Digital Image Processing Fundamentals

Resmi N.G. Reference: Digital Image Processing Rafael C. Gonzalez Richard E. Woods

What is a digital image? An array of real or complex numbers represented by a

finite number of bits.

3/18/2012

CS 04 804B Image Processing - Module1

2

What is digital image processing? Processing of a two dimensional image using a

computer. Digital processing of any two dimensional data for storage, transmission and machine perception.

3/18/2012


3

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. Middle-Level Inputs are images; Outputs are attributes extracted from images. Involves image segmentation (partitioning image into regions), classification or recognition of individual objects.

3/18/2012


4

High-Level Working with recognized objects as in image analysis. eg; automated analysis of text I. II. III. IV.

V.

3/18/2012

Acquiring image of area containing the text. Preprocessing Segmenting individual characters. Describing characters in a form suitable for computer processing. Recognizing the individual characters.


5

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. Pictures were sent by submarine cable between London and New York. 5 distinct levels of grey.

3/18/2012


6

1929: Levels of grey increased to 15.

3/18/2012


7

1964: Pictures of moon transmitted by Ranger7 were

processed using computers to correct various types of image distortion.

3/18/2012


8

Applications of DIP Medical applications-to study X-ray images.

3/18/2012


9

Geographic Information Systems-to study pollution

patterns from aerial and satellite images.

3/18/2012


10

Astronomy

3/18/2012


11

Applications classified based on their sources of energy Electro-magnetic spectrum (gamma rays with highest

energy to radio waves with lowest energy)

3/18/2012


12

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


13

X-ray Imaging X-rays are generated using an X-ray tube(vacuum tube with a cathode and an anode).

3/18/2012


14

Imaging in Ultra Violet Band

3/18/2012


15

Imaging in Visible and Infrared Bands

3/18/2012


16

Remote sensing applications

3/18/2012


17

3/18/2012


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) Synthetic Imaging Archaeology Physics Biology Defense Industry Machine perception

3/18/2012


19

Fundamental Steps in Digital Image Processing

3/18/2012


20

Image acquisition Involves preprocessing such as scaling

3/18/2012


21

Image Enhancement Brings out details that are obscured. Highlights certain features of interest in an image.

3/18/2012


22

Image Restoration Improves appearance of an image Based on mathematical or probabilistic models of

image degradation.

3/18/2012


23

Colour Image Processing Colour is used to extract features of interest in an

image.

3/18/2012


24

Wavelets and Multiresolution Processing Wavelets are used: for representing images in various degrees of resolution for data compression pyramidal representation

3/18/2012


25

Compression Reduces the storage required to save an image or

bandwidth required to transmit it.

3/18/2012


26

Morphological Processing Tools for extracting image components that are useful

in the representation and description of shape of image. eg; boundary extraction.

3/18/2012


27

Segmentation Partitions image into its constituent parts or objects.

3/18/2012


28

Representation and description Output of segmentation stage - Raw pixel data(either the

boundary of a region or the region as a whole).

Choosing a representation - one step in transforming raw

data into form suitable for computer processing.

Description(feature selection) deals with highlighting

features of interest.

3/18/2012


29

3/18/2012


30

Object Recognition Assigning labels to objects based on its descriptors.

3/18/2012


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 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


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. 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


33

Knowledge Base

3/18/2012


34

Knowledge about the problem domain. Details regions of an image where information of

interest is known to be located. Advantage: limits the search. Controls the interaction between modules.

3/18/2012


35

Components of an Image Processing System

3/18/2012


36

Image Acquisition Two elements: Image sensors Digitizer Image sensor – Physical device that is sensitive to the energy radiated by the object we wish to image. Digitizer – Converts sensing device output to digital form.

3/18/2012


37

Specialized Image Processing Hardware High speed front end subsystem. Two elements: Digitizer Arithmetic and Logic Unit (ALU) ALU performs arithmetic and logical operations in parallel on entire images. eg; averaging images for noise reduction.

3/18/2012


38

Image Processing Software Consists of specialized modules that perform specific

tasks. User can write code utilizing these specialized modules.

3/18/2012


39

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 storage space. 3 categories: Short-trem (during processing) Online storage (for fast access) Archival (infrequent access, massive storage) 3/18/2012


40

Short-term: Computer memory Frame buffers

Online: Magnetic disks Optical media

Archival: Magnetic tapes Optical disks

3/18/2012


41

Image Displays Color TV monitors

Hardcopy devices Laser printers, cameras, heat-sensitive devices.

3/18/2012


42

Thank You

3/18/2012


43

Digital Image Processing Fundamentals

Recommend Documents