JPH0614184A - Color correction device - Google Patents

Abstract

(57) [Abstract] [Purpose] The area of the color tone correction is specified by the value (HSL value) in the color space, but the capacity of the storage device is prevented from being enlarged and the color tone is smoothly corrected. [Structure] An HSL value of each pixel of the original image stored in the first frame memory 2 is obtained using a look-up table 12 for converting an RGB signal into an HSL value, and stored in the effective range memory 11. It is determined by comparing with dH, dS, dL whether each pixel is in the area in the designated color space, and kr, kg, stored in the parameter memory 13 for the RGB signal of the determined pixel. kb is applied to correct the color tone. At this time, the corrected colors H _U, S _U,
The values of kr, kg, kb are changed according to the difference amount between the L _U data and the Hij, Sij, Lij data of the determined pixel,
A new parameter that changes smoothly is calculated and used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tone correction device used in, for example, a video plate making process, and more particularly, to an RGB signal of a pixel corresponding to a color to be corrected in an original image, which is converted into an RGB signal of a desired target color. The present invention relates to a device that corrects the color tone of an original image by converting it into a signal.

[0002]

2. Description of the Related Art Parameters for changing RGB signal values of an original image in accordance with a target color are used in color tone correction processing.
For example, if the red component of the original image is to be increased, the value of the parameter that acts on the R signal is increased, and if the green component is to be increased, the value of the parameter that acts on the G signal is increased to perform the tone correction processing. . Since applying a parameter to each pixel of the original image results in a huge amount of calculation,
Color tone correction is often performed using a look-up table in which preset parameters are applied to the values of the R, G, and B signals. When it is desired to correct the color tone of only a specific area in the original image, the specific area is specified by a pointing device such as a mouse, and the above parameters are applied only to the RGB signals of the pixels in the specified area.

[0003]

First, it is difficult and complicated to specify a specific area. For example, in the situation where you want to change the color of the red sweater in the original image but do not want to change the red color of the apple in the vicinity, operate the pointing device such as the mouse along the outline of the sweater to adjust the color tone area. Need to be specified, which causes a problem that the time required for the color tone correction processing is extended.

Therefore, a method of designating an area in a color space and performing color correction processing only on pixels in the area is considered instead of the above-described geometrical area specification. As a color space, H having three-dimensional coordinates of hue H, saturation S, and lightness L, which are three attribute values of human perceptual color, are used.
It is preferable to use the SL color space, which is the RGB of each pixel of the original image.
Convert the signal value to its HSL value and specify the specified HS
An apparatus has been proposed in which it is determined whether or not the pixel is within the range of the L color space, the HSL value of the pixel within the range is corrected, and this is converted back to the original RGB signal.

However, in such a device, RG
A means (look-up table or the like) for converting the value of the B signal into the value of the HSL and another look-up table as a means for inversely converting the value of the HSL into the value of the RGB signal are required. In order for the two transformations to be reversible, the lookup table must have sufficient accuracy,
A large-capacity storage device is required to store these tables, which causes a problem of high cost of the color tone correction device.

Next, in both of the above-described geometrical specific area designation and the specific area designation in the color space, if the original image has a smooth change as a whole, it is specified in that. Since an area is specified and color conversion in the area is performed using parameters, there is a problem that an unnatural image in which the color changes abruptly at the boundary of the area.

The present invention has been made in view of the above circumstances, and enlarges the capacity of the storage device as described above while designating the area for color tone correction with a value in the color space. It is an object of the present invention to provide a color tone correction device that does not impair the smoothness of a specific area of an original image having a smoothly changing image signal.

