JP4758845B2 - Color classification apparatus, color classification method, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a digital copying machine, a printer, and a scanner, a color classification apparatus provided in the image forming apparatus, and a color classification method used for these, and more specifically, converts and outputs a color image into a two-color image. The present invention relates to a color classification device, a color classification method, and an image forming apparatus.

  In recent years, full-color printing machines capable of outputting full-color images are increasing instead of monochrome printing machines that output monochrome images. Full-color images look better than monochrome images, and because they can represent points that could not be represented by monochrome images, they are increasing their share.

  On the other hand, full-color images have a problem that the output unit price per sheet is high. Therefore, by making it possible to output a two-color image obtained by adding one color to a monochrome image, a balance between cost and expressiveness is secured.

  A two-color image can be obtained by subtractive color processing from a full-color image. However, depending on the processing method, even the same two-color image has different expressive power.

As a technique for obtaining a two-color image, for example, there is JP-A-8-84268. A feature point of a color image original is obtained by obtaining a density distribution with respect to hue, and two-color separation is performed from the information.
JP-A-8-84268

  As described above, depending on the processing method, even the same two-color image has different expressive power, so that it is required to obtain a two-color image with low cost and higher expressive power.

  SUMMARY An advantage of some aspects of the invention is that it provides a color classification device, a color classification method, and an image forming apparatus capable of outputting a two-color image with enhanced expressive power.

The present invention employs the following means in order to achieve the above object. That is, in the color classification device according to the present invention, the hue calculation means for calculating the hue value of the unit data constituting the input color image data, the saturation calculation means for calculating the saturation value of the unit data, and the plurality of divisions A first threshold value that is provided for each hue value that is divided into three groups in order of the saturation value, and a second threshold value that is greater than the first threshold value . Threshold storage means for storing. Further, the color classification device compares the calculated saturation value with the first threshold value corresponding to the calculated hue value, and the second threshold value , thereby comparing the three groups to which the unit data belongs. And a hue comparison unit that compares the calculated hue value with a hue value in a predetermined range . In addition, the color classification device does not extract unit data having a hue value different from the hue value in the predetermined range based on the comparison result by the hue comparison unit and the determination result by the saturation comparison unit. Unit data having a hue value in the range specified in advance, and unit data having a saturation value smaller than the first threshold is classified into a non-extracted color group, and the second data Classifying means for classifying unit data having a saturation value larger than a threshold value into an extracted color group and classifying unit data having a saturation value in a range from the first threshold value to the second threshold value into an intermediate color group is provided. Further, the color classification device includes a first conversion unit that converts unit data classified into the extracted color group and unit data classified into the non-extracted color group into a first output color and a second output color, respectively. And second conversion means for converting the unit data classified into the intermediate color group into a third output color obtained by mixing the first output color and the second output color at a predetermined ratio.

In this configuration, an intermediate color group is provided and unit data belonging to the intermediate color group is converted into a color in which the first output color and the second output color are mixed at a predetermined ratio, thereby increasing expressive power without increasing costs. The obtained two-color image can be obtained. Further, the color classification device according to the present invention is configured so that the unit data classified into the intermediate color group includes the first threshold value corresponding to the hue value to which the unit data belongs as the first output color and the second output color. And a second conversion means for converting into a third output color mixed at an output ratio corresponding to the degree of deviation from the second threshold. The color classification apparatus according to the present invention includes an output ratio storage unit that stores a plurality of output ratio tables that associate a hue value with a predetermined output ratio corresponding to the hue value, the calculated hue value, and a plurality of output ratio tables. Output ratio calculation means for calculating an output ratio corresponding to the calculated hue value based on the output ratio table corresponding to the hue value in the range specified in advance in the output ratio table, and the intermediate color Second conversion means for converting the unit data classified into groups into a third output color obtained by mixing the first output color and the second output color at the calculated output ratio. Also good. The color classification apparatus according to the present invention may further include an output unit that outputs unit data converted by the first conversion unit and the second conversion unit.

  Furthermore, an image forming apparatus having such a color classification apparatus and a color classification method realized by the processing procedure of the apparatus are also provided.

  By providing an intermediate color group and converting unit data belonging to the intermediate color group into a saturation value that is smaller than the unit data of the extracted color group, a two-color image with increased expressive power can be obtained without increasing costs. .

  Also, two threshold values are provided for each of the divided hues, and an extracted color group that should be clearly converted to the first output color, a non-extracted color group that should be clearly converted to the second output color, and its The image is divided into intermediate color groups corresponding to the intermediate. Then, the area corresponding to the intermediate color group is converted so that the saturation value after conversion becomes larger (smaller) stepwise. As a result, it is possible to obtain a two-color image with higher expressive power without increasing the cost.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.

  The image forming apparatus 101 according to the present invention will be described below.

  FIG. 1 is a schematic diagram of the image forming apparatus 100. However, details of each part not directly related to the present invention are omitted.

