# US 2022/0044615 A1 · Display mapping for high dynamic range images on power-limiting displays

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- Number: US 2022/0044615 A1
- Document ID: US20220044615A1
- Status: Published application
- Kind: A1
- Application number: 17/276,752
- Filed: 2019-09-17
- Published: 2022-02-10
- Earliest claimed: 2018-09-17
- Assignees: Dolby Laboratories Licensing Corporation
- Applicants: Dolby Laboratories Licensing Corporation
- Inventors: Jaclyn Anne Pytlarz
- Web page: https://patentgrep.com/patent/US20220044615A1

## CPC

- G09G 3/2007: {Display of intermediate tones}
- G06T 5/92: based on global image properties
- G09G 5/005: {Adapting incoming signals to the display format of the display terminal}
- G09G 5/10: Intensity circuits
- G06T 2207/20208: High dynamic range [HDR] image processing
- G09G 2320/0626: for control of overall brightness
- G09G 2320/0666: for control of colour parameters, e.g. colour temperature
- G09G 2320/0673: for control of gamma adjustment, e.g. selecting another gamma curve
- G09G 2330/021: Power management, e.g. power saving
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- 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)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

Methods and systems for mapping images from a first dynamic range to a second dynamic on a target display with power limitations are described. Given: an input image in a first dynamic range, input metadata (Smin, Smid, Smax), power-independent luminance characteristics of a target display (Tmin, reference Tmax), and an APL function of the target display, wherein the APL function determines output luminance in the target display as a function of average picture level (APL) input in the target display, a processor generates an adaptive output of the maximum luminance level for the target display (Tmax) so that when mapping the image from the first dynamic range to the second dynamic range, the anchor points of the tone-mapping function are adjusted according to the APL function of the target display.

## Claims

### Claim 1

A method for generating a display-mapped image using a tone-mapping curve with a first anchor point and a second anchor point, the method comprising:
receiving input metadata for an input image to be mapped on a target display from a first dynamic range to a second dynamic range using the tone-mapping curve, wherein the input metadata comprise a minimum luminance pixel value of the input image Smin, a medium or average luminance pixel value of the input image Smid, and a maximum luminance pixel value of the input image Smax;
receiving an average picture level (APL) function of the target display, wherein the APL function determines output luminance in the target display as a function of APL input in the target display;
receiving a minimum luminance level for the target display Tmin and a reference maximum luminance level for the target display Tmax_ref;
determining a reference mid luminance level for the target display Tmid_ref by mapping Smid from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax_ref as the second anchor point;
determining a luminance versus candidate maximum luminance level (Tmax_c) function of the target display as the output of the APL function for an APL input corresponding to a mid luminance level of the target display Tmid determined by mapping Smid from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax_c as the second anchor point;
determining an output maximum luminance level of the target display Tmax based on a Tmax_c value for which the output of the luminance versus Tmax_c function is closer to the reference mid luminance level of the target display Tmid_ref; and
mapping the input image from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax as the second anchor point.

### Claim 2 (depends on 1)

The method of claim 1, wherein determining the reference mid luminance level for the target display comprises:
generating a mid-reference PQ luminance value for the target display based on the medium or average luminance pixel value of the input image, the minimum luminance level for the target display, and the reference maximum luminance level for the target display; and
converting the mid reference PQ luminance to a linear mid luminance level by using a PQ-to-linear luminance mapping function.

### Claim 3 (depends on 1)

The method of claim 1, wherein determining the luminance versus Tmax_c function for the target display comprises:
determining a set of two or more candidate maximum luminance values;
for a candidate maximum luminance value (Tmax_c(i)) in the set of candidate maximum luminance values:
generating a candidate mid luminance value for the target display based on the medium or average luminance pixel value of the input image, the minimum luminance level for the target display and the candidate maximum luminance value; and
generating a luminance for the Tmax_c(i) value based on the candidate mid luminance value and the APL function of the target display.

### Claim 4

A method for generating a display-mapped image using a tone-mapping curve with a first anchor point and a second anchor point, the method comprising:
receiving input metadata for an input image to be mapped on a target display from a first dynamic range to a second dynamic range using the tone-mapping curve, wherein the input metadata comprise a minimum luminance pixel value of the input image Smin, a medium or average luminance pixel value of the input image Smid, and a maximum luminance pixel value of the input image Smax;
receiving an average picture level (APL) function of the target display, wherein the APL function determines output luminance in the target display as a function of APL input in the target display;
receiving a minimum luminance level for the target display Tmin and a reference maximum luminance level for the target display Tmax_ref;
determining a reference mid luminance level for the target display Tmid_ref by mapping Smid from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax_ref as the second anchor point;
determining a luminance versus candidate power factor (P_c) function of the target display as the output of the APL function for an APL input corresponding to a mid luminance level of the target display Tmid determined by mapping Smid from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax_ref as the second anchor point, with Tmid adjusted using the candidate power factor P_c;
determining an output power factor for the target display P based on a P_c value for which the output of the luminance versus P_c function is closer to the reference mid luminance level of the target display Tmid_ref; and
mapping the input image from the first dynamic range to the second dynamic range using the tone-mapping curve with Smin, Tmin as the first anchor point and Smax, Tmax_ref as the second anchor point, with the tone-mapping curve adjusted using the output power factor P.

### Claim 5 (depends on 4)

The method of claim 4, wherein determining the reference mid luminance level for the target display comprises:
generating a mid reference PQ luminance value for the target display based on the medium or average luminance pixel value of the input image, the minimum luminance level for the target display, and the reference maximum luminance level for the target display; and
converting the mid reference PQ luminance to a linear mid luminance level by using a PQ-to-linear luminance mapping function.

### Claim 6 (depends on 4)

The method of claim 4, wherein determining the luminance vs P_c function for the target display comprises:
determining a set of two or more candidate power factor values;
for a candidate power factor value (P_c(i)) in the set of candidate power factor values:
generating a candidate mid luminance value for the target display based on the medium or average luminance pixel value of the input image, the minimum luminance level for the target display, the maximum luminance level, and the candidate power factor value; and
generating a luminance for the P_c(i) value based on the candidate mid luminance value and the APL function of the target display.

### Claim 7 (depends on 4)

The method of claim 4 further comprising:
determining a first tone-mapping curve mapping the input image to the target display based on the minimum luminance level of the target display, the reference maximum luminance level for the target display, and the input metadata; and
adjusting the first tone-mapping curve based on the output power factor.

### Claim 8 (depends on 7)

The method of claim 7, wherein adjusting the first tone-mapping curve comprises raising the output of the first tone-mapping curve to the power of the output power factor.

### Claim 9 (depends on 1)

A non-transitory computer-readable storage medium having stored thereon computer-executable instructions for executing with one or more processors a method in accordance with claim 1.

### Claim 10 (depends on 1)

An apparatus comprising a processor and configured to perform the method recited in claim 1.