Image dynamic range processing method and apparatus
This application provides an image dynamic range processing method and apparatus. The method includes: obtaining a first coordinate value of a first interpolation point and a first coordinate value of a third interpolation point related to a first cubic spline curve; and determining, based on histogram information of a first luminance interval of a to-be-processed image, a first coordinate value of a second interpolation point related to the first cubic spline curve. The first luminance interval is an interval between the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point. The first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, and the first coordinate value of the third interpolation point are used to determine a function of the first cubic spline curve.
1 . An image dynamic range processing method, comprising:
obtaining, by a processor, a first coordinate value of a first interpolation point and a first coordinate value of a third interpolation point related to a first cubic spline curve, wherein the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point are luminance values;
determining, by a processor, based on histogram information of a first luminance interval of a to-be-processed image, a first coordinate value of a second interpolation point related to the first cubic spline curve, wherein
the first coordinate value of the second interpolation point is calculated based on a distribution of pixel luminance values within the first luminance interval;
the first luminance interval of the to-be-processed image is an interval between the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point; and
the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, and the first coordinate value of the third interpolation point are used to determine a function of the first cubic spline curve;
mapping a luminance value of a pixel whose luminance value is in the first luminance interval in the to-be-processed image to a first target luminance value based on the function of the first cubic spline curve to modify a dynamic range of the to-be-processed image; and
sending the to-be-processed image to a display device for displaying in accordance with the modified dynamic range.
2 . The method according to claim 1 , wherein the function of the first cubic spline curve is obtained in the following manner:
obtaining a function of a basic mapping curve;
mapping the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point based on the function of the basic mapping curve, to obtain a second coordinate value of the first interpolation point and a second coordinate value of the third interpolation point;
determining a second coordinate value of the second interpolation point according to the following equation:
VA
2
=
VA
1
+
(
TH
2
-
TH
1
)
×
(
VA
3
-
VA
1
)
TH
3
-
TH
1
,
wherein
VA 2 is the second coordinate value of the second interpolation point, VA 1 is the second coordinate value of the first interpolation point, VA 3 is the second coordinate value of the third interpolation point, TH 2 is the first coordinate value of the second interpolation point, TH 1 is the first coordinate value of the first interpolation point, and TH 3 is the first coordinate value of the third interpolation point; and
determining the function of the first cubic spline curve based on the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, the first coordinate value of the third interpolation point, the second coordinate value of the first interpolation point, the second coordinate value of the third interpolation point, and the second coordinate value of the second interpolation point.
3 . The method according to claim 1 , wherein the method further comprises:
determining, based on the first coordinate value of the third interpolation point and a maximum RGB component value of a first pixel of the to-be-processed image, first coordinate values of a fourth interpolation point, a fifth interpolation point, and a sixth interpolation point related to a second cubic spline curve, wherein the first pixel is a pixel with a largest maximum RGB component value in the to-be-processed image, and the maximum RGB component value of the pixel is a largest value of an R component, a G component, and a B component of the pixel; and
wherein the first coordinate value of the fourth interpolation point, the first coordinate value of the fifth interpolation point, and the first coordinate value of the sixth interpolation point are used to determine a function of the second cubic spline curve, the function of the second cubic spline curve is used to map a luminance value of a pixel whose luminance value is in a second luminance interval in the to-be-processed image to a second target luminance value, to modify the dynamic range of the to-be-processed image, the second luminance interval is an interval between the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, and the first luminance interval and the second luminance interval do not overlap.
4 . The method according to claim 1 , wherein the first coordinate value of the second interpolation point is determined according to the following equation:
TH
2
=
∑
i
=
0
N
frame
f
(
i
)
N
frame
,
wherein
TH 2 is the first coordinate value of the second interpolation point, N frame is a total quantity of pixels whose luminance values are in the first luminance interval in the to-be-processed image, i is an i th pixel in the pixels whose luminance values are in the first luminance interval in the to-be-processed image, and f(i) is a luminance value of the i th pixel.
