Digital Image Processing #HW2

1. Digital Image Processing #HW2 RGB to YCbCr Conversion Background Subtraction & Denoising Using Morphological Operator Contact Information Tzu-Jui Wang (王子睿) Visual Communications Lab Dep. of Communications Engineering, National Central University No.300, JhongdaRd., JhongliCity, TaoyuanCounty 32001, Taiwan (R.O.C.) Phone: +886958801691 E-mail: juliuswang0728@gmail.com

2. Outline • Part #1 – RGB to YCbCr Conversion • Introduction to YCbCr • Part #2 – Background Subtraction & Denoising using morphological operator • Background Subtraction • Morphological operator • Dilation & Erosion • Opening operator • Grading Policy • Due Data & Demo Schedule

3. Introduction to YCbCr • Another color space. • Used in digital video and photography system. • Encode RGB information • Y – luminance (強度) • Cb – Chroma (彩度) of blue components • Cr – Chromaof red components

4. Introduction to YCbCr Cb component RGB space Cr component Y component

5. Introduction to YCbCr • Convert RGB to YCbCr • Show the images representing Y, Cb, Cr, respectively.

6. Background Subtraction • Visual “difference” always surprises machine ! (or human ) What I usually see…nothing’s new. Oops..! Whose slipper ?

7. Background Subtraction • How to detect the unusual objects ? • Simplest method : background subtraction • Possible application : event detection / analysis. － = ? Y component of foreground Y component of background

8. Background Subtraction • Find the difference of two images in Y component. • Produce binary images with proper threshold. Noises are everywhere ! The output

9. What’s the Problem ? • Luminance components are always affected by lights seriously ! • But how about Cb and Cr components ?

10. Denoising Using Morphological Operator • Dilation (膨脹) B : structure element (9.2-3) (9.2-4)

11. Denoising Using Morphological Operator • Erosion (侵蝕) B : structure element (9.2-1) (9.2-2)

12. Denoising Using Morphological Operator • Opening operator • Erode, and dilate. • Remove small object (noise), keep original shape. After processing with opening operator

13. Denoising Using Morphological Operator • Perfectly separate slipper and background.

14. Grading Policy • Part #1 • Output images in Y, Cb, Cr component, respectively. (2%) • Part #2 • Output image after background subtraction and thresholding (in binary form). (The noisy one) (2%) • Output two images, • After eroding. (1.5%) • After opening.(1.5%) • Report (3%)

15. Download Test Samples • The test samples can be downloaded at • http://140.115.156.251/vclab/html/course/DIP2010.html • .jpg files are provided, so you need to use MATLAB (or others ?) to access the pixel information. (BUT DON’T implement this assignment in MATLAB)

16. Due Date & Demo Schedule • 11/17, Thursday, 19:00, R3-307 (@VCLab). • Send your report before 19:00, 11/17. • juliuswang0728@gmail.com • .pdf file is preferred.

17. Due Date & Demo Schedule • Your report could be much better. • There’re many details you can give in this assignments • Which component used for background subtraction separates foreground and background better ? (or even fuse the subtraction results on multiple components ! You can try ) • How do you setup your thresholds ? • How do you define your size of square structure element ? • What if change the shape of the structure element ? • Fully discuss your wonderful design and the results.

18. Thanks, Good Luck !