Digital Image Processing Tania Stathaki Location Extension Email

Digital Image Processing Tania Stathaki Location: Extension: Email: Room 812 46229 t. stathaki@ic. ac. uk

LOGISTICS OF THE COURSE n Duration – 20 lectures n Assessment – 100% exam – There isn't any coursework or homework

IMAGE PROCESSING §Textbook – R. C. Gonzalez, R. E. Woods, Digital Image Processing, Addison Wesley, 1993, ISBN 0 -201 -50803 -6

DIGITAL IMAGE

DIGITAL IMAGE

FROM ANALOG TO DIGITAL object Imaging systems Sample and quantize Digital storage (disk) Digital computer On-line buffer observe digitize store process Refresh /store Display output Record

Sampling 256 x 256 64 x 64

Quantisation – 8 bits 0 255 0 0 0 0 255 0 0 0 255 255 0

Quantisation cont. 256 x 256 levels 256 x 256 32 levels

Quantisation cont. 256 x 256 levels 256 x 256 2 levels

Coloured Image

Intensity (Gray-Level) Image

Binary Image

Image Processing § manipulation of multidimensional signals image (photo) video CT, MRI

Image Processing § Why? – Coding/compression – Enhancement, restoration, reconstruction – Analysis, detection, recognition, understanding – Visualization

Part I: Image Transforms Original Image Fourier Transform Amplitude Phase

Part II: Image Enhancement Original Image High Pass Filtering

Part III: Image Restoration Distorted Image Restored Image

Distortion due to Camera Misfocus Original image Distorted image

Distortion due to Camera Misfocus Camera lens

Distortion due to motion Camera lens

Distortion due to Random Noise Original image Distorted image

Part IV: Image Compression § Signal-Processing Based: Encoder H Decoder Compressed Representation

Images are not directly amenable to computer analysis n n Computers work with numerical (rather than pictorial) data. An image must be converted to numerical form before processing by computer can commence. n n n Picture elements or pixels Rectangular sampling grid Brightness of the image

Images are not directly amenable to computer analysis

APPLICATIONS Medical images n Satellite images n Astronomy n Radar images n

Satellite image Volcano Kamchatka Peninsula, Russia

Satellite image Volcano in Alaska

Medical Images: MRI of normal brain

Medical Images: X-ray knee

Medical Images: Ultrasound Five-month Foetus (lungs, liver and bowel)

Astronomical images