Motoi Iwata

Bio: Motoi Iwata is an academic researcher from Osaka Prefecture University. The author has contributed to research in topics: Digital watermarking & Watermark. The author has an hindex of 9, co-authored 62 publications receiving 610 citations.

Speech balloon and speaker association for comics and manga understanding

Abstract: Comics and manga are one of the most important forms of publication and play a major role in spreading culture all over the world. In this paper we focus on balloons and their association to comic characters or more generally text and graphic links retrieval. This information is not directly encoded in the image, whether scanned or digital-born, it has to be understood according to other information present in the image. Such high level information allows new browsing experience and story understanding (e.g. dialog analysis, situation retrieval). We propose a speech balloon and comic character association method able to retrieve which character is emitting which speech balloon. The proposed method is based on geometric graph analysis and anchor point selection. This work has been evaluated over various comic book styles from the eBDtheque dataset and also a volume of the Kingdom manga series.

A Survey of Comics Research in Computer Science

Abstract: Graphic novels such as comic books and mangas are well known all over the world. The digital transition started to change the way people are reading comics: more and more on smartphones and tablets, and less and less on paper. In recent years, a wide variety of research about comics has been proposed and might change the way comics are created, distributed and read in the future. Early work focuses on low level document image analysis. Comic books are complex; they contains text, drawings, balloons, panels, onomatopoeia, etc. Different fields of computer science covered research about user interaction and content generation such as multimedia, artificial intelligence, human–computer interaction, etc. with different sets of values. We review the previous research about comics in computer science to state what has been done and give some insights about the main outlooks.

Digital watermarking method for tamper detection and recovery of JPEG images

Abstract: Digital watermarking is a technique that embeds additional data into digital contents so that the distortion by embedding them is imperceptible, where the additional data are called watermark. One of the applications of digital watermarking is tamper detection and recovery. The digital watermarking methods for tamper detection and recovery can detect the tampered region in a tampered image and recover it. In this application, the digital watermarking methods solve the problem that digital contents can be tampered so that the falsification is not detected. In this manuscript, we propose a new method for tamper detection and recovery of JPEG images by using a RS code. The proposed method embeds the check symbols corresponding to an information-reduced original image into the LSBs of the quantized DCT coefficients in a JPEG image directly. Therefore the method completely extracts the embedded data from watermarked JPEG images. We investigated the performance of the proposed method in view of the image quality and the ability of tamper detection and recovery. The experiments of the image quality confirmed the imperceptibility of watermarked images and images used for recovery. The experiments of the ability of tamper detection and recovery confirmed the maximum size of recoverable tampered region and the difficulty of undetectable falsification.

Sketch-based manga retrieval using manga109 dataset

Abstract: Manga (Japanese comics) are popular worldwide. However, current e-manga archives offer very limited search support, i.e., keyword-based search by title or author. To make the manga search experience more intuitive, efficient, and enjoyable, we propose a manga-specific image retrieval system. The proposed system consists of efficient margin labeling, edge orientation histogram feature description with screen tone removal, and approximate nearest-neighbor search using product quantization. For querying, the system provides a sketch-based interface. Based on the interface, two interactive reranking schemes are presented: relevance feedback and query retouch. For evaluation, we built a novel dataset of manga images, Manga109, which consists of 109 comic books of 21,142 pages drawn by professional manga artists. To the best of our knowledge, Manga109 is currently the biggest dataset of manga images available for research. Experimental results showed that the proposed framework is efficient and scalable (70 ms from 21,142 pages using a single computer with 204 MB RAM).

Sketch-based Manga Retrieval using Manga109 Dataset

Abstract: Manga (Japanese comics) are popular worldwide. However, current e-manga archives offer very limited search support, including keyword-based search by title or author, or tag-based categorization. To make the manga search experience more intuitive, efficient, and enjoyable, we propose a content-based manga retrieval system. First, we propose a manga-specific image-describing framework. It consists of efficient margin labeling, edge orientation histogram feature description, and approximate nearest-neighbor search using product quantization. Second, we propose a sketch-based interface as a natural way to interact with manga content. The interface provides sketch-based querying, relevance feedback, and query retouch. For evaluation, we built a novel dataset of manga images, Manga109, which consists of 109 comic books of 21,142 pages drawn by professional manga artists. To the best of our knowledge, Manga109 is currently the biggest dataset of manga images available for research. We conducted a comparative study, a localization evaluation, and a large-scale qualitative study. From the experiments, we verified that: (1) the retrieval accuracy of the proposed method is higher than those of previous methods; (2) the proposed method can localize an object instance with reasonable runtime and accuracy; and (3) sketch querying is useful for manga search.