JP2002305665A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor capable of realizing automatic original color decision (ACS) processing that can output decision results agreeing to user's preference and sense of sight. SOLUTION: This image processor has a plurality of area deciding parts E1 to E25 which set a pixel color decision area divided into a plurality of areas on a chromaticity plane with a plurality of thresholds THa1 to THa6 and THb1 to THb6, decide which area of the pixel color decision area a pixel of a decision object is included in and also can switchingly decide that a pixel included in each area is a color pixel or a black and white pixel in each of the areas divided in the pixel color decision area, and a decision results outputting part 27 including an OR circuit 28 for deciding the pixel of the decision object is a color pixel or a black and white pixel on the basis of decision results of the plurality of area deciding parts E1 to E25 as the configuration of a pixel color deciding part 24 for deciding a pixel constituting an image read by an image reading means is a color pixel or a black and white pixel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a copying machine, an image scanner and a facsimile apparatus for reading an image of a document and processing the image data. It is suitable to be applied to an image processing apparatus having an ACS (Auto Color Selection) processing function for automatically determining whether or not the image processing is performed.

[0002]

2. Description of the Related Art Generally, in an image processing apparatus such as a full-color copying machine, an image forming mode (color mode / monochrome mode) is switched according to whether a document to be processed is a color document or a monochrome document. It is also known that the determination of whether a document is a color document or a black-and-white document, that is, the determination of the so-called document color is automatically performed by the ACS processing function without the user having to specify each time.

In the ACS processing, an image of a document is actually read, and a pixel color determination is performed to determine whether the pixels constituting the read image are color pixels or black and white pixels. Or black-and-white original. Further, when determining the pixel color, in the conventional image processing apparatus, in a uniform color space of the L * a * b * color system, a square is formed on a chromaticity plane (on an a * b * plane) representing hue and saturation. It is known that a determination region is set and a pixel color (color / black and white) is determined depending on whether or not a determination target pixel (target pixel) is included in the determination region. Specifically, as shown in FIG. 18, on the chromaticity plane represented by the a * axis and the b * axis, the determination area is determined by the minimum and maximum thresholds of a * and the minimum and maximum thresholds of b *. , And this determination area is set as a fixed black and white area. The pixels included in the black and white area are determined as black and white pixels, and the other pixels (that is, pixels not included in the black and white area) are determined as color pixels.

However, since the boundary between black and white / color judgments regarding chromaticity is only subjective, it is possible that the judgment criterion may be different for each user. Therefore, conventionally, it has been necessary for the user to optimize the determination area according to his / her preference.

[0005] Regarding these points, for example, Japanese Patent Laid-Open No.
No. 0675 proposes a method in which a predetermined color filter area is provided separately from the determination area, and pixels included in the filter area are treated as black and white pixels. Japanese Patent Application Laid-Open No. 4-336876 proposes a method of changing the size of the determination area according to the brightness (L * value).

[0006]

However, according to the methods described in the above two publications, the determination area is not freely configured, so that the determination area is set finely according to the user's preference. I couldn't. As a result, the document that the user has recognized as a black and white document is A
In some cases, the CS process determines that the document is a color document, and conversely, the user recognizes a document that is recognized as a color document as a monochrome document in the ACS process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an image processing apparatus capable of realizing an ACS processing capable of outputting a judgment result in accordance with the user's preference and vision. Is to do.

[0008]

An image processing apparatus according to the present invention comprises a pixel color determining means for determining whether a pixel constituting an image read by an image reading means is a color pixel or a monochrome pixel. The pixel color determination means sets a pixel color determination area divided into a plurality of areas NI on a chromaticity plane, and determines which area of the pixel color determination area includes the pixel to be determined. Determining means, for each area divided in the pixel color determination area, area setting means capable of switching between determining whether a pixel included in the area is a color pixel or a monochrome pixel, And a second determination unit that determines whether the pixel to be determined is a color pixel or a monochrome pixel based on the determination result of the determination unit and the setting condition of the area setting unit.

In the image processing apparatus having the above configuration, the first determination means sets a pixel color determination area divided by a plurality of areas on a chromaticity plane, and determines which area includes the pixel to be determined. Is determined. At this time, if the area including the pixel to be determined has been set to be determined as a color pixel by the area setting means, this pixel is determined as a color pixel by the second determination means. If the area including the pixel to be determined is set by the area setting means to be determined as a monochrome pixel, the second determination means determines that the pixel is a monochrome pixel.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an image processing apparatus according to the present invention is applied to an image reading apparatus such as an image scanner will be described below in detail with reference to the drawings. The image processing apparatus according to the present invention is not limited to an image reading apparatus, but is applicable to an image forming apparatus such as a color copying machine and a facsimile machine.

