Contemporary deep learning techniques have made image recognition a reasonably reliable technology. However training effective photo classifiers typically takes numerous examples which limits image recognition's scalability and applicability to scenarios where images may not be available. This has motivated investigation into zero-shot learning, which addresses the issue via knowledge transfer from other modalities such as text. In this paper we investigate an alternative approach of synthesizing image classifiers: almost directly from a user's imagination, via freehand sketch. This approach doesn't require the category to be nameable or describable via attributes as per zero-shot learning. We achieve this via training a model regression network to map from free-hand sketch space to the space of photo classifiers. It turns out that this mapping can be learned in a category-agnostic way, allowing photo classifiers for new categories to be synthesized by user with no need for annotated training photos. We also demonstrate that this modality of classifier generation can also be used to enhance the granularity of an existing photo classifier, or as a complement to name-based zero-shot learning.
One ZSL study is related to ours in use of visually abstract (cartoon) person inputs to generate classifiers for photos @cite_24 . However, this significantly easier and less general than our task. It only uses cartoon as a manipulation modality to solicit user input. It then uses the annotated pose of persons in the cartoon and photo domain as the representation. This means that: (i) By using a high level pose representation, it does not directly address the whole computer vision problem of sketch and photo interpretation in the respective domains. (ii) This cross-domain mapping of cartoon-person-pose to photo-person-pose is much simpler than the more general mapping between cartoon images and photo images overall. (iii) As a result it is constrained to recognizing photo categories which can be defined by the pose of one or two persons. In contrast, our more general approach does not require any such pose annotation in either modality, and can apply to arbitrary categories.
@cite_24
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One of the main challenges in learning fine-grained visual categories is gathering training images. Recent work in Zero-Shot Learning (ZSL) circumvents this challenge by describing categories via attributes or text. However, not all visual concepts, e.g., two people dancing, are easily amenable to such descriptions. In this paper, we propose a new modality for ZSL using visual abstraction to learn difficult-to-describe concepts. Specifically, we explore concepts related to people and their interactions with others. Our proposed modality allows one to provide training data by manipulating abstract visualizations, e.g., one can illustrate interactions between two clipart people by manipulating each person’s pose, expression, gaze, and gender. The feasibility of our approach is shown on a human pose dataset and a new dataset containing complex interactions between two people, where we outperform several baselines. To better match across the two domains, we learn an explicit mapping between the abstract and real worlds. We present a novel approach for synthesizing photo-realistic images of people in arbitrary poses using generative adversarial learning. Given an input image of a person and a desired pose represented by a 2D skeleton, our model renders the image of the same person under the new pose, synthesizing novel views of the parts visible in the input image and hallucinating those that are not seen. This problem has recently been addressed in a supervised manner, i.e., during training the ground truth images under the new poses are given to the network. We go beyond these approaches by proposing a fully unsupervised strategy. We tackle this challenging scenario by splitting the problem into two principal subtasks. First, we consider a pose conditioned bidirectional generator that maps back the initially rendered image to the original pose, hence being directly comparable to the input image without the need to resort to any training image. Second, we devise a novel loss function that incorporates content and style terms, and aims at producing images of high perceptual quality. Extensive experiments conducted on the DeepFashion dataset demonstrate that the images rendered by our model are very close in appearance to those obtained by fully supervised approaches. Human pose as a query modality is an alternative and rich experience for image and video retrieval. It has interesting retrieval applications in domains such as sports and dance databases. In this work we propose two novel ways for representing the image of a person striking a pose, one looking for parts and other looking at the whole image. These representations are then used for retrieval. Both the representations are obtained using deep learning methods.In the first method, we make the following contributions: (a) We introduce deep poselets' for pose-sensitive detection of various body parts, built on convolutional neural network (CNN) features. These deep poselets significantly outperform previous instantiations of Berkeley poselets [6], and (b) Using these detector responses, we construct a pose representation that is suitable for pose search, and show that pose retrieval performance is on par with the previous methods. In the second method, we make the following contributions: (a) We design an optimized neural network which maps the input image to a very low dimensional space where similar poses are close by and dissimilar poses are farther away, and (b) We show that pose retrieval system using these low dimensional representation is on par with the deep poselet representation and is on par with the previous methods.The previous works with which the above two methods are compared include bag of visual words [44], Berkeley poselets[6] and human pose estimation algorithms [52]. All the methods are quantitatively evaluated on a large dataset of images built from a number of standard benchmarks together with frames from Hollywood movies. For human pose search, two novel pose descriptors (D-I and D-II) are proposed.D-I pools scores of deep poselets (body part detectors in a specific pose).D-II, maps an image such that similar and dissimilar pose images are separated.Both descriptors use CNNs and do not need an explicit human pose estimation.These have been shown to outperform other pose descriptors by large margins. In this paper we address the problem of generating person images conditioned on a given pose. Specifically, given an image of a person and a target pose, we synthesize a new image of that person in the novel pose. In order to deal with pixel-to-pixel misalignments caused by the pose differences, we introduce deformable skip connections in the generator of our Generative Adversarial Network. Moreover, a nearest-neighbour loss is proposed instead of the common L1 and L2 losses in order to match the details of the generated image with the target image. We test our approach using photos of persons in different poses and we compare our method with previous work in this area showing state-of-the-art results in two benchmarks. Our method can be applied to the wider field of deformable object generation, provided that the pose of the articulated object can be extracted using a keypoint detector.