1 Vladimir Botchko [email protected] Lecture 6. Image Compression Lappeenranta University of Technology (Finland)

1

Vladimir Botchko [email protected]

Lecture 6. Image CompressionLecture 6. Image Compression

Lappeenranta University of Technology (Finland)

2

Image CompressionImage Compression

Lossy and lossless compression Fundamentals Fidelity Criteria Image Compression Models Error Free Compression Lossy Compression Compression Standards Video Image Compression

3

FundamentalsFundamentals

Coding redundancy Interpixel Redundancy Psychovisual Redundancy

4

Image CompressionImage Compression

Lossy and lossless compression Fundamentals Fidelity Criteria Image Compression Models Error Free Compression Lossy Compression

5

Image CompressionImage Compression

Lossy and lossless compression Fundamentals Fidelity Criteria Image Compression Models Error Free Compression Lossy Compression

6

Error Free CompressionError Free Compression

Variable-length coding Huffman coding Near optimal variable length codes Lossless predictive coding

7

One-dimensional predictive coding

Right histogram is a Laplacian pdf

8

Image CompressionImage Compression

Lossy and lossless compression Fundamentals Fidelity Criteria Image Compression Models Error Free Compression Lossy Compression

9

Lossy CompressionLossy Compression

Delta Modulation DM Differential pulse code modulation DPCM Transform coding

10

Lossy CompressionLossy Compression

Delta Modulation DM Differential pulse code modulation DPCM Transform coding

11

Transform CodingTransform Coding

Transform basis functions Fourier transform Walsh-Hadamard transform Discrete cosine transform Wavelet transform

12

Transform CodingTransform Coding

ON-LINE DEMO on the course Web page (browser with Java 2): References: Dmitry Kolesnikov: Introduction Lecture

13

Walsh-Hadamard transform

Walsh-Hadamard basis images: one – black, minus one – white.

14

Transform CodingTransform Coding

Transform basis functions Fourier transform FT Walsh-Hadamard transform WHT Discrete cosine transform DCT Wavelet transform WT

15

DCT

Image udersampling (upper row), DCT (lower row)

16

Transform CodingTransform Coding

Transform basis functions Fourier transform Walsh-Hadamard transform Discrete cosine transform Wavelet transform

17

Haar transform

Haar basis images: positive-black, negative-white, zero-gray

18

Wavelet Transform (1 level decomposition)

19

Wavelet Transform (2 level decomposition)

20

Wavelet transform

Wavelets (upper row), image undersampling (lower row), compare with DCT

21

Image CompressionImage Compression

Lossy and lossless compression Fundamentals Fidelity Criteria Image Compression Models Error Free Compression Lossy Compression Compression Standards Video image compression

22

Video image compression

A moving image sequence 192 kB/frame (left), intra (independetly inside frame) frame compression 6 kB/frame (center), inter (by subtraction of frames) frame compression 512 bytes/frame and intra compression is also kept (right).

MPEG format.

23

Gray-scale image compression. Fractals.

f