원근거리 판별 기반의 에지·컬러 히스토그램을 이용한 위성영상 워터마킹

Abstract

A geographic information system (GIS) is a system that captures, stores, analyzes, manages, and presents geographical information. Recently, the interest in GIS data has been highly increased along with the development of various services using GIS. The recent GIS technology has been developed to the newly content combined to various information and communication technologies, such as Web 2.0, SaaS(Software as a Service), Digital Convergence and Mash-up Service in the trend of consumerization of IT industry. But GIS should require the more strong security system because GIS data developed to contents provides the location information, which it will be considered to privacy information. An active discussion about security technologies of GIS vector data is in progress, but there is still a lack of security technologies for satellite images based on raster data. This paper therefore aims to suggest digital watermarking schemes to protect copyrights of satellite images. In this paper, we propose a watermarking scheme adaptive to the perspective distance of satellite image. Firstly, we classify any satellite image to short or long distances according to the hue histogram. Thus, a satellite image is classified to short-distance if the hue histogram is distributed widely on many levels, such as border zones of buildings, roads, cities, and so on. On the contrary, a satellite image is classified to long-distance if the hue histogram is distributed highly on particular levels, such as nature region like seas, mountains and rivers. In case of a short distance, we divide an image into blocks and detect the principal edge ingredient of each block by using the edge histogram. Then we insert the watermark in the principal edge by varying adjacent pixels. In case of a long distance, we obtain a histogram of color that is near to a particular hue level with high distribution and divide it into some levels considering the length of watermark. Then we insert the watermark by shifting the histogram in the divided levels. The experimental results verified that the watermarked satellite image has an excellent invisibility and also has the robustness to translation, scaling- up/down, rotation, cropping, and JPEG compression.