The document discusses various image transforms. It begins by explaining why transforms are used, such as for fast computation and obtaining conceptual insights. It then introduces image transforms as unitary matrices that represent images using a discrete set of basis images. It proceeds to describe one-dimensional orthogonal and unitary transforms using matrices. It also discusses separable two-dimensional transforms and provides properties of unitary transforms such as energy conservation. Specific transforms discussed in more detail include the discrete Fourier transform, discrete cosine transform, discrete sine transform, and Hadamard transform.
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.
Spatial filtering using image processingAnuj Arora
spatial filtering in image processing (explanation cocept of
mask),lapace filtering and filtering process of image for extract information and reduce noise
Image Restoration And Reconstruction
Mean Filters
Order-Statistic Filters
Spatial Filtering: Mean Filters
Adaptive Filters
Adaptive Mean Filters
Adaptive Median Filters
Image Enhancement: Introduction to Spatial Filters, Low Pass Filter and High Pass Filters. Here Discussed Image Smoothing and Image Sharping, Gaussian Filters
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.
Spatial filtering using image processingAnuj Arora
spatial filtering in image processing (explanation cocept of
mask),lapace filtering and filtering process of image for extract information and reduce noise
Image Restoration And Reconstruction
Mean Filters
Order-Statistic Filters
Spatial Filtering: Mean Filters
Adaptive Filters
Adaptive Mean Filters
Adaptive Median Filters
Image Enhancement: Introduction to Spatial Filters, Low Pass Filter and High Pass Filters. Here Discussed Image Smoothing and Image Sharping, Gaussian Filters
Comprehensive Performance Comparison of Cosine, Walsh, Haar, Kekre, Sine, Sla...CSCJournals
The desire of better and faster retrieval techniques has always fuelled to the research in content based image retrieval (CBIR). The extended comparison of innovative content based image retrieval (CBIR) techniques based on feature vectors as fractional coefficients of transformed images using various orthogonal transforms is presented in the paper. Here the fairly large numbers of popular transforms are considered along with newly introduced transform. The used transforms are Discrete Cosine, Walsh, Haar, Kekre, Discrete Sine, Slant and Discrete Hartley transforms. The benefit of energy compaction of transforms in higher coefficients is taken to reduce the feature vector size per image by taking fractional coefficients of transformed image. Smaller feature vector size results in less time for comparison of feature vectors resulting in faster retrieval of images. The feature vectors are extracted in fourteen different ways from the transformed image, with the first being all the coefficients of transformed image considered and then fourteen reduced coefficients sets are considered as feature vectors (as 50%, 25%, 12.5%, 6.25%, 3.125%, 1.5625% ,0.7813%, 0.39%, 0.195%, 0.097%, 0.048%, 0.024%, 0.012% and 0.06% of complete transformed image coefficients). To extract Gray and RGB feature sets the seven image transforms are applied on gray image equivalents and the color components of images. Then these fourteen reduced coefficients sets for gray as well as RGB feature vectors are used instead of using all coefficients of transformed images as feature vector for image retrieval, resulting into better performance and lower computations. The Wang image database of 1000 images spread across 11 categories is used to test the performance of proposed CBIR techniques. 55 queries (5 per category) are fired on the database o find net average precision and recall values for all feature sets per transform for each proposed CBIR technique. The results have shown performance improvement (higher precision and recall values) with fractional coefficients compared to complete transform of image at reduced computations resulting in faster retrieval. Finally Kekre transform surpasses all other discussed transforms in performance with highest precision and recall values for fractional coefficients (6.25% and 3.125% of all coefficients) and computation are lowered by 94.08% as compared to Cosine or Sine or Hartlay transforms.
Describes human eye optics.
Please send comments and suggestions for improvements to solo.hermelin@gmail.com.
For more presentations on different subjects please visit my website at http://www.solohermelin.com.
At the end of this lesson, you should be able to;
identify color formation and how color visualize.
describe primary and secondary colors.
describe display on CRT and LCD.
comprehend RGB, CMY, CMYK and HSI color models.
