Abstract: A method for categorizing multiple users of a website based on their respective transition patterns between successive types of user activities is implemented at a computing device having one or more processors and memory. After receiving one or more log files from a data source, the computing device generates respective event transition matrixes for multiple users in accordance with the users' event records such that each element of each respective event transition matrix includes a probability of an occurrence of two consecutive event types A and B for the same user. Based on an analysis of the multiple users' event transition matrixes, the computing device categorizes the multiple users into at least two distinct groups of users and performs one or more operations to the website's user accounts associated with one or more users from one of the groups.

Abstract: Methods and systems for watermarking of digital images are presented. In one aspect, a method of embedding information in a digital image includes transforming the digital image to a set of coefficient blocks having coefficients in a frequency domain, embedding a watermark-indicator in one or more of the coefficient blocks, and embedding a watermark in one or more watermark blocks that have a predetermined number of coefficient blocks. The embedded watermark is substantially invisible in the output watermarked digital image. Another aspect is a method of extracting a watermark from a digital image that includes transforming a digital image to a coefficient matrix, determining if the digital image is watermarked based on a predetermined watermark-indicator, and retrieving a watermark from a projected watermark block of a projected watermark block distribution.

Abstract: Methods and systems for watermarking of digital images are presented. In one aspect, a method of embedding information in a digital image includes transforming the digital image to a set of coefficient blocks having coefficients in a frequency domain, embedding a watermark-indicator in one or more of the coefficient blocks, and embedding a watermark in one or more watermark blocks that have a predetermined number of coefficient blocks. The embedded watermark is substantially invisible in the output watermarked digital image. Another aspect is a method of extracting a watermark from a digital image that includes transforming a digital image to a coefficient matrix, determining if the digital image is watermarked based on a predetermined watermark-indicator, and retrieving a watermark from a projected watermark block of a projected watermark block distribution.

Abstract: Methods and systems for watermarking of digital images are presented. In one aspect, a method of embedding information in a digital image includes transforming the digital image to a set of coefficient blocks having coefficients in a frequency domain, embedding a watermark-indicator in one or more of the coefficient blocks, and embedding a watermark in one or more watermark blocks that have a predetermined number of coefficient blocks. The embedded watermark is substantially invisible in the output watermarked digital image. Another aspect is a method of extracting a watermark from a digital image that includes transforming a digital image to a coefficient matrix, determining if the digital image is watermarked based on a predetermined watermark-indicator, and retrieving a watermark from a projected watermark block of a projected watermark block distribution.

Abstract: Methods and systems for watermarking of digital images are presented. In one aspect, a method of embedding information in a digital image includes transforming the digital image to a set of coefficient blocks having coefficients in a frequency domain, embedding a watermark-indicator in one or more of the coefficient blocks, and embedding a watermark in one or more watermark blocks that have a predetermined number of coefficient blocks. The embedded watermark is substantially invisible in the output watermarked digital image. Another aspect is a method of extracting a watermark from a digital image that includes transforming a digital image to a coefficient matrix, determining if the digital image is watermarked based on a predetermined watermark-indicator, and retrieving a watermark from a projected watermark block of a projected watermark block distribution.