[0008]

The present invention has the following constitution in order to achieve the above object. That is, the invention according to claim 1 is an original image data storage unit for storing the digitized three primary color signals (RGB signals) of each pixel of the original image and three attribute values (HSL) of the perceptual color of the RGB signals.
Value), an image data conversion table, a target color to be the center of the color tone correction processing, a HSL value in the effective range of the color tone correction processing based on the color to be corrected,
And processing condition designating means for designating a target color after tone correction, and parameter calculating means for computing a parameter for tone correction processing based on the color to be modified and the target color designated by the processing condition designating means, An HSL value obtained by applying the RGB signal of each pixel of the original image stored in the original image data storage means to the image data conversion table;
The first processing means for comparing the HSL value indicating the effective range of the color tone correction processing designated by the processing condition designation means to determine the pixel to be the target of the color tone correction processing; and the first processing means. A second processing unit that applies the parameter calculated by the parameter calculation unit to the RGB signal of the pixel to perform the color tone correction process is provided.

According to a second aspect of the present invention, in the color tone correcting apparatus according to the first aspect, the H of the pixel corresponding to the color to be corrected is H.
The difference value between the SL value and the HSL value of the pixel determined to be the color tone correction target by the first processing means is calculated, and the parameter for the color tone correction processing becomes smaller as the difference value increases. Is provided with a parameter correcting means.

Further, according to the invention described in claim 3, in the color tone correction device according to claim 1, the color to be corrected which is the object center of the color tone correction processing designated by the processing condition designating means and the color tone corrected And a display means for displaying the target color of.

[0011]

The operation of the invention according to claim 1 is as follows. The HSL value indicating the effective range of the color tone correction processing designated by the processing condition designation means and the RGB of each pixel of the original image.
The HSL value obtained by applying the signal to the image data conversion table is compared to determine whether or not the pixel is a target of color tone correction (first processing means), and the pixel determined to be the target. The parameter calculated by the parameter calculating means is applied to the RGB signal of to perform the color tone correction processing (second processing means).

In other words, the RGB signal is converted into the HSL value only for determining the target pixel of the color tone correction processing, and the actual color tone correction processing is performed on the RGB signal of the target pixel. It is sufficient to have only one image data conversion table for converting to the HSL value, and the effective range of the processing can be input by the HSL value which is the value of the color space, but the expansion of the capacity of the storage device is avoided.

The operation of the invention according to claim 2 is as follows. Since the HSL value (hsl) of the pixel determined to be the color tone correction target by the first processing means is a value determined to be within the effective range with the color to be corrected as a reference, this value and the color to be corrected are The difference value from the HSL value (HSL) of the corresponding pixel has a minimum value when (HSL) = (hsl), and (hsl) is the limit value of the effective range, that is, the target pixel of the color tone correction processing in the color space. Becomes larger as it approaches the boundary value between the target pixel and the non-target pixel.

Since the parameter correcting means corrects the calculated parameter so that it becomes smaller as the difference value becomes larger, the second parameter using this parameter is corrected.
The intensity of the color tone correction processing in the processing means becomes minimum at the boundary between the target pixel and the non-target pixel, and increases as the target pixel approaches the pixel corresponding to the color to be corrected. Therefore, in the image after the color tone correction processing, the color does not suddenly change at the boundary between the target pixel and the non-target pixel.

The operation of the invention according to claim 3 is as follows. That is, since the target color of the color tone correction processing designated by the processing condition designating means and the display means for displaying the target color after the color tone correction are provided,
The difference between both colors can be confirmed on the same display device, which is convenient in practice.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of the color tone correction device. An image monitor 3 that displays an image to be processed to which color tone correction (hereinafter, simply referred to as color correction) and an image after color correction are displayed.
The main components are a data input device 4, a magneto-optical disk drive device 1 for storing image data (a magneto-optical disk driver 1), and a frame memory unit 20 incorporating a frame memory for storing image data before and after correction. Is.

The data input device 4 includes an operation monitor 9 for inputting data from a user of the device, a keyboard 10, a mouse 5, and a computer main body 21 having color correction processing as main functions. It is composed of.