FIG. 1 is a schematic diagram showing the configuration of an image reading apparatus to which the present invention is applied. The illustrated image reading device 1 includes:
A document holding cover 3 with an automatic document feeder (ADF) that automatically feeds a document 2 to be processed to a preset reading position is provided. The document holding cover 3 is supported on the apparatus main body 4 by a hinge mechanism or the like so as to be openable and closable, and is opened and closed by a user. On the upper surface of the apparatus main body 4, a platen glass 5 serving as a document table is provided. The document 2 to be processed is set (placed) on the platen glass 5.

On the other hand, an optical scanning system as image reading means for reading an image of a document is incorporated in the apparatus main body 4. This optical scanning system includes a full-rate carriage 6, a half-rate carriage 7, an imaging lens 8
And a photoelectric conversion element 9. A lamp 10 and a first mirror 11 are mounted on the full-rate carriage 6, and a second mirror 12 is mounted on the half-rate carriage 7.
And a third mirror 13 are mounted.

The carriages 6 and 7 move in the sub-scanning direction (left and right directions in the drawing) using a common carriage moving motor as a drive source. At this time, the half-rate carriage 7 moves with a moving amount of の of the full-rate carriage 6, so that even if the carriages 6 and 7 move to any position in the sub-scanning direction, the half-rate carriage 7 moves from the original surface to the photoelectric conversion element 9. Is always kept constant.

On the other hand, the lamp 10 irradiates light to the surface of the original 2 to be read, and the reflected light from the original surface is reflected by the first mirror 11, the second mirror 12, and the third mirror 1
3 sequentially reflected. The imaging lens 8 forms an image of the light reflected by the third mirror 13 on the imaging surface of the photoelectric conversion element 9 at a predetermined reduction magnification. The photoelectric conversion element 9 is an image sensor for reading a document image, and is constituted by, for example, a three-line color CCD sensor. The photoelectric conversion element 9 performs photoelectric conversion of reflected light from a document in pixel units and outputs R (red), G (green), and B (blue) analog image signals (hereinafter, referred to as RGB signals).

FIG. 2 is a block diagram showing a control configuration of an image reading apparatus to which the present invention is applied. 2, the RGB signals input from the photoelectric conversion element 9 are provided to the analog / shading correction unit 14. This analog /
The shading correction unit 14 performs automatic gain control (AG) on the RGB signals given from the photoelectric conversion element 9.
F), after performing processing such as automatic offset control (AOC), A / D conversion is performed. By this A / D conversion, RG
Since the B signal is converted from an analog value into digital multi-value information, the analog / shading correction unit 14 performs shading correction on the digitized RGB signal.

The corrected RGB signals (multi-valued information) are sent to the image processing unit 15. The image processing unit 15
Various processes are performed on a given RGB signal. As one of the processing modes in the image processing unit 15,
The conversion from RGB to L * a * b * is performed. Thereby, RG
The B signal is converted into multivalued information of L * representing lightness and a * and b * representing hue and saturation. L * a * generated by this transformation
The b * signal is sent to the ACS processing unit 16. The ACS processing unit 16 performs a process of determining whether a document to be processed is a color document or a monochrome document.

On the other hand, the main control unit 17 is constituted by, for example, a CPU (Central Processing Unit), and has a ROM (Read-On).
ly Memory) 18 to control the operation of the entire apparatus according to a predetermined control program. Detection signals from various sensors 19 are input to the main control unit 17 as state information in the apparatus. Among various sensors 19,
For example, a sensor that detects the open / closed state of the document holding cover 3 and a sensor that detects the position where the document is conveyed by the automatic document feeder are included. The ADF control unit 20, the illumination control unit 21, and the scan control unit 22 control the operation of the control target unit in accordance with commands from the main control unit 17, respectively. That is, the ADF control unit 20 controls the operation of the automatic document feeder mounted on the document holding cover 3 described above, and the illumination control unit 21 controls the on / off operation of the lamp 10 mounted on the full rate carriage 6 described above. , Scanning control unit 2
Reference numeral 2 controls a rotation operation of a carriage moving motor (stepping motor or the like) 23.

FIG. 3 is a block diagram showing the internal configuration of the ACS processing unit 16. As shown, the ACS processing unit 16
It comprises a pixel color determination unit 24, a block color determination unit 25, and a document color determination unit 26. Pixel color determination unit 24
Is to determine whether pixels constituting a document image read by the optical scanning system (6 to 13) are color pixels or monochrome pixels. The determination of the pixel color (color pixel / black and white pixel) in the pixel color determination unit 24 is performed for each pixel (pixel unit) constituting an image read from a document. The result of the pixel color determination by the pixel color determination unit 24 is sent to the block color determination unit 25. The details of the pixel color determination unit 24 will be described later.

