JP2008103917A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce as much as possible the influence of an area that is easily misjudged due to a constitutional factor of a reading apparatus in an image processing and apparatus for determining whether a manuscript is a color manuscript or a monochrome manuscript, and to prevent the judgment accuracy on the entire reading manuscript from being lowered. To provide an apparatus.
An image processing apparatus for determining whether a color document or a monochrome document from image data having a predetermined number of pixels in a first direction and a second direction orthogonal to the first direction, the pixel of interest The result of the achromatic color judging means for judging whether the color is a chromatic color or the achromatic color and the judgment signal changing means for changing the judgment signal value for each designated region are determined as the first direction judgment / second direction judgment. According to the result of the setting means that can be set independently and the first and second chromatic pixel coefficient means for counting the chromatic pixels in the document independently in the first direction and the second direction, respectively, according to the setting means. It has a determination means for determining whether the image data should be processed as a color document or a monochrome document.
[Selection] Figure 9

Description

  The present invention relates to an image processing apparatus and a control method thereof, and more particularly to an image processing apparatus and a control method having a function of identifying whether an input image is a color image or a monochrome image. The present invention also relates to an image forming apparatus using these image processing apparatuses.

  In a color image forming apparatus, in particular, a color copying machine realized by combining a color copying machine, a color scanner, a computer, and a color printer, C (cyan), There are cases where copying is performed with four colors of M (magenta), Y (yellow), and K (black). However, in the case of a color copying machine or a color copying apparatus using a color laser beam printer, it is desirable to copy a monochrome original with a single black color considering the life of the drum and the amount of toner consumption. This is the same as color copiers and copiers using color ink jet printers, considering the ink consumption.

  For this reason, a color image forming apparatus is conventionally equipped with a function for identifying whether a document image is a color document or a monochrome document, and the determination is made using automatic document type determination: ACS (Auto Color Select). . Conventionally, such document type discrimination is mainly performed by adding color pixels (pixels determined to be chromatic) of an input document, and statistically evaluating the added value or comparing it with a threshold value. It was done by simple evaluation.

  However, when the color pixel is determined based on the color components (R, G, and B luminance signals) of each pixel of the document image read by the document input device, the reading element that should read the color component at the same position. However, when the completely same pixel position cannot be read, that is, when reading is performed with a slight shift (hereinafter referred to as color shift), the edge of the black line is detected as having a color. End up.

  Even if the reading position accuracy is sufficient, the color component (false color) similar to the case where the reading position accuracy is insufficient is generated near the edge of the black line due to variations in MTF characteristics for each wavelength by the lens. Resulting in.

  In response to the above problem, according to Japanese Patent Application Laid-Open No. 2002-199239, when counting chromatic colors in the main and sub-scanning directions, the number of color pixels determined to be chromatic is counted, and A method of reducing the influence of false colors generated depending on the device characteristics of the reading apparatus by counting the number is proposed. Furthermore, in the above invention, the amount of color misregistration amount is larger than other regions (for example, the reading front end, the rear end, and the left and right regions) according to the color misregistration amount (false color generation degree) depending on the document reading position. By not using it for the determination, it is devised not to reduce the determination accuracy.

  In addition, in the patent document: Japanese Patent Laid-Open No. 2003-259133, as a problem when performing the above determination using ADF (Auto Document Feeder), it occurs because vibration is applied to the original when the original is drawn or released. A method for improving the influence of the false color at the edge has been proposed.

  In the above document, first, the validity determination target region in the fixed reading mode (also called book mode) and the conveyance reading mode (reading using ADF) is changed. In particular, in the conveyance reading mode, the color classification of the original is performed except for the area affected by vibration during conveyance. In the above-mentioned document, a region where false color is generated due to speed fluctuation after entry of a document is specified (predicted), a chromatic color component in a region where false color is likely to be generated is invalid, or a threshold for counting chromatic colors inside a block, A proposal has been made to avoid erroneous determination by changing the threshold for counting the color / monochrome signal determined for each block.

Also, in Patent Document: Japanese Patent No. 3303992, unlike Patent Document: Japanese Patent Laid-Open No. 2003-259133, a method is proposed in which an area part actually used in an input document is used as an ACS determination.
JP 2002-199239 JP 2003-259133 A Japanese Patent Registration No.3330392

  Patent literature: JP 2002-199239, JP 2003-259133 PR, and Patent 3303992 both have the occurrence of false colors or information from unnecessary areas by limiting the chromatic color determination area. An erroneous determination of the original color type determination is avoided.

  However, if there is information indicating that the document is chromatic or achromatic in the area where the area restriction is provided, the information cannot be used effectively in the above invention.

  In other words, despite the fact that the area restriction is provided, colorful information is described, but as a result of copying, the area other than the restriction is black and white, so it is output as a black and white document. There is a case.

  Patent document: JP 2003-259133 A public information, each of which counts the threshold for judging whether the pixel of interest is color or black and white, the threshold for counting and judging in the block, and the result judged in block unit It is proposed to improve with a threshold. However, lowering the chromatic / achromatic threshold of a pixel lowers the accuracy of subsequent determinations. In addition, in the method of counting and determining the determination result in pixel units, if there are vivid lines and character information straddling blocks, the ratio of chromatic colors to be tightened inside the block greatly affects the determination in the block. Therefore, it is considered difficult to make a sensitive determination.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to determine whether a manuscript is a color manuscript or a monochrome (monochrome) manuscript. An object of the present invention is to provide an image processing apparatus and a control method therefor that reduce the influence of an area that is easily erroneously determined and reduce the accuracy of determination on the entire read original.

  That is, the gist of the present invention is an image for determining whether the image data is a color document or a monochrome document from image data having a predetermined number of pixels in each of the first direction and the second direction orthogonal to the first direction. A processing device for determining whether a pixel of interest is a chromatic color or an achromatic color, and a determination signal change for changing a determination signal value for each designated region of a signal transmitted from the achromatic color determination unit And a setting means capable of setting the result of the determination signal changing means independently of the determination of the first direction / the determination of the second direction, and the first direction, the first direction according to the setting means The first and second chromatic pixel coefficient means for counting the chromatic pixels in the document independently in the direction 2 and the result of the first and second chromatic pixel coefficient means as a color original. Whether to process or monochrome By determining means, to solve the above problems. Further, the chromatic pixel coefficient means is characterized by calculating the continuity of pixels determined to be chromatic colors and the number of the continuity, and the determination means includes the first direction and the second direction. It is a feature that the determination result is determined by providing a threshold value independently.

  Another aspect of the present invention is to determine whether the image data is a color document or a monochrome document from image data having a predetermined number of pixels in each of the first direction and the second direction orthogonal to the first direction. An achromatic color determining unit that determines whether a pixel of interest is a chromatic color or an achromatic color, and a determination that a signal transmitted from the achromatic color determining unit is changed for each specified region The first setting means that can set the signal changing means and the result of the determination signal changing means independently of the determination of the first direction / the determination of the second direction, and the first setting means, the first direction And a second setting means for selecting a setting means in an area where the second direction and the second direction overlap with each other independently in the first direction and the second direction according to the first and second setting means. First and second chromatic pixel coefficient means for counting chromatic pixels in the document; To solve the above problem and determining means for determining whether to process a monochrome should be processed image data as a color original by the results of the chromatic pixel coefficient means. Further, the chromatic pixel coefficient means is characterized by calculating the continuity of pixels determined to be chromatic colors and the number of the continuity, and the determination means includes the first direction and the second direction. It is a feature that the determination result is determined by providing a threshold value independently.

  As described above, according to the present invention, it is possible to determine the document type without degrading the chromatic / achromatic determination accuracy determined for each pixel for the occurrence of false colors caused by the input device for each region. Therefore, for example, it is possible to accurately determine a document in which a chromatic color exists only in a region where false colors are likely to occur.

