JP2000188694A - Signal processor and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perceive a color as being formed an approximate color by providing a conversion means nearly fixing brightness and hue to compress saturation for converting a chrominance signal in a first color reproducing area to a chrominance signal in a second color reproducing area which differs from the first color reproducing area by allowing the conversion means to increase compressibility near the highest saturation. SOLUTION: In accordance with an input/output relation fixed from brightness range information extracted from monitor color area information and printer color area information and a prescribed compressing relation, a brightness compression part 103 executes brightness compression on an inputted L signal and outputs an L signal being the result of the compression to a chrominance signal combining part 105. According to an input/output relation fixed from a saturation range information extracted from monitor color area information and printer color area information and a prescribed compressing relation, a saturation compression part 104 executes saturation compression on an inputted signal ab and outputs signal ab which is the result of the compression to the part 105. The part 105 combines the L signal and the ab signal and outputs the result to a color area inspecting part 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus and method, and more particularly to a signal processing apparatus and method for performing gamut compression.

[0002]

2. Description of the Related Art In a computer system or a video printer having a color monitor and a color printer, a color image created and / or processed on a monitor or a color image received by a receiver may be printed out.

A color monitor that emits light of a specific wavelength by using a phosphor to express a color image, and a color printer that absorbs light of a specific wavelength by using ink and the like and expresses a color image by remaining reflected light. It is well known that the color gamut greatly differs between and. further,
The color monitors also have different color reproduction ranges, such as those using liquid crystal, those using an electron gun type CRT, and those using a plasma type. Similarly, a color printer also has a different color gamut due to differences in paper quality and the like, differences in the amount of ink used, and the like.

For this reason, in an image displayed on a color monitor, an image output by a color printer, or a color image output by using a plurality of types of printers and a plurality of types of recording paper, these colors are not used. Cannot be perfectly matched in the colorimetric sense. Therefore, when a human perceives a color image displayed (formed) on each output medium, a large difference is felt in the tint between the images.

As an image processing technique for absorbing perceptual differences in color of a color image displayed (formed) between output media having different color reproduction ranges, and achieving perceptual matching of colors. , Gamut compression or color matching.

[0006]

According to an image processing technique, the sum of the squares of the differences between the color signals used in the color monitor and the color signals used in the color printer, that is, the sum of the squared differences is calculated for all the colors. Gamut compression is performed so that the sum of squared differences is minimized. However,
Although this technique provides good results within the color reproduction range of both devices, image information is significantly impaired due to loss of gradation for color signals outside the range. Therefore, in an image having a color signal outside the color reproduction range of both devices, the colors of the image displayed or formed by those devices are observed to be significantly different.

Further, in consideration of the above-mentioned problem of gradation, various gamut compression techniques have been developed under the condition that the gradation is not lost as much as possible. However, in these techniques, since the amplitude of the difference signal between the color signal of the color monitor and the color signal of the color printer when expressing a certain color becomes large in all colors, the display or formation by these devices is also performed. The color of the resulting image is observed to be significantly different.

Thus, there is a need for a gamut compression technique that can simultaneously solve the above two problems.

The present invention is directed to overcoming the problems set forth above, and converts color signals so that colors formed and / or displayed on different devices and / or different recording media are perceived as approximate colors. It is an object of the present invention to provide a signal processing device and a signal processing method capable of performing the same.

[0010]

The present invention has the following configuration as one means for achieving the above object.

[0011] The signal processing device according to the present invention compresses the lightness while keeping the chromaticity substantially constant, so that the color signal in the first color gamut is converted into a second signal different from the first color gamut. Conversion means for converting into a color signal in a color reproduction range, wherein the conversion means increases the compression ratio near the maximum lightness when the first and second color reproduction ranges have different maximum lightness, When the minimum lightness of the second color gamut is different from that of the second color gamut, the compression ratio near the minimum lightness is increased.

Further, by compressing the lightness while keeping the chromaticity substantially constant, the color signals in the first color gamut are converted into the color signals in the second color gamut different from the first color gamut. Converting means for converting, and obtaining means for obtaining the highest lightness and the lowest lightness at any chromaticity of the first and second color reproduction regions, respectively, wherein the converting means changes the conversion characteristic according to the chromaticity. Wherein the conversion characteristics at each chromaticity, when the highest brightness of the first and second color gamut are different from each other, the compression ratio near the highest brightness is large, the first and second color gamut If the minimum brightness differs from each other,
It is characterized in that the compression ratio near the minimum brightness is large.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into a color signal in the second color gamut different from the first color gamut. The image processing apparatus further includes a conversion unit that converts the signal into a signal, and the conversion unit increases a compression ratio near a maximum saturation.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into a color signal in a second color gamut different from the first color gamut. Conversion means for converting into a signal, acquisition means for acquiring the maximum saturation in each of the first and second color gamut at any hue, and conversion characteristics from the two maximum saturations acquired for each hue. Setting means for setting.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into a color signal in a second color gamut different from the first color gamut. Conversion means for converting into a signal, acquisition means for acquiring the maximum saturation in the arbitrary hue and arbitrary lightness of the first and second color gamut, and for each hue, from the two maximum saturations acquired Setting means for setting the conversion characteristic.

Further, by compressing the lightness while keeping the chromaticity substantially constant, the color signals in the first color gamut are converted into the color signals in the second color gamut different from the first color gamut. Conversion means for converting, a compression means for obtaining a third color gamut obtained by applying lightness compression and saturation compression to the first color gamut, and an arbitrary chromaticity of the second and third color gamut It is characterized by having acquisition means for acquiring the maximum lightness and minimum lightness, respectively, and adjusting means for adjusting the lightness by making the chromaticity substantially constant from the four lightnesses acquired for each chromaticity.

According to the signal processing method of the present invention, the color signal in the first color gamut is converted into the second color gamut different from the first color gamut by compressing the brightness with the chromaticity substantially constant. A signal processing method for converting into a color signal in a color reproduction range, wherein the highest brightness of the first and second color reproduction ranges is different from each other, the compression ratio near the highest brightness is increased, and the first and second When the minimum lightness of the color gamut is different from each other, the compression ratio near the minimum lightness is increased.

Further, the maximum lightness and the minimum lightness at arbitrary chromaticities of the first and second color reproduction regions are obtained, respectively.
Based on the acquired highest lightness and lowest lightness, by compressing the lightness with the chromaticity substantially constant, a color signal in the first color gamut, a second color different from the first color gamut A signal processing method for converting into a color signal within a reproduction range, wherein the conversion characteristic in the conversion is changed according to chromaticity, and the conversion characteristic in each chromaticity is the first and second color reproduction. When the highest lightness of the gamut is different from each other, the compression ratio near the highest lightness is large, and when the lowest lightness of the first and second color reproduction regions is different from each other, the compression ratio near the lowest lightness is large.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into a color signal in the second color gamut different from the first color gamut. A signal processing method for converting a signal into a signal, characterized in that a compression ratio near a maximum saturation is increased.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into the color signal in the second color gamut different from the first color gamut. A signal processing method for converting into a signal, wherein a maximum saturation in an arbitrary hue of the first and second color reproduction ranges is obtained, and a conversion characteristic is obtained from the obtained two maximum saturations for each hue. It is characterized by setting.

Further, by compressing the saturation while keeping the brightness and the hue substantially constant, the color signal in the first color gamut is converted into the color signal in the second color gamut different from the first color gamut. A signal processing method for converting into a signal, wherein the maximum saturation in any hue and any brightness of the first and second color reproduction gamut is obtained, and for each hue, from the obtained two maximum saturations The conversion characteristic is set.

