With the development of information technology and network, multimedia protection has become a major concern, in which images are the important research objects. Especially, the image degradation is one of basic fields. This paper introduces a three-dimensional Z-matrix map which can be used for encryption, and shows its satisfactory property. Then, two color image degradation algorithms based on different templates for selective encryption are proposed. Finally, the performance and security of them are analyzed. Simulation results indicate the reliability of these schemes.