1. S. Mandayam/ DIP/ECE Dept./Rowan University Digital Image Processing 0909.452.01/0909.552.01 Fall 2001 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall01/dip/ Lecture 10 November 19, 2001

2. S. Mandayam/ DIP/ECE Dept./Rowan University Grad Students: Final Project Presentations Dec 10 th Dec 17 th

3. S. Mandayam/ DIP/ECE Dept./Rowan UniversityPlan Digital Image Compression Fundamental principles Image Compression Model Recall: Information Theory Image Compression Standards CCITT Group 3 (FAX): Lossless LZW (GIF, TIFF, ZIP): Lossless DCT (JPEG): Lossy Lab 4: Digital Image Compression

4. S. Mandayam/ DIP/ECE Dept./Rowan University DIP: Details

5. S. Mandayam/ DIP/ECE Dept./Rowan UniversityFundamentals Justification Applications Principle Redundancy Types Lossy Lossless demos/demo6dithering/

6. S. Mandayam/ DIP/ECE Dept./Rowan University Compression Model f(x,y) Transform Quantize Encode Source Channel

7. S. Mandayam/ DIP/ECE Dept./Rowan University Recall: Measures of Information Definitions Probability Information Entropy Source Rate Recall: Shannon’s Theorem If R < C = B log 2 (1 + S/N), then we can have error- free transmission in the presence of noise MATLAB DEMO: http://engineering.rowan.edu /~shreek/spring01/ecomms/ entropy.m

8. S. Mandayam/ DIP/ECE Dept./Rowan University Recall: Source Encoding Why are we doing this? Analog Message A/D Converter Digital Source Encoder Source Symbols (0/1) Source Entropy Encoded Symbols (0/1) Source-Coded Symbol Entropy

9. S. Mandayam/ DIP/ECE Dept./Rowan University Source Encoding Requirements Decrease L av Unique decoding Instantaneous decoding

10. S. Mandayam/ DIP/ECE Dept./Rowan University Recall: Huffman Coding 2-Step Process Reduction List symbols in descending order of probability Reduce the two least probable symbols into one symbol equal to their combined probability Reorder in descending order of probability at each stage Repeat until only two symbols remain Splitting Assign 0 and 1 to the final two symbols remaining and work backwards Expand code at each split by appending a 0 or 1 to each code word Example m(j)ABCDEFGH P(j)0.10.180.40.050.060.10.070.04

11. S. Mandayam/ DIP/ECE Dept./Rowan University CCITT Group 3 1-D Standard for Bilevel Image Compression Determine “run lengths” of black and white pixels on each line Code these using a Huffman code Conventions: Each line begins with a zero-run length white code word Each line ends with a special EOL code black run length white run length http://www.itu.int/publibase/itu-t/

12. S. Mandayam/ DIP/ECE Dept./Rowan University LZW Algorithm Initialize string table with single character strings Read first input character = w Read next input character = k No more k’s? Output = code(w) Stop wk in string table? Output = code(w) w = wk w = k Put wk in string table y n n y United States Patent No. 4,558,302, Patented by Unisys Corp.

13. S. Mandayam/ DIP/ECE Dept./Rowan University Discrete Cosine Transform Information Concentration Data Compaction Feature Extraction Discrete Cosine Transform >>dctdemo

14. S. Mandayam/ DIP/ECE Dept./Rowan University Laser Based Ultrasound* *Karta Technologies Inc., San Antonio, TX

15. S. Mandayam/ DIP/ECE Dept./Rowan University Example: Photothermal Shearography Images Before Deformation - After Deformation = Fringe Pattern Sample 10 0.254 mm depth -605.36 MPa stress

16. S. Mandayam/ DIP/ECE Dept./Rowan UniversityPreprocessing Fringe Pattern DCT DCT Coefficients Zonal Mask 1 23451 2345 1 2 3 4 5 (1,1) (1,2) (2,1) (2,2). Feature Vector Artificial Neural Network

17. S. Mandayam/ DIP/ECE Dept./Rowan University JPEG Compression Standard f(x,y) Level Shift Compute DCT F(u,v) Normalize Reorder to form 1-D Sequence Compute DC Coefficient Compute AC Coefficients http://www.jpeg.org/

18. S. Mandayam/ DIP/ECE Dept./Rowan University Karhunen-Loeve (Hotelling) Transform Hotelling transform of x demos/demo7klt/

19. S. Mandayam/ DIP/ECE Dept./Rowan University Lab 4: Digital Image Compression http://engineering.rowan.edu/~shreek/fall01/dip/lab4.html

20. S. Mandayam/ DIP/ECE Dept./Rowan UniversitySummary