Image coding/compression EE5364 DSP Project Pradeep Suthram, David - - PowerPoint PPT Presentation

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Jul 13, 2023 215 likes •367 views

Image 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 Overview l Quantization Linear quantization Adaptive quantization

SLIDE 1

Image 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

SLIDE 2

Overview

l Quantization

– Linear quantization – Adaptive quantization

l Compression

– DCT – JPEG – Wavelet

SLIDE 3

Linear Quantization

l Image intensities are quantized into equidistant quantization steps [Mathcad 2001 File]

17 34 51 68 85 102 119 136 153 170 187 204 221 238 255 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255

Quantization steps

Grayscale levels quantized grayscale levels

SLIDE 4

Linear Quantization results

1 Bit 8 Bit

SLIDE 5

Linear Quantization error

SLIDE 6

Linear Quantization SNR

1 2 3 4 5 6 7 8 10 20 30 40 50 60

SNR vs. grayscale resolution

Grayscale resolution [Bits] SNR [dB]

6.2dB per grayscale bit

SLIDE 7

Adaptive Quantization

l Quantization steps are scaled by the characteristic image probability density function [Mathcad 2001 File]

17 34 51 68 85 102 119 136 153 170 187 204 221 238 255 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255

Quantization steps

Grayscale levels quantized grayscale levels 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255

Quantization steps

Grayscale levels quantized grayscale levels

SLIDE 8

Adaptive Quantization results

Adaptive quantization Linear quantization

SLIDE 9

Adaptive Quantization error

(adaptive vs. linear)

SLIDE 10

Adaptive Quantization SNR

1 2 3 4 5 6 7 8 10 20 30 40 50 60

SNR vs. grayscale resolution

Grayscale resolution [Bits] SNR(dB]

5.6dB per grayscale bit for adaptive quantization [red] 6.2dB per grayscale bit for linear quantization [blue]

SLIDE 11

8x8 pixel block DCT Quantizer Level-shift Encoder Data

Lenna BMP file used
Gray scale image level-shifted by –128
for n = 8, 2^(n-1) = 128

JPEG Algorithm

SLIDE 12

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 Algorithm

SLIDE 13

To come:

l Compression

– DCT – JPEG decompression – Wavelet

SLIDE 14

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