Cosine Metric Supervised Deep Hashing

Hashing has drawn more and more attention in image retrieval due to its high search speed and low storage cost. Traditional hashing methods project the high-dimensional hand-crafted visual features to compact binary codes by linear or non-linear hashing functions. Deep hashing methods, which integrate image representation learning and hash functions learning into a unified framework, have shown more superior performance. Most of existing supervised deep hashing methods mainly consider the semantic similarities among images by using pair-wise or triplet-wise constraints as supervision information. However, as a kind of crucial information, the rankings of the retrieval results, are neglected. Consequently, the produced hash codes may be suboptimal. In this paper, a new Deep Hashing with Top Similarity Preserving (DHTSP) method is proposed to optimize the quality of hash codes for image retrieval. Specifically, we utilize AlexNet to extract discriminative image representations directly from the raw image pixels and learn hash functions simultaneously. Then a top similarity preserving loss function is designed to preserve the similarity of returned images at the top of the ranking list. Experimental results on three benchmark datasets show that our proposed method outperforms most of state-of-the-art deep hashing methods and traditional hashing methods.

Deep hashing methods have achieved promising results for large-scale image retrieval recently. To accelerate the subsequent Hamming ranking process, the multi-index approach has been proposed to reduce the computations for the Hamming distance. However, the binary codes output by the previous deep hashing methods may not be optimally compatible with the multi-index approach. In this paper, we present a novel Deep Index-Compatible Hashing (DICH) method for fast image retrieval, which can learn similarity-preserving binary codes that are more compatible with the multi-index approach. With the learned binary codes, both the size of the intermediate result set produced by the multi-index approach and the number of the candidate images can be reduced, which can accelerate the Hamming ranking process. By taking advantage of the unique feature of DICH, we further propose a block-based ranking strategy to quickly rank the candidate images without calculating the Hamming distance. Extensive evaluations demonstrate that the proposed method can significantly reduce the retrieval time with almost no loss of retrieval accuracy.

Multiple-Instance ranking based deep hashing for multi-Label image retrieval

Deep hashing methods utilize an end-to-end framework to mutually learn feature representations and hash codes, thereby achieving a better retrieval performance. Traditional supervised hashing methods adopt handcrafted features for hashing function learning and then generate hash codes through classification and quantization. The lack of adaptability and independence of the quantization procedure leads to low retrieval accuracy of supervised hashing methods with handcrafted features in image retrieval. In this study, a non-relaxation deep hashing method for fast image retrieval is proposed. In this method, a differentiable host thresholding function is used to encourage hash-like codes to approach -1 or 1 non-linearly at the output of the convolutional neural, instead of the symbol function for quantization used in the traditional method. The output of the host thresholding function is directly used to compute the network training error, and a loss function is elaborately designed with the norm to constrain each bit of the hash-like code to be as binary as possible. Finally, a symbol function is added outside the trained network model to generate binary hash codes for image storage and retrieval in a low-dimensional binary space. Extensive experiments on two large-scale public datasets show that our method can effectively learn image features, generate accurate binary hash codes, and outperform state-of-the-art methods in terms of the mean average precision.

Hash coding has been widely used in the approximate nearest neighbor search for large-scale image retrieval. Recently, many deep hashing methods have been proposed and shown largely improved performance over traditional feature-learning-based methods. Most of these methods examine the pairwise similarity on the semantic-level labels, where the pairwise similarity is generally defined in a hard-assignment way. That is, the pairwise similarity is '1' if they share no less than one class label and '0' if they do not share any. However, such similarity definition cannot reflect the similarity ranking for pairwise images that hold multiple labels. In this paper, a new deep hashing method is proposed for multi-label image retrieval by re-defining the pairwise similarity into an instance similarity, where the instance similarity is quantified into a percentage based on the normalized semantic labels. Based on the instance similarity, a weighted cross-entropy loss and a minimum mean square error loss are tailored for loss-function construction, and are efficiently used for simultaneous feature learning and hash coding. Experiments on three popular datasets demonstrate that, the proposed method outperforms the competing methods and achieves the state-of-the-art performance in multi-label image retrieval.

