Color image compression based on block truncation coding using pattern fitting principle

1. Color image compression based on block truncation coding using pattern fitting principle

2. Outline • Introduction • Related works • Block truncation coding (BTC) • BTC pattern fitting (BTC-PF) • Proposed method(CBTC-PF) • RGB to O1 O2 O3conversion • O1plane encoding • O2 O3plane encoding • O1 O2 O3plane decoding • Experimental results • Conclusions

3. Introduction • In true-color digital image, each color component (R,G,B) is usually quantized with 8-bits, so a color is specified by 24 bits per pixel. • To reduce storage space or transmission cost image compression is the solution.

4. Related works (1/2) • Block truncation coding(BTC) 16bits Original gray level image Bit pattern Reconstruct image 8bits Bits per pixel = 32/16 =2(bpp) 8bits (96, 146, (1000100011101111)2)

5. Related works (2/2) • BTC pattern fitting (BTC-PF) Original image Bit pattern Reconstruct image Pattern book ej0 = (89 - 110)2 + (90 - 110)2+ … +(143 – 110)2 ej1 = (146 - 139)2 + (97 - 139)2 + … +(147 – 139)2 Find minimum (ej0 + ej1)

6. Proposed method (1/8) • RGB to O1 O2 O3conversion R G B O1 O2 O3

7. Proposed method (2/8) • O1plane encoding 1. First column and first row blocks 2. Residual blocks v h

8. Proposed method (3/8) • O1plane encoding Smooth block Non-smooth block

9. Proposed method (4/8) • O1plane encoding I0

10. Proposed method (5/8) • O2 & O3plane encoding Two 4×4 sub-blocks derived from 8×8 block by Quincunx sampling. 2-Level patterns used to define the gray-levels of 4 × 4 sub-blocks generated from O2 and O3 planes.

11. Proposed method (6/8) • O2 & O3plane encoding A - d A + d Original image Bit pattern Reconstruct image

12. Proposed method (7/8) • O2 & O3plane encoding Smooth block Non-Smooth block

13. Proposed method (8/8) • O1 O2 O3decoding O1plane (1) BTC-PF Original block (2) BTC-PF Residual block ---------------------------------------------------------------------------------------------------- O2 O3plane (1) BTC-PF (2) Reconstruction(interpolation)

14. Experimental results (1/4)

15. Experimental results (2/4)

16. Experimental result (3/4)

17. Experimental results (4/4)

18. Conclusions • Quality of image. • Low bit rates.

19. Thanks for your attention!

20. Proposed method • O2 & O3plane encoding (Smooth block) (1) If d’ = 0, we need not transmit the pattern index (2) Get the higher compression