(0,0) (0,0) (1,1)
3x3 5x5
Sharpening, also referred to as crispening, emphasizes the details in an image. Sharpening an image will increase its contrast.
1)}, ( ) 1, ( 1), ( ) 1, ( { 4 1 ), ( ), ( ) :, ( 0 ),, ( ), ( ), ( + + + + + = > + = n m u n m u n m u n m u n m u n m g Laplacian n m g where n m g n m u n m v λ λ Signal Low-pass High-pass (1) (2) (3) (1)+λ(3)
h h HP BP ( m, n) = u( m, n) h ( m, n) = LP ( m, n) hl ( m, n) h ( m, n) 1 L2 u ( m, n) Spatial V LP ( m, n) u( m, n) averaging LPF V HP + ( m, n) (a) Spatial low-pass filter (b) Spatial high-pass filter u( m, n) LPF ( m, h L 1 n ) + V BP ( m, n) LPF ( m, h L 2 n (c) Spatial band-pass filter(dog) )
1 2 1 2 5 1 1 2 1 1 1 1 1 9 1 1 1 1 0 1 0 1 5 1 0 1 0
Sharpening an image is based on the high filter. A highpass filter will remove the low frequency components and show only high detail. HPF mask 1/ 9 1/ 9 1/ 9 1/ 9 8/ 9 1/ 9 1/ 1/ 1/ 9 9 9
High - Boost = αoriginal Lowpass α=1, α>1, 1/ 9 1/ 9 1/ 9 1/ 9 ω / 9 1/ 9 1/ 9 1/ 9 1/ 9, ω = 9α 1
α
), ( ), ( tan = ), ( + y) (x, y) (x, + y) (x, = y) (x, r c -1 c r 2 c 2 r y x H y x H y x H H H H H θ