Dynamic range mapping method and apparatus
This application provides a dynamic range mapping method and apparatus. The dynamic range mapping method includes: obtaining a display parameter of a terminal device; obtaining feature information of image data; obtaining a first parameter of a first tone mapping curve of the image data; when a preset condition is met, obtaining a second parameter of a second tone mapping curve based on the first parameter, the display parameter of the terminal device, and the feature information of the image data, where output luminance at a first point on the second tone mapping curve is not greater than input luminance at the first point on the second tone mapping curve; and performing dynamic range mapping on the image data based on the second parameter of the second tone mapping curve.
1. A dynamic range mapping method, comprising:
obtaining a display parameter of a terminal device;
obtaining feature information of image data;
obtaining a first parameter of a first tone mapping curve of the image data, wherein the first parameter comprises a second linear spline curve parameter, the second linear spline curve parameter comprises a slope MB_mid[0][0] of a second linear spline on the first tone mapping curve and/or a maximum value TH3_mid[0] of a luminance value of a range pixel of the second linear spline, the display parameter comprises maximum display luminance MaxDisplay of the terminal device, and the feature information comprises a maximum luminance correction value max_lum of the image data;
when a preset condition is met, obtaining a second parameter of a second tone mapping curve based on the first parameter, the display parameter of the terminal device, and the feature information of the image data, the obtaining the second parameter of the second tone mapping curve based on the first parameter, the display parameter, and the feature information further comprising:
adjusting the curve parameters MB_mid[0][0] and TH3_mid[0] based on the maximum display luminance MaxDisplay and the maximum luminance correction value max_lum to obtain the curve parameters MB[0][0] and TH3[0]; and
performing dynamic range mapping on the image data based on the second parameter of the second tone mapping curve.
2. The method according to claim 1 , wherein the preset condition comprises:
a parameter a P1 the first parameter is greater than a value Ta, wherein the value Ta is obtained based on p P1 in the first parameter and a preset correspondence between Ta and p P1 .
3. The method according to claim 1 , wherein the second parameter comprises a first linear spline curve parameter, and the first linear spline curve parameter comprises the MB[0][0] which is a slope of a first linear spline on the second tone mapping curve and/or the TH3[0] which is a maximum value of a luminance value of a range pixel of the first linear spline and/or an intersection point base_offset of the first linear spline and a vertical coordinate axis.
4. The method according to claim 1 , wherein the curve parameters MB_mid[0][0] and TH3_mid[0], and the curve parameters MB[0][0] and TH3[0] satisfy:
MB[ 0][0]=min(max( MB _mid[0][0]+(1− MB _mid[0][0])*( WA ) N 1 ,MB _mid[0][0]),1),
and
TH 3[0]=min(max( TH 3_mid[0]+(max_lum− TH 3_mid[0])*( WA ) N 2 ,TH 3_mid[0]),1),
wherein
WA
=
MaxDisplay
max_lum
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
1
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
,
G
(
L
,
m_a
)
=
(
K
3
×
(
L
-
m_b
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
-
m_b
m_a
)
1
m
_
m
)
1
m
_
n
,
or
G
(
L
,
m_a
)
=
(
K
3
×
(
L
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
m_a
)
1
m
_
m
)
1
m
_
n
,
wherein
a function H(L) corresponds to a tone mapping curve, m_a, m_b, m_m, m_n, k1, k2, and k3 are curve parameters, H(L,m_a_T) indicates a H(L) value corresponding to an input variable L when a value of a parameter M_a of H(L) is m_a_T, N1 and N2 are rational numbers, max(a, b) indicates calculating a larger value of a and b, min(a, b) indicates calculating a smaller value of a and b, and H(L) is
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
+
m_b
,
or
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
.
5. The method according to claim 1 , wherein the second parameter comprises a cubic spline curve parameter, and the cubic spline curve parameter comprises interpolation point values TH1[1], TH2[1], and TH3[1] of a cubic spline on the second tone mapping curve, wherein TH1[1] indicates a minimum value of a luminance value of a first range pixel of the cubic spline, TH2[1] indicates a maximum value of the luminance value of the first range pixel of the cubic spline and a minimum value of a luminance value of a second range pixel of the cubic spline, and TH3[1] indicates a maximum value of the luminance value of the second range pixel of the cubic spline.
