| 摘要 |
PROBLEM TO BE SOLVED: To enhance image compression rate of sub-band/wavelet transformation reversible compression. SOLUTION: A hierarchical processing means 100 receives an image signal and divides it into two specified areas depending on the frequency components thereof. A special conversion type context model encoding means 200 receives image signal in one divided area according to context modeling and performs encoding. A conversion predictive difference processing means 210 calculates an initial predictive value by applying a special reversible S conversion. A context subjected to special reversible S conversion is quantized. A predictive error calculating means 220 performs predictive correction of an initial predictive value depending on a quantized context, then calculates the difference between a predictive value and a predictive object pixel, and encodes the difference. An entropy encoding means 230 performs entropy encoding of an encoded image signal to generate an image compression signal. The context is reflected on the entropy encoding as required. |