At the end of this lecture, you should be able to;
describe the importance of morphological features in an image.
describe the operation of erosion, dilation, open and close operations.
identify the practical advantage of the morphological operations.
apply morphological operations for problem solving.
EXPERT SYSTEMS AND SOLUTIONS
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IEEE 2010 , IEEE 2011 BASED PROJECTS FOR FINAL YEAR STUDENTS OF B.E
Email: expertsyssol@gmail.com,
Cell: +919952749533, +918608603634
www.researchprojects.info
OMR, CHENNAI
IEEE based Projects For
Final year students of B.E in
EEE, ECE, EIE,CSE
M.E (Power Systems)
M.E (Applied Electronics)
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Ph.D Electrical and Electronics.
Training
Students can assemble their hardware in our Research labs. Experts will be guiding the projects.
EXPERT GUIDANCE IN POWER SYSTEMS POWER ELECTRONICS
We provide guidance and codes for the for the following power systems areas.
1. Deregulated Systems,
2. Wind power Generation and Grid connection
3. Unit commitment
4. Economic Dispatch using AI methods
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7. Transformer Fault Identifications
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we provide guidance and codes for the for the following power Electronics areas.
1. Three phase inverter and converters
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Image and Audio Signal Filtration with Discrete Heap Transformsmathsjournal
Filtration and enhancement of signals and images by the discrete signal-induced heap transform (DsiHT) is described in this paper. The basic functions of the DsiHT are orthogonal waves that are originated from the signal generating the transform. These waves with their specific motion describe a process of elementary rotations or Givens transformations of the processed signal. Unlike the discrete Fourier transform which performs rotations of all data of the signalon each stage of calculation, the DsiHT sequentially rotates only two components of the data and accumulates a heap in one of the components with the maximum energy. Because of the nature of the heap transform, if the signal under process is mixed with a wave which is similar to the signal-generator then this additive component is eliminated or vanished after applying the heap transformation. This property can effectively be used for noise removal, noise detection, and image enhancement.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Search and Society: Reimagining Information Access for Radical FuturesBhaskar Mitra
The field of Information retrieval (IR) is currently undergoing a transformative shift, at least partly due to the emerging applications of generative AI to information access. In this talk, we will deliberate on the sociotechnical implications of generative AI for information access. We will argue that there is both a critical necessity and an exciting opportunity for the IR community to re-center our research agendas on societal needs while dismantling the artificial separation between the work on fairness, accountability, transparency, and ethics in IR and the rest of IR research. Instead of adopting a reactionary strategy of trying to mitigate potential social harms from emerging technologies, the community should aim to proactively set the research agenda for the kinds of systems we should build inspired by diverse explicitly stated sociotechnical imaginaries. The sociotechnical imaginaries that underpin the design and development of information access technologies needs to be explicitly articulated, and we need to develop theories of change in context of these diverse perspectives. Our guiding future imaginaries must be informed by other academic fields, such as democratic theory and critical theory, and should be co-developed with social science scholars, legal scholars, civil rights and social justice activists, and artists, among others.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
2. Why Do Transforms?
Fast computation
E.g., convolution vs. multiplication for filter with
wide support
Conceptual insights for various image processing
E.g., spatial frequency info. (smooth, moderate
change, fast change, etc.)
Obtain transformed data as measurement
E.g., blurred images, radiology images (medical
and astrophysics)
Often need inverse transform
May need to get assistance from other transforms
For efficient storage and transmission
Pick a few “representatives” (basis)
Just store/send the “contribution” from each basis
3. Introduction
Image transforms are a class of
unitary matrices used for
representing images.
An image can be expanded in terms
of a discrete set of basis arrays called
basis images.
The basis images can be generated
by unitary matrices.
4. One dimensional orthogonal and unitary
transforms
For a 1-D sequence represented
as a vector u of size N, a unitary transformation
is written as
{ ( ),0 1}u n n N
1
0
( ) ( , ) ( ) , 0 1
N
n
v k a k n u n k N
v = Au
5. 1
*
0
( ) ( ) ( , ) , 0 1
N
k
u n v k a k n n N
*T
u = A v
v(k) is the series representation of the sequence u(n).