FIG. 2 shows a system block diagram of the present apparatus, and the configuration and operation of the present apparatus will be described with reference to this block diagram, including the operation of the user. However, in FIG. 2, among the processing functions of the computer main body 21, the functions relating to the color correction processing are independently shown as a block diagram, and other processing, for example, processing for outputting and displaying data on the operation monitor 9 and the like. It is assumed that the data input device 4 has a function of performing.

The magneto-optical disk driver 1 is for taking in a digitized image signal of an image to be processed (hereinafter referred to as an original image) to this apparatus. Although it is assumed that the original image signal is stored in the magneto-optical disk, it may be stored in a magnetic tape or a hard disk. In such a case, the drive device that accesses each storage medium replaces the magneto-optical disk driver 1.

The first frame memory 2 stores R for one frame of the original image read by the magneto-optical disk driver 1.
It has a storage capacity for storing the respective three primary color signals of (red), G (green) and B (blue). The original image signal in the first frame memory 2 is output to the image monitor 3 via the internal switch SW and displayed as an image. When the user of this device operates the pointing device such as the mouse 5 of the data input device 4 while looking at the screen and specifies the display position of the color to be corrected, the data input device 4 is displayed on the screen of the image monitor 3. First the coordinate data of the specified point
Is output as a read address to the frame memory 2.

Here, the read R, G, and B primary color signals are referred to as R _U, G _{U, and} B _U signals. The R _U, G _U, B _U signals are
The R, G, and B signals of the point (pixel) designated by the mouse 5 are the colors of the point designated by the user, that is, the color to be corrected visually determined by the user is strictly on the screen. It is affected not only by the color of the designated point of the, but also by the color around the designated point. Therefore, as the R _U, G _{U, and} B _U signals, an average of the values of the R, G, and B signals of 4 pixels adjacent to the point designated by the mouse 5 or 8 pixels in the vicinity may be used. .

The R _U, G _{U and} B _U signals are stored in the first pixel value memory 6
And is output to the parameter calculation unit 7, the color patch display memory 8 and the data input device 4. These memories and a memory described later are present as a part of a storage area of an internal memory (main storage device) of the computer main body 21, and each arithmetic processing unit executes a program according to its processing algorithm.
It corresponds to a PU (Central Processing Unit).

The color patch display memory 8 stores the above-mentioned R _U, G _U, B _{U at} an address corresponding to a predetermined area on the screen of the image monitor 3 (for example, near the lower left corner of the screen). The signal is stored and output to the image monitor 3, and the color patch of the color to be corrected is superimposed and displayed on the original image.
The color patch refers to a color patch in which a predetermined area on the image monitor 3 is filled with the color so that the user can independently observe the color to be corrected specified on the original image.

[0024] R _U, G _U, B _U signal data input device given 4 converts R _U, G _U, a B _U signal to a numerical value, and outputs displayed on the operation monitor 9. For example, if each of the R, G, and B signals stored in the first frame memory 2 is an 8-bit digital signal, it is converted into a decimal number and the numerical value from "0 to 255" is R _U, G. _{The U and} B _U signals may be represented, or further, the numerical value of “0 to 255” may be represented by a numerical value of “0 to 100 (%)”.

The user refers to the color patch of the color to be corrected displayed on the image monitor 3 and the values of the R _U, G _U, B _U signals displayed on the operation monitor 9 to process the image. The respective values of the R, G and B signals of the subsequent color (hereinafter, target color) are input from the keyboard 10. The data input device 4 performs conversion reverse to the above to generate R, G, B signals corresponding to the input values, and outputs the color patch display memory 8 and the parameter calculation unit 7.
Output to. The R, G, B signals of the target color will be referred to as R in the following.
_T, G _T, B _T signals.

The color patch display memory 8 has the R
_{U T,} G _U, B _U signals are stored in another memory location having the same area (for example, a memory location corresponding to the display location of the color patch of the color to be corrected) as R _T, G _T,
The B _T signal is stored and output to the image monitor 3, and the color patch of the target color is superimposed and displayed on the original image.

