| 摘要 |
PURPOSE:To appropriately recognize an irradiation field and to appropriately determine an image processing condition by expressing a change in the density of an image by means of plural linear approximate formulas and calculating a difference between proposed image density values based upon these approximate formulas. CONSTITUTION:A change in the density of an image indicated by a sample image signal is expressed by approximate formulas F1-Fn practically consisting of linear equations successively in picture element groups L1-Ln arranged from the end part of recording area 103A of a recording medium 103 to the center side, the difference DELTAD between the proposed image density values based upon the approximate formulas Fi and Fi-1 is calculated and an area in which the difference is reached from the end part to the center side and an inside area are respectively recognized as the outside of the radiation field 103B and the radiation field 103A. Thereby, an image signal extracted from the inside of the radiation field 103A is a signal excluding an image signal due to dispersed line on the outside of the radiation field. Consequently, the image processing condition can be determined based on a real image signal including no dispersed line noise.
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