  The image forming apparatus 100 according to the present invention corresponds to, for example, a printer, a single scanner, or a multifunction machine including a printer, a copy, a scanner, a fax machine, and the like.

  As an example, the operation of the image forming apparatus when copying a document using a multifunction machine will be briefly described.

  For example, when a user prints a document using the multifunction device, the document is placed on the document table 103 or the table 105 shown in FIG. 1, and a print instruction is given to the operation panel provided near the document table. Do. When the instruction is given, printing is performed by operating the following units (drive units).

  That is, as shown in FIG. 1, the image forming apparatus 100 according to the present embodiment includes a main body 101 and a platen cover 102 attached above the main body 101. A document table 103 is provided on the upper surface of the main body 101, and the document table 103 is opened and closed by a platen cover 102. The platen cover 102 is provided with an automatic document feeder 104, a placing table 105, and a sheet discharging table 109.

  The automatic document feeder 104 includes a document conveyance path 108 formed inside the platen cover 102, a pickup roller 106 and a conveyance roller 107 provided inside the platen cover 102, and the like. The document conveyance path 108 is a document conveyance path that leads from the placement table 105 to the sheet discharge table 109 via a reading position P where reading is performed by the reading unit 110 provided in the main body 101.

  The automatic document feeder 104 pulls out each document placed on the placing table 105 to the inside of the transport path 108 by the pickup roller 106 and passes the document pulled out by the transport roller 107 and the like through the reading position P. The paper is discharged onto the paper base 109. When the document passes the reading position P, the document is read by the reading unit 110.

  The reading unit 110 is provided below the document table 103, and its details are shown in FIG. The reading unit 110 includes a first light source 111 that illuminates the document table 103 in the main scanning direction, a slit 116 that selectively passes light from the document table, and a mirror 112 that guides light from the document table. The movable carriage 117, the second movable carriage 118 including mirrors 113A and 113B that reflect the reflected light from the first movable carriage 117 again, and the lens group 119 that optically corrects the light guided by the mirror, An image sensor 115 that receives the light corrected by the lens group 119, and an image data generation unit 114 that converts the light received by the image sensor into an electrical signal and performs correction / correction as necessary. .

  When reading a document on the automatic document feeder 104, the light source 111 moves to a position where the reading position P can be irradiated and emits light. Light from the light source 111 is reflected by a document that passes through the document table 103 and passes through the reading position P, and is guided to the image sensor 115 by the slit 116, mirrors 112, 113A, and 113B, and the lens group 119. The image sensor 115 converts the received light into an electrical signal and transmits it to the image data generation unit 114. The light received by the image sensor 115 is input to the image data generator 114 as analog electrical signals of R (red), G (green), and B (blue), where analog-to-digital conversion is performed. Digitized. Further, the image data generation unit 114 uses the sequentially converted digital signal as unit data, and corrects and corrects the unit data to generate image data including a plurality of unit data.

  The reading unit 110 can read not only the document conveyed by the automatic document feeder 104 but also the document placed on the document table 103. When reading a document placed on the document table 103, the first carriage 112 moves in the sub-scanning direction while emitting light from the light source 111, so that the optical path length from the light source 111 to the image sensor 115 is constant. The second moving carriage 118 moves in the direction of the image sensor 115 at a half speed of the first moving carriage 117.

  The image sensor 115 electrically outputs light from the document placed on the document table 103 based on the light guided to the mirrors 112, 113 </ b> A, 113 </ b> B, as in the case of the document conveyed to the automatic document feeder 104. The signal is converted into a signal, and based on this, the image data generation unit 114 generates image data.

  A printing unit 120 that prints image data is provided below the reading unit 110 of the main body 101. Image data that can be printed by the printing unit 120 is generated by the image data generation unit 114 as described above, or transmitted from a terminal such as a personal computer connected to the image forming apparatus 100 and a network such as a LAN. It is.

  As a printing method performed by the printing unit 120, an electrophotographic method is used. That is, the photosensitive drum 121 is uniformly charged by the charger 122, and then the photosensitive drum 121 is irradiated by the laser 123 to form a latent image on the photosensitive drum 121, and toner is attached to the latent image by the developing device 124. In this method, a visual image is formed and the visible image is transferred onto a sheet by a transfer roller.

  Note that in the image forming apparatus corresponding to the full-color image, the developing device (rotary developing device) 124 is rotated in the circumferential direction around a rotation axis configured in a direction perpendicular to the paper surface of FIG. A developing unit in which color toner is stored is disposed at a position facing the photosensitive drum 121. In this state, the latent image on the photosensitive drum 121 is developed with toner stored in the developing device 124 and transferred to the intermediate transfer belt 125A. The developing device 124 includes four developing units 124 (Y), (C), (M), and yellow (Y), cyan (C), magenta (M), and black (K). (K). By repeating the transfer to the intermediate transfer belt 125A for each color, a full color image is formed on the intermediate transfer belt 125A.