Further, by compressing the lightness while keeping the chromaticity substantially constant, the color signals in the first color gamut are converted into the color signals in the second color gamut different from the first color gamut. A signal processing method for converting, wherein a third color gamut obtained by subjecting the first color gamut to lightness compression and chroma compression is obtained, and the second and third color gamut at an arbitrary chromaticity. It is characterized in that the maximum brightness and the minimum brightness are obtained, respectively, and the brightness is adjusted while keeping the chromaticity substantially constant from the four brightnesses obtained for each chromaticity.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a signal processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0024]

First Embodiment [System Configuration] FIG. 1 is a block diagram showing an example of a system configuration of a color signal conversion device according to a first embodiment of the present invention.

In FIG. 1, 201 is a CPU, 202 is a main memory such as a RAM, and 203 is a SCSI (Small Computer Standby).
ard Interface) interface (I / F), 204 is a network interface, 205 is a hard disk driver (HD
D), 206 is a graphic accelerator, 207 is a color monitor, 208 is a color signal converter, 209 is a color printer, 210
Is a keyboard / mouse controller, 211 is a keyboard,
212 is a pointing device such as a mouse, 213 is a local area network (LAN), and 214 is a PC, for example.
It is an I (Peripheral Component Interconnect) bus. Note that the CPU 201 executes various processes described below in accordance with programs and data stored in the ROM 215 and / or the HDD 205 in advance.

In the above configuration, the image data stored in the HDD 205 is transferred to the main memory 202 via the SCSI I / F 203 and the PCI bus 214 according to a command from the CPU 201.
In addition, image data stored in a server connected to the LAN 213, or image data on the Internet,
Network I / F 204 and PCI bus 2 by command of CPU 201
The data is transferred to the main memory 202 via. The image data held in the main memory 202 is
The data is transferred to the graphic accelerator 206 via the CI bus 214. The graphic accelerator 206 converts the image data from digital to analog (D / A) if necessary,
The data is transmitted to the color monitor 207 through the display cable. Therefore, an image corresponding to the image data is displayed on the color monitor 207.

Here, when an instruction (print command) for printing the image held in the main memory 202 by the color printer 209 is received from the user by the keyboard 211 or the mouse 212, the CPU 201 transmits the color gamut information of the appropriate color monitor. And the color gamut information of the appropriate color printer
The data is transferred from the HDD 205 to the main memory 202, and then the two pieces of color gamut information are transferred to the color signal converter 208.
Next, the image data held in the main memory 202 is sent to the color signal converter via the PCI bus 214 according to a command from the CPU 201.
Transferred to 208. After performing color signal conversion on the input image data, the color signal converter 208 transmits the converted image data to the color printer 209, and the color printer 2
At 09, an image corresponding to the image data is printed on the recording paper.

When issuing a print command or in advance, the user selects a printer model and a recording paper type to be used for printing, and a monitor model. Based on this selection information, the CPU 201 determines which of the plurality of pieces of color gamut information held in the HDD 205 should be selected.

[Color Signal Converter] FIG. 2 is a block diagram showing a configuration example of the color signal converter 208. In the present embodiment, an example will be described in which gamut compression is performed in the Lab color space.

The color signal converter 208 converts Lab signals on the color gamut (monitor gamut) of the monitor into Lab signals on the color gamut (printer gamut) of the printer. The main memory 202 is connected to the color signal converter 208 via the terminal 109.
Is input, the Lab signal of the image data, that is, the color signal on the monitor gamut as the conversion source is input. An output image to the printer, that is, a desired color signal on the printer gamut is output from the terminal 110.

Further, color gamut information (printer gamut information) of the printer is input from a terminal 111, and color gamut information (monitor gamut information) of a monitor is input from a terminal 112.
Monitor gamut information is stored in the storage unit 107, and printer gamut information is stored in the storage unit 108.

Reference numeral 102 denotes a color signal separation unit that separates an input Lab signal into a lightness component L and a chromaticity component ab, and outputs a lightness component L
The signal is output to lightness compression section 103, and the ab signal as the chromaticity component is output to saturation compression section 104. The brightness compression unit 103 performs brightness compression on the input L signal in accordance with brightness range information extracted from the monitor gamut information and the printer gamut information and an input / output relationship determined from a predetermined compression relationship. ,
The L signal resulting from the compression is output to color signal combining section 105. The saturation compression unit 104 performs the saturation processing on the input ab signal according to the saturation range information extracted from the monitor color gamut information and the printer color gamut information and the input / output relationship determined from a predetermined compression relationship. Performs compression, and outputs the resulting ab signal to the color signal synthesis unit 105.
Output to

The color signal synthesizing unit 105 synthesizes the input L signal and ab signal and outputs the synthesized signal to the color gamut inspection unit 106 as a Lab signal. The color gamut inspection unit 106 determines whether the input Lab signal is within the printer color gamut or outside the printer color gamut, and outputs the input Lab signal when the input Lab signal is within the printer color gamut, In some cases, a Lab signal in the printer color gamut that minimizes the color difference is output.

In the above configuration, the color signal converter 208 operates as follows. Prior to the operation, the color gamut information of the color monitor and the color gamut information of the printer are transmitted by a command from the CPU 201, and are stored in the storage units 107 and 108 as the monitor gamut information and the printer gamut information, respectively. Thereafter, the image data in which the color information is described by the Lab signal is transmitted to the color signal converter 208 via the PCI bus 214 in the raster scan order. Here, the color signal converter 208
The color signal conversion by gamut compression is performed on the Lab signal of each pixel in the image data, and the color signal is sequentially transmitted to the color printer 209.

That is, in this color signal conversion operation, the input Lab signal is first separated into an L signal and an ab signal by the color signal separation unit 102, and then the gamut signal is output to each circuit constituting the color signal converter 101. A compression process is performed.

Brightness Compression Unit The brightness compression unit 103 is controlled by a function f (·) that defines an input / output relationship. That is, the relationship of Lout = f (Lin) is established between Lin, which is an L signal input to brightness compression section 103, and Lout, which is an output L signal. f (•) is defined using a piecewise function consisting of n-1 segments, and is controlled so that the following condition is satisfied. Incidentally, n is the number of nodes of the piecewise function. f (・) is [Lmin_monitor, Lmax_monitor] f (・) is continuous at all points f (Lmin_monitor) = Lmin_printer f (Lmax_monitor) = Lmax_printer f '(Lmin_monitor) = α, α: 0 ≦ α f '(Lmax_monitor) = β, β: 0 ≦ β f (mi) = mi, i: 0 ≦ i ≦ n-2, mi: Lmin_printer <mi <
Lmax_printer f '(mi) = 1, i: 0 ≦ i ≦ n-2, mi: Lmin_printer <mi <
Lmax_printer f '(x) ≠ 0, x: Lmin_monitor <x <Lmax_monitor where Lmin_monitor: Black L value of monitor Lmax_monitor: White L value of monitor Lmin_printer: Black L value of printer Lmax_printer: White L of monitor Value α: Constant that controls the compression ratio near the brightest point of brightness compression β: Constant that controls the compression ratio near the darkest point of brightness compression mi: Any value

The constant α for controlling the compression ratio is Lmin_monitor
And Lmin_printer decrease as the difference increases. In other words, the compression ratio near the darkest point, which is the darkest point, increases. On the other hand, the constant β controlling the compression ratio is
It decreases as the difference between Lmax_monitor and Lmax_printer increases. In other words, the compression ratio near the brightest point, which is the brightest point, increases. In the present embodiment, f (·)
Is realized as a C2 continuous cubic spline function of, for example, 5 knots (4 segments). Also, for example, m1 = 40, m
2 = 50 and m3 = 70.

Here, in a printer output using this embodiment, Lmin_monitor = 0, Lmax_monitor = 100, Lm
FIG. 3 shows the input / output relationship of the brightness when in_printer = 20 and Lmax_printer = 90.

FIG. 4 is a block diagram showing a configuration example of the saturation compression unit 104.
The ab signal is input from the terminal 125, and the ab signal whose saturation is compressed is output from the terminal 126. Also, monitor gamut information is input from a terminal 127, and printer gamut information is input from a terminal 128.

