text: 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).
  @cite_36: Document analysis is an active field of research, which can attain a complete understanding of the semantics of a given document. One example of the document understanding process is enabling a computer to identify the key elements of a comic book story and arrange them according to a predefined domain knowledge. In this study, we propose a knowledge-driven system that can interact with bottom-up and top-down information to progressively understand the content of a document. We model the comic book's and the image processing domains knowledge for information consistency analysis. In addition, different image processing methods are improved or developed to extract panels, balloons, tails, texts, comic characters and their semantic relations in an unsupervised way.
  @cite_42: 
  @cite_43: 
  @cite_5: The existing content aware image retargeting methods are mainly suitable for natural images, and do not perform well on line drawings. Such methods tend to regard homogeneous areas as less important. For line drawings, this is not always true.
  @cite_66: We introduce a method for automated conversion of scanned color comic books and graphical novels into a new high-fidelity rescalable digital representation. Since crisp black line artwork and lettering are the most important structural and stylistic elements in this important genre of color illustrations, our digitization process is geared towards faithful reconstruction of these elements. This is a challenging task, because commercial presses perform halftoning (screening) to approximate continuous tones and colors with overlapping grids of dots. Although a large number of inverse haftoning (descreening) methods exist, they typically blur the intricate black artwork. Our approach is specifically designed to descreen color comics, which typically reproduce color using screened CMY inks, but print the black artwork using non-screened solid black ink. After separating the scanned image into three screening grids, one for each of the CMY process inks, we use non-linear optimization to fit a parametric model describing each grid, and simultaneously recover the non-screened black ink layer, which is then vectorized. The result of this process is a high quality, compact, and rescalable digital representation of the original artwork.
  @cite_18: Picture subjects and text balloons are basic elements in comics, working together to propel the story forward. Japanese comics artists often leverage a carefully designed composition of subjects and balloons (generally referred to as panel elements) to provide a continuous and fluid reading experience. However, such a composition is hard to produce for people without the required experience and knowledge. In this paper, we propose an approach for novices to synthesize a composition of panel elements that can effectively guide the reader's attention to convey the story. Our primary contribution is a probabilistic graphical model that describes the relationships among the artist's guiding path, the panel elements, and the viewer attention, which can be effectively learned from a small set of existing manga pages. We show that the proposed approach can measurably improve the readability, visual appeal, and communication of the story of the resulting pages, as compared to an existing method. We also demonstrate that the proposed approach enables novice users to create higher-quality compositions with less time, compared with commercially available programs.
  @cite_60: 
  @cite_48: 
  @cite_80: Today, the demand of services for comic contents increases because paper magazines and books are bulky while digital contents can be read anytime and anywhere with cellular phones and PDAs. To convert existing print comic materials into digital format such that they can be read using the cellular phones and the PDAs with small screens, it is necessary to divide each page into scene frames and to determine reading order of the scene frames. The division of comic images into the scene frames can be considered as a type of document layout analysis. We analyzed layout of comic images using density gradient. The method can be applied to comics in which comic balloons or pictures are drawn over scene frames. In this research, a method for detecting the scene frame division in comic images using the density gradient after filling the quadrangle regions in each image with black is proposed. Experimental results show that 80 percent of 672 pages in four print comic booklets are successfully divided into scene frames by the proposed method.
  @cite_26: Diversity of drawing styles of mangas can be easily perceived by humans, but are hard to be described in text. We design computational features derived from line segments to describe drawing styles, enabling style classification such as discriminating mangas targeting youth boys and youth girls, and discriminating artworks produced by different artists. With statistical analysis, we found that drawing styles can be effectively characterized by the proposed features such that explicit (e.g., density of line segments) or implicit (e.g., included angles between lines) observations can be made to facilitate various manga style classification.
  @cite_28: Comic books constitute an important cultural heritage asset in many countries. Digitization combined with subsequent comic book understanding would enable a variety of new applications, including content-based retrieval and content retargeting. Document understanding in this domain is challenging as comics are semi-structured documents, combining semantically important graphical and textual parts. Few studies have been done in this direction. In this work we detail a novel approach for closed and non-closed speech balloon localization in scanned comic book pages, an essential step towards a fully automatic comic book understanding. The approach is compared with existing methods for closed balloon localization found in the literature and results are presented.
  @cite_57: This research proposes a novel method to present "thumbnails" of episodes of digitized comics, in order to improve the efficiency of comic search. Comic episode thumbnails are generated based on image analysis technologies developed especially for comic images. Namely, the following procedures are developed for our system: automatic comic frame segmentation, text balloon extraction, and a linear regression based model to calculate the importance score of each extracted frame. The system then selects frames from each episode with high importance score, and aligns the selected frames to create the episode thumbnail, which is presented to the system user as a compact preview of the episode. User experiments conducted with actual Japanese comic images prove that the proposed method significantly decreases the time necessary to search for specific episodes from a large scaled comic data collection.
  @cite_34: 
  @cite_25: Screentones are unique expressions of Japanese comics (manga), which enrich their visual expression. However, such screentones have a very different visual nature from that of line drawing areas; this prevents us from applying various kinds of image processing techniques to manga. We propose a method for extracting line drawings and removing screentones. We employ Laplacians of Gaussian filters and flow-based differences of Gaussian filters, one for removing screentones and the other for preserving lines, and make a binary mask for separating line drawings from manga by merging the results of the two filters. We show that the proposed method successfully separates line drawings and is better than existing methods in comparative studies.
  @cite_61: We present eBDtheque, a database of various comic book images and their ground truth for panels, balloons and text lines plus semantic annotations. The database consists of a hundred pages of various comic book albums, Franco-Belgian, American comics and mangas. Additionally, we present the piece of software used to establish the ground truth and a tool to validate results against this ground truth. Everything is publicly available for scientific use on http: ebdtheque.univ-lr.fr.
  @cite_14: This paper describes an efficient system for scalable video summarization that exploits comic-like summaries and multi-scale representations to facilitate interactivity and balance between content coverage and compactness. Due to the layout disturbance induced by the transitions between scales, a new heuristic algorithm is proposed to restrict changes to bounded summary segments. Conducted user evaluations show that the proposed methodology improves usability while keeping the summaries compact and informative.
  @cite_53: 
  @cite_45: Manga (Japanese comics) are popular all over the world. However, most existing manga are monochrome. If such monochrome manga can be colorized, readers can enjoy the richer representations. In this paper, we propose a semiautomatic colorization method for manga. Given a previously colored reference manga image and target monochrome manga images, we propagate the colors of the reference manga to the target manga by representing images as graphs and matching graphs. The proposed method enables coloring of manga images without time-consuming manual colorization. We show results in which the colors of characters were correctly transferred to target characters, even those with complex structures.
  @cite_59: 
summary: From an image-processing perspective, manga has a distinctive visual nature compared with natural images. Several applications for manga images have been proposed: colorization @cite_45 @cite_43 @cite_48 , vectorization @cite_66 , layout recognition @cite_80 , layout generation @cite_57 @cite_34 , element composition @cite_18 , manga-like rendering @cite_59 , speech balloon detection @cite_28 , segmentation @cite_53 , face tailored features @cite_26 , screen tone separation @cite_25 , retargeting @cite_5 , and manga-like summarization for video @cite_14 @cite_42 @cite_60 . The research group at Universit 'e de La Rochelle constructed a comic database @cite_61 , which we mention in sec:db , and analyzed the structure of visual elements in a page to understand the comics content semantically @cite_36 .