# US 9,438,770 B2 · Color image conversion using chroma

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- Number: US 9,438,770 B2
- Document ID: US9438770B2
- Status: Granted
- Kind: B2
- Application number: 14/408,973
- Filed: 2012-07-24
- Published: 2015-08-20
- Granted: 2016-09-06
- Earliest claimed: 2012-07-24
- Assignees: Hewlett-Packard Development Company, L.P.
- Applicants: Marti Maria Saguer; Laura Alicia Clemente Gomez
- Inventors: Marti Maria Saguer; Laura Alicia Clemente Gomez
- Web page: https://patentgrep.com/patent/US9438770B2

## CPC

- H04N 1/6016: {Conversion to subtractive colour signals}
- H04N 1/40012: {Conversion of colour to monochrome}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

In one example, a color image is converted to a gray image and/or a black and white image. The amount of chroma in an input image is detected and conversion to gray and/or black and white of the input image is computed simultaneously.

## Claims

### Claim 1

A method of converting a color image to a gray image and/or a black and white image, the method comprising, simultaneously:
detecting the amount of chroma in an input image;
computing conversion to gray and/or black and white of the input image; and
converting a plurality of elements of an input image into International Color Consortium Profile Connection Space (ICC PCS);
wherein the detection of the amount of chroma in an input image comprises detecting the amount of chroma of each element of the converted image; and
wherein the computation of the conversion to gray and/or black and white comprises computing conversion to gray and/or black and white of the converted image.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the detection of the amount of chroma of each element of the converted image comprises:
determining which pixel of the converted image has chroma and which has no chroma;
determining the amount of chroma for each pixel determined as having chroma.

### Claim 3 (depends on 2)

A method according to claim 2, wherein the determination of which pixel of the converted image has chroma and which has no chroma comprises:
using a*/b* axis of the ICC profile of the converted image to determine which pixel of the converted image has chroma and which has no chroma.

### Claim 4 (depends on 3)

A method according to claim 3, wherein the method further comprises:
outputting a function of the amount of chroma on a first output channel.

### Claim 5 (depends on 1)

A method according to claim 1, wherein the computation of the conversion to gray of the converted image comprises
deriving a greyscale representation of the input image.

### Claim 6 (depends on 5)

A method according to claim 5, wherein the method further comprises:
outputting the greyscale representation of the input image on a second output channel.

### Claim 7 (depends on 1)

A method according to claim 1, wherein the computation of black and white of the converted image comprises
applying a step function to the converted image; and
obtaining a pure black and white rendering of the applied, converted image.

### Claim 8 (depends on 7)

A method according to claim 7, wherein the method further comprises:
outputting the pure black and white rendering of the input image on a third output channel.

### Claim 9

An apparatus for converting a color image to a gray image and/or a black and white image, the apparatus comprising
a detector configured to detect the amount of chroma in an input image;
a processor configured to compute conversion to gray and/or black and white of the input image, and
a first output channel configured to output a function of the amount of chroma;
wherein the detector and processor are in parallel such that detecting the amount of chroma in an input image and computing conversion to gray and/or black and white of the input image are performed simultaneously; and
wherein the apparatus further comprises a third output channel configured to output the pure black and white rendering of the input image, wherein the third output channel is parallel with respect to the first output channel.

### Claim 10 (depends on 9)

The apparatus according to claim 9, wherein the apparatus further comprises
a converter configured to convert a plurality of elements of an input image into International Color Consortium Profile Connection Space (ICC PCS); and
wherein the output of the converted is in communication with the input of the detector and processor.

### Claim 11

The apparatus according to 9, wherein the apparatus further comprises a second output channel configured to output the greyscale representation of the input image, wherein the second output channel is parallel with respect to the first output channel.

### Claim 12

The apparatus according to 11, wherein the apparatus further comprises a third output channel configured to output the pure black and white rendering of the input image, wherein the third output channel is parallel with respect to the first and second output channels.

### Claim 13

An apparatus for converting a color image to a gray image and/or a black and white image, the apparatus comprising:
a detector configured to detect the amount of chroma in an input image;
a processor configured to compute conversion to gray and/or black and white of the input image, and
a converter configured to convert a plurality of elements of an input image into International Color Consortium Profile Connection Space (ICC PCS);
wherein the detector and processor are in parallel such that the detection of the amount of chroma in an input image and the computing conversion to gray and/or black and white of the input image are performed simultaneously;
wherein the detection of the amount of chroma in an input image comprises detecting the amount of chroma of each element of the converted image; and
wherein the computation of the conversion to gray and/or black and white comprises computing conversion to gray and/or black and white of the converted image.