Summary: Distortion-free compressibility of individual pictures by finite-state encoders is investigated. In a recent paper [\textit{A. Lempel} and \textit{J. Ziv}, IEEE Trans. Inf. Theory, IT-32, 1-8 (1986)], the compressibility of a given picture I was defined and shown to be the asymptotically attainable lower bound on the compression ratio that can be achieved for I by any finite-state encoder. In this paper, a different and more direct approach is taken to prove similar results, which are summarized in a converse-to-coding theorem and a constructive-coding-theorem that leads to a universal and asymptotically optimal compression algorithm.