Managing an image storage space is provided. A number of processor units identifies a benchmark image in a similar images group. A number of other images not identified in the similar images group as the benchmark image is a set of similar images. The number of processor units creates an image mapping tree. The image mapping tree has a root block for the benchmark image and blocks arranged in a set of layers below the root block based on the set of similar images; the blocks represent portions of the benchmark image; and a plurality of lower blocks in the blocks in a lower layer correspond to subdivisions in an upper block in the blocks in an upper layer. The number of processor units stores a set of selected blocks in the set of similar images that have differences from a set of corresponding blocks in image mapping tree for the benchmark image. The number of processor units store metadata for the set of selected blocks that describes set of paths in the image mapping tree from the set of corresponding blocks in the image mapping tree to the root block.