JP5067277B2 - Image processing apparatus, image processing method, image processing program, copying apparatus, copying method, and copying program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing method, an image processing program, a copying apparatus, a copying method, and a copying program.

  In a copying apparatus, a document is copied by performing printing based on image data read by the document reading device. Normally, in such a copying apparatus, input image data indicating a reading result of the document reading apparatus is converted into output image data by a profile, and the color of the output apparatus is specified by the output image data. By performing processing based on various ideas at the time of this color conversion, various functions can be realized along with copying. For example, it is not preferable to faithfully reproduce the background color and show-through for a document whose background is not white or a document with show-through. In view of this, a technique is known that removes the background and show-through by uniformly converting the input image data to pixels having a certain brightness or higher to the maximum brightness.

Also, if pixels having a certain brightness or higher are uniformly converted to the maximum brightness, a tone jump occurs between the brightness areas that are not converted. In order to prevent this tone jump, a method of converting the brightness so as to smoothly change in a brightness range equal to or lower than the certain brightness has been proposed (for example, Patent Document 1).
JP 2006-67233 A

However, in the technique described in Patent Document 1, only a specific region (a predetermined hue range and a predetermined saturation range) is processed in the L ^* a ^* b ^* space in order to maintain the reproducibility of yellow and skin color. Yes. Therefore, there has been a problem that tone jump occurs inside and outside a specific area in the L ^* a ^* b ^* space, resulting in poor appearance.

  The present invention has been made in view of the above problems, and an image processing apparatus and an image that can prevent occurrence of a tone jump not only in the brightness direction but also in the saturation direction and the hue direction while removing the background and the show-through It is an object to provide a processing method, an image processing program, a copying apparatus, a copying method, and a copying program.

  In order to solve the above problems, the image processing apparatus according to the present invention includes an image data input unit and a color conversion unit. The color conversion means converts the input image data to obtain output image data indicating the output color in the output device, and converts a color whose brightness exceeds a predetermined threshold to the maximum brightness, and is equal to or lower than the threshold. Conversion is performed so that the brightness changes smoothly in the brightness range, and the saturation of the color is converted to 0 when the color having the highest brightness is the color in a specific area in the color space. .

  That is, by converting a color whose lightness exceeds a predetermined threshold value into a constant lightness color, it is possible to remove the show-through that should be a constant color, but since the change in lightness below the threshold value is smooth, It can suppress that the brightness changes rapidly with color conversion. At this time, it is desirable that the color of the highest brightness is white with zero saturation, but the saturation may not be zero depending on the background color of the document from which the input image data is based. Therefore, for the color converted to the maximum brightness, the saturation is converted to 0 when the color is in a specific region in the color space. For example, if the specific area is an L * a * b * space, it can be specified by saturation and hue angle. Therefore, it is possible to prevent the occurrence of the show-through and to prevent the tone jump in the lightness direction and to prevent the tone jump in the saturation direction and the hue angle direction.

  Here, the input image data may be data in which colors are specified for a plurality of pixels, and is usually one color component (such as brightness) for a monochrome image, and usually three color components for a color image. Any data may be used as long as the gradation is designated for each. The image data input means only needs to be able to input such input image data. However, as a configuration for removing the background color and show-through of the original, data obtained by reading the original with an image reading device is used as the input image. It is preferable to use data. According to such a configuration, even when a background color or show-through that is originally unnecessary is read by the image reading device, these can be appropriately removed.

  In the color conversion means, when the input image data is converted into the output image data, it is sufficient that the color system employed in each image data can be converted. That is, the input image data is data representing colors in the color system employed when generating this data (for example, when reading by the image reading device), and the output image data is the output device (for example, printing) Data representing the color in the color system used in the apparatus. As described above, the color expressed by the data used in the image reading apparatus or the printing apparatus is usually a device-dependent color. Therefore, even if the color components of both color systems match, it cannot be said that the color indicated by the gradation value is the same, and the color conversion means selects the same color as that color for each pixel of the input image data. Output image data is generated so as to be the data shown.

  Usually, color conversion is performed with reference to a profile. That is, color conversion is performed using a color conversion table or a function that defines the correspondence between the color systems using a color conversion table or a function that defines the correspondence between the color systems. Of course, the profile may be a profile in which the color system in the input image data is directly associated with the color system in the output image data, or the input image data and other color systems (for example, device-independent colors). Color conversion may be performed with reference to a first profile that associates (space) with the second profile that associates output image data with another color system (for example, a device-independent color space). Of course, in addition to a configuration in which a profile is created in advance and conversion is performed so that the brightness changes smoothly in the brightness range below the threshold by referring to this profile, processing for input image data, for example, processing for output The color conversion according to the present invention may be performed every time the operation is performed, and various configurations may be employed.

