Method and device for reconstructing a color image
A method for reconstructing a color image from a sensor which comprises a plurality of pixels arranged in a matrix of rows and columns is provided. The sensor is provided with a color filter array such that each pixel corresponds to one of three basic colors. The three basic colors are provided on the sensor in a predetermined pattern. The sensor outputs a detected value for each of the plurality of pixels. The method comprises the steps: for each of the plurality of pixels: accepting a detected value obtained for the corresponding one of the three basic colors and, for each of the respective two other basic colors, calculating a vertical interpolation value and a horizontal interpolation value and selecting either the vertical interpolation value or the horizontal interpolation value; outputting the accepted detected value and the selected interpolation values. The vertical interpolation and the horizontal interpolation are calculated based on the detected values for pixels in a 5×5 pixel environment around the respective pixel.
1. A method for reconstructing a color image from a sensor comprising a plurality of pixels arranged in a matrix of rows and columns, the sensor being provided with a color filter array such that each pixel corresponds to one of three basic colors, the three basic colors being provided on the sensor in a predetermined pattern; wherein the sensor outputs a detected value for each of the plurality of pixels;
the method comprising:
for each of the plurality of pixels:
accepting a detected value obtained for the corresponding one of the three basic colors and, for each of the respective two other basic colors, calculating a vertical interpolation value and a horizontal interpolation value and selecting either the vertical interpolation value or the horizontal interpolation value comprises
calculating a horizontal edge indicator taking into account the horizontal interpolation value;
calculating a vertical edge indicator taking into account the vertical interpolation value; and
comparing the horizontal edge indicator and the vertical edge indicator where the horizontal edge indicator is calculated according to the equation
class x =|a 33 −a 31 |+|a 33 −a 35 |+|B 33 −b 32 |+|B 33 −b 34 |
with the pixels in the 5×5 pixel environment being defined as
[
p
11
p
12
p
13
p
14
p
15
p
21
p
22
p
23
p
24
p
25
p
31
p
32
p
33
p
34
p
35
p
41
p
42
p
43
p
44
p
45
p
51
p
52
p
53
p
54
p
55
]
the pixel p 33 being the pixel for which interpolation is performed, a ij and b ij being corresponding detected values for pixels p ij , and B 33 being the horizontal interpolation value for pixel p 33 ;
outputting the accepted detected value and the selected interpolation values;
wherein the vertical interpolation value and the horizontal interpolation value are calculated based on the detected values for pixels in a 5×5 pixel environment around the respective pixel.
2. The method according to claim 1 , wherein the vertical edge indicator is calculated according to the equation
class y =|c 33 −c 13 |+|c 33 −c 53 |+|D 33 −d 23 |+|D 33 −d 43 |
with c ij and d ij being corresponding detected values for pixels p ij and D 33 being the vertical interpolation value for pixel p 33 .
3. The method according to claim 2 , wherein the vertical interpolation value is selected if the following equation is fulfilled:
class y <class x ,
and else the horizontal interpolation value is selected.
4. A device for reconstructing a color image, the device comprising:
a sensor comprising a plurality of pixels arranged in a matrix of rows and columns, the sensor being provided with a color filter array such that each pixel corresponds to one of three basic colors, the three basic colors being provided on the sensor in a predetermined pattern; the sensor being adapted to output a detected value for each of the plurality of pixels;
a plurality of line memories; and
a reconstruction unit adapted to perform the following operations for each of the plurality of pixels wherein the reconstruction unit comprises a classification unit adapted to calculate a horizontal edge indicator taking into account the horizontal interpolation value and to calculate a vertical edge indicator taking into account the vertical interpolation value and the horizontal edge indicator is calculated according to the equation
class x =|a 33 −a 31 |+|a 33 −a 35 |+|B 33 −b 32 |+|B 33 −b 34 |
with the pixels in the 5×5 pixel environment being defined as
[
p
11
p
12
p
13
p
14
p
15
p
21
p
22
p
23
p
24
p
25
p
31
p
32
p
33
p
34
p
35
p
41
p
42
p
43
p
44
p
45
p
51
p
52
p
53
p
54
p
55
]
the pixel p 33 being the pixel for which interpolation is performed, a ij and b ij being corresponding detected values for pixels p ij , and B 33 being the horizontal interpolation value for pixel p 33 :
accepting a detected value obtained for the corresponding one of the three basic colors and, for each of the respective two other basic colors, calculating a vertical interpolation value and a horizontal interpolation value and selecting either the vertical interpolation value or the horizontal interpolation value;
outputting the accepted detected value and the selected interpolation values;
wherein the vertical interpolation value and the horizontal interpolation value are calculated based on the detected values for pixels in a 5×5 pixel environment that is provided by the plurality of line memories to the reconstruction unit around the respective pixel.
5. The device of claim 4 , wherein the vertical edge indicator is calculated according to the equation
class y =|c 33 −c 13 |+|c 33 −c 53 |+|D 33 −d 23 |+|D 33 −d 43 |
with c ij and d ij being corresponding detected values for pixels p ij and D 33 being the vertical interpolation value for pixel p 33 .
6. The device of claim 5 , wherein the vertical interpolation value is selected if the following equation is fulfilled:
class y <class y ,
and else the horizontal interpolation value is selected.