The block color determining section 25 divides an image reading area corresponding to the document size into blocks of N pixels × M lines, and determines whether each block is a color block or a monochrome block. The determination result of the pixel color sent from the pixel color determination unit 24 is used for the determination process of the block color (color / monochrome) in the block color determination unit 25. That is, the block color determination unit 25 counts the number of color pixels included in the divided block as described above, and compares the count value with a preset threshold value for block color determination. It is determined whether the block is a color block or a black and white block based on the result. This block color determination unit 25
Is sent to the document color determination unit 26.

The document color determining section 26 determines whether the document from which the image has been read is a color document or a black and white document. The original color (color / color / color
The determination result of the block color sent from the block color determination unit 25 is used for the determination process of “black and white”. That is, the document color determination unit 26 counts the number of blocks determined as color blocks by the block color determination unit 25 among the blocks divided in the image reading area corresponding to the document size as described above, The count value is compared with a preset threshold value for document color determination, and it is determined whether the document is a color document or a monochrome document based on the comparison result. The result of the determination of the document color by the document color determination unit 26 is sent to the main control unit 17 and is used, for example, when an image is generated by an image forming apparatus or the like.

Here, the configuration of the pixel color determining section 24 and the processing contents thereof will be described in detail. First, the pixel color determination unit 2
In FIG. 4, as shown in FIG. 4, a plurality of (25 in the example in the figure) areas (No. 1 to No. 25) are divided on a chromaticity plane (on the a * b * plane) representing hue and saturation (FIG. 4). A subdivided pixel color determination area is set. Each of the areas (No. 1 to No. 25) divided in the pixel color determination area has a plurality (six in the example) of thresholds THa1 to THa6 corresponding to the a * axis and the b * axis. A plurality of (six in the example in the figure) threshold values THb1 to THb6 are separated in a grid pattern. These threshold values THa1 to
THa6 and THb1 to THb6 are provided to the pixel color determination section 15 as pixel color determination thresholds.

Here, on the chromaticity plane described above, a *
Of the threshold values THa1 to THa6 corresponding to the axis, the threshold value THa1
And THa6 are respectively given as a minimum threshold value and a maximum threshold value of a *, and the threshold values THa2 to TH
a5 is given. Similarly, THb1 to THb corresponding to the b * axis
Of b6, the threshold values THb1 and THb6 are given as the minimum and maximum threshold values of b *, respectively, and the threshold values THb2 to THb5 are given to separate them.

Accordingly, the minimum threshold values THa1 and THb1 and the maximum threshold values THa6 and THa6 corresponding to the a * axis and the b * axis, respectively.
THb6 defines the outer frame (range) of the above-described pixel color determination area. The pixel color determination area is set so as to surround an inner area (including an area where color / black and white recognition is ambiguous) excluding an area that is explicitly recognized as a color on the chromaticity plane. For example, if the range of possible values of a * on the a * axis is −80 to +80, THa1 = −30,
THa6 = + 30 is set. Assuming that the range of possible values of b * on the b * axis is −60 to +100, TH
b1 = −30 and THb6 = + 30. Note that the size of the pixel color determination area, the number of divisions of the area in the pixel color determination area, the size, and the like can be arbitrarily changed by changing the condition of the threshold value provided to the pixel color determination unit 24.

FIG. 5 is a block diagram showing the internal configuration of the pixel color judgment unit 24. As shown in the figure, the pixel color determination unit 24
Mainly, area determination units E1 to E25 corresponding to the respective areas (No. 1 to No. 25) divided in the pixel color determination area.
And a determination result output unit 27 that determines a pixel color (color pixel / monochrome pixel) based on the output from each of the area determination units E1 to E25 and outputs the determination result.

The area determination section E1 corresponds to the area No. 1 of the pixel color determination area, and includes a first comparison circuit CMP-1 and a second comparison circuit CMP-1.
Comparison circuit CMP-2, third comparison circuit CMP-3, fourth comparison circuit CMP-
4, first AND circuit AND-1, second AND circuit AND-2, third
It comprises an AND circuit AND-3 and a selector SEL-1.

The pixel value Da * (a * value of the pixel to be determined) is given to one input terminal of the first comparison circuit CMP-1, and the threshold value THa1 is given to the other input terminal. . A pixel value Da * is input to one input terminal of the second comparison circuit CMP-2.
And a threshold value THa2 is applied to the other input terminal. On the other hand, a pixel value Db * (b * value of the pixel to be determined) is given to one input terminal of the third comparison circuit CMP-3,
A threshold value THb1 is given to the other input terminal. A pixel value Db * is provided to one input terminal of the fourth comparison circuit CMP-4, and a threshold value THb2 is provided to the other input terminal.

