JP4023491B2 - Image processing apparatus, image processing program, and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing program, and an image processing method capable of performing adjustment in harmony with other colors when adjusting a specific color of a color image.

  In recent years, the performance of digital cameras and video cameras has been improved, and it has been widely used since it has been supplied at low cost. Images taken by these cameras are output to a color printer (for example, an ink jet printer) and printed, or displayed on a color image display device such as an LCD.

  The colors displayed by these display devices include, for example, memory colors that are stored as human images such as skin color, and such colors are imaged by humans rather than colors that are faithful to the subject. It is required to adjust the colors so that they are close to each other.

Japanese Patent Application Laid-Open No. 2-96477 discloses a color adjustment apparatus that can locally perform color adjustment on an area in which a memory color such as a skin color area is desired to be reproduced.
Japanese Patent Laid-Open No. 2-96477

  However, the above-mentioned Patent Document 1 does not consider the lightness when specifying the skin color area, so adjustment of the bright and dark parts of the skin color, and the skin color and the skin color adjacent to the skin color area are different. There was a problem that the color adjustment near the part and the boundary became unnatural. In particular, when processing an image obtained by photographing a human face, there is a tendency that it is difficult to adjust the boundary between the eyebrows and the dark part of the portion continuous with the neck to a natural color.

  The present invention has been made to solve the above-described problems, and an image processing apparatus, an image processing program, and an image that can adjust the color adjustment of a specific color and a portion adjacent to the specific color to natural colors. It aims to provide a processing method.

In order to achieve this object, an image processing apparatus according to claim 1 of the present invention includes an input means for inputting a value of a combination of a plurality of basic colors included in color image information, and image information input to the input means. Is converted to lightness, hue, saturation values, adjustment means for adjusting the brightness, hue, saturation values converted by the conversion means, and the brightness, hue adjusted by the adjustment means Correction means for correcting a color image based on a saturation value, and for each value of hue and saturation, a weighting factor for a value indicating a specific color is set to a first predetermined value. And storing a weighting factor for a value in a predetermined range continuous with a value indicating a specific color as a weighting factor curve having a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum. About brightness value The weight coefficient for the value indicating the specific color is set to a first predetermined value, and the weight coefficient for a value in a predetermined range continuous to the value indicating the specific color is monotonously decreased with the first predetermined value being maximized or A weight coefficient curve storage means for storing as a weight coefficient curve having a value determined by a monotonically increasing function and a weight coefficient when the lightness is a maximum value as a second predetermined value other than 0; A weighting factor acquisition unit that obtains a weighting factor corresponding to each value of brightness, hue, and saturation converted by the unit by referring to the weighting factor curve stored in the weighting factor curve storage unit, and the weighting factor acquisition unit Specific color index acquisition means for obtaining a specific color index by mutually multiplying each weighting coefficient acquired by the above, and a change amount setting means for setting a change amount of each value of brightness, hue, and saturation, The adjustment unit sets the adjustment amount by multiplying the change amount set by the change amount setting unit by the specific color index obtained by the specific color index acquisition unit, and based on the adjustment amount, brightness, hue, It adjusts each value of saturation.

According to a second aspect of the present invention, there is provided the image processing device according to the first aspect , wherein a weighting factor for a value in a predetermined range that is continuous with a value indicating a specific color in the weighting factor curve stored in the weighting factor curve storage unit is provided. The desired monotonically increasing or monotonically decreasing function is set to a sine function or a cosine function.

The image processing apparatus according to claim 3, wherein, in the image processing apparatus according to claim 1 or 2, wherein the specific color is one in which skin color is set.

According to a fourth aspect of the present invention, there is provided an image processing program that includes an input unit that inputs values of combinations of a plurality of basic colors included in color image information, and is executed in an image processing apparatus that processes a color image input to the input unit. An image processing program comprising: a conversion step for converting image information input to the input means into lightness, hue, and saturation values; and the brightness, hue, and saturation values converted by the conversion step. As for the corresponding weighting factor, for each value of hue and saturation, the weighting factor for the value indicating the specific color is set to the first predetermined value, and the weighting factor for the value in a predetermined range continuous to the value indicating the specific color Is stored as a weighting coefficient curve having a value obtained by a monotonically decreasing or monotonically increasing function maximizing the first predetermined value, and the brightness value is a value corresponding to a value indicating a specific color. The weighting factor is set to a first predetermined value, and the weighting factor for a value in a predetermined range continuous with a value indicating a specific color is obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum. And a weighting factor acquisition step to be obtained by referring to a weighting factor curve storage means for storing the weighting factor when the brightness is the maximum value as a weighting factor curve having a second predetermined value that is not 0, and , Specific color index acquisition step to obtain the specific color index by multiplying each weight coefficient determined by the weight coefficient acquisition step, and change amount setting to set the change amount of each value of lightness, hue, saturation a step, sets the adjustment amount by multiplying the specific color index determined by the specific color index acquiring step changes the amount set by the change amount setting step, the An adjustment step for adjusting each value of brightness, hue, and saturation based on the amount of adjustment, and a correction step for correcting a color image based on the values of brightness, hue, and saturation adjusted by the adjustment step Yes.

An image processing program according to a fifth aspect is the image processing program according to the fourth aspect , wherein the specific color is set to a skin color.