5 . The method according to claim 3 , wherein the determining, based on the first coordinate value of the third interpolation point and the maximum RGB component value of the first pixel of the to-be-processed image, the first coordinate values of the fourth interpolation point, the fifth interpolation point, and the sixth interpolation point related to the second cubic spline curve comprises:
determining the first coordinate value of the fourth interpolation point according to a first equation, wherein the first equation is:
TH1_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
;
determining the first coordinate value of the fifth interpolation point according to a second equation, wherein the second equation is:
TH2_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
1
)
U
;
and
setting the first coordinate value of the sixth interpolation point to the maximum RGB component value of the first pixel, wherein
TH 1 _high is the first coordinate value of the fourth interpolation point, TH 2 _high is the first coordinate value of the fifth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, THB is the first coordinate value of the third interpolation point, and U is a preset value.
6 . The method according to claim 3 , wherein the determining, based on the first coordinate value of the third interpolation point and the maximum RGB component value of the first pixel of the to-be-processed image, the first coordinate values of the fourth interpolation point, the fifth interpolation point, and the sixth interpolation point related to the second cubic spline curve comprises:
determining an initial value of the first coordinate value of the fourth interpolation point according to the following equation:
TH1_high
1
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
,
wherein
TH 1 _high 1 is the initial value of the first coordinate value of the fourth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, U is a preset value, and THB is the first coordinate value of the third interpolation point;
setting the first coordinate value of the sixth interpolation point to the maximum RGB component value of the first pixel;
determining a first pixel quantity and a second pixel quantity based on the initial value of the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, wherein the first pixel quantity is a quantity of pixels whose luminance values are in a third luminance interval in the to-be-processed image, the third luminance interval is an interval between the initial value of the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, and the second pixel quantity is a total quantity of pixels in the to-be-processed image or in a luminance histogram of the to-be-processed image;
determining the first coordinate value of the fourth interpolation point based on the first pixel quantity, the second pixel quantity, the first coordinate value of the third interpolation point, the initial value of the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point; and
determining the first coordinate value of the fifth interpolation point based on histogram information of the second luminance interval of the to-be-processed image, the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point.
7 . The method according to claim 6 , wherein the second luminance interval comprises N subintervals, N is a positive integer, and the determining the first coordinate value of the fifth interpolation point based on histogram information of the second luminance interval of the to-be-processed image, the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point comprises:
determining an i th subinterval from the N subintervals, wherein the i th subinterval is in n subintervals of the N subintervals, a sequence number of the n subintervals is greater than or equal to N/4, the sequence number of the n subintervals is less than or equal to 3N/4, and a quantity of pixels whose luminance values are in the i th subinterval in the to-be-processed image is a smallest value in the n subintervals; and
determining the first coordinate value of the fifth interpolation point based on the first coordinate value of the fourth interpolation point, the first coordinate value of the sixth interpolation point, and i.
8 . The method according to claim 6 , wherein the determining the first coordinate value of the fourth interpolation point based on the first pixel quantity, the second pixel quantity, the first coordinate value of the third interpolation point, the initial value of the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point comprises:
determining a ratio of a length of the third luminance interval to the maximum RGB component value of the first pixel; and
determining the first coordinate value of the fourth interpolation point according to the following equation:
TH1_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
-
POW
(
highRatio
wholeratio
,
j
)
×
Max
Source
-
TH
3
U
,
wherein
TH 1 _high is the first coordinate value of the fourth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, U is a preset value, THB is the first coordinate value of the third interpolation point, highRatio is a ratio of the first pixel quantity to the second pixel quantity,
wholeratio
=
TH3_high
-
TH1_high1
Max
Source
,
whole ratio is the ratio of the length of the third luminance interval to the maximum RGB component value of the first pixel, TH 1 _high 1 is the initial value of the first coordinate value of the fourth interpolation point, TH 3 _high is the first coordinate value of the sixth interpolation point, and POW(x, j) indicates the j th power of x.
