Introduction in Digital Image Processing, Lecture notes of Digital Image Processing

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CS316-DIGITAL IMAGE PROCESSING

Introduction

COURSE ORGANISATION

• LECTURES

• TUTORIALS

• PRACTICALS

• ASSIGNMENTS

• QUIZES

• 2 TESTS

• Failure to attend any one of the components above may lead to severe punishment on you.

The physics of vision

Image formation in the eye:

• In photographic cameras, the lens has a fixed focal length and focusing at various distances is achieved by varying the distance between the lens and the imaging plane, where the film is located.
• In human eye, the distance between the lens and the imaging region (the retina) is fixed, and the focal length needed to achieve proper focus is obtained by varying the shape of the lens.

The physics of vision…

What is a Digital Image? (cont…)

Pixel values typically represent gray levels, colours, heights, opacities etc Remember digitization implies that a digital image is an approximation of a real scene 1 pixel

What is a Digital Image? (cont…)

Common image formats include:

• 1 sample per point (B&W or Grayscale)
• 3 samples per point (Red, Green, and Blue)
• 4 samples per point (Red, Green, Blue, and “Alpha”, a.k.a. Opacity)

What is DIP? (cont…)

The continuum from image processing to computer vision can be broken up into low-, mid- and high-level processes Low Level Process Input: Image Output: Image Examples: Noise removal, image sharpening Mid Level Process Input: Image Output: Attributes Examples: Object recognition, segmentation High Level Process Input: Attributes Output: Understanding Examples: Scene understanding, autonomous navigation In this course we will stop here

History of Digital Image Processing

Early 1920s: One of the first applications of digital imaging was in the news- paper industry

• The Bartlane cable picture transmission service
• Images were transferred by submarine cable between London and New York
• Pictures were coded for cable transfer and reconstructed at the receiving end on a telegraph printer Early digital image Images taken from Gonzalez & Woods, Digital Image Processing (2002)

History of DIP (cont…)

1960s: Improvements in computing technology and the onset of the space race led to a surge of work in digital image processing

• 1964: Computers used to improve the quality of images of the moon taken by the Ranger 7 probe
• Such techniques were used in other space missions including the Apollo landings A picture of the moon taken by the Ranger 7 probe minutes before landing Images taken from Gonzalez & Woods, Digital Image Processing (2002)

History of DIP (cont…)

1970s: Digital image processing begins to be used in medical applications

• 1979: Sir Godfrey N. Hounsfield & Prof. Allan M. Cormack share the Nobel Prize in medicine for the invention of tomography, the technology behind Computerised Axial Tomography (CAT) scans Typical head slice CAT image Images taken from Gonzalez & Woods, Digital Image Processing (2002)

Examples: Image Enhancement

One of the most common uses of DIP techniques: improve quality, remove noise etc Images taken from Gonzalez & Woods, Digital Image Processing (2002)

Examples: The Hubble Telescope

Launched in 1990 the Hubble telescope can take images of very distant objects However, an incorrect mirror made many of Hubble’s images useless Image processing techniques were used to fix this

Examples: Medicine

Take slice from MRI scan of canine heart, and find boundaries between types of tissue

• Image with gray levels representing tissue density
• Use a suitable filter to highlight edges Original MRI Image of a Dog Heart (^) Edge Detection Image Images taken from Gonzalez & Woods, Digital Image Processing (2002)

Examples: GIS

Geographic Information Systems

• Digital image processing techniques are used extensively to manipulate satellite imagery
• Terrain classification
• Meteorology Images taken from Gonzalez & Woods, Digital Image Processing (2002)