On the other hand, the output of the first comparison circuit CMP-1 is provided to one input terminal of the first AND circuit AND-1, and the output of the second comparison circuit CMP-2 is provided to the other input terminal. Given. The output of the third comparison circuit CMP-3 is provided to one input terminal of the second AND circuit AND-2, and the output of the fourth comparison circuit CMP-3 is applied to the other input terminal.
The output of the comparison circuit CMP-4 is provided. Further, the output of the first AND circuit AND-1 is provided to one input terminal of the third AND circuit AND-3, and the second AND circuit AN is provided to the other input terminal thereof.
The output of D-2 is provided. The output of the third AND circuit AND-3 is one input a of the selector SEL. Selector SEL-1
Is connected to the ground. The selector SEL-1 is supplied with a selection signal φSEL1. The selection signal φSEL1 determines which of the two inputs a and b of the selector SEL-1 is to be selected as the output of the selector SEL-1. The selection signal φSEL1 can be switched from outside by an operator, a user, or the like.

The area judgment section E2 corresponds to the area No. 2 of the pixel color judgment area, and includes a first comparison circuit CMP-1 and a second comparison circuit CMP-1.
Comparison circuit CMP-2, third comparison circuit CMP-3, fourth comparison circuit CMP-
4, first AND circuit AND-1, second AND circuit AND-2, third
It comprises an AND circuit AND-3 and a selector SEL-2. This area determination section E2 is provided with another area determination section (to E
Basically, it has the same configuration and function as the area determination unit E1, including 25). However, the pixel values (Da *, Db
*) Is compared with each area determination unit E1
A threshold value for dividing areas No. 1 to No. 25 corresponding to E25 is given.

Here, each of the area determination units E1 to E25
The operation function will be described by taking the area determination unit E1 as an example. In the area determination unit E1, the first comparison circuit CM
The pixel value Da * is compared with the threshold value THa1 at P-1, and the pixel value Da * is compared with the threshold value THa2 at the second comparison circuit CMP-2.
The third comparator CMP-3 compares the pixel value Db * with the threshold value THb1, and the fourth comparator CMP-4 compares the pixel value Db * with the threshold value THb1.
Hb2 is compared. Then, the pixel value Da * is set to the threshold value THa1.
If the output is within the range THa2, the outputs of the first comparator CMP-1 and the second comparator CMP-2 are both "1". Similarly,
If the pixel value Db * is in the range between the threshold values THb1 and THb2, the outputs of the third comparison circuit CMP-3 and the fourth comparison circuit CMP-4 are both "1".

When the outputs of the first comparator CMP-1 and the second comparator CMP-2 are both "1", the first AND circuit A
The output of ND-1 becomes "1", and the third comparator CMP-
When the outputs of the third and fourth comparison circuits CMP-4 are both "1",
The output of the second AND circuit AND-2 becomes "1". further,
When the outputs of the first AND circuit AND-1 and the second AND circuit AND-2 are both "1", the output of the third AND circuit AND-3 is "1".

Therefore, when the pixel value Da * is equal to the threshold value
If the pixel value Db * is within the range of the threshold values THb1 to THb2, that is, if the pixel to be determined is included in the area No. 1 in the pixel color determination area on the chromaticity plane, the third logic The output of the AND circuit AND-3 becomes "1", otherwise, that is, if the pixel to be determined is not included in the area No. 1, the output of the third AND circuit AND-3 becomes "0". .

From this, the first comparison circuit CMP-1 and the second comparison circuit CMP-1
Comparison circuit CMP-2, third comparison circuit CMP-3, fourth comparison circuit CMP-
4, first AND circuit AND-1, second AND circuit AND-2, third
The circuit configuration including the AND circuit AND-3 has a determination function of determining whether or not the determination target pixel is included in the area No. 1.

On the other hand, when the input a is selected by the selection signal φSEL1 in the selector SEL-1, the output ("1" or "0") of the third AND circuit AND-3 is output to the selector SEL-1.
When the input signal b is output from −1 and the input signal b is selected by the selection signal φSEL1, “0” is forcibly output regardless of whether or not the pixel to be determined is included in the area No. 1.

Therefore, when the output of the third AND circuit AND-3 is "1", that is, when the pixel to be determined is included in the area No. 1, the input signal a is selected by the selection signal φSEL1. When the output of the selector SEL-1 becomes "1" and the input b is selected by the selection signal φSEL1, the selector SEL-1
Is "0". At this time, assuming that the output of the selector SEL-1 is “1” as a monochrome pixel and the output of the selector SEL-1 is “0” as a color pixel as the determination result of the area determination unit E1, the input signal a is selected by the selection signal φSEL1. When selected, the pixels included in area No. 1 are determined as black and white pixels, and when input b is selected by selection signal φSEL1, the pixels included in area No. 1 are determined as color pixels. Will be.