The image processing method according to claim 6, wherein an input step for inputting a combination value of a plurality of basic colors included in the color image information, and the image information input by the input step are set to three values of brightness, hue, and saturation. A color conversion based on the lightness, hue, and saturation values adjusted by the adjustment step, the lightness, hue, and saturation values converted by the conversion step. A correction step for correcting an image, and for each value of hue and saturation, a weighting factor for a value indicating a specific color is set to a first predetermined value and a value indicating a specific color A weighting coefficient curve for a continuous predetermined range of values is a weighting coefficient curve having a value determined by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum, and for a value of brightness, The weight coefficient for the value indicating the constant color is set to the first predetermined value, and the weight coefficient for the value in the predetermined range continuous to the value indicating the specific color is monotonously decreased or monotonically with the first predetermined value as a maximum. A weighting factor curve forming step for forming a weighting factor curve having a value obtained by an increasing function and a weighting factor when the lightness is a maximum value as a second predetermined value other than 0 ; and the conversion step A weighting factor acquisition step for obtaining a weighting factor corresponding to each value of lightness, hue, and saturation converted by the weighting factor curve by referring to the weighting factor curve forming step, and the weighting factor acquisition step. Specific color index acquisition step to obtain specific color index by multiplying each obtained weight coefficient mutually, and change amount to set the change amount of each value of lightness, hue, saturation And the adjustment step sets the adjustment amount by multiplying the change amount set by the change amount setting step by the specific color index obtained by the specific color index acquisition step, and the adjustment Each value of brightness, hue, and saturation is adjusted based on the amount.

The image processing method according to claim 7, wherein, in the image processing method according to claim 6, wherein the specific color is one that is set to the skin color.

According to the image processing apparatus of the first aspect, the weighting coefficient curve storage means sets the weighting coefficient for the value indicating the specific color as the first predetermined value and specifies the hue and saturation values. A weight coefficient for a predetermined range of values that are continuous with a value indicating a color is stored as a weight coefficient curve having a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum, and a lightness value For the value indicating the specific color, the weighting coefficient for the value indicating the specific color is set to the first predetermined value, and the weighting coefficient for the value in the predetermined range continuing to the value indicating the specific color is monotonically maximizing the first predetermined value. A value obtained by a function that decreases or monotonously increases, and is further stored as a weight coefficient curve in which the weight coefficient when the brightness is the maximum value is a second predetermined value that is not zero. Weight coefficient acquiring unit, converted brightness by converting means, hue, Ru determined by referring to the weighting coefficient curve stored in the weight coefficient curve storage means the weighting coefficients corresponding to each value of the color saturation. The specific color index acquisition means obtains the specific color index by multiplying each weight coefficient acquired by the weight coefficient acquisition means, and the change amount setting means determines the change amount of each value of brightness, hue, and saturation. Set . The adjustment unit sets the adjustment amount by multiplying the change amount set by the change amount setting unit by the specific color index obtained by the specific color index acquisition unit, and based on the adjustment amount, brightness, hue Adjust each value of saturation. In the weighting coefficient curve for lightness, when the value indicating lightness is the highest value, the weighting coefficient value is set to a value larger than 0. Therefore, the weighting coefficient is not 0 in the high lightness region. In addition, there is an effect that even when the specific color is bright, it is corrected well.
In addition, when adjusting the specific color of the input color image, the adjustment amount of the specific color specified by lightness, hue, and saturation can be greatly changed, and a color that is not a specific color adjacent to the specific color Abrupt color change can be suppressed at the boundary. As a result, it is necessary to perform adjustment again due to an excessive amount of adjustment, and it is possible to prevent repeated operations and to efficiently adjust natural color change.

According to the image processing apparatus according to claim 2, wherein, in addition to the effects of the image processing apparatus according to claim 1, wherein, in a predetermined continuous range of a value indicating a specific color in the weighting coefficient curves stored in the weighting coefficient curve storage means Since the monotonically increasing function or the monotonically decreasing function for obtaining the weighting coefficient for the value is a sine function or a cosine function, the area where the weighting coefficient is the first predetermined value and the area where the weighting coefficient is 0 change smoothly. There is an effect that a curve can be formed and the boundary between a specific color and a color that is not a specific color can be changed in a natural color tone.

According to the image processing apparatus of the third aspect , in addition to the effect produced by the image processing apparatus of the first or second aspect , the specific color is a skin color, so that it is one of the memory colors and has an image especially for humans. There is an effect that a strong color can be finely adjusted without unnaturalness.

According to the image processing program of claim 4, the weighting factor acquisition step calculates the weighting factor corresponding to each value of brightness, hue, and saturation converted by the conversion step, and for each value of hue and saturation, The weight coefficient for the value indicating the specific color is set to the first predetermined value, and the weight coefficient for the value in the predetermined range continuous to the value indicating the specific color is monotonically decreased or monotonically with the first predetermined value as a maximum. Stored as a weighting coefficient curve having a value obtained by an increasing function, and for the brightness value, the weighting coefficient for the value indicating the specific color is set to the first predetermined value and the value indicating the specific color is continuous. The weighting factor for the value in the predetermined range is a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as the maximum, and the weighting factor when the lightness is the maximum value is not zero. 2 Determined by referring to the weighting coefficient curve storage means for storing a weighting coefficient curve with a predetermined value. The specific color index acquisition step obtains the specific color index by multiplying each weight coefficient obtained in the weight coefficient acquisition step, and the change amount setting step includes the change amount of each value of lightness, hue, and saturation. Set. The adjustment step sets the adjustment amount by multiplying the change amount set in the change amount setting step by the specific color index obtained in the specific color index acquisition step, and based on the adjustment amount, brightness, hue, saturation Each value of is adjusted. In the weighting coefficient curve for lightness, when the value indicating lightness is the highest value, the weighting coefficient value is set to a value larger than 0. Therefore, the weighting coefficient is not 0 in the high lightness region. In addition, there is an effect that even when the specific color is bright, it is corrected well. In addition, when adjusting the specific color of the input color image, the adjustment amount of the specific color specified by lightness, hue, and saturation can be greatly changed, and a color that is not a specific color adjacent to the specific color Abrupt color change can be suppressed at the boundary. As a result, it is necessary to perform adjustment again due to an excessive amount of adjustment, and it is possible to prevent repeated operations and to efficiently adjust natural color change.

According to the image processing program of the fifth aspect , in addition to the effect produced by the image processing program of the fourth aspect , the specific color is a skin color, so that the color is one of the memory colors and particularly has a strong image for humans. There is an effect that fine adjustment can be performed without unnaturalness.