  Furthermore, each area is equipped with a mechanism that sends a determination signal independently in the main scanning direction and the sub-scanning direction, so that not only false colors caused by mechanical factors but also lens aberrations, etc. Therefore, it is possible to provide a processing device having a wide latitude compared to the prior art.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 18 is a cross-sectional view showing a structural example of a color image forming apparatus as an example of an image forming apparatus to which the image processing apparatus according to the embodiment of the present invention can be applied.

  In the figure, reference numeral 201 denotes an image scanner unit which reads a document placed on a platen glass and performs digital processing on the document image. A printer unit 200 forms an image corresponding to the original image read by the image scanner unit 201 on a recording medium such as paper and outputs the image.

  In FIG. 18, a copying machine 202 uses an original platen. However, the present invention is effective when an ADF configured with a U-turn path as shown in FIGS. In the configuration diagram showing an example of the ADF shown in FIG. 20, 1 is a document tray, and 2 is a width regulation body that regulates the side of the document. Reference numeral 3 denotes a pickup roller, which can be lowered to a position where the original comes into contact for feeding the original. A separation roller 4 is always in contact with the opposing separation pad 5 to perform frictional separation, and conveys documents one by one. Reference numeral 6 denotes a first conveyance roller, and 7 is a conveyance roller.

  The separated original is formed by an inner guide 10 and an outer guide 18, travels down a curved and inclined conveyance path, and passes through a pre-reading roller 11 and a reading pressure roller 12 as upstream conveying means immediately before the reading position Q. Then, it is conveyed to the reading position Q. A guide member that guides the back side of the document near the reading position Q (the side opposite to the reading surface) is referred to as a reading guide 13. A guide mylar 14 as a transparent sheet, which is a transparent film member, is mounted as a means for guiding the front side of the document, which is located on the opposite side of the reading guide 13. The guide mylar 14 is a transparent plastic film made of, for example, a PET material and has a thickness of about 100 μm. The guide mylar 14 is locked by the boss portion, and the member is called a mylar holder 19. One end of the guide mylar 14 is locked by the boss portion 19 a of the mylar holder 19, and the other end is placed on the discharge guide 20 through the document table glass 62.

  The reading guide 13 has a surface facing the reading position Q, a flat surface portion 13a parallel to the platen glass 62, and an upstream inclined portion 13b that is curved and inclined to the flat surface portion 13a and to the upstream and downstream sides. It is formed by the downstream inclined portion 13c. Further, the reading guide 13 is rotatably mounted about 20 rotation centers 13d, and is urged toward the original platen glass 62 by an urging means (not shown). Further, the guide mylar 14 is in contact with the platen glass 62 in the vicinity of the reading position Q, and the original image is read through the guide mylar 14 and the platen glass 62.

  The above is the apparatus configuration for reading a document when ADF is used.

  The description of the copying machine will be continued based on the configuration diagram 18.

  In the image scanner unit 201, 202 is an original platen, and 203 is an original table glass (platen glass). The document 204 is placed on the document table glass 203 with the recording surface facing downward in the figure, and the position of the document 204 is fixed by the document pressure plate 202. A light source 205 such as a fluorescent lamp, a halogen lamp, or a xenon lamp irradiates the recording surface of the original placed on the original table glass 203. In the present embodiment, it is assumed that the light source 205 is a fluorescent lamp.

  Reflected light from the original 204 is guided to mirrors 206 and 207, converged by a lens 208, and formed on a light receiving surface of an image reading element (hereinafter, CCD) 210 such as a linear CCD image sensor. The CCD 210 separates and reads the reflected light from the original into red (R), green (G), and blue (B) colors, and sends them to the image processing unit 209.

  In the present embodiment, the CCD 210 includes approximately 7500 light receiving pixels arranged in one line, and is composed of a total of 3 lines for each of RGB, and can read 297 mm in the short direction of an A3 size document at 600 dpi (dots / inch). Is possible. Similarly, in order to read 297 mm in the short direction of an A3 size document at 400 dpi, a one-dimensional image sensor with about 5000 pixels for each of RGB may be used.

  The fluorescent lamp 205 and the mirror 206 are mechanically moved in the sub-scanning direction (a direction orthogonal to the CCD 210) at a speed v and the mirror 207 is v / 2, so that the reflected light passes through the CCD 210 through a certain distance. The image is formed and can be read.

  A reference white plate 211 having uniform chromaticity is used to calculate a reference chromaticity value for correcting shading unevenness by the lens 208 and sensitivity unevenness of each pixel of the CCD 201.

  The details of the image processing unit 209 as the image processing apparatus according to the embodiment of the present invention will be described later, but the signal read by the CCD 210 is converted into a digital signal, and yellow (Y) corresponding to the ink color at the time of printing. , Magenta (M), cyan (C), and black (Bk) color component images are formed and sent to the printer unit 200. For one original scan (corresponding to one sub-scan) in the image scanner unit 201, one color component image of Y, M, C, and Bk is sent to the printer unit 200, and therefore four scans are performed. The recording color component image signals obtained in each scan are sequentially sent to the printer unit 200, whereby one printing process is completed. If there is a necessary and sufficient memory in the image processing unit 209, the result of one scan reading (the result of four scans) is stored in the memory, so that it can be sent to the printer unit once. .

  The Y, M, C, and Bk image signals sent from the image processing unit 209 in this way are sent to the laser driver 212 in the printer unit 200. The laser driver 212 outputs laser light by causing a laser diode to emit light according to the image signal of each pixel. The laser beam scans on the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216.

  Reference numerals 219 to 222 denote developing units, which develop electrostatic latent images corresponding to the respective color components using yellow, magenta, cyan, and black developing materials (toners and the like). Four developing devices 219 to 222 sequentially come into contact with the photosensitive drum 217 and develop the photosensitive drum electrostatic latent image formed by the laser light irradiation with the corresponding color toner.

  A transfer drum 223 winds the recording paper fed from the paper cassette 224 or 225 by the action of static electricity, and transfers the toner image developed on the photosensitive drum 217 onto the recording paper. In the recording process using four color components, toner of each color component is superimposed and recorded by rotating the transfer drum 223 four times. Finally, the recording paper is peeled off from the transfer drum 223 with a peeling claw, conveyed toward the fixing unit 226, fixed, and discharged outside the apparatus. The above is the outline of the operation of the color copying machine shown in FIG.

  In addition, in order to perform multiple recording on the back side of the recording paper, a branch conveyance path is provided at the paper discharge port as shown in the figure. By taking in the apparatus again through this conveyance path, it is possible to perform recording on the back surface, multiple recording, and the like.

  (Configuration of Image Processing Unit) FIG. 1A is a block diagram mainly showing a functional configuration of the image processing unit 209 in FIG. A G1 signal that is one of the three-color separation signals R1, G1, and B1 of the image read by the image scanner unit 201 is input to the character / image determination unit 111. The character / image determination unit 111 determines from the G1 signal whether the target pixel is a line image such as a character or a line image, or a gradation image such as a photograph or a print image, and the result is the character / image determination signal TI. Output as.

  The character / image determination unit 111 takes out a G component signal of, for example, about 3 × 3 pixels (which may be changed as appropriate depending on the reading resolution), calculates the difference between the maximum value and the minimum value, The determination is made based on whether the difference is equal to or greater than a predetermined value. This utilizes the phenomenon that this difference (luminance change) becomes a large value near the edge of a character or line drawing, and conversely, in the case of a halftone image, the difference is small. Further, in order to distinguish from the print image, the above 3 × 3 pixel region can be expanded and discriminated from the correspondence between the image characteristics and the spatial frequency characteristics.