Even if the input a is selected by the selection signal φSEL1, if the pixel to be determined is not included in the area No. 1, the output of the selector SEL-1 becomes "0". Further, when the pixel to be determined is not included in any of the areas No. 1 to No. 25 of the pixel color determination area, the output of the selectors SEL-1 to SEL-25 in each of the area determination units E1 to E25. Are all "0". That is, in the present embodiment, a region outside the pixel color determination region (a region that is explicitly recognized as a color) on the chromaticity plane is set as a fixed color region, and a pixel to be determined is included in this color region. (In other words, when the pixel to be determined is not included in the pixel color determination area), the pixel is determined to be a color pixel and “0” is output.

From the above, in the area determination section E1, by switching the selection signal φSEL1 to be given to the selector SEL-1, the pixels included in the area No. 1 are determined as color pixels or monochrome pixels. Can be arbitrarily switched.

The determination circuits (the first comparison circuit CMP-1, the second comparison circuit CMP-2, the third comparison circuit CMP-3, and the fourth comparison circuit CMP-) provided in each of the area determination units E1 to E25. 4. The circuit configuration of the first AND circuit AND-1, the second AND circuit AND-2, and the third AND circuit AND-3) is such that the determination target pixel is any one of the area No. 1 in the pixel color determination area. No. 25 to No. 25.

Further, each of the area determination units E1 to E25
, SEL-25 provided in each of the areas No. 1 to No. 25 divided in the pixel color determination area.
For each time, an area setting means that can switch between determining whether a pixel included in the area is a color pixel or a monochrome pixel is configured.

On the other hand, the judgment result output section 27 is composed of an OR circuit 28, an inverter 29 and a selector 30. The OR circuit 28 includes each area determination unit E
Outputs from 1 to E25 are provided as inputs. The output of the OR circuit 28 is one input a of the selector 30. The inverter 29 inverts the output of the OR circuit 28, and this inverted output becomes the other input b of the selector 30.

In the judgment result output unit 27 having the above configuration,
The OR circuit 28 outputs “0” when the outputs from the area determination units E1 to E25 are all “0”, and “1” when any one of the outputs is “1”. Is output. The output of the OR circuit 28 is provided to one input a of the selector 30. In contrast, the selector 30
An inverted output obtained by inverting the output of the OR circuit 28 by the inverter 29 is provided to the other input b of the circuit. The selector 30 is supplied with a selection signal φSELA. The selection signal φSELA determines which of the two inputs a and b of the selector 30 is to be selected as the output of the selector 30. The selection signal φSELA can be switched by an operator, a user, or the like from outside.

Here, when the output of the OR circuit 28 is "0", one input a of the selector 30 is "0" and the other input b is "1". Therefore, the selection signal φSELA
When the input a is selected, the output of the selector 30 becomes “0”, and when the input b is selected, the selector 30
Is "1". When the output of the OR circuit 28 is “1”, one input a of the selector 30 is “1”.
, The other input b becomes “0”. Therefore, if the input a is selected by the selection signal φSELA, the output of the selector 30 becomes “1”, and if the input b is selected, the output of the selector 30 becomes “0”. When the output of the selector 30 is “0”, the result of the determination is that the pixel to be determined is a color pixel, and the output of the selector 30 is “1”.
In the case of, the determination result is that the pixel to be determined is a monochrome pixel.

As described above, the OR circuit 28 outputs "0" or "1" based on the output from each of the area judgment sections E1 to E25, so that the judgment result of the first judgment means and the area This constitutes a second determining means for determining whether the pixel to be determined is a color pixel or a monochrome pixel based on the setting conditions of the setting means. Further, since the inverter 29 inverts the output of the OR circuit 28, it constitutes an inversion judging means for inverting the judgment result of the second judging means. Further, the selector 30 can select the output of the OR circuit 28 or the output of the inverter 29, and
Since the output of 0 is output as the final determination result in the pixel color determination unit 24, it constitutes a determination result selection unit in the present invention.

In the image processing apparatus provided with the pixel color judging section 24 having the above configuration, the pixels included in an arbitrary area among the respective areas No. 1 to No. 25 divided in the pixel color judging area. Can be determined as a color pixel or a monochrome pixel. For example, the selector of the area determination unit E2
When the selection signal φSEL2 for selecting the input a is given to the SEL-2, the pixels included in the area No. 2 can be determined as the monochrome pixels, and the selection signal φS for selecting the input b can be determined.
When EL2 is given, pixels included in area No. 2 can be determined as color pixels. Further, a selection signal φSEL2 for selecting the input a is given to the selector SEL-2 of the area determination unit E2, and all selectors other than the area determination unit E2 are selected for the input b. By providing the signal, only the pixels included in the area No. 2 can be determined as black and white pixels. As a result, it is possible to arbitrarily set the pixel color determination area according to the user's preference and vision, as well as the user's intention.

