| 摘要 |
PROBLEM TO BE SOLVED: To make an arithmetic circuit small in scale and high in arithmetic speed by calculating normal distribution from the mean value and distribution of the concentration value of histogram. SOLUTION: A histogram calculating circuit 8 calculates a histogram for the concentration value of the constant area of an input picture, and calculates the mean value and distribution of the concentration value of the histogram. A normal distribution calculating circuit 9 calculates a normal distribution function from the mean value and distribution calculated by the histogram calculating circuit 8. A dividing circuit 10 calculates cumulative distribution function from the normal distribution function calculated by the normal distribution calculating circuit 9, divides the cumulative distribution axis of the cumulative distribution function into equal division, and calculates the re-quantization threshold value of a non-linear quantization. A reference table preparing circuit 11 prepares the reference table of the re-quantization threshold value calculated by the dividing circuit 10 and an actual picture concentration value. An original data concentration converting circuit 12 calculates a picture concentration value after re-quantization from the reference table and the concentration value of the input picture. |
