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

LOGISTICS OF THE COURSE Duration 20 lectures 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 store object observe digitize process Digital storage (disk) object observe Imaging systems digitize Sample and quantize process Digital computer Refresh/store On-line buffer Record output Display

Sampling 256x256 64x64

Quantisation – 8 bits 255

Quantisation cont. 256x256 256 levels 256x256 32 levels

Quantisation cont. 256x256 256 levels 256x256 2 levels

Coloured Image

Intensity (Gray-Level) Image

Binary Image

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

Image Processing Why? – Enhancement, restoration, reconstruction – 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 Compressed Representation H Decoder

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

Images are not directly amenable to computer analysis

APPLICATIONS Medical images Satellite images Astronomy Radar images

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