Lec1

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Lec1

  1. 1. Chapter 1 Introduction* What is Computer Vision?* Applications* Relations with other fields* Resources
  2. 2. 1.1 What is Computer Vision?Computer vision is a field that includes methodsfor acquiring, processing, analyzing, andunderstanding one or more images from the realworld in order to produce and communicatenumerical or symbolic information to users orother systems.How to acquire images?Why we need to process and analyze images?Why we want the computer to understand the images?
  3. 3. 1.2 ApplicationsIndustrial inspection and quality control – detectcracks in bottleReverse engineering – generate 3D object modelfrom imagesFace/gesture recognition – securityTrack and count humans – surveillance, human-computer interactionTrack and count vehicles – road monitoringImage database query – automatic image retrievalMedical image analysis – assist diagnosis, surgery
  4. 4. 1.3 Related disciplinescomputer vision = machine vision = image understanding Computer Image Vision Processing noise filtering, edge detection, etc.
  5. 5. Many computer vision methods use and extend signal processing techniques Pattern recognition can be considered as part of computer vision Computer vision is, in some ways, the inverse of computer graphics. CV CGoriginal image 3D model synthetic image
  6. 6. 1.4 To know more about Computer Vision1.4.1 conference• International Conference on Computer Vision (ICCV)• International Conference on Computer Vision and Pattern Recognition (CVPR)• European Conference on Computer Vision (ECCV)
  7. 7. 1.4.2 journal• International Journal of Computer Vision• IEEE Transactions on Pattern Analysis and Machine Intelligence• Computer Vision and Image Understanding• Machine Vision and Applications1.4.3 internet• CVonline (http://homepages.inf.ed.ac.uk/rbf/CVonline)• Numerical Recipes (http://apps.nrbook.com/empanel/index.html#)
  8. 8. 1.5 Overview of MATLAB1.5.1 The MATLAB environment• when you start MATLAB, the command window will open with the prompt >>• user can enter commands or data in the command window• for each command typed in, you get the result immediately• if you do not assign the result to a variable, MATLAB will assign it to ans
  9. 9. 1.5.2 Assignment• assign value(s) to variable name(s)scalar variable>> a = 4 >> a = 4, A = 6a= a= 4 4 Separate>> A= multiple 6 commands by>> a = 4; >> comma>> Case sensitiveNo echo print
  10. 10. array• a collection of values represented by one variable name• one-dimensional array – vector• two-dimensional array – matrix>> a = [1 2 3 4 5]a= 1 2 3 4 5 Row vector>>
  11. 11. >> a = [1;2;3;4;5] >> a = [1 2 3 4 5]a= a= 1 1 Use single quote 2 2 as transpose 3 3 operator 4 4 5 5>> >> Column vector
  12. 12. >> A = [1 2 3; 4 5 6; 7 8 9] >> A = [1 2 3A= 456 1 2 3 7 8 9] 4 5 6 A= 7 8 9 1 2 3>> 4 5 6 7 8 9 >> Press Enter key to separate the rows
  13. 13. To access individual element:>> a(3)ans = 3>>>> A(2,3)ans = Column index 6 Row index>>
  14. 14. colon operator>> A(2,:)ans = 4 5 6>>Access the entire row increment (If it is omitted,start end the default value is 1)>> t = 1:0.5:3t= 1.0000 1.5000 2.0000 2.5000 3.0000>>
  15. 15. negative increment>> t = 10:-1:5t= 10 9 8 7 6 5>>To extract part of the array:>> t(2:4)ans = 9 8 7>>
  16. 16. 1.5.3 Mathematical operations^ exponentiation Highest priority- negation*/ multiplication, division left division+- addition, subtraction Lowest priority• priority order can be overridden with parentheses
  17. 17. >> y = -4 ^ 2y= -16>>>> y = (-4) ^ 2y= 16>>
  18. 18. 1.5.4 M-file• M-file provides an alternative way of using MATLAB to perform numerical analysis• starts with the word function• can have input argument(s) and output(s)• multiple inputs - separate by comma• multiple outputs – separate by comma, enclose in square brackets• it contains a series of statements• the file is stored with an extension .m
  19. 19. function outvar = funcname(arglist)% commentsstatementsoutvar = value;outvar: name of output variablefuncname: name of functionarglist: argument listcomments: information for user
  20. 20. 1.5.5 Structured programming• simple M-file performs command sequentially, from the first statement to the last• the program is highly restrictive• real programs usually have non-sequential execution paths, which can be achieved via decisions and loops
  21. 21. decision• the branching of execution flow based on a decisionif condition if condition 1 statements group 1 statementsend elseif condition 2 group 2 statementsif condition . group 1 statements .else else group 2 statements else statementsend end
  22. 22. • one simple form of condition is a relational expression that compares two valuesvalue 1 relation value 2operator relation== equal~= not equal< less than> greater than<= less than or equal to>= greater than or equal to
  23. 23. • logical operators can be used to test more than one logical condition• there is priority order, use parentheses to override itoperator meaning~ not Highest priority&& and|| or Lowest priority
  24. 24. loop• the repetition of a group of statementsfor index = start:step:finish statementsend
  25. 25. for i = 1:2:5 disp(i) Positive stependfor i = 5:-2:1 disp(i) Negative stependfor i = 1:5 disp(i) Default step = 1end
  26. 26. while condition statementsendi = 5;while i > 0 i = i – 1; disp(i)end
  27. 27. Summary♦ scope of Computer Vision♦ application areas♦ relations with other fields♦ resources and development platform of computer vision

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