Patent ID: 8150186

Claim:
A method for compressing image data, comprising: quantizing image data corresponding to at least one digital image, the quantizing comprising: dividing the image data into a plurality of data blocks, the data blocks comprising corresponding numbers of pixels; applying orthogonal transformations to the data blocks, the orthogonal transformations generating corresponding conversion coefficients for the pixels of the data blocks; computing scaled threshold values associated with a quantization matrix, based on at least one scale factor and a corresponding scaling interval; and calculating quotients of the conversion coefficients and corresponding ones of the scaled threshold values to generate quantized image data; and compressing the quantized data in accordance with a variable-length encoding scheme, wherein: the at least one scale factor and the scaling interval enable the compressed data to fit within a predetermined range of a target amount of data; and the computing comprises: partitioning the scaling interval into a plurality of sub-intervals; calculating estimated values of the at least one scale factor for the sub-intervals, based on a relationship between the at least one scale factor and an amount of the compressed data; and computing the scaled threshold values, based on at least the estimated scale factor values.