Introduction to Digital Image Processing

1 Introduction to Digital Image ProcessingRanga RodrigoNovember 13, 20111/1121 Introduction2 Digital Images3 Matlab or Octave Tutorial4 Programming in MatlabFlow ControlScripts and FunctionsOther Data Structures2/112 Outline1 Introduction2 Digital Images3 Matlab or Octave Tutorial4 Programming in MatlabFlow ControlScripts and FunctionsOther Data Structures3/112 What Is Digital Image Processing ? Digital Image Processing helps us enhance images to make them visuallypleasing, or accentuate regions or features of an Image to betterrepresent the example, we may wish to enhance the brightness and contrast tomake a better print of a photograph, similar to popular a magnetic resonance Image (MRI)

2 Of the brain, we may want toaccentuate a certain region of Image intensities to see certain parts ofthe analysis and computer vision, which go beyond Image Processing ,helps us to make decisions based on the contents of the course, vision for automation, will give you the basic knowledgerequired to enter into this exciting field, and equip you with basic tools todo Image Processing and computer vision and apply the knowledge Is Computer Vision?The goal is the emulation of the visual capability of human beings other words, computer vision is making the machine see as we do!It is :1 Image acquisition2 Image manipulation3 Image understanding4 Decision making6/112 What Is Computer Vision?

3 The goal is the emulation of the visual capability of human beings other words, computer vision is making the machine see as we do!It is :1 Image acquisition2 Image manipulation3 Image understanding4 Decision making6/112 What Is Computer Vision?The goal is the emulation of the visual capability of human beings other words, computer vision is making the machine see as we do!It is :1 Image acquisition2 Image manipulation3 Image understanding4 Decision making6/112 What Is Computer Vision?The goal is the emulation of the visual capability of human beings other words, computer vision is making the machine see as we do!

4 It is :1 Image acquisition2 Image manipulation3 Image understanding4 Decision making6/112 Main Driving TechnologiesSignal view recognition and machine and :Lane departure warning tracking systems for drowsiness assistance automobile license plates, and traffic :In camera face detection [2], red eye removal, and other panorama stitching [1].1(From )8/112 ApplicationsMovie and video (a very big industry):Augmented objects in video or film and solving for 3-D motion to allow forprecise augmentation with 3-D computer cameras to precisely track tennis and cricket expression for 3-D visualization for sports broadcasting and consistent regions in video and insert virtual for character capture, camera tracking, panorama stitching, and building 3 Dmodels for TrackingShow 2d3 :Tracking human gestures for playing games or interacting with the hand and body motions of players (to control the SonyPlaystation).

5 Image -based rendering, vision for purpose:Inspection and localization tasks, people counting, biomedical, and recognition and navigation for mobile robotics, grocery retail, andrecognition from cell phone 3D vision systems for use on the space shuttles and retrieval based on automation (a very big industry):Vision-guided robotics in the automotive inspection systems for component and biomedical (maturing):Vision to detect and track the pose of markers for surgical applications,needle insertion, and seed analysis of medical imaging, including diagnosis such and biometrics (thriving):Intelligent video face, fingerprint, and iris Invasive Surgery13/112 Areas of Images3 Matlab or Octave Tutorial4 Programming in MatlabFlow ControlScripts and FunctionsOther Data Structures15/112 What Is a Digital Image ?

6 DefinitionAn Image may be defined as a two-dimensional function,f(x,y), wherexandyare spatial coordinates, and the amplitude offat any pair of coordinates(x,y)is called the intensity of gray level offof the Image at that ,y, and the amplitude values offare all finite, discrete quantities, wecall the Image a Digital Image RepresentationA Digital Image can thus be treated as a 2-D array of integers. Let sdenote a Digital Image asf(i,j). The variables take following values:i [0,h 1], wherehis the height of the [10,w 1], wherewis the width of the (i,j) [0,L 1], whereL 1=255for an 8-bit can formally write this asf: [0,h 1] [0,w 1]7 [0,L 1].

7 (1)In Matlab or Octave indicesitakes the values form1toh, and indexjtakes the values 1w 1i0j0 Figure 1: Digital Image coordinates. Here,i [0,h 1]andj [0,w 1]. In Matlab andOctave,i [1,h]andj [1,w].f(i,j)is the value of the pixel at coordinate(i,j). Forconvenience, we sayf(i,j)is the values of pixel(i,j).18/112 PixelsA Digital images consists of a finite number of elements are referred to as picture elements, or grayscale Digital Image can be seen as a two-dimensional array (i0,j0)is the grayscale values of the pixel at coordinate(i0,j0).19/112 Color ImagesA color Image can be represented using three functionsfR(x,y),fG(x,y),andfB(x,y), representing the red, green and blue values can interpret a Digital color Image as consisting of threetwo-dimensional bands: infrared, : PET (positron emission tomography).

8 And Formationscene planeimage planecamera22/112 Camera GeometryCZYXPxfCis the camera center andCZis the optical the Image of the the focal length andxhas Image coordinates(fXZ,fYZ)if theimage center isPand Image coordinate axes Resolution and Dots Per InchResolution is the number of pixels in the Image , ,800 same Image with a particular resolution can be displayed with acertain number of dots per inch (DPI).If we display an800 600image at 100 DPI, the Image will be 8 incheswide and 6 inches at least 300 DPI is needed for good print 2 shows the effects of changing Image resolution.

9 (a)320 240, 300 DPI(b)160 120, 300 DPI(c)80 60, 300 DPI(d)40 30, 300 DPIF igure 2: Effect of resolution with the same 3 shows the effects of changing dots-per-inch value.(a)160 120, 150 DPI(b)160 120, 300 DPIF igure 3: Effect of DPI with the same ImagesIf we have a400 300image and want a600 450image, we need order to zoom, we need Processing , Analysis, and Computer VisionThere is no clear cut boundary between categorization is low-, mid-, and high-level ProcessingPreprocessing to remove ProcessingImage Images3 Matlab or Octave Tutorial4 Programming in MatlabFlow ControlScripts and FunctionsOther Data Structures32/112 What Is Matlab?

10 The Matlab high-performance language for technical computingintegrates computation, visualization, and programming in an easy-to-useenvironment where problems and solutions are expressed in familiarmathematical notation. Therefore, Matlab is a powerful and friendly environment for in MatlabMatlab helps us to do matrix manipulations. This is the basic functionalityof Matlab. There are a large number of toolboxes built on top of this Processing Toolbox is one of these toolboxes. However, we try touse the basic functionality and just minimally use the Image ProcessingToolbox. This is because our aim is to be able to write our own imageprocessing programs in is a free tool that can do a lot of tasks Matlab is capable of toolboxes are not as comprehensive as Matlab, or it is not asuser-friendly as MatricesIn order to enter a matrix in Matlab or Octave command window, type thefollowing:2A = [ 1 2 3 ; 4 5 6 ; 7 8 9 ]Matlab responds with the following:A =123456789If we add a semicolon, Matlab will not display the value of the = [ 1 2 3 ; 4 5 6 ; 7 8 9 ] ;2In the following tutorial, I follow Matlab s Getting Started Guide.