digital image processing fundamentals
DESCRIPTION
CS804B, M1_1, Lecture NotesTRANSCRIPT
Resmi N.G.Reference: Digital Image Processing
Rafael C. GonzalezRichard E. Woods
What is a digital image?� An array of real or complex numbers represented by a
finite number of bits.
2CS 04 804B Image Processing - Module13/18/2012
What is digital image processing?
� Processing of a two dimensional image using acomputer.computer.
� Digital processing of any two dimensional data forstorage, transmission and machine perception.
3CS 04 804B Image Processing - Module13/18/2012
Three Types of Processing� Low-Level
� Both inputs and outputs are images.� Involves primitive operations such as image
preprocessing to reduce noise, contrast enhancement,and image sharpening.and image sharpening.
� Middle-Level� Inputs are images; Outputs are attributes extracted from
images.� Involves image segmentation (partitioning image into
regions), classification or recognition of individualobjects.
4CS 04 804B Image Processing - Module13/18/2012
� High-Level� Working with recognized objects as in image analysis.� eg; automated analysis of text
I. Acquiring image of area containing the text.II. PreprocessingII. PreprocessingIII. Segmenting individual characters.IV. Describing characters in a form suitable for computer
processing.V. Recognizing the individual characters.
5CS 04 804B Image Processing - Module13/18/2012
Origin of Image Processing� One of the first applications of digital imaging was
in the newspaper industry.� Early 1920’s- Introduction of The Bartlane Cable
Picture Transmission system.Picture Transmission system.� Pictures were sent by submarine cable between
London and New York.� 5 distinct levels of grey.
6CS 04 804B Image Processing - Module13/18/2012
� 1929: Levels of grey increased to 15.
3/18/2012 CS 04 804B Image Processing - Module1 7
� 1964: Pictures of moon transmitted by Ranger7 wereprocessed using computers to correct various types ofimage distortion.
3/18/2012 CS 04 804B Image Processing - Module1 8
Applications of DIP� Medical applications-to study X-ray images.
3/18/2012 CS 04 804B Image Processing - Module1 9
� Geographic Information Systems-to study pollution patterns from aerial and satellite images.
3/18/2012 CS 04 804B Image Processing - Module1 10
� Astronomy
3/18/2012 CS 04 804B Image Processing - Module1 11
Applications classified based on their sources of energy
� Electro-magnetic spectrum (gamma rays with highest energy to radio waves with lowest energy)
12CS 04 804B Image Processing - Module13/18/2012
� Gamma-ray Imaging� Radioactive isotope emits positrons while it decays.� Gamma rays are given off when a positron hits an
electron.� These are detected and image is created.
3/18/2012 CS 04 804B Image Processing - Module1 13
� X-ray Imaging� X-rays are generated using an X-ray tube(vacuum tube
with a cathode and an anode).
3/18/2012 CS 04 804B Image Processing - Module1 14
� Imaging in Ultra Violet Band
3/18/2012 CS 04 804B Image Processing - Module1 15
� Imaging in Visible and Infrared Bands
3/18/2012 CS 04 804B Image Processing - Module1 16
� Remote sensing applications
3/18/2012 CS 04 804B Image Processing - Module1 17
3/18/2012 CS 04 804B Image Processing - Module1 18
Other areas of application� Microwave band – Radar (explores inaccessible region’s of
earth’s surface)� Radio band – in medicine(Magnetic Resonance Imaging)
and astronomy� Acoustic Imaging (mineral and oil exploration over land
and water)and water)� Synthetic Imaging� Archaeology� Physics� Biology� Defense� Industry� Machine perception
19CS 04 804B Image Processing - Module13/18/2012
Fundamental Steps in Digital Image Processing
3/18/2012 CS 04 804B Image Processing - Module1 20
Image acquisition� Involves preprocessing such as scaling
3/18/2012 CS 04 804B Image Processing - Module1 21
Image Enhancement� Brings out details that are obscured.� Highlights certain features of interest in an image.
3/18/2012 CS 04 804B Image Processing - Module1 22
Image Restoration� Improves appearance of an image� Based on mathematical or probabilistic models of
image degradation.
3/18/2012 CS 04 804B Image Processing - Module1 23
Colour Image Processing
� Colour is used to extract features of interest in an image.