  The predetermined threshold value may be determined so that the show-through color and the background color to be removed are included in a brightness range larger than that. By converting the color exceeding the threshold value into a color having a certain brightness, the show-through and the background color can be removed. In addition, various configurations can be employed for conversion so that the brightness changes smoothly in the brightness range below the threshold value. That is, it is only necessary that conversion can be performed so as to prevent the lightness from changing suddenly in the lightness range equal to or lower than the threshold value, and to suppress the occurrence of tone jump.

As a color space for performing this conversion, it is preferable to employ a color space including lightness as a color component. That is, since the conversion target in this conversion is lightness, conversion can be performed very easily if the color space includes lightness as a color component. Examples of color spaces that include lightness in color conversion include device-independent color spaces such as the L ^* a ^* b ^* color space and the L ^* u ^* v ^* color space. In addition, since it is possible to calculate a value corresponding to lightness in a color space that does not include lightness, for example, an RGB color space, it is possible to adjust a value corresponding to lightness by changing each component of RGB. It is. However, since the brightness is not directly changed, it is difficult to ensure that the brightness changes smoothly. On the other hand, if the processing is performed in a color space that includes the lightness in the color component, the lightness is directly changed, so that it is possible to ensure that the lightness change becomes smooth.

  As a specific example for smoothly changing the brightness below the threshold in the color conversion means, as an index for smoothly changing the brightness in the brightness area below the threshold, a plurality of brightness in the brightness area below the threshold An output value may be set, and the input lightness may be converted into the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses. That is, a plurality of points are designated in advance as indices for smoothly changing, and a smooth input / output curve is generated based on the indices. That is, the amount of data prepared in advance can be reduced while realizing the intended smoothness.

  Further, as a configuration example for making it possible to flexibly cope with the background color and show-through of input data based on various document types, the color conversion unit is provided with a threshold receiving unit that receives the change of the threshold, and is equal to or less than the threshold A lower limit is set for a range in which the lightness is smoothly changed in the lightness region, and the lightness may be smoothly changed in the range below the threshold and above the lower limit. That is, the threshold value change based on the user's appropriate judgment is accepted to increase the removal level of the background color and the show-off, and the removal does not affect the high density region (low brightness region) with the change of the removal level. In addition, a lower limit is set in a range in which the lightness can be converted by the color conversion means. Accordingly, it is possible to prevent the influence on the dark part such as the quality of black characters. The lower limit may be set according to the document type of the input image data.

  Furthermore, as an example of a more specific configuration in which the lower limit value is provided, the color conversion unit may use a plurality of brightness values in the brightness range below the threshold as an index for smoothly changing the brightness in the brightness range below the threshold. When an output value is set for the input value, the input lightness is converted into an output lightness based on a smooth input / output curve formed based on the plurality of lightness values, and the threshold value accepting unit accepts the change of the threshold value. When the plurality of brightness values are changed and the plurality of brightness values are shifted to the lower limit or less due to the change, a correction that sets a minimum value to the lower limit for the plurality of brightness values and an interval ratio of the plurality of brightness values It is good also as a structure which performs correction | amendment which keeps constant. That is, in order to realize the smooth conversion, output values are set for a plurality of brightness values, and input brightness values are converted into output brightness values based on these brightness values. If any of the plurality of brightness values is equal to or lower than the lower limit value, the ratio is changed so that the ratio of the plurality of brightness intervals is maintained before and after the change of the threshold value. Therefore, it is possible to prevent the influence on the dark part and keep smooth conversion.

  For the threshold value and the plurality of brightness values, color conversion may be performed so as to have different brightness changes in accordance with the creation conditions when creating the input image data. It is possible to target colors in different regions in the color space.

The above-described image processing apparatus includes various modes such as being implemented in a state where it is incorporated in another device or being implemented together with another method. The present invention also provides an image processing system and a copying apparatus provided with the image processing apparatus, a control method having steps corresponding to the configuration of the apparatus described above, a program for causing a computer to implement functions corresponding to the configuration of the apparatus described above, and the program It can also be realized as a computer-readable recording medium on which is recorded. The inventions of the image processing system, the copying apparatus, the image processing method, the image processing program, and the medium on which the program is recorded also have the above-described operations and effects. Needless to say, the configuration described in claim 2 is also applicable to the system, the method, the program, and the recording medium.

Hereinafter, embodiments of the present invention will be described in the following order.
(1) Configuration of copying machine:
(2) Copy processing:
(2-1) Profile creation processing:
(3) Other embodiments:
(4) Summary:

(1) Configuration of copying machine:
FIG. 1 is a perspective view showing an outer shape of a copying apparatus as an embodiment of an image processing apparatus according to the present invention. As shown in FIG. 1, a copying apparatus 10 according to an embodiment of the present invention includes a scanner unit 20, a printer unit 40, and an operation unit 30 connected thereto. FIG. 2 is a block diagram illustrating a hardware configuration of the copying apparatus. As shown in the figure, the copying apparatus 10 includes a CPU 11, a RAM 12, a ROM 13, a data holding unit 14, a scanner unit 20, a printer unit 40, and an operation unit 30. The CPU 11 executes various control programs stored in the ROM 13 while using the RAM 12 as a work memory. The data holding unit 14 is configured by storage means such as a hard disk or an EEPROM.