As described above, when the user inputs the values of the R _T, G _{T, and} B _T signals, the image (color patch) corresponding to the values is displayed on the image monitor 3 in real time. The correlation between the set R _T, G _{T, and} B _T signal values and the assumed target color can be immediately grasped.
If the color of the color patch is different from the expected target color, the target color can be specified easily and accurately by updating the values of the R _T, G _{T, and} B _T signals.

When the designation of the color to be corrected and the target color is completed,
Then, the user specifies the effective range of color correction from the color to be corrected to the target color. In this device, the effective range is specified by the hue H (Hu
e), saturation S (Saturation), and lightness L (Lightness). This is R, G, B
In such a color mixture system, it is necessary to always be aware of additive color mixture when handling colors, and it is difficult to intuitively specify the color. Therefore, the HSL color space having a color difference suitable for human perception difference is used. As the value of, the effective range of the color to be processed is specified.

The effective range is H _U ± dH, S _U , where H _{U is} the hue corresponding to the R _U, G _{U, and} B _U signals of the color to be corrected, S _{U is the} saturation, and L _U is _the lightness. ± dS, L _U d represented by ± dL
It is input as H, dS, dL and stored in the effective range memory 11.

The present apparatus uses the information input or extracted up to this point, that is, "R, G, B signals (R
_U, G _U, B _U signals) ”,“ R, G, B signals of target color (R _T,
G _T, B _T signal) ”,“ data dH of effective range of color correction,
dS, dL "is used to determine whether or not the color component of each pixel of the original image stored in the first frame memory 2 is within the effective range of the color correction, and whether the color correction is performed or not performed. Then, the color correction processing is performed.

First, the color component of each pixel of the original image is HSL.
The lookup table 12 for converting the values of R, G, and B into the values of hue H, saturation S, and lightness L in order to determine whether they are within the effective range of color correction in the color space is described below. Create and keep.

Since the values of R, G, B do not directly correspond to the values of hue H, saturation S, and lightness L, the values of R, G, B correspond to the Lab color system (corresponding to lightness L). The one-dimensional coordinates, and the saturation S and the hue H are converted into the values of the three-dimensional coordinate space consisting of the two-dimensional coordinates drawn on the planes of the symbols a and b, and the values of the Lab color system are converted into the values of the HSL color space. Take the procedure of converting to a value.

In order to convert the values of R, G and B into the Lab display system, first, the tristimulus values Xima when the maximum values Rmax, Gmax and Bmax of R, G and B are added to the image monitor 3.
Measure x, Yimax, Zimax (i = R, G, B) with a spectroradiometer.

Next, using the gamma of the image monitor 3 (a constant indicating the relationship between the input signal of the color monitor and the light emission output: hereinafter, for convenience, represented by the symbol t), arbitrary RGB values r, g, and The tristimulus values X, Y, and Z when b is input are obtained by the following equation. X = Σ (j / imax) ^t · Ximax: (i = R, G, B,
j = r, g, b) Y = Σ (j / imax) ^t · Yimax: (i = R, G, B,
j = r, g, b) Z = Σ (j / imax) ^t · Zimax: (i = R, G, B,
j = r, g, b) In the above equations, each time i = R, G, B changes, j = r, g, b.

Using these tristimulus values X, Y, Z, R, G,
The value of B is converted into the value of Lab color system by the following formula. L = 116 ・ (Y / Yn) ¹ / 3-16 a = 500 ・ [(X / Xn) ¹ / 3- (Y / Yn) ^1/3 ] b = 200 ・ [(Y / Yn) ^1/3 − (Z / Zn) ^1/3 ] where Yn = ΣYimax (i = R, G, B), Xn =
ΣXimax (i = R, G, B), Zn = ΣZimax (i
= R, G, B).

