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Color Image Coding by Modified
Embedded Zerotree Wavelet (EZW)
Algorithm
Ouafi, Zitouni, ” Information and Communication
Technologies, ICTTA '06. 2nd ”, Damascus, pp. 1451 –
1456, 17-19 Oct. 2006.
Student : Chien-Nan Lin
Outline
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Introduction
Review
Proposed Algorithm
Experimental Results
Introduction
A new approach of images coding by EZW
algorithm is proposed.
advantage:
improvement on the PSNR and compression
ratio.
Outline
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Introduction
Review
Proposed Algorithm
Experimental Results
Review
EZW :
LL3 HL3
HL 3
LH 3
HH 3
LH3 HH3
LH 2
HL1
HH2
LH2
HL 2
Image
HH 2
DWT
LH 1
LH1
HL 1
HL2
HH 1
HH1
Review
EZW :
1. Dominant pass
2. Subordinate pass
60
34
45
8
7
13
--10
7
--30
22
14
-6
3
4
6
--1
13
15
3
-8
5
--7
3
6
--9
--7
--14
8
4
--2
3
2
--5
8
--1
42
2
6
--2
2
3
0
--3
2
3
--2
0
4
2
--3
6
--6
3
4
2
5
5
8
2
6
0
3
--4
4
Review
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P: a positive coefficient greater than the current
threshold.
N: a negative coefficient greater than the
current threshold
T: (zerotree): a zero tree root. This coefficient
and all of its descendants are below the current
threshold.
Z: (isolated zero): an isolated zero, or a
coefficient that is below the current threshold
but is not a zerotree root.
Review
T=32 ( Threshold = 2 log 2 60  )
Dominate pass：PS(60)、PS(34)、IZ(-30)、
ZR(22)、PS(45)、ZR(8)、
ZR(14)、ZR(-6)、ZR(13)、
IZ(15)、ZR(-9)、ZR(-7)、
ZR(7)、ZR(13)、ZR(3)、ZR(4)、
ZR(-1)、PS(42)、ZR(-3)、ZR(2)
Subordinate pass：UP、Lo、Lo、Lo
Outline
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Introduction
Review
Proposed Algorithm
Experimental Results
Proposed Algorithm
In our MEZW algorithm, the six symbols (P,
N, Z, T, Pt and Zt).
if all the descendants are judged insignificant,
the coefficients are coded using the symbols
Pt for positive coefficients and Nt for negative
coefficients.
Proposed Algorithm
each one is coded on three bits.
 If the significant coefficient is in the root
, then a symbol Pt,(or Nt), in MEZW
algorithm, represents four symbols "PTTT'
(or "NTTT') in EZW algorithm.
 If the significant coefficient is not in the root
, then a symbol Pt,(or Nt), in MEZW
algorithm, represents four symbols "PTTTT'
(or "NTTTT') in EZW algorithm.
Proposed Algorithm
As example
EZW:PNZTPTTTTZTTZZZZZPZZ
MEZW:PNZTPtZTTZZZZZPZZ
Pt
PTTTT
Outline
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Introduction
Review
Proposed Algorithm
Experimental Results
Experimental Results