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Thanikaiselvan V
Assistant Professor SeniorSENSE
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V THANIKAISELVAN | ASST PROF SR | SENSE
Called as averaging filters low pass filters Replacing of every pixel in an image by the
average of the gray levels in the neighborhood
defined by the filter mask. This process results in an image with reduced
sharp transitions in gray levels.
Random noise will be reduced Box filters , weighted average filters(second mask)
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V THANIKAISELVAN | ASST PROF SR | SENSE
Order statistics filters are non linear spatial filterswhose response is based on ordering (ranking)
the pixels contained in the image area
encompassed by the filter, and replacing the valueof the center pixel with the value determined by
the ranking result.
Median filters.
Impulse noise , salt and pepper noise removed
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Laplacian filters Isotropic filters Rotation invariant
The simplest isotropic derivative operator is the
laplacian, which for a function f(x,y) of twovariables, is defined as
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Second order derivative for x direction
Second order derivative for y direction
two dimensional laplacian is obtained by summing the
above two components
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- =
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First derivative in image processing isimplemented as
Magnitude of gradient vector is referred to as
Gradient
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V THANIKAISELVAN | ASST PROF SR | SENSE
The simplest approximation in first orderderivative is (Proposed by Robert-1965)
We compute the gradient as
Mask is given in the figure, this is called as
Robert Cross gradient operator
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V THANIKAISELVAN | ASST PROF SR | SENSE
We are interested in 3 x 3 mask
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Sober operator (c and D)
Sum is zero, then constant area pixel will get zero
as gradient.
