Patent ID: 6420979
Filing Date: 2002-07-16
Classification: G06F,G06T

Abstract:
A method for compressing image signals comprising:a selection process of selecting 2N pieces of picture element data fj (0&lE;j&lE;2Nâˆ’1) contained in one line or one string constituting a block of 2NÃ—2N (N being a natural number) pieces of picture element data forming image data, for each of fixed coefficients Pk given in equation (1) and equation (2) and determined in accordance with a discrete cosine transformation rule; a multiplication process of multiplying each piece of selected said picture element data by each of corresponding said fixed coefficients Pk to obtain products; an addition/subtraction process of performing adding operations and/or subtracting operations between products obtained by said multiplication process and determined in accordance with said discrete cosine transformation rule; and an output process of outputting a value obtained by said addition/subtraction process as transformation coefficient data Fj for each line or each string constituting said block of 2NÃ—2N picture element data; wherein, in said selection process, first set and second set of picture element data composed of 2N pieces of picture element data contained in one line or one string constituting said block of 2NÃ—2N pieces of picture element data are selected for each of fixed coefficients, out of said fixed coefficients Pk, with k in odd-numbered positions in said equation (1) and said equation (2), in a predetermined order, and wherein, in said multiplication process, said first set and said second set of picture element data selected for each of said fixed coefficients with k in odd-numbered positions in said equation (1) and said equation (2) are multiplied by each of said fixed coefficients with k in odd-numbered positions in said equation (1) and said equation (2) to obtain said product; Pk=cos&it;â€ƒ&it;((N-1-k)&it;Ï€2N+1)(1)â€ƒ0&lE;k&lE;2Nâˆ’1âˆ’2 where k=2Nâˆ’1âˆ’1 is excluded; Pk=12(2)(k=2Nâˆ’1âˆ’1).