Image Image coding/compression coding/compression EE5364 DSP Project Pradeep Suthram, David Hemmert, Tammo Heeren All Mathcad files [MCD/PDF] can be found on: http:// webpages . acs . ttu . edu / theeren
Dec 27, 2015
Image coding/compressionImage coding/compression
EE5364 DSP Project
Pradeep Suthram, David Hemmert, Tammo Heeren
All Mathcad files [MCD/PDF] can be found on:http://webpages.acs.ttu.edu/theeren
OverviewOverview
Quantization– Linear quantization– Adaptive quantization
Compression– DCT– JPEG– Wavelet
Linear QuantizationLinear Quantization
Image intensities are quantized into equidistant quantization steps [Mathcad 2001 File]
0 17 34 51 68 85 102 119 136 153 170 187 204 221 238 2550
17
34
51
68
85
102
119
136
153
170
187
204
221
238
255Quantization steps
Grayscale levels
quan
tized
gra
ysca
le le
vels
Linear Quantization SNRLinear Quantization SNR
1 2 3 4 5 6 7 80
10
20
30
40
50
60SNR vs. grayscale resolution
Grayscale resolution [Bits]
SN
R [
dB]
6.2dB per grayscale bit
Adaptive QuantizationAdaptive Quantization
Quantization steps are scaled by the characteristic image probability density function [Mathcad 2001 File]
0 17 34 51 68 85 102 119 136 153 170 187 204 221 238 2550
17
34
51
68
85
102
119
136
153
170
187
204
221
238
255Quantization steps
Grayscale levels
quan
tized
gra
ysca
le le
vels
0 17 34 51 68 85 102 119 136 153 170 187 204 221 238 2550
17
34
51
68
85
102
119
136
153
170
187
204
221
238
255Quantization steps
Grayscale levels
quan
tized
gra
ysca
le le
vels
Adaptive Quantization resultsAdaptive Quantization results
Adaptive quantization Linear quantization
Adaptive Quantization SNRAdaptive Quantization SNR
1 2 3 4 5 6 7 80
10
20
30
40
50
60SNR vs. grayscale resolution
Grayscale resolution [Bits]
SN
R(d
B]
5.6dB per grayscale bit for adaptive quantization [red]6.2dB per grayscale bit for linear quantization [blue]
8x8 pixel block
DCT QuantizerLevel-shift Encoder Data
• Lenna BMP file used
• Gray scale image level-shifted by –128
• for n = 8, 2^(n-1) = 128
JPEG AlgorithmJPEG Algorithm
Quantization
using a typical normalization matrix
[ 16 11 10 16 24 40 51 61
12 12 14 19 26 58 60 55
14 13 16 24 40 57 69 56
14 17 22 29 51 87 80 62
18 22 37 56 68 109 103 77
24 35 55 64 81 104 113 92
49 64 78 87 103 121 120 101
72 92 95 98 112 100 103 99 ]
Encoding
• Zig-Zag Pattern
• Huffman Coding
• Run-length Coding
• Tables
DC
Size | Amplitude
AC
Run/Size | Amplitude
JPEG AlgorithmJPEG Algorithm
References:References:
1. Rafael C. Gonzalez, Richard E. Wood, “Digital Image Processing”, Addison Wesley, 1993
2. Geoffrey M. Davis, Aria Nosratinia, “Wavelet-based Image Coding: An Overview”, http://www.geoffdavis.net/
3. Subhasis, Saha, “Image Compression - from DCT to Wavelets : A Review”, http://www.acm.org/crossroads/xrds6-3/sahaimgcoding.html
4. Weidong Kou, “Digital Image Compression Algorithms and Standards,” Kluwer Academic Publishers, 1995.
5. “Selected Papers on Image Coding and Compression,” Majid Rabbani, Ed., Brian J. Thompson, Gen. Ed., SPIE Milestone Series, Vol MS-48, SPIE Optical Engineering Press, 1992.
6. “Fractal Image Compression Theory and Application,” Yuval Fisher, Ed., Springer-Verlag New York, 1995.
7. Bernd Jaehne, “Digital Image Processing”, Third Edition, Springer-Verlag, New York 1995