Image Processing Reference
In-Depth Information
1.5 Interpolation based on linear filtering
The elementary primitive of color interpolation is the algorithm of a bilinear filtration which
is applied to each channel independently. For channel G ("green") the filter kernel
represents:
010
1
k
1
4
1
,
4
010
And for channels "red" and "blue" accordingly:
121
.
Other algorithm of the general application is bicubic interpolation, at which kernels for
channels of the primary colors are the following:
1
k
242
4
121
00 0 1 0 00
00 9 0 900
090 10 90
1
k
1
0
81
256
81
0
1
,
G
256
090 10 90
00 9 0 900
00 0 1 0 00
10 9 6901
000 0 000
9
0
81
144
81
0
9
1
k
16
0
144
256
81
0
16
.
R,B
256
9 0 81 144 81 0 9
000 0 000
1 0 9 690 1
1.6 Interpolation based on color hue constance
Color interpolation can be led also on the basis of assumptions of persistence of color tone in
localized areas. Generally, selection of a color tone constant is possible considering property
of orderliness of colors within a color circle. Interpolation of a constant of the color tone,
offered in [7], is one of the most widespread methods used up to professional cameras. The
constant of color tone is defined as a difference between the main color components. At the
first stage the algorithm interpolates green channel
G
, using the bilinear method considered
earlier. For an estimation of an error of "red" pixels bilinear interpolation of a
difference
R( ) G( )
, which then incremented by
G(
. The channel "blue" is recovered
similarly.
