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© 2002 R. C. Gonzalez & R. E. Woods
Chapter 2 Digital Image fundamentalsChapter 2 Digital Image fundamentals
2.1 Elements of visual perception
2.2 Light and the electromagnetic spectrum
2.3 Image sensing and acquisition
2.4 Image sampling and quantization
2.5 Some basic relationships between pixels
2.6 Linear and Nonlinear Operations
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.1 Elements of visual perception 2.1 Elements of visual perception
2.1.1 Structure of the Human Eye 2.1.1 Structure of the Human Eye
,
( )
≈20mm
Conjunctiva Pupil
© 2002 R. C. Gonzalez & R. E. Woods
Light ReceptionLight Reception
Cones
6-7millions sensitive to Color Photopic or Bright-light vision
Rods
75-150millions Scotopic or Dim-light vision
2.1 Elements of visual perception 2.1 Elements of visual perception
2.1.1 Structure of the Human Eye 2.1.1 Structure of the Human Eye
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.1 Elements of visual perception 2.1 Elements of visual perception
2.1.1 Structure of the Human Eye 2.1.1 Structure of the Human Eye
© 2002 R. C. Gonzalez & R. E. Woods
2.1 Elements of visual perception 2.1 Elements of visual perception
2.1.2 Image formation in the Eye2.1.2Image formation in the Eye
– Len
– Fovea
14mm ~ 17mm
2.55mm
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
^ 2.1.32.1.3 Brightness adaptation and discriminationBrightness adaptation and discrimination
– Subjective Brightness is a logarithm function
– The total range of distinct intensity levels it can
discriminate simultaneously is rather small
milliLambert:
2.1 Elements of visual perception 2.1 Elements of visual perception
© 2002 R. C. Gonzalez & R. E. Woods
2.1 Elements of visual perception 2.1 Elements of visual perception
A classic experiment for brightness discriminationA classic experiment for brightness discrimination
– Weber Ratio : ∆ Ic / I
- a small value means Good brightness discrimination
- a large value means Poor brightness discrimination
– the typical observer can discern 1~2 dozen different
intensity changes
Scotopic Photopic
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.1 Elements of visual perception 2.1 Elements of visual perception
^ Two examplesTwo examples
to demonstrate the perceived brightness is not a simple
function of intensity
Mach Bands - 1865, Ernst Mach
© 2002 R. C. Gonzalez & R. E. Woods
2.1 Elements of visual perception 2.1 Elements of visual perception
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.1 Elements of visual perception 2.1 Elements of visual perception
© 2002 R. C. Gonzalez & R. E. Woods
2.1 Elements of visual perception 2.1 Elements of visual perception
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.1 Elements of visual perception 2.1 Elements of visual perception
© 2002 R. C. Gonzalez & R. E. Woods
2.1 Elements of visual perception 2.1 Elements of visual perception
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.2 Light and the Electromagnetic Spectrum 2.2 Light and the Electromagnetic Spectrum
^ Electromagnetic Spectrum(Electromagnetic Spectrum(^ ))
© 2002 R. C. Gonzalez & R. E. Woods
Wavelength λ
h = 6. 626068 × 10 −^34 Js 1 eV = 1. 6 × 10 −^19 J
2.2 Light and the Electromagnetic Spectrum 2.2 Light and the Electromagnetic Spectrum
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.2 Light and the Electromagnetic Spectrum 2.2 Light and the Electromagnetic Spectrum
Visible Band
430um~790nm Illuminant ( ) reflected light from objects ( ) Achromatic or Monochromatic (Gray Level) Chromatic - Color Light Source Radiance ( ) - measured in Watts Luminance ( ) - measured in lumens Brightness ( ) - subjective descriptor
© 2002 R. C. Gonzalez & R. E. Woods
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
2.3.12.3.1 Image acquisition using a single sensorImage acquisition using a single sensor
Photodiode( )
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
^ 2.3.22.3.2 Image acquisition using sensor stripsImage acquisition using sensor strips
Scanning Direction
CAT MRI PET
Flatbed Scanner
© 2002 R. C. Gonzalez & R. E. Woods
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
2.3.32.3.3 Image acquisition using sensor arraysImage acquisition using sensor arrays
Charged Couple Diode (CCD)
IrisLens Digital Camera
SunLamp Flash
CCDCMOS
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
© 2002 R. C. Gonzalez & R. E. Woods
Typical values of i(x,y)
i = 90000 lm/m^2 i = 10000 lm/m^2 i = 0.1 lm/m^2 i = 1000 lm/m^2
Typical values of r(x,y)
r = 0. r = 0. r = 0. r = 0. r = 0.
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
Intensity at (x 0 , y0 )
[ Lmin , L max ] is called gray scale
Shift this interval to [0, L - 1]
l = 0 is black l = L - 1 is white All intermediate values are shades of gray
l = f ( x 0 , y 0 ) (2.3-5)
L min ≤ l ≤ L max (2.3- 6)
L min = i min r min
L max = i max r max
2.3 Image Sensing and Acquisition 2.3 Image Sensing and Acquisition
© 2002 R. C. Gonzalez & R. E. Woods
2.4 Image sampling and quantization 2.4 Image sampling and quantization
2.4.1 Basic concepts in sampling and quantization2.4.1 Basic concepts in sampling and quantization
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.4 Image sampling and quantization 2.4 Image sampling and quantization
Sampling ( Sampling ( )) Quantization (Quantization( ))
© 2002 R. C. Gonzalez & R. E. Woods
2.4 Image sampling and quantization 2.4 Image sampling and quantization
2.4.3 Spatial and Gray-Level Resolution2.4.3 Spatial and Gray-Level Resolution
Spatial Resolution
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com
2.4 Image sampling and quantization 2.4 Image sampling and quantization
© 2002 R. C. Gonzalez & R. E. Woods
2.4 Image sampling and quantization 2.4 Image sampling and quantization
Gray-Level Resolution
Digital Image Processing, 2nd ed. Digital Image Processing, 2nd ed. (^) www.imageprocessingbook.com 2.4 Image sampling and quantization 2.4 Image sampling and quantization
Gray-Level Resolution