According to the image processing method of claim 6 , the weighting coefficient curve forming step sets the weighting coefficient for the value indicating the specific color as the first predetermined value and the specific color for each value of hue and saturation. A weighting coefficient curve for a value in a predetermined range continuous with a value indicating a weighting coefficient curve having a value obtained by a monotonically decreasing or monotonically increasing function maximizing the first predetermined value, The weight coefficient for the value indicating the specific color is set to the first predetermined value, and the weight coefficient for the value in the predetermined range continuous to the value indicating the specific color is monotonically decreased or monotonically with the first predetermined value as a maximum. A weight coefficient curve is formed with a value obtained by an increasing function and a second predetermined value that is not zero when the lightness is the maximum value . In the weighting factor acquisition step, the weighting factor corresponding to each value of brightness, hue, and saturation converted in the conversion step is obtained by referring to the weighting factor curve formed in the weighting factor curve forming step. The specific color index acquisition step obtains the specific color index by multiplying each weight coefficient acquired by the weight coefficient acquisition step, and the change amount setting means determines the change amount of each value of brightness, hue, and saturation. Set. The adjustment step sets the adjustment amount by multiplying the change amount set in the change amount setting step by the specific color index obtained in the specific color index acquisition step, and based on the adjustment amount, brightness, hue, saturation Adjust each degree value.

The weighting factor curve for the brightness stored in the weighting factor curve storage means is a region where the value of the weighting factor is set to a value greater than 0 when the value indicating the brightness is the highest value, so that the value is high. In this case, there is an effect that the weighting coefficient is not 0, and the correction is satisfactorily corrected even when the specific color is bright. In addition, when adjusting the specific color of the input color image, the adjustment amount of the specific color specified by lightness, hue, and saturation can be greatly changed, and a color that is not a specific color adjacent to the specific color Abrupt color change can be suppressed at the boundary. As a result, it is necessary to perform adjustment again due to an excessive amount of adjustment, and it is possible to prevent repeated operations and to efficiently adjust natural color change.

According to the image processing method according to claim 7, wherein, in addition to the effects of the image processing method according to claim 6, wherein the specific color, because it is skin color is one of the memory color, especially the color image is strong take humans There is an effect that fine adjustment can be performed without unnaturalness.

  A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of a printer 1 and a personal computer 20 (hereinafter referred to as a PC 20) connected to the printer 1. The printer 1 is configured to convert image information input from the PC 20 or image information recorded in an external medium 40 installed in the external media slot 6 provided in the printer 1 into print information and print it. Has been.

  The printer 1 includes a CPU 2, a RAM 3, a ROM 4, a USB interface 5, a USB connection terminal 7, an external media slot 6, an operation panel 30, and a printing unit 8, which are mutually connected via a bus 9. It is connected to the.

  The CPU 2 is a microprocessor that executes various programs stored in the ROM 4, and the RAM 3 is a memory having a work area that temporarily stores variables and the like when the CPU 2 executes the various programs. The ROM 4 is a read-only memory that stores various programs executed by the CPU 2 and constants and tables that are referred to when the programs are executed.

  The ROM 4 includes a specific color correction program 4a that is a control program, a weight coefficient curve 4b, a color conversion program 4c, a print control program 4d, and lookup tables LUT1-M (4e) and LUT2-M that are conversion tables. (4f) and the like are stored.

  The specific color correction program 4a obtains weighting coefficients for three parameters of lightness (L *), saturation (c *), and hue (h *), and a specific color index obtained from the weighting coefficients is set by a user or the like. This is a program that performs processing for correcting the respective values of the three parameters of lightness (L *), saturation (c *), and hue (h *) by multiplying the change amount.

  The weighting coefficient curve 4b is a curve showing weighting coefficients for three parameters of lightness (L *), saturation (c *), and hue (h *) that are referred to when the specific color correction program 4a is executed. is there. The weighting coefficient curve 4b may be a conversion table that stores a numerical value of a graph or may be an arithmetic expression.

  The color conversion program 4c is a program for converting values such as RGB, which are input color image information, so that the printer 1 can perform printing in an optimal state. The value is converted into CMYK values, which are print information, using an optimum lookup table or the like so as to match the type of sheet material to be printed and the printing resolution.

  The print control program 4d controls a carriage on which a print head of a printing unit is mounted, a driving device that drives a sheet material, and the like according to print information for performing printing converted by the color conversion program 4c.

  The lookup table LUT1-M (4e) is a conversion table that inputs values of combinations of three basic colors R (red), G (green), and B (blue) and performs ICCsRGB profile conversion. The table LUT2-M (4f) is a conversion table that inputs values of combinations of three basic colors (RGB) included in the image information and converts them into print information (CMYK) for printing. A plurality of lookup tables are stored in accordance with the ink used for printing, the type of sheet material to be printed, the printing resolution, and the like.

  The USB interface 5 communicates with the PC 20 through a USB cable connected to the USB terminal 7. Here, print information (CMYK) for printing from the PC 20 is input.

  The external media slot 6 can detachably mount an external medium 40 for storing image information (image data) taken by a digital camera or the like, and directly inputs image information (RGB) from the mounted external medium 40. To do.

  The printing unit 8 includes a carriage, a print head, ink tanks for each color of C (cyan), M (magenta), Y (yellow), and K (black). The carriage moves on a sheet material on which printing is performed, and the print head is mounted on the carriage and discharges ink supplied from each ink tank to a predetermined position of the sheet material. The operation panel 30 allows the user to make various settings of the printer 1 and will be described later with reference to FIG.

  The PC 20 includes a CPU 21, a ROM 22, a RAM 23, a hard disk 24 (HDD), a USB interface 25, and the like. The CPU 21 is a microprocessor that executes various programs stored in the ROM 22 and the hard disk 24. The RAM 23 is a memory having a work area that temporarily stores variables and the like when the CPU 2 executes various programs.

  The hard disk 24 is a non-volatile memory having a large storage capacity, and stores image data 24a photographed by a so-called OS or digital camera, a color conversion program 24b, and lookup tables 24c and 24d.

