Digital Watermarking Algorithms for Spatial Raster Data
Date Issued
2016
Date
2016
Author(s)
Chen, Chih-Cheng
Abstract
This study mainly focused on raster spatial data for digital watermarking analysis and discussion, the explored objects included photogrammetric images, remote sensing images and digital terrain model (DTM). The watermarking algorithm of images are mainly is developed based on image''s feature points for digital watermarking algorithm, and influences and robustness of images after watermark embedding were tested during the study. When conducting copyright protection using watermarking algorithm in the future, relevant results can be used as the reference when evaluating derivational problems from re-processing and geometric transformation of images with watermarks embedded. Moreover, the watermarking algorithm proposed in this study had little influence on the original quality of images after embedding, thus could avoid subsequent application outcomes of images. It was proved by the experimental results that in addition to a certain degree of robustness, the digital watermarking algorithm proposed in this study can also resist attacks from different types of image processing and geometric transformation, and at the same time maintain the quality of images. The second watermarking algorithm for image proposed in this study also based on feature points and adjusted the embedding strength of watermarks according to feature region''s texture sensitivity value, resulting in less anamorphose of images after watermark embedding and higher robustness when images were under geometric attacks such as rotation and resizing. Watermarking algorithm was tested for robustness using geometric corrections such as rotation scale translation (RST) and polynomial transformation targeting remote sensing images, the NC value of watermarks captured from geometrically corrected images through RST is very high. However, the extracted watermark after polynomial transformation is unidentifiable and has a small NC value.The third part of this study is DTM, which is an important national fundamental data. As confirmed through experiments, an aspect-based algorithm was proposed in this study so that the bits of watermark information could be evenly and repeatedly embedded into DTM data, through which not only the number of redundant embedding times could be increased and watermark embedding capacity could be improved, the problem of relatively low data redundancy can also be overcome, thus the data contents would have good robustness even if they were altered because of being attacked.
Subjects
digital watermarking
spatial data
robustness
surjective function
Type
thesis