Spectral Feature Extraction - Cornell University

CEE 615: Digital Image Processing 6
W. Philpot, Cornell University
Example 2: Spectral Addition:
Adding gray values from different spectral bands.
2-band case: k' = a 0 + a 1 k 1 + a 2 k 2
• The vector, a = (a 1 ,a 2 ), defines the direction of changing gray value.
• The coefficients may be defined by choosing
(k 11 , k 21 ) => k min = minimum gray value in the new image, and
(k 12 , k 22 ) => k max = maximum gray value in the new image.
The coefficients are:
a 2 = m a 1 where: m = slope of the best fit straight line.
= (k 22 -k 21 )/(k 12 -k 11 )
a
1
=
k
max
− k
min
( k − k ) + m( k − k )
12 11 22 21
a 0 = k min – a 1 (k 11 + m k 21 )
• Spectral addition can be regarded as a partitioning of the measurement space.
• The space is partitioned into plane-parallel regions which are perpendicular to the direction
of the coefficient vector a = (a 1 , a 2 ).
• Intensity information extraction will be optimized if the coefficient vector, is parallel to the
direction of correlation.