  The paper on which the visible image is printed is placed on a paper feed tray such as the manual feed tray 131 and the paper feed cassettes 132, 133, and 134.

  When the printing unit 120 performs printing, one sheet of paper is pulled out from any one of the paper feed trays using the pickup roller 135, and the pulled-out paper is transferred to the intermediate transfer belt 125 </ b> A by the transport roller 137 or the registration roller 138. Feed between rollers 125B.

  When the visible image on the intermediate transfer belt 125 is transferred onto the sheet fed between the intermediate transfer belt 125 and the transfer roller 125, the printing unit 120 uses the conveying belt 126 to fix the visible image. Send paper to 127. The fixing device 127 includes a heating roller 128 with a built-in heater and a pressure roller 129 pressed against the heating roller 128 with a predetermined pressure. When the sheet passes between the heating roller 128 and the pressure roller 129, the visible image is fixed to the sheet by heat and the pressing force to the sheet. The printing unit 120 discharges the sheet that has passed through the fixing device 127 to the discharge tray 130.

  The basic copy service processing in the image forming apparatus 100 has been described above.

  In the image forming apparatus 100, as shown in the schematic configuration diagram of FIG. 3, a central processing unit (CPU) 301, a random access memory (RAM) 302, a read only memory (ROM) 303, and a hard disk drive (HDD). 304 and a driver 305 corresponding to each drive unit in the printing process are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, and the like, and exchanges data and commands with the driver 305 based on the execution result, thereby performing the above-described FIG. 2 controls the operation of each driving unit 307 shown in FIG.

  Next, details of the color classification unit 400 according to the present invention will be described.

  The color classification unit 400 can be provided as, for example, a color classification device provided in the image data generation unit 114 or connected to the image data generation unit 114.

  The color classification unit 400 performs processing for classifying unit data constituting a color original into two colors when outputting the color original as a two-color image. The user can select a color to be extracted from the color document (extracted color) and two colors (first output color and second output color) for outputting the extracted color before printing. For example, when it is desired to extract a blue portion of a color document, “extracted color = blue” is set from an operation panel provided near the document table. The setting is stored in the extracted color storage unit 407 described later.

  When the user wants to output the extracted color “blue” as “red”, the user selects “red” as the first output color from the operation panel. The selected first output color is stored in first output color storage means 411 described later. Here, it is assumed that the second output color is fixed to “gray (achromatic color)” and the “gray” is stored in the second output color storage unit 412 described later. Further, a third output color to be described later is determined from the first output color and the second output color.

  When the color classification unit 400 obtains color image data based on RGB from the data generation unit 114 by the image data input unit 401, the color image data is obtained by, for example, yellow (Y), cyan (C), magenta ( M) is converted into density image data. Since the conversion is performed by a predetermined conversion formula that has been conventionally used, details are omitted. When the image data input unit 401 receives image data transmitted via a network, for example, the image data input unit 401 performs the above conversion on the image data so that the transmitted data is also input from the data generation unit 114. Can be handled in the same way.

  The density image data input / converted by the image data input unit 401 is input to the hue calculation unit 402 and the saturation calculation unit 403 for each unit data, and the hue and saturation are calculated for each unit data.

  For example, when calculating the hue, it is performed as follows.

First, when the unit data (C, M, Y) is input, the hue calculation unit 402 calculates the maximum value (MAX), the minimum value (MIN), and the difference value (MAXMIN) between the maximum value and the minimum value. . C, M, and Y are values from 0 to 255 represented by 8 bits, for example.
1) Here, C is the minimum value compared with M and Y, and MAXMIN ≠ 0,
Further, when Y> M, hue value = 42 + (Y−M) × 42 ÷ MAXMIN is calculated.

When Y <= M, hue value = 42− (MY) × 42 ÷ MAXMIN is calculated.

Further, when MAXMIN = 0, hue value = 42 is calculated.
2) Note that M is the minimum value compared to C and Y, and MAXMIN ≠ 0,
Further, when C> Y, hue value = 127 + (C−Y) × 42 ÷ MAXMIN is calculated.

When C <= Y, hue value = 127− (Y−C) × 42 ÷ MAXMIN.

Further, when MAXMIN = 0, the hue value is calculated as 127.
3) Y is the minimum value compared to C and M, and MAXMIN ≠ 0,
Further, when M> C, hue value = 212 + (M−C) × 42 ÷ MAXMIN is calculated.

Further, when M <= C, hue value = 212− (C−M) × 42 ÷ MAXMIN is calculated.

Further, when MAXMIN = 0, the hue value is calculated as 212.

  As described above, the hue value of the unit data is calculated by the hue calculation unit 402. The calculated hue value can take 256 values from 0 to 255.

