How to protect the secret digital images is an important issue in commercial or military application. In this paper, we propose a new scheme for secure still visual data with a block cipher structure, which is composed of three parts: encryption, decryption and key generator. The encryption process based on cryptographic primitive operations and Boolean functions is proposed. A key generator based on one-way coupled map lattice (OCML) is derived. Experimental results have demonstrated that the proposed cipher has satisfactory security with a low cost, which makes it a potential candidate for encryption of multimedia data such as images, audios and even videos.