  The character / image determination signal TI is output to the black character / color character / image determination signal generation unit 117 and the spatial filter coefficient storage unit 112. The spatial filter coefficient storage unit 112 is configured by, for example, a ROM or the like. When the pixel of interest indicates a character or a line drawing (for example, TI = '1'), the spatial filter coefficient for the character has a gradation (intermediate). (Tone image) (for example, TI = '0'), the tone image spatial filter coefficients are respectively selected and output.

  FIG. 2A and FIG. 2B are diagrams showing an example of the spatial filter coefficients Kij for characters and gradation images stored in the spatial filter coefficient storage unit 112. The DC component of the conventional spatial filter for characters and gradation images is “1”, whereas the spatial filter for characters or gradation images in this embodiment is shown in FIG. In b), the DC component is set to “0”. That is, for a flat image having no edge component, the output after the conventional spatial filtering outputs the input image value as it is, whereas the output value after the spatial filter processing of this embodiment is “0”.

  Returning to FIG. 1A, the three signals of the three color separation signals R1, G1, and B1 of the color image are input to the first color space conversion unit 102, and the lightness signal L1 representing the brightness and the color are obtained. It is converted into a chromaticity signal (Ca1, Cb1). The lightness signal L1 and the chromaticity signals (Ca1, Cb1) are colorimetrically determined from three variables L *, a *, b * and CIE1976 (L * u * v *) in the CIE 1976 (L * a * b *) color space. The color space may be three variables L *, u *, v *, or may be a variable in an arbitrary color space determined more simply. However, in the present embodiment, L1, Ca1, and Cb1 are used because simple conversion from the three-color separation signals R, G, and B is possible.

  The following equation (1) shows an example of a conversion equation for simply converting the three color separation signals R, G, and B into lightness and chromaticity signals L1, Ca1, and Cb1.

L = (R + 2G + B) / 4
Ca = (RG) / 2 Formula (1)
Cb = (R + G-2B) / 4
The lightness signal L1 and the chromaticity signals (Ca1, Cb1) converted by the first color space conversion unit 102 are input to the delay unit 103. In the delay unit 103, the lightness signal L1 is stored for N lines, and the chromaticity signals (Ca1, Cb1) are stored for (N / 2) lines. More specifically, when performing the 5 × 5 pixel spatial filter processing, the edge enhancement extraction unit 113 becomes data for a total of five lines of the lightness signal L1 for the past four lines and the lightness signal L1 for the current line. Is input. At this time, the chromaticity signal becomes data for a total of three lines of the past 4/2 = 2 lines and the current line, and is input to the saturation amount extraction unit 114.

  The edge enhancement amount extraction unit 113 calculates the brightness signal in the 5 × 5 pixel block based on the spatial filter coefficient Kij (which depends on the character / image determination signal TI) output from the spatial filter coefficient storage unit 112, and The edge enhancement amount ε of the pixel (the pixel at the center position in the 5 × 5 pixel block) is calculated and output.

When a 5 × 5 lightness signal is represented by L1ij (i = 1 to 5, j = 1 to 5), the edge enhancement amount ε is obtained as follows. ε = (ΣL1ij * Kij) / C (where * is a multiplication, and C is a normalization constant that normalizes the edge-enhanced component.)
This edge enhancement amount ε is supplied to the edge enhancement amount distribution unit 116. The edge enhancement amount distribution unit 116 is based on the edge enhancement amount ε, the saturation signal S from the saturation amount extraction unit 114, and a determination signal KC from the achromatic / chromatic color determination unit 115 described later. Edge enhancement amount εl and edge enhancement correction amount εc of the chromaticity signals (Ca1, Cb1) are generated and output to the edge enhancement unit 104.

  Although not shown in FIG. 1, the chromaticity signals (Ca1, Cb1) delayed by the delay unit 103 are actually data for a total of three lines of the delayed two lines and the current line, This is input to the saturation amount extraction unit 114. In response to this, the saturation amount extraction unit 114 generates and outputs a saturation signal S representing the vividness of the color as described above.

  Here, a method for generating the saturation signal S from the chromaticity signals (Ca1, Cb1) will be briefly described. The chromaticity signal (Ca1, Cb1) is a signal (a *, b *) in the CIE 1976 (L *, a *, b *) color space or a signal in the CIE 1976 (L *, u *, v *) color space. When (u *, v *), the saturation signal S is determined by equation (2). In the equation, the symbol “^” represents a power.

S = (Ca1 ^ 2 + Cb1 ^ 2) ^ 0.5 Formula (2)
Further, for simplicity, the saturation signal S may be determined by the equation (3).

S = MAX (Ca1, Cb1) Formula (3)
Here, the function MAX (A, B) outputs a value having a larger absolute value of the variables A and B.

  In addition to the edge enhancement amount ε and the saturation signal S, the edge enhancement amount distribution unit 116 also receives a determination signal KC from an achromatic / chromatic color determination unit 115 described later.

  The achromatic / chromatic color determination unit 115 determines whether the pixel is black and white (achromatic color) or color (chromatic color), and outputs a determination signal KC. In this embodiment, the input signal to the achromatic / chromatic color determination unit 115 is a saturation signal S representing the vividness of the color, and the achromatic / chromatic color is determined based on this signal.

  However, as described above, the saturation signal S is generated by the saturation amount extraction unit 114 based on the chromaticity signals (Ca1, Cb1) for a total of three lines of 2 lines + current line delayed by the delay unit 103. Therefore, as the input signal to the achromatic / chromatic color determination unit 115, the saturation signal S and the chromaticity signals (Ca1, Cb1) which are the original signals may be input. (In this case, the (Ca1, Cb1) signal line drawn to the saturation amount extraction unit 114 shown in FIG. 1 is extended to the achromatic / chromatic determination unit 115 together with the saturation signal S).

  Hereinafter, the delay unit 103 according to the present embodiment and the edge enhancement amount extraction unit 113, the saturation amount extraction unit 114, and the achromatic / chromatic color determination unit 115, which are the peripheral units, will be described in detail with reference to FIG.

  Since the lightness signal L1 and the chromaticity signals (Ca1, Cb1) output from the first color space conversion unit 102 are synchronized with the central pixel of the lightness signal by the line memories 801 to 804 of the delay unit 103, the line memory In 805 and 806, the chromaticity signal Ca1 is stored for two lines, and in the line memories 807 and 808, the chromaticity signal Cb1 is stored for two lines.

  Now, assuming that the center line is j line, the lightness signal L1 stores j-2, j-1, j, j + 1 lines, and the lightness signal for five lines including the current line j + 2 lines is the edge enhancement amount extraction unit. 113 is input.

  The edge enhancement unit 113 creates edge-enhanced data (edge enhancement amount ε) based on the 5 × 5 brightness signal from the delay unit 103 and the 5 × 5 filter coefficient from the spatial filter coefficient storage unit 112. Therefore, from the above formula, it can be simply considered that it can be composed of 25 multipliers and 24 adders.

  On the other hand, for the chromaticity signals Ca1 and Cb1, the line memories 805 to 808 of the delay unit 103 store j and j + 1 lines, respectively, and the chromaticity signals Ca1 and Cb1 for three lines including the current line j + 2 are stored. Is supplied to the saturation amount extraction unit 114 and the achromatic / chromatic color determination unit 115.

  Further, in the present embodiment, the saturation signal S is calculated for the three lines j, j + 1, and j + 2 by using the above-described equations (2) and (3) when calculating the achromatic / chromatic color determination signal KC. It is also possible to perform spatial processing using this data. For example, the saturation signal S can be obtained by averaging the saturation signals of adjacent pixels (8 pixels) of 3 × 3 size surrounding the target pixel, and the average value can be represented by the saturation signal S. Similarly, for the chromatic color determination signal KC, the determination result of the adjacent pixels of 3 × 3 size may be statistically processed, and the representative value may be the achromatic / chromatic color determination signal KC.