  Further, when the unit data (C, M, Y) is input, the saturation calculation unit 403 calculates the maximum value (MAX), the minimum value (MIN), and the difference value (MAXMIN) between the maximum value and the minimum value. To do.

And if MAXMIN is not 0,
Saturation value = MAXMIN × 255 ÷ MAX.

If MAXMIN is 0,
Saturation value = 0 is calculated.

  Thus, the saturation value of the unit data is calculated by the saturation calculation unit 403. The calculated saturation value can take 256 values from 0 to 255.

  By the above calculation, the hue value and saturation value of the unit data are calculated. The set of calculated values can be represented by the hue circle in FIG. That is, for example, the calculated hue value can be expressed as a value in the circumferential direction in the hue circle of FIG. Of groups are represented. At the end point 502, the hue value is 255.

  Further, the saturation value indicates a position when the center from the center 503 of the hue circle to the circumference is divided into 256 equal parts, the center 503 has a saturation value of 0, and the saturation value has a saturation value of 255.

  By the way, in the two-color image, the boundary between the color area and the gray area is particularly important, and the appropriate degree of the gray area differs depending on the hue of human eyes. For example, among the two substantially elliptical shapes 504 and 505 shown in FIG. 5, the inside of the substantially elliptical shape 504 located on the inner periphery indicates the most appropriate gray appropriate region in the two-color image. Further, an appropriate area of the output color most suitable for the two-color image is shown between the outside of the substantially elliptical shape 505 located on the outer periphery and the circumference 506. That is, in the present application, processing is performed to make the ratio of the area where gray is appropriate and the ratio of the area where color area is appropriate for each hue. Then, an intermediate area between the substantially elliptical shapes 504 and 505 is newly determined as an intermediate area. The substantially oval shapes 504 and 505 are merely examples, and the appropriate gray and color areas may be indicated by other shapes, but here, each area indicated by the two approximately oval shapes indicates the appropriate area. Explain that it is.

  The color classification unit 400 in the present application determines unit data of a gray area, a color area, and an intermediate area based on the appropriate area.

  That is, the hue value of the unit data calculated by the hue calculation unit 402 is input to the saturation comparison unit 405 and the hue comparison unit 406.

  The hue comparison unit 406 to which the hue value is input compares the hue value with the extracted color designated by the user acquired from the extracted color storage unit 407.

  Here, since the extracted color stored in the extracted color storage unit 407 is “blue”, the hue comparison unit 406 uses the hue determination table for blue to determine whether the unit data corresponds to “blue”. Determine whether or not. Here, blue is defined in advance to fall within the range of 154 to 188 in terms of hue value.

  That is, the hue comparison unit 406 indicates that the hue value input from the hue calculation unit 402 falls within the range of 154 to 188 shown in FIG. Value) "is output to the classification means 409. If the input hue value is not within the range of 154 to 188, for example, “0” indicating that it corresponds to a non-extracted color is output to the classification means 409. By the processing of the hue comparison unit 406, the region 701, the region 702, and the region 703, which are shown in a substantially fan shape in FIG. When another color different from blue (for example, yellow) is selected, a hue determination table corresponding to the other color is used.

  The saturation comparison unit 405 that has acquired the hue value of the unit data from the hue calculation unit 402 and has acquired the saturation value of the unit data from the saturation calculation unit 403 is acquired from the hue calculation unit 402 from the threshold storage unit 408. A first threshold value (a saturation value serving as a threshold value) and a second threshold value corresponding to the hue value are acquired. The two threshold values are provided for each of the divided 256 hue values, that is, 512 threshold values are stored in advance. The threshold value indicates the distance (coordinates) from the center 503 when the center 503 is “0” and the circumference is “255”, and the first threshold corresponding to each hue value is connected to form a substantially elliptical shape. The circumference (contour) of the shape 504 is formed. Further, the circumference (contour) of the substantially elliptical shape 505 is formed by connecting the second threshold value corresponding to each hue value.

  Note that the two threshold values forming the circumference of the substantially elliptical shapes 504 and 505 are indicated by a graph composed of the hue value on the horizontal axis and the saturation value on the vertical axis, and the region determination table 801 in FIG. Shown in A group having a saturation value from 0 to the first threshold value 504 corresponds to the gray area 804, and a group from the first threshold value 504 to the second threshold value 505 corresponds to the intermediate color area 803, and the second threshold value. A group from 505 to 255 corresponds to the color region 802. The saturation comparison unit 405 determines whether the unit data belongs to the group of the color area (802) or the intermediate color area (803) based on the hue value and saturation value of the input unit data and the area determination table 801. ) Group or a gray region (804) group.

  Here, when the saturation value corresponding to the input hue value is in the range from 0 to the first threshold value 504, for example, “0” indicating that fact is transmitted to the classification unit 409. In other words, when “0” is output, it means that it belongs to the substantially oval shape (GRAY area) 504 shown in FIG.

