| 摘要 |
PURPOSE: To facilitate decoding of additional information by controlling the quantization value of a target pixel so that the quantization value of a plurality of pixels, including the target pixel forms a specific pattern to multiplex the additional information onto image information. CONSTITUTION: A pseudo-gradation processing section 101 applies pseudo-gradation processing to received image information to convert its quantization level into a quantization level which is less than that represented by an input gradation number, and a quantization value of a plurality of pixels expresses gradation in terms of area. A quantization section 103 calculates the quantization value of a target pixel by referencing a code of additional information and also a quantization result of a plurality of pixels having already been quantized finally. A quantization value decision section 104 decides the final quantization value, on the basis of both quantization values after the quantization after the pseudo-gradation processing in the pseudo- gradation processing section 101 and after the quantization in the quantization section 103. Thus, use of the pseudo-gradation processing enables quantizing of the target pixel of image information to control the quantization value of the target pixel, so that the quantization value of a plurality of pixels including the target pixel forms a specific pattern indicating the additional information.
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