Patent ID: 6396955
Filing Date: 2002-05-28
Classification: G06T

Abstract:
An image compression device comprising:an orthogonal transformation processor that applies an orthogonal transformation to image data corresponding to a still image to obtain orthogonal transformation coefficients; a determiner that determines whether a sign of each of said orthogonal transformation coefficients expressed as a bit sequence is negative; a calculator that manipulates said bit sequence to reverse said sign, when said sign is negative; a bit separation processor that separates one of said bit sequence when said sign of said orthogonal transformation coefficient is positive and a manipulated bit sequence when said sign of said orthogonal transformation coefficient is negative to a higher-rank bit sequence and a lower-rank bit sequence to obtain a higher-rank orthogonal transformation coefficient and a lower-rank orthogonal transformation coefficient; a sign bit addition processor that adds one of an additional positive-sign bit to said lower-rank bit sequence when said orthogonal transformation coefficient is positive and an additional negative-sign bit to said lower-rank bit sequence when said orthogonal transformation coefficient is negative to obtain a sign-included lower-rank orthogonal transformation coefficient; a grouping processor that utilizes a group table to obtain zero run lengths, group numbers and added bits of said higher-rank orthogonal transformation coefficients; and an encoding processor that utilizes a Huffman table to determine a codeword corresponding to each of said zero run lengths and said group numbers, and combines said added bits and said codeword to generate compressed image data.