  When the saturation value is in the range from the first threshold value 504 to the second threshold value 505, for example, “1” indicating that fact is transmitted to the classification means 409. In other words, when “1” is output, it means that it belongs to the region between the substantially elliptical shape 504 and the substantially elliptical shape 505 shown in FIG.

  If the saturation value is in a range larger than the second threshold value 505, for example, “2” indicating that fact is transmitted to the classification means 409. In other words, when “2” is output, it means that it belongs to the area from the substantially elliptical shape 505 shown in FIG. 7 to the circumference, that is, the color area 802.

  Subsequently, when the comparison result from the hue comparison unit 406 and the comparison result from the saturation comparison unit 405 are acquired, the classification unit 409 determines whether the unit data is an extracted color group or an intermediate color group based on the two comparison results. And classify into non-extracted color groups.

  For example, if the comparison result from the hue comparison unit 406 is “0”, it means that the area other than the user designated as the extracted color, that is, the unit data belongs to an area other than the areas 701, 702, and 703. The extracted color group is determined.

  When the comparison result from the hue comparison unit 406 is “1 (value greater than 0)” and the comparison result from the saturation comparison unit 405 is “0”, the hue value is the extracted color selected by the user. This means that the saturation value corresponds to the gray region 804. That is, the unit data belongs to the area 703 (GRAY) shown in FIG. 7, and is determined as a non-extracted color group.

  When the comparison result from the hue comparison unit 406 is “1 (value greater than 0)” and the comparison result from the saturation comparison unit 405 is “1”, the hue value is the extracted color selected by the user. This means that the saturation value corresponds to the intermediate color region 803. That is, it means that the unit data belongs to the area 702 shown in FIG. 7, and it is determined as an intermediate color group.

  When the comparison result from the hue comparison unit 406 is “1 (value greater than 0)” and the comparison result from the saturation comparison unit 405 is “2”, the hue value is the extracted color selected by the user. This means that the saturation value corresponds to the color region 802. That is, it means that the unit data belongs to the area 701 shown in FIG.

  FIG. 9 shows an output color group distribution diagram 901 after the classification means 409 classifies the unit data into an extracted color group, a non-extracted color group, and an intermediate color group.

  Subsequently, the determination result is transmitted to the conversion unit 410, and the conversion unit 410 converts the output color. The conversion is performed as follows, for example. First, when it is determined that the unit data belongs to the non-extracted color group, the first conversion unit 410A constituting the conversion unit 410 uses the second output color (stored in the second output color storage unit 412). Strictly speaking, in the case of gray, since it does not correspond to a hue, if it includes gray, the hue is expressed as a color), that is, it is converted to gray.

  If it is determined that the unit data belongs to the extracted color group, the first conversion means 410A is selected by the user, and the first output color stored in the first output color storage means 411, that is, Convert to red.

If it is determined that the unit data belongs to the intermediate color group, the second conversion unit 410B constituting the conversion unit 410 is selected by the user, and the first output color (here, red) and the second output unit are selected. The output color (in this case, gray) is mixed (integrated) at a predetermined ratio into an intermediate output color, that is, a third output color. When the second output color is gray, the third output color has the same hue as the first output color and a lower saturation than the color. An example of the conversion process to the third output color is shown below.
(First conversion processing example)
The output color red stored in the first output color storage unit 411 is represented by (C, M, Y, K) = (0, 255, 255, 0), for example, and the second output color. It is assumed that the output color gray stored in the storage means 412 is represented by (C, M, Y, K) = (0, 0, 0, 128), for example. In this case, as the intermediate output color, for example, the first output color (red) and the second output color (gray) are mixed (integrated) at a ratio of 1: 1 (50%: 50%). . By the above mixing, the intermediate output color is converted into, for example, (C, M, Y, K) = (0, 128, 128, 128).

  The unit data converted by the conversion unit 410 is maintained for each unit data by the output unit 413 or until all unit data is converted, and is output as converted image data.

  The output unit data or converted image data is transmitted to the printing unit 120 described above and printed as a converted two-color image. Thereby, the first output color (for example, red), the second output color (for example, black, gray), and the third output color (the first output color and the second output color are mixed at a predetermined ratio). Color) can form a two-color image.

As described above, an intermediate color group is provided, and unit data belonging to the intermediate color group is converted into a color in which the first output color and the second output color are mixed at a predetermined ratio, so that expressive power can be increased without increasing costs. An increased two-color image can be obtained.
(Second conversion processing example)
Further, the intermediate output color may be converted more finely. For example, the second conversion unit 410B converts the first output color and the second output color from the first threshold value 504 and the second threshold value 505 corresponding to the hue value to which the unit data belongs. This is converted into a third output color mixed at an output ratio corresponding to the degree of deviation.