  The scanner unit 20 is a device that conveys a document set in an ADF (Auto Document Feeder) to a document reading unit and reads an image on the document. At this time, the read image is expressed by input image data. In the present embodiment, an image is constituted by a plurality of pixels, and each color density of RGB (red, green, blue) is expressed by gradation for each pixel. . The scanner unit 20 realizes a reading operation by a control program executed by the CPU 11.

  More specifically, the reading unit 20b includes a light source (such as an LED) that irradiates light on the document, a sensor (such as a CCD) that detects reflected light, and a document transport mechanism, and the CPU 11 reads the reading control unit 20a. The reading unit 20b is controlled via As a result, the document is transported and the contents recorded on the document are converted into digital data. That is, input image data for each RGB is generated.

The data holding unit 14 records a scanner profile for converting input image data obtained as a result of reading by the scanner unit 20 into coordinate values of the L * a ^* b ^* color system. A scanner profile is created in advance for each type of document to be read by the scanner unit 20, and is stored for each type of document. The data holding unit 14 may be a mask ROM or a rewritable memory such as an EEPROM as long as it can hold data indicating a profile.

  The operation unit 30 presents copy conditions and the like to the user, takes charge of processing for accepting an operation from the user, and creates a correction profile for performing color conversion according to the present invention. For this purpose, a display unit 30b (such as an LCD) that provides information to the user such as the document type and the size of the printing paper and an operation input unit 30a (such as a push button and a touch panel) for inputting user-desired information are provided. Yes. In addition to controlling the display unit 30b and the operation input unit 30a, the CPU 11 performs a process of creating a correction profile with reference to the scanner profile and printer profile held in the data holding unit 14.

  That is, the data holding unit 14 holds data indicating a threshold value for each type of document and lightness data indicating a change in lightness in advance, and the CPU 11 refers to these data and from the data holding unit 14 the scanner profile and the like. A printer profile is acquired, and a correction profile is created based on these data. The created correction profile is recorded in the data holding unit 14. Details of processing for creating a correction profile will be described later.

  In the present embodiment, the CPU 11 also performs a process of performing color conversion with reference to the correction profile. That is, input image data is acquired from the scanner unit 20, color conversion is performed on the input image data with reference to the correction profile, and output image data is acquired. Then, the output image data is output to the printer unit 40. As a result, it is possible to obtain a printing result reflecting the color conversion by the correction profile.

  The output image data is data in which an image is constituted by a plurality of pixels and each color density of RGB (red, green, blue) is expressed by gradation for each pixel. However, the input image data expresses colors in the RGB color system of the scanner, and the output image data expresses colors in the RGB color system of the printer. Even if the color component values of the two match, The colors corresponding to the color component values do not always match. That is, the color specified in both color systems is a device-dependent color. Therefore, the configuration is such that color conversion of both RGB color systems can be performed by the correction profile. The correction profile only needs to be configured to perform color conversion in both RGB color systems, and may be a color conversion table or data indicating a function.

  The predetermined image processing is performed by the image processing unit 50 (custom IC or the like), and the process of recording the recording material on the printing paper is performed by the print control unit 40a and the print engine 40b. That is, the CPU 11 performs a data transfer process based on an instruction from the operation unit 30 and appropriately performs image processing. When the output image data output by the operation unit 30 is acquired, the output image is obtained. The image processing unit 50 is made to process the data. The image processing unit 50 is an IC that performs color conversion and halftone processing with reference to a profile, and generates halftone data specifying a recording material amount for outputting the color indicated by the output image data.

  The color of the recording material is not particularly limited, but for example, CMYK (cyan, magenta, yellow, black) can be used. In this case, the image processing unit 50 performs color conversion on the output image data of the RGB color system, generates a gradation value corresponding to the recording material usage amount for each color of CMYK, and reduces the number of gradations of the gradation value. To generate halftone data.

  The print engine 40b includes a photoconductor unit, an exposure unit developing unit, a printing paper transport unit, and the like (not shown). The toner is transferred to the photoconductor according to the halftone data, and further, the toner is transferred to the printing paper and fixed. To execute printing. The print engine 40b is controlled by a print control unit 40a, and the print control unit 40a receives the halftone data and controls each unit to record a recording material according to the halftone data.

