1.Smooth an image over a neighborhood of pixels
2.Median filtering as a special non-linear filtering and smoothing approach
Determine the average of neighboring values
1. moving average [1 1 1 1 1] x 1/5
2. weighted moving average [1 4 6 4 1] x 1/16
smoothing process over an image using averages
some observation
-small image “rubbed” over bigger image
kernel h(i,j)
3×3 area around each original pixel used (i.e., neighborhood size k=1)
window size is 2k+1, therefore our wind is 3×3
G[i,j] = 1/(2k+1)^2 ΣΣF[i+u,j+v]
Special Case: Median Filtering
F[i,j]
median and average is changed value
Apply median filter to all 3*3 regions over the whole image
Median filtering: nonlinear operation often used in image processing
reduces noise, but
preserves edges(sharp lines!)
main idea: use median of all pixel in area, instead of mean
Median Filtering for noise removal
