# US 11,908,113 B2 · Image processing method and image processing device using the same

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- Number: US 11,908,113 B2
- Document ID: US11908113B2
- Status: Granted
- Kind: B2
- Application number: 17/519,415
- Filed: 2021-11-04
- Published: 2022-05-26
- Granted: 2024-02-20
- Earliest claimed: 2020-11-20
- Assignees: Cvitek Co. Ltd.
- Applicants: Cvitek Co. Ltd.
- Inventors: Jen-Shi Wu; Hsin-Hui Chen
- Web page: https://patentgrep.com/patent/US11908113B2

## CPC

- G06T 5/40: using histogram techniques
- G06T 5/50: using two or more images, e.g. averaging or subtraction
- G06T 5/92: based on global image properties
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

An image processing method includes: (a) receiving a to-be-processed image; (b) obtaining a target brightness of the to-be-processed image; (c) creating a histogram curve of the to-be-processed image; (d) clipping the histogram curve according to a clipping value; (e) obtaining a mapping function of the clipped histogram curve; (f) obtaining a mapped image mapped according to the mapping function; (g) obtaining an average brightness of the mapped image; (h) obtaining a difference between the target brightness and the average brightness; and (i) if the difference is greater than a threshold, adjusting the clipping value and repeating steps (d) to (i) until the difference is less than the threshold. Thus, if the to-be-processed image does not reach the target brightness, the image processing device automatically repeats steps (c) to (i) until the to-be-processed image reaches the target brightness.

## Claims

### Claim 1

An image processing method, characterized in comprising the following steps:
(a) receiving a to-be-processed image;
(b) obtaining a target brightness of the to-be-processed image;
(c) creating a histogram curve of the to-be-processed image;
(d) clipping the histogram curve according to a clipping value;
(e) obtaining a mapping function of the clipped histogram curve;
(f) obtaining a mapped image mapped according to the mapping function;
(g) obtaining an average brightness of the mapped image;
(h) obtaining a difference between the target brightness and the average brightness; and
(i) if the difference is greater than a threshold value, adjusting the clipping value and repeat step (c)-step (i) until the difference is less than the threshold value.

### Claim 2 (depends on 1)

The image processing method according to claim 1, wherein step (d) further comprises:
distributing the clipped part of the histogram curve to the unclipped part of the histogram curve; and
wherein step (e) comprises:
accumulating the clipped histogram curve to obtain the mapping function.

### Claim 3 (depends on 1)

The image processing method according to claim 1, wherein the initial value of the clipping value is a fixed value.

### Claim 4 (depends on 1)

The image processing method according to claim 1, wherein the target brightness is α times the average brightness of the to-be-processed image; α is a real number.

### Claim 5 (depends on 1)

The image processing method according to claim 1, wherein in step (i), the clipping value is adjusted according to the following formulas:
step
⁢
⁢
(
n
+
1
)
=
η
⁡
(
n
+
1
)
×
step_
⁢
1
;
U
⁡
(
n
+
1
)
=
U
⁡
(
n
)
±
step
⁢
⁢
(
n
+
1
)
;
wherein the step_1 is an initial clipping value for the 1st iteration; step(n+1) is a value of step adjustment for the (n+1)th iteration; η(n+1) is an adjustment rate for the (n+1)th iteration; U(n) is the clipping value for the nth iteration; U(n+1) is the clipping value for the (n+1)th iteration; n is a positive integer equivalent to or greater than 2.

### Claim 6 (depends on 5)

The image processing method according to claim 5, wherein in step (i),
η(n) is obtained according to the following formula:
η
⁡
(
n
+
1
)
=
k
×
η
⁡
(
n
)
;
wherein k is an attenuation constant and is a real number less than 1; η(n) is the adjustment rate for the nth iteration; value of η(1) is 1.

### Claim 7 (depends on 5)

The image processing method according to claim 5, wherein step (i) further comprises:
determining whether the average brightness is greater than the target brightness;
if the average brightness is greater than the target brightness, decreasing value of step(n+1).

### Claim 8 (depends on 5)

The image processing method according to claim 5, wherein step (i) further comprises:
determining whether the average brightness is greater than the target brightness; and
if the average brightness is less than the target brightness, increasing the value of step(n+1).

### Claim 9 (depends on 1)

The image processing method according to claim 1, wherein the image processing method further comprises:
combining several images to form a to-be-processed image, wherein the to-be-processed image is a wide dynamic image.

### Claim 10

An image processing device, characterized in that the image processing device comprises:
an input port configured to
(a) receive a to-be-processed image;
a processor configured to
(b) obtain a target brightness of the to-be-processed image;
(c) create a histogram curve of the to-be-processed image;
(d) clip the histogram curve according to a clipping value;
(e) obtain a mapping function of the clipped histogram curve;
(f) obtain a mapped image mapped according to the mapping function;
(g) obtain an average brightness of the mapped image;
(h) obtain a difference between the target brightness and the average brightness; and
(i) if the difference is greater than a threshold value, adjust the clipping value and repeat step (c) to step (i) until the difference is less than the threshold value.

### Claim 11 (depends on 10)

The image processing device according to claim 10, wherein the processor further is configured to
in step (d), distribute the clipped part of the histogram curve to the unclipped part of the histogram curve; and
in step (e), accumulate the clipped histogram curve to obtain the mapping function.

### Claim 12 (depends on 10)

The image processing device according to claim 10, wherein the initial value of the clipping value is a fixed value.

### Claim 13 (depends on 10)

The image processing device according to claim 10, wherein the target brightness is α times the average brightness of the to-be-processed image; α is a real number.

### Claim 14 (depends on 10)

The image processing device according to claim 10, wherein the processor further is configured to
in step (i), adjust the clipping value according to the following formulas:
step
⁢
⁢
(
n
+
1
)
=
η
⁡
(
n
+
1
)
×
step_
⁢
1
;
U
⁡
(
n
+
1
)
=
U
⁡
(
n
)
±
step
⁢
⁢
(
n
+
1
)
;
wherein the step_1 is the initial clipping value for the 1st iteration; step(n+1) is value of step adjustment for the (n+1)th iteration; η(n+1) is the adjustment rate for the (n+1)th iteration; U(n) is the clipping value for the nth iteration; U(n+1) is the clipping value for the (n+1)th iteration; n is a positive integer equivalent to or greater than 2.

### Claim 15 (depends on 14)

The image processing device according to claim 14, wherein the processor further is configured to
in step (i), obtain η(n) according to the following formula:
η
⁡
(
n
+
1
)
=
k
×
η
⁡
(
n
)
;
wherein k is an attenuation constant and is a real number less than 1; η(n) is the adjustment rate for the nth iteration; value of η(1) is 1.

### Claim 16 (depends on 14)

The image processing device according to claim 14, wherein the processor further is configured to
in step (i), determine whether the average brightness is greater than the target brightness; and
if the average brightness is greater than the target brightness, decrease the value of step(n+1).

### Claim 17 (depends on 14)

The image processing device according to claim 14, wherein the processor further is configured to
in step (i), determine whether the average brightness is greater than the target brightness; and
if the average brightness is less than the target brightness, increase the value of step(n+1).

### Claim 18 (depends on 10)

The image processing device according to claim 10, wherein the processor further is configured to
combine several images to form a to-be-processed image, wherein the to-be-processed image is a wide dynamic image.