The coordinate signal converter 121 converts the ab signal, whose chromaticity is represented by the rectangular coordinate system, into the hc signal, which represents the chromaticity by the polar coordinate system. Here, the h signal represents an angle in the polar coordinate system, that is, hue, and the c signal represents a distance from the origin in the polar coordinate system, that is, saturation. The color signal separation unit 122 separates the input hc signal into a hue component h and a saturation component c, and outputs the h signal, which is a hue component, to the coordinate signal conversion unit 124 and the saturation calculation unit 123. A certain c signal is output to the saturation calculator 123.

The saturation calculator 123 calculates the saturation range information in the hue determined from the h signal extracted from the monitor gamut information and the printer gamut information, and the input / output relationship determined from a predetermined compression relationship. Calculate the saturation to be output from the input c signal. The c signal resulting from the calculation is output to the coordinate signal converter 124. The coordinate signal conversion unit 124 converts the hc signal into an ab signal and outputs it.

The saturation calculator 123 is controlled by a function g (·) that defines an input / output relationship. That is, the saturation calculator 12
The relationship cout = g (cin) holds between the c signal cin input to 3 and the c signal cout output. g (·) is defined using a cubic function, and is controlled so that the following condition is satisfied. g (•) is [0, Cmax_monitor] g (0) = 0 g (Cmax_monitor) = Cmax_printer g '(0) = 1 g' (Cmax_monitor) = γ, γ: γ> 0 g '(x) ≠ 0, x: 0 ≦ x ≦ Cmax_monitor

In the above equation, Cmax_monitor is calculated from the h signal and the monitor gamut information, and is defined as the maximum chroma value of the monitor gamut at the hue determined from the h signal. Cmax_printer is calculated from the h signal and the moprinter color gamut information, and is defined as the maximum chroma value of the printer color gamut at the hue determined from the h signal. Γ is a value that controls the compression ratio of saturation compression near the maximum saturation, and Cmax_monitor and Cmax_monitor
The saturation calculation unit 123 automatically determines the relationship with or.
In the automatic setting of γ parameter, Cmax_monitor and Cmax_p
The value of γ decreases as the ratio Cmax_monitor / Cmax_printer to rinter increases. That is, the compression ratio increases.

FIG. 5 is a diagram showing the input / output relationship of saturation in a printer output using the present embodiment. In addition,
Cmax_monitor = 60.51 and Cmax_printer = 40.17.

According to the present embodiment, in a color monitor of a certain model and a color printer of a certain model, each brightness compression input when gamut compression is performed on a plurality of types of paper quality such as plain paper or special recording paper. FIG. 6 shows the superposition of the output characteristics. That is,
Medium brightness is preserved regardless of paper quality. On the other hand, near the brightest point or the darkest point, the compression ratio greatly changes depending on the lightness range in which color reproduction is possible.

According to this embodiment, color continuity is maintained,
In addition, it is possible to reproduce gradations outside the color gamut of the printer. In addition, humans are sensitive and natural images (photo images)
It is possible to reproduce the medium lightness region (see FIG. 3) and the low saturation region (see FIG. 5), which are color gamuts frequently included in the image, with high accuracy. Therefore, it is possible to satisfactorily reproduce an input image including a color outside the printer color gamut by the printer.

Further, since the medium lightness area and the low chroma area can be reproduced with high precision, as shown in FIG. 6, the medium lightness of various recording papers (recording media) having different color reproduction characteristics (color gamut) can be improved. In addition, it is possible to match the color reproducibility with respect to the low-saturation area, and it is possible to match the tint of each recording sheet.

[0048]

Second Embodiment Hereinafter, a signal processing device according to a second embodiment of the present invention will be described. Note that, in the present embodiment,
The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is a modification of the operation of the saturation compression section 104 in the first embodiment. Saturation compressor 104
Is controlled by a function g (·) that defines an input / output relationship. That is, between the c signal cin input to the saturation calculator 123 and the c signal cout output, cout = g
(cin). g (·) is defined using a piecewise function consisting of n-1 segments, and is controlled so that the following condition is satisfied. Incidentally, n is the number of nodes of the piecewise function. g (•) is [0, Cmax_monitor] g (0) = 0 g (Cmax_monitor) = Cmax_printer g '(0) = 1 g' (Cmax_monitor) = γ, γ: γ> 0 g (mi) = mi , i: 0 ≦ i ≦ n-2, mi: 0 <mi <Cmax_monito
r g '(mi) = 1, i: 0 ≦ i ≦ n-2, mi: 0 <mi <Cmax_monito
r g '(x) ≠ 0, x: 0 ≦ x ≦ Cmax_monitor

Here, Cmax_monitor is calculated from the h signal and monitor gamut information, and is defined as the maximum chroma value of the monitor gamut at the hue determined from the h signal. Also, Cm
ax_printer is calculated from the h signal and the printer gamut information, and is defined as the maximum saturation value of the printer gamut at the hue determined from the h signal. Further, γ is a value for controlling the compression ratio of the saturation compression near the maximum saturation, and the saturation calculation unit 123 automatically determines the relationship between Cmax_printer and Cmax_monitor under the restriction that the above condition is satisfied. In the γ parameter automatic setting, as the ratio Cmax_monitor / Cmax_printer between Cmax_monitor and Cmax_printer increases,
The value of γ decreases. That is, the compression ratio increases.

In this embodiment, g (·) is realized as a C2-continuous cubic spline function of, for example, two segments. For example, m1 = 1/2 × Cmax_monitor.

FIG. 7 is a diagram showing the input / output relationship of saturation in a printer output using the present embodiment. In addition,
Cmax_monitor = 60.51 and Cmax_printer = 40.17.

[0053]

Third Embodiment Hereinafter, a signal processing device according to a third embodiment of the present invention will be described. Note that, in the present embodiment,
The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 8 is a block diagram showing a configuration example of the color signal converter 208 according to the third embodiment of the present invention.

On the color gamut of the monitor (monitor gamut)
Lab signals are converted to the color gamut of the printer (printer gamut)
The terminal 109 is connected to the color signal converter 208 for converting to the above Lab signal.
, A Lab signal of the image data held in the main memory 202, that is, a color signal on a monitor gamut as a conversion source is input. An output image to the printer, that is, a desired color signal on the printer gamut is output from the terminal 110.

Further, color gamut information (printer gamut information) of the printer is input from a terminal 111, and color gamut information (monitor gamut information) of a monitor is input from a terminal 112.
Monitor gamut information is stored in the storage unit 107, and printer gamut information is stored in the storage unit 108. In addition, the storage unit 312 stores information on the result of compression of brightness and saturation with respect to the monitor color gamut.

A multiplexer (MUX) 302 is a storage unit based on a selection signal from the CPU 201 input via a terminal 313.
A signal input from 107 or terminal 109 is selected and output to color signal separation section 102. Color signal separation unit 102, brightness compression unit 10
3. Processing performed by the saturation compression unit 104 and the color signal synthesis unit 105 is the same as the processing described with reference to FIG. 2 in the first embodiment, and a description thereof will not be repeated.

The Lab signal output from the color signal synthesizing unit 105 is input to a demultiplexer (DMUX) 307 and output to the storage unit 312 or the brightness adjusting unit 308 according to a selection signal from the CPU 201. The lightness adjustment unit 308 converts the L signal according to the input / output relationship determined from the input Lab signal, the printer gamut information and the gamut compression information stored in the storage unit 312, and converts the Lab signal that is the conversion result. Color gamut inspection unit 1 described above
Output to 06.