Further, by providing an inverter (judgment output selection means) 29 in the judgment result output section 27, it is possible to judge only pixels included in an arbitrary area as color pixels. For example, the selector of the area determination unit E2
A selection signal φSEL2 for selecting the input a is supplied to the SEL-2, and all the input signals b are input to the selectors of the other area determination units (E1, E3 to E25) except the area determination unit E2.
And a judgment result output unit 27
Selection signal φS which causes the selector 30 to select the input b.
By providing ELA, only pixels included in area No. 2 can be determined to be color pixels. As a result, variations when setting the pixel color determination area can be increased.

Hereinafter, a specific case will be described. First, a procedure in the case where the user sets the pixel color determination area according to his / her preference will be described with reference to the flowchart in FIG. When the user sets the pixel color determination area, the user selects the ACS user selection mode via the operation panel of the image reading apparatus (step S1). The ACS user selection mode is a mode prepared in advance for the user to set the pixel color determination area as one of the original image reading modes.

If the user has not selected the ACS user selection mode, an area in the pixel color determination area is set according to a standard area setting condition prepared in advance (step S2). In this standard area setting condition, the center (a * axis and b *
The selection signal of the selector in each area determination unit is switched so that the pixels included in the area near the zero point where the axes intersect) are determined as monochrome pixels, and the pixels included in the area near the periphery are determined as color pixels. Can be

On the other hand, when the user selects the ACS user selection mode, the user specifies a color (step S3). The color designation by the user is performed by, for example, selecting a color desired to be black and white from a user interface (edit pad or the like) provided on the document pressing cover 3 (FIG. 1). The color that can be specified on the user interface is associated in advance with which area in the pixel color determination area set by the pixel color determination unit 24. Therefore, when a color is specified by the user, a condition for determining a pixel included in an area corresponding to the color specified by the user as a monochrome pixel is added to the standard area setting condition.
An area within the pixel color determination area is set (step S
4). For example, assuming that the area corresponding to the color designated by the user is area No. 1 in FIG. 4, the selector SEL-1 of the area determination unit E1 corresponding to this area No. This is executed by switching the selection signal φSEL1 so as to make a selection.

Thereafter, after the original image is read by the optical scanning system, ACS processing is performed (steps S5 and S6). In the ACS processing, pixel color determination is performed using the pixel color determination area set in the previous step S2 or S4. Therefore, in the determination using the pixel color determination area set in step S4, the pixels included in the area corresponding to the color designated by the user are determined as monochrome pixels.

Next, a description will be given of a process for not determining a document containing only the red mark as a color document when the document to be processed is a document with a red mark as shown in FIG. This processing is executed by the user selecting the red mark removal mode when reading the document image. The red mark removal mode is a mode prepared in advance as one of the original image reading modes. When the red mark removal mode is selected by the user, the pixel color determination area is set according to the area setting condition corresponding to the red mark removal mode.

That is, when the red mark removal mode is selected, in the pixel color determination area, as shown in FIG. 8, all the pixels included in the black and white area and the pixels included in the red area are all included. Is set to be determined as a black and white pixel,
All pixels included in the other areas are set so as to be determined as color pixels. The area setting in this case is also performed by appropriately switching the selection signal of the selector of the area determination unit corresponding to each area. Also,
In the red mark removal mode, the selection signal φSELA is switched so that the selector 30 in FIG. 5 outputs the output of the OR circuit 28 as the final pixel color determination result.

When the pixel G1 corresponding to the red mark of the document is to be determined in the pixel color determination area set under such conditions, the pixel G1 is included in any one area of the red area. . The area including the pixel G1 is
The pixels included in the area are set to be determined as black and white pixels. Therefore, as shown in FIG. 9, the determination result of the area including the pixel G1 is “1”. Therefore, the pixel G1 to be determined is determined as a monochrome pixel according to the determination result “1” of the area determination unit.

The pixel G2 corresponding to the monochrome portion of the original
Is included in any one of the black and white areas. The area including the pixel G2 is set so that the pixels included in the area are determined as black and white pixels. for that reason,
As shown in FIG. 10, the determination result of the area including the pixel G2 is “1”. Therefore, the determination target pixel G2
Are determined as black and white pixels according to the determination result “1” of the area determination unit.

On the other hand, a color pixel G3 other than red (in the illustrated example, an intermediate color pixel between blue and green) G3 is included in any one of the areas other than the black and white area and the red area. The area including the pixel G3 is set so that the pixels included in the area are determined as color pixels. Therefore, as shown in FIG. 11, the determination result of the area including the pixel G3 is “0”. Therefore, the determination target pixel G3
Are determined as color pixels according to the determination result “0” of the area determination unit.

By executing the processing based on the red mark removal mode, it is not necessary to determine a document including only the red mark as a color document as shown in FIG. That is, all documents including only the red mark can be determined to be monochrome documents. Therefore, when an image processing apparatus having the red mark removal mode is used to copy an image of a document with a color copier or the like, a user who wants to output a document with a red mark in black and white mode in order to save a copy fee. It becomes very convenient. In addition, for example, a designated color removal mode is prepared as a response to a color other than the red mark, and the same processing as described above is performed on a color designated by a user or the like in the designated color removal mode, so that all originals containing only the designated color can be processed. It is possible to determine that the document is a monochrome document. Incidentally, the designation of the color by the user may be performed using a user interface such as an edit pad as in the case of the ACS user selection mode.