The columns of A*T, that is, the vectors
are called the basis vectors of A.
*
{ ( , ), 0 1}T
a k n n N *
ka
One dimensional orthogonal and unitary
transforms
6. Two-dimensional orthogonal and
unitary transforms
A general orthogonal series expansion for an N x
N image u(m,n) is a pair of transformations of
the form
1 1
,
0 0
( , ) ( , ) ( , )
N N
k l
m n
y k l x m n a m n
1 1
*
,
0 0
( , ) ( , ) ( , )
N N
k l
k l
x m n y k l a m n
,where ( , ) ,k la m n called an image transform, is a set of complete
orthonormal discrete basis functions.
7. Separable unitary transforms
Complexity : O(N4)
Reduced to O(N3) when transform is separable i.e.
ak,l(m,n) = ak(m) bl(n) =a(k,m)b(l,n) where
{a(k,m), k=0,…,N-1},{b(l,n), l=0,…,N-1}
are 1-D complete orthonormal sets of basis vectors.
8. Separable unitary transforms
A={a(k,m)} and B={b(l,n)} are unitary
matrices i.e. AA*T = ATA* = I.
If B is same as A
1 1
0 0
( , ) ( , ) ( , ) ( , )
N N
m n
y k l a k m x m n a l n
T
Y AXA
1 1
* * *
0 0
( , ) ( , ) ( , ) ( , )
N N
T
k l
x m n a k m y k l a l n
*
X = A YA
9. Basis Images
Let denote the kth column of . Define the matrices
then
*
ka *T
A
* * *T
k,l k lA = a a
1 1
0 0
( , )
( , ) ,
N N
k l
y k l
y k l
*
k,l
*
k,l
X A
X A
, 0,..., 1k l N *
k,lA
The above equation expresses image X as a linear
combination of the N2 matrices , called
the basis images.
11. Example
Consider an orthogonal matrix A and image X
1 11
1 12
A
43
21
X
1 1 1 2 1 1 5 11
1 1 3 4 1 1 2 02
T
Y = AXA
To obtain basis images, we find the outer product of the
columns of A*T
* *
0,1 1,0
1 11
1 12
T
A A
*
1,1
1 11
1 12
A
*
0,0
1 1 11 1
1 1
1 1 12 2
A
The inverse transformation gives
1 1 5 1 1 1 1 21
1 1 2 0 1 1 3 42
*T *
X = A YA
12. Properties of Unitary Transforms
Energy Conservation
In unitary transformation, y = Ax and ||y||2 = ||x||2
1 1
2 2
0 0
( ) ( )
N N
k n
y k x n
2 2*T *T *T *T
y y y = x A Ax = x x x
Proof:
This means every unitary transformation is simply a rotation
of the vector x in the N-dimensional vector space.
Alternatively, a unitary transformation is rotation of the basis
coordinates and the components of y are the projections of x
on the new basis.
13. Properties of Unitary Transforms
Energy compaction
Unitary transforms pack a large fraction of the
average energy of the image into a relatively
few components of the transform coefficients.
i.e. many of the transform coefficients contain
very little energy.
Decorrelation
When the input vector elements are highly
correlated, the transform coefficients tend to be
uncorrelated.
Covariance matrix E[ ( y – E(y) ) ( y – E(y) )*T ].
small correlation implies small off-diagonal terms.
14. 1-D Discrete Fourier Transform
1
0
1
( ) ( ) , 0,..., -1
N
nk
N
n
y k x n W k N
N
2
expN
j
W
N
The discrete Fourier transform (DFT) of a sequence {u(n), n=0,…,N-1} is
defined as
where
The inverse transform is given by
1
0
1
( ) ( ) , 0,..., -1
N
nk
N
k
x n y k W n N
N
The NxN unitary DFT matrix F is given by
1
, 0 , 1nk
NF W k n N
N
15. DFT Properties
Circular shift u(n-l)c = x[(n-l)mod N]
The DFT and unitary DFT matrices are
symmetric i.e. F-1 = F*
DFT of length N can be implemented by a fast
algorithm in O(N log2N) operations.
