# US 2016/0366386 A1 · Prevention of highlight clipping

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- Number: US 2016/0366386 A1
- Document ID: US20160366386A1
- Status: Published application
- Kind: A1
- Application number: 15/081,680
- Filed: 2016-03-25
- Published: 2016-12-15
- Earliest claimed: 2015-06-12
- Assignees: GoPro, Inc.
- Applicants: GoPro, Inc.
- Inventors: Bruno Cesar Douady-Pleven; Michael Serge André Kraak; Guillaume Matthieu Guerin; Thomas Nicolas Emmanuel Veit
- Web page: https://patentgrep.com/patent/US20160366386A1

## CPC

- G06T 3/4015: Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
- G06T 5/40: using histogram techniques
- G06T 5/50: using two or more images, e.g. averaging or subtraction
- G06T 5/70: Denoising; Smoothing
- G06T 5/75: Unsharp masking
- G06T 5/92: based on global image properties
- G06T 5/94: based on local image properties, e.g. for local contrast enhancement
- H04N 5/213: Circuitry for suppressing or minimising impulsive noise (for suppressing or minimising disturbance in image signal generation H04N23/81)
- H04N 9/646: {for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters}
- H04N 9/77: Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase (circuits for matrixing H04N9/67)
- H04N 23/741: by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
- H04N 23/81: for suppressing or minimising disturbance in the image signal generation
- H04N 25/618: for random or high-frequency noise
- H04N 25/626: Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
- H04N 25/633: by using optical black pixels
- H04N 25/672: between adjacent sensors or output registers for reading a single image
- H04N 25/674: based on the scene itself, e.g. defocusing
- G06T 2207/10016: Video; Image sequence
- G06T 2207/10024: Color image
- G06T 2207/20182: Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
- H04N 23/88: for colour balance, e.g. white-balance circuits or colour temperature control
- H04N 2209/046: Colour interpolation to calculate the missing colour values
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A system determines for each color channel of each portion of the image, a corresponding adjustment value to apply to the color channel to correct for a color irregularity. The system determines a corrected adjustment value based on a difference between twice the pixel value and the maximum saturation value. If the adjustment value as applied is larger than the corrected adjustment value, the system applies the adjustment value to the corresponding color channel of the image portion to produce the adjusted color channel. Otherwise, the system applies the corrected adjustment to the corresponding color channel of the image portion to produce an adjusted color channel. The system generates a modified image based on the adjusted color channel.

## Claims

### Claim 1

A method for processing an image captured by a camera comprising:
accessing an image from an image sensor;
determining, for each color channel of each portion of the image, a corresponding adjustment value to apply to the color channel to correct for a color irregularity, each color channel comprising a set of pixels each with a pixel value between zero and a maximum saturation value;
determining a corrected adjustment value based on a difference between twice the pixel value and the maximum saturation value;
in response to a determination that the adjustment value as applied is larger than the corrected adjustment value, applying the adjustment value to the corresponding color channel of the image portion to produce the adjusted color channel;
in response to a determination that the adjustment value as applied is larger than the corrected adjustment value, applying the corrected adjustment to the corresponding color channel of the image portion to produce an adjusted color channel; and
generating a modified image based on the adjusted color channel.

### Claim 2 (depends on 1)

The method of claim 1, wherein the color irregularity is a white balance error, and the adjustment value is to be applied uniformly to all image portions of the image.

### Claim 3 (depends on 1)

The method of claim 1, wherein the color irregularity is a lens shading error, and the adjustment value is to be applied to image portions of the image affected by the lens shading error.

### Claim 4 (depends on 1)

The method of claim 1, wherein the adjustment value to be applied is the same for each color channel of one or more of the image portion.

### Claim 5 (depends on 1)

The method of claim 1, further comprising prior to the determining the corresponding adjustment value:
identifying a gain value for the image to increase the luminance of the image;
applying the gain value to each color channel of the image;
determining that one or more pixel values of one or more of the color channels is to be decreased to correct for the color irregularity; and
determining that at least one pixel value of one of the color channels has reached a maximum saturation value due to the application of the gain value.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
identifying a gain value for the image to increase the luminance of the image;
applying the gain value to each color channel of the image by:
determining a continuously variable adjusted gain value based on the gain value and dependent upon an input pixel value of each color channel of the image, such that input pixel values that are nearer a zero value have an adjusted gain value nearing the gain value, and the input pixel values that are nearer the maximum saturation value have an adjusted gain value that when applied to the pixel value does not cause the pixel value to reach the maximum saturation value; and
applying the continuously variable adjusted gain value to the input pixel values of one or more of the color channels of the image.