  (Calculation of Color Determination Signal KC) Next, a method for calculating the determination signal KC from the obtained saturation signal S will be described. When the saturation signal S is small, the pixel is black and white (achromatic color). When the saturation signal S is large, the pixel is color (chromatic color). Therefore, simply, the determination signal KC is determined by Expression (4) using a predetermined threshold ρ.

(When S <ρ) KC = achromatic color (when S ≧ ρ) KC = chromatic color Formula (4)
(Generation of Edge Enhancement Correction Amount for Lightness Signal) Hereinafter, processing for generating edge enhancement correction amounts εl and εc based on the edge enhancement amount ε, the saturation signal S, and the determination signal KC input to the edge enhancement amount distribution unit 116. Will be described.

  First, the distribution of the edge enhancement correction amount ε with respect to the lightness signal L1 is increased, and the total edge enhancement amount ε is assigned to εl for achromatic signal pixels. Further, edge correction for the brightness signal is not performed for pixels having a saturation equal to or higher than a predetermined value.

  This process will be described with reference to the flowchart of FIG. 3 and the schematic diagram of FIG. In step S1 shown in FIG. 3, the process branches according to the achromatic / chromatic determination signal KC of the target pixel. When the determination signal KC is achromatic (when the determination in step S1 is YES), in order to assign the total edge enhancement amount ε to εl, “1” is assigned to the multiplication coefficient γ in step S2, and εl = γε, That is, ε is assigned to εl.

  If the determination signal KC is a chromatic color in step S1, it is determined whether the saturation signal S is larger than a predetermined value η (step S3). 0 ”is assigned (step S4), and γε, ie,“ 0 ”is assigned to εl in step S6.

  On the other hand, when the saturation S is equal to or less than η in step S3, it is difficult to determine whether the target pixel is a chromatic color or an achromatic color. Therefore, in step S5 and step S6, the multiplication coefficient γ and further εl are set. Determined by equation (5).

γ = (1− (S−α) / (η−α))
εl = (1 ((S−α) / (η−α)) ε (5)
When the above processing is performed, the relationship among α, η, and γ is as shown in FIG. That is, γ is “1” when it can be determined that the color is substantially achromatic, and γ is “0” when it can be determined that the color is chromatic. In the intermediate state, a value of 0 to 1 (that is, a decimal point) is taken according to the saturation signal S as shown.

  (Generation of Edge Enhancement Correction Amount for Chromaticity Signal) Next, the edge enhancement correction amount εc for the chromaticity signal (Ca1, Cb1) will be described.

  For chromaticity signals, contrary to that of lightness signals, the higher the saturation (brighter colors), the more the edge enhancement amount ε is distributed to the chromaticity signals, and for achromatic signal pixels. Then, edge correction is not performed, and the chromaticity signal of the target pixel is also removed.

  This is because in an image forming apparatus such as a color copying machine, if a color component remains in a copy image such as a black character, the image quality is visually deteriorated. In other words, for such a pixel, it is necessary to cut the color component and correct the color to a complete achromatic signal.

  This process will be described with reference to the flowchart of FIG. 5 and the schematic diagram of FIG. In step S11 of FIG. 5, first, the process for the target pixel is switched in accordance with the achromatic / chromatic color determination signal KC. That is, when the determination signal KC indicates an achromatic color (when step S11 in the figure is YES), in order to set the edge enhancement amount εc to 0 as described above, the multiplication coefficient γ is set to 0 in step S12. Εc is set to 0 by performing the calculation of S18.

  If the determination in step S11 is NO, the process proceeds to step S13, and the saturation signal S is compared with the threshold value λ2. If S> λ2, the multiplication coefficient γ is set to 1 in step S14, the calculation in step S18 is performed, and εc is set to a value of (1−ε / κ).

  If it is determined in step S13 that S ≦ λ2, the process proceeds to step S15, where the saturation S and λ1 are compared to determine whether S <λ1. If the inequality is satisfied, it may be determined that the pixel of interest is an achromatic color, so the multiplication coefficient γ is set to 0 and εc is set to 0 in step S19.

  When it is determined in step S15 that S ≧ λ1, the multiplication coefficient γ is determined from the following equation in step S17 in order to set the multiplication coefficient γ to a value corresponding to the saturation signal S (a value between 0 and 1). To do.

γ = (S−λ1) / (λ2−λ1) Equation (6)
In step S18, the edge enhancement correction amount εc for the chromaticity signal is obtained according to the equation (7).

εc = γ (1-ε / κ) Equation (7)
(Where κ is a normalization constant)
As a result, the multiplication coefficient γ takes a value corresponding to the chromaticity signal S as shown in FIG. That is, the multiplication coefficient γ takes a value of “0” during an achromatic color (less than the threshold λ1), and εc = 0. Further, γ = (S−λ1) / (λ2−λ1) when the saturation S is between the threshold values λ1 and λ2, and increases continuously as the saturation S increases. When the saturation S is higher than the threshold λ2, γ = 1, so εc = 1−ε / κ.

  The edge enhancement correction amounts εl and εc generated as described above are supplied to the edge enhancement unit 104 together with the L, Ca, and Cb signals.

The edge enhancement unit 104 adds the edge enhancement correction amount εl to the brightness signal L from the delay unit 103, and multiplies the edge enhancement correction amount εc to the same chromaticity signals Ca and Cb. , L2, Ca2, and Cb2. That is,
L2 = εl + L1
Ca2 = εc * Ca1
Cb2 = εc * Cb1 Formula (8)
It becomes.

  As can be seen from the equation (8), by adding the edge correction amount εl to the signal L, the pixel having high chroma and not desired to be edge-enhanced becomes (εl = 0), and the lightness is preserved. . On the other hand, by multiplying the signals Ca and Cb by the edge correction amount εc, as the saturation is lower and the color is closer to an achromatic color, the εc gradually becomes a smaller value. , Εc = 0. That is, the lower the saturation value, the easier the removal of the chromaticity component of the target pixel itself is controlled.

  Here, the preservability of the hue (hue) with respect to the edge enhancement of the chromaticity signal will be described. FIG. 7 represents chromaticity coordinates with the chromaticity signal (Ca1, Cb1) direction as a coordinate axis. For simplicity of explanation, the Ca and Cb axes are assumed to be a * and b * axes in the CIE 1976 (L *, a *, b *) color space.

  Further, the intersection point 0 of the a * and b * axes represents an achromatic color, the saturation is higher as the distance from the intersection point 0 increases, and the angle θ formed with the a * axis represents the hue (hue). Further, the lightness L * is a direction perpendicular to the paper surface. Now, when the target pixels are chromaticity signals Ca1 (702) and Cb1 (703), this color is represented by a vector 701 on the chromaticity coordinates. According to equation (8), the chromaticity signal (Ca1, cb1) is multiplied by the edge correction amount εc, and the generated edge-enhanced signal (Ca2, Cb2) becomes (εcCa1, εcCb1). Although it is represented by a vector 704 on the degree coordinate, the angle θ formed with the a * axis does not change as shown in the figure, indicating that there is no change in color. In other words, it can be seen that the vividness is enhanced by the emphasis, but the change in color is not substantially affected.

  When the edge enhancement processing is performed as described above, the signals L2, Ca2, and Cb2 are supplied to the second color space conversion unit 105, where they are inversely converted to R, G, and B values.

  The following equation (9) shows an example of a conversion equation for converting the lightness and chromaticity signals L2, Ca2, and Cb2 into the three-color separation signals R2, G2, and B2, and is obtained from the equation (1) described above. It is.

