1. An image processing apparatus, comprising: a reducing section reducing an image for which a feature analysis is to be carried out at a predetermined reduction ratio; an ROI mask generating section analyzing a feature of a reduced image as the image reduced at the predetermined reduction ratio by said reducing section, and generating an ROI mask as mask information indicating a region of interest as a region to be interested in the reduced image; an ROI mask enlarging section enlarging a size of said ROI mask generated by said ROI mask generating section to a size of the image before being reduced at the predetermined reduction ratio by said reducing section; and an ROI mask updating section analyzing a feature of a region, set as a blank region as a region not to he interested in said ROI mask, of the image before being reduced at the predetermined reduction ratio by said reducing section, and updating said ROI mask by using an analysis result; ROI standing for region of interest.