  The image data 24 a is input from the digital camera via the USB interface 25 and stored in the hard disk 24. The color conversion program 24a is one of so-called printer drivers, and refers to the lookup tables 24c and 24d from the RGB values constituting the image data 24a in order to print the image data 24a and the like. , A program for converting into CMYK values.

  The look-up tables 24c and 24d convert three-dimensional data represented by RGB values into four-dimensional CMYK data. The color conversion program 24b and the look-up tables 24c and 24d are set so as to perform processing corresponding to the printer 1 to be used, and are supplied from a CD-ROM attached to the printer 1. In the PC 20, these data are read by a CD-ROM drive (not shown) and stored in the hard disk 24. Note that these data may be provided via a communication interface (not shown) and received via a network such as the Internet.

  The USB interface 25 is an interface that communicates with an external device through a USB cable connected to the USB terminal 26. The USB interface 25 inputs image information captured by the digital camera, and outputs print information for printing to the printer 1. The image information captured by the scanner function of the printer 1 can be received.

  2A is a plan view of a portion of the operation panel of the printer 1, and FIG. 2B is a front view thereof. The printer 1 is a multifunction machine that can perform fax, copy, scan, and the like, and these functions are selected by a switch 33. When image information is received from the PC 20, printing is executed regardless of which function is selected.

  Various settings in each function are performed by operating the setting switch 31, and the dial button unit 32 is used when inputting a fax number of the other party when transmitting a FAX. The display unit 34 is composed of a liquid crystal, and can be selected by displaying a setting state or moving a cursor from functions displayed on the liquid crystal.

  The cursor key 35 is used when the cursor displayed on the display unit 34 is moved or when a selection is made from the displayed functions. When the user performs color adjustment of a specific color, the cursor key 35 is operated to display a screen for adjusting the specific color on the display unit 34, the specific color to be adjusted is selected, and the brightness (L *) , Saturation (c *), and hue (h *), the change amount is set for each of the three parameters, and an instruction is given to perform color adjustment.

  The stop button 37 is for instructing to stop when various functions are being executed, and the start button 38 is a button for instructing the start of execution of the function when performing faxing or copying. The flat bed 39 is a surface on which materials are arranged in order to read images of materials when copying, faxing, and scanning.

  On the front side of the printer 1, a discharge tray 50 for discharging the sheet material that has finished printing and an external media slot for mounting various external media are formed. In this figure, a CompactFlash (registered trademark) slot 41, a Memory Stick (registered trademark) slot 42, and a SmartMedia (registered trademark) slot 43 are provided.

  Next, the concept of the adjustment method when the specific color according to the present invention is a skin color will be described with reference to FIG. In the present invention, when adjusting a specific color, a weighting factor is obtained for each of the three parameters of lightness (L *), saturation (c *), and hue (h *) of the color indicating the specific color. The value obtained by multiplying the weight coefficients by each other is used as an index of a specific color, and the change amount is changed by multiplying the index by the change amount for changing each parameter set by the user.

  FIG. 3 shows that the weighting function is F, and the weighting coefficient is expressed with respect to the horizontal axis where each value is input for each of the three parameters of lightness (L *), saturation (c *), and hue (h *). It is a graph which shows the value of F on a vertical axis | shaft. FIG. 3A is a graph showing the weighting factor F (L *) for the lightness (L *), in which the horizontal axis represents the lightness (L *) and the vertical axis represents the weighting factor F (L *). is there. The lightness (L *) takes a value from 0 to 100, and the weight coefficient F (L *) takes a value from 0 to 1.

  As shown in this graph, the weighting factor F (L *) in the range indicated by lightness (L *) from 0 to A is 0, and the weighting factor F (L *) in the range indicated by B to C is 1. . The section indicated by A to B is connected by an S-shaped gentle monotone increasing curve, and the range beyond the position indicated by C is connected by an inverse S-shaped gentle monotonic decreasing curve. In the case of 100 which is the maximum value of lightness (L *), the weighting factor F (L *) is set to a predetermined value larger than zero.

  Therefore, when the brightness is high, the weighting factor F (L *) is set to a certain level, and a certain amount of change is performed according to the amount of change. In particular, when printing is performed, if the lightness is high, the amount of ink is small, and if the amount of change is small, the adjustment amount may be discarded. By setting the weighting factor F (L *) to a certain level, it is possible to correct well even when the brightness value is large.

  In this graph, the range from B to C (weighting factor F (L *) is 1) is the value of the lightness (L *) of the color representing the best skin color, and the lightness values outside this range are The lightness (L *) of a color that displays a color that is not a skin color is a value that is taken. In other words, the weighting factor F (L *) is set to 1 for the range of the lightness (L *) value of the color that best displays the skin color, which is the specific color, and the lightness (L *) outside that range is set. The value is set to 0 through a function that monotonously decreases or monotonically increases from a range where the weighting factor F (L *) is 1. The monotonically decreasing or monotonically increasing function is preferably an S-shaped or inverse S-shaped function that is a gentle change, as shown in FIG. A sine function or a cosine function can be used as the function indicating the S shape or the inverted S shape.

When using a sine function, if the weighting factor is Y and the constant is a,
Y = sin (aL *) / 2 + 0.5
Can be expressed as

  Note that the position indicated by A and the position indicated by B in FIG. 3A may be connected by a straight line, and in that case, the inclination of the straight line may be appropriately set. Further, as the S-shaped or inverse S-shaped function, a Gaussian function or a function using a third or higher order polynomial may be used. In addition, a lookup table formed by arbitrarily drawn curves may be used without using mathematical expressions.

  FIG. 3B is a graph showing the weighting factor F (c *) for saturation (c *), with the horizontal axis representing saturation (c *) and the vertical axis representing weighting factor F (c *). Is. The saturation (c *) takes a value from 0 to 160 or more, but here, it indicates a range from 0 to 160, and the weighting factor F (c *) is the weighting factor F (L *) of the lightness (L *). As in *), it takes a value from 0 to 1. In this graph, similarly to the weighting factor F (L *) of the lightness (L *), 1 is set for the value range of the saturation (c *) of the color that best displays the specific skin color, Lightness (c *) values outside the range are set to 0 through a function that monotonously decreases or monotonically increases from a range in which the weighting factor F (c *) is 1. Since the monotonically increasing or decreasing function is the same as the weighting factor F (L *) of the lightness (L *), detailed description thereof is omitted.

