1. An image compression device for generating compressed data formed by compressing an image, said image compression device comprising: a boundary area detection section for detecting boundary areas which include both of internal and external parts of an object rendered in the image, from among plural areas included in the image; a non-boundary area data generation section for, by compressing non-boundary areas which are not the boundary areas in the image, in a predetermined compression mode, generating partially compressed data in the compressed data, corresponding to the non-boundary areas; and a boundary area data generation section for generating partially compressed data in the compressed data, corresponding to the boundary areas, from the boundary areas, in a mode in which difference between images before compression and after expansion is less in comparison with a case where the boundary areas are compressed in the predetermined compression mode.