6. The method according to claim 1 , wherein the obtaining a first parameter of a first tone mapping curve of the image data comprises:
obtaining metadata of the image data; and
determining the first parameter of the first tone mapping curve based on the metadata and the display parameter.
7. A dynamic range mapping apparatus, comprising:
at least one processor; and
at least one memory coupled to the at least one processor and storing instructions, which when executed by the at least one processor, cause the at least one processor to:
obtain a display parameter of a terminal device,
obtain feature information of image data; and
obtain a first parameter of a first tone mapping curve of the image data, wherein the first parameter comprises a second linear spline curve parameter, the second linear spline curve parameter comprises a slope MB_mid[0][0] of a second linear spline on the first tone mapping curve and/or a maximum value TH3_mid[0] of a luminance value of a range pixel of the second linear spline, the display parameter comprises maximum display luminance MaxDisplay of the terminal device, and the feature information comprises a maximum luminance correction value max_lum of the image data;
when a preset condition is met, obtain a second parameter of a second tone mapping curve based on the first parameter, the display parameter of the terminal device, and the feature information of the image data, including adjusting the curve parameters MB_mid[0][0] and TH3_mid[0] based on the maximum display luminance MaxDisplay and the maximum luminance correction value max_lum to obtain the curve parameters MB[0][0] and TH3_[0]; and
perform dynamic range mapping on the image data based on the second parameter of the second tone mapping curve.
8. The apparatus according to claim 7 , wherein the preset condition comprises:
a parameter a P1 in the first parameter is greater than a value Ta, wherein the value Ta is obtained based on p P1 in the first parameter and a preset correspondence between Ta and p P1 .
9. The apparatus according to claim 7 , wherein the second parameter comprises a first linear spline curve parameter, and the first linear spline curve parameter comprises the MB[0][0] which is a slope of a first linear spline on the second tone mapping curve and/or the TH3[0] which is a maximum value of a luminance value of a range pixel of the first linear spline and/or an intersection point base_offset of the first linear spline and a vertical coordinate axis.
10. The apparatus according to claim 7 , wherein the curve parameters MB_mid[0][0] and TH3_mid[0], and the curve parameters MB[0][0] and TH3[0] satisfy:
MB[ 0][0]=min(max( MB _mid[0][0]+(1 −MB _mid[0][0])*( WA ) N 1 ,MB _mid[0][0]),1)
and
TH 3[0]=min(max( TH 3_mid[0]+(max_lum− TH 3_mid[0])*( WA ) N 2 ,TH 3_mid[0]),1),
wherein
WA
=
MaxDisplay
max_lum
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
1
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
,
G
(
L
,
m_a
)
=
(
K
3
×
(
L
-
m_b
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
-
m_b
m_a
)
1
m
_
m
)
1
m
_
n
,
or
G
(
L
,
m_a
)
=
(
K
3
×
(
L
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
m_a
)
1
m
_
m
)
1
m
_
n
,
wherein
a function H(L) corresponds to a tone mapping curve, m_a, m_b, m_m, m_n, k1, k2, and k3 are curve parameters, H(L, m_a_T) indicates a H(L) value corresponding to an input variable L when a value of a parameter M_a of H(L) is m_a_T, N1 and N2 are rational numbers, max(a, b) indicates calculating a larger value of a and b, min(a, b) indicates calculating a smaller value of a and b, and H(L) is
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
+
m_b
,
or
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
.
11. The apparatus according to claim 7 , wherein the second parameter comprises a cubic spline curve parameter, and the cubic spline curve parameter comprises interpolation point values TH1[1], TH2[1], and TH3[1] of a cubic spline on the second tone mapping curve, wherein TH1[1] indicates a minimum value of a luminance value of a first range pixel of the cubic spline, TH2[1] indicates a maximum value of the luminance value of the first range pixel of the cubic spline and a minimum value of a luminance value of a second range pixel of the cubic spline, and TH3[1] indicates a maximum value of the luminance value of the second range pixel of the cubic spline.