  FIG. 3C is a graph showing the weighting factor F (h *) for the hue (h *), where the horizontal axis is the hue (h *) and the vertical axis is the weighting factor F (h *). is there. The hue (h *) takes a value from 0 to 360 degrees, and the weighting factor F (h *) takes a value from 0 to 1 like the weighting factor F (L *) of the lightness (L *). is there. In this graph, similarly to the weighting factor F (L *) of the lightness (L *), 1 is set for the value range of the hue (h *) of the color that best displays the skin color as the specific color. The hue (h *) value other than the range is set to 0 through a function that monotonously decreases or monotonically increases from a range in which the weighting factor F (h *) is 1. The monotonically increasing or monotonically decreasing function is the same as the case of the lightness (L *) weighting factor F (L *), and thus detailed description thereof is omitted.

As described with reference to the above graph, the functions F (L *) and F (c *) of the respective weighting factors of the three parameters of lightness (L *), saturation (c *), and hue (h *) ), F (h *) is set, and the skin color index when the specific color is skin color is Hada (L *, c *, h *), the skin color index is multiplied by each weight coefficient,
Hada (L *, c *, h *) = F (L *) × F (c *) × F (h *)...
Can be defined as

For each of lightness (L *), saturation (c *), and hue (h *), the amount of change set by the user or the like is ΔL *, Δc *, Δh *, and the adjusted lightness (L *), If the saturation (c *) and hue (h *) values are L *, c *, and h *, the amount of adjustment will be multiplied by the skin color index.
ΔL * ・ Hada (L *, c *, h *)
Δc * · Hada (L *, c *, h *)
Δh * · Hada (L *, c *, h *)
It becomes. Therefore, if the adjusted values of lightness (L *), saturation (c *), and hue (h *) are L * ′, c * ′, and h * ′,
L * ′ = L * + ΔL * × Hada (L *, c *, h *) Equation 2
c * ′ = c * + Δc * × Hada (L *, c *, h *) Equation 3
h * ′ = h * + Δh * × Hada (L *, c *, h *) Equation 4
Can be obtained as

  The printer 1 is configured so that the user sets change amounts ΔL *, Δc *, and Δh * for lightness (L *), saturation (c *), and hue (h *), respectively, and a specific color correction program Based on the change amounts ΔL *, Δc *, Δh * set in 4a, the values of lightness (L *), saturation (c *), and hue (h *) are corrected as described above, and printing is performed. .

  FIG. 4 is a flowchart showing the processing of the specific color correction program 4a. In this case, image data formed by RGB ternary values is input from the external medium 40 mounted in the external media slot 6 and converted into R′G′B ′ ternary values in which the skin color as a specific color is corrected. The case will be described.

  First, RGB values are converted into XYZ values by ICCsRGB profile conversion (S1). Originally, it is preferable to use the ICC profile of the monitor or the ICC profile of the digital camera, but the ICCsRGB profile is used for simplicity. Here, the ICC profile indicates a color conversion file format that describes the color characteristics of a device defined by the ICC (International Color Consortium). Further, sRGB is a standard color space for a monitor created in an attempt to unify RGB color reproducibility and color space, which was different for each device. With reference to this ICCsRGB profile, conversion from RGB values to XYZ values is performed.

  Next, the XYZ values converted by the ICCsRGB profile conversion are converted into L * a * b * values (S2). This conversion is performed using a known conversion formula. Further, each value of L * c * h * is obtained from the value of L * a * b * (S3). In this case, the value of L * is not changed, and c * and h * are calculated by the following equations.

Next, skin color correction processing is performed based on these L * c * h * values (S4). This skin color correction process will be described later with reference to FIG. L * ′, c * ′, and h * ′ corrected by the skin color correction process are obtained.

  Next, the L * a * b * values corresponding to the corrected L * ′, c * ′, and h * ′ are obtained from these values, contrary to the conversion of S1, S2, and S3 (S5). An XYZ value corresponding to the L * a * b * value is obtained (S6), and an R′G′B ′ value corrected by ICCsRGB profile conversion is obtained (S7).

In this way, the printer 1 'converts the values, the converted R'G'B' input RGB values flesh color corrected R'G'B convert values into C MYK value by the color conversion program 4c Then, the printing process is performed by the printing control program 4d based on the CMYK value.

  FIG. 5 is a flowchart showing a skin color correction process which is the process of S4 in the flowchart of FIG. In this skin color correction process, first, ΔL *, Δc *, and Δh * as change amounts are input by the user (S11). Next, the weighting factors F (L *), F (c *), and F (h *) corresponding to the values of L *, c *, and h * obtained by the process of S3 are stored in the ROM 4 weights. The coefficient curve 4b is obtained with reference to (S12). Next, the skin color index Hada (L *, c *, h *) is obtained by multiplying these weighting factors by using Equation 1 (S13).

  Next, for each of the lightness (L *), saturation (c *), and hue (h *), the change amounts ΔL *, Δc *, and Δh * set by the user are calculated using Equations 2, 3, and 4. The lightness L * ′, saturation c * ′, and hue h * ′ are obtained by multiplying the skin color index and adding to each original value (S14).

  As described above, in the first embodiment, weighting factors are set for the values of lightness (L *), saturation (c *), and hue (h *), and the weighting factors are multiplied with each other. The adjustment amount is calculated by multiplying the specific color index by the change amount of each lightness (L *), saturation (c *), and hue (h *). The weighting coefficient has a value range indicating a specific color as 1, a value indicating a color that is not a specific color as 0, and its boundary is formed by a gentle monotone decay or monotone increase function. Therefore, since the weighting coefficient for the specific color is large and the weighting coefficient for the color adjacent to the specific color is set to gradually decrease, when correcting the specific color, the color that is not the specific color adjacent to the specific color Therefore, it is possible to prevent the adjustment amount from becoming excessive. If the adjustment amount is excessive, it is necessary to repeatedly set the change amount over and over again. However, since the adjustment amount is prevented from being excessive, it is possible to improve the work efficiency of the adjustment.