### Claim 7 (depends on 1)

The method of claim 1, wherein applying the adjustment value to the corresponding color channel of the image portion further comprises:
determining one or more adjusted pixel values of the adjusted color channel by multiplying the one or more pixel values of the corresponding color channel by the adjustment value.

### Claim 8 (depends on 1)

The method of claim 1, wherein applying the adjustment value to the corresponding color channel of the image portion further comprises:
determining one or more adjusted pixel values of the adjusted color channel by multiplying the one or more pixel values of the corresponding color channel by the corrected adjustment value, the corrected adjustment value equal to twice the value of the one or more pixel values of the corresponding color channel subtracted by the maximum saturation value.

### Claim 9 (depends on 1)

The method of claim 1, wherein the application of the corrected adjustment value prevents a presentation of an unnatural color when one or more color channels of one or more of the image portions is desaturated to correct for the color irregularity.

### Claim 10

A specially-configured hardware system configured to:
access an image from an image sensor;
determine, for each color channel of each portion of the image, a corresponding adjustment value to apply to the color channel to correct for a color irregularity, each color channel comprising a set of pixels each with a pixel value between zero and a maximum saturation value;
determine a corrected adjustment value based on a difference between twice the pixel value and the maximum saturation value;
in response to a determination that the adjustment value as applied is larger than the corrected adjustment value, apply the adjustment value to the corresponding color channel of the image portion to produce the adjusted color channel;
in response to a determination that the adjustment value as applied is larger than the corrected adjustment value, apply the corrected adjustment to the corresponding color channel of the image portion to produce an adjusted color channel; and
generate a modified image based on the adjusted color channel.

### Claim 11 (depends on 10)

The specially-configured hardware system of claim 10, wherein the color irregularity is a white balance error, and the adjustment value is to be applied uniformly to all image portions of the image.

### Claim 12 (depends on 10)

The specially-configured hardware system of claim 10, wherein the color irregularity is a lens shading error, and the adjustment value is to be applied to image portions of the image affected by the lens shading error.

### Claim 13 (depends on 10)

The specially-configured hardware system of claim 10, wherein the adjustment value to be applied is the same for each color channel of one or more of the image portion.

### Claim 14 (depends on 10)

The specially-configured hardware system of claim 10, further configured to:
identify a gain value for the image to increase the luminance of the image;
apply the gain value to each color channel of the image;
determine that one or more pixel values of one or more of the color channels is to be decreased to correct for the color irregularity; and
determine that at least one pixel value of one of the color channels has reached a maximum saturation value due to the application of the gain value.

### Claim 15 (depends on 10)

The specially-configured hardware system of claim 10, further configured to:
identify a gain value for the image to increase the luminance of the image;
apply the gain value to each color channel of the image by:
determine a continuously variable adjusted gain value based on the gain value and dependent upon an input pixel value of each color channel of the image, such that input pixel values that are nearer a zero value have an adjusted gain value nearing the gain value, and the input pixel values that are nearer the maximum saturation value have an adjusted gain value that when applied to the pixel value does not cause the pixel value to reach the maximum saturation value; and
apply the continuously variable adjusted gain value to the input pixel values of one or more of the color channels of the image.

### Claim 16 (depends on 10)

The specially-configured hardware system of claim 10, further configured to:
determine one or more adjusted pixel values of the adjusted color channel by multiplying the one or more pixel values of the corresponding color channel by the adjustment value.

### Claim 17 (depends on 10)

The specially-configured hardware system of claim 10, further configured to:
determine one or more adjusted pixel values of the adjusted color channel by multiplying the one or more pixel values of the corresponding color channel by the corrected adjustment value, the corrected adjustment value equal to twice the value of the one or more pixel values of the corresponding color channel subtracted by the maximum saturation value.

### Claim 18 (depends on 10)

The specially-configured hardware system of claim 10, wherein the application of the corrected adjustment value prevents a presentation of an unnatural color when one or more color channels of one or more of the image portions is desaturated to correct for the color irregularity.