Method, apparatus and system for compressing data

Apparatus for compressing a digital image to obtain a compressed image data set for subsequent reconstruction, comprising:

• means to detect and convert digital image data from RGB color space to a less redundant color space;
• means to perform a wavelet decomposition of each color plane of said image in said less redundant color space to obtain a transform of DC and non-DC terms;
• means to losslessly encode said DC terms;
• means to convert said transform to a sign and magnitude format and to select a division point comprising one of a pair of adjacent bit planes and a pair of adjacent amplitudes which separate the non-DC terms into first and second ranges, based upon absolute magnitudes, the first range comprising values of the transform which are greater in magnitude than those in the second range of the transform;
• scalar quantizer means to encode the values in said first range;
• vector quantizer means to encode the values in said second range;
• and
• means to losslessly encode the resulting data set to obtain a compressed image data set.

A method of encoding wavelet transformed digital information composed of DC and non-DC terms, comprising the steps of:

• (i) establishing a hierarchy in said transformed digital information wherein each pixel in the highest level adjacent the DC terms is identified as the parent of a corresponding two by two array of child pixels in the next lower level and repeating said identification for each lower level;
• (ii) for the highest level to the lowest level of the hierarchy to be encoded, examining each trio of corresponding horizontal, vertical and diagonal pixels in the level in turn in a dominant pass to identify pixels not previously deemed significant and losslessly encoding the address and sign of said identified pixels in the present level and examining the two by two child array of pixel trios in each lower level down to the lowest level and identifying those newly significant pixels;
• (iii) identifying zero tree roots in said examined pixels and removing from said hierarchy pixels which are dependent from a zero tree root from said hierarchy;
• (iv) in a subordinate pass, outputting the magnitudes of all significant pixels identified in the dominant pass, in the same order as the dominant pass was performed, said output magnitudes having a preselected numeric precision;
• and
• (v) repeating steps (ii) through (iv) for each level until the lowest level has been processed.

An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for implementing a digital image compression apparatus, the computer readable program codes means in said article of manufacture comprising:

• computer readable program code for causing said computer to detect and convert digital image data from RGB color space to a less redundant color space;
• computer readable program code means for causing said computer to perform a wavelet decomposition of each color plane of said image in said less redundant color space to obtain a transform of DC and non-DC terms;
• computer readable program code means for causing said computer to losslessly encode said DC terms;
• computer readable program means for causing said computer to convert said transform to a sign and magnitude format and to select a division point comprising a pair of bit planes which separate the non-DC terms into first and second ranges, based upon absolute magnitudes, the first range comprising values of the transform which are greater in magnitude than those in the second range of the transform;
• computer readable program code means for causing said computer to perform a scalar quantization to encode the values in said first range;
• computer readable program code means for causing said computer to perform a vector quantization to encode the values in said second range;
• and
• computer readable program code means for causing said computer to losslessly encode the resulting data set to obtain a compressed image data set.