  Next, a second embodiment will be described. The description of the same parts as those of the first embodiment described above will be omitted, and only different parts will be described. In the first embodiment, the input RGB value is converted into an L * c * h * value, the respective weighting factors of each L * c * h * are obtained, and the weighting factors are multiplied together to specify a specific color. An index is calculated, and the specific color index is multiplied by the amount of change in each of the three parameters of lightness (L *), saturation (c *), and hue (h *), and each value of L * c * h * Is corrected, and these values are inversely transformed to correct the value of R′G′B ′.

  In the second embodiment, a lookup table for performing color correction of a specific color is stored based on a preset change amount, and the specific color is referred to by referring to this lookup table from the input RGB values. The R′G′B ′ value subjected to the color correction is directly obtained.

  FIG. 6 is a flowchart showing a process for creating a lookup table for performing color correction of a specific color. First, change amounts ΔL *, Δc *, and Δh * are input (S21). The change amounts ΔL *, Δc *, and Δh * may be input by a user, or a manufacturer that manufactures the printer 1 may input an optimal value for the printer 1 that is manufactured. Next, in order to obtain the corrected R′G′B ′ value for the RGB value in each grid of the RGB axes constituting the lookup table, the RGB value of the grid is sequentially designated (S22). Next, an R′G′B ′ value obtained by correcting a specific color is obtained for the designated RGB value, and the R′G′B ′ value corresponding to the RGB value is stored as a lookup table. (S23). The process of converting the RGB value into the R′G′B ′ value is the same as the process shown in FIG.

  Next, it is determined whether corrected R′G′B ′ values have been obtained for all grid positions (S24). If the corrected R′G′B ′ values for all grid positions have not been obtained (S24: No), the process returns to S22, and the R′G′B ′ values for the RGB values of the next designated grid are returned. If R′G′B ′ values corrected for all grid positions are obtained (S24: Yes), the process of creating this lookup table is terminated.

  The lookup table created in this way is stored in the RAM 3 or ROM 4 and the input RGB values can be converted to R'G'B 'by referring to the lookup table. In the case of storing in the RAM 3, it is preferable that the power is backed up so that the stored contents are not lost when the power of the printer 1 is cut off.

  As described above, in the second embodiment, a lookup table for converting RGB into R′G′B ′ is created as described above, and the lookup table is stored in the memory. , The weight coefficient is obtained to obtain the index of the specific color, and it is not necessary to calculate the adjustment amount according to the change amount, and the correction of the specific color can be performed appropriately and quickly with less processing.

  Next, a third embodiment will be described. The description of the same parts as those of the first embodiment described above will be omitted, and only different parts will be described. In the first embodiment, the functions F (L *), F (C *), F of the respective weighting factors of the three parameters of lightness (L *), saturation (c *), and hue (h *). (H *) is a region where the weighting factor of the color region indicated by the specific color is 1, the weighting factor of the region indicating the color which is not the specific color is 0, and the region where the weighting factor is 1 to the region where the weighting factor is not 0 The boundary weighting coefficient is formed by a gentle curve.

  However, this method may not be able to perform optimal correction according to the type of image on which color adjustment processing is performed. For example, taking skin color as an example, the skin color characteristics differ depending on the skin color of adults, the skin color of children, the skin color of men, the skin color of women, and the like. This difference is even more pronounced for different races. Therefore, it is the most appropriate method to obtain a function of an optimum weighting factor for each image and perform color adjustment using the function. In the third embodiment, an area including a large number of specific colors for color adjustment is extracted from a sample image taken with a digital camera or the like, and lightness (L *), saturation (c *), and hue (h *) in the area are extracted. ) And a weighting coefficient function is obtained based on the distribution.

  FIG. 7 shows an example of a sample image. When obtaining the distribution of lightness (L *), saturation (c *), and hue (h *) based on an image taken by a digital camera or the like, the image It is a schematic diagram which shows typically a mode that the area | region where many specific colors are included from is extracted. FIG. 7A schematically shows an image of a Japanese adult's face taken with a digital camera. FIG. 7B is a sample image in which the hair and eyes are removed from this original image. Is shown. Similarly, FIG. 7 (c) schematically shows an image obtained by photographing a Japanese infant's face with a digital camera. FIG. 7 (d) removes the hair and eyes from this original image. A sample image is shown. These sample images are extracted so as to include a region constituted by a specific color (in this example, skin color) and a region adjacent to the region and to be adjusted in harmony when the specific color is adjusted. It is a thing.

  FIG. 8 is a flowchart showing processing for obtaining a function of a weighting coefficient using this sample image. First, RGB values of a sample image are input, and the RGB values are converted into XYZ values by performing ICCsRGB profile conversion (S31). Next, the XYZ value is converted into an L * a * b * value (S32), and the L * a * b * value is further converted into an L * c * h * value (S33). Since these conversion methods are as described above, description thereof is omitted here. L * c * h * values can be obtained for all pixels forming the sample image converted in this way.

  Next, based on the L * value, c * value, and h * value for each pixel, each value is taken in each axis of lightness (L *), saturation (c *), and hue (h *). Count the number of pixels. For example, taking the lightness L * as an example, the number of pixels having a lightness L * of 0 and the number of pixels having a lightness L * of 1, respectively, from 0 to 100 of the lightness L *. It counts how many pixels exist for an integer value of. In this way, a histogram showing the distribution of each lightness (L *), saturation (c *), and hue (h *) is created (S34).

  FIG. 9 shows an example of a histogram created as described above. The histogram shown in FIG. 9 is a total of three 200 × 250 dot face images.

