# US 2026/0030731 A1 · Mapping a low resolution, noisy tone mapping operation onto high resolution images

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- Number: US 2026/0030731 A1
- Document ID: US20260030731A1
- Status: Published application
- Kind: A1
- Application number: 18/940,676
- Filed: 2024-11-07
- Published: 2026-01-29
- Earliest claimed: 2024-07-29
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Thilo Balke; Hamid Rahim Sheikh; John Seokjun Lee
- Web page: https://patentgrep.com/patent/US20260030731A1

## CPC

- G06T 5/92: based on global image properties
- G06T 3/18: Image warping, e.g. rearranging pixels individually
- G06T 3/4015: Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
- G06T 5/40: using histogram techniques
- G06T 5/70: Denoising; Smoothing
- G06V 10/758: {Involving statistics of pixels or of feature values, e.g. histogram matching}
- G06T 2207/20016: Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING

## Abstract

To employ low resolution, noisy tone mapping operations for high resolution images, at least one raw image frame is converted to a first image at a higher resolution and a second image at a lower resolution. Tone mapping is applied to the second image to derive a third image at the lower resolution. Histogram matching and regularization are performed to determine a lookup table approximating histogram matching of the second image to the third image. A global gain map is derived based on luma for the first image and the lookup table. A local gain map is derived by up-sampling and denoising residual differences between the third image and the lookup table applied to the second image. Based on the global gain map and the local gain map, a total gain map is determined for tone mapping the first image to produce a fourth image at the first resolution.

## Claims

### Claim 1

A method comprising:
converting at least one raw image frame to a first image at a first resolution and a second image at a second resolution, wherein the second resolution is lower than the first resolution;
applying tone mapping to the second image to derive a third image at the second resolution;
performing histogram matching and regularization using the second image and the third image to determine a lookup table approximating histogram matching of the second image to the third image;
deriving a global gain map for tone mapping based on luma for the first image and the lookup table;
deriving a local gain map by up-sampling and denoising residual differences between the third image and the lookup table applied to the second image after regularization of the lookup table; and
based on the global gain map and the local gain map, determining a total gain map for tone mapping the first image to produce a fourth image at the first resolution.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
refining the total gain map based the first image to retain detail and contrast from the first image in a filtered gain map.

### Claim 3 (depends on 2)

The method of claim 2, further comprising:
applying the filtered gain map to the first image to produce a fifth image at the first resolution.

### Claim 4 (depends on 1)

The method of claim 1, wherein the global gain map is derived from a ratio of the lookup table applied to the luma for the first image and the luma for the first image.

### Claim 5 (depends on 1)

The method of claim 1, wherein the local gain map is derived from a ratio of the third image and the lookup table applied to the second image.

### Claim 6 (depends on 1)

The method of claim 1, wherein, when the first image is processed in tiles, the global gain map is derived in tiles until all tiles have been processed.

### Claim 7 (depends on 1)

The method of claim 1, wherein one or more of warping, blending, or demosaicing is applied to the at least one raw image frame to produce the first image at the first resolution and to produce the second image at the second resolution.

### Claim 8

An electronic device comprising:
a memory storing image data; and
at least one processing device configured to:
convert at least one raw image frame to a first image at a first resolution and a second image at a second resolution, wherein the second resolution is lower than the first resolution;
apply tone mapping to the second image to derive a third image at the second resolution;
perform histogram matching and regularization using the second image and the third image to determine a lookup table approximating histogram matching of the second image to the third image;
derive a global gain map for tone mapping based on luma for the first image and the lookup table;
derive a local gain map by up-sampling and denoising residual differences between the third image and the lookup table applied to the second image after regularization of the lookup table; and
based on the global gain map and the local gain map, determine a total gain map for tone mapping the first image to produce a fourth image at the first resolution.

### Claim 9 (depends on 8)

The electronic device of claim 8, wherein the at least one processing device is further configured to:
refine the total gain map based the first image to retain detail and contrast from the first image in a filtered gain map.

### Claim 10 (depends on 9)

The electronic device of claim 9, wherein the at least one processing device is further configured to:
apply the filtered gain map to the first image to produce a fifth image at the first resolution.

### Claim 11 (depends on 8)

The electronic device of claim 8, wherein the global gain map is derived from a ratio of the lookup table applied to the luma for the first image and the luma for the first image.

### Claim 12 (depends on 8)

The electronic device of claim 8, wherein the local gain map is derived from a ratio of the third image and the lookup table applied to the second image.

### Claim 13 (depends on 8)

The electronic device of claim 8, wherein, when the first image is processed in tiles, the global gain map is derived in tiles until all tiles have been processed.

### Claim 14 (depends on 8)

The electronic device of claim 8, wherein one or more of warping, blending, or demosaicing is applied to the at least one raw image frame to produce the first image at the first resolution and to produce the second image at the second resolution.

### Claim 15

A non-transitory machine-readable medium containing instructions that when executed cause at least one processor to:
convert at least one raw image frame to a first image at a first resolution and a second image at a second resolution, wherein the second resolution is lower than the first resolution;
apply tone mapping to the second image to derive a third image at the second resolution;
perform histogram matching and regularization using the second image and the third image to determine a lookup table approximating histogram matching of the second image to the third image;
derive a global gain map for tone mapping based on luma for the first image and the lookup table;
derive a local gain map by up-sampling and denoising residual differences between the third image and the lookup table applied to the second image after regularization of the lookup table; and
based on the global gain map and the local gain map, determine a total gain map for tone mapping the first image to produce a fourth image at the first resolution.

### Claim 16 (depends on 15)

The non-transitory machine-readable medium of claim 15, wherein the instructions when executed cause the at least one processor to:
refine the total gain map based the first image to retain detail and contrast from the first image in a filtered gain map.

### Claim 17 (depends on 16)

The non-transitory machine-readable medium of claim 16, wherein the instructions when executed cause the at least one processor to:
apply the filtered gain map to the first image to produce a fifth image at the first resolution.

### Claim 18 (depends on 15)

The non-transitory machine-readable medium of claim 15, wherein the global gain map is derived from a ratio of the lookup table applied to the luma for the first image and the luma for the first image.

### Claim 19 (depends on 15)

The non-transitory machine-readable medium of claim 15, wherein the local gain map is derived from a ratio of the third image and the lookup table applied to the second image.

### Claim 20 (depends on 15)

The non-transitory machine-readable medium of claim 15, wherein, when the first image is processed in tiles, the global gain map is derived in tiles until all tiles have been processed.