  More specifically, as shown in FIG. 10, the unit data belonging to the area 1001 determined as the extracted color is converted into the first output color, that is, red, for example, as described above. Here, focusing on the unit data 1002 to 1005 whose hue value belongs to 154 and is determined to be an intermediate color, the unit data 1002 having the saturation value A corresponding to (matching) the second threshold 505 is the above-described first unit data 1002. Is converted to the same saturation value as the output color. Further, the converted saturation value of the unit data 1005 having the saturation value corresponding to (matching with) the first threshold value 504 is the second output color (for example, black) corresponding to the area determined as the non-extracted color. , Gray) and the same saturation value. For unit data 1003 and 1004 that are larger than the first threshold 504 and smaller than the second threshold, for example, according to the degree of deviation from the first threshold 504 and the second threshold 505, The first output color and the second output color are converted into saturation values that are mixed at a predetermined ratio. Here, the “predetermined ratio according to the degree of divergence” refers to the reciprocal of the degree of divergence of the saturation value of the unit data from the first threshold (the saturation value of the unit data−the first threshold), It refers to the ratio to the reciprocal of the degree of deviation from the second threshold (second threshold—the saturation value of the unit data).

In the above example,
Deviation from first threshold at 154 = (first threshold corresponding to saturation value-154 of unit data) / (first threshold corresponding to second threshold-154 corresponding to 154) ..X
Degree of deviation from the second threshold at 154 = (1−X)... Y
Defined as
The predetermined ratio is
First output color (red): second output color (gray) = Y: X
As required.

In the above example, X and Y are calculated as coefficients having a value of 1 or less,
The unit data color element (CMYK) = Y × (first output color color element) + X × (second output color element).

  Based on the above, the unit data 1003 closer to the first output color (red) than the unit data 1004 is given a saturation closer to red than the unit data 1004. Conversely, the unit data 1004 Saturation closer to gray than data 1003 is given.

  By performing the conversion for each hue value, the saturation value of the unit data belonging to the intermediate color group gradually increases from the vicinity of the first threshold value 504 toward the second threshold value 505. That is, the area 1006 determined to belong to the intermediate color group is converted so as to form a gradation in which the saturation value increases from the bottom to the top in FIG.

As described above, two threshold values are provided for each of the divided hues, and an extracted color group to be clearly converted to the first output color and a non-extracted color group to be clearly converted to the second output color And an intermediate color group corresponding to the middle. Then, the area corresponding to the intermediate color group is converted so that the saturation value after conversion becomes larger (smaller) stepwise. As a result, it is possible to obtain a two-color image with higher expressive power without increasing the cost.
(Third conversion processing example)
In the second conversion processing example, the output color is converted to form a gradation in the saturation direction. However, the output color may be converted to form a gradation in the hue direction (circumferential direction). Good.

  In this case, as shown in FIG. 11, the color classification unit 1101 is newly based on the output ratio storage unit 1102 that stores the output ratio table, the hue value calculated by the hue calculation unit 402, and the output ratio table. Output ratio calculation means 1103 for calculating the output ratio of the hue value after conversion.

  As shown in FIG. 12, the output ratio table is a table in which a hue value is assigned to the X axis and a converted output ratio corresponding to the hue value is assigned to the Y axis. The table of FIG. 12 is a table for blue (hue value range 154 to 188) selected when blue is stored in the extracted color storage unit 407. For example, a plurality of tables for CMYRG are also included. Is remembered.

  In the above state, for example, the hue of the unit data is calculated as “162” by the hue calculation unit 402. The hue value is transmitted to the output ratio calculation unit 1103, and the output ratio calculation unit 1103 stores the output ratio table 1201 corresponding to the blue on the basis of “blue” set in the extracted color storage unit 407. Read from the storage means 1102.

  Subsequently, the output ratio calculation unit 1103 calculates the converted output ratio Z = 82% from the hue value “162” and the output ratio table 1201. The calculated value is transmitted to the second conversion unit 410B.

  In the second conversion means 410B, a third output obtained by mixing the first output color (red) and the second output color (gray) at the calculated output ratio (here 82:18). Convert to color.

In the above example, Z is calculated as a coefficient having a value of 1 or less,
The unit data color element (CMYK) = Z × (first output color color element) + (1−Z) × (second output color element).

  With the above processing, as shown in FIG. 13, with respect to the hue direction, a color closer to the extracted color is output with an element closer to the first output color (red), and a color farther from the extracted color is output to the second output color ( Since it is output with elements close to (gray), it is possible to obtain a two-color image with further increased expressive power.

When the third conversion processing example and the second conversion processing example are performed at the same time, the second conversion means 410B converts the color element of the unit data into
{Y × Z × (color element of first output color)} + {{1− (Y × Z)} × (color element of second output color)}
Calculate as

  As a result, with respect to both the hue direction and the saturation direction, a color closer to the extracted color is output as an element closer to the first output color (red), and a color farther from the extracted color is output to the second output color (gray). Therefore, a two-color image close to a color image can be obtained.

