| In recent years, with the popularization of network communication technology, as an important tool for people to gain and exchange information, digital media like image etc. are extensively applied in various fields of the modern society. Because of relatively simple exchange and transmission process, digital image is extensively communicated and used on the Internet in the form of image information. Due to the explosive increase and communication of image information on the Internet and because of the transparency and operability of network information, more and more digital images are illegally stolen, tampered, copied and attacked, which seriously threatens legitimate interests of the copyright owners. Therefore, digital right management and copyright identification become increasingly important.As a branch of information hiding technology, digital watermark technology is one of the vital means to solve copyright issues. It utilizes randomness and redundant data universally existing in digital works to embed digital watermark indicating copyright information into digital media. The watermark not only will not affect the normal use of digital media but also will not be perceived by mankind’s visual system, which successfully protects the user’s copyright.Based on the mutually restricted relationship among information capacity contained by digital watermark, invisibility and robustness of the watermark, the paper analyzes and studies the influence of the transformation of IWT and digital DCT on image pixel. Besides, combining the features and color component correlation of colored images, the paper expands and applies the traditional gray level image watermark method in the field of colored images and puts forward a IWT-integer DCT domain QR code digital watermark algorithm based on the DS-FOA algorithm. With QR code containing copyright information as the digital watermark, QR code digital watermarks are periodically embedded to strengthen the capacity of true watermark information and the corrective function of QR code is used to improve robustness of the watermark so as to solve the contradiction between the capacity and robustness of digital watermark; DS-FOA (the Diminishing Step Fruit Fly Optimization Algorithm) is utilized to apply 53 IWT and integer DCT in the digital watermark technology, embed watermark in blue component to which HVS is insensitive, solve the contradiction between the invisibility and robustness of watermark; the paper tampers and attacks images with watermarks generated by the algorithm, makes a statistical recognition of pixel values in the same position of several QR code watermarks extracted according to the threshold value, revises the watermark by regarding pixel value greater than the threshold value as the pixel value of this point, improves the accuracy of QR code and guarantees that copyright information can be correctly identified; during the process of embedding and extracting digital watermark, based on sizes of the images carrying secrets and the embedded QR code, DS-FOA is used to self-adapt select the watermark embedding strength and position during the watermark embedding process and the threshold value in the watermark correction process; in the end, a simulation experiment is conducted to analyze the performance of the algorithm. |
