KAYA Frame Grabbers Color Geometric Distortion Correction
6
4.1
1-D multi-spectral spatial correction
The corrector compensates spatial distortion along a single image line. The same correction is
applied on all the lines of the captured image.
For every incoming line of “raw” RGB24 pixels, the corrector delivers one line of “corrected”
RGB24 pixels having the same length. In this case, there are 4096 pixels.
The corrector operates on each color plane separately. A different spatial correction can be applied
on each color component: R, G, and B components in this case. This feature allows the correction of
chromatic aberrations.
4.2
Spatial Correction Principle
For each pixel position P along the delivered line of pixels, the corrector delivers, for each
component separately, the estimated pixel component data corresponding to the corrected position
P’ described in the following correction principle:
𝑅
𝑜𝑢𝑡
(𝑃) = 𝑅
𝑖𝑛
(𝑃
R ′
); 𝑃
𝑅 ′
= 𝑃 + 𝑃𝑜𝑓𝑓𝑠𝑒𝑡
R
(𝑃)
𝐺
𝑜𝑢𝑡
(𝑃) = 𝐺
𝑖𝑛
(𝑃
𝐺 ′
); 𝑃
𝐺 ′
= 𝑃 + 𝑃𝑜𝑓𝑓𝑠𝑒𝑡
G
(𝑃)
𝐵
𝑜𝑢𝑡
(𝑃) = 𝐵
𝑖𝑛
(𝑃
𝐵 ′
); 𝑃
𝐵 ′
= 𝑃 + 𝑃𝑜𝑓𝑓𝑠𝑒𝑡
B
(𝑃)
The Position Offset values are specific to each component (R, G, B) and each position P.
4.2.1
Interpolation
The corrector uses linear interpolation between two adjacent pixels to estimate the pixel component
data of the corrected position P’. P’ is a positive value composed of an integer part P’
INT
and a
fractional part P’
FRAC
.
The interpolator estimates the pixel component data using the following formula:
(𝑃′) = (𝑃’
𝐼𝑁𝑇
) ∗ (1 – 𝑃’
𝐹𝑅𝐴𝐶
) + 𝐷𝑎𝑡𝑎(𝑃’
𝐼𝑁𝑇
+ 1) ∗ 𝑃’
𝐹𝑅𝐴𝐶
4.2.2
Operating Limits
The corrector will exhibit some operating limits regarding the Position Offset values:
The range of position values will be restricted to a window of 256 pixels allowing position
offsets in the range of -128 up to +127.
The fractional part is defined in steps of 1/256th.
Corrector will affect maximum of 4096 pixels.
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Color Geometric Distortion Correction