  FIG. 9A is a histogram showing the lightness (L *), where the horizontal axis indicates the lightness (L *) and the vertical axis indicates the number of pixels. As shown in this histogram, the number of pixels is the largest in the vicinity where the value of lightness (L *) is 80, and the maximum value is about 14,000 pixels. Similarly, FIG. 9B is a histogram showing saturation (c *), where the horizontal axis represents saturation (c *) and the vertical axis represents the number of pixels. As shown in this histogram, the number of pixels is the largest in the vicinity where the value of saturation (c *) is 40, and the maximum value is about 24,000 pixels. Similarly, FIG. 9C is a histogram showing the hue (h *), in which the horizontal axis represents hue (h *) and the vertical axis represents the number of pixels. As shown in this histogram, the number of pixels is the largest in the vicinity where the hue (h *) value is 70 degrees, and the maximum value is about 18,000 pixels.

  Next, an approximation function approximating each of these histograms is obtained (S35). As an approximate function, a Gaussian function indicating a normal distribution is used. By using a Gaussian function, a function that best approximates the histogram can be obtained. Gaussian function

And the approximate function is Fit (x, a, b) = Gauss (x, a, b) × (2-Gauss (x, a, b))
It is defined as Here, the approximate function of lightness (L *) is x = L *, the approximate function of saturation (c *) is x = c *, and the approximate function of hue (h *) is x = h *. It is what.

With this definition, for each lightness (L *), saturation (c *), and hue (h *), an approximate function that approximates each histogram is obtained by the least square method.
In the least square method, the approximation function for the lightness L * is set to Fit (L *), the value corresponding to the lightness L * of the histogram is set to hist (L *),

This is a method of obtaining the values of a and b that minimize the value of Curv. Note that Σ means obtaining a sum for all possible values of L *. In this embodiment, the range of L * is 0 to 100. This calculation can be obtained by sequentially changing the values of a and b using a computer. The saturation c * and the hue h * can also be obtained by the same calculation.

  For the histogram shown in FIG. 9, the approximate function of lightness L * is Fit (L *, 78, 220), the approximate function of chroma c * is Fit (c *, 42, 140), and the approximate function of hue h *. Fit (h *, 73, 220) was obtained. Note that the values of a and b may be sequentially changed and visually compared with each histogram to obtain the values of a and b that are closest to the histogram.

  As described above, in the third embodiment, each histogram of lightness (L *), saturation (c *), and hue (h *) is created for a sample image of a subject, and an approximate function that matches the histogram is obtained. The color of a specific color is finely adjusted using this approximate function as a weighting coefficient. Therefore, the specific color can be changed greatly, and the amount of change in the area adjacent to the specific color can be suppressed, so that the adjustment according to the actual image type can be performed efficiently.

  Therefore, in the case of adjusting the skin color, an adult skin color, a child skin color, a male skin color, a female skin color, and an approximate function corresponding to the race are respectively stored, and an operator provided on the operation panel 30 is used. It is possible to perform better adjustment by selecting any one of the approximation functions and performing adjustment according to the selected approximation function.

  The weighting factor acquisition unit according to claim 1 and the weighting factor acquisition step according to claim 5 or 7 correspond to the processing of S12 in the flowchart shown in FIG. 5, and the specific color index acquisition unit according to claim 1 and The specific color index acquisition step according to claim 5 or 7 corresponds to the processing of S13 in the flowchart shown in FIG. 5, and the change amount setting means according to claim 1 and the change amount setting step according to claim 5 or 7 include 5 corresponds to the process of S11 in the flowchart shown in FIG. 5, and the adjustment unit described in claim 1 and the adjustment step described in claim 5 or 7 correspond to the process of S14 in the flowchart shown in FIG.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be easily made without departing from the spirit of the present invention. It can be done.

  For example, in the first embodiment, image information RGB input from an external medium is first subjected to ICCsRGB profile conversion to obtain an XYG value, and then an L * a * b * value is calculated from the XYZ value. Although the value of L * c * h * is calculated from the value of * a * b * by calculation, it is directly converted to the value of L * c * h * by referring to the lookup table from the RGB value. You may make it convert.

  Also, when converting the value of L * 'c *' h * 'subjected to skin color correction into the value of R'G'B', R'G'B is directly converted by referring to a lookup table. 'It may be converted to a value.

  In the first embodiment, the printer 1 performs the correction process for the specific color. However, the PC 20 performs the correction process for the specific color, and the corrected image information (R′G′B ′). ) Or print information (CMYK) may be transmitted to the printer 1.

  In the second embodiment, based on the input change amounts ΔL *, Δc *, Δh *, a lookup table for converting RGB values into corrected R′G′B ′ values is created. Although the conversion to R′G′B ′ is performed using a lookup table, the printer 1 stores a lookup table for obtaining a CMYK value obtained by correcting a specific color from the RGB value, and from the RGB value. You may make it convert into a CMYK value.

  In the second embodiment, the printer 1 is provided with the lookup table in which the specific color is corrected. However, the PC 20 includes the lookup table, and the PC 20 performs the correction to perform the correction. Image information or print information may be transmitted to the printer 1.

FIG. 2 is a block diagram showing an electrical configuration of a printer and a personal computer in an embodiment of the present invention. (A) is a top view which shows the panel part of the external appearance of a printer, (b) is a front view. It is a graph which shows a weighting coefficient, (a) is lightness (L *), (b) is saturation (c *), (c) is a graph which each shows about hue (h *). It is a flowchart which shows a specific color adjustment process. It is a flowchart which shows a skin color correction process. It is a flowchart which shows the process which produces the look-up table which converts RGB value into R'G'B 'value which correct | amended the specific color in 2nd Embodiment. It is a figure which shows a sample image typically, (a) shows the image of an adult's face, (b) shows the image which extracted the field which contains many specific colors from the image of (a), ( (c) shows an image of an infant's face, and (d) is a schematic diagram showing images obtained by extracting regions containing a lot of specific colors from the image of (c). It is a flowchart which shows the process which calculates | requires an approximate function based on a sample image. It is a histogram created by counting the number of pixels corresponding to each value of brightness, saturation, and hue for each of the brightness, saturation, and hue of the sample image. (A) is a graph showing lightness (L *), (b) is saturation (c *), and (c) is a graph showing hue (h *).

