Chapter 1. IntroductionChapter 1. Introduction

Goals of Image ProcessingGoals of Image Processing

“One picture is worth more than a thousand words”

1. Improvement of pictorial information for human interpretation.

2. Processing of scene data for autonomous machine perception.

Related Areas of Image Related Areas of Image ProcessingProcessing

• Image Processing: image image

• Computer Graphics: information image

• Computer Vision: image information

1. Image Analysis

2. Image Restoration

3. Image Enhancement

4. Image Compression

Applications of Image Applications of Image ProcessingProcessing

Example of Image RestorationExample of Image Restoration

Example of Image Example of Image EnhancementEnhancement

Steps in Digital Image Steps in Digital Image ProcessingProcessing

Digital ImageDigital Image

Sampling & Sampling & QuantizationQuantization

SamplingSampling

QuantizationQuantization False contours

Storage requirementStorage requirement

A MxN image with 2k gray scales

# of storage bits = M x N x k

ExampleExample

Generally, transmission is Generally, transmission is accomplished in packets consisting of accomplished in packets consisting of a start bit, a byte of information, and a a start bit, a byte of information, and a stop bit. Using this approach, how stop bit. Using this approach, how many seconds would it take to many seconds would it take to transmit a 1024x1024 image with 256 transmit a 1024x1024 image with 256 gray levels at 300 baud (bits/sec)?gray levels at 300 baud (bits/sec)?

Types of ImagesTypes of Images

Analog Image

Digital Image1. Binary Image2. Gray-scale Image3. Color Image4. Multispectral Image

MultispectrMultispectral Imageal Image

Electromagnetic SpectrumElectromagnetic Spectrum

Vector Image

Bitmap Image• RAW no header• RLE (Run-Length Encoding)• PGM,PPM,PNM (Portable Gray Map)• GIF (Graphics Interchange Format) no more than 256 colors• TIF (Tag Image File Format) Scanner• EPS (Encapsulated Postscript) Printer• JPEG (Joint Photographic Experts Group) Compression ratio• MPEG (Motion Picture Experts Group) Video

Image FormatsImage Formats

Comparison of Image Comparison of Image FormatsFormats

Human Visual PerceptionHuman Visual Perception

Machine Visual PerceptionMachine Visual Perception

Perception of objectsPerception of objects

1. The spectrum (energy) of light source.

2. The spectral reflectance of the object surface.

3. The spectral sensitivity of the sensor (eye or camera).

Human Human eyeeye

How do we see an object?How do we see an object?

Light

Object

Eye

• Luminance Lightness Rods• Chrominance Color Cones

Human eye is more sensitive to luminance than to chrominance

Cones & RodsCones & Rods( day & night )( day & night )

Three kinds of ConesThree kinds of Cones

Brightness adaptationBrightness adaptation

Brightness Brightness illusions: illusions:

Mach band effectMach band effect

Contrast illusionsContrast illusions

Geometric illusionsGeometric illusions

Spatial & Temporal Spatial & Temporal ResolutionResolution

• Spatial resolution: 4-50 cycles per Spatial resolution: 4-50 cycles per degreedegree

• Temporal resolution: 50 cycles per Temporal resolution: 50 cycles per secondsecond

• Brightness resolution: 100 gray levelsBrightness resolution: 100 gray levels

Color Color SpectruSpectrumm

Electromagnetic spectrumElectromagnetic spectrum

RGB ModelRGB Model

RGB ModelRGB Model

RGB signals from a video RGB signals from a video cameracamera

• Color measurement: •A mixture of red, green, and blue light •Values between 0.0 (none) and 1.0 (lots)

• Color examplesRed Green Blue

White 1.0 1.0 1.0 Black 0.0 0.0 0.0 Yellow 1.0 1.0 0.0 Magenta 1.0 0.0 1.0 Cyan 1.0 1.0 0.0

RGB ModelRGB Model

rgb Model(Normalized RGB)rgb Model(Normalized RGB)

r+g+b=1

ChromaticiChromaticity ty DiagramDiagram

Typical Typical color color gamutgamut

HSI ModelHSI Model

HSI ModelHSI Model

Color ComplementsColor Complements

CMY ModelCMY Model

B

G

R

Y

M

C

1

Light Light vs. vs. PigmenPigmentt

YIQ ModelYIQ Model

B

G

R

Q

I

Y

311.0523.0212.0

321.0275.0596.0

114.0587.0299.0

• TV transmission digital space YCBCR

analog space YIQ (NTSC) YUV (PAL)

YUV & YCYUV & YCBBCCRR Model Model

B

G

R

YR

YB

Y

V

U

Y

10.052.061.0

45.029.015.0

11.059.030.0

)(877.0

)(493.0

B

G

R

YR

YB

Y

C

C

Y

r

b

08.042.05.0

5.033.017.0

11.059.030.0

)(713.0

)(564.0

TV BroadcastTV Broadcast