Patent ID: 6904181

Claim:
An image data processing apparatus comprising: radiation generation means for generating X-rays; two-dimensional X-ray sensor means for obtaining, as image data, the X-rays penetrating an object; object area extraction means for extracting an area of the object from an image represented by the image data obtained by said two-dimensional X-ray sensor means; limitation means for limiting the object area extracted by said object area extraction means; extraction means for extracting a feature quantity in the area limited by said limitation means; and gradation conversion means for determining a shape of a gradation conversion curve using, as a parameter, the feature quantity extracted by said extraction means, and performing gradation conversion of the image data using the gradation conversion curve whose shape has been determined, wherein said limitation means comparts the extracted object area in a certain ratio of the vertical axis of the extracted object area or a certain length in the vertical direction of the image and limits the object area by using a comparted range as a reference.