  In the above description, only the hue and saturation conversion is described for the color when the conversion unit 410 converts, and the luminance is not mentioned. Luminance is also affected by the characteristics of each color toner (CMYK) used by the apparatus, and therefore conversion unique to the apparatus is performed based on these characteristics. Thus, although the present application does not limit the luminance conversion, it goes without saying that the conversion means may convert the luminance according to the extracted color or output color selected by the user.

  Further, although the conversion means converts the extracted color into the output color designated by the user, the designated extracted color may be used as it is.

  Furthermore, for the sake of understanding, a hue value determination table and an output ratio table are provided separately, but the hue value determination table can be replaced with an output ratio table. In this case, the classification by the classification unit 409 is determined based on the comparison of the comparison result from the hue comparison unit 406 based on “0” and “greater than 0” instead of “0” and “1”. Just do it.

  The color classification apparatus, the color classification method, and the image forming apparatus according to the present invention are useful as a color classification apparatus, a color classification method, and an image forming apparatus that can provide a two-color image with rich expressive power.

1 is a schematic diagram of an image forming apparatus according to the present invention. The enlarged view of a reading part. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. 1 is a schematic functional block diagram of an image forming apparatus according to the present invention. The figure which shows a hue circle. The figure which shows an example of a hue classification | category table. The figure which shows the extraction area | region of a hue circle, and a non-extraction area | region. The figure which shows the example of an area | region determination table. The figure which shows distribution of an output color group. The figure explaining the relationship of the saturation value after conversion. FIG. 6 is a schematic functional block diagram of an image forming apparatus according to another embodiment of the present invention. The figure which shows an example of an output ratio table. The 2nd figure explaining the relationship of the saturation value after conversion.

Explanation of symbols

400 Color classification means 401 Image data input means 402 Hue calculation means 403 Saturation calculation means 405 Saturation comparison means 406 Hue comparison means 407 Extracted color storage means 408 Threshold storage means 409 Classification means 410 Conversion means 410A First conversion means 410B First Second conversion means 411 First output color storage means 412 Second output color storage means 413 Output means 1102 Output ratio storage means 1103 Output ratio calculation means

Claims (8)

