Patent ID: 6118903
Filing Date: 2000-09-12
Classification: H04N

Abstract:
A method of compressing a digitised image composed of a matrix of image samples to provide a compressed image which satisfies a predefined bit budget, the method comprising the steps of:1) dividing the digitised image into blocks and deriving for each block an energy packing transform comprising a set of transform coefficients;2) selecting a quantisation table from a set of quantisation tables and using the selected table to quantise the coefficients of each transform;3) deriving a zero-value index indicative of the number of zero-value quantised transform coefficients;4) determining a predicted zero-value index using said predefined bit budget;5) selecting a quantisation table from said set of tables using the derived index and said predicted index and using that selected table to quantise the coefficients of each transform; and6) compressing the coefficients quantised in step 5) using run-length encoding.