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What is Image Compression?. Reduction of amount of data based on removal of redundant data Mathematically: transferring an image into a statistically uncorrelated data set. What kind of redundancy?. Coding redundancy Psychovisual redundancy Interpixel redundancy. Why Compression?.
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What is Image Compression? • Reduction of amount of data based on removal of redundant data • Mathematically: transferring an image into a statistically uncorrelated data set
What kind of redundancy? • Coding redundancy • Psychovisual redundancy • Interpixel redundancy
Why Compression? • Essential in data storage and data transmission • Examples • Transmission of image/video • Digital library and image databases • Remote sensing • Medical imaging and telemedicine
Digital image • A digital image is a two-dimensional sequence of samples
Lossless vs. Lossy Compression • Lossless or information preserving compression: Images can be compressed and restored without any loss of information (e.g. medical imaging) • Lossy compression: Perfect recovery is not possible but we can have larger data compression (e.g. telemedicine)
Lossy Compression • Quantizer
DICOM Compression • JPEG (JPEG-LS) • Lossless or lossy • Simple, fast and low memory requirement • JPEG 2000 • Lossless or lossy • Progressive (contrast or spatial) • ROI encoding (fewer bits for background)
JPEG 0.125 0.25 0.5 1.0 Original
JPEG 2000 0.125 0.25 0.5 1.0 Original