Overcompression is the process of post-processing compressed images to gain either further size reduction or improved quality. This is made possible by the fact that the set of all \reasonable" images has a sparse structure. In this work, we apply this idea to the overcompression of JPEG images: We reduce the blocking artifacts commonly seen in JPEG images by allowing the low frequency coecients of the DCT to vary slightly. Evolutionary strategies are used in order to guide the modication of the coecients towards a smoother image.