Disclosed herein is an information processor including: an image storage section storing a piece of first image data having a first resolution and at least one piece of second image data as layer-by-layer image data for a specimen, the piece of second image data being obtained by spatially compressing the piece of first image data at different magnification ratios; an image data acquisition section acquiring image data from the layer-by-layer image data in units of a predetermined second resolution by which the first resolution is equally divisible to display the image data on a display device; an annotation setting section setting annotations at arbitrary spatial positions of the display image data in response to an instruction from the user; and an image optimization section determining whether each piece of the image data stored in the image storage section is necessary to delete the image data determined to be unnecessary.