In the above configuration, the color signal converter 208 operates as follows. Prior to the operation, the color gamut information of the color monitor and the color gamut information of the printer are transmitted by a command from the CPU 201, and are stored in the storage units 107 and 108 as the monitor gamut information and the printer gamut information, respectively. Next, the color signal converter 208 creates color gamut compression information, which is monitor color gamut information that has undergone lightness and saturation compression, and stores it in the storage unit 312. In this process, the MUX 302 selects a signal input from the storage unit 107, and the DMUX 307 selects a signal input from the storage unit 31.
Select output to 2.

When the above processing is completed, the color signal converter 208
Performs color signal conversion processing for performing gamut compression on the Lab signal on the input monitor gamut. In this process,
The MUX 302 selects the signal input from the terminal 109,
Selects the output to the brightness adjustment unit 308.

When the above operation is completed, the image data in which the color information is described by the Lab signal is transmitted to the color signal conversion device 301 via the PCI bus by the raster scan method.
Here, the color signal conversion device 301 performs color signal conversion based on gamut compression on the Lab signal of each pixel in the image data, and sequentially transmits the Lab signal to the printer. Therefore, image data in which color information is described by Lab signals is stored in the PCI bus 214.
Are transmitted to the color signal converter 208 in the order of raster scan, and the color signal converter 208 performs color signal conversion by gamut compression on the Lab signal of each pixel in the image data, and sequentially transmits the color signal to the color printer 209. .

● Brightness Adjustment Unit The brightness adjustment unit 308 extracts ab information from the input Lab signal, and uses the extracted ab information and printer gamut information to have the same value as the extracted ab information within the printer gamut. Lightness maximum value Lmax_printer_ab and lightness minimum value Lmin_
Extract printer_ab. Subsequently, in the monitor color gamut (hereinafter sometimes referred to as “compressed color gamut”) on which the brightness and saturation have been compressed, the extracted ab information and color gamut compression information are the same as the extracted ab information. Lightness maximum value Lm with value
ax_compressed_ab and minimum brightness Lmin_compressed_ab
Is extracted. These extracted information and the input La
From the L information Lin of the b signal, the brightness information Lout is obtained by the following procedure.
Is calculated.

Lmax_printer_ab, Lmin_printer_ab, Lmax
If any of _compressed_ab and Lmin_compressed_ab is not extracted, Lout = Lin.

In cases other than the above, Lout is calculated using the following equation.
Is calculated.

The lightness adjusting unit 308 outputs the obtained lightness information Lout
And outputs a Lab signal synthesized from the input Lab signal and the ab information of the input Lab signal.

According to the present embodiment, gamut compression can be performed with higher precision than in the first embodiment. That is, since the color gamut of the actual printer has a very complicated shape, the conversion based on the compression ratio set according to Cmax_printer of the first embodiment completely converts the input image data into the color gamut of the printer. It is not possible. On the other hand, according to the present embodiment, the gamut compression is performed based on the color gamut compression information which is the data on the input image after compression.
Higher precision gamut compression is achieved.

[0067]

Fourth Embodiment Hereinafter, a signal processing device according to a fourth embodiment of the present invention will be described. Note that, in the present embodiment,
The same components as those in the first and third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is a modification of the operation of the brightness adjusting section 308 in the third embodiment. Brightness adjustment unit 308
Extracts ab information from the input Lab signal, from the extracted ab information and printer gamut information, within the printer gamut, the lightness maximum value Lmax_printer_ab and the lightness minimum value Lmin_printer_ab having the same value as the extracted ab information Is extracted. Subsequently, a lightness maximum value Lmax_compressed_ab and a lightness minimum value Lmin_compressed_ab having the same value as the extracted ab information are extracted from the extracted ab information and color gamut compression information. From the extracted information and the L information Lin of the input Lab signal, brightness information Lout is calculated by the following procedure.

Lmax_printer_ab, Lmin_printer_ab, Lmax
If any of _compressed_ab and Lmin_compressed_ab is not extracted, Lout = Lin.

If the above does not apply, Lout is calculated using a function h (·) that defines the input / output relationship. That is, Lout = h
(Lin). h (·) is defined using a piecewise function consisting of n-1 segments, and is controlled so that the following condition is satisfied. Incidentally, n is the number of nodes of the piecewise function h (·). h (・) is [Lmin_compressed_ab, Lmax_compressed_ab] and h (・) is continuous at all points h (Lmin_compressed_ab) = Lmin_printer_ab h (Lmax_compressed_ab) = Lmax_printer_ab h '(Lmin_compressed_ab) = α, α: α h '(Lmax_compressed_ab) = β, β: 0 <β h (mi) = ni, i: 0 ≦ i ≦ n-2, mi: Lmin_compressed_ab <
mi <Lmax_compressed_ab, ni: Lmin_printer_ab <ni <
Lmax_printer_ab h '(mi) = 1, i: 0 ≦ i ≦ n-2, mi: Lmin_compressed_ab <
mi <Lmax_compressed_ab h '(x) ≠ 0, x: Lmin_compressed_ab ≦ x ≦ Lmax_compresse
d_ab

Here, α and β: are parameters that give the compression ratio at the end point of the table, and are automatically calculated under the restriction that the above condition is satisfied. Also, mi and ni are automatically calculated under the restriction that the above conditions are satisfied. Although an attempt is made to maintain the relationship of mi = ni as much as possible by an automatic calculation algorithm, the relationship (mi = ni) is not necessarily guaranteed because priority is given to maintaining the gradation and the above conditions. However, we strive to make the absolute difference | h (Lin)-Lin | between the input and output as small as possible at each point.

In the present embodiment, h (·) is set to C1 of three segments.
Implemented as a continuous cubic spline function. Also, m1 = 1
/ 3 × Cmax_monitor and m2 = 2/3 × Cmax_monitor.

FIG. 9 and FIG. 10 are diagrams showing the input / output relationship of the lightness at a certain chromaticity ab in a certain printer output using the present embodiment. Note that Lmin_compre in FIG.
ssed_ab = 40, Lmax_compressed_ab = 68, Lmin_printer_ab
= 45 and Lmax_printer_ab = 64. Also, Lmin_compressed_ab = 60, Lmax_compressed_ab = 84, FIG.
Lmin_printer_ab = 46 and Lmax_printer_ab = 75.

According to the present embodiment, since the non-linear transformation is used in the lightness compression, the reproducibility in the medium lightness region can be further improved. In particular, it is possible to improve the color reproducibility in an area such as cyan where the color gamut of the monitor and the color gamut of the printer do not have a similar relationship.

[0075]

Fifth Embodiment Hereinafter, a signal processing device according to a fourth embodiment of the present invention will be described. Note that, in the present embodiment,
For configurations substantially similar to the first, third and fourth embodiments,
The same reference numerals are given and the detailed description is omitted.

This embodiment is a modification of the configuration of the saturation compression unit 104 in the fourth embodiment. FIG. 11 is a block diagram illustrating a configuration example of the color signal converter 208 according to the present embodiment.
The difference from the configuration shown in FIG. 8 is that the L signal is input to the saturation compression section 104 together with the ab signal.

FIG. 12 is a block diagram showing an example of the configuration of the saturation compression section 104 of this embodiment. Saturation compression section 104 shown in FIG.
The difference is that the L signal is supplied to the saturation calculation unit 123 via a terminal 426.
Is to be entered.

The saturation calculation section 123 extracts the hue determined from the h signal extracted from the monitor gamut information and the printer gamut information, and the saturation range information at the brightness determined from the input L signal. According to the input / output relationship determined from the compression relationship, the saturation to be output is calculated from the input c signal. The c signal resulting from the calculation is output to the coordinate signal converter 124. The coordinate signal conversion unit 124 converts the hc signal into an ab signal and outputs it.

The operation of the saturation calculator 123 having the above configuration is described in FIG.
This will be described with reference to the flowchart shown in FIG.