R2 = (4L + 5Ca + 2Cb) / 4
G2 = (4L-3Ca + 2Cb) / 4
B2 = (4L + Ca-6Cb) / 4 Formula (9)
Thereafter, the three-color separation signal inversely converted into R2, G2, and B2 signals is input to the luminance / density conversion unit 106 and converted into density signals C1, M1, and Y1. Since the conversion from RGB to CMY color system itself is known, the method will not be described here.

  The density signals C1, M1, and Y1 are then subjected to background removal (known as UCR processing) by the color correction unit 107 to generate a black component signal K, undercolor removal, and color correction. Processing is performed, and density signals C2, M2, Y2, and K2 are output.

  In the present embodiment, the color correction unit 107 performs this process according to the TC signal from the black character / color character / image determination signal generation unit 117. The black character / color character / image determination signal generation unit 117 inputs the color determination signal KC that is the determination result of the achromatic / chromatic color determination unit 115 and the TI signal that is the determination result of the character / image determination unit 111. The TC signal is generated.

  For example, color correction is performed with emphasis on highlight color reproducibility for image signals, and color correction is performed on color characters and black character signals without highlight reproduction with the background color skipped. Similarly, the binarization unit 108 transmits C3, M3, Y3, and K3 signals obtained by binarizing the multi-valued image using a known error diffusion process, and subsequently the character is also input to the smoothing / resolution conversion unit 109. / Referring to the determination signal TI that is the determination result of the image determination unit 111, when TI = 1 (character portion), an edge represented by notch processing is converted to a high resolution in the main scanning direction or the sub-scanning direction. Correction processing is performed.

  Note that the smoothing / resolution conversion unit 109 can also control the function itself in accordance with an instruction from an operation unit (not shown) or an image processing mode (for example, for photographs or characters). . Each process is performed, and the C4, M4, Y4, and K4 signals that are the output of the smoothing / resolution conversion unit 109 are output to the printer unit 200, whereby a color image is printed and recorded.

  (Document Type Determination Unit) The image processing described above operates by determining the determination result of the document type determination unit 118 described below. 9 to 17 are explanatory diagrams of the document type determination unit 118.

  The document type determination unit 118 recognizes in the main scanning direction and the sub-scanning direction the pixel signal from which the determination signal KC is output as a chromatic color from the achromatic / chromatic color determination unit 115 described above, and makes a final determination.

  FIG. 9 is a block diagram illustrating a configuration example of the document type determination unit 118 in the present embodiment. In the present embodiment, the document type determination unit 118 sequentially calculates the color determination signal KC output from the achromatic / chromatic color determination unit 115 to determine whether the document is monochrome or color.

  First, the identification region restriction unit 901 restricts whether or not the achromatic / chromatic color determination signal KC sequentially sent from the achromatic / chromatic color determination unit 115 is an effective region for performing the document type determination unit. As shown in FIGS. 19A and 19B, the identification area restriction unit 901 describes an area that restricts subsequent determination processing in the main scanning and sub-scanning directions with respect to the entire document reading area 1801.

  FIG. 19A gives a restriction in the main scanning direction. In the figure, the main scanning direction is limited by the portions (areas) shown in the three areas covered by the halftone dots. Although this embodiment has been described with three areas, the number of areas to be restricted is not limited to this number.

  The area (halftone dot portion) that gives this restriction can be set by register settings (1901 to 1905), for example. The register setting value may be set in advance in the ROM 122 or may be set by inputting from the operation unit via the input / output unit 124.

  In this embodiment, the main scanning direction area used for the document type determination is determined by Reg-width: 1905.

  Therefore, the region from the leftmost broken line as the starting point to Reg_main_mask: 1901 (= main scanning mask 0 region), Reg_main0_enable: 1902 to Reg_main1_mask: 1903 region (= main scanning mask 1 region), and Reg_main1_enable: 1904 to Reg_w: In each of the areas 1905 (= the main scanning mask 2 area), the restriction is made.

  Similarly, in FIG. 19B, with the upper broken line as the base point, the region from Reg_sub0_mask: 1906 (= sub-scanning mask 0 region), Reg_sub0_enable: 1907 to Reg_sub1_mask: 1908 (= sub-scanning mask 1 region), Reg_sub1_enable: Restriction is performed in each area from 1909 to Reg_sub2_mask: 1910 (= sub-scanning mask 2 area), and further from Reg_sub2_enable: 1911 to Reg_height: 1912 (= sub-scanning mask 3 area).

  Similarly to FIG. 19-a, the area restriction in the sub-scanning direction (halftone dot part) is not limited to four. Furthermore, for setting the number of areas and the range thereof, FIG. As described in 19-a, it can be set by register setting (1906 to 1912). The register setting value may be set in advance via the ROM 122 or may be set by inputting from the operation unit via the input / output unit 124.

  In addition, the sub-scanning validity determination area is limited by Reg_height: 1912.

  Next, the limiting method in the mask area described above will be described.

  FIG. 22 is an example of the restriction contents set in the main scanning and sub-scanning directions, respectively. In the figure, the content restricted by 2 bits is defined, but the number of bits may be increased according to the content of the restriction.

  First, “00” is “not detecting continuity in the main scanning / sub-scanning direction” described later, and “01” is “detecting continuity only in the main scanning direction and masking the sub-scanning direction: forced "10 is not reflected in determination", "10" is opposite to "01", "continuity is detected only in the sub-scanning direction and the main scanning direction is masked: not forcibly reflected in determination", and finally "11 “Is operated as“ same as effective area ”.

As described above, a method for independently limiting the mask regions for main scanning and sub-scanning is set.
Next, how the independently limited setting method behaves in the overlapping region will be described with reference to FIGS.

  FIG. 24 shows a state in which the main scanning / sub-scanning mask restrictions overlap as described above. In order to simplify the explanation in the figure, it is assumed that the mask area 2401 in the main scanning direction and the mask area 2402 in the sub-scanning are set one by one, and the overlapping area (displayed by oblique lines): 2403 is 1 (If a plurality of mask areas are set, there are a plurality of areas 2403).

  In the identification area restriction unit 901, a restriction value composed of 2 bits for each of main scanning / sub-scanning shown in FIG. 23 is determined to determine the behavior of the target pixel in the subsequent processing. This restriction determination block: FIG. 23 uses, as inputs, a mask setting value for main scanning: 2302 and a mask setting value for sub-scanning: 2303, and its behavior is determined by a restriction determination unit: 2301, and the mask setting value is determined. : 2304 is output, and the limiting method is determined.

  As described above, the region limit coefficient storage unit 119 stores, for example, a main scanning synchronization signal: HSYNC that can recognize a main scanning line, a sub-scanning synchronization signal: VSYNC, and a video clock: VCLK that is a signal synchronized with each pixel. From the above, the limitation method can be used by switching the limitation method for each pixel by using a counter value of an internal counter (not shown).

  In the present embodiment, the hatched portion can be switched by a register value: 2305 for determining which of the main scanning and sub-scanning settings is to be prioritized.

  The register value: 2305 may be set in advance via the ROM 122 or may be set by inputting from the operation unit via the input / output unit 124.

  As the setting configuration, the following six can be selected or set as initial values.

• Main scan priority • Sub scan priority • “00”
・ "01"
·"Ten"
・ "11"
Due to the above restriction, the document area restriction means 901 sends the KC signal as it is, or gives a restriction to the subsequent determination to change and send the KC signal.

  In the present embodiment, the region-limited signal is further subjected to final determination based on the determination result in the main scanning direction (main scanning count unit) and the determination result in the sub scanning direction (sub scanning count unit). Have.

  24, the white region shown in FIG. 24 corresponds to “11” in FIG. 23, and the main scan determination is output as ACS_MAIN, and the sub-scan determination is output as ACS_SUB.

  In the halftone dot area, the setting values that are restricted for each of the main scanning and the sub scanning are reflected in ACS_MAIN and ACS_SUB, and if set to “01”, ACS_SUB is forced to be achromatic in the specified area. The determined signal is generated, and a KC signal is created as it is in ACS_MAIN.