12. The apparatus according to claim 7 , wherein the at least one processor is configured to:
obtain metadata of the image data; and
determine the first parameter of the first tone mapping curve based on the metadata and the display parameter.
13. A non-transitory computer-readable storage medium, comprising a computer program, wherein when executed on a computer or by a processor, cause the computer or the processor to perform:
obtaining a display parameter of a terminal device;
obtaining feature information of image data;
obtaining a first parameter of a first tone mapping curve of the image data, wherein the first parameter comprises a second linear spline curve parameter, the second linear spline curve parameter comprises a slope MB_mid[0][0] of a second linear spline on the first tone mapping curve and/or a maximum value TH3_mid[0] of a luminance value of a range pixel of the second linear spline, the display parameter comprises maximum display luminance MaxDisplay of the terminal device, and the feature information comprises a maximum luminance correction value max_lum of the image data;
when a preset condition is met, obtaining a second parameter of a second tone mapping curve based on the first parameter, the display parameter of the terminal device, and the feature information of the image data, including adjusting the curve parameters MB_mid[0][0] and TH3_mid[0] based on the maximum display luminance MaxDisplay and the maximum luminance correction value max_lum to obtain the curve parameters MB[0][0] and TH3[0]; and
performing dynamic range mapping on the image data based on the second parameter of the second tone mapping curve.
14. The non-transitory computer-readable storage medium according to claim 13 , wherein the preset condition comprises:
a parameter a P1 in the first parameter is greater than a value Ta, wherein the value Ta is obtained based on p P1 in the first parameter and a preset correspondence between Ta and p P1 .
15. The non-transitory computer-readable storage medium according to claim 13 , wherein the second parameter comprises a first linear spline curve parameter, and the first linear spline curve parameter comprises the MB[0][0] which is a slope of a first linear spline on the second tone mapping curve and/or the TH3[0] which is a maximum value of a luminance value of a range pixel of the first linear spline and/or an intersection point base_offset of the first linear spline and a vertical coordinate axis.
16. The non-transitory computer-readable storage medium according to claim 13 , wherein the curve parameters MB_mid[0][0] and TH3_mid[0], and the curve parameters MB[0][0] and TH3[0] satisfy:
MB[ 0][0]=min(max( MB _mid[0][0]+(1 −MB _mid[0][0])*( WA ) N 1 ,MB _mid[0][0]),1),
and
TH 3[0]=min(max( TH 3_mid[0]+(max_lum− TH 3_mid[0])*( WA ) N 2 ,TH 3_mid[0]),1),
wherein
WA
=
MaxDisplay
max_lum
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
1
-
MaxDisplay
G
(
MaxDisplay
,
m_a
_T
)
,
G
(
L
,
m_a
)
=
(
K
3
×
(
L
-
m_b
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
-
m_b
m_a
)
1
m
_
m
)
1
m
_
n
,
or
G
(
L
,
m_a
)
=
(
K
3
×
(
L
m_a
)
1
m
_
m
m_p
-
(
K
1
×
m_p
-
K
2
)
×
(
L
m_a
)
1
m
_
m
)
1
m
_
n
,
wherein
a function H(L) corresponds to a tone mapping curve, m_a, m_b, m_m, m_n, k1, k2, and k3 are curve parameters, H(L, m_a_T) indicates a H(L) value corresponding to an input variable L when a value of a parameter M_a of H(L) is m_a_T, N1 and N2 are rational numbers, max(a, b) indicates calculating a larger value of a and b, min (a, b) indicates calculating a smaller value of a and b, and H(L) is
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
+
m_b
,
or
H
(
L
)
=
m_a
×
(
m_p
×
L
m
_
n
(
K
1
×
m_p
-
K
2
)
×
L
m
_
n
+
K
3
)
m
_
m
.
17. The non-transitory computer-readable storage medium according to claim 13 , wherein the computer or the processor is further configured to:
obtain metadata of the image data; and
determine the first parameter of the first tone mapping curve based on the metadata and the display parameter.