At step S1000, the maximum saturation Cmax_printer of the printer gamut at hue h is determined from the hue h and the printer gamut information input to the saturation compression unit 104.
In S1001, from the hue h and the monitor gamut information input to the saturation compression unit 104, the maximum saturation C of the monitor gamut at the hue h is obtained.
max_monitor is calculated, and in step S1002, the saturation Cmax_print
ratio between er and saturation Cmax_monitor Rmax = Cmax_printer / Cmax_m
Ask for onitor.

Next, in step S1003, based on the hue h, lightness L, and printer gamut information input to the saturation compression unit 104,
Maximum chroma CL_monit of monitor color gamut at hue h and lightness L
is determined, and in step S1004, a ratio R = c / CL_monitor between the saturation c input to the saturation compression unit 104 and the maximum saturation CL_monitor is determined.

Next, in step S1005, the saturation ratio Rnew = g (R / Rmax) is determined using a function g (·) that defines the input / output relationship of the saturation ratio.
, And in step S1006, the saturation ratio Rnew and the maximum saturation CL_mo
The result of multiplication with nitor is output as a calculation result of the saturation calculation unit 123. Here, a function that defines the input / output relationship of the saturation ratio
g (•) is defined using a cubic function in the present embodiment, and is controlled as follows. g (•) is [0, 1] g (0) = 0 g (1) = Rmax g '(0) = 1 g' (Rmax) = γ, γ: γ> 0 g '(x) ≠ 0, x: 0 ≦ x ≦ 1

Here, γ is a value for controlling the compression ratio of the saturation compression in the vicinity of the maximum saturation at a certain hue and lightness, and Cmax_monitor
And Cmax_printer, the saturation calculation unit 123 automatically determines each combination of hue and lightness. In the γ parameter automatic setting, γ is Cmax_monitor / Cmax_pr
The value decreases as inter increases. That is, the compression ratio increases.

In this embodiment, the function g (·) for defining the input / output relationship is realized using a cubic function.
Even if it is realized using a piecewise function as in the second embodiment, the essence is not impaired at all.

According to this embodiment, linear compression can be performed outside the printer color gamut, and nonlinear compression can be performed within the printer color gamut so as to increase the compression ratio in the high chroma region. That is, by linearly compressing the saturation of the boundary of the monitor color gamut, it is possible to better express the gradation in the high chroma range. Therefore, reproducibility can be improved in the vivid gradation of colors often used in DTP, etc., and the medium-brightness area and low-saturation area, which are sensitive to humans, can be reproduced with high accuracy.
Images and the like can also be well reproduced.

[0086]

[Sixth Embodiment] Hereinafter, a signal processing device according to a sixth embodiment of the present invention will be described. Note that, in the present embodiment,
The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 14 shows a color signal converter 20 according to this embodiment.
8 is a block diagram showing a configuration example of FIG.

On the color reproduction range (monitor gamut) of the monitor
Lab signals are converted to the color gamut of the printer (printer gamut)
The terminal 109 is connected to the color signal converter 208 for converting to the above Lab signal.
, A Lab signal of the image data held in the main memory 202, that is, a color signal on a monitor gamut as a conversion source is input. An output image to the printer, that is, a desired color signal on the printer gamut is output from the terminal 110.

Also, color gamut information (printer gamut information) of the printer is input from a terminal 111, and color gamut information (monitor gamut information) of a monitor is input from a terminal 112.
Monitor gamut information is stored in the storage unit 107, and printer gamut information is stored in the storage unit 108.

The chrominance signal separating section 102 separates the input Lab signal into a lightness component and a chromaticity component, outputs an L signal as a lightness component to the lightness compression section 103 and the saturation compression section 104, Is output to the saturation compression unit 104.

The saturation compression section 104 performs saturation compression in accordance with the saturation range information extracted from the monitor gamut information and the printer gamut information, and the input / output relationship determined from a predetermined compression relationship. Is output to the brightness compression section 103. Further, the saturation compression unit 104 performs information processing by acquiring lightness information necessary for lightness compression from monitor gamut information. The extracted saturation range information and monitor brightness information are output to the brightness compression unit 103 as a signal 512.

[0092] The brightness compression section 103 converts the L signal according to the monitor brightness information and the extracted saturation range information processed by the saturation compression section 104 and the input / output relationship determined from a predetermined compression relationship. Lightness compression is performed, and the L signal as a result of the compression and the ab signal 51 input from the saturation compression unit 104
3 is output to the color gamut inspection unit 106 as a Lab signal.

[Saturation Compression Unit] FIG. 15 is a block diagram showing a configuration example of the saturation compression unit 104 of this embodiment. The difference from the saturation compression section 104 shown in FIG. 12 is that a brightness information calculation section 525 is provided. The brightness information calculation unit 525 calculates the maximum brightness and the minimum brightness of the monitor gamut at the chromaticity ab from the L signal, ab signal, and monitor gamut information input to the saturation compression unit 104, and outputs a signal from a terminal 529. Five
Output as 12.

The operation of the brightness compression section 103 in the above configuration will be described. The brightness compression unit 103 calculates the maximum brightness information Lmax_printer_ab and the minimum brightness information Lmin_printer_ab of the printer gamut at the chromaticity ab from the input ab signal and the printer gamut information.
Is calculated. Next, Lmax_monitor_ab is the maximum brightness information input to the brightness compression unit 103, and Lmin_monitor is the minimum brightness information.
As monitor_ab, a parameter required for brightness compression calculation is calculated from these four brightness information.

The calculated parameters and the brightness compression unit 103
Is output as the L signal Lin that is the brightness compression target that is input to
The signal Lout is calculated by a function f (·) that defines an input / output relationship with the L signal Lout. Here, f (·) is defined using a piecewise function composed of n−1 segments, and is restricted so that the following condition is satisfied. Incidentally, n is the number of nodes of the piecewise function. f (・) is [Lmin_monitor_ab, Lmax_monitor_ab] and f (・) is continuous at all points f (Lmin_monitor_ab) = Lmin_printer_ab f (Lmax_monitor_ab) = Lmax_printer_ab f '(Lmin_monitor_ab) = α, α ≦ α f '(Lmax_monitor_ab) = β, β: 0 ≦ β f (mi) = ni, i: 0 ≦ i ≦ n-2, mi: Lmin_monitor_ab <mi <
Lmax_monitor_ab ni: Lmin_printer_ab <ni <Lmax_printer_ab f '(x) ≠ 0, x: Lmin_monitor_ab <x <Lmax_monitor_ab

In this embodiment, f (·) is set to C2 of 5 segments.
Implemented as a continuous cubic spline function. Here, the number of contacts n, the values mi and ni at the contacts, and the compression ratios α and β at the end points of the table are Lmin_monitor_ab, Lmax_moni
It is automatically calculated from four brightness information of tor_ab, Lmin_printer_ab and LLmax_printer_ab. Here, a parameter is set by the parameter automatic setting algorithm so that f (x) = x as much as possible within a range that satisfies the gradation and the above conditions. The automatic setting algorithm for α and β is roughly as follows.

For α, Lmin_monitor_ab ≦ Lmin_prin
If ter_ab, Lmin_monitor_ab and Lmin_printer_ab
As the difference from becomes larger, α becomes smaller under the constraint condition of 0 ≦ α ≦ 1. That is, the compression ratio near the darkest point increases.

On the other hand, Lmin_monitor_ab> Lmin_printer_ab
In this case, as the difference between Lmin_monitor_ab and Lmin_printer_ab increases, α increases under the constraint of α> 1. That is, the elongation rate near the darkest point increases.

Similarly, for β, Lmax_monitor_ab ≧ Lma
If x_printer_ab, Lmax_monitor_ab and Lmax_prin
As the difference from ter_ab increases, β decreases under the constraint of 0 ≦ β ≦ 1. That is, the compression ratio near the brightest point increases.