The color conversion process by the image processing unit 50 is performed with reference to the profile held in the data holding unit 14. A plurality of types of profiles corresponding to printing conditions are recorded in the data holding unit 14 as printing profiles. In addition, for each printing condition, a printer profile that associates the coordinate values of the output image data (RGB values) and the L ^* a ^* b ^* color system, the color of the output image data and the recording material (toner) A toner conversion profile in which color space coordinate values as color components are associated is recorded. The image processing unit 50 refers to the toner conversion profile and acquires coordinate values of a color space in which the color of the recording material is a color component. As a result of this color conversion, the usage amount of the recording material for forming an image with the color indicated by the output image data is specified.

(2) Copy processing:
In the present embodiment, copying is performed by the processing of the CPU 11. FIG. 3 is a general flowchart of the copying process. At the time of copying, the CPU 11 performs processing according to the flowchart shown in FIG. 3 and sets copy conditions (step S100). That is, a selection screen for selecting a reading condition and a printing condition at the time of copying is displayed on the display unit 30b of the operation unit 30, and the user reads through the operation input unit 30a while viewing the selection screen. Set the conditions and printing conditions.

  Various conditions can be adopted as the reading conditions. For example, the type of the original to be read, the original size, the background color and the level at which the show-through is removed (hereinafter referred to as background removal) are set. Various conditions can be adopted as the printing conditions. For example, the printing paper size and the color at the time of printing (monochrome, color designation) are set. When the copying conditions are set, the CPU 11 outputs instruction data for instructing the scanner unit 20 to start reading. When the scanner unit 20 acquires the instruction data, the CPU 11 issues an instruction to the reading control unit 20a. Then, the document placed on the ADF is conveyed under the control of the reading control unit 20a, and input image data indicating an image on the document is acquired (step S110). The acquired input image data is output to the operation unit 30.

  In the present embodiment, the background color and the show-through that can be included in the input image data are removed, and the tone jump is prevented from occurring due to the removal (hereinafter referred to as tone jump prevention). Conversion is performed, and the correction profile is created in order to perform this color conversion (step S120). The created correction profile is held in the data holding unit 14 as described above, and the CPU 11 refers to the correction profile and performs color conversion processing on the input image data acquired in step S110 (step S130). ).

  When the output image data is created by this color conversion processing, the CPU 11 outputs the output image data to the printer unit 40, and the printer unit 40 performs printing based on the output image data (step S140). That is, the CPU 11 controls the printer unit 40 so as to execute printing according to the printing conditions. For example, the CPU 11 issues an instruction to the print control unit 40a, pulls out the printing paper from the cassette in which the designated printing paper is accumulated, and conveys it.

  Further, the CPU 11 instructs the image processing unit 50 on the number of colors (monochrome or color). The image processing unit 50 performs color conversion with reference to the toner conversion profile for executing printing with the specified number of colors. Further, the image processing unit 50 performs halftone processing, and the print control unit 40a controls the print engine 40b based on the data after the halftone processing. As a result, an image is recorded on the printing paper in a state where the conversion by the correction profile is reflected.

(2-1) Profile creation processing:
In the present embodiment, in creating the correction profile, a correction profile is created that performs conversion so that the brightness changes smoothly with background removal. By performing the color conversion process with reference to the correction profile created in this way, the background is removed and tone jump does not occur due to this removal. The correction profile creation process will be described in detail below.

FIG. 4 is a flowchart in an embodiment of a process for creating a correction profile. When the process is started, in step S200, the CPU 11 acquires information indicating the document type set in step S100, and acquires a scanner profile corresponding to the document type. The CPU 11 temporarily stores data indicating the scanner profile in the RAM 12. The scanner profile defines a correspondence relationship between L ^* a ^* b ^* values and RGB values in the scanner.

In subsequent step S205, the CPU 11 acquires information indicating the printing conditions set in step S110, and acquires a printer profile corresponding to the printing conditions. The CPU 11 temporarily stores data indicating the printer profile in the RAM 12. The printer profile defines the correspondence between L ^* a ^* b ^* values and RGB values in the printer.

For L ^* a ^* b ^* values corresponding to RGB values defined in the scanner profile, if the RGB values corresponding to the same L ^* a ^* b ^* values are calculated from the printer profile, the scanner's color matching will be performed. The RGB value and the RGB value of the printer can be associated with each other. When this association is performed, the L ^* a ^* b ^* value corresponding to the RGB value defined in the scanner profile is converted to another value, and the RGB value corresponding to the converted L ^* a ^* b ^* value Is calculated from the printer profile, the RGB value of the scanner can be associated with the RGB value of the printer in a state where the color read by the scanner unit 20 is converted into a desired color.

Therefore, in the present embodiment, color matching is performed in the L ^* a ^* b ^* space so that the brightness is changed smoothly along with the ground color / show-through removal, and the color correspondence relationship using the threshold value and the brightness data. Perform the conversion. By performing the input / output conversion in the L ^* a ^* b ^* color space as in this embodiment, it is very easy to maintain the hue and saturation before and after the conversion. Although it is possible to change the brightness in a color system that does not include brightness, such as the RGB color system, it is very difficult to change only the brightness. However, in the L ^* a ^* b ^* space, it is possible to perform conversion while maintaining the color. Since the human eye is most sensitive to lightness changes among lightness, saturation, and hue, the smooth change in lightness suppresses the impression that a tone jump has occurred very effectively. be able to.

