Browse Prior Art Database

A New Method for Transform Encoding of Images

IP.com Disclosure Number: IPCOM000109160D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Feig, E: AUTHOR [+3]

Abstract

A method for transform encoding of images is disclosed. The method allows for more efficient software decoding than standard run length techniques.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 96% of the total text.

A New Method for Transform Encoding of Images

      A method for transform encoding of images is disclosed.  The
method allows for more efficient software decoding than standard run
length techniques.

      Typically, an image is compressed with the following technique.
The image is first segmented into M times N blocks.  Each block is
then subjected to some kind of transform, e.g, the discrete cosine
transform.  The transform data is quantized.  The quantized transform
data is compressed with an entropy encoder, e.g., run-length encoding
followed by Huffman encoding.

      The invention is a variation on the final stage, the encoding
the quantized coefficients.  For each block, arrange the MN
coefficients into a one-dimensional array and then compute an integer
i as follows.  The bit of i that is k places from the right is
a 0 if coefficient k is 0, and it is a 1 otherwise.  The encoder
codes, in order, the integer i and then the nonzero coefficients.

      A corresponding decoder has linear code to deal with every
possible value that i can take on.  After i is decoded, the decoder
jumps to the appropriate code segment.  The code segment decodes the
nonzero coefficients and computes the inverse transform.  The code
segment can be optimized to avoid computations that are made
redundant by the fact that it is known ahead of time that certain of
the transform coefficients are zero.  Except for the initial branch
based on i, no conditional branchi...