On the other hand, Lmax_monitor_ab <Lmax_printer_ab
In the case of, as the difference between Lmax_monitor_ab and Lmax_printer_ab increases, β increases under the constraint condition of β> 1. That is, the elongation rate near the brightest point increases.

[0101]

Seventh Embodiment Hereinafter, a signal processing device according to a seventh embodiment of the present invention will be described. Note that, in the present embodiment,
For configurations substantially similar to the first, third and fourth embodiments,
The same reference numerals are given and the detailed description is omitted.

This embodiment is a modification of the configuration of the saturation compression section 104 in the fourth embodiment. FIG. 16 is a block diagram illustrating a configuration example of the color signal converter 208 according to the present embodiment.

The color saturation adjustment information input unit 618 is for the user to input color saturation adjustment information.
, A control panel formed as a user interface image on the color monitor 207, a keyboard 211 and / or a mouse 212, and the like. The saturation adjustment information input by the user giving the input value and the output value at each node is converted into an appropriate data structure by the CPU 201, and then temporarily stored in the main memory 20.
After being held at 2, the signal is input to the saturation compression unit 104 of the color signal converter 208 via the terminal 617. The input of the saturation adjustment information is not an essential operation.

Upon receiving an instruction to output the image held in the main memory 202 from the printer 209, the CPU 201 examines the stored contents of the main memory 202 to determine whether or not there has been input of the saturation adjustment information. The signal is sent to the signal converter 208. When the saturation adjustment information is input, the CPU 201 sends the saturation adjustment information held in the main memory 202 to the color signal converter 208 via the PCI bus 214 and the terminal 617.

The saturation compressing section 104 operates according to the saturation range information extracted from the monitor gamut information and the printer gamut information, and the input / output relationship determined from the compression relationship controlled by the input saturation adjustment information. Saturation compression is performed, and an ab signal as a result of the compression is output to the color signal synthesis unit 105.

The saturation adjustment information input section 618 in the above configuration is realized by the respective blocks in the configuration of FIG. 2 operating in a predetermined order as described above.

[Saturation Compression Unit] FIG. 17 is a block diagram showing a configuration example of the saturation compression unit 104.

In FIG. 17, storage section 625 stores saturation adjustment information input via terminal 630, and stores color signal separation section 12 information.
The saturation adjustment value corresponding to the h signal, which is the hue information input from 2, is output to the saturation calculation unit 123. The saturation calculator 123 is extracted from the monitor gamut information and the printer gamut information,
saturation range information for the hue determined from the h signal,
According to the input / output relationship determined from the compression relationship controlled by the saturation adjustment information, the saturation to be output is calculated from the input c signal, and the c signal resulting from the calculation is output to the coordinate signal conversion unit 124.

The operation of the saturation calculator 123 in the above configuration will be described. The saturation calculator 123 is controlled by a function g (·) that defines an input / output relationship, and a relationship of cout = g (cin) is provided between the input c signal cin and the output c signal cout. Stand up. g (·) is defined using a cubic function, and is controlled so that the following condition is satisfied. g (•) is [0, Cmax_monitor] g (0) = 0 g (Cmax_monitor) = Cmax_printer g '(0) = α g' (Cmax_monitor) = γ, γ: γ> 0 g '(x) ≠ 0, x: 0 ≦ x ≦ Cmax_monitor

Here, α is determined by the output value of the storage unit 625, that is, the saturation adjustment value in the hue determined from the h signal. Cmax_monitor is calculated from the h signal, which is a hue component, and monitor color gamut information, and is defined as the maximum chroma value of the monitor color gamut at the hue determined from the h signal. Cmax_printer is calculated from the h signal, which is a hue component, and printer gamut information, and is defined as the maximum saturation value of the printer gamut at the hue determined from the h signal.

Γ is a value for controlling the compression ratio of the saturation compression in the vicinity of the maximum saturation. Under the restriction that the above condition is satisfied, the saturation calculation unit 123 automatically determines the relationship between Cmax_monitor and Cmax_monitor. In the automatic setting of the γ parameter, the value of γ decreases as Cmax_monitor / Cmax_printer increases. That is, the compression ratio increases.

Saturation Adjustment Information The user inputs the saturation y at x = 0 of the saturation control function for one or more arbitrary hues as the saturation adjustment information. The storage unit 625 performs linear interpolation on the angle,
Create saturation adjustment information for all hues. This information is formed as a set of each hue and the saturation adjustment value α for each hue. This set information is stored in the storage unit 625 as saturation adjustment information.

The user inputs the gradient y at x = 0 of the saturation control function at an arbitrary hue as the saturation adjustment information, which means that the ideal saturation after the gamut compression at the specified saturation is calculated from the original saturation. Equal to y times the saturation of
Intuitive saturation adjustment is made very easy.

[0114]

[Eighth Embodiment] Hereinafter, a signal processing apparatus according to an eighth embodiment of the present invention will be described. Note that, in the present embodiment,
For configurations substantially similar to the first, third and fourth embodiments,
The same reference numerals are given and the detailed description is omitted.

This embodiment is a modification of the configuration of the saturation compression section 104 in the fourth embodiment. FIG. 18 is a block diagram illustrating a configuration example of the color signal converter 208 according to the present embodiment.

The brightness adjustment information input section 718 is for the user to input brightness adjustment information.
, A control panel formed as a user interface image on the color monitor 207, a keyboard 211 and / or a mouse 212, and the like. The brightness adjustment information input by the user giving the input value and the output value at each node is converted into an appropriate data structure by the CPU 201, and then temporarily changed to the main memory 20.
After being held at 2, the signal is input to the brightness compression unit 103 of the color signal converter 208 via the terminal 717. The input of the brightness adjustment information is not an essential operation.

Upon receiving an instruction to output the image held in the main memory 202 from the printer 209, the CPU 201 checks the stored contents of the main memory 202 to determine whether or not brightness adjustment information has been input, and transmits the presence / absence information to a color signal. Send to converter 208. When the brightness adjustment information is input, the CPU 201 sends the brightness adjustment information held in the main memory 202 to the color signal converter 208 via the PCI bus 214 and the terminal 717.

The brightness compression section 103 is input according to brightness range information extracted from monitor color gamut information and printer color gamut information, a predetermined compression relationship, and an input / output relationship determined from input brightness adjustment information. The L signal is lightness-compressed, and the L signal as a result of the compression is output to the color signal synthesis unit 105.

Lightness Compression Unit The brightness compression unit 103 is controlled by a function f (·) that defines an input / output relationship. That is, between the L signal Lin input to the brightness compression unit 103 and the L signal Lout output, Lout = f
(Lin). f (•) is defined using a piecewise function consisting of n-1 segments, and is controlled so that the following condition is satisfied. Incidentally, n is the number of nodes of the piecewise function, and is controlled by an input from the brightness adjustment information input unit 718 in the present embodiment. f (・) is [Lmin_monitor, Lmax_monitor], and f (・) is continuous at all points f (Lmin_monitor) = Lmin_printer f (Lmax_monitor) = Lmax_printer f '(Lmin_monitor) = α, α: 0 ≦ α f '(Lmax_monitor) = β, β: 0 ≦ β f (mi) = ni, i: 0 ≦ i ≦ n-2, mi: Lmin_monitor <mi <
Lmax_monitor, ni: Lmin_printer <ni <Lmax_printer f '(mi) = γi, i: 0 ≦ i ≦ n-2, mi: Lmin_monitor <mi <
Lmax_monitor f '(x) ≠ 0, x: Lmin_monitor <x <Lmax_monitor

Here, Lmin_monitor is the L value held by the black color of the monitor, and Lmax_monitor is L held by the white color of the monitor.
The value Lmin_printer is the L value held by the black color of the printer, and Lmax_printer is the L value held by the white color of the monitor. In the present embodiment, f (·) is set at least at each contact point.
This is realized by a cubic spline function that is C1 continuous. Here, α, β, the number of contacts n, mi, ni, and γi are set by the user when inputting the brightness adjustment information.
If there is no input of α, β or both, the algorithm automatically sets α, β or both. Also,
When there is no input of γi, γi is automatically obtained from the C2 continuity at the contact point i by an algorithm.

