Pixel modification to reduce energy consumption of a display device
A method and device for reducing power consumption of display devices proposes to reduce the total amount of light emitted in a perceptually indistinguishable manner based on the on the human visual sensitivity at the position of a pixel. The visibility of the processing can be made to remain provably below threshold, whereas other techniques may not be able to provide such proof. This is achieved by determining a minimum detectable modulation or a corresponding just-noticeable difference based on frequency intensity information for a pixel representative of how much there is of a set of frequencies at the pixel and a contrast sensitivity function representative of a model of human vision that predicts which contrasts at which frequencies are visible to the human eye. Pixel values may be reduced based on this minimum detectable modulation or just-noticeable difference. The contrast sensitivity function may be given by Barten's model and the frequency intensity information may be based on a hierarchical map built using a discrete wavelet transform or a continuous wavelet transform.
1 . A method comprising:
determining, for a pixel of an image located at a position within an input image, a scaling value based on human visual sensitivity at the position of the pixel; and
scaling a luminance of the pixel by an amount based on the scaling value,
wherein the human visual sensitivity is determined by a pixel map of contrast sensitivities S img as follows:
S
i
m
g
=
S
(
L
,
k
G
⊗
arg
max
u
i
(
CWT
·
S
(
L
,
u
i
)
)
)
wherein CWT is a continuous wavelet transform, L is a pixel map of luminance values of the input image, G is a smoothing kernel, u i are the frequencies defined by levels i of the CWT, and k is a constant representing a second scaling value, and Sis a contrast sensitivity function.
2 . The method of claim 1 , wherein the amount of scaling is equal to the scaling value.
3 . The method of claim 1 , wherein the amount of scaling is smaller than the scaling value.
4 . The method of claim 1 , wherein the amount of scaling is greater than the scaling value.
5 . The method of claim 1 , further comprising displaying, on a screen, an image with scaled luminance.
6 . The method of claim 5 , wherein the screen is based on one or more of an organic light-emitting diode (LED) display technology, a micro-LED technology, a mini-LED technology, micro-electromechanical systems technology, and a liquid crystal display technology with uniform or non-uniform backlight based on one or more of cold cathode fluorescent lamp, LED, mini-LED or micro-LED technologies.
7 . A non-transitory computer-readable medium comprising instructions for, when executed on a processor, performing a method according to claim 1 .
8 . The method of claim 1 , wherein the luminance scaling is determined, for the pixel x, by:
L
scaled
(
x
)
=
L
1
-
f
S
(
x
)
1
+
f
S
(
x
)
wherein f is a modulation factor.
9 . The method of claim 1 , wherein the contrast sensitivity function is using Barten's model.
10 . An apparatus comprising at least one processor configured to:
determine, for a pixel of an image located at a position within an input image, a scaling value based on human visual sensitivity at the position of the pixel; and
scale a luminance of the pixel by an amount based on the scaling value,
wherein the human visual sensitivity is determined by a pixel map of contrast sensitivities S img as follows:
S
i
m
g
=
S
(
L
,
k
G
⊗
arg
max
u
i
(
CWT
·
S
(
L
,
u
i
)
)
)
wherein CWT is a continuous wavelet transform, L is a pixel map of luminance values of the input image, G is a smoothing kernel, u i are the frequencies defined by levels i of the CWT, and k is a constant representing a second scaling value, and Sis a contrast sensitivity function.
11 . The apparatus of claim 10 , further comprising a screen and wherein the processor is further configured to display an image with scaled luminance.
12 . The apparatus of claim 11 , wherein the screen is based on one or more of an organic light-emitting diode (LED) display technology, a micro-LED technology, a mini-LED technology, micro-electromechanical systems technology, and a liquid crystal display technology with uniform or non-uniform backlight based on one or more of cold cathode fluorescent lamp, LED, mini-LED or micro-LED technologies.
13 . The apparatus of claim 10 , being selected in a group comprising a television, a smartphone, a laptop, a camera, and a tablet.
14 . The apparatus of claim 10 , wherein the luminance scaling is determined, for the pixel x, by:
L
scaled
(
x
)
=
L
1
-
f
S
(
x
)
1
+
f
S
(
x
)
wherein f is a modulation factor.
15 . The apparatus of claim 10 , wherein the contrast sensitivity function is using Barten's model.