It is urgently required to protect copyrights from unjust usage since digital content can be easily copied without degradation of quality. There is a technique called watermarking to protect copyright of digital content, which hides secret information (digital watermark) in digital content. In this paper, we propose a new watermarking method which spreads an ID pattern (copyright information) with specific sequences and embeds it throughout the spatial domain of an image. The proposed method is robust to disturbance by noise addition and common image processing operations such as edge enhancement, contrast conversion, histogram equalization, posterization, Gaussian filtering, median filtering, and JPEG compression. As an ID pattern is spread throughout an image, we can extract the ID pattern from a part of the image, that is a clipped image. In the proposed method, we make a set of key sequences which are orthogonal to any part of fixed length of each column of the image and add the ID pattern to the image with the set of key sequences. We can extract the ID pattern by summing up the values of inner products of any part of fixed length of columns of the watermarked image and the corresponding part of key sequences even if the embedded values are altered by several image processing operations.