When no brightness adjustment information is input from the user, n = 5, mi = ni and γi = 1 are set, and α and β are automatically calculated under the above conditions. Set the approximate parameters to the function f (•).

In the automatic calculation algorithm for α and β, the value of α decreases as the difference between Lmin_monitor and Lmin_printer increases. That is, the compression ratio near the darkest point increases. On the other hand, Lmax_monitor
As the difference from Lmax_printer increases, the value of β decreases. That is, the compression ratio near the brightest point increases.

According to each of the embodiments described above, in gamut compression, medium brightness is preserved, and colors with very high brightness or colors with very low brightness are greatly compressed in brightness. Further, in gamut compression, the saturation is preserved for a color having a low saturation, and is conversely compressed for a color having a high saturation. As a result, it is possible to obtain an output image that is very similar perceptually irrespective of the difference in color reproducibility due to the difference in the model of the monitor or the printer, or the difference in color reproducibility due to the difference in the color reproduction characteristics of the recording medium. it can.

[0124]

[Other Embodiments] The present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), and can be applied to a single device (for example, a copying machine). Machine, facsimile machine, etc.).

Further, an object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiment to a system or an apparatus, and to provide a computer (or CPU or MPU) of the system or apparatus.
Needless to say, this can also be achieved by the PU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the OS running on the computer based on the instructions of the program code.
It goes without saying that an (operating system) performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

In each of the above embodiments, the description has been made with reference to the typical Lab color space. However, the present invention is not limited to this, and the lightness and chromaticity of the Luv color space, the Munsell color space, etc. Can be applied to any color space having

[0128]

As described above, according to the present invention,
A signal processing apparatus and method for converting a color signal so that colors formed and / or displayed on different devices and / or different recording media are perceived as similar colors can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration example of a color signal conversion device according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration example of a color signal converter shown in FIG. 1;

FIG. 3 is a diagram showing an example of an input / output relationship of brightness in the first embodiment;

FIG. 4 is a block diagram showing a configuration example of a saturation compression unit shown in FIG. 2;

FIG. 5 is a diagram showing an example of a relationship between input and output of saturation in the first embodiment;

FIG. 6 is a diagram showing lightness compression input / output characteristics when gamut compression is performed on a plurality of types of paper qualities;

FIG. 7 is a diagram illustrating an example of an input / output relationship of saturation in the second embodiment.

FIG. 8 is a block diagram illustrating a configuration example of a color signal converter according to a third embodiment;

FIG. 9 is a diagram showing an input / output relationship of lightness at a certain chromaticity ab;

FIG. 10 is a diagram showing an input / output relationship of lightness at a certain chromaticity ab;

FIG. 11 is a block diagram illustrating a configuration example of a color signal converter according to a fifth embodiment;

FIG. 12 is a block diagram illustrating a configuration example of a saturation compression unit illustrated in FIG. 11;

FIG. 13 is a flowchart showing the operation of the saturation calculator shown in FIG. 11;

FIG. 14 is a block diagram illustrating a configuration example of a color signal converter according to a sixth embodiment;

FIG. 15 is a block diagram illustrating a configuration example of a saturation compression unit illustrated in FIG. 14;

FIG. 16 is a block diagram illustrating a configuration example of a color signal converter according to a seventh embodiment;

FIG. 17 is a block diagram illustrating a configuration example of a saturation compression unit illustrated in FIG. 16;

FIG. 18 is a block diagram illustrating a configuration example of a color signal converter according to an eighth embodiment.

Continued on the front page F term (reference) 5B057 AA11 BA28 CA01 CA08 CA12 CB01 CB08 CB12 CB16 CC01 CE11 CE16 CE18 CG07 CH08 CH11 DC25 DC36 5C077 PP15 PP31 PP35 PQ12 PQ22 RR21 SS06 TT02 TT06 5C079 HB11 PA12 MA03

Claims (41)

