Patent ID: 6553142
Filing Date: 2003-04-22
Classification: G06F,G06Q,G11B,H04N

Abstract:
A method for compressing image data, comprising:receiving the image data, transforming a block of the image data using a discrete cosine transform to obtain a matrix of coefficients, wherein each coefficient corresponds to a frequency in a range of frequencies having low frequencies and high frequencies; defining at least one quantization matrix, wherein the quantization matrix has a plurality of quantization values, wherein each quantization value corresponds to a coefficient in the matrix of coefficients, and wherein each quantization value corresponds to a frequency in the range of frequencies having low frequencies and high frequencies, wherein the quantization values are defined to obtain a desired amount of data from processing the matrix of coefficients, wherein the quantization values in different quantization matrices are such that for increased compression, a quantization value corresponding to at least one higher frequency is changed whereas quantization values corresponding to at least one lower frequency is unchanged; quantizing the coefficients for the block of the image data using the defined quantization matrix; and encoding the quantized coefficients to produce compressed image data.