Methods for obtaining a three-band intrinsic image from a single input image
View Patent ↗Various embodiments of the present invention related to methods for obtaining shadow invariant and shadow-shading invariant images from a single camera image taken with a narrow-band camera sensor and assuming Plankian illuminating conditions.
1. A method performed by a computing device for determining a shadow invariant image from input image data, the method comprising:
receiving input image data associated with an image of a scene from an image recording device, each pixel of the input image data including pixel intensities associated with three or more primary colors;
calculating a shadow invariant intensity for each pixel intensity of each pixel; and
displaying a color shadow invariant image of the scene by displaying the shadow invariant intensities of each pixel on a display device.
2. The method of claim 1 wherein receiving input image data further comprises uploading data from the image recording device to the computing device.
3. The method of claim 1 wherein calculating the shadow invariant intensity for each pixel intensity further comprises computing:
P
u
=
L
u
+
κ
∑
i
∈
{
r
,
g
,
b
}
λ
i
λ
u
L
i
-
λ
m
λ
u
L
m
1
-
3
κ
where L u is the logarithm of the pixel intensity I u ;
κ is a constant other than ⅓; and
λ u is a wavelength of the primary color u.
4. The method of claim 3 wherein calculating the shadow invariant intensity for each pixel intensity further comprises computing:
L
u
=
log
(
I
u
)
=
log
[
(
ρ
d
S
(
λ
u
)
+
ρ
s
)
q
u
2
hc
2
λ
u
5
]
+
(
-
hc
λ
u
kT
)
where I u is a pixel intensity associated with primary color u;
h is Plank's constant;
c is the speed of light in a vacuum;
k is Boltzmann's constant;
T is the color temperature
ρ d and ρ s are geometric factors associated with diffuse and specular reflection of each pixel;
q u is the magnitude of the sensor response associated with the pixel; and
S(λ) is a surface reflectance spectrum.
5. The method of claim 1 further comprises calibrating the image recording device.
6. The method of claim 5 wherein calibrating the image recording device further comprises calculating the relative wavelength
λ
u
′
=
1
/
(
L
u
(
x
)
-
L
u
(
y
)
)
∑
i
∈
{
r
,
g
,
b
}
1
/
(
L
i
(
x
)
-
L
i
(
y
)
)
for each shadow and non-shadow pixel pair x and y, respectively, within a uniform color distribution.
7. The method of claim 1 wherein the image recording device further comprises a digital camera, a mobile phone, a camera phone, a personal digital assistant, a camcorder or any device that digitally captures images via an electronic image sensor and can store the image data in memory.
8. The method of claim 1 wherein the computing device further comprises a desktop computer, a laptop computer, a portable computer, a display system, a television, a computer monitor, a navigation system, a portable media player, a personal digital assistant, a game console, a handheld electronic device, an embedded electronic device, or an appliance.
9. The method of claim 1 wherein calculating the shadow invariant image further comprises assuming Plankian illuminating conditions.
10. A method performed by a computing device for determining a shadow-shading invariant image from input image data, the method comprising:
receiving input image data associated with an image of a scene from a image recording device, each pixel of the input image data including pixel intensities associated with three or more primary colors;
calculating a shadow-shading invariant intensity for each pixel intensity of each pixel; and
displaying a color shadow-shading invariant image of the scene by displaying the shadow-shading invariant intensities of each pixel on a display device.
11. The method of claim 10 wherein receiving input image data further comprises uploading data from the image recording device to the computing device.
12. The method of claim 10 wherein calculating the shadow-shading invariant intensity for each pixel intensity further comprises calculating:
p
u
=
L
u
-
λ
m
λ
u
L
m
+
κ
(
∑
i
∈
{
r
,
g
,
b
}
(
λ
i
λ
u
L
i
)
-
3
L
u
)
∑
i
∈
{
r
,
g
,
b
}
(
λ
i
λ
u
L
i
)
-
3
λ
m
λ
u
L
m
where L u is the logarithm of the pixel intensity I u ;
κ is a constant other than ⅓; and
λ u is a wavelength of the primary color u.
13. The method of claim 12 wherein calculating the shadow-shading invariant intensity for each pixel intensity further comprises calculating:
L
u
=
log
(
I
u
)
=
log
[
(
ρ
d
S
(
λ
u
)
+
ρ
s
)
q
u
2
hc
2
λ
u
2
]
+
(
-
hc
λ
u
kT
)
where I u is a pixel intensity associated with primary color u;
h is Plank's constant;
c is the speed of light in a vacuum;
k is Boltzmann's constant;
T is the color temperature
ρ d and ρ s are geometric factors associated with diffuse and specular reflection of each pixel;
q u is the magnitude of the sensor response associated with the pixel; and
S(λ) is a surface reflectance spectrum.
14. The method of claim 10 further comprises calibrating the image recording device.
15. The method of claim 14 wherein calibrating the image recording device further comprises calculating the relative wavelength
λ
u
′
=
1
/
(
L
u
(
x
)
-
L
u
(
y
)
)
∑
i
∈
{
r
,
g
,
b
}
1
/
(
L
i
(
x
)
-
L
i
(
y
)
)
for each shadow and non-shadow pixel pair x and y, respectively, within a uniform color distribution.
16. The method of claim 10 wherein the image recording device further comprises a digital camera, a mobile phone, a camera phone, a personal digital assistant, a camcorder or any device that digitally captures images via an electronic image sensor and can store the image data in memory.
17. The method of claim 10 wherein the computing device further comprises a desktop computer, a laptop computer, a portable computer, a display system, a television, a computer monitor, a navigation system, a portable media player, a personal digital assistant, a game console, a handheld electronic device, an embedded electronic device, or an appliance.
18. The method of claim 10 wherein calculating the shadow-shading invariant image further comprises assuming Plankian illuminating conditions.