9 . The method according to claim 3 , wherein the method further comprises:
determining a third pixel quantity and a fourth pixel quantity based on a luminance histogram of the to-be-processed image, the first coordinate value of the fourth interpolation point, the first coordinate value of the fifth interpolation point, and the first coordinate value of the sixth interpolation point, wherein the third pixel quantity is a quantity of pixels in an interval between the first coordinate value of the fourth interpolation point and the first coordinate value of the fifth interpolation point in the luminance histogram, and the fourth pixel quantity is a quantity of pixels in an interval between the first coordinate value of the fifth interpolation point and the first coordinate value of the sixth interpolation point in the luminance histogram; and
determining adjustment strength of a second coordinate value of the fifth interpolation point according to the following equation:
TH_high
_strength
=
{
TH_high
_strength
1
+
Δ
,
NUM
1
<
NUM
2
TH_high
_strength
1
+
2
Δ
,
2
NUM
1
<
NUM
2
,
wherein
TH_high_strength is the adjustment strength of the second coordinate value of the fifth interpolation point, TH_high_strength 1 is a default value of the adjustment strength of the second coordinate value of the fifth interpolation point, Lis an adjustment operation, NUM 1 is the third pixel quantity, and NUM 2 is the fourth pixel quantity;
wherein the adjustment strength indicates an offset degree of the second coordinate value of the fifth interpolation point relative to an initial value of the second coordinate value of the fifth interpolation point.
10 . An image processing device, comprising:
a processor; and
a memory;
wherein the processor is coupled to the memory, and the processor is configured to enable the image processing device to:
obtain a first coordinate value of a first interpolation point and a first coordinate value of a third interpolation point related to a first cubic spline curve generated by a display device, wherein the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point are luminance values; and
determine, based on histogram information of a first luminance interval of a to-be-processed image, a first coordinate value of a second interpolation point related to the first cubic spline curve, wherein
the first coordinate value of the second interpolation point is calculated based on a distribution of pixel luminance values within the first luminance interval;
the first luminance interval of the to-be-processed image is an interval between the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point; and
the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, and the first coordinate value of the third interpolation point are used to determine a function of the first cubic spline curve;
map a luminance value of a pixel whose luminance value is in the first luminance interval in the to-be-processed image to a first target luminance value based on the function of the first cubic spline curve to modify a dynamic range of the to-be-processed image; and
send the to-be-processed image to the display device for displaying in accordance with the modified dynamic range.
11 . The image processing device according to claim 10 , wherein the processor is further configured to enable the image processing device to:
obtain a function of a basic mapping curve;
map the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point based on the function of the basic mapping curve, to obtain a second coordinate value of the first interpolation point and a second coordinate value of the third interpolation point;
determine a second coordinate value of the second interpolation point according to the following equation:
VA
2
=
VA
1
+
(
TH
2
-
T
H
1
)
×
(
VA
3
-
VA
1
)
T
H
3
-
T
H
1
,
wherein
VA 2 is the second coordinate value of the second interpolation point, VA 1 is the second coordinate value of the first interpolation point, VA 3 is the second coordinate value of the third interpolation point, TH 2 is the first coordinate value of the second interpolation point, TH 1 is the first coordinate value of the first interpolation point, and TH 3 is the first coordinate value of the third interpolation point; and
determine the function of the first cubic spline curve based on the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, the first coordinate value of the third interpolation point, the second coordinate value of the first interpolation point, the second coordinate value of the third interpolation point, and the second coordinate value of the second interpolation point.
12 . The image processing device according to claim 10 , wherein the processor is further configured to enable the image processing device to:
determine, based on the first coordinate value of the third interpolation point and a maximum RGB component value of a first pixel of the to-be-processed image, first coordinate values of a fourth interpolation point, a fifth interpolation point, and a sixth interpolation point related to a second cubic spline curve, wherein the first pixel is a pixel with a largest maximum RGB component value in the to-be-processed image, and the maximum RGB component value of the pixel is a largest value of an R component, a G component, and a B component of the pixel; and
the first coordinate value of the fourth interpolation point, the first coordinate value of the fifth interpolation point, and the first coordinate value of the sixth interpolation point are used to determine a function of the second cubic spline curve, the function of the second cubic spline curve is used to map a luminance value of a pixel whose luminance value is in a second luminance interval in the to-be-processed image to a second target luminance value, to modify the dynamic range of the to-be-processed image, the second luminance interval is an interval between the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, and the first luminance interval and the second luminance interval do not overlap.