Hashing method maps similar data to binary hashcodes with smaller hamming distance, which has received broad attention due to its low storage cost and fast retrieval speed. With the rapid development of deep learning, deep hashing methods have achieved promising results in efficient information retrieval. Most existing deep hashing methods adopt pairwise or triplet losses to deal with similarities underlying the data, but their training are difficult and less efficient because O(n2) data pairs and O(n3) triplets are involved. To address these issues, we propose a novel deep hashing algorithm with unary loss which can be trained very efficiently. First of all, we introduce a Unary Upper Bound of the traditional triplet loss, thus reducing the complexity to O(n) and bridging the classificationbased unary loss and the triplet loss. Second, we propose a novel Semantic Cluster Deep Hashing (SCDH) algorithm by introducing a modified Unary Upper Bound loss, named Semantic Cluster Unary Loss (SCUL). The resultant hashcodes form several compact clusters, which means hashcodes in the same cluster have similar semantic information. We also demonstrate that the proposed SCDH is easy to be extended to semi-supervised settings by incorporating the state-of-the-art semi-supervised learning algorithms. Experiments on large-scale datasets show that the proposed method is superior to state-of-the-art hashing algorithms.

The deep hash method has been proved to be the most efficient and approximate nearest neighbor search technique for large-scale image retrieval. However, the existing deep hashing methods have few cases in medical image retrieval, so we propose a deep hash network model for medical image retrieval. Firstly, in order to enhance the feature extraction and learning ability in the network model, we add SENet visual attention mechanism into each residual module of the backbone network ResNet50 for feature extraction. Then the extracted high-dimensional semantic features are added to the Cauchy hash module to generate a compact, centralized hash code, and then complete medical image retrieval. So as to enhance experimental comparison, the proposed method was validated experimentally on NUS-WIDE and MURA data sets. A large number of experiments verify that the proposed method is reliable and can be used for medical image retrieval. Compared with other existing hash algorithms, the retrieval performance of the proposed method has certain improved. The framework of the proposed method is shown in Figure 1.

In recent years, with the explosion of multimedia data from search engines, social media, and e-commerce platforms, there is an urgent need for fast retrieval methods for massive big data. Hashing is widely used in large-scale and high-dimensional data search because of its low storage cost and fast query speed. Thanks to the great success of deep learning in many fields, the deep learning method has been introduced into hashing retrieval, and it uses a deep neural network to learn image features and hash codes simultaneously. Compared with the traditional hashing methods, it has better performance. However, existing deep hashing methods have some limitations; for example, most methods consider only one kind of supervised loss, which leads to insufficient utilization of supervised information. To address this issue, we proposed a triplet deep hashing method with joint supervised loss based on the convolutional neural network (JLTDH) in this work. The proposed method JLTDH combines triplet likelihood loss and linear classification loss; moreover, the triplet supervised label is adopted, which contains richer supervised information than that of the pointwise and pairwise labels. At the same time, in order to overcome the cubic increase in the number of triplets and make triplet training more effective, we adopt a novel triplet selection method. The whole process is divided into two stages: In the first stage, taking the triplets generated by the triplet selection method as the input of the CNN, the three CNNs with shared weights are used for image feature learning, and the last layer of the network outputs a preliminary hash code. In the second stage, relying on the hash code of the first stage and the joint loss function, the neural network model is further optimized so that the generated hash code has higher query precision. We perform extensive experiments on the three public benchmark datasets CIFAR-10, NUS-WIDE, and MS-COCO. Experimental results demonstrate that the proposed method outperforms the compared methods, and the method is also superior to all previous deep hashing methods based on the triplet label.

Recently, image retrieval from massive images has been considered as a crucial research topic. Current deep hashing methods mostly rely on convolutional neural network (CNN) as the backbone network. However, the CNN-based deep hashing methods require multiple convolution operations to capture global information, which lead to the loss of many shallow-level features in the process of feature extraction and affect the accuracy of binary hashing codes. To address such limitations, a new deep hashing method is proposed and studied in this paper by adopting the vision transformer model as the backbone network and designing a spatial reduction layer with channel attention mechanism fused. Such a deep hashing method can capture long-range dependencies effectively. The experiments on the CIFAR-10, NUSWIDE and ImageNet datasets indicate that the proposed method achieves higher mean average precision than other state-of-the-art hashing methods, thereby confirming the outstanding performance on image retrieval.

Hashing methods can overcome the problems of low retrieval efficiency and high storage cost. Existing hashing methods use either only one feature or multiple features as the input of one kernel function. The fact that different kernel functions have different roles and different characteristics and contain different information is ignored. In this paper, an adaptive multi-feature and multi-kernel hashing learning (MFMKH) algorithm is proposed, which can adaptively combine the feature weight coefficient and the kernel weight coefficient and double-combine the multi-feature and multi-kernel advantages. The fusion of these features in the algorithm solves the disadvantage of single feature containing insufficient information. In addition, the use of a variety of different kernel functions can compensate for the lack of a single-kernel learning ability and has the dual advantages of multi-feature fusion and multi-kernel learning. Experiments on the standard datasets IRMA, Ultrasound, and Cifar10 have shown that the retrieval performance of the proposed method clearly outperforms other similar kernel-based hashing learning methods. In addition, compared to the supervised deep hashing, the retrieval performance of the proposed method is competitive on the Cifar10 dataset in the case of the reduced training time.

