Device and method of removing chromatic aberration in image
View Patent ↗A device and method of removing chromatic aberration which occurs in an image generated by capturing a target subject. The chromatic aberration removing device includes a chromatic aberration region detecting unit which detects a chromatic aberration occurrence region in an input image, a coefficient calculating unit which calculates a minimizing pixel value which minimizes a difference between sizes, numbers of pixels or intensities of edges of red, green, and blue (RGB) channels of the chromatic aberration occurrence region, a chroma signal processing unit which removes chromatic aberration in the chromatic aberration occurrence region, and a purple fringing removing unit which removes purple fringing.
1. A chromatic aberration removing device comprising:
a chromatic aberration region detecting unit which detects a chromatic aberration occurrence region in an input image;
a coefficient calculating unit which calculates a minimizing pixel value which minimizes a difference between sizes, numbers of pixels or intensities of edges of red, green, and blue (RGB) channels of the chromatic aberration occurrence region; and
a chroma signal processing unit which removes chromatic aberration in the chromatic aberration occurrence region by using the minimizing pixel value and chroma values of pixels adjacent to the chromatic aberration occurrence region.
2. The chromatic aberration removing device of claim 1 , wherein the coefficient calculating unit estimates a minimizing coefficient which minimizes a difference between a size, number or intensity of pixels of the edge of the R channel and a size, number or intensity of pixels of the edge of the B channel, and then, calculates the minimizing pixel value by using the minimizing coefficient.
3. The chromatic aberration removing device of claim 2 , wherein the minimizing pixel value is a pixel value (i′,j′) that satisfies expressions of min∥ I G ( i,j )− I R ( i′,j ′)∥, and min∥ I G ( i,j )− I B ( i′,j ′)∥, where ( i,j )εEdge region, and is calculated by using an equation of ( i′,j ′)=( i,j )( a 0 +a 1 r ( i,j )+ a 1 r ( i,j ) 2 +a 1 r ( i,j ) 3 ),
where a 0 , a 1 , a 2 , a 3 indicate size coefficients between the RGB channels.
4. The chromatic aberration removing device of claim 2 , wherein the chroma signal processing unit comprises:
a channel moving unit which moves the edge of the R channel and the edge of the B channel in the chromatic aberration occurrence region to a position corresponding to the minimizing pixel value; and
a chroma interpolating unit which obtains chroma values which are estimated in a case where the chromatic aberration does not occur in pixels of the RB channels included in the chromatic aberration occurrence region, by using chroma values of pixels which are from among adjacent pixels of the pixels of the RB channels included in the chromatic aberration occurrence region and which are not affected by the chromatic aberration, and replaces chroma values of the pixels of the RB channels in the chromatic aberration occurrence region with the estimated chroma values.
5. The chromatic aberration removing device of claim 4 , wherein each of the estimated chroma values I′ Cb (i,j) is calculated by using an equation of
I
Cb
′
(
i
,
j
)
=
∑
(
p
,
q
)
∈
N
S
(
p
,
q
)
w
1
(
p
,
q
)
+
w
2
(
p
,
q
)
+
w
3
(
p
,
q
)
I
Cb
(
p
,
q
)
,
where Cb indicates chroma, (i,j) indicate pixels in the chromatic aberration occurrence region, (p,q) indicate the adjacent pixels in the chromatic aberration occurrence region, N indicates an adjacent region around the chromatic aberration occurrence region, S indicates a switch function for weighting and averaging only same chroma from among a plurality of pieces of chroma of the adjacent pixels in the chromatic aberration occurrence region, w1 indicates an absolute value of a difference between slopes of the G and B channels, w2 indicates an absolute value of a slope of a Y channel, and w3 indicates a difference between a Y (luminance) value of a pixel in the chromatic aberration occurrence region and Y values of pixels adjacent to the pixel in the chromatic aberration occurrence region.