13 . The image processing device according to claim 10 , wherein the first coordinate value of the second interpolation point is determined according to the following equation:
TH
2
=
∑
i
=
0
N
frame
f
(
i
)
N
frame
,
wherein
TH 2 is the first coordinate value of the second interpolation point, N frame is a total quantity of pixels whose luminance values are in the first luminance interval in the to-be-processed image, i is an i th pixel in the pixels whose luminance values are in the first luminance interval in the to-be-processed image, and f(i) is a luminance value of the i th pixel.
14 . The image processing device according to claim 12 , wherein the processor is further configured to enable the image processing device to:
determine the first coordinate value of the fourth interpolation point according to a first equation, wherein the first equation is:
TH
1
_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
;
determine the first coordinate value of the fifth interpolation point according to a second equation, wherein the second equation is:
TH2_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
1
)
U
;
and
set the first coordinate value of the sixth interpolation point to the maximum RGB component value of the first pixel, wherein
TH 1 _high is the first coordinate value of the fourth interpolation point, TH 2 _high is the first coordinate value of the fifth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, THB is the first coordinate value of the third interpolation point, and U is a preset value.
15 . The image processing device according to claim 12 , wherein the processor is further configured to enable the image processing device to:
determine an initial value of the first coordinate value of the fourth interpolation point according to the following equation:
TH1_high
1
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
,
wherein
TH 1 _high 1 is the initial value of the first coordinate value of the fourth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, U is a preset value, and THB is the first coordinate value of the third interpolation point;
set the first coordinate value of the sixth interpolation point to the maximum RGB component value of the first pixel;
determine a first pixel quantity and a second pixel quantity based on the initial value of the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, wherein the first pixel quantity is a quantity of pixels whose luminance values are in a third luminance interval in the to-be-processed image, the third luminance interval is an interval between the initial value of the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, and the second pixel quantity is a total quantity of pixels in the to-be-processed image or in a luminance histogram of the to-be-processed image;
determine the first coordinate value of the fourth interpolation point based on the first pixel quantity, the second pixel quantity, the first coordinate value of the third interpolation point, the initial value of the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point; and
determine the first coordinate value of the fifth interpolation point based on histogram information of the second luminance interval of the to-be-processed image, the first coordinate value of the fourth interpolation point, and the first coordinate value of the sixth interpolation point.
16 . The image processing device according to claim 12 , wherein the processor is further configured to enable the image processing device to:
determine a third pixel quantity and a fourth pixel quantity based on a luminance histogram of the to-be-processed image, the first coordinate value of the fourth interpolation point, the first coordinate value of the fifth interpolation point, and the first coordinate value of the sixth interpolation point, wherein the third pixel quantity is a quantity of pixels in an interval between the first coordinate value of the fourth interpolation point and the first coordinate value of the fifth interpolation point in the luminance histogram, and the fourth pixel quantity is a quantity of pixels in an interval between the first coordinate value of the fifth interpolation point and the first coordinate value of the sixth interpolation point in the luminance histogram; and
determining adjustment strength of a second coordinate value of the fifth interpolation point according to the following equation:
TH_high
_strength
=
{
TH_high
_strength
1
+
Δ
,
NUM
1
<
NUM
2
TH_high
_strength
1
+
2
Δ
,
2
NUM
1
<
NUM
2
,
wherein
TH_high_strength is the adjustment strength of the second coordinate value of the fifth interpolation point, TH_high_strength 1 is a default value of the adjustment strength of the second coordinate value of the fifth interpolation point, Lis an adjustment operation, NUM 1 is the third pixel quantity, and NUM 2 is the fourth pixel quantity;
wherein the adjustment strength indicates an offset degree of the second coordinate value of the fifth interpolation point relative to an initial value of the second coordinate value of the fifth interpolation point.