  In the subsequent step S210, the CPU 11 acquires the threshold value and brightness data corresponding to the document type from the data holding unit 14, and acquires the background removal level set in step S100. The threshold value and brightness data (coordinate values) are recorded in the data holding unit 14 for each document type. Therefore, even if the background color differs for each document type and the degree of show-through varies, the background is appropriately removed according to each document type, and the brightness is smoothly changed according to each document type. be able to. The role of threshold value, brightness data, and background removal level will be described in detail below.

Threshold, L ^* a ^* b ^* space indicates the range for removing the background color and show-through at, L ^* a ^* b ^* coordinates of the color space _{^{(L * T, a * T}} , b * T ) Specifies the color to be removed from the base color and show-through. That is, for a color having a lightness equal to or higher than the threshold value L ^* _T, the lightness is uniformly converted to the maximum value (for example, the gradation value 100 in the gradation value range 0 to 100). This threshold value L ^* _T corresponds to a predetermined threshold value in the above claims.

When the lightness of the specific gradation range is converted in this way, a tone jump occurs between colors outside the specific gradation range. In this embodiment, in order to smoothly change the brightness before and after the threshold L ^* _T, specifies how the brightness change of the low-brightness side by brightness data than the threshold L ^* _T. The brightness data is composed of a plurality of points, and will be described with reference to FIG.

FIG. 5 is an explanatory diagram illustrating input / output conversion in the present embodiment. That is, the state of lightness change is specified by the coordinate value (the lightness data described above) on the two-dimensional graph indicating input / output conversion. In the figure, the horizontal axis corresponds to the input value, and the vertical axis corresponds to the output value. In this embodiment, the L ^* value (L ^* _s ) in the scanner profile is an input value, and the L ^* value (L ^* _p ) in the printer profile is an output value. In the present embodiment, five coordinate values indicating a change in brightness are prepared in advance. Hereinafter, these five coordinate values will be expressed as (L ^* _s [i], L ^* _p [i]) (i = 0, 1, 2, 3, 4).

In FIG. 5, each coordinate value is indicated by a black circle, and is defined such that L ^* _s [i] increases as i increases in order from i = 0 to i = 4. In this embodiment, each coordinate value corresponds to a control point of a Bezier curve, and (L ^* _s [0], L ^* _p [0]) is the start point of the Bezier curve, and (L ^* _s [4], L ^* _p [4]) is the end point of the Bezier curve.

In the present embodiment, the maximum L ^* _s [4] of the five coordinate values is matched with the threshold L ^* _T. Therefore, a smooth Bezier curve can be defined based on the black circle and smoothly connected to the threshold L ^* _T. Therefore, even if an image in which the color in the vicinity of the threshold L ^* _T changes smoothly is included, the lightness does not change abruptly, so that the occurrence of tone jump can be suppressed.

The background removal level is set by the user in accordance with the state of the read document and the reading trial result. The threshold value is changed in accordance with the background removal level, and the brightness data is corrected if necessary in accordance with the change of the threshold value. The correspondence relationship between the background removal level, the threshold value, and the brightness data is, for example, as shown in FIG. That is, when the background removal level is increased, the threshold value L ^* _T is lowered, and it becomes possible to remove even higher density background and show-through. However, as the threshold value L ^* _T decreases, the brightness data L ^* _s [4] set to the same brightness as the threshold value L ^* _T decreases, and the other brightness data also decreases.

At this time, if the intervals of the lightness data L ^* _s [0] to L ^* _s [4] are maintained, the Bezier curve for tone jump prevention has a low lightness as in the case of the background removal levels 4 and 5 in FIG. There is a possibility of shifting to the area and degrading the quality of black characters. Therefore, the lower limit L ^* _min is set so that the Bezier curve does not shift below a certain brightness. Note that the gradation range that affects the quality of black characters when the gradation value is changed varies depending on the nature of the printing paper and ink and the type of document, so the lower limit L ^* _min is the document type, printing conditions, It is set for each type of printing press.

FIG. 7 is a graph for explaining a state in which L ^* _s [0] of brightness data falls below the lower limit L ^* _min due to an increase in the background removal level when the brightness data lower limit L ^* _min is not set. . As shown in the figure, before the background removal level is strengthened, all brightness data is on the higher brightness side than the lower limit L ^* _min , but when the background removal level is strengthened, the interval of each brightness data is maintained. As a result, the entire brightness data may shift to the low gradation side, and L ^* _s [0] may fall below L ^* _min as shown in the lower diagram of FIG. Therefore, the brightness data is adjusted so as not to affect the quality of black characters.