A hue calculation means for calculating a hue value of unit data constituting the input color image data;
A saturation calculating means for calculating the saturation value of the unit data;
A threshold value provided for each of the hue values divided into a plurality of values, a first threshold value for dividing the saturation value in each hue value into three groups in the order of the saturation value, and greater than the first threshold value Threshold storage means for storing a second threshold ;
Saturation comparison for determining the three groups to which the unit data belongs by comparing the calculated saturation value, the first threshold value corresponding to the calculated hue value, and the second threshold value Means,
A hue comparison means for comparing the calculated hue value with a hue value in a predetermined range;
Based on the comparison result by the hue comparison unit and the determination result by the saturation comparison unit, unit data having a hue value different from the hue value in the range specified in advance is classified into a non-extracted color group, and Unit data having a hue value in a pre-designated range, the unit data having a saturation value smaller than the first threshold is classified into a non-extracted color group, and a saturation value larger than the second threshold is determined. Classifying means for classifying unit data having an extracted color group and classifying unit data having a saturation value in a range from the first threshold to the second threshold into an intermediate color group ;
First conversion means for converting the unit data classified into the extracted color group and the unit data classified into a non-extracted color group into a first output color and a second output color, respectively;
Second conversion means for converting the unit data classified into the intermediate color group into a third output color obtained by mixing the first output color and the second output color at a predetermined ratio;
Color classification device with A hue calculation means for calculating a hue value of unit data constituting the input color image data;
A saturation calculating means for calculating the saturation value of the unit data;
A threshold value provided for each of the hue values divided into a plurality of values, a first threshold value for dividing the saturation value in each hue value into three groups in the order of the saturation value, and greater than the first threshold value Threshold storage means for storing a second threshold ;
Saturation comparison for determining the three groups to which the unit data belongs by comparing the calculated saturation value, the first threshold value corresponding to the calculated hue value, and the second threshold value Means,
A hue comparison means for comparing the calculated hue value with a hue value in a predetermined range;
Classification means for classifying the unit data into an extracted color group, a non-extracted color group, or an intermediate color group based on the comparison result by the hue comparison means and the determination result by the saturation comparison means;
First conversion means for converting the unit data classified into the extracted color group and the unit data classified into a non-extracted color group into a first output color and a second output color, respectively;
The unit data classified into the intermediate color group, the degree of deviation from the first threshold and the second threshold corresponding to the hue value to which the unit data belongs between the first output color and the second output color Second conversion means for converting to a third output color mixed at an output ratio according to
Color classification device with A hue calculation means for calculating a hue value of unit data constituting the input color image data;
A saturation calculating means for calculating the saturation value of the unit data;
Threshold value storage means for storing two threshold values, each of which is a threshold value provided for each of hue values divided into a plurality of values and divides the saturation value in each hue value into three groups in the order of the saturation value;
A saturation comparison unit that determines the three groups to which the unit data belongs by comparing the calculated saturation value with the two threshold values corresponding to the calculated hue value;
A hue comparison means for comparing the calculated hue value with a hue value in a predetermined range;
Classification means for classifying the unit data into an extracted color group, a non-extracted color group, or an intermediate color group based on the comparison result by the hue comparison means and the determination result by the saturation comparison means;
First conversion means for converting the unit data classified into the extracted color group and the unit data classified into a non-extracted color group into a first output color and a second output color, respectively;
Output ratio storage means for storing a plurality of output ratio tables associating a hue value with a predetermined output ratio corresponding to the hue value;
Based on the calculated hue value and the output ratio table corresponding to the hue value in the predetermined range among the plurality of output ratio tables, an output ratio corresponding to the calculated hue value is calculated. An output ratio calculating means for calculating;
Second conversion means for converting the unit data classified into the intermediate color group into a third output color obtained by mixing the first output color and the second output color at the calculated output ratio;
Color classification device with Further, the first conversion means and the second color classification apparatus according to any one of claims 1 -3 comprising output means for outputting the converted unit data at converting means. An image forming apparatus having a color classification apparatus according to any one of claims 1-4. A hue calculation step for calculating a hue value of unit data constituting the input color image data;
A saturation calculation step for calculating a saturation value of the unit data;
The threshold value provided for each of the divided hue values corresponding to the calculated hue value and the calculated hue value, and the saturation value in each hue value is 3 in the order of the saturation value. A saturation comparison step of determining the three groups to which the unit data belongs by comparing a first threshold to be divided into groups and a second threshold greater than the first threshold;
A hue comparison step for comparing the calculated hue value with a predetermined range of hue values;
Based on the comparison result in the hue comparison step and the determination result in the saturation comparison step , classify unit data having a hue value different from the hue value in the predetermined range into a non-extracted color group, Unit data having a hue value in a pre-designated range, the unit data having a saturation value smaller than the first threshold is classified into a non-extracted color group, and a saturation value larger than the second threshold is determined. Classifying unit data having an extracted color group, and classifying unit data having a saturation value ranging from the first threshold to the second threshold into an intermediate color group ;
A first conversion step of converting the unit data classified into the extracted color group and the unit data classified into the non-extracted color group into a first output color and a second output color, respectively;
A second conversion step of converting the unit data classified into the intermediate color group into a third output color obtained by mixing the first output color and the second output color at a predetermined ratio;
Color classification method with A hue calculation step for calculating a hue value of unit data constituting the input color image data;
A saturation calculation step for calculating a saturation value of the unit data;
The threshold value provided for each of the divided hue values corresponding to the calculated hue value and the calculated hue value, and the saturation value in each hue value is 3 in the order of the saturation value. A saturation comparison step of determining the three groups to which the unit data belongs by comparing a first threshold to be divided into groups and a second threshold greater than the first threshold;
A hue comparison step for comparing the calculated hue value with a predetermined range of hue values;
A classification step for classifying the unit data into an extracted color group, a non-extracted color group, or an intermediate color group based on the comparison result in the hue comparison step and the determination result in the saturation comparison step;
A first conversion step of converting the unit data classified into the extracted color group and the unit data classified into the non-extracted color group into a first output color and a second output color, respectively;
The unit data classified into the intermediate color group, the degree of deviation from the first threshold and the second threshold corresponding to the hue value to which the unit data belongs between the first output color and the second output color A second conversion step for converting to a third output color mixed at an output ratio according to
Color classification method with A hue calculation step for calculating a hue value of unit data constituting the input color image data;
A saturation calculation step for calculating a saturation value of the unit data;
The threshold value provided for each of the divided hue values corresponding to the calculated hue value and the calculated hue value, and the saturation value in each hue value is 3 in the order of the saturation value. A saturation comparison step of determining the three groups to which the unit data belongs by comparing two threshold values divided into groups;
A hue comparison step for comparing the calculated hue value with a predetermined range of hue values;
A classification step for classifying the unit data into an extracted color group, a non-extracted color group, or an intermediate color group based on the comparison result in the hue comparison step and the determination result in the saturation comparison step;
A first conversion step of converting the unit data classified into the extracted color group and the unit data classified into the non-extracted color group into a first output color and a second output color, respectively;
Among the plurality of output ratio tables associating the calculated hue value with the hue value and a predetermined output ratio corresponding to the hue value, the output ratio table corresponding to the hue value in the range specified in advance. An output ratio calculating step for calculating an output ratio corresponding to the calculated hue value,
A second conversion step of converting the unit data classified into the intermediate color group into a third output color obtained by mixing the first output color and the second output color at the calculated output ratio;
Color classification method with

Images