A PSO Based Image Disguise Method

When the tampered JPEG image is saved, it was re-compressed. After double compression, the amounts of some DCT coefficient values decrease greatly. The pattern can be easily detected by statistics methods. To defend this forensic method, we established a model to evaluate the security and image quality influenced by the re-compression. Base on the model, an optimized adjustment of the DCT coefficients is achieved by PSO (Particle Swarm Optimization). Results show that the traces of double compression are removed but well preserving the image quality.