DETERMINING IF AN IMAGE IS BLURRED

A technology for making determinations as to whether the image of an image data file is blurred, with low processing load, is provided. First, photographic image data PID containing pixel color information, as well as thumbnail image data for the photographic image data, are prepared. A specific pixel is then selected from among the pixels of the thumbnail image data. Specifically, on the basis of data of a pixel under examination and data of a pixel neighboring the pixel under examination, it is determined whether the pixel under examination should be designated as the specific pixel. Then, for a specific region Ape which is a region constituting part of the photographic image data PID and which corresponds to the specific pixel of the thumbnail image data, analysis of the photographic image PID is carried out, and a localized blur level that represents indistinctness of the image in the specific region Ape is calculated. Subsequently, in the event that the localized blur level of the specific region Ape contained in the photographic image data PID meets a prescribed condition, it is determined that the image of the photographic image data PID is blurred.