JPEG standard
JPEG (Joint Photographic Experts Group) Reducing the size of photographic images or continuous-tone artwork – pictures JPEG compression can be performed on 24bit color or 8-bit grayscale images.
The inverse quantization coefficients
Rebuild image sub MB brightness value
The baseline process
Lossy Sequential DCT based mode DC components coding
8×8 block →DCT →DC coefficient DPCM Huffman coding
Part 2, Extensions (adds more features and sophistication to the core) Part 3, Motion JPEG 2000 Part 4, Conformance Part 5, Reference software (Java and C implementations are available) Part 6, Compound image file format (document imaging, for pre-press
enhancements to baseline process
Lossless mode
low compression ratio allows perfect reconstruction of original image
Hierarchical mode
accomodate images of different resolutions
JPEG coding system
The baseline process The extended process
Original image sub MB brightness value
Relative DCT coefficients
The quantization coefficients
JPEG Compression Arithmetic
DCT: lossy compression Predictive coding : lossless compression
JPEG image reconstruction mode：
Sequential decoding (line-by-line) ； Progressive decoding (refinement of the whole image)
Several typical image/video compression coding standard
H.261、H.263:TV Conference and Visual Telephone System；
JPEG、JPEG2000:Still Image Compression；
MPEG-1: VCD； MPEG-2: DTV、DVD、HDTV； MPEG-4: Multimedia Communication。
01111， Diff=-3，111111111100
01100
（1，-2） （0，-1） （0，-1） （0，-1） （2，-1）
NNNN/SSSS huffman code
0/100 0/201 0/3100 0/41011 …... 0/10 1/1 1/2 …... 1igzag scanning → Run-length coding Huffman coding
Example： Diff=7，000000000111
100111， Diff=-7，111111111000
100000， Diff=3，000000000011
and fax-like applications, etc.) Part 7 has been abandoned Part 8, JPSEC (security aspects) Part 9, JPIP (interactive protocols and API) Part 10, JP3D (volumetric imaging) Part 11, JPWL (wireless applications) Part 12, ISO Base Media File Format (common with MPEG-4)
Four different modes
Lossy Sequential DCT based mode
Baseline process that must be supported by every JPEG implementation.
Expanded Lossy DCT based mode
15/1 15/2 ...... 15/10
JPEG 2000 standard(ISO15444)
JPEG 2000 refers to all parts of the standard:
Part 1, Core coding system (intended as royalty and license-fee free NB NOT patent-free)
Key techniques of JPEG2000
Based on state-of-the-art wavelet compression
DCT: Wavelet: Reduce Blocking Artifacts DWT: multiresolution Others