Deep hashing has been widely applied in large scale image retrieval due to its high computation efficiency and retrieval performance. Recently, training deep hashing networks with a triplet ranking loss become a common framework. However, most of the triplet ranking loss based deep hashing methods cannot obtain satisfactory retrieval performance due to their ignoring the relative similarities among the objects. In this paper, we propose a method to learn the discriminative object features and utilize these features to compute the adaptive margins of the proposed loss for learning powerful hash codes. Experimental results show that our learned hash codes can yield state-of-the-art retrieval performance on three challenging datasets

Recently, deep learning has been successfully applied to the problem of hashing, yielding remarkable performance compared to traditional methods with hand-crafted features. However, most of existing deep hashing methods are designed for the supervised scenario and require a large number of labeled data. In this paper, we propose a novel semi-supervised hashing method for image retrieval, named Deep Hashing with a Bipartite Graph (DHBG), to simultaneously learn embeddings, features and hash codes. More specifically, we construct a bipartite graph to discover the underlying structure of data, based on which an embedding is generated for each instance. Then, we feed raw pixels as well as embeddings to a deep neural network, and concatenate the resulting features to determine the hash code. Compared to existing methods, DHBG is a universal framework that is able to utilize various types of graphs and losses. Furthermore, we propose an inductive variant of DHBG to support out-of-sample extensions. Experimental results on real datasets show that our DHBG outperforms state-of-the-art hashing methods.

Hashing methods have been widely used in large-scale image retrieval. However, the constraints on the hash codes of similar images learned by the previous hashing methods are too strong, which may lead to overfitting and difficult convergence. Besides, the binary codes output by the previous hashing methods are not optimally compatible with the multi-index approach, which is the most effective method for Hamming distance query acceleration. In this paper, we propose a novel Robust and Index-Compatible Deep Hashing (RICH) method to learn compact similarity-preserving binary codes, which focuses on improving the retrieval accuracy and time efficiency simultaneously. With the learned binary codes, we can achieve better results compared with the state-of-the-arts in retrieval accuracy. Meanwhile, remarkable promotions of the retrieval time efficiency have been made in the Hamming distance query process.

Similarity preserving hashing methods have drawn a lot of attention lately due to their efficiency in performing approximate nearest neighbor searches on high-dimensional large-scale multimedia data. With the development of deep learning techniques, deep supervised hashing has attracted increasing attention lately. Existing deep hashing methods usually take a two-step strategy to generate hash codes. They generate continuous hash codes and then discretize them into binary hash codes. Deep hashing methods have outperformed other methods significantly, but there is still a huge quantization gap between the discrete hash codes and continuous hash codes. The quantization gap prevents existing deep hashing methods from achieving better performance. In this paper, we propose deep supervised hashing with dynamic weighting scheme (DHDW), a novel deep hashing method that narrows down the quantization gap by utilizing Hamming distance information during training. Specifically, we introduce Hamming distance and stability information into the training phase by applying a novel dynamic weighting module to all data of a mini-batch. The dynamic weighting module we present is constructed from real-time Hamming distance and stability information. Additionally, the dynamic weighting module is compatible with all existing pairwise deep supervised hashing methods. Comprehensive experiments show that DHDW outperforms existing state-of-the-art methods on several standard datasets and benchmarks, and the dynamic weighting module effectively improves the performance of deep learning to hash methods.

K-nearest neighbors (KNN) has been successfully used for recommendation, but querying neighbors of high quality is nearly impossible when the feature space is small or has limited training data. However, due to privacy requirements and government policies, directly transferring data from one data owner to another is not workable. Therefore, we propose a novel KNN approach, secured federated KNN (SF-KNN), that takes privacy requirements into consideration and builds a federated model to gain global neighbors with joint parties, in order to improve the model performance. Specifically, it empowers the parties to train high-quality models with little data. More importantly, it makes cross-domain training possible. We implement SF-KNN on Euclidean and cosine metrics using user-based and item-based methods. In our experiment, we evaluate the proposed SF-KNN on three data sources, MovieLens, Netflix, and Amazon, and several diverse domains, movies, books, clothes, jewellery and food, by comparing it against various baselines. The experiment results indicate that SF-KNN is able to learn more precise neighbors than a local KNN trained by parties individually. In general, it outperforms the local KNN on all of the datasets, reaching 15% average accuracy gain on the Euclidean metric and 8% of it on the cosine metric when simulating 10 parties across all data sources.