[Claims] 1. A color signal in a first color gamut is converted to a color signal in a second color gamut different from the first color gamut by compressing the brightness with the chromaticity substantially constant. When the first lightness and the second color gamut are different from each other, the conversion means increases the compression ratio near the highest lightness, and the first and second color gamut. A signal processing device for increasing a compression ratio near the minimum brightness when the minimum brightnesses of the two are different from each other. 2. The signal processing apparatus according to claim 1, wherein the conversion unit has a characteristic of suppressing a change in a color signal value before and after conversion in a medium brightness region. 3. The signal processing apparatus according to claim 1, wherein a conversion characteristic of the conversion unit is substantially constant regardless of chromaticity. 4. The apparatus according to claim 1, wherein a conversion characteristic in a medium brightness area of said conversion means is kept substantially constant irrespective of characteristics of said first and second color reproduction areas. 4. The signal processing device according to claim 3. 5. The method according to claim 1, wherein the conversion characteristic of the conversion unit is realized using a piecewise function.
A signal processing device according to any one of the above. 6. The signal processing apparatus according to claim 5, wherein a continuous first-order or higher spline function is used as the piecewise function. 7. The signal processing apparatus according to claim 6, wherein a C2 continuous cubic spline function is used as the spline function. 8. The signal processing apparatus according to claim 6, wherein a C1 continuous cubic spline function is used as the spline function. 9. The apparatus according to claim 5, further comprising control means for controlling said conversion characteristic based on an input value and an output value of each node manually input.
A signal processing device according to any one of the above. 10. The apparatus further comprising: setting means for setting a continuous cubic or higher-order n-order spline function used as the piecewise function, wherein the setting means includes: an input / output value of each node manually input; 6. The signal processing device according to claim 5, wherein the n-th order spline function is set based on n-1 order continuity of a node. 11. Further, there is provided setting means for setting a continuous nth-order spline function of a fourth order or higher used as the piecewise function, wherein the setting means comprises an input / output value and a slope of each of the manually input nodes. 6. The signal processing device according to claim 5, wherein the n-th order spline function is set based on the continuity of an n-2 order of each node. 12. The signal processing apparatus according to claim 11, wherein the setting unit obtains the slope of the node for which the slope has not been input, from n-1 order continuity. 13. A color signal in the first color gamut is converted to a color signal in a second color gamut different from the first color gamut by compressing the lightness while keeping the chromaticity substantially constant. A signal processing method for converting, wherein the highest lightness of the first and second color reproduction areas is different from each other, the compression ratio near the highest lightness is increased, and the lowest lightness of the first and second color reproduction areas. Are different from each other, the compression ratio near the lowest brightness is increased. 14. A color signal in the first color gamut is converted to a color signal in a second color gamut different from the first color gamut by compressing the brightness with the chromaticity substantially constant. Conversion means for converting; and obtaining means for obtaining the highest lightness and the lowest lightness in the arbitrary chromaticity of the first and second color gamut, respectively, wherein the conversion means changes the conversion characteristic according to the chromaticity. Wherein the conversion characteristics at each chromaticity, if the highest lightness in the target chromaticity of the first and second color reproduction gamut is different from each other, the compression ratio near the highest lightness is large, the first and second A signal processing device, wherein when the minimum lightness in the target chromaticity of the color reproduction range is different from each other, the compression ratio near the minimum lightness is large. 15. The signal processing apparatus according to claim 14, wherein the conversion unit has a characteristic of suppressing a change in a color signal value before and after conversion in a medium brightness region. 16. The maximum lightness and the minimum lightness at an arbitrary chromaticity of the first and second color gamut are obtained, respectively, and the luminosity is compressed by making the chromaticity substantially constant based on the obtained maximum lightness and the minimum lightness. By doing so, a signal processing method for converting a color signal in the first color gamut into a color signal in a second color gamut different from the first color gamut, wherein the conversion characteristic in the conversion is It is characterized by being changed in accordance with chromaticity, the conversion characteristics in each chromaticity, if the highest lightness in the target chromaticity of the first and second color gamut is different from each other, the compression ratio near the highest lightness is large The signal processing method according to claim 1, wherein when the minimum lightness in the target chromaticity of the first and second color reproduction areas is different from each other, a compression ratio near the minimum lightness is large. 17. A color signal in the first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing the saturation while keeping the brightness and the hue substantially constant. A signal processing apparatus, comprising: conversion means for converting into a signal, wherein the conversion means increases a compression ratio near a maximum saturation. 18. The signal processing apparatus according to claim 17, wherein the conversion unit has a characteristic of suppressing a change in a color signal value before and after conversion in an achromatic color region to a medium saturation region. 19. The signal processing apparatus according to claim 17, wherein the conversion characteristic of the conversion unit is realized by using a function of third order or higher. 20. The signal processing apparatus according to claim 17, wherein the conversion characteristic of the conversion unit is realized using a piecewise function. 21. A continuous linear or higher order spline function is used for the piecewise function.
A signal processing device according to claim 1. 22. The spline function has C2 continuous or
22. The signal processing device according to claim 21, wherein a C1 continuous cubic spline function is used. 23. The signal processing apparatus according to claim 19, further comprising control means for controlling the conversion characteristic based on a manually input gradient at a saturation of zero. apparatus. 24. A color signal in the first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing the saturation while keeping the brightness and the hue substantially constant. A signal processing method for converting a signal into a signal, wherein a compression ratio near a maximum saturation is increased. 25. A color signal in the first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing the saturation while keeping the brightness and the hue substantially constant. Conversion means for converting into a signal, acquisition means for acquiring the maximum saturation in each hue of the first and second color gamut, and conversion characteristics from the two maximum saturations acquired for each hue. A signal processing device comprising: setting means for setting. 26. Compressing chroma with substantially constant lightness and hue to convert a color signal in a first color gamut into a color in a second color gamut different from the first color gamut. Conversion means for converting to a signal, acquisition means for acquiring the maximum saturation at an arbitrary hue and arbitrary lightness of the first and second color gamut, and for each hue, from the acquired two maximum saturations A signal processing device comprising: setting means for setting a conversion characteristic. 27. Compressing chroma with substantially constant brightness and hue to convert color signals in the first color gamut into colors in a second color gamut different from the first color gamut. A signal processing method for converting into a signal, wherein a maximum saturation in an arbitrary hue of the first and second color reproduction ranges is obtained, and a conversion characteristic is obtained from the obtained two maximum saturations for each hue. A signal processing method characterized by setting. 28. A color signal in a first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing chroma with substantially constant brightness and hue. A signal processing method for converting into a signal, wherein a maximum saturation at an arbitrary hue and an arbitrary brightness of the first and second color reproduction ranges is obtained, and for each hue, from the obtained two maximum saturations A signal processing method comprising setting conversion characteristics. 29. A color signal in the first color gamut is converted to a color signal in a second color gamut different from the first color gamut by compressing the lightness while keeping the chromaticity substantially constant. Conversion means for converting, compression means for obtaining a third color gamut obtained by applying lightness compression and saturation compression to the first color gamut, and at any chromaticity of the second and third color gamut A signal processing apparatus comprising: an acquisition unit that acquires a maximum lightness and a minimum lightness; and an adjustment unit that adjusts a lightness by making the chromaticity substantially constant from the four lightnesses acquired for each chromaticity. 30. The brightness adjustment by the adjusting means is performed linearly for each chromaticity based on the highest brightness in the second color gamut and the highest brightness and the lowest brightness in the third color gamut. 30. The signal processing device according to claim 29, wherein: 31. The lightness adjustment by the adjusting means includes, for each chromaticity, the highest lightness in the second color gamut and the highest lightness and the lowest lightness in the third color gamut.
30. The signal processing device according to claim 29, wherein the signal processing is performed nonlinearly so as to maintain the brightness of the third color gamut. 32. The signal processing apparatus according to claim 29, wherein the conversion characteristic of the conversion unit is realized using a piecewise function. 33. A continuous linear or higher-order spline function is used for the piecewise function.
A signal processing device according to claim 1. 34. The spline function has C2 continuous or
The signal processing device according to claim 33, wherein a C1 continuous cubic spline function is used. 35. A color signal in a first color gamut is converted to a color signal in a second color gamut different from the first color gamut by compressing the brightness with the chromaticity substantially constant. A signal processing method for converting, wherein a third color gamut obtained by applying lightness compression and saturation compression to the first color gamut is obtained, and the second and third color gamut at an arbitrary chromaticity. A signal processing method comprising acquiring a maximum lightness and a minimum lightness, respectively, and adjusting the lightness by making the chromaticity substantially constant from the four lightnesses obtained for each chromaticity. 36. A color signal in a first color gamut is converted into a color signal in a second color gamut different from the first color gamut by compressing the lightness while keeping the chromaticity substantially constant. A recording medium on which a program code of a signal processing to be converted is recorded, wherein the program code increases a compression ratio near a maximum brightness at least when the maximum brightness of the first and second color reproduction areas is different from each other. A recording medium comprising: a step code; and a step code for increasing a compression ratio near the minimum brightness when the first and second color reproduction areas have different minimum brightness. 37. A method for acquiring the highest lightness and the lowest lightness in the arbitrary chromaticities of the first and second color reproduction regions, respectively, and compressing the lightness by making the chromaticity substantially constant based on the obtained highest lightness and the lowest lightness. By doing so, the recording medium has recorded thereon a signal processing program code for converting a color signal in the first color gamut into a color signal in a second color gamut different from the first color gamut. The conversion characteristic in the conversion is characterized by being changed according to the chromaticity, the conversion characteristic in each chromaticity, when the highest brightness of the first and second color gamut is different from each other, near the highest brightness A recording medium characterized by having a high compression ratio and a high compression ratio near the minimum brightness when the first and second color reproduction areas have different minimum brightness. 38. A color signal in the first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing the saturation while keeping the brightness and the hue substantially constant. A recording medium on which is recorded a signal processing program code for converting into a signal, wherein the program code has at least a code for a step of increasing a compression ratio near a maximum saturation. 39. By compressing the saturation while keeping the brightness and the hue substantially constant, a color signal in the first color gamut is converted into a color signal in a second color gamut different from the first color gamut. A recording medium on which a program code for signal processing to be converted into a signal is recorded, and a code of a step of acquiring a maximum saturation in an arbitrary hue of the first and second color gamut, and for each hue, A code for setting a conversion characteristic from the two acquired maximum saturations. 40. A color signal in the first color gamut is converted into a color in a second color gamut different from the first color gamut by compressing the saturation while keeping the brightness and the hue substantially constant. A recording medium on which a program code of a signal processing to be converted into a signal is recorded, wherein a code of a step of obtaining a maximum saturation in an arbitrary hue and an arbitrary brightness of the first and second color reproduction regions, respectively, A code for setting a conversion characteristic from the two maximum saturations acquired for each of the recording mediums. 41. By compressing the lightness while keeping the chromaticity substantially constant, a color signal in the first color gamut is converted into a color signal in a second color gamut different from the first color gamut. A recording medium on which a program code of a signal processing to be converted is recorded, wherein a code of a step of obtaining a third color gamut obtained by applying brightness compression and saturation compression to the first color gamut; And a code for a step of obtaining the highest lightness and the lowest lightness in the arbitrary chromaticity of the third color reproduction range, and a step of adjusting the lightness by making the chromaticity substantially constant from the four lightnesses obtained for each chromaticity And a recording medium comprising: