A Study On Compression, Encryption And Retrieval Of Image And Their Arithmetics

Currently, valid compression and efficient transfers of images are needed in communication, navigation and teaching etc; people require valid encryption method in order to prohibit infringing in the process of delivering and sharing of images; an efficiently retrieval method is urgently demanded when looking for a certain image in extensive image's database. In this paper, image is compressed efficiently based on the wavelet packets decomposition. It is concluded that energy and variance can be serve as the criterions which can be used to judge the importance of the coefficients through strictly deduction based on the character of the wavelet coefficients, these coefficients can be classed according to the criterion, after that they should be quantified adaptively; further more, different methods of quantization can use the same code table. In this paper, two methods are used to encrypt images. One method is designing watermark algorithm according to the principle of the DCT transformation and JPEG standard, taking good use of the sense of visual feature of person and the characteristic of image. The examinations of watermark only need a very small part of data from the original image according to the principle of our algorithm. It is easy to examine the watermark's existence when the image which contain watermark suffering from the compression of different degree, shearing to slice, and so on. Another method is based on the study of the ability of data conceals adequately, and proposed that the ability of data conceals can be scaled by using the degree of edge, the even degree of distribute and luminance. Using the idea of frequency modulation that belongs to communication engineering, and bringing up "frequency modulation watermark"which different to traditional watermark technique. Constituting base band signal by select the intermediate frequency coefficients of image piece which has strong data conceals ability, then, embedding and picking up watermark according to the idea of frequency modulation. This kind of watermark technique can give attention to invisibleness and robustness, and realize blind examination efficiently. A high-level retrieval method prompted in this paper is the retrieval of human based on the comprehension of pose. Comprehend the pose of human, descript the human by vector and realize the retrieval that tally with comprehension of human through the method of vector mapping warehouse.