Digital Image Digital Image ProcessingProcessing

Digital Image Digital Image ProcessingProcessing

SANDHIYA

LOGISTICS OF THE LOGISTICS OF THE COURSECOURSE

DurationDuration– 20-22 lectures20-22 lectures

AssessmentAssessment– 100% exam100% exam– There isn't any coursework or There isn't any coursework or

homeworkhomework

IMAGE PROCESSINGIMAGE PROCESSING

TextbookTextbook –– R. C. Gonzalez, R. E. WoodsR. C. Gonzalez, R. E. Woods, , Digital Digital Image Processing, Image Processing, Addison Addison Wesley, Wesley, 1993, ISBN 0-201-50803-6 1993, ISBN 0-201-50803-6

DIGITAL IMAGEDIGITAL IMAGEDIGITAL IMAGEDIGITAL IMAGE

DIGITAL IMAGEDIGITAL IMAGEDIGITAL IMAGEDIGITAL IMAGE

FROM ANALOG TO FROM ANALOG TO DIGITALDIGITAL

Record

outputDisplay

object observe

Imaging systems

digitize

Sample and quantize

store

Digital storage (disk)

process

Digital computer

Refresh/store

On-line buffer

SamplingSamplingSamplingSampling

256x256 64x64

QuantisationQuantisation – 8 – 8 bitsbits

0 0 0

00

0 0

00

0

0 0

00

0 0

0

255 255

255

255

255

255 255255

Quantisation cont.Quantisation cont.Quantisation cont.Quantisation cont.

256x256 256 levels 256x256 32 levels

Quantisation cont.Quantisation cont.Quantisation cont.Quantisation cont.

256x256 256 levels 256x256 2 levels

Coloured ImageColoured ImageColoured ImageColoured Image

Intensity (Gray-Level) Intensity (Gray-Level) ImageImage

Intensity (Gray-Level) Intensity (Gray-Level) ImageImage

Binary ImageBinary ImageBinary ImageBinary Image

Image ProcessingImage Processing

manipulation of multidimensional signalsmanipulation of multidimensional signals

image (photo)image (photo)

videovideo

CT, MRI CT, MRI

),( yxf

),,( tyxf

),,,( tzyxf

Image ProcessingImage Processing

Why?Why?

– – Coding/compressionCoding/compression

– – Enhancement, restoration, reconstructionEnhancement, restoration, reconstruction

– – Analysis, detection, recognition, Analysis, detection, recognition, understandingunderstanding

– – VisualizationVisualization

Original Image Fourier Transform Amplitude Phase

Part I: Image TransformsPart I: Image Transforms

Original Image High Pass Filtering

Part II: Image Part II: Image EnhancementEnhancement

Distorted Image Restored Image

Part III: Image RestorationPart III: Image Restoration

Distortion due to Camera Distortion due to Camera MisfocusMisfocus

Original image Distorted image

Distortion due to Camera Distortion due to Camera MisfocusMisfocus

Camera lens

Distortion due to motionDistortion due to motion

Camera lens

Distortion due to Random Distortion due to Random NoiseNoise

Distorted imageOriginal image

Part IV: Image Part IV: Image CompressionCompression

Signal-Processing BasedSignal-Processing Based::

EncoderEncoder),( yxf

H),( yxg Compressed

Representation

Decoder 1H

),(ˆ yxf),( yxg

Images are not directly amenable to Images are not directly amenable to computer analysiscomputer analysis

Computers work with Computers work with numericalnumerical (rather (rather than than pictorialpictorial) data.) data.

An image must be An image must be converted to converted to numerical form numerical form before processing by before processing by computer can computer can commence.commence.

Picture elements or pixelsPicture elements or pixels Rectangular sampling gridRectangular sampling grid Brightness of the imageBrightness of the image

Images are not directly amenable to Images are not directly amenable to computer analysiscomputer analysis

Medical imagesMedical images Satellite imagesSatellite images AstronomyAstronomy Radar imagesRadar images

APPLICATIONSAPPLICATIONS

Satellite imageSatellite imageVolcano Volcano Kamchatka Peninsula, RussiaKamchatka Peninsula, Russia

Satellite imageSatellite imageVolcano in AlaskaVolcano in Alaska

Medical Images:Medical Images:MRI of normal brainMRI of normal brain

Medical Images:Medical Images:X-ray kneeX-ray knee

Medical Images: UltrasoundMedical Images: UltrasoundFive-month Foetus (lungs, liver and Five-month Foetus (lungs, liver and

bowel)bowel)

Astronomical images Astronomical images