6. The chromatic aberration removing device of claim 1 , wherein the chroma signal processing unit comprises:
a channel moving unit which moves the edge of the R channel and the edge of the B channel in the chromatic aberration occurrence region to a position corresponding to the minimizing pixel value; and
a chroma interpolating unit which obtains chroma values which are estimated in a case where the chromatic aberration does not occur in pixels of the RB channels included in the chromatic aberration occurrence region, by using chroma values of pixels which are from among adjacent pixels of the pixels of the RB channels included in the chromatic aberration occurrence region and which are not affected by the chromatic aberration, and replaces chroma values of the pixels of the RB channels in the chromatic aberration occurrence region with the estimated chroma values.
7. The chromatic aberration removing device of claim 1 , further comprising:
a purple fringing removing unit which removes purple fringing by using given pixel values as weights,
wherein the given pixel values comprise a pixel value which is restored from pixels adjacent to pixels having a purple fringing chroma characteristic, and a pixel value which is interpolated from a previous image frame of an image frame having the purple fringing.
8. The chromatic aberration removing device of claim 7 , wherein the coefficient calculating unit estimates a minimizing coefficient which minimizes a difference between a size, number or intensity of pixels of the edge of the R channel and a size, number or intensity of pixels of the edge of the B channel, and then, calculates the minimizing pixel value by using the coefficient.
9. The chromatic aberration removing device of claim 8 , wherein the chroma signal processing unit comprises:
a channel moving unit which moves the edge of the R channel and the edge of the B channel in the chromatic aberration occurrence region to a position corresponding to the minimizing pixel value; and
a chroma interpolating unit which obtains chroma values which are estimated in a case where the chromatic aberration does not occur in pixels of the RB channels included in the chromatic aberration occurrence region, by using chroma values of pixels which are from among adjacent pixels of the pixels of the RB channels included in the chromatic aberration occurrence region and which are not affected by the chromatic aberration, and replaces chroma values of the pixels of the RB channels in the chromatic aberration occurrence region with the estimated chroma values.
10. The chromatic aberration removing device of claim 7 , wherein a purple fringing occurrence region in which the purple fringing occurs is defined as I Cb >0 and I Cr >−th and I Cb >I Cr , the purple fringing occurrence region and values of adjacent pixels around the purple fringing occurrence region are defined as I Cb (i,j)>I Cb (p,q) and I Cb (p,q)≦I Cr (p,q), and an interpolated chroma value I′Cb(i,j) of each of pixels in the purple fringing occurrence region is calculated by using an equation of
I
Cb
′
(
i
,
j
)
=
∑
(
p
,
q
)
∈
N
′
w
4
(
p
,
q
)
I
Cb
(
p
,
q
)
,
where, w4 indicates a weight according to a distance between the pixels in the purple fringing occurrence region and the adjacent pixels in the purple fringing occurrence region, and N′ indicates a region in which the purple fringing does not occur).
11. A method of removing chromatic aberration, the method comprising:
(a) detecting a region of an input image in which chromatic aberration occurs;
(b) estimating a minimizing coefficient which minimizes a difference between a size, number or intensity of pixels of an edge of a red (R) channel and a size, number or intensity of pixels of an edge of a blue (B) channel;
(c) calculating, using a processor and the estimated coefficient, a minimizing pixel value which minimizes a difference between sizes, numbers of pixels or intensities of edges of red, green and blue (RGB) channels;
(d) moving the edges of the R channels and the edges of the B channels in the chromatic aberration occurrence region, to a position which corresponds to the minimizing pixel value; and
(e) obtaining chroma values which are estimated in a case where the chromatic aberration does not occur in pixels of the RB channels included in the chromatic aberration occurrence region, by using chroma values of pixels which are from among adjacent pixels of the pixels of the RB channels included in the chromatic aberration occurrence region and which are not affected by the chromatic aberration, and then, replaces chroma values of the pixels of the RB channels included in the chromatic aberration occurrence region with the estimated chroma values.
12. The method of claim 11 , further comprising:
(f) removing purple fringing by using given pixel values as weights, wherein the given pixel values comprise a pixel value which is restored from pixels adjacent to pixels having a purple fringing chroma characteristic, and a pixel value which is interpolated from a previous image frame of an image frame having the purple fringing.