FIG. 8 is a diagram for explaining how to adjust the brightness data. In the figure, L ^* _s [0] to L ^* _s [2] and the lower limit L ^* _min , which are objects of brightness data adjustment in this embodiment, are plotted on the input brightness axis. In this embodiment, among the five brightness data, three low-lightness intervals are targeted for adjustment. Of course, this is an example, and the input / output tone curve is smoothly changed. If there is, other brightness data may be adjusted.

As shown in FIG. 8, the brightness data adjustment is performed so that the ratio of the brightness data intervals to be adjusted is maintained before and after the brightness data adjustment. In the figure, the interval on the input brightness axis between L ^* _s [0] and L ^* _s [1] is ΔL ^* _1, and the interval on the input brightness axis between L ^* _s [1] and L ^* _s [2] Is ΔL ^* ₂ . When the background removal level increases, L ^* _s [0] <L ^* _min , and when L ^* _s [0] = L ^* _min is corrected, L ^* _s [1] becomes L ^* _s [1] ' L ^* _s [2] is corrected to L ^* _s [2] '. Let L ^* _s [0] 'and L ^* _s [1]' on the input brightness axis be ΔL ^* ₁ ', and L ^* _s [1]' and L ^* _s [2] 'on the input brightness axis. Let the interval be ΔL ^* ₂ ′. At this time, if ΔL ^* ₁ : ΔL ^* ₂ = a: b, the interval of the brightness data is adjusted so that ΔL ^* ₁ ′: ΔL ^* ₂ ′ = a: b. In FIG. 8, only the input brightness is described, but the same interval adjustment is executed for the output brightness.

  That is, in step S212, the threshold acquired in step S210 is changed according to the background removal level acquired in step S100, and the brightness data is changed in accordance with the change in the threshold. In this step, the process of correcting the ratio of the brightness data intervals executed in S235 and S240 described later may be executed in advance.

In the flowchart shown in FIG. 4, the process proceeds by sequentially converting L ^* _s values defined in the scanner profile. For this reason, first, the counter n is initialized to 0 (step S215). That is, among a plurality of colors defined in the scanner profile, the colors are distinguished by the counter n (L ^* _sn , a ^* _sn , b ^* _sn ), and processing is performed for each color. After the color is assigned with a sign to define the distinction of each color, it is determined whether or not the threshold L ^* _T is smaller than 100 (step S220).

When it is determined in step S220 that the threshold value L ^* _T is 100 or more, since it is not necessary to perform the input / output conversion according to the present invention for the lightness L ^* _sn , it is set so that the lightness conversion is not performed. That is, substituting the L ^* _sn variable L ₀ (step S275). In this case, the RGB value of the printer corresponding to L ^* _sn is calculated without _performing input / output conversion in the subsequent processing.

If it is determined in step S225 that the threshold value L ^* _T is smaller than 100, whether or not the lightness L ^* _sn exists between the start point L ^* _s [0] and the end point L ^* _s [4] in the above coordinate values. (Step S225). If it is not determined in step S225 that the lightness L ^* _sn exists between the start point and the end point, steps S265 to S267 are performed because it is not necessary to perform input / output conversion according to the present invention on the lightness L ^* _sn .

That is, it is determined whether or not the lightness L ^* _sn is greater than the threshold value L ^* _T (step S265). If it is determined in step S265 that the lightness L ^* _sn is greater than the threshold value L ^* _T , input / output conversion is performed. The maximum value (100) is substituted into the variable L ₀ for substituting the output value (step S270). In this case, the brightness is converted to the maximum value in the subsequent processing. If it is not determined in step S265 that the lightness L ^* _sn is greater than the threshold value L ^* _T , step S275 is performed.

When it is determined in step S230 that the lightness L ^* _sn exists between the start point and the end point, it is determined whether the start point L ^* _s [0] is larger than L ^* _min (S230). If it is determined in step S230 that the start point L ^* _s [0] is larger than L ^* _min , the process proceeds to step S245. On the other hand, when it is determined that the starting point L ^* _s [0] is equal to or less than L ^* _min , L ^* _s [0] is corrected to L ^* _min as shown in FIGS. 7 and 8 (step S235), and L The interval between ^* _s [0], L ^* _s [1] and L ^* _s [2] is adjusted and the process proceeds to step S245 (S240).

In step S245, a Bezier curve passing through the coordinate values (L ^* _s [i], L ^* _p [i]) is created. Here, the input / output relationship only needs to be defined by a curve smoothly connecting the coordinate values, and the input / output relationship can be defined by various algorithms for calculating a Bezier curve. After creating the Bezier curve, it converts the lightness L ^* _sn color to be processed based on the Bezier curve lightness L ^* _p n, substituting lightness L ^* _p n after conversion into the variable L ₀ (Step S250).

