable for expressing a halftone image, and a continuous operation image. A third calculation method or parameter suitable for the above, each of which has one or more types, and uses only the first calculation or only the second calculation in the image of one page. Only, the first and second operations are switched, the first and third operations are switched, the second and third operations are switched, and the first, second and third operations are used. It is possible to use 9 kinds of calculation methods of switching and using the calculation of 3 and any one of them is selected corresponding to the mode designation of the system controller 50.

In the first embodiment, the image type is determined by the prescan method before image formation.
In the second embodiment of the present invention, the yellow (Y) image is numbered first because the change due to the conversion calculation and the switching of the parameters is not noticeable to the human eye in the yellow (Y). At this time, the above-mentioned image type determination is performed, the determination result is held in the memory, and the image processing at the time of yellow (Y) image formation is performed exclusively for line images, halftone images, and continuous tone images. A uniform process that is less likely to be impaired is defined, and the image process when forming an image of another color is switched according to the determination result stored in the memory.

It should be noted that line drawing, half-tone drawing and continuous-tone drawing
Although the image type is determined as the type, the effect can also be expected by determining the type as two types of line drawing, halftone image, and continuous tone image.

According to the first and second embodiments of the present invention described above, it is possible to efficiently and accurately determine the image type of an input image page by page. According to the second embodiment, in the color digital image processing apparatus for reproducing BK, C, M, Y or C, M, Y, page image classification can be performed without increasing the processing time, which is excellent. An image is obtained.

[0039]

EFFECT OF THE INVENTION In the digital image forming apparatus, not only the halftone automatic separation mode but also the line drawing mode and the halftone mode can be selected without increasing the troublesomeness of selecting the image forming mode.
Since image processing suitable for the type of input image such as continuous tone mode is automatically performed, a good reproduced image can be obtained and the operator's trouble of mode switching can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing an outline of the mechanism of a digital color copying machine equipped with the image processing apparatus shown in FIG.

3 is a block diagram showing a functional configuration of a chromatic / achromatic determination 75 shown in FIG.

FIG. 4 is a block diagram showing a functional configuration of the image separation 76 shown in FIG.

5 is a chart showing the contents of input information and output information of the image type determination 77 shown in FIG.

[Explanation of symbols]

100: Laser Printer 200: Automatic Document Feeder 300: Operation Board 400: Image Scanner 1: Photoreceptor Drum 2: Transfer Drum 3: Writing Unit 4: Developing Unit 5: Charging Charger 6: Clear 7: Transfer charger 8: Separation charger 9: Fixing device 10: Paper ejection tray

Claims (4)

[Claims] 1. An input means for inputting an image signal, a means for performing an operation for embodying the input image signal, and a first arithmetic method or parameter suitable for embodying a line drawing by said arithmetic means. A second operation method or parameter suitable for embodying a halftone image and one or more third operation method or parameters suitable for embodying a continuous tone image. However, in the image of one page, only the first calculation is used, only the second calculation is used, only the third calculation is used, and the first and second calculations are switched and used. And the third calculation is switched and used, the second and third calculations are switched and used, and the first, second and third calculations are switched and used, and
A line drawing consisting of only a line drawing, only a halftone image, only a continuous toning image, based on the means for selecting which of these methods is to be used and the image data input for one page. And halftone, line drawing and continuous tone,
A page image type determining means for determining which of nine types of halftones and continuous tones, a line drawing and halftones and continuous tones, and means for determining the selection of the selecting means based on the determination result. An image forming apparatus comprising: 2. The page image type judging means comprises means for discriminating whether the input image is a line drawing, a halftone image or a continuous image for each fine region, and the continuity and frequency of the judgment result. The image forming apparatus according to claim 1, wherein the type of page image is determined by counting the number of pages. 3. The page image type determining means uses the brightness or the brightness to perform the determination.
Image forming apparatus. 4. An input image is sequentially calculated with output components of four colors of black (Bk), cyan (C), magenta (M) and yellow (Y) or three colors of only C, M and Y. The calculation of this color component is performed from Y,
The page image type determination is performed in parallel with the Y component calculation, and the calculation method or parameter for line image / halftone image / continuous tone mixture is used for the Y component calculation. The image forming apparatus according to claim 2 or claim 3.