Logarithmic curve generation method, device, and storage medium
Embodiments of this application provide a logarithmic curve generation method, a device, and a storage medium. The method includes: determining a dynamic range of a photosensitive element of a mobile device and a coding depth of the mobile device; obtaining a plurality of numerical points within the dynamic range, where each numerical point includes a stop within the dynamic range and a corresponding code value; and performing curve fitting based on the plurality of numerical points to obtain a log curve, where when the mobile device shoots in a log mode, the log curve is used to convert, into a code value, a raw signal that is output by the photosensitive element and that indicates brightness.
1. A logarithmic curve generation method, comprising:
determining a dynamic range of a photosensitive element of a mobile device and a coding depth of the mobile device;
obtaining a plurality of numerical points within the dynamic range, wherein each numerical point comprises a stop within the dynamic range and a corresponding code value; and
performing curve fitting based on the plurality of numerical points to obtain a log curve, wherein when the mobile device shoots in a log mode, the log curve is used to convert, into a code value, a raw signal that is output by the photosensitive element and that indicates brightness;
when a horizontal axis is scene reflectance and a vertical axis is normalized code value, a formula of the log curve is as follows:
when T_scene_reflection is greater than 0.0028,
Y_cv
=
0.3145
×
log
1
0
(
5
.
5
5
5
5
56
×
T_scene
_reflection
+
0.07907
)
+
0
.
4
471
;
or
when T_scene_reflection is not greater than 0.0028,
Y_cv
=
11.4695
×
T_scene
_reflection
+
0.0928641
;
and
wherein T_scene_reflection is the scene reflectance, and Y_cv is the normalized code value.
2. The method according to claim 1 , wherein when the coding depth of the mobile device is 10 bits and the dynamic range is 11 stops, among the plurality of numerical points, a code value corresponding to stop −6 is 128, a code value corresponding to stop −5 is 149, a code value corresponding to stop −4 is 184, a code value corresponding to stop −3 is 235, a code value corresponding to stop −2 is 302, a code value corresponding to stop −1 is 381, a code value corresponding to stop 0 is 468, a code value corresponding to stop 1 is 560, a code value corresponding to stop 2 is 654, a code value corresponding to stop 3 is 749, a code value corresponding to stop 4 is 845, and a code value corresponding to stop 5 is 942; and
a scene reflectance corresponding to stop 0 is 18%.
3. The method according to claim 1 , wherein:
when the scene reflectance is 0%, a code value of 8 bits determined based on the log curve is 24, a code value of 10 bits determined based on the log curve is 95, and an IRE value determined based on the log curve is 3.5%;
when the scene reflectance is 18%, a code value of 8 bits determined based on the log curve is 116, a code value of 10 bits determined based on the log curve is 468, and an IRE value determined based on the log curve is 46.1%; or
when the scene reflectance is 600%, a code value of 8 bits determined based on the log curve is 236, a code value of 10 bits determined based on the log curve is 948, and an IRE value determined based on the log curve is 100.9%.
4. The method according to claim 1 , wherein after the performing curve fitting based on the plurality of numerical points to obtain a log curve, the method further comprises:
determining an inverse log curve corresponding to the log curve; and
when a vertical axis is scene reflectance and a horizontal axis is normalized code value, a formula of the inverse log curve is as follows:
when Y_cv is greater than 0.1251,
T_scene
_reflection
=
10
(
Y
_
cv
-
0.6813
)
/
0.3145
-
0.0142
;
or
when Y_cv is not greater than 0.1251,
T_scene
_reflection
=
(
Y_cv
-
0.0928641
)
/
11.4695
.
5. The method according to claim 1 , wherein the mobile device stores a table representing the log curve, and the table comprises a plurality of x coordinates and corresponding y coordinates on the log curve.
6. The method according to claim 1 , wherein the mobile device stores a computer-executable function representing the log curve.
7. The method according to claim 1 , wherein the dynamic range of the photosensitive element of the mobile device is determined based on a quantity of recognizable light spots in a raw image of a detection apparatus captured by the mobile device, and the detection apparatus displays a plurality of light spots with different brightness.
8. The method according to claim 1 , wherein color space corresponding to the log curve is color space ITU-R BT.2020.
9. An electronic device, comprising a memory and one or more processors, wherein
the memory is configured to store a computer program; and
the one or more processors are configured to execute the computer program, and executing the computer program causes the electronic device to:
determine a dynamic range of a photosensitive element of a mobile device and a coding depth of the mobile device;
obtain a plurality of numerical points within the dynamic range, wherein each numerical point comprises a stop within the dynamic range and a corresponding code value; and
perform curve fitting based on the plurality of numerical points to obtain a log curve, wherein when the mobile device shoots in a log mode, the log curve is used to convert, into a code value, a raw signal that is output by the photosensitive element and that indicates brightness;
wherein when a horizontal axis is scene reflectance and a vertical axis is normalized code value, a formula of the log curve is as follows:
when T_scene_reflection is greater than 0.0028,
Y_cv
=
0.3145
×
log
1
0
(
5
.
5
5
5
5
56
×
T_scene
_reflection
+
0.07907
)
+
0
.
4
471
;
or
when T_scene_reflection is not greater than 0.0028,
Y_cv
=
11.4695
×
T_scene
_reflection
+
0.0928641
;
and
wherein T_scene_reflection is the scene reflectance, and Y_cv is the normalized code value.
