# US 7,609,413 B1 · Color management for limited gamut devices

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- Number: US 7,609,413 B1
- Document ID: US7609413B1
- Status: Granted
- Kind: B1
- Application number: 10/138,363
- Filed: 2002-05-02
- Granted: 2009-10-27
- Earliest claimed: 2002-05-02
- Assignees: Apple Inc.
- Inventors: Gabriel Marcu; Steve Swen; Luke Stanislaw Wallis
- Web page: https://patentgrep.com/patent/US7609413B1

## CPC

- G09G 5/02: characterised by the way in which colour is displayed {(details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607)}
- H04N 1/6058: {Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut}
- G09G 5/06: using colour palettes, e.g. look-up tables
- G09G 2340/06: Colour space transformation
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Methods and apparatuses for performing color manipulation using virtual gamuts. In one aspect of the invention, a method to perform color manipulation on a digital processing system includes: performing color manipulation using a virtual gamut of a device if a real gamut of the device is poor in quality. When the real gamut of the device is wide, color manipulations are performed using the real gamut of the device. In one example according to this aspect, whether or not the real gamut of the device is poor in quality is determined by comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram. A virtual profile of the device specifies the virtual gamut of the device.

## Claims

### Claim 1

A method to perform color manipulation on a digital processing system, the method comprising:
maintaining one or more color profiles for a device having a real gamut, each color profile specifying one gamut for the device;
determining a virtual gamut for the device from the one or more color profiles maintained, wherein the virtual gamut is substituted for the real gamut for the device if the real gamut is poor in quality; and
generating color data to control the device using a color profile specifying the virtual gamut, wherein the generation of the color data is independent of the real gamut of the device.

### Claim 2 (depends on 1)

A method as in claim 1 further comprising:
determining whether or not the real gamut of the device is poor in quality.

### Claim 3 (depends on 2)

A method as in claim 2 wherein said determining whether or not the real gamut is poor in quality comprises:
comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 4 (depends on 1)

A method as in claim 1 wherein the color profile is a virtual profile of the device which specifies the virtual gamut of the device; and wherein the generation of color data includes color manipulation comprises color management; and wherein said color management comprises at least one of:
a) converting a color representation in a device dependent color space to a corresponding color representation in a device independent color space; and
b) converting a color representation in a device independent color space to a corresponding color representation in another device's dependent color space.

### Claim 5 (depends on 1)

A method as in claim 1 further comprising:
defining the virtual gamut of the device.

### Claim 6 (depends on 5)

A method as in claim 5 further comprising:
generating a virtual profile of the device to specify the virtual gamut.

### Claim 7 (depends on 5)

A method as in claim 5 wherein said defining the virtual gamut comprises:
determining the virtual gamut from an interpolation using the real gamut, threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 8 (depends on 7)

A method as in claim 7 wherein the threshold gamut is the same as the limit gamut.

### Claim 9 (depends on 5)

A method as in claim 5 wherein said defining the virtual gamut comprises:
determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 10 (depends on 9)

A method as in claim 9 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 11 (depends on 9)

A method as in claim 9 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 12 (depends on 7)

A method as in claim 7 wherein one of the threshold gamut and the limit gamut is determined from a real gamut of a destination device in the chromaticity diagram.

### Claim 13

A method to prepare data for performing color manipulation on a digital processing system, the method comprising:
determining whether or not a real gamut of a device is poor in quality;
defining a virtual gamut of the device if a real gamut of the device is poor in quality;
storing a color profile specifying the virtual gamut for the device; and
generating color data to control the device using the color profile, wherein the generation of the color data is independent of the real gamut of the device, and wherein the virtual gamut substitutes for the poor quality real gamut during subsequent color manipulation.

### Claim 14 (depends on 13)

A method as in claim 13 wherein said determining whether or not the real gamut is poor in quality comprises:
comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 15 (depends on 13)

A method as in claim 13 further comprising:
generating a virtual profile of the device to specify the virtual gamut.

### Claim 16 (depends on 13)

A method as in claim 13 wherein said defining the virtual gamut comprises:
determining the virtual gamut from an interpolation using the real gamut, a threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 17 (depends on 16)

A method as in claim 16 wherein the threshold gamut is the same as the limit gamut.