Explanation of symbols

1 Printer 4 ROM (weighting coefficient curve storage means)
4e Look-up table (part of conversion means)
5 USB interface (input means)
6 External media slot (input means)
20 Personal computer

Claims (7)

An input unit that inputs a value of a combination of a plurality of basic colors included in color image information, a conversion unit that converts image information input to the input unit into values of brightness, hue, and saturation, and a conversion unit Image processing comprising adjustment means for adjusting the converted values of brightness, hue, and saturation, and correction means for correcting a color image based on the values of brightness, hue, and saturation adjusted by the adjustment means In the device
For each value of hue and saturation, a weighting factor for a value indicating a specific color is set to a first predetermined value, and a weighting factor for a value in a predetermined range continuing to the value indicating a specific color is set to the first predetermined value. Is stored as a weighting coefficient curve that is a value obtained by a monotonically decreasing or monotonically increasing function with the value of maximal being the maximum, and for the lightness value, the weighting coefficient for the value indicating the specific color is the first predetermined value In addition, a weighting factor for a value in a predetermined range continuous with a value indicating a specific color is a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum, and the brightness is a maximum value. Weight coefficient curve storage means for storing a weight coefficient in a certain case as a weight coefficient curve having a second predetermined value other than 0;
A weighting factor acquisition unit for obtaining a weighting factor corresponding to each value of brightness, hue, and saturation converted by the converting unit by referring to a weighting factor curve stored in the weighting factor curve storage unit;
Specific color index acquisition means for obtaining a specific color index by multiplying each weight coefficient acquired by the weight coefficient acquisition means,
A change amount setting means for setting a change amount of each value of brightness, hue, and saturation,
The adjustment unit sets an adjustment amount by multiplying the change amount set by the change amount setting unit by the specific color index obtained by the specific color index acquisition unit, and based on the adjustment amount, brightness, hue An image processing apparatus for adjusting each value of saturation. The monotonically increasing or monotonically decreasing function for obtaining a weighting factor for a predetermined range of values that are continuous with the value indicating the specific color in the weighting factor curve stored in the weighting factor curve storage means is a sine function or a cosine function. The image processing apparatus according to claim 1 . Wherein the specific color, the image processing apparatus according to claim 1 or 2, wherein it is a skin color. An image processing program that is executed in an image processing apparatus that includes an input unit that inputs values of combinations of a plurality of basic colors included in color image information and processes a color image input to the input unit ,
A conversion step of converting the image information input to the input means into values of brightness, hue, and saturation;
The weighting coefficient corresponding to each value of lightness, hue, and saturation converted by the conversion step is set as the first predetermined value for the value indicating the specific color for each value of hue and saturation. And storing a weighting factor for a value in a predetermined range continuous with a value indicating a specific color as a weighting factor curve having a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value as a maximum, For the value of brightness, the weighting coefficient for the value indicating the specific color is set to the first predetermined value, and the weighting coefficient for the value in a predetermined range continuous to the value indicating the specific color is maximized with the first predetermined value. A weight coefficient curve storage that stores a value obtained by a monotonically decreasing or monotonically increasing function as a weight coefficient curve in which the weight coefficient when the brightness is the maximum value is a second predetermined value that is not 0 means And the weighting coefficient obtaining step of obtaining by reference,
A specific color index obtaining step for obtaining a specific color index by mutually multiplying each weight coefficient obtained by the weight coefficient obtaining step;
A change amount setting step for setting a change amount of each value of brightness, hue, and saturation ;
An adjustment amount is set by multiplying the change amount set in the change amount setting step by the specific color index obtained in the specific color index acquisition step, and each of brightness, hue, and saturation is set based on the adjustment amount. An adjustment step to adjust the value;
An image processing program comprising: a correction step for correcting a color image based on values of brightness, hue, and saturation adjusted by the adjustment step . The image processing program according to claim 4 , wherein the specific color is a skin color. An input step for inputting a value of a combination of a plurality of basic colors included in color image information, a conversion step for converting the image information input in the input step into three values of brightness, hue, and saturation, and the conversion step An adjustment step for adjusting the brightness, hue, and saturation values converted by the correction step, and a correction step for correcting the color image based on the brightness, hue, and saturation values adjusted by the adjustment step. In the image processing method,
For each value of hue and saturation, a weighting factor for a value indicating a specific color is set to a first predetermined value, and a weighting factor for a value in a predetermined range continuing to the value indicating a specific color is set to the first predetermined value. A weight coefficient curve that is a value obtained by a monotonically decreasing or monotonically increasing function with the value of maximal as the maximum value, and for the brightness value, the weight coefficient for the value indicating the specific color is the first predetermined value, When the weight coefficient for a predetermined range of values that are continuous with a value indicating a specific color is a value obtained by a monotonically decreasing or monotonically increasing function with the first predetermined value being the maximum, and the brightness is the maximum value A weighting factor curve forming step for forming a weighting factor curve as a weighting factor curve having a second predetermined value other than 0 as a weighting factor;
A weighting factor acquisition step for obtaining a weighting factor corresponding to each value of brightness, hue, and saturation converted by the conversion step by referring to the weighting factor curve formed by the weighting factor curve forming step;
A specific color index obtaining step for obtaining a specific color index by mutually multiplying each weight coefficient obtained by the weight coefficient obtaining step;
A change amount setting step for setting a change amount of each value of brightness, hue, and saturation,
The adjustment step sets an adjustment amount by multiplying the change amount set by the change amount setting step by the specific color index obtained by the specific color index acquisition step, and brightness based on the adjustment amount, An image processing method characterized by adjusting each value of hue and saturation. The image processing method according to claim 6 , wherein the specific color is a skin color.