Computer Vision – Overview

1. Computer Vision – Overview Hanyang University Jong-Il Park

2. Digital Image Processing • Sampling & Quantization • Image Enhancement • Image Restoration • Image Coding( or Image Data Compression) • Image Understanding( or Computer Vision)

3. Image formation

4. Sampling & Quantization

6. Subsampling & aliasing aliasing

7. Sub-Nyquist sampling Circular Zone Plate H ½, v ½ Org. aliasing

8. Image Enhancement • Goal • to accentuate certain image features for subsequent analysis or for image display Input : image Output : image

11. Image Enhancement • Techniques • contrast/edge enhancement • histogram equalization • pseudo coloring • noise filtering • edge sharpening • smoothing • Applications • processing of remote-sensed image via satellite • radar, SAR, Ultrasonic image processing

12. Image Restoration • Goal • to remove or minimize known/unknown degradations in image

14. Blur model  estimate or recover f(x,y) from g(x,y)  deconvolution problem

15. Enhancement by integration

16. Image Restoration • Techniques • deblurring • noise filtering • correction of geometric distortion • inverse filtering • Least mean square(Wiener) filtering • Applications • remote-sensed image processing • noise cancellation

17. Image Data Compression • Goal • to reduce the amount of data required to represent images Input : image Output : bit-stream data “010100101100110101001 . . . .” moving image: 1,0001,0008(bits/sample)330 frame/sec = 72107 bit/sec

18. 2-D Image Compression, JPEG • Image quality by JPEG (a) 27.9 dB at 0.125 bpp (b) 31.5 dB at 0.25 bpp (c) 34.8 dB at 0.5 bpp

21. 3D Mesh Compression Original ‘Bunny’ 12 bpc 10 bpc 8 bpc

22. Image Data Compression • Techniques • Error-free coding( or lossless coding) • Lossy compression • Image Compression Standard • JPEG, H.261, H.263, MPEG-1,2,4 etc • Applications • Transmission • teleconferencing ,TV system, remote sensing via satellite • Storage • VOD(video on demand), Video CD, DVD(digital video disk), medical imaging, educational and business documents

23. Image Coding Standards

24. MPEG • MPEG-1 • 1992 • Video CD • Includes Audio Layer III (MP3) • MPEG-4 • Part 1: 1998 • Part 2: 1999 (addition still under development) • Audio visual object • Mobile telephony (IMT-2000) • Interactivity • Content –Based Interactivity

25. MPEG-7 • 2001 (addition still under development) • Content Description Interface • Metadata language and schemes for search & retrieval

26. Content-based Image Retrieval • Image retrieval • Find similar images from image database • Used features • Color • Texture • Shape Query Retrieved

27. Query Image Retrieval Results Image Data List Texture Option

28. Content-based Video Retrieval • Video retrieval • Scene change detection and key frame extraction • Extracted key frame from a movie clip

29. Content-based Video Retrieval • Video retrieval • Automatic indexing • Index from a news sequence

30. Media Framework Tech. • MPEG-21 • All electronic creation, delivery and trade of digital multimedia content • Transparent usage of various content types on various devices connected through various network

31. Watermarking • the process of embedding information into a host signal without changing perceived characteristics of the host

32. Image Understanding • Goal • to interpret or describe the meaning contained in the image Input : image Output : interpretation(description) “KAISION” “circle”

35. Stereo Vision (disparity map) 기준 영상(좌) 기준 영상(우) 구한 변위 지도(검은색: 가리워짐) 변위 참 값(붉은색: 가리워짐)

36. Model image Model Input scene Scene Matching (1) Scene matching result

37. Model Scene matching result Input image Edge image Scene Matching (2)

38. Fruit Classifier • Apple • Orange • Water Mellon –크기, 반지름

39. – color

40. Edge Detection

41. Segmentation (a) Aerial Original Image (b) Segmented Image

43. There are a lot of interesting topics to explore in image processing and computer vision.