21/11/15
21/11/15 Duong Anh Duc - Digital Image Processing
Duong Anh Duc - Digital Image Processing 1
1
Digital Image Processing
Image Restoration
Image Restoration
21/11/15
21/11/15 Duong Anh Duc - Digital Image Processing
Duong Anh Duc - Digital Image Processing 2
2
Image Restoration
Image Restoration
Most images obtained by optical, electronic, or
Most images obtained by optical, electronic, or
electro-optic means is likely to be degraded.
electro-optic means is likely to be degraded.
The degradation can be due to camera
The degradation can be due to camera
misfocus, relative motion between camera and
misfocus, relative motion between camera and
object, noise in electronic sensors, atmospheric
object, noise in electronic sensors, atmospheric
turbulence, etc.
turbulence, etc.
The goal of image restoration is to obtain a
The goal of image restoration is to obtain a
relatively “clean” image from the degraded
relatively “clean” image from the degraded
observation.
observation.
It involves techniques like filtering, noise reduction
It involves techniques like filtering, noise reduction
etc.
etc.
21/11/15
21/11/15 Duong Anh Duc - Digital Image Processing
Duong Anh Duc - Digital Image Processing 3
3
Restoration vs. Enhancement
Restoration vs. Enhancement
Restoration
Restoration:
:
A process that attempts to reconstruct or recover an
A process that attempts to reconstruct or recover an
image that has been degraded by using some prior
image that has been degraded by using some prior
knowledge of the degradation phenomenon.
knowledge of the degradation phenomenon.
Involves modeling the degradation process and
Involves modeling the degradation process and
applying the inverse process to recover the original
applying the inverse process to recover the original
image.
image.
A criterion for “goodness” is required that will recover
A criterion for “goodness” is required that will recover
the image in an optimal fashion with respect to that
the image in an optimal fashion with respect to that
criterion.
criterion.
Ex. Removal of blur by applying a deblurring function.
Ex. Removal of blur by applying a deblurring function.
21/11/15
21/11/15 Duong Anh Duc - Digital Image Processing
Duong Anh Duc - Digital Image Processing 4
4
Restoration vs. Enhancement
Restoration vs. Enhancement
Enhancement
Enhancement:
:
Manipulating an image in order to take
Manipulating an image in order to take
advantage of the psychophysics of the human
advantage of the psychophysics of the human
visual system.
visual system.
Techniques are usually “heuristic.”
Techniques are usually “heuristic.”
Ex. Contrast stretching, histogram equalization.
Ex. Contrast stretching, histogram equalization.
21/11/15
21/11/15 Duong Anh Duc - Digital Image Processing
Duong Anh Duc - Digital Image Processing 5
5
(Linear) Degradation Model
(Linear) Degradation Model
g(m,n) = f(m,n)*h(m,n) +
g(m,n) = f(m,n)*h(m,n) +
(m,n)
(m,n)
G(u,v) = H(u,v)F(u,v) + N(u,v)
G(u,v) = H(u,v)F(u,v) + N(u,v)
f(m,n)
f(m,n) : Degradation free image
: Degradation free image
g(m,n)
g(m,n) : Observed image
: Observed image
h(m,n)
h(m,n) : PSS of blur degradation
: PSS of blur degradation
(m,n)
(m,n) : Additive Noise
: Additive Noise