  In the shaded area, the values of ACS_MAIN and ACS_SUB are determined according to the setting of the register value 2305 in FIG.

  By performing the above-mentioned restrictions, when a false color occurs due to a color shift or the like, not only the pixel signal determined to be a chromatic color is forced to be an achromatic color but also the determination in the sub-scanning direction. By propagating the color information, it becomes possible to determine the chromatic / achromatic color of the document without degrading the determination accuracy.

  Similarly, when false colors are likely to occur in the main scanning direction due to other factors, by specifying “01”, the sub-scanning direction determination is masked (ACS_SUB is forcibly achromatic), and the main scanning direction It can be used for judgment.

(Determination processing in the main scanning direction)
First, a process connected to the main scanning count unit 903, which is a unit that determines that a chromatic color exists in the main scanning direction, will be described.

  The achromatic / chromatic signal KC subjected to the region restriction by the document region discriminating unit 901 is output as an ACS_MAIN signal, and the first main scanning color group recognition unit 902 collects chromatic color pixels continuous in the main scanning direction. It is determined whether there is a predetermined number or more. A configuration example is shown in FIG.

  In FIG. 10, the first main scanning color group recognition unit 902 includes a main scanning continuity recognition unit 1001 that determines whether a predetermined number M (≧ 0) of pixels determined to be chromatic in the main scanning direction are continuous. The main scanning continuity recognition unit 1001 includes a color group recognition unit 1002 that recognizes a cluster of chromatic color pixels that are M pixels continuous as a color cluster. The result determined by the first main scanning color group recognition unit 902 is sent as a COL_EXIST_M (1 bit) signal to the main scanning counting unit 903 at the subsequent stage.

  First, the main scanning continuity recognition unit 1001 will be described. First, the reason for observing the continuity of chromatic color pixels in such main scanning is, for example, as shown in FIG. 11, for some reason (lens) at the edge of the black vertical line 1101 (1102, 1103: gray portion in the figure). When a color shift occurs in the main scanning direction due to the MTF difference, aberration, mirror stage vibration, etc., false colors are generated at the edges 1102 and 1103 in spite of the original achromatic region, and the chromatic color pixels There are as many vertical lines 1101 as there are in the sub-scanning direction.

  If the erroneously determined parts resulting from this are counted incorrectly, the document type detection (color document or monochrome document) will be erroneously determined, so a continuity recognition process in the main scanning direction like this process is incorporated. , Avoiding misjudgment.

  Next, processing of the main scanning continuity recognition unit 1001 will be described. First, the counter 1011 for observing continuity at the start of processing is reset. In the present embodiment, an up counter is assumed to observe the continuity of chromatic colors. Therefore, in order to recognize the continuity, the operation timing indicating the start of the copy sequence operation or the start of the scanner operation is determined by the timing of the sub-scanning synchronization signal (VSYNC) and the main scanning synchronization signal (HSYNC). At the same time, the internal up counter is reset.

  In addition, since the internal counter observes a continuous chromatic color determination signal, if the chromatic color is not continuous, it is reset each time, and further, for the purpose of observing the presence of the chromatic color in the main scanning direction, It is also reset at the end of one main scanning line, and the internal counter is reset under a total of three conditions. The reset signal generation unit 1010 generates a reset signal for the counter 1011 from the VSYNC, HSYNC, and ACS_MAIN signals according to the above-described conditions, and supplies the reset signal to the reset terminal of the counter 1011.

  The value of the internal counter increases every video clock (VCLK), and when the counter value reaches a predetermined count value (M, M> 0) without being reset, the count value and the predetermined value M are A comparator 1012 to compare generates a detection signal. The predetermined value M is stored in the ROM 122 described later.

  The operation of the main scanning continuity recognition unit 1001 will be further described with reference to FIG. Here, the description will be made by paying attention to the processing of a determination signal of 9 pixels on one main scanning line, for example. The square in the figure shows the result of the achromatic / chromatic color determination signal KC in one pixel (strictly, it indicates the ACS_MAIN signal subjected to the area restriction), the white square is the pixel determined to be chromatic, and the black square is empty. Represents a pixel determined to be colored. In the figure, N-4 indicates the result of the old time, and N + 4 indicates the determination result of the new time.

  The internal counter 1011 of the main scanning continuity recognition unit 1001 shown in the present embodiment continuously counts up four pixels from N-4 to N, and observes an ACS_MAIN signal determined to be achromatic at N + 1 pixels. As a result, the reset signal generator 1010 generates a reset signal and resets the internal counter 1011. Then, counting starts again from N + 2 pixels of chromatic color pixels, and when counting up to N + 3 pixels, since the N + 4 pixels are determined to be achromatic colors, the internal counter is reset again.

  During the counting operation, when the count value reaches the predetermined value M, a pulse signal for counting up the counter 1021 in the color group recognition processing unit 1002 is output from the comparator 1012. This pulse signal is also used as a reset signal for the counter 1011 of the main-scanning continuity recognition unit 1001, whereby the presence / absence of a chromatic pixel having M consecutive pixels is determined again.

  In addition, since the internal counter 1011 used in the present embodiment is configured with a finite number of bits, when the counter value OUT indicates the maximum value, there is a limit so that the counter is not further counted up. .

  Next, the color group recognition processing unit 1002 in the main scanning color group recognition process will be described. Similarly to the main scanning continuity recognition unit 1001, the color group recognition processing 1002 includes an up counter 1021, a comparator 1022 that compares the count value of the counter 1021 with a predetermined threshold MG, and a reset signal generation unit 1020. ing.

  When the main scanning continuity recognition unit 1001 detects a chromatic color pixel having a predetermined continuity M, a counter 1021 in the color group recognition processing 1002 is counted up by a pulse signal output from the comparator 1012. Then, after the comparator 1022 compares the count value of the counter 1021 with a predetermined value MG (a value set in the ROM 122 described later), if it is equal to or larger than the predetermined value, a chromatic color cluster is observed on the main scanning line of interest. Notify that it is present: Set bit “1” in COL_EXIST_M signal. Otherwise, COL_EXIST_M sets that the bit is set to “0” on the assumption that there is no chromatic color cluster, and informs the main scanning count unit in the subsequent stage of the presence of the color in the line of interest.

  Similar to the reset signal generation unit 1010 of the main scanning continuity recognition unit 1001, the reset signal generation unit 1020 determines the end of one main scanning line, the start of the copy sequence operation, and the start of the scanner operation from the VSYNC and HSYNC signals. A reset signal for the counter 1021 is generated in accordance with the operation timing shown.

  Next, a specific operation of the color group recognition unit 1002 will be described with reference to FIG. 13 indicate pixels for which white is determined to be a chromatic color, and pixels for which black is determined to be an achromatic color, as described with reference to FIG. Here, in order to make the operation content easy to understand, the operation will be described together with the operation of the main scanning continuity recognition unit 1001. Further, the operation will be described on the assumption that the continuity M detected by the main scanning continuity recognition unit 1001 is “2” and the parameter MG for recognizing the color cluster by the color group recognition unit 1002 is “3”.

  In the example of FIG. 13, the internal counter 1011 for recognizing main scanning continuity has a counter value of 2 due to the chromatic pixels N-4 and N-3, so that the comparator 1012 generates a pulse signal and the color group recognition unit. A counter 1021 inside 1002 counts up and becomes 1. Since the pulse signal of the comparator 1012 is used as a reset signal of the counter 1011, it is reset after the counter 1021 counts up.