17 . A non-transitory computer-readable storage medium storing a computer program, which, when executed by a processor of an image processing device, cause the image processing device to:
obtain a first coordinate value of a first interpolation point and a first coordinate value of a third interpolation point related to a first cubic spline curve generated by a display device, wherein the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point are luminance values;
determining, based on histogram information of a first luminance interval of a to-be-processed image, a first coordinate value of a second interpolation point related to the first cubic spline curve, wherein
the first coordinate value of the second interpolation point is calculated based on a distribution of pixel luminance values within the first luminance interval;
the first luminance interval of the to-be-processed image is an interval between the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point; and
the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, and the first coordinate value of the third interpolation point are used to determine a function of the first cubic spline curve;
map a luminance value of a pixel whose luminance value is in the first luminance interval in the to-be-processed image to a first target luminance value based on the function of the first cubic a spline curve to modify a dynamic range of the to-be-processed image; and
send the to-be-processed image to the display device for displaying in accordance with the modified dynamic range.
18 . The non-transitory computer-readable storage medium according to claim 17 , wherein the computer program is further enabling the computer or the processor to:
obtain a function of a basic mapping curve;
map the first coordinate value of the first interpolation point and the first coordinate value of the third interpolation point based on the function of the basic mapping curve, to obtain a second coordinate value of the first interpolation point and a second coordinate value of the third interpolation point;
determine a second coordinate value of the second interpolation point according to the following equation:
VA
2
=
VA
1
+
(
TH
2
-
TH
1
)
×
(
VA
3
-
VA
1
)
TH
3
-
TH
1
,
wherein
VA 2 is the second coordinate value of the second interpolation point, VA 1 is the second coordinate value of the first interpolation point, VA 3 is the second coordinate value of the third interpolation point, TH 2 is the first coordinate value of the second interpolation point, TH 1 is the first coordinate value of the first interpolation point, and TH 3 is the first coordinate value of the third interpolation point; and
determine the function of the first cubic spline curve based on the first coordinate value of the first interpolation point, the first coordinate value of the second interpolation point, the first coordinate value of the third interpolation point, the second coordinate value of the first interpolation point, the second coordinate value of the third interpolation point, and the second coordinate value of the second interpolation point.
19 . The non-transitory computer-readable storage medium according to claim 17 , wherein the computer program is further enabling the computer or the processor to:
determine, based on the first coordinate value of the third interpolation point and a maximum RGB component value of a first pixel of the to-be-processed image, first coordinate values of a fourth interpolation point, a fifth interpolation point, and a sixth interpolation point related to a second cubic spline curve, wherein the first pixel is a pixel with a largest maximum RGB component value in the to-be-processed image, and the maximum RGB component value of the pixel is a largest value of an R component, a G component, and a B component of the pixel; and
the first coordinate value of the fourth interpolation point, the first coordinate value of the fifth interpolation point, and the first coordinate value of the sixth interpolation point are used to determine a function of the second cubic spline curve, the function of the second cubic spline curve is used to map a luminance value of a pixel whose luminance value is in a second luminance interval in the to-be-processed image to a second target luminance value, to modify the dynamic range of the to-be-processed image, the second luminance interval is an interval between the first coordinate value of the fourth interpolation point and the first coordinate value of the sixth interpolation point, and the first luminance interval and the second luminance interval do not overlap.
20 . The computer-readable storage medium according to claim 19 , wherein the computer program is further enabling the computer or the processor to:
determine the first coordinate value of the fourth interpolation point according to a first equation, wherein the first equation is:
TH
1
_high
=
TH
3
+
(
Max
Source
-
TH
3
)
×
(
U
-
2
)
U
;
determine the first coordinate value of the fifth interpolation point according to a second equation, wherein the second equation is:
TH2_high
=
TH
3
+
(
MaxS
ource
-
TH
3
)
×
(
U
-
1
)
U
;
and
set the first coordinate value of the sixth interpolation point to the maximum RGB component value of the first pixel, wherein
TH 1 _high is the first coordinate value of the fourth interpolation point, TH 2 _high is the first coordinate value of the fifth interpolation point, a value of MaxSource is the maximum RGB component value of the first pixel, THB is the first coordinate value of the third interpolation point, and U is a preset value.