1. Image Perception ‘Let there be light! ‘

2. “Let there be light”

3. Image perception “Let there be Newton, then comes the light light”

4. ELECTROMAGNETIC SPECTRUM AND VISIBLE BAND Can perceive 7% Cycle per second

5. Human Visual System Eye-Brain Channel brain eye Low level Acquisition Sampling Quantization Enhancement Restoration Compression High Level Enhancement + Restoration+ Compression+ Feature Extraction Labeling Understanding

6. EYE: Diameter:20mm Pupil 2mm Fovea: Sensors,rodes and cones A Feedback Control System: Adjusts the diameter of Eye ball Pupil Lenz

8. RODES 80-100 Million for Shape perception

9. CONES: 6-7 Million For color perception CONES: 6-7 Million For color perception

10. Cones:6-7 Milion

11. Sampling and quantization around the Fovea Cones: 6-7 million, located mostly on fovea, sensitive to color, each one is connected to a nerve cell Rodes:75-150 million, distributed over retina, sensitive to shape info, several of them is connected to the same nerve cell

14. In the Brain (60-70% is for vision) http://neuro.ceng.metu.edu.tr/fmri_prj/animations.html

15. In the Brain Gestalt Theory (Koffka 1935) LGN: Feature extraction, classification, texture analysis, recognition. Visual Cortex: –Scene representation –Interpretation –Knowledge manipulation –Hierarchical library of indexed feature –Task related to hierarchical vision

16. Lateral Geniculate Nucleus Primary Visual Cortex http://neuro.ceng.metu.edu.tr/fmri_prj/animations.html

18. ART (Grosberg, 1978) There are two state –Resonance –Reset

19. CHARATERSITICS OF HVS RESOLUTION: Ability to separate 1.Two adjacent pixels: Spatial Resolution 2.Two colors: Radiometric resolution 3.Two frames: Time resolution Response of HVS to resolution depends on the 1.Distance from the eye 2.Illumination

20. Low frequency High frequency f=2 f= 4 x direction 1.Spatial resolution

21. Field of viev Spatial Resolution is restricted by physical size of rodes and cones sampling rate of image

22. 2. Radiometric resolution: Response to intensity and color Pupil changes size according to the brightnes level What you see is different then what it is dark Glare limit quantization

23. Brightness adaptation is logarithmic function of intensity

24. Weber’s law: weber ratio =  I/I I: intensity,  I: increment of discriminable illumination Weber’s law: weber ratio =  I/I I: intensity,  I: increment of discriminable illumination rodes cones

25. MACH BAND EFFECT (Ernst Mach)

26. Simultaneous Contrast: backround effect the color of the object

27. 3. Temporal resolution response of HVS as a function of time Flicker frequency: ability to observe a flicker Depends on the brightness: 50 hertz

28. Visual Perception- Illusions

29. Simultaneous Contrast

32. HVS: Visual Illusion From Prof. E. H. Adelson

33. What is this? HVS: Visual Illusion

34. Which lines are straight? HVS: Visual Illusion

36. İmage acquisition devices Three types –Single sensor (scanners) –Sensor stripes (xerox, tomography), circular sensor stripes –Sensor arrays (cameras)

37. İmage acquisition: current technology

38. Chapter 2: Digital Image Fundamentals

40. Emerging technology: Single pixel camera Compressive sensing

41. Image Representation Continuous image: f(x,y), d= (x,y), r: Brightness values Digital image: both d and r is discrete Discrete image d is discrete, r is continuos Motion: f(x,y,t) Binary image: r  (0,1) Gray scale image r  (0.1,.......L-1) Color image f i (x,y), i=r,g,b Multispectral image: f i (x,y)

42. IMAGE SAMPLING: Digitize the domain of f(x,y) Generate an NxM matrix. How: Study sampling theorem IMAGE SAMPLING: Digitize the domain of f(x,y) Generate an NxM matrix. How: Study sampling theorem

43. IMAGE QUANTIZATION: Digitize the range of f(x,y)

44. Sampled and quantized image

45. f(x,y): storage space: NxMxkxT T: number of frames Number of gray values: L=2 k: f(x,y): storage space: NxMxkxT T: number of frames Number of gray values: L=2 k:

46. Storage Spaces: S= NxMxkxi i= # of bands L=2 k Storage Spaces: S= NxMxkxi i= # of bands L=2 k

47. SAMPLING

49. QUANTIZATION

50. Chapter 2: Digital Image Fundamentals

51. HOW TO SELECT SAMPLING AND QUANTIZATION RATES? HOW TO SELECT SAMPLING AND QUANTIZATION RATES?

52. Chapter 2: Digital Image Fundamentals

56. Storage Spaces: S= NxMxkxi i= # of bands L=2 k Storage Spaces: S= NxMxkxi i= # of bands L=2 k

57. Chapter 2: Digital Image Fundamentals