If the a ^* value and b ^* value are maintained by the conversion in steps S250 and S270, if the color becomes out of the color gamut of the printer unit 40, the a ^* value or b is specified so that the color in the color gamut is designated. ^It is preferable to convert ^* . Therefore, it is determined whether or not L ₀ = 100 (step S252). If L ₀ = 100, the color gamut is not widened in the normal saturation direction, so a ^* = b ^* = 0. (Step S253). If L ₀ = 100 is not satisfied, the process proceeds to step S255 without changing the saturation.

After performing steps S275 and S253, the scanner profile corresponding to the lightness L ^* _sn is calculated with reference to the scanner profile. Further, the printer RGB value of the printer corresponding to the coordinate values (L ₀ , a ^* _sn , b ^* _sn ) is calculated with reference to the printer profile. Then, a part of the data constituting the correction profile is created by associating both RGB values and recorded in the data holding unit 14 (step S255).

  When the above processing is completed, it is determined whether the counter n has reached the upper limit value (the number of colors defined in the scanner profile), thereby determining whether processing has been completed for all data to be processed. Is determined (step S260). If it is not determined in step S260 that all the processes have been completed, the counter n is incremented (step S280), and the processes in and after step S225 are repeated. If it is determined in step S260 that all the processes have been completed, the process in step S255 has been completed for all colors to be defined as profiles, and the creation / recording of the correction profile is completed.

(3) Other embodiments:
The embodiment described above is an example for realizing the present invention, and various other configurations can be adopted. For example, in the above embodiment, the control unit (the CPU 12, the CPU 13, and the data holding unit 14) is collectively described by the scanner unit 20, the operation unit 30, and the printer unit 40. Of course, each unit includes a control unit. Thus, calibration may be performed in which each control unit performs communication and performs linked processing. In addition to the configuration in which the CPU creates a correction profile according to a predetermined program, the control unit may be implemented by a custom IC chip that implements the present invention.

  Further, in the above-described embodiment, the present invention is realized by the copying apparatus 10 in which the scanner unit 20 and the printer unit 40 are integrated. However, the copying process is performed by connecting the scanner and the printer to a general-purpose computer. In the configuration in which the correction profile is implemented, the correction profile may be created by the general-purpose computer, the scanner, or the printer. Of course, the number of colors of the recording material used in the printer unit 40 is not limited to four, and the printer may be an inkjet printer.

  Furthermore, the coordinate values for smoothly changing the brightness as described above are not limited to five, and may be, for example, a Bezier curve in which a start point and an end point are specified. Further, the algorithm for forming the curve is not limited to the Bezier curve, and various other curves can be employed.

  Further, a configuration for creating a correction profile for each copying process as in the above-described embodiment is not essential, and a correction profile may be created in advance and stored in a memory. Further, instead of creating a correction profile, it is possible to obtain input image data and perform output equivalent to the conversion shown in FIG. 4 to generate output image data. Of course, as the correction profile, in addition to the profile that associates the RGB value of the scanner with the RGB value of the printer, a profile indicating the above input / output conversion is created, and this profile, the scanner profile, and the printer profile are referred to during copying. The conversion may be performed.

(4) Summary:
As described above, in the present embodiment, input image data designating the colors of a plurality of pixels is input from the scanner unit 20, and the input image data is converted to output image data indicating the output color in the printer unit 40. , The color whose lightness exceeds the predetermined threshold L ^* _T is converted to L = 100, and the lightness is smoothly changed in the lightness range below the threshold L ^* _T. When a color having L = 100 is a color in a predetermined saturation region and a predetermined hue angle region of L ^* a ^* b ^* space, the saturation of the color is converted to 0, so that It is possible to prevent the occurrence of tone jumps not only in the brightness direction but also in the saturation direction and the hue direction while removing the reflection and the like.

  Note that the present invention is not limited to the above-described embodiments and modifications, and the structures disclosed in the above-described embodiments and modifications are mutually replaced, the combinations are changed, the known technique, and the above-described implementations. Configurations in which the configurations disclosed in the embodiments and modifications are mutually replaced or the combinations are changed are also included.

1 is a diagram illustrating a copying apparatus. 1 is a block configuration diagram of a copying apparatus. It is a general flowchart of a copying process. It is a flowchart of a correction profile creation process. It is explanatory drawing explaining input-output conversion. It is a table | surface which shows the correspondence of a background removal level, a threshold value, and brightness data. It is the graph which showed the brightness data which change with a raise of a background removal level. It is a figure explaining how to adjust brightness data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Copy apparatus, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... Data holding part, 20 ... Scanner part, 20a ... Reading control part, 20b ... Reading part, 30 ... Operation part, 30a ... Operation input part, 30b ... display unit, 40 ... printer unit, 40a ... print control unit, 40b ... print engine, 50 ... image processing unit

Claims (7)

