Patent ID: 6917711
Filing Date: 2005-07-12
Classification: H04N

Abstract:
1. A method for encoding a digital still image to produce a compressed bit stream, said method comprising the steps of: a) decomposing and ordering the digital still image into a hierarchy of multi-resolution images, wherein each multi-resolution image comprises a set of one or more transform coefficients, wherein each transform coefficient has a magnitude and wherein each transform coefficient represents a pixel of said digital still image; b) initializing a list of insignificant blocks, a temporary list of insignificant blocks and a list of significant pixels as empty sets, wherein after initialization and during processing the list of insignificant blocks is used to store one or more blocks of transform coefficients for which all transform coefficients are insignificant for a particular threshold value or have not yet been evaluated for significance, the temporary list of insignificant blocks is used to store one or more blocks of transform coefficients for which all transform coefficients have been evaluated to be insignificant for a particular threshold value and the list of significant pixels comprises one or more transform coefficients which have been evaluated to be significant for a particular threshold value; c) entering each multi-resolution image as a block of transform coefficients into the list of insignificant blocks in an arbitrary sequence; d) determining an initial threshold value based on the transform coefficient having the largest magnitude; e) generating a significance map related to a selected threshold value and encoding said significance map using a quadtree representation, wherein said significance map is determined by the evaluation of the significance of the blocks of transform coefficients within the list of insignificant blocks in relation to this selected threshold value, wherein the sequence of evaluation is performed according to the sequence in which the blocks of transform coefficients were entered into the list of insignificant blocks and wherein a transform coefficient greater than or equal to the selected threshold value is significant in relation to this selected threshold value; and f) generating the compressed bit stream, wherein said bit stream contains a bit stream header comprising information relating to method of generation of said compressed bit stream.