FIG. 3 shows the correlation between the Lab color system and the HSL color space. In FIG. 3, the L axis of the Lab color system directly corresponds to the lightness L of the HSL color space, the radius vector on the two-dimensional coordinates of the a axis and the b axis corresponds to the saturation S, and the b axis and the radius vector The angle θ formed by corresponds to the hue H. Therefore, the value of L obtained above is directly used as the value of the lightness of the HSL color space,
The saturation S and the hue H are obtained using the following equations.

S ² = A ² + B ² H = tan ⁻¹ (B / A) However, when A <0, 180 degrees is added to the calculation result of the hue H, and when A> 0 and B <0, Add 360 degrees. This is because the calculation result does not give a negative value.

The lookup table 12 shown in FIG. 2 stores the values of H, S, L corresponding to the values of the R, G, B signals obtained by the respective arithmetic expressions as described above. But,
If the values of H, S, L corresponding to the number of bits (n bits) of the digitized R, G, B signals are made into a table, an enormous amount of data will result. Therefore, for example, the lower several bits of n bits should be deleted. It is assumed that the number of bits is m (n> m), and the values of H, S, and L corresponding to the m-bit R, G, and B signals (represented by n bits because there is no need to reduce this data) are stored in the lookup table 12. It may be stored and configured.

As described above, the values of the R, G and B signals are converted into the values of the HSL color space so that the color components of each pixel of the original image are within the specified effective range of color correction. Since the converted value of the HSL color space is not used in the color correction processing, there is no particular problem with the accuracy reduction due to the reduction of the number of bits of the R, G, B signals.

Therefore, of the R _U, G _U, B _U signals (n bits) of the color to be corrected stored in the first pixel value memory 6, only the m bits excluding the lower several bits are looked up in the look-up table 12. To obtain n-bit H, S, L values. This is represented as H _U, S _U, L _U. H _U, S _U, L _U are stored in another storage area of the first pixel value memory 6.

Further, the parameter calculation unit 7 to which the R _U, G _U, B _U signals of the color to be corrected and the R _T, G _T, B _T signals of the target color are given, performs the color correction processing by the following equations. Calculate the required parameters kr, kg, kb. _{kr = R T / R U -1} kg = G T / G U -1 kb = B T / B U -1 calculated kr, kg, kb is stored in the parameter memory 13.

Next, the R, G, B signals of each pixel of the original image stored in the first frame memory 2 are sequentially read out and temporarily stored in the second pixel value memory 14. If the number of pixels in the horizontal direction of the first frame memory 2 is x and the number of pixels in the vertical direction is y, then pixels ij (i = 1, 2, ... X, j
= 1, 2, ..., Y) Rij, Gij, Bij signals are sequentially stored in the second pixel value memory 14, and, like the first pixel value memory 6, m bits of less than a few lower bits are stored. Ri
The j, Gij, Bij signals are output to the look-up table 12, and the corresponding n-bit Hij, Sij, Lij are the second.
The pixel value memory 14 is stored in another storage area. The Rij, Gij, Bij signals are also output to the color correction processing unit 15. This is the original n with the low order bits not removed.
It is a bit signal.

The comparison unit 16 compares H _U, S _U, L _U stored in the first pixel value memory 6 with Hij, Sij, Lij sequentially stored in the second pixel value memory 14. Then, the absolute difference amount is stored in the effective range memory 11 d
It is determined whether or not it is larger than the values of H, dS, and dL. The comparison formula is shown below. _{| Hij-H U | <dH} | Sij-S U | <dS | Lij-L U | <dL

When all the values of Hij, Sij, and Lij satisfy the above-mentioned comparison expression (when the value of the HSL color space of the pixel ij read from the first frame memory 2 is within the effective range) ), The comparison unit 16 outputs a control signal for instructing the color correction processing unit 15 to perform the processing. Conversely, Hij, Sij, L
When any one of ij does not satisfy the above comparison expression (when it is outside the valid range), the color correction processing unit 15
A control signal for instructing to default processing is output to.

