Patent ID: 7024044
Filing Date: 2006-04-04
Classification: H04N

Abstract:
1. A method for compressing a digital image comprising a matrix of elements, each element comprising a plurality of digital components of different types for representing a pixel, the method comprising: determining at least one energy measure of the digital image; estimating a gain factor as a function of the at least one energy measure, the function being determined experimentally according to a target compression factor; splitting the digital image into a plurality of blocks, and calculating for each block a group of discrete cosine transform (DCT) coefficients for the digital components of different types, each group of DCT coefficients comprising at least one direct current (DC) coefficient and a plurality of alternating current (AC) coefficients; and quantizing the DCT coefficients for each block using a corresponding quantization table scaled by the gain factor for achieving the target compression factor; wherein determining the at least one energy measure comprising receiving the plurality of digital components, and calculating the at least one energy measure in a pixel domain using the plurality of digital components; wherein estimating the gain factor comprises