In this paper, we propose a block-based transformation algorithm to achieve the purpose of image content protection. More importantly, under the proposed image content protection framework, image retrieval and image convolution can also be performed directly on the content-protected images. As a consequence, not only secure image storage and communication are accomplished, but also the computation efforts can be fully distributed, thus making it a perfect match for nowadays popular cloud computing technology. Security analyses are conducted to prove that the proposed image encryption scheme offers certain degree of security in both statistical and computational aspects. Although a higher data confidentiality may be reached by adopting traditional cryptographic encryption algorithms, we believe it could be accepted by ordinary users with general image storage needs, since extra functionalities, i.e. content-based image retrieval and image convolution, are provided. Experimental results also demonstrate the decent performance of the proposed encryption domain image retrieval and convolution with acceptable storage overhead.