The color correction processing unit 15 receives the R _U, G _U, B _U signals (the number of bits is not reduced n) stored in the first pixel value memory 6 on the basis of the control signal indicating the performance of the process.
Signal), and data of H _U, S _U, L _U , data of Hij, Sij, Lij stored in the second pixel value memory 14, dH, d stored in the effective range memory 11.
The S, dL data and the kr, kg, kb data stored in the parameter memory 13 are read out, and the color correction processing of the Rij, Gij, Bij signals output from the second pixel value memory 14 is performed as follows. Then, it is stored in the second frame memory 17. When a control signal indicating failure of processing is given from the comparison unit 16, the second
Rij, Gij, Bij output from the pixel value memory 14 of
The signal is stored as it is in the second frame memory 17.

In the color correction processing, basically, kr, kg and kb calculated by the parameter calculation unit 7 are multiplied by the Rij, Gij and Bij signals of the pixel ij determined to be processed, and this is further multiplied. Although it is performed by adding to the Rij, Gij, and Bij signals, the following problems may occur.

That is, as described above, the color correction processing is performed on the pixel group of the portion where the values of the R, G, and B signals of the original image change smoothly, based on the specified effective range.
When the default is distinguished, the color may suddenly change in the middle of the smoothly changing pixel group, and the image may be unnatural. A phenomenon called so-called tone jump occurs. Therefore, in order to mitigate such a problem, the following processing is performed before the color correction processing is performed.

First, the Rij, Gij, and Bij signals Hij, Sij, and Bij of the pixel ij to be processed are expressed by the following equations.
Lij data and R _U, G _U, B _U signal H _U, S _U,
The absolute values ΔH, ΔS, ΔL of the difference amount from the L _U data are calculated. │Hij-H _U │ = ΔH │Sij-S _U │ = ΔS │Lij-L _U │ = ΔL

The parameters kr and k are determined according to the difference amount.
The coefficient for varying g and kb is calculated by the following calculation. 1- (ΔH / dH) = kh 1- (ΔS / dS) = ks 1- (ΔL / dL) = kl In the above formula, dH, dS, dL are the values of the color correction processing stored in the effective range memory 11. A value indicating the effective range, that is, a boundary value between a pixel to be processed and a pixel not to be processed. Then, kh, ks, kl are ΔH, ΔS, Δ
It is a coefficient that approaches the minimum value “0” as L approaches dH, dS, dL, and approaches the maximum value “1” as ΔH, ΔS, ΔL becomes farther from dH, dS, dL.

Therefore, when the coefficients kh, ks, and kl are applied to the color correction parameters kr, kg, and kb by using the following formulas, the closer to the boundary value (the farther from the color to be corrected), the more kr , Kg, kb are made smaller, the farther from the boundary value (the closer to the color to be corrected),
New parameters are obtained that are equal to the values of kr, kg, kb. The parameters are represented by KR, KG, and KB. KR = kr * kh * ks * kl KG = kg * kh * ks * kl KB = kb * kh * ks * kl

Such parameters KR, KG, KB
Is used for the color correction processing, the color of the image does not suddenly change in the middle of the smoothly changing pixel group, and natural color correction can be performed.

The color correction processing section 15 includes a second pixel value memory 14
A value obtained by multiplying the Rij, Gij, Bij signals of the processing target pixel output from the above by the above parameters KR, KG, KB is added to perform color correction processing. rij = Rij (1 + KR) gij = Gij (1 + KG) bij = Bij (1 + KB) These rij, gij, and bij are the three primary color signals of the pixel ij after color correction processing and are stored in the second frame memory 17. To be done.

The image signal after the color correction processing stored in the second frame memory 17 and the unprocessed image (original image) signal stored in the first frame memory 2 are stored in the data input device 4, for example. An internal switch SW that is switched by the switch of the mouse 5 or the like selectively outputs the image to the image monitor 3 for display. The image after the color correction and the image before the color correction can be alternately compared, which is practically convenient.

