Patent ID: 6661924
Filing Date: 2003-12-09
Classification: H04N

Abstract:
A compression apparatus for compressing image data comprising:a reduced-image generating processor that transforms original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of said original image data; a fluency transform processor that applies a fluency transform to said reduced-image data so as to generate expanded-image data partitioned into second blocks corresponding to said first blocks, said fluency transform having a plurality of modes; a differential value calculating processor that obtains differential value data indicating a difference between said original image data and said expanded-image data; an orthogonal transform processor that obtains orthogonal transform coefficient data by applying an orthogonal transform to said differential value data; a mode setting processor that selects one mode from said plurality of modes, said orthogonal transform coefficient data being generated in accordance with said selected mode; a code-length calculating processor that calculates a code-length corresponding to a bit length of Entropy-encoded bit data obtained by an Entropy coding to said orthogonal transform coefficient data, said code-length calculating processor calculating said code-length in each of said plurality of modes; an optimum mode determining processor that determines an optimum mode, by which said code-length becomes minimum, from said plurality of modes; and an optimum Entropy coding processor that obtains said Entropy-encoded bit data by applying said Entropy coding to said orthogonal transform coefficient data in accordance with said optimum mode.