Image Retrieval Apparatus, Image Retrieval Method, and Recording Medium

An image retrieval method, comprising:

• acquiring a first image feature value for a retrieval target image;
• retrieving, from a plurality of image feature values, an image feature value that is similar to the first image feature value acquired in the acquiring;
• determining a linear conversion parameter to be used for linear conversion out of a group of linear conversion parameters that are based on a plurality of image feature values for a plurality of images of the same photographic subject obtained under a plurality of conditions, based on the first image feature value and image feature value for the photographic subject;
• converting the first image feature value using a linear conversion parameter determined in the determining, and converting, using the linear conversion parameter, the image feature value retrieved in the retrieving;
• and
• outputting the conversion result of the converting.

A non-transitory recording medium having stored therein, an image retrieval program, the non-transitory recording medium being readable by a processor,

• wherein the image retrieval program causes the processor to execute:
• an acquisition process of acquiring a first image feature value for a retrieval target image;
• a retrieval process of retrieving, from a plurality of image feature values, an image feature value that is similar to the first image feature value acquired in the acquiring;
• a determining process of determining a linear conversion parameter to be used for linear conversion out of a group of linear conversion parameters that are based on a plurality of image feature values for a plurality of images of the same photographic subject obtained under a plurality of conditions, based on the first image feature value and image feature values for the photographic subject;
• a conversion process of converting the first image feature value using a linear conversion parameter determined in the determining, and converting, using the linear conversion parameter, the image feature value retrieved in the retrieving;
• and
• an output process of outputting the conversion result of the conversion process.