10. The electronic device according to claim 9 , wherein when the coding depth of the mobile device is 10 bits and the dynamic range is 11 stops, among the plurality of numerical points, a code value corresponding to stop −6 is 128, a code value corresponding to stop −5 is 149, a code value corresponding to stop −4 is 184, a code value corresponding to stop −3 is 235, a code value corresponding to stop −2 is 302, a code value corresponding to stop −1 is 381, a code value corresponding to stop 0 is 468, a code value corresponding to stop 1 is 560, a code value corresponding to stop 2 is 654, a code value corresponding to stop 3 is 749, a code value corresponding to stop 4 is 845, and a code value corresponding to stop 5 is 942; and
a scene reflectance corresponding to stop 0 is 18%.
11. The electronic device according to claim 9 , wherein:
when the scene reflectance is 0%, a code value of 8 bits determined based on the log curve is 24, a code value of 10 bits determined based on the log curve is 95, and an IRE value determined based on the log curve is 3.5%;
when the scene reflectance is 18%, a code value of 8 bits determined based on the log curve is 116, a code value of 10 bits determined based on the log curve is 468, and an IRE value determined based on the log curve is 46.1%; or
when the scene reflectance is 600%, a code value of 8 bits determined based on the log curve is 236, a code value of 10 bits determined based on the log curve is 948, and an IRE value determined based on the log curve is 100.9%.
12. The electronic device according to claim 9 , wherein executing the computer program further causes the electronic device to:
after performing curve fitting based on the plurality of numerical points to obtain the log curve, determining an inverse log curve corresponding to the log curve; and
when a vertical axis is scene reflectance and a horizontal axis is normalized code value, a formula of the inverse log curve is as follows:
when Y_cv is greater than 0.1251,
T_scene
_reflection
=
10
(
Y
_
cv
-
0.6813
)
/
0.3145
-
0.0142
;
or
when Y_cv is not greater than 0.1251,
T_scene
_reflection
=
(
Y_cv
-
0.0928641
)
/
11.4695
.
13. The electronic device according to claim 9 , wherein the mobile device stores a table representing the log curve, and the table comprises a plurality of x coordinates and corresponding y coordinates on the log curve.
14. The electronic device according to claim 9 , wherein the mobile device stores a computer-executable function representing the log curve.
15. The electronic device according to claim 9 , wherein the dynamic range of the photosensitive element of the mobile device is determined based on a quantity of recognizable light spots in a raw image of a detection apparatus captured by the mobile device, and the detection apparatus displays a plurality of light spots with different brightness.
16. The electronic device according to claim 9 , wherein color space corresponding to the log curve is color space ITU-R BT.2020.
17. A non-transitory computer storage medium, configured to store a computer program, and when the computer program is executed, an electronic device is caused to:
determine a dynamic range of a photosensitive element of a mobile device and a coding depth of the mobile device;
obtain a plurality of numerical points within the dynamic range, wherein each numerical point comprises a stop within the dynamic range and a corresponding code value; and
perform curve fitting based on the plurality of numerical points to obtain a log curve, wherein when the mobile device shoots in a log mode, the log curve is used to convert, into a code value, a raw signal that is output by the photosensitive element and that indicates brightness;
wherein when a horizontal axis is scene reflectance and a vertical axis is normalized code value, a formula of the log curve is as follows:
when T_scene_reflection is greater than 0.0028,
Y_cv
=
0.3145
×
log
1
0
(
5
.
5
5
5
5
56
×
T_scene
_reflection
+
0.07907
)
+
0
.
4
471
;
or
when T_scene_reflection is not greater than 0.0028,
Y_cv
=
11.4695
×
T_scene
_reflection
+
0.0928641
;
and
wherein T_scene_reflection is the scene reflectance, and Y_cv is the normalized code value.
18. The non-transitory computer storage medium according to claim 17 , wherein when the coding depth of the mobile device is 10 bits and the dynamic range is 11 stops, among the plurality of numerical points, a code value corresponding to stop −6 is 128, a code value corresponding to stop −5 is 149, a code value corresponding to stop −4 is 184, a code value corresponding to stop −3 is 235, a code value corresponding to stop −2 is 302, a code value corresponding to stop −1 is 381, a code value corresponding to stop 0 is 468, a code value corresponding to stop 1 is 560, a code value corresponding to stop 2 is 654, a code value corresponding to stop 3 is 749, a code value corresponding to stop 4 is 845, and a code value corresponding to stop 5 is 942; and
a scene reflectance corresponding to stop 0 is 18%.
19. The non-transitory computer storage medium according to claim 17 , wherein:
when the scene reflectance is 0%, a code value of 8 bits determined based on the log curve is 24, a code value of 10 bits determined based on the log curve is 95, and an IRE value determined based on the log curve is 3.5%;
when the scene reflectance is 18%, a code value of 8 bits determined based on the log curve is 116, a code value of 10 bits determined based on the log curve is 468, and an IRE value determined based on the log curve is 46.1%; or
when the scene reflectance is 600%, a code value of 8 bits determined based on the log curve is 236, a code value of 10 bits determined based on the log curve is 948, and an IRE value determined based on the log curve is 100.9%.