  Subsequently, since the counter value of the counter 1011 reaches “2” again at N−1, the counter 1021 counts up and the counter value becomes 2. Since N + 1 pixels are achromatic, the counter 1011 is reset at that time, and the counter value of the counter 1021 is incremented to 3 at the next N + 3 pixels. At this time, since the count value becomes the same value as MG, the comparator 1022 sets “1” to the COL_EXIST_M signal to notify the main scanning count unit 903 in the subsequent stage that the color of interest is present. Further, once the value of COL_EXIST_M becomes “1”, the value of the counter 1021 is not decreased in the processing for the same main scanning line, and therefore “1” is held for the main scanning line.

  In FIG. 13, the counter values of the counter 1011 and the counter 1021 when processing up to N + 8 pixels are “2” and “5”, respectively, and the count 1011 is reset. Similarly to the counter 1011, the counter 1021 is composed of a finite number of bits. Therefore, when the counter value shows the maximum value, the counter 1021 is limited so that it is not counted up any further.

  Further, as described above, the counter 1021 is reset at the time of the copy sequence operation, the scan operation, and further every main scanning line, similarly to the counter 1011. The operation content of the first main scanning color group recognition unit 902 has been described above. In this way, the first main scanning color group recognition unit 902 first determines the continuity of a predetermined number of chromatic color pixels and whether or not a predetermined number of continuous clusters exist on the main scanning line of interest. To do.

  Next, the main scanning count unit 903 will be described. As shown in FIG. 14, the main scanning count unit 903 is also configured by an up counter 911 and a reset signal generation unit 910 in the same basic configuration as the main scanning continuity recognition unit 1001 and the color group recognition unit 1002. .

  The counter 911 is reset at the initial stage of the copy sequence and at the initial stage of the scan, and is not reset for each main scanning line like the counters 1011 and 1021 of the first main scanning color group recognition unit 902. The reset signal generation unit 910 generates a reset signal for resetting the counter 911 at these predetermined timings from the VSYNC and HSYNC signals.

  The count timing of the counter 911 is the processing within one main scanning line, when the processing of the first main scanning color group recognition unit 902 is completed and the value of COL_EXIST_M is determined. That is, on one main scanning line, a cluster of chromatic color pixels having the set continuity M is detected MG times, and counted after the presence of color in the line of interest is determined.

  At this time, the counter 1021 in the first main scanning color group recognition unit 902 is not reset until the main scanning count unit 903 finishes counting. Similarly to the counter group in the main scanning color group recognition unit 902, the counter 911 in the main scanning count unit 903 is restricted from being counted any more when the count value reaches the maximum value. The above is the description regarding the determination process in the main scanning direction.

(Sub-scanning direction determination process)
Subsequently, determination processing in the sub-scanning direction will be described with reference to FIGS. Similar to the main scanning direction, the sub-scanning direction determination process includes a second main scanning color group recognition unit 904 (for sub-scanning) and a sub-scanning counting unit 905. A feature of the determination process in the sub-scanning direction is that when the presence of a cluster of color pixels is recognized in the line of interest, the presence of a color in the sub-scanning direction is recognized by observing the continuity in the sub-scanning direction. .

  First, the second main scanning color group recognition unit 904 will be described with reference to FIG. The second main scanning color group recognition unit 904 has the same configuration as the first main scanning color group recognition unit 902 used for the determination unit in the main scanning direction (the continuity M compared by the comparator 1012 is S, 1401 in FIG. 15 is the same as 1001 in FIG. 10 and 1042 in FIG. 15 except that the continuity MG compared by the comparator 1022 changes to SG and the output COL_EXIST_M of the color group recognition means changes to COL_EXIST_S. Has a circuit configuration similar to that of 1002 in FIG.

  Although it is also a feature of this embodiment, the reason for using the same processing for the main scanning and sub-scanning determination processing is that the parameters used for processing in the main scanning and sub-scanning processing determination This is to provide different determination accuracy by enabling the setting independently. Therefore, in this embodiment, the parameters S and SG for recognizing the continuity for sub-scanning determination can have different values from M and MG for main-scanning determination.

  For example, when the color misregistration is severe in the sub-scanning direction, the continuity M and the sensitivity of the mass recognition parameter MG are changed from those in the sub-scanning direction with the setting parameters of the first main scanning color group recognition unit 902 in the main scanning direction. However, there is a case where the determination sensitivity of the region itself (accuracy for determining the presence or absence of a chromatic color) itself is lowered.

  In the present invention, the input KC signal is not forcibly changed in the main scanning / sub-scanning direction independently of the input signal of the pixel that is likely to generate a false color depending on the area specified by the document area determination unit 901. As a signal to be determined, the ACS_MAIN signal and the ACS_SUB signal are improved by sending a signal limited in accordance with the register setting.

  Subsequently, processing of the sub-scanning counting unit 905 will be described with reference to FIGS. FIG. 16 shows an internal processing block of the sub-scanning counting unit 905. First, the sub-scanning continuity recognition unit 1501 inside the sub-scanning counting unit 905 will be described. Similar to the main scanning continuity recognition unit 1001, the sub-scan continuity recognition unit 1501 includes an internal counter 1511, a comparator 1512, and a reset signal generation unit 1510.

  First, the value of COL_EXIST_S sent from the second main scanning continuity recognition unit 904 at the previous stage is counted after the determination result in one main scanning line is confirmed. At this time, similarly to the case where the main scanning continuity recognition unit 1001 recognizes the continuity, the comparator 1512 recognizes the continuity in the sub-scanning direction (compare with the threshold line). As a result of the comparison, if the value of the counter 1511 exceeds the threshold value, the counter 1521 of the subsequent sub-scanning direction counting unit 1502 counts up.

  A reset signal generation unit 1510 included in the sub-scanning continuity recognition unit 1501 generates a reset signal that resets the counter 1511 at the initial stage of the copy sequence operation and the initial scan operation. The counter 1511 is also reset by a signal that the comparator 1512 counts up the counter 1521 of the sub-scanning direction counting unit 1502.

  Similarly, a reset signal generation unit 1520 included in the sub-scanning direction counting unit 1502 generates a reset signal that resets the counter 1521 at the initial stage of the copy sequence operation and the initial scanning operation.

  Next, processing of the sub-scanning counting unit 905 will be described using FIG. In FIG. 17, N-4 to N + 8 represent pixel positions in the main scanning direction, M-4 to M + 3 represent the number of lines in the sub-scanning direction, white cells represent pixels determined to be chromatic colors, and black cells Represents a pixel determined to be an achromatic color. In order to easily explain the operation, thresholds for determining continuity are set as S = 3, SG = 2, and line = 3.

  When one main scanning line starts with N-4 pixels and one main scanning line ends with N + 8 pixels, the second main scanning color group recognition unit 904 performs N-2 pixels, N-2 pixels, and N-1 pixels. Since the chromatic color pixels are 3 consecutive from N + 1 to N + 1, COLOR_EXIST_S becomes 1 at this time, and when the line is finished, the internal counter 1511 of the sub-scan continuity recognition unit 1501 for the M-4 line is incremented to 1. Become.

  Subsequently, since the M-3 and M-2 lines have the same pattern as the M-4 line, the count value of the counter 1511 is 3. At this time, the comparator 1512 detects that the threshold line (= 3) has been reached, and the internal counter 1521 of the sub-scanning direction counting unit 1502 counts up. When the counter 1521 counts up, the counter 1511 is reset by the output signal of the comparator 1512.

  Subsequently, since three continuous chromatic color pixels are detected twice also in the M-1 line, COLOR_EXIST_S becomes 1, and when the line ends, the internal counter 1511 of the sub-scan continuity recognition unit 1501 in the M-1 line. Is incremented to 1. Similarly, the processing is continued, and when the count value of the counter 1511 becomes 3 in the M + 1 line, the counter 1521 is incremented again by the comparator 1512 and the counter value becomes 2.

