This document discusses the Fourier transformation, including:
1) It defines continuous and discrete Fourier transformations and their properties such as separability, translation, periodicity, and convolution.
2) The fast Fourier transformation (FFT) improves the computational complexity of the discrete Fourier transformation from O(N^2) to O(NlogN).
3) FFT works by rewriting the DFT calculation in a way that exploits symmetry and reduces redundant computations.
Digital Image Processing denotes the process of digital images with the use of digital computer. Digital images are contains various types of noises which are reduces the quality of images. Noises can be removed by various enhancement techniques. Image smoothing is a key technology of image enhancement, which can remove noise in images.
Wavelet transform is one of the important methods of compressing image data so that it takes up less memory. Wavelet based compression techniques have advantages such as multi-resolution, scalability and tolerable degradation over other techniques.
its very useful for students.
Sharpening process in spatial domain
Direct Manipulation of image Pixels.
The objective of Sharpening is to highlight transitions in intensity
The image blurring is accomplished by pixel averaging in a neighborhood.
Since averaging is analogous to integration.
Prepared by
M. Sahaya Pretha
Department of Computer Science and Engineering,
MS University, Tirunelveli Dist, Tamilnadu.
Digital Image Processing denotes the process of digital images with the use of digital computer. Digital images are contains various types of noises which are reduces the quality of images. Noises can be removed by various enhancement techniques. Image smoothing is a key technology of image enhancement, which can remove noise in images.
Wavelet transform is one of the important methods of compressing image data so that it takes up less memory. Wavelet based compression techniques have advantages such as multi-resolution, scalability and tolerable degradation over other techniques.
its very useful for students.
Sharpening process in spatial domain
Direct Manipulation of image Pixels.
The objective of Sharpening is to highlight transitions in intensity
The image blurring is accomplished by pixel averaging in a neighborhood.
Since averaging is analogous to integration.
Prepared by
M. Sahaya Pretha
Department of Computer Science and Engineering,
MS University, Tirunelveli Dist, Tamilnadu.
WEBINAR ON FUNDAMENTALS OF DIGITAL IMAGE PROCESSING DURING COVID LOCK DOWN by by K.Vijay Anand , Associate Professor, Department of Electronics and Instrumentation Engineering , R.M.K Engineering College, Tamil Nadu , India
What is Fourier Transform
Spatial to Frequency Domain
Fourier Transform
Forward Fourier and Inverse Fourier transforms
Properties of Fourier Transforms
Fourier Transformation in Image processing
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Adjusting primitives for graph : SHORT REPORT / NOTESSubhajit Sahu
Graph algorithms, like PageRank Compressed Sparse Row (CSR) is an adjacency-list based graph representation that is
Multiply with different modes (map)
1. Performance of sequential execution based vs OpenMP based vector multiply.
2. Comparing various launch configs for CUDA based vector multiply.
Sum with different storage types (reduce)
1. Performance of vector element sum using float vs bfloat16 as the storage type.
Sum with different modes (reduce)
1. Performance of sequential execution based vs OpenMP based vector element sum.
2. Performance of memcpy vs in-place based CUDA based vector element sum.
3. Comparing various launch configs for CUDA based vector element sum (memcpy).
4. Comparing various launch configs for CUDA based vector element sum (in-place).
Sum with in-place strategies of CUDA mode (reduce)
1. Comparing various launch configs for CUDA based vector element sum (in-place).
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2. Fourier Transformation
Continuous & Discrete Fourier Transformation
Properties of Fourier Transformation
Fast Fourier Transformation
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3. Fourier Transformation ( 1-D Continuous
Signal)
Let f(x) is a continuous function of some variable then the Fourier
transformation of f(x) is F(u)
Here f(x) must be continuous & integralable
Inverse Fourier Transformation:
F(u) is a Fourier transform of signal f(x) so after inverse Fourier
transformation of F(u) we get f(x)
Fourier Transformation :
4. Fourier Transformation ( 1-D Continuous
Signal)
Fourier Transformation Pair
F(u) → Fourier Transform of signal f(x)
F(x) → Original Signal or Inverse Fourier Transform of F(u)
Here F(u) is a complex function contains real part & imaginary part
F(u) = R(u) + jI(u)
We have
Fourier Spectrum:
The phase angle:
Power Spectrum :
5. Fourier Transformation ( 2-D Continuous
Signal)
Forward Fourier Transformation:
Let f(x,y) is 2 dimensional signal with 2 variable
Inverse (Backward) Fourier Transformation:
7. 2-D Discrete Fourier
Transformation
Forward 2D discrete Fourier Transformation:
Let we have an Image of size MxN then F(u,v) is the F T of image f(x,y)
Where variable u = 0, 1, 2, …., M-1 and v = 0, 1, 2, …., N-1
Inverse (Backward) Fourier Transformation :
Where variable x = 0, 1, 2, …., M-1 and y = 0, 1, 2, …., N-1
8. For a square image i.e. M = N and the
Fourier Transformation Pair is as follows
2-D Discrete Fourier
Transformation
9. Discrete F T Result
Original
Image
Transformed
Image
DFT
IDFT
12. Seperability
The separbility property says that we can do 2D Fourier transformation as two
1 D Fourier Transformation
Inverse Fourier Transform
X represent row of
image so x is fixed
Fourier Transformation
along row
13. Seperability Cont…
2D Inverse Fourier transformation can also be viewed as two 1 D Inverse
Fourier Transformation
IDFT along rows
IDFT along columns
Advantage of Seperability:
Operation become much simpler and less time complexity
14. Seperability Concept
f(x,y) → Original
Image
F(x,v) → Intermediate
Coefficient of F T along row
F(x,v) → Intermediate
Coefficient of F T along row
Row Transform
Column Transform
F(u,v) → Complete
Coefficient of F T
N-1
N-1
(0,0)
N-1
N-1
(0,0)
N-1
N-1
(0,0)N-1
N-1
(0,0)
17. Periodicity
Periodicity property says that the Discrete Fourier Transform and Inverse
Discrete Fourier Transform are periodic with a period N
Proof:
So we can say that Discrete Fourier
Transform is periodic with N
18. Conjugate
If f(x,y) is a real valued function then
F(u,v) = F* (-u, -v)
Where F* indicate it complex conjugate
Now Fourier Spectrum
|F(u,v)| = |F(-u,-v)|
This property help to visualize Fourier
Spectrum
19. Rotation
Let x = rcosθ and y = sinθ
u = wcosø and v = sinø
Then we have
f(x,y) = f(r,θ) in Spatial Domain
F(u,v) = F(w, ø) in Frequency Domain
Now Rotated Image is f(r, θ + θ0 ) and
f(r, θ + θ0 ) ↔ F(w, ø + ø0)
F(w, ø + ø0) is F T of Rotated image
22. Scaling
If a and b are two scaling quantity then
a f(x,y) ↔ a F(u,v)
If f(x,y) is multiplied by scalar quantity a then
its F T is also multiplied by same scalar
quantity
Scaling Individual dimension
23. Convolution:
Convolution in spatial domain is equivalent to
multiplication in frequency domain and vice
versa
Correlation:
Where f* and F* indicate conjugates of f and F
Correlation & Correlation
25. Fast Fourier Transformation
A 2D Fourier transform
Has complexity O(N4
)
For a 1D Discrete F T complexity become O(N2
)
Where we take for simplification. We have N
= 2N
no. of input and we assume N = 2M