Browse Prior Art Database

Progressive Coding with Discrete Cosine Transforms

IP.com Disclosure Number: IPCOM000107937D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 55K

Publishing Venue

IBM

Related People

Feig, E: AUTHOR

Abstract

Disclosed is a progressive coding method utilizing Discrete Cosine Transforms for reproducing an image in various stages, the clarity of the image improving with each stage.

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This is the abbreviated version, containing approximately 68% of the total text.

Progressive Coding with Discrete Cosine Transforms

      Disclosed is a progressive coding method utilizing Discrete
Cosine Transforms for reproducing an image in various stages, the
clarity of the image improving with each stage.

      A preferred embodiment entails partitioning the image to 8 x 8
blocks, and taking the 8 x 8 quantized DCT of each block.  The
quantization is a function of the desired quality and average desired
compression rate.  The output of each block is sectioned into four
subblocks:  the top-left 4 x 4 subblock, labeled LL (low-low), the
top-right 4 x 4 subblock, labeled LH (low-high), the bottom-left 4 x
4 subblock, labeled HL (high-low), and the bottom-right 4 x 4
subblock, labeled HH (high-high).

      The LL subblock may be in-turn subband coded again; the
remaining three subblocks are coded with any of the good lossless
coding techniques used in image processing, such as Huffman coding or
arithmetic coding (including Q-coding), utilizing a zig-zag pattern
as described in the JPEG standards draft proposal, or any other
scanning order.

      The LL subblocks may be used to create an image which is half
the size of the original in each dimension and closely resembling the
original, by taking the 4 x 4 LL subblocks contiguously and
subjecting them to inverse quantized 4 x 4 DCTs.  For a fully
reconstructed image, all four subblocks are used, appropriately
arranged as 8 x 8 arrays, and subjected to 8 x 8 inverse quantized
DCTs.

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