Vehicle detection method for expressway by MPEG compressed domain

A method which extracts traffic information from an MPEG-2 compressed video is proposed. According to the features of vehicle motion, the motion vector of a macro-block is used to detect moving vehicles in daytime, and a filter algorithm for removing noises of motion vectors is given. As the brightness of the headlights is higher than that of the background in night images, discrete cosine transform （DCT）coefficient of image block is used to detect headlights of vehicles at night, and an algorithm for calculating the DCT coefficients of P-frames is introduced. In order to prevent moving objects outside the expressway and video shot changes from disturbing the detection, a driveway location method and a video-shot-change detection algorithm are suggested. The detection rate is 97.4% in daytime and 95.4% in nighttime by this method. The results prove that this vehicle detection method is effective.

OPPR:An Outsourcing Privacy-Preserving JPEG Image Retrieval Scheme with Local Histograms in Cloud Environment

As the wide application of imaging technology,the number of big image data which may containing private information is growing fast.Due to insufficient computing power and storage space for local server device,many people hand over these images to cloud servers for management.But actually,it is unsafe to store the images to the cloud,so encryption becomes a necessary step before uploading to reduce the risk of privacy leakage.However,it is not conducive to the efficient application of image,especially in the Content-Based Image Retrieval(CBIR)scheme.This paper proposes an outsourcing privacy-preserving JPEG CBIR scheme.We design a set of JPEG format-compatible encryption method,making no file expansion to JPEG files.We firstly combine multiple adjacent 8×8 DCT coefficient blocks into big-blocks.Then,random scrambling and stream encryption are used on the binary code of DCT coefficients to protect the JPEG image privacy.The task of extracting features from encrypted images and retrieving similar images are done by the cloud server.The group index histograms of DCT coefficients are extracted from the encrypted big-blocks,then the global vector is produced to represent the JPEG image with the aid of bag-of-words(BOW)model.The security analysis and experimental results show that our proposed scheme has strong security and good retrieval performance.

ADAPTIVE RECONSTRUCTION TECHNIQUE FOR THE LOST INFORMATION OF THE RECTANGULAR IMAGE AREA

The adaptive reconstruction for the lost information of the rectangular image area is very important for the robust transmission and restoration of the image. In this paper, a new reconstruction method based on the Discrete Cosine Transform (DCT) domain has been put forward. According to the low pass character of the human visual system and the energy distribution of the DCT coefficients on the rectangular boundary, the DCT coefficients of the rectangular image area are adaptively selected and recovered. After the Inverse Discrete Cosine Transform (IDCT), the lost information of the rectangular image area can be reconstructed. The experiments have demonstrated that the subjective and objective qualities of the reconstructed images are enhanced greatly than before.