Further, by appropriately changing the area setting condition of the pixel color determination area, it is possible to determine only a document including a red mark as a color document. Such processing is
In reading a document image, the process is performed by the user selecting the red mark reading mode. The red mark reading mode is a mode prepared in advance as one of the reading modes of the document image. When the user selects the red mark reading mode, the pixel color determination area is set according to the area setting condition corresponding to the red mark reading mode.

That is, when the red mark reading mode is selected, as shown in FIG. 12, in the pixel color determination area, the pixels included in the area within the red area are set to be determined as black and white pixels. All pixels included in the area outside the red area are set to be determined as color pixels. The area setting in this case is also performed by appropriately switching the selection signal of the selector of the area determination unit corresponding to each area. In the red mark reading mode, the selector 30 in FIG.
Is output as the final pixel color determination result.

When the pixel G1 corresponding to the red mark of the document is to be determined in the pixel color determination area set under such conditions, the pixel G1 is included in any one of the red areas in the pixel color determination area. Included in one area. This pixel G
The area including 1 is set so that the pixels included in the area are determined as black and white pixels. Therefore, FIG.
As shown in (1), the determination result of the area including the pixel G1 is “1”. However, in the red mark reading mode, the result of the inversion determination by the inverter 29 is set to be output as the final pixel color determination result. Therefore, the determination target pixel G1 is determined as a color pixel according to the inversion determination result “0” obtained by inverting the determination result of the area determination unit.

The pixel G2 corresponding to the monochrome portion of the original
Is included in any one area outside the red area in the pixel color determination area. The area including the pixel G2 is set so that the pixels included in the area are determined as color pixels. Therefore, as shown in FIG. 14, the determination result of the area including the pixel G2 is “0”. And
Ultimately, the pixel G2 is determined to be a black and white pixel according to the inversion determination result "1" obtained by inverting the determination result of the area determination unit.

Further, since the color pixel G3 other than red (in the illustrated example, an intermediate color pixel between blue and green) G3 is also included in any one area outside the red area in the pixel color determination area, as shown in FIG. The determination result of the area including the pixel G3 is “0”. Finally, the pixel G3 is determined to be a monochrome pixel according to the inversion determination result “1” obtained by inverting the determination result of the area determination unit.

By executing such a process based on the red mark reading mode, a document including only the red mark can be determined to be a color document. In addition, for example, a designated color reading mode is prepared as a response other than the red mark, and the same processing as described above is performed on the color designated by the user in the designated color reading mode, so that a document including only the designated color is converted to a color document. Can be determined. By the way,
The user can specify the color by using a user interface such as an edit pad in the same manner as in the ACS user selection mode.

Various modifications and applications are possible as a method of setting the pixel color judgment area in the pixel color judgment section 24. For example, as shown in FIG. 16, on the chromaticity plane, an achromatic region with low saturation is defined as a fixed black and white region, and a peripheral region of the black and white region is divided into a plurality of (16 in the example in the figure) areas. There is a case where a pixel color determination area is set. The black and white area in this case is an area that is explicitly recognized as black and white, and all the pixels included in this black and white area are determined as black and white pixels. By providing a fixed black and white area in this way, the number of area determination units can be reduced and the circuit configuration can be simplified.

In addition, in addition to the above, the pixel color determination area is configured to be variable according to the lightness (L * value), whereby the pixel color determination area is changed to the L * a * b * color space as shown in FIG. It may be set in a three-dimensionally expanded form above. Specifically, the brightness value (L * value) is divided into several levels on the L * axis, and a pixel color determination area corresponding to each brightness level is set on the chromaticity plane. When such a configuration is adopted, the brightness of the pixel to be determined is reflected in the pixel color determination, so that more accurate pixel color determination can be performed. Further, a similar effect can be obtained by a configuration in which a plurality of thresholds for dividing the pixel color determination area are changed according to the brightness.

In the above-described embodiment, the inside area other than the area that is explicitly recognized as a color on the chromaticity plane is set as the pixel color determination area.
For example, the minimum threshold value (THa1) and the maximum threshold value (THa6) corresponding to the a * axis are set to the minimum and maximum values that a * can take on the a * axis, and similarly, the minimum threshold value corresponding to the b * axis is set. The threshold (THb1) and the maximum threshold (THb6) are respectively set on the b * axis.
By setting the minimum and maximum values of b *,
It is also possible to configure so that the pixel to be determined is always included in any area in the pixel color determination area. When such a configuration is employed, various image reading modes (red-mark removal mode, red-mark reading mode, etc.) are supported without providing a judgment inversion unit by the inverter 29 and a judgment result selection unit by the selector 30. It becomes possible.

