  Word spotting has become a field of strong research interest in document
image analysis over the last years. Recently, AttributeSVMs were proposed which
predict a binary attribute representation. At their time, this influential
method defined the state-of-the-art in segmentation-based word spotting. In
this work, we present an approach for learning attribute representations with
Convolutional Neural Networks (CNNs). By taking a probabilistic perspective on
training CNNs, we derive two different loss functions for binary and
real-valued word string embeddings. In addition, we propose two different CNN
architectures, specifically designed for word spotting. These architectures are
able to be trained in an end-to-end fashion. In a number of experiments, we
investigate the influence of different word string embeddings and optimization
strategies. We show our Attribute CNNs to achieve state-of-the-art results for
segmentation-based word spotting on a large variety of data sets.