DFT of a real sequence {x(n), n=0,…,N-1} is
conjugate symmetric about N/2.
i.e. y*(N-k) = y(k)
16. The Two dimensional DFT
1 1
0 0
1
( , ) ( , ) , 0 , -1
N N
km ln
N N
m n
y k l x m n W W k l N
N
1 1
0 0
1
( , ) ( , ) , 0 , -1
N N
km ln
N N
k l
x m n y k l W W m n N
N
The 2-D DFT of an N x N image {x(m,n)} is a separable
transform defined as
Y = FXF * *
X = F YF
The inverse transform is
In matrix notation &
17. Properties of the 2-D DFT
Symmetric,
unitary.
Periodic
Conjugate
Symmetry
Fast transform
Basis Images
T -1
* *
F F*
F F, F F =
( , ) ( , ), ,
( , ) ( , ), ,
y k N l N y k l k l
x m N n N x m n m n
*
( , ) ( , ), 0 , 1y k l y N k N l k l N
* ( )
,
1
, 0 , 1 , 0 , 1T km ln
k l k l NA W m n N k l N
N
O(N2log2N)
21. The Cosine Transform (DCT)
1
0
(2 1)
( ) ( ) ( )cos , 0 1
2
N
n
n k
y k k x n k N
N
1
, 0,0 1
( , )
2 (2 1)
cos , 1 1,0 1
2
k n N
N
C k n
n k
k N n N
N N
1
0
(2 1)
( ) ( ) ( )cos , 0 1
2
N
k
n k
x n k y k n N
N
The N x N cosine transform matrix C={c(k,n)}, also known
as discrete cosine transform (DCT), is defined as
1 2
(0) , ( ) = for 1 1
N
k k N
N
The 1-D DCT of a sequence {x(n), 0 ≤ n ≤ N-1} is defined as
The inverse transformation is given by
where
22. Properties of DCT
The DCT is real and orthogonal
i.e. C=C*C-1=CT
DCT is not symmetric
The DCT is a fast transform : O(N log2N)
Excellent energy compaction for highly
correlated data.
Useful in designing transform coders and
Wiener filters for images.
23. 2-D DCT
(2 1) (2 1)
( , , , ) ( ) ( )cos cos
2 2
m k n l
C m n k l k l
N N
1
0
( )
2
1 1
k
N
k
k N
N
The 2-D DCT Kernel is given by
where
Similarly for ( )l
25. The Sine Transform
( , )k nΨ
2 ( 1)( 1)
( , ) sin , 0 , 1
1 1
n k
k n k n N
N N
The N x N DST matrix is defined as
The sine transform pair of 1-D sequence is defined as
1
0
1
0
( ) ( ) ( , ), 0 1
( ) ( , ) ( ), 0 1
N
n
N
k
y k x n k n k N
x n k n y k n N
26. The properties of Sine
transform
The Sine transform is real, symmetric, and
orthogonal
The sine transform is a fast transform
It has very good energy compaction property
for images
* T -1
Ψ = Ψ = Ψ = Ψ
27. The Hadamard transform
The elements of the basis vectors of the
Hadamard transform take only the binary
values ±1.
Well suited for digital signal processing.
The transform matrices Hn are N x N matrices,
where N=2n, n=1,2,3.
Core matrix is given by
1 11
1 12
1H
28. The Hadamard transform
1 1
1 1
1 1
1
2
n n
n n
n n
H H
H H H
H H
The matrix Hn can be obtained by kroneker product recursion
3 2 1 2 1 1
3
&
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 11
1 1 1 1 1 1 1 18
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
H H H H H H
H
Example
29. The Hadamard transform properties
The number of sine changes in a row is called
sequency. The sequency for H3 is 0,7,3,4,
1,6,2,5.
The transform is real, symmetric and
orthogonal.
The transform is fast
Good energy compaction for highly correlated
data.