### Claim 18 (depends on 13)

A method as in claim 13 wherein said defining the virtual gamut comprises:
determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 19 (depends on 18)

A method as in claim 18 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 20 (depends on 18)

A method as in claim 18 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 21

A computer readable medium containing profile data of a device for performing color manipulation on a digital processing system, said profile data produced by a method comprising:
determining whether or not a real gamut of the device is poor in quality;
computing a virtual gamut of the device from an interpolation using a threshold gamut and a limit gamut in a chromaticity diagram after a determination that the real gamut of the device is poor in quality; and
storing a color profile specifying the virtual gamut for the device; and
generating color data to control the device using the color profile, wherein the generation of the color data is independent of the real gamut of the device, and wherein the virtual gamut substitutes for the poor quality real gamut during subsequent color manipulation.

### Claim 22 (depends on 21)

A computer readable medium as in claim 21 wherein said determining whether or not the real gamut is poor in quality comprises:
comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 23 (depends on 21)

A computer readable medium as in claim 21 wherein the threshold gamut is the same as the limit gamut.

### Claim 24 (depends on 21)

A computer readable medium as in claim 21 wherein said computing the virtual gamut comprises:
determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 25 (depends on 24)

A computer readable medium as in claim 24 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 26 (depends on 24)

A computer readable medium as in claim 24 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 27

A computer readable medium containing executable computer program instructions which when executed by a digital processing system cause said system to perform a method for color manipulation, the method comprising:
maintaining one or more color profiles for a device having a real gamut, each color profile specifying one gamut for the device;
determining a virtual gamut for the device from the one or more color profiles maintained, wherein the virtual gamut is substituted for the real gamut for the device if the real gamut is poor in quality; and
generating color data to control the device using a color profile specifying the virtual gamut, wherein the generation of the color data is independent of the real gamut of the device.

### Claim 28 (depends on 27)

A computer readable medium as in claim 27 wherein the method further comprises:
determining whether or not the real gamut of the device is poor in quality.

### Claim 29 (depends on 28)

A computer readable medium as in claim 28 wherein said determining whether or not the real gamut is poor in quality comprises:
comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 30 (depends on 27)

A computer readable medium as in claim 27 wherein the color profile is a virtual profile of the device which specifies the virtual gamut of the device; and wherein the generation of color data includes color manipulation comprises color management; and wherein said color management
comprises at least one of:
a) converting a color representation in a device dependent color space to a corresponding color representation in a device independent color space; and
b) converting a color representation in a device independent color space to a corresponding color representation in another device's dependent color space.

### Claim 31 (depends on 27)

A computer readable medium as in claim 27 wherein the method further comprises:
defining the virtual gamut of the device.

### Claim 32 (depends on 31)

A computer readable medium as in claim 31 wherein the method further comprises:
generating a virtual profile of the device to specify the virtual gamut.

### Claim 33 (depends on 31)

A computer readable medium as in claim 31 wherein said defining the virtual gamut comprises:
determining the virtual gamut from an interpolation using a threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 34 (depends on 33)

A computer readable medium as in claim 33 wherein the threshold gamut is the same as the limit gamut.

### Claim 35 (depends on 31)

A computer readable medium as in claim 31 wherein said defining the virtual gamut comprises:
determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 36 (depends on 35)

A computer readable medium as in claim 35 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 37 (depends on 35)

A computer readable medium as in claim 35 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 38 (depends on 33)

A computer readable medium as in claim 33 wherein one of the threshold gamut and the limit gamut is determined from a real gamut of a destination device in the chromaticity diagram.

### Claim 39

A computer readable medium containing executable computer program instructions which when executed by a digital processing system cause said system to perform a method to prepare data for performing color manipulation, the method comprising:
determining whether or not a real gamut of a device is poor in quality; and
defining a virtual gamut of the device if a real gamut of the device is poor in quality; and
storing a color profile specifying the virtual gamut for the device; and
generating color data to control the device using the color profile, wherein the generation of the color data is independent of the real gamut of the device, and wherein the virtual gamut substitutes for the poor quality real gamut during subsequent color manipulation.

### Claim 40 (depends on 39)

A computer readable medium as in claim 39 wherein said determining whether or not the real gamut is poor in quality comprises:
comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 41 (depends on 39)

A computer readable medium as in claim 39 wherein the method further comprises:
generating a virtual profile of the device to specify the virtual gamut.

### Claim 42 (depends on 39)

A computer readable medium as in claim 39 wherein said defining the virtual gamut comprises:
determining the virtual gamut from an interpolation using a threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 43 (depends on 42)

A computer readable medium as in claim 42 wherein the threshold gamut is the same as the limit gamut.