  In addition, the counters 1511 and 1512 in the sub-scanning counting unit 905 are limited so that when the counters show the maximum value, they are not further counted up. The above is the description regarding the sub-scanning counting unit 905 and the sub-scanning direction determination process.

  As described above, when the result of the determination unit in the main scanning and sub-scanning directions is confirmed (indicating the end of one scan, which may be either forward scan or back scan), each count result is observed by the identification unit 906. .

  The identification unit 906 determines whether the document is monochrome or color according to a predetermined determination condition from the count value MAIN_UC of the main scanning count unit 903 and the sub-scanning counting unit 905SUB_UC.

  The determination condition can be arbitrarily determined. For example, if the value of one of the main scanning and sub-scanning count values is 1 or more, it is determined that a color exists in the original and the read original is Predetermined image processing is performed by setting processing dedicated to color processing. Alternatively, when the count value of the main scanning count unit 903 is 1 or more and the count value of the sub-scanning counting unit 905 is 3 or more, it can be determined as a color original. In this way, by combining the count values of the sub-scanning counting unit, it is possible to reduce the possibility of false detection of a false color generated in the black contour.

  If the identification unit 906 determines that the document is color, image processing suitable for an image-rendered image such as using color toner is performed, and the printer unit 200 performs color image formation processing. If the original is determined to be monochrome, image processing that is optimal for monochrome processing, such as using only black toner, is performed, and the printer unit 200 performs image formation processing.

  In the present embodiment, the image processing unit 209 shown in FIG. 1A can be configured by hardware. For example, as shown in FIG. It is also possible to realize the program that is executed using the RAM 123 as a work area. In this case, exchanges with the image scanner unit 201 and the printer unit 200 are performed via the input / output unit 124. The RAM 123 is used not only as a work area for the CPU 121, but also as a primary storage location for image data read from the image scanner unit 201 and print data transmitted to the printer unit 200. Further, an external storage device such as a hard disk drive can be used as a readable / writable storage device other than the RAM 123.

  Further, it is needless to say that, among the units in FIG. 1A, only a part with a large CPU processing load is configured by hardware, and the other part can be realized by the CPU executing a program. .

  As described above, according to the present embodiment, even if the edge of a black thin line in a monochrome original is color-shifted due to the occurrence of color misregistration, the color type counting method is devised to increase the type detection of the original. Can be done with precision. Specifically, by observing the continuity of the color dots in the determination method in the main scanning and sub-scanning directions, an algorithm having a high latitude for color misregistration can be realized as compared with the conventional method using simple addition. Furthermore, since the accuracy of the continuity in the main scanning and sub-scanning directions can be set independently, it is possible to set an appropriate threshold value for each scanner model or for each scanner. Could have

  Note that the thresholds for each determination described in the embodiment may be dynamically changed as appropriate. As the timing of the change, for example, a part that detects the size of the document image is provided, and a signal from the detection part may be considered.

  In addition, by setting the threshold value according to the characteristics of the image scanner (such as the amount of reading position deviation), it is possible to make highly accurate judgments without being affected by individual differences in the image scanner, and the image scanner can be replaced. Alternatively, appropriate determination can always be made even when a plurality of image scanner units can be selected and used.

[Other Embodiments]
The present invention may be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a scanner, a printer, etc.), or may be applied to a copying machine composed of a single device as described above. .

  An object of the present invention is to supply a storage medium (or recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus. Needless to say, this can also be achieved by reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the structural example of the image process part as an image processing apparatus which concerns on embodiment of this invention. It is a figure which shows the example of the spatial filter coefficient which the spatial filter coefficient memory | storage part of FIG. 1 memorize | stores. It is a flowchart which shows the edge emphasis correction amount production | generation process with respect to the brightness signal performed in the edge emphasis amount distribution part of FIG. It is a figure which shows the edge emphasis correction amount based on the process of FIG. 3 is a flowchart illustrating edge enhancement correction amount generation processing for a chromaticity signal performed by an edge enhancement amount distribution unit in FIG. 1. It is a figure which shows the edge emphasis correction amount based on the process of FIG. In an embodiment of the present invention, it is a figure which shows that hue (hue) is preserved before and after edge emphasis execution of a chromaticity signal. It is a block diagram which shows the connection example with the structural example of the delay part in FIG. 1, and a related other part. FIG. 2 is a block diagram illustrating a configuration example of a document type determination unit in FIG. 1. FIG. 10 is a block diagram illustrating a configuration example of a first main scanning color group recognition unit in FIG. 9. It is a figure explaining a color shift. It is a figure which shows the example of an output of the ACS_MAIN signal for demonstrating operation | movement of the main scanning continuity recognition part in FIG. It is a figure which shows the example of an output of the IRO_ACS signal for demonstrating operation | movement of the color group recognition part in FIG. FIG. 10 is a block diagram illustrating a configuration example of a main scanning count unit in FIG. 9. FIG. 10 is a block diagram illustrating a configuration example of a second main scanning color group recognition unit in FIG. 9. FIG. 10 is a block diagram illustrating a configuration example of a sub-scanning counting unit in FIG. 9. It is a figure which shows the example of an output of the IRO_ACS signal for demonstrating operation | movement of the subscanning count part in FIG. 1 is a block diagram illustrating a configuration example of a color copying machine as an example of an image forming apparatus to which an image processing apparatus according to an embodiment of the present invention can be applied. FIG. 10 is a diagram illustrating an example of a document reading area restricted by the document area restriction unit in FIG. 9. An example of a structure of ADF is shown. An example of a structure of ADF is shown. It is a table which shows the example of a setting of area | region restrictions. It is a block diagram of the restriction | limiting determination part in the area | region where the restrictions overlapped. It is a figure which shows that the restriction | limiting area | region overlapped.

Claims (6)

An image processing apparatus for determining whether the image data is a color document or a monochrome document from image data having a predetermined number of pixels in each of a first direction and a second direction orthogonal to the first direction,
Achromatic color determination means for determining whether the pixel of interest is a chromatic color or an achromatic color;
A determination signal changing means for changing a signal sent from the achromatic color determining means for each designated area;
Setting means capable of setting the result of the determination signal changing means independently of the determination in the first direction and the determination in the second direction;
First and second chromatic pixel coefficient means for counting chromatic pixels in the document independently in the first direction and the second direction, respectively, in accordance with the setting means. An image processing apparatus comprising: determining means for determining whether image data should be processed as a color original or monochrome according to a result of the chromatic pixel coefficient means.   2. The image processing apparatus according to claim 1, wherein the chromatic pixel coefficient means calculates a continuity of pixels determined to be a chromatic color and a number of the continuity.   The image processing apparatus according to claim 1, wherein the determination unit performs determination by providing a threshold value independently for the count results in the first direction and the second direction. An image processing apparatus for determining whether the image data is a color document or a monochrome document from image data having a predetermined number of pixels in each of a first direction and a second direction orthogonal to the first direction,
Achromatic color determination means for determining whether the pixel of interest is a chromatic color or an achromatic color;
A determination signal changing means for changing a signal sent from the achromatic color determining means for each designated area;
A first setting means capable of setting the result of the determination signal changing means independently of the determination in the first direction and the determination in the second direction;
In the first setting means, in the region where the first direction and the second direction overlap, the second setting means for selecting the setting means,
According to the first and second setting means, first and second chromatic pixel coefficient means for counting chromatic pixels in the document independently in the first direction and the second direction, respectively. 1. An image processing apparatus comprising: determination means for determining whether image data should be processed as a color document or monochrome according to a result of the first and second chromatic pixel coefficient means.   5. The image processing apparatus according to claim 4, wherein the chromatic pixel coefficient means calculates a continuity of pixels determined to be a chromatic color and a number of the continuity.   5. The image processing apparatus according to claim 4, wherein the determination means determines the threshold value independently for the counting results in the first direction and the second direction.

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