Image data input means for inputting input image data designating the colors of a plurality of pixels;
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. Color conversion means for converting the saturation of the color to 0 when the color having the highest brightness with respect to the color after conversion is a color within a specific region in the color space, Prepared ,
The color conversion means includes
A threshold receiving means for receiving a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the threshold value accepting unit accepts the change of the threshold value, the plurality of brightness values are changed accordingly, and when the plurality of brightness values are shifted to the lower limit or less due to the change, the plurality of brightness values are changed. An image processing apparatus , wherein correction for setting a minimum value to the lower limit and correction for maintaining a constant interval ratio of the plurality of brightness values are performed . The color conversion unit, when creating conditions for generating the input image data is different, the color of the different areas in the color space as a target in claim 1 for performing the color conversion so that different brightness change The image processing apparatus described. An image data input step of inputting input image data designating the colors of a plurality of pixels;
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. A color conversion step of converting the saturation of the color to 0 when the color having the highest brightness with respect to the color after conversion is a color within a specific region in the color space, Prepared ,
The color conversion step includes
A threshold acceptance step for accepting a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the change of the threshold is accepted in the threshold acceptance step, the plurality of brightnesses are changed accordingly, and when the plurality of brightnesses are shifted to the lower limit or less by the change, the plurality of brightnesses are changed. An image processing method comprising: performing a correction for setting a minimum value to the lower limit and a correction for maintaining a constant interval ratio of the plurality of brightness values . An image processing program,
An image data input function for inputting input image data specifying colors of a plurality of pixels,
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. A color conversion function for converting the saturation of the color to 0 when the color having the highest brightness for the converted color is a color within a specific region in the color space, to realize the computer,
The color conversion function is
A threshold acceptance function for accepting a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the change of the threshold value is received by the threshold value reception function, the plurality of brightness values are changed accordingly, and when the plurality of brightness values are shifted to the lower limit or less by the change, the plurality of brightness values are changed. An image processing program characterized by performing correction for setting a minimum value to the lower limit and correction for maintaining a constant interval ratio of the plurality of brightness values . A document reading means for reading the document and inputting input image data specifying the color of the image for a plurality of pixels;
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. Color conversion means for converting the saturation of the color to 0 when the color having the highest brightness with respect to the color after the conversion is a color within a specific region in the color space;
Printing control means for causing the printing apparatus to execute printing based on the output image data ,
The color conversion means includes
A threshold receiving means for receiving a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the threshold value accepting unit accepts the change of the threshold value, the plurality of brightness values are changed accordingly, and when the plurality of brightness values are shifted to the lower limit or less due to the change, the plurality of brightness values are changed. A copying apparatus , wherein a correction for setting a minimum value to the lower limit and a correction for maintaining a constant interval ratio of the plurality of brightness values are performed . A document reading step of reading the document and inputting input image data specifying the color of the image for a plurality of pixels;
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. A color conversion step of converting the saturation of the color to 0 when the color having the highest brightness with respect to the converted color is a color within a specific region in the color space;
A printing control step for causing the printing apparatus to execute printing based on the output image data ,
The color conversion step includes
A threshold acceptance step for accepting a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the change of the threshold is accepted in the threshold acceptance step, the plurality of brightnesses are changed accordingly, and when the plurality of brightnesses are shifted to the lower limit or less by the change, the plurality of brightnesses are changed. A copying method comprising: performing a correction for setting a minimum value to the lower limit and a correction for maintaining a constant interval ratio of the plurality of brightness values . A copying program,
An original reading function for reading an original and inputting input image data in which the color of the image is designated for a plurality of pixels;
In obtaining the output image data indicating the output color in the output device by converting the input image data, the color whose brightness exceeds a predetermined threshold is converted to the maximum brightness, and the brightness is smooth in the brightness range below the threshold. A color conversion function for converting the saturation of the color to 0 when the color having the highest brightness with respect to the converted color is a color within a specific region in the color space;
Causing a computer to implement a print control function that causes a printing apparatus to execute printing based on the output image data ,
The color conversion function is
A threshold acceptance function for accepting a change in the threshold;
A lower limit is set for the range in which the brightness is smoothly changed in the brightness area below the threshold value, and a plurality of brightness values in the brightness area below the threshold value are set as indices for smoothly changing the brightness in the brightness area below the threshold value. By setting an output value for the lightness, and converting the input lightness to the output lightness based on a smooth input / output curve formed based on the plurality of lightnesses, the lightness is within the range below the threshold and above the lower limit. Convert to change smoothly,
When the change of the threshold value is received by the threshold value reception function, the plurality of brightness values are changed accordingly, and when the plurality of brightness values are shifted to the lower limit or less by the change, the plurality of brightness values are changed. A copying program , wherein a correction for setting a minimum value to the lower limit and a correction for maintaining a constant interval ratio of the plurality of brightness values are performed .

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