### Claim 44 (depends on 39)

A computer readable medium as in claim 39 wherein said defining the virtual gamut comprises:
determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 45 (depends on 44)

A computer readable medium as in claim 44 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 46 (depends on 44)

A computer readable medium as in claim 44 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 47

A digital processing system for color manipulation, the digital processing system comprising:
means for maintaining one or more color profiles for a device having a real gamut, each color profile specifying one gamut for the device;
means for determining a virtual gamut for the device from the one or more color profiles maintained, wherein the virtual gamut is substituted for the real gamut for the device if the real gamut is poor in quality; and
means for generating color data to control the device using a color profile specifying the virtual gamut, wherein the generation of the color data is independent of the real gamut of the device.

### Claim 48 (depends on 47)

A digital processing system as in claim 47 further comprising:
means for determining whether or not the real gamut of the device is poor in quality.

### Claim 49 (depends on 48)

A digital processing system as in claim 48 wherein said means for determining whether or not the real gamut is poor in quality comprises:
means for comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 50 (depends on 47)

A digital processing system as in claim 47 wherein the color profile is a virtual profile of the device which specifies the virtual gamut of the device; and wherein the generation of color data includes color manipulation comprises color management; and wherein said color management comprises at least one of:
a) converting a color representation in a device dependent color space to a corresponding color representation in a device independent color space; and
b) converting a color representation in a device independent color space to a corresponding color representation in another device's dependent color space.

### Claim 51 (depends on 47)

A digital processing system as in claim 47 further comprising:
means for defining the virtual gamut of the device.

### Claim 52 (depends on 51)

A digital processing system as in claim 51 further comprising:
means for generating a virtual profile of the device to specify the virtual gamut.

### Claim 53 (depends on 51)

A digital processing system as in claim 51 wherein said means for defining the virtual gamut comprises:
means for determining the virtual gamut from an interpolation using a threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 54 (depends on 53)

A digital processing system as in claim 53 wherein the threshold gamut is the same as the limit gamut.

### Claim 55 (depends on 51)

A digital processing system as in claim 51 wherein said means for defining the virtual gamut comprises:
means for determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 56 (depends on 55)

A digital processing system as in claim 55 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 57 (depends on 55)

A digital processing system as in claim 55 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.

### Claim 58 (depends on 53)

A digital processing system as in claim 53 wherein one of the threshold gamut and the limit gamut is determined from a real gamut of a destination device in the chromaticity diagram.

### Claim 59

A digital processing system method to prepare data for performing color manipulation, the digital processing system comprising:
means for determining whether or not a real gamut of a device is poor in quality;
means for defining a virtual gamut of the device if a real gamut of the device is poor in quality; and
means for storing a color profile specifying the virtual gamut for the device; and
means for generating color data to control the device using the color profile, wherein the generation of the color data is independent of the real gamut of the device, and wherein the virtual gamut substitutes for the poor quality real gamut during subsequent color manipulation.

### Claim 60 (depends on 59)

A digital processing system as in claim 59 wherein said means for determining whether or not the real gamut is poor in quality comprises:
means for comparing an area of the real gamut with a threshold gamut area in a chromaticity diagram.

### Claim 61 (depends on 59)

A digital processing system as in claim 59 further comprising:
means for generating a virtual profile of the device to specify the virtual gamut.

### Claim 62 (depends on 59)

A digital processing system as in claim 59 wherein said means for defining the virtual gamut comprises:
means for determining the virtual gamut from an interpolation using a threshold gamut and a limit gamut in a chromaticity diagram.

### Claim 63 (depends on 62)

A digital processing system as in claim 62 wherein the threshold gamut is the same as the limit gamut.

### Claim 64 (depends on 59)

A digital processing system as in claim 59 wherein said means for defining the virtual gamut comprises:
means for determining an area of the virtual gamut from an area of the real gamut, an area of a threshold gamut and an area of a limit gamut.

### Claim 65 (depends on 64)

A digital processing system as in claim 64 wherein the area of the virtual gamut increases as the area of the real gamut increases; and wherein the area of the virtual gamut is larger than the area of the real gamut, larger than the area of the limit gamut, and smaller than the area of the threshold gamut.

### Claim 66 (depends on 64)

A digital processing system as in claim 64 wherein a primary of the virtual gamut and a corresponding primary of the real gamut are on a hue locus; and a saturation of the primary of the virtual gamut is larger than a saturation of the corresponding primary of the real gamut.