Christian X. Ries

Bio: Christian X. Ries is an academic researcher from Augsburg College. The author has contributed to research in topics: Feature (computer vision) & Visual Word. The author has an hindex of 7, co-authored 13 publications receiving 162 citations. Previous affiliations of Christian X. Ries include University of Augsburg.

A survey on visual adult image recognition

Abstract: We provide an overview of state-of-the-art approaches to visual adult image recognition which is a special case of one-class image classification. We present a representative selection of methods which we coarsely divide into three main groups. First we discuss color-based approaches which rely on the intuitive assumption that adult images usually feature skin-colored regions. Different ways of defining skin colors are described and example classification frameworks built on skin color models are presented. Another main group of approaches to adult image recognition is based on shape information which usually also exploit color information to find skin-colored regions of interest. Color and texture features are often used to augment such shape features. Finally we introduce approaches based on local feature descriptors.

Learning to Reassemble Shredded Documents

Abstract: In this paper, we address the problem of automatically assembling shredded documents. We propose a two-step algorithmic framework. First, we digitize each fragment of a given document and extract shape- and content-based local features. Based on these multimodal features, we identify pairs of corresponding points on all pairs of fragments using an SVM classifier. Each pair is considered a point of attachment for aligning the respective fragments. In order to restore the layout of the document, we create a document graph in which nodes represent fragments and edges correspond to alignments. We assign weights to the edges by evaluating the alignments using a set of inter-fragment constraints which take into account shape- and content-based information. Finally, we use an iterative algorithm that chooses the edge having the highest weight during each iteration. However, since selecting edges corresponds to combining groups of fragments and thus provides new evidence, we reevaluate the edge weights after each iteration. We quantitatively evaluate the effectiveness of our approach by conducting experiments on a novel dataset. It comprises a total of 120 pages taken from two magazines which have been shredded and annotated manually. We thus provide the means for a quantitative evaluation of assembly algorithms which, to the best of our knowledge, has not been done before.

Method for binary classification of a query image

Abstract: The invention relates to a method for the training of a classifier based on weakly labeled images and for the binary classification of an image. The training of the classifier comprises the steps of automatically and iteratively determining initial regions of interest for a training set and further on refining said regions of interest and adapting the classifier onto the refined regions of interest by a classifier refinement procedure. Further on, for a query image with unknown classification, an initial region of interest is determined and refined as to maximize the probability value derived at the output of said classifier. The query image is automatically assigned a negative classification label if said probability value is lower than or equal to a predetermined first threshold. The query image is automatically assigned a positive classification label if said probability value is greater than a predetermined second threshold.

Robust feature bundling

Abstract: In this work we present a feature bundling technique that aggregates individual local features with features from their spatial neighborhood into bundles. The resulting bundles carry more information of the underlying image content than single visual words. As in practice an exact search for such bundles is infeasible, we employ a robust approximate similarity search with min-hashing in order to retrieve images containing similar bundles. We demonstrate the benefits of these bundles for small object retrieval, i.e. logo recognition, and generic image retrieval. Multiple bundling strategies are explored and thoroughly evaluated on three different datasets.

Towards universal visual vocabularies

Abstract: Many content-based image mining systems extract local features from images to obtain an image description based on discrete feature occurrences. Such applications require a visual vocabulary also known as visual codebook or visual dictionary to discretize the extracted high-dimensional features to visual words in an efficient yet accurate way. Once such an application operates on images of a very specific domain the question arises if a vocabulary built from those domain-specific images needs to be used or if a ”universal” visual vocabulary can be used instead. A universal visual vocabulary may be computed from images of a different domain once and then be re-used for various applications and other domains. We therefore evaluate several visual vocabularies from different image domains by determining their performance at pLSA-based image classification on several datasets. We empirically conclude that vocabularies suit our classification tasks equally well disregarding the image domain they were derived from.

Advances In Kernel Methods Support Vector Learning

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Bundle min-hashing for logo recognition

Abstract: We present a scalable logo recognition technique based on feature bundling. Individual local features are aggregated with features from their spatial neighborhood into bundles. These bundles carry more information about the image content than single visual words. The recognition of logos in novel images is then performed by querying a database of reference images.We further propose a novel WGC-constrained RANSAC and a technique that boosts recall for object retrieval by synthesizing images from original query or reference images. We demonstrate the benefits of these techniques for both small object retrieval and logo recognition. Our logo recognition system clearly outperforms the current state-of-the-art with a recall of 83% at a precision of 99%.

Applying deep learning to classify pornographic images and videos.

Abstract: It is no secret that pornographic material is now a one-click-away from everyone, including children and minors. General social media networks are striving to isolate adult images and videos from normal ones. Intelligent image analysis methods can help to automatically detect and isolate questionable images in media. Unfortunately, these methods require vast experience to design the classifier including one or more of the popular computer vision feature descriptors. We propose to build a classifier based on one of the recently flourishing deep learning techniques. Convolutional neural networks contain many layers for both automatic features extraction and classification. The benefit is an easier system to build (no need for hand-crafting features and classifiers). Additionally, our experiments show that it is even more accurate than the state of the art methods on the most recent benchmark dataset.

The Psychological Well-Being of Content Moderators: The Emotional Labor of Commercial Moderation and Avenues for Improving Support

Abstract: An estimated 100,000 people work today as commercial content moderators. These moderators are often exposed to disturbing content, which can lead to lasting psychological and emotional distress. This literature review investigates moderators’ psychological symptomatology, drawing on other occupations involving trauma exposure to further guide understanding of both symptoms and support mechanisms. We then introduce wellness interventions and review both programmatic and technological approaches to improving wellness. Additionally, we review methods for evaluating intervention efficacy. Finally, we recommend best practices and important directions for future research. Content Warning: we discuss the intense labor and psychological effects of CCM, including graphic descriptions of mental distress and illness.