[0064]

As described above, according to the image processing apparatus of the present invention, the pixel color judgment means sets a pixel color judgment area divided by a plurality of areas on the chromaticity plane, and sets each area. Since the color / black and white determination in the above can be freely set, the color / black and white determination criterion can be optimized according to the needs of the user, and the function of the ACS processing can be improved. ACS using pixel color determination
In the process, it is possible to output a determination result that matches the user's preference and vision. This greatly contributes to improving reliability in the market, such as reducing complaints from users due to erroneous determination of a document color.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an image reading apparatus to which the present invention is applied.

FIG. 2 is a block diagram illustrating a control configuration of an image reading apparatus to which the present invention is applied.

FIG. 3 is a block diagram illustrating an internal configuration of an ACS processing unit.

FIG. 4 is a diagram illustrating a pixel color determination area.

FIG. 5 is a block diagram illustrating an internal configuration of a pixel color determination unit.

FIG. 6 is a flowchart illustrating a procedure for setting a pixel color determination area by a user.

FIG. 7 is a diagram illustrating a document with a red mark.

FIG. 8 is a diagram illustrating a setting condition of a pixel color determination area in a red mark removal mode.

FIG. 9 is a diagram (part 1) illustrating a determination result of a pixel color in a red mark removal mode.

FIG. 10 is a diagram (part 2) illustrating a result of determining a pixel color in the red mark removal mode.

FIG. 11 is a diagram (part 3) illustrating a determination result of a pixel color in a red mark removal mode.

FIG. 12 is a diagram illustrating a setting condition of a pixel color determination area in a red mark reading mode.

FIG. 13 is a diagram (part 1) illustrating a determination result of a pixel color in a red mark reading mode.

FIG. 14 is a diagram (part 2) illustrating a determination result of a pixel color in a red mark reading mode.

FIG. 15 is a diagram (part 3) illustrating a determination result of a pixel color in a red mark reading mode.

FIG. 16 is a diagram illustrating another method for setting a pixel color determination area.

FIG. 17 is a diagram illustrating still another setting method of the pixel color determination area.

FIG. 18 is a diagram illustrating a conventional pixel color determination method.

[Explanation of symbols]

16 ACS processing unit, 24 pixel color determination unit, 25 block color determination unit, 26 document color determination unit, 27 determination result output unit, 28 OR circuit, 29 inverter, 30 selector, E1 to E1 E25: Area judgment unit, CMP-1 to CMP-4 ...
Comparison circuit, AND-1 to AND-3: AND circuit, SEL-1 to SEL-25
…selector

Continued on the front page F term (reference) 5B057 AA11 BA02 CA01 CA02 CA08 CA12 CA16 CB18 CC01 CE16 CE18 CH08 5C077 LL19 MP08 PP32 PP36 PP43 PP48 PP68 PQ12 PQ20 SS01 TT06 5C079 HB01 HB08 LA03 LA10 MA11 NA03 PA02 5L09A A02 FA02 GA19 GA41

Claims (6)

[Claims] 1. An image processing apparatus comprising: a pixel color determination unit configured to determine whether a pixel constituting an image read by an image reading unit is a color pixel or a black and white pixel. A first determination unit configured to set a pixel color determination area divided into a plurality of areas, and determine which area of the pixel color determination area includes a pixel to be determined; For each divided area,
Area setting means capable of switching whether a pixel included in the area is determined to be a color pixel or a monochrome pixel; and the determination based on a determination result of the first determination means and a setting condition of the area setting means. An image processing apparatus comprising: a second determination unit configured to determine whether a target pixel is a color pixel or a monochrome pixel. 2. The method according to claim 1, wherein the pixel color determination unit includes: a determination inversion unit configured to invert a determination result obtained by the second determination unit; and a determination result obtained by the second determination unit or a determination result inverted by the determination inversion unit. The image processing apparatus according to claim 1, further comprising: a determination result selection unit that can be selected as a typical pixel color determination result. 3. The image processing apparatus according to claim 1, wherein the first determination unit sets an achromatic region as a fixed black and white region among the regions on the chromaticity plane, divides a peripheral region of the black and white region into a plurality of areas, and The image processing apparatus according to claim 1, wherein a determination area is set. 4. The image processing apparatus according to claim 1, wherein the pixel color determination area is variable according to brightness or an image reading mode. 5. The pixel color determination area is divided into the plurality of areas using a plurality of thresholds, and the plurality of thresholds are variable according to brightness or an image reading mode. The image processing device according to claim 1. 6. The area setting means receives a designation of a color by a user, and sets whether a pixel included in an area corresponding to the designated color is determined as a color pixel or a monochrome pixel. The image processing apparatus according to claim 1.