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Learn about the differences between JPEG and JPEG2000 image compression standards, including algorithms, architectures, encoding processes, and quality comparisons. Explore the layered structure, functionalities, and applications of each standard.
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JPEG JPEG2000 JPEG - JPEG2000 Isabelle Marque Let's go Jackets!
JPEG • Joint Photographic Experts Group • Committe created in 1986 by: International Organization for Standardization (ISO) and International Telecommunication Union (ITU) • A working group which creates the standard for still image compression
JPEG - JPEG2000 • Two different standards • Major differences : JPEG JPEG2000 Created for natural imagery Discrete Cosine Transformalgorithm Created for computer generated imagery Discrete Wavelet Transform algorithm
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG • Architecture of standard • Forward transform • Quantization • Entropy coding • DC coefficient • AC coefficients
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG • Forward transform • Level shifted • Divided into blocks of 8*8 pixels • Forward DCT:
JPEG • DCT basis functions
JPEG • Original image
JPEG • DCT coefficients
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG • Quantization • Quantization table • Zigzag scan
JPEG • Quantization table
JPEG • Labels after quantization
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG • Entropy encoding • DC coefficient and AC coefficients are coded differently • DC coefficient • Encode the difference • Huffman code unmanageable • First bits to define the category and other bits to define the element in the category
JPEG • AC coefficients Defined by a certain number of terms: • Category C that a non zero label falls in • Z: number of zero since the last non zero label • Z/C points to a specific code • Follows by bits to define the element in the category • +1 code • EOB stands for End Of Block: A code after the last non zero value
JPEG • Sample table for obtaining the huffman code
JPEG • Reconstructed image
JPEG • More accurate image • Increase the bit rate • Decrease quantization table elements • Less accurate image • Decrease the bit rate • Increase quantization table elements • Problem: Low rate image: « blockiness »
JPEG2000 • Can be both lossless and lossy • Improves image quality • Uses a layered file structure : • Progressive transmission • Progressive rendering • File structure flexibility: • Could use for a variety of applications • Many functionalities
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG2000 • Architecture of standard • Forward transform • Quantization • Entropy coding
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG2000 • Forward transform • Level shifted • Divided into blocks • Forward Discrete Wavelet Transform
JPEG2000 • Details
JPEG2000 • Discrete Wavelet Transform can be : • Irreversible: Daubechies 9-tap/7-tap filter • Reversible: 5-tap/3-tap filter • Any user could supply wavelet filter banks
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG2000 • Quantization Dynamic range: depends on the number of bits and the choice of the wavelet Exponent Mantissa
Source image data Forward transform Entropy encoding Compressed image data Quantization JPEG2000 • Entropy encoding • Embedded Block Coding with Optimization Truncation of the embedded bit stream (EBCOT) • Each subband is divided into rectangular blocks which are coded independently called code blocks • Bitstream is organized in a succession of layers • Each layer corresponds to a certain distortion level • The quality of the reproduction is proportional to the numbers layers received
JPEG2000 • Layered structure
JPEG JPEG2000 JPEG - JPEG2000 - Quality • At compression ratio: 43:1
JPEG - JPEG2000 - Quality • Method of picture quality measurement:PSNR Peak Signal To Noise Ratio in dB: Pixel of the image Pixel of the reconstructed image Size of the image Root Mean Squared Error
JPEG - JPEG2000 - Quality • Comparison of PSNR values (dB) compressed colour images
CONCLUSION – Key points • JPEG: DCT algorithm • JPEG2000: DWT algorithm • Layered structure • Many functionalities • For a similar quality of PSNR, JPEG2000 compresses almost twice more than JPEG
REFERENCES • Introduction to Data Compression, K. Sayood, Morgan Kauffman, Second Edition, 2000. (Primary) • A.N. Skodra, C.A. Christopoulos, T. Ebrahimi, « JPEG2000, the upcoming still image compression standard », Proceeding of the 11th Portuguese Conference on Pattern recognition, Porto, Portugal, May 11th-12th, pp. 359-366, 2000 • JPEG, Official site: http://www.jpeg.org • Home page of a member: http://www.etro.vub.ac.be/members/christopoulos.charilaos/welcome.html • http://www.aware.com/products/compression/j2kmaindemo.html • http://www.cs.sfu.ca/CC/820/li/material/presentations/paper21.ppt • http://dmsun4.bath.ac.uk/research/sar/dwt.html • http://www.us.design-reuse.com/articles/article6691.html • PSNR:http://www.snellwilcox.com/knowledgecenter/whitepapers/papers/picturequality_mpeg2.pdf • Quality: http://jj2000.epfl.ch/jj_publications/papers/001.pdf