Reduce the information for recording block indexes by non-uniform clustering algorithm and thus improve the quality of camouflage image by setting small block size.

Modify the previous color transformation to be reversible. So the secret image can be transformed to a freely-selected target image, getting a camouflage image used as the camouflage of secret image with good visual quality, and the secret image can be restored without any loss.

Because of the reversibility, we can further realize multi-round transformation, that is, transform the camouflage image to another target image.