Chapter 8: Image CompressionChapter 8: Image Compression
Images with (a) coding redundancy; (b) spatial redundancy; (c) irrelevant information
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
For the image in Fig. 8.1(a):
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
M i I I f tiMeasuring Image Information
Note that the entropy of Fig.8.1(b) is 8 bits/pixel and that of Fig. 8.1(c) is 1.566 bits/pixel
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Fid li C i iFidelity Criteria
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
The rms of the three images are 5.17, 15.67, and 14.17.
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Some Basic Compression Methods
Huffman coding:
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Huffman coding example:
The entropy of the original image is 7.3838 bits/pixelAfter compression, the number of bits/pixel is 7.428 including the code table.
© 1992–2008 R. C. Gonzalez & R. E. Woods
Hence, C=8/7.428=1.077, R=1- (1/1.077)=0.0715
Chapter 8: Image CompressionChapter 8: Image Compression
A ith ti diArithmetic coding: - An entire sequence of source symbols is assigned a single code- No one-to-one correspondence between source symbols and code
dwords
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
The entropy of the original image is 0.58 decimal digits per source symbol.
After coding 3 decimal digits are required for the 5-After coding, 3 decimal digits are required for the 5symbol message – 0.6 decimal digits/source symbol
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
LZW coding:-Assigns fixed-length code words to variable-length source sequence- Spatial redundancy is exploited- Spatial redundancy is exploited- Used in a number of imaging file formats like GIF, TIFF, PDF ..
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Construction of a codebook or “dictionary” containing the source symbol.
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
R l th di ti l l it bl f bi iRun-length coding: particularly suitable for binary images
BMP file format – use 2-byte format(a) encoded mode: 1st byte shows # of consecutive pixels;
and 2nd byte gives color index.(b) absolute mode: 1st byte is 0; 2nd byte is shown below( ) y ; y
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Bit Pl C diBit-Plane Coding:Decompose an image into a series of binary images and compress each binary image via one of several well-known p y gbinary compression methods
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Bl k T f C diBlock Transform Coding:
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
The choice of a particular transform in a given application depends on the amount ofapplication depends on the amount of reconstruction error that can be tolerated and the computational resources available.
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Periodicity of DFT and DCT
Gibbs effect
No Gibbs effect
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Selection of subimage size
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
L l di ti diLossless predictive coding
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Lossy predictive codingLossy predictive coding
Delta modulation
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
O ti l di tOptimal predictor
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Optimal quantizer
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Wavelet coding
W l t Bl kWavelet vs. Block No subdivision of the original imageNo block artifact
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
Digital Image Watermarking
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
© 1992–2008 R. C. Gonzalez & R. E. Woods
Chapter 8: Image CompressionChapter 8: Image Compression
W ki i DCT d iWatermarking in DCT domain
© 1992–2008 R. C. Gonzalez & R. E. Woods
Top Related