3/18/2012 CS 04 804B Image Processing - Module1 24
Wavelets and MultiresolutionProcessing
� Wavelets are used: � for representing images in various degrees of resolution� for data compression� for data compression� pyramidal representation
3/18/2012 CS 04 804B Image Processing - Module1 25
Compression� Reduces the storage required to save an image or
bandwidth required to transmit it.
3/18/2012 CS 04 804B Image Processing - Module1 26
Morphological Processing� Tools for extracting image components that are useful
in the representation and description of shape ofimage. eg; boundary extraction.
3/18/2012 CS 04 804B Image Processing - Module1 27
Segmentation
� Partitions image into its constituent parts or objects.
3/18/2012 CS 04 804B Image Processing - Module1 28
Representation and description
� Output of segmentation stage - Raw pixel data(either theboundary of a region or the region as a whole).
� Choosing a representation - one step in transforming raw� Choosing a representation - one step in transforming rawdata into form suitable for computer processing.
� Description(feature selection) deals with highlightingfeatures of interest.
3/18/2012 CS 04 804B Image Processing - Module1 29
3/18/2012 CS 04 804B Image Processing - Module1 30
Object Recognition� Assigning labels to objects based on its descriptors.
3/18/2012 CS 04 804B Image Processing - Module1 31
Image Representation� Each digital image consists of a finite number of
elements called picture elements or pixels.� Each pixel has a particular location and value.� Image representation concerns with charaterization of� Image representation concerns with charaterization of
the quantity that each pixel represents.� Luminances of objects� Absorption characteristics of body tissue� Radar cross-section of target� Temperature profile of a region
3/18/2012 CS 04 804B Image Processing - Module1 32
Definition for a Digital Image� Any two dimensional function that bears information
is considered an image.� An image is defined as a two-dimensional function
f(x,y), where x and y are spatial coordinates.f(x,y), where x and y are spatial coordinates.� Amplitude of ‘f ’ at any pair of coordinates (x,y) is
called intensity of image at that point.� When x, y and amplitude values of ‘f ’ are all finite,
discrete quantities, the image is called a digital image.
3/18/2012 CS 04 804B Image Processing - Module1 33
Knowledge Base
34CS 04 804B Image Processing - Module13/18/2012
� Knowledge about the problem domain.� Details regions of an image where information of
interest is known to be located.� Advantage: limits the search.� Advantage: limits the search.� Controls the interaction between modules.
35CS 04 804B Image Processing - Module13/18/2012
Components of an Image Processing System
36CS 04 804B Image Processing - Module13/18/2012
Image Acquisition� Two elements:
� Image sensors� Digitizer
Image sensor – Physical device that is sensitive to theenergy radiated by the object we wish to image.
Digitizer – Converts sensing device output to digital form.
37CS 04 804B Image Processing - Module13/18/2012
Specialized Image Processing Hardware
� High speed front end subsystem.� Two elements:
� Digitizer� Arithmetic and Logic Unit (ALU)� Arithmetic and Logic Unit (ALU)
ALU performs arithmetic and logical operations inparallel on entire images.
eg; averaging images for noise reduction.
38CS 04 804B Image Processing - Module13/18/2012
Image Processing Software
� Consists of specialized modules that perform specific tasks.
� User can write code utilizing these specialized � User can write code utilizing these specialized modules.
39CS 04 804B Image Processing - Module13/18/2012
Mass Storage� A must for image storage� Image of size 1024 x 1024 pixels in which intensity of
each pixel is an 8-bit quantity requires 1 MB of storagespace.
� 3 categories:� Short-trem (during processing)� Online storage (for fast access)� Archival (infrequent access, massive storage)
40CS 04 804B Image Processing - Module13/18/2012
Short-term: � Computer memory� Frame buffers
Online: � Magnetic disks� Magnetic disks� Optical media
Archival: � Magnetic tapes� Optical disks
3/18/2012 CS 04 804B Image Processing - Module1 41
Image Displays
Hardcopy devices
� Color TV monitors
� Laser printers, cameras, heat-sensitive devices.
3/18/2012 CS 04 804B Image Processing - Module1 42
Hardcopy devices
Thank YouThank You
3/18/2012 CS 04 804B Image Processing - Module1 43