* T -1
H = H = H = H
30. The Haar transform
The Haar functions hk(x) are defined on a continuous
interval, x [0,1], and for k = 0,…,N-1, where N = 2n.
The integer k can be uniquely decomposed as k = 2p + q -1
where 0 ≤ p ≤ n-1; q=0,1 for p=0 and 1 ≤ q ≤ 2p for p≠0. For
example, when, N=4
k 0 1 2 3
p 0 0 1 1
q 0 1 1 2
31. The Haar transform
•The Haar functions are defined as
0 0,0
/ 2
/ 2
,
1
( ) ( ) , [0,1]
1
1 22 ,
2 2
1
1 2( ) 2 ,
2 2
0, [0,1]
p
p p
p
k p q p p
h x h x x
N
q
q
x
q
q
h x h x
N
otherwise for x
32. Haar transform example
The Haar transform is obtained by letting x take discrete
values at m/ N, m=0,…,N-1. For N = 4, the transform is
1 1 1 1
1 1 1 11
2 2 0 04
0 0 2 2
Hr
33. Properties of Haar transform
The Haar transform is real and
orthogonal
Hr = Hr* and Hr-1 = HrT
Haar transform is very fast: O(N)
The basis vectors are sequency
ordered.
It has poor energy compaction for
images.
34. KL transform
Hotelling transform
Originally introduced as a series
expansion for continuous random
process by Karhunen and Loeve.
The discrete equivalent of KL series
expansion – studied by Hotelling.
KL transform is also called the
Hotelling transform or the method of
principal components.
35. KL transform
Let x = {x1, x2,…, xn}T be the n x 1 random
vector.
For K vector samples from a random
population, the mean vector is given by
The covariance matrix of the population is
given by
1
1 K
k
kK
xm x
1
1 K
T T
k k
kK
x x xC x x m m
36. KL Transform
Cx is n x n real and symmetric matrix.
Therefore a set on n orthonormal eigenvectors
is possible.
Let ei and i, i=1, 2, …, n, be the eigenvectors
and corresponding eigenvalues of Cx, arranged
in descending order so that j ≥ i+1 for j = 1, 2,
…, n.
Let A be a matrix whose rows are formed from
the eigenvectors of Cx, ordered so that first row
of A is eigenvector corresponding to the largest
eigenvalue, and the last row is the eigenvector
corresponding to the smallest eigenvalue.
37. KL Transform
Suppose we use A as a transformation
matrix to map the vectors x’s into the
vectors y’s as follows:
y = A(x – mx)
This expression is called the Hotelling
transform.
The mean of the y vectors resulting from
this transformation is zero; that is my =
E{y} =0.
38. KL Transform
The covarianve matrix of the y’s is given in
terms of A and Cx by the expression
Cy = ACxAT
Cy is a diagonal matrix whose elements along
the main diagonal are the eigenvalues of Cx
1
2
0
0 n
yC
39. KL Transform
The off-diagonal elements of this
covariance matrix are 0, so that the
elements of the y vectors are
uncorrelated.
Cx and Cy have the same eigenvalues
and eigenvectors.
The inverse transformation is given by
x = ATy + mx
40. KL transform
Suppose, instead of using all the eigenvectors
of Cx we form a k x n transformation matrix
Ak from k eigenvectors corresponding to k
largest eigenvalues, the vector reconstructed
by using Ak is
The mean square error between x and is
T
k xx = A y + m
x
1 1 1
n k n
ms j j j
j j j K
e
41. KL Transform
As j’s decrease monotonically, the error can be
minimised by selecting the k eigenvectors
associated with the largest eigenvalues.
Thus Hotelling transform is optimal i.e. it
minimises the min square error between x and
Due to the idea of using the eigenvectors
corresponding to the largest eigenvalues, the
Hotelling transform is also known as the
principal components transform.
x
43. a) Original Image,
b) Reconstructed using all the three principal components,
c) Reconstructed image using two largest principal components,
d) Reconstructed image using only the largest principal component
KL Transform Example
a b
c d