| 摘要 |
An unsharp mask signal Lu, which corresponds to super-low frequency, is calculated from an original image signal Dorg representing an original image. The rate of compression, at which the dynamic range of the original image is compressed, is changed in accordance with the unsharp mask signal Lu. A dynamic range compressing process is carried out with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements. The dynamic range compressing process is carried out with Formula (1)Dproc=Dorg+f(Lu)(1)and a processed image signal Dproc is thereby obtained. The unsharp mask signal Lu represents the mean value of the image signal values of all picture elements located within a rectangular unsharp mask having shorter sides, which extend across an edge of a region of interest in the original image, and longer sides extending in the direction along which the edge extends.
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