Image correcting device, method for creating corrected image, correction table creating device, method for creating correction table, program for creating correction table, and program for creating corrected image
View Patent ↗An image correcting device includes an image input section, image storage section, correction table storage section, geometry correcting section subjecting an input image to geometrical correction based on a correction table, and image output section outputting the input image as a corrected image. The table is created by: calculating a pair of angles (θ, φ) corresponding to each pixel position on the output image as the corrected image; calculating a light direction based on an intersection line between a plane obtained by rotating a YZ plane by angle θ about Y axis and that by rotating an XZ plane by angle φ about X axis, in three dimensional Cartesian coordinate system with origin at a projection center of the input image; calculating a position on the input image corresponding to the light direction, as a resampling position; and associating the resampling position with the pixel position on the output image.
1. An image correcting device for creating a corrected image through geometrical correction of an input image, comprising:
an input interface configured to input the input image;
a memory configured to store the input image;
a geometrical correcting circuit configured to subject the input image stored in the memory to geometrical correction by: calculating a pair of angles (θ, φ) which corresponds to each pixel position (u, v) on an output image as the corrected image; calculating a light direction (X, Y, Z) based on a line of intersection between a plane obtained by rotating a YZ plane by the angle θ about Y axis and a plane obtained by rotating an XZ plane by the angle φ about X axis, in a three dimensional Cartesian coordinate system with an origin at a projection center of the input image; calculating a position on the input image corresponding to the light direction, as a resampling position; and associating the resampling position with the pixel position on the output image; and
an output interface configured to output the input image corrected by the geometrical correcting circuit, as the corrected image,
wherein a ratio of a first angle change rate of each of the angles (θ, φ) at the edge of the output image to a second angle change rate of each of the angles (θ, φ) at the center of the output image is within a predetermined numerical range.
2. An image correcting device according to claim 1 , wherein the ratio of the first angle change rate to the second angle change rate is equal to or greater than 0.84 and less than 1.
3. An image correcting device according to claim 1 , wherein the angle θ and the angle φ are determined by the expressions
θ
=
f
(
u
)
=
π
2
·
u
-
u
c
w
and
ϕ
=
g
(
v
)
=
π
2
·
v
-
v
c
w
,
wherein (u c , v c ) are the pixel position coordinates of the center position of the output image, and w is a normalization constant,
and the light direction coordinates X, Y, Z are determined by the expressions
X
=
X
0
N
,
Y
=
Y
0
N
,
Z
=
Z
0
N
,
X
0
=
sin
θ
·
cos
ϕ
,
Y
0
=
cos
θ
·
sin
ϕ
,
Z
0
=
cos
θ
·
cos
ϕ
,
and
N
=
X
0
2
+
Y
0
2
+
Z
0
2
.
4. A method of creating a corrected image through geometrical correction of an input image, comprising the steps of:
inputting the input image;
storing the input image;
subjecting the input image stored in the image storage section to geometrical correction by: calculating a pair of angles (θ, φ) which corresponds to each pixel position (u, v) on an output image as the corrected image; calculating a light direction (X, Y, Z) based on a line of intersection between a plane obtained by rotating a YZ plane by the angle θ about Y axis and a plane obtained by rotating an XZ plane by the angle φ about X axis, in a three dimensional Cartesian coordinate system with an origin at a projection center of the input image; calculating a position on the input image corresponding to the light direction, as a resampling position; and associating the resampling position with the pixel position on the output image; and
outputting the input image corrected in the step of geometrical correction as the corrected image,
wherein a ratio of a first angle change rate of each of the angles (θ, φ) at the edge of the output image to a second angle change rate of each of the angles (θ, φ) at the center of the output image is within a predetermined numerical range.
5. A non-transitory computer-readable medium containing computer program instructions for creating a corrected image for executing the method according to claim 4 .
6. A method according to claim 4 , wherein the ratio of the first angle change rate to the second angle change rate is equal to or greater than 0.84 and less than 1.
7. A method according to claim 4 , wherein the angle θ and the angle φ are determined by the expressions
θ
=
f
(
u
)
=
π
2
·
u
-
u
c
w
and
ϕ
=
g
(
v
)
=
π
2
·
v
-
v
c
w
,
wherein (u c , v c ) are the pixel position coordinates of the center position of the output image, and w is a normalization constant,
and the light direction coordinates X, Y, Z are determined by the expressions
X
=
X
0
N
,
Y
=
Y
0
N
,
Z
=
Z
0
N
,
X
0
=
sin
θ
·
cos
ϕ
,
Y
0
=
cos
θ
·
sin
ϕ
,
Z
0
=
cos
θ
·
cos
ϕ
,
and
N
=
X
0
2
+
Y
0
2
+
Z
0
2
.