According to the above-described embodiment, the color correction processing is performed only on the pixels within the designated effective range, but all the pixels of the original image are the target. That is,
In one image, all pixels within the specified color range are subjected to color correction processing. If this is inconvenient, the mouse 5 or the like of the data input device 4 may be used to perform the above processing only for the area.

[0055]

As is apparent from the above description, according to the color tone correcting apparatus of the invention described in claim 1, the RGB signal of each pixel of the original image is given to the conversion table to obtain the HSL of each pixel.
The value is calculated, the HSL value is compared with whether it is within the valid range, the pixel to be processed is determined, and the parameter is applied to the RGB signal of the determined pixel to perform the tone correction processing. There is only one table for converting the value to the value of HSL, and there is no need for reversible conversion, so a table with low accuracy is sufficient, and the effective range of processing can be input with the HSL value which is the value of the color space. Also, the capacity of the storage device is not increased, and the cost of the device can be reduced.

According to the second aspect of the invention, the difference value between the HSL value of the pixel corresponding to the color to be corrected in the original image and the HSL value of the pixel determined to be the tone correction target is large. As it becomes, the value of the parameter is corrected to be smaller and used for the color tone correction processing. Therefore, the intensity of the color tone correction processing becomes the minimum at the boundary between the pixel to which this processing is applied and the pixel to which this processing is not applied, and this processing is performed. It is possible to make a smooth tone correction in which the intensity is maximized as the pixel to be corrected approaches the value in the color space of the pixel corresponding to the color to be corrected, and a natural image that avoids the phenomenon called tone jump is created. Obtainable.

Further, in the invention according to claim 3, since the display means for displaying the color to be corrected and the target color is provided, the difference between the two colors can be confirmed on the same display device, and the target color can be designated. It is convenient when doing.

[Brief description of drawings]

FIG. 1 is an external perspective view of an embodiment of a color tone correcting device of the present invention.

FIG. 2 is a block diagram showing its internal configuration.

[Fig. 3] HS in which the values of hue, saturation, and lightness are three-dimensional coordinates
It is a figure which shows the correlation of L color space and Lab color system.

[Explanation of symbols]

2 ... First frame memory (original image data storage means) 3 ... Image monitor (display means) 4 ... Data input device (processing condition designating means) 7 ... Parameter calculation unit (parameter calculation) Means) 12 ... Look-up table (image data conversion means) 15 ... Color correction processing section (second processing means, parameter correction means) 16 ... Comparison section (first processing means)

Claims (3)

[Claims] 1. An original image data storage unit for storing the digitized three primary color signals (RGB signals) of each pixel of the original image, and an image for converting the RGB signals into three attribute values (HSL values) of perceptual colors. The data conversion table, the designation of the color to be corrected which is the center of the color tone correction processing, the designation with the HSL value of the effective range of the color tone correction processing based on the color to be corrected, and the designation of the target color after color tone correction Processing condition specifying means for performing, parameter calculating means for calculating a parameter for tone correction processing based on the color to be corrected and the target color specified by the processing condition specifying means, and the original image data stored in the original image data storage means. An HSL value obtained by giving the RGB signal of each pixel of the image to the image data conversion table and an HSL value indicating the effective range of the color tone correction processing designated by the processing condition designating means. And a first processing unit that determines a pixel to be subjected to a color tone correction process by comparing the RGB signals of the pixels determined by the first processing unit with a parameter calculated by the parameter calculation unit. A color tone correction device, comprising: a second processing unit that performs a correction process. 2. The color tone correction device according to claim 1, wherein a difference value between the HSL value of the pixel corresponding to the color to be corrected and the HSL value of the pixel determined to be the color tone correction target by the first processing unit is calculated. A tone correction device comprising a parameter correction unit that calculates and corrects the parameter so that the parameter for the tone correction process decreases as the difference value increases. 3. The color tone correcting apparatus according to claim 1, wherein a display means for displaying a color to be corrected which is a target of the color tone correction processing designated by the processing condition designating means and a target color after the color tone correction. Tone correction device equipped with.