IMAGE ENCODING/DECODING EQUIPMENT, IMAGE ENCODING/ DECODING METHOD AND ITS STORAGE MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide image encoding/decoding equipment, an image encoding/ decoding method and its storage medium which can prevent deterioration of image quality and decrease of compression ratio. SOLUTION: The image encoding/decoding equipment is provided with a control unit 101 for inputting halftone image data via an input part 102, a compression method selecting part 104 for selecting a compression method, a contraction part 105 for contracting the halftone image data and producing contracted image data, gradation converting parts 106, 107 for converting the halftone image data or the contracted image data to multivalued image data on the basis of a selected contraction method, and compression parts 108, 109 for compressing the multivalued image data and producing compressed image data. The compression method selecting part 104 selects the compression method by using color plane information of the halftone image data.