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End to end feature learning method
NetVLAD: CNN architecture for weakly supervised place recognition （CVPR 2016）
This article is fromINRIA OfRelja
Arandjelović The work of others. This paper focuses on a specific application of case search—— Location recognition. In the problem of location recognition, Given a query picture, Mark data set by querying a large-scale location, Then use the location of those similar images to estimate the location of the query image. The author first usesGoogle
Street View Time
Machine Large scale location mark data set is established, Then a convolutional neural network architecture is proposed,NetVLAD—— takeVLAD Method embedded inCNN Network, And realize“end-to-end” Learning. This method is shown in the figure below：
OriginalVLAD Method inhard-assignment Operations are nondifferentiable（ Assign each local feature to its nearest center point）, So it can't be embedded directly intoCNN In the network, And participate in error back propagation. The solution to this article is to usesoftmax The function takes this.hard-assignment Operation converted tosoft-assignment operation—— Use1x1 Convolution sumsoftmax The probability that the local feature belongs to each central point is obtained by the function/ weight, Then assign it to have the maximum probability/ Center point of weight. thereforeNetVLAD It contains three parameters that can be learned,, Which is the top1x1 Convolution parameters, Used for predictionsoft-assignment, Represented as the center point of each cluster. And in the picture aboveVLAD
core The corresponding accumulated residual operation is completed in the layer. The author explained it to us through the figure belowNetVLAD Compared to the originalVLAD Advantage：（ Greater flexibility—— Learning better cluster center points）
Another improvement of this article isWeakly supervised triplet ranking
loss. In order to solve the problem that the training data may contain noise, taketriplet ranking
loss Replace positive and negative samples with potential positive samples（ Include at least one positive sample, But I'm not sure which one） And a clear negative sample set. And in training, The feature distance between the constrained query image and the most likely positive image in the positive sample set is smaller than the feature distance between the query image and all the images in the negative sample set.
Deep Relative Distance Learning: Tell the Difference Between Similar Vehicles
The next article focuses on vehicle identification/ Search problem, From Peking UniversityHongye Liu The work of others. As shown in the figure below, This problem can also be regarded as an instance search task.
Like many supervised deep case search methods, This paper aims to map the original image into a Euclidean feature space, And make it, More images of the same vehicle, Pictures of vehicles not of the same kind are far away. To achieve this effect, The common method is to optimizetriplet
ranking loss, Go to trainingCNN network. however, The author found that the originaltriplet ranking loss There are some problems, As shown in the figure below：
For the same sample, The triples on the left are adjusted by the loss function, The triples on the right are ignored. The difference between the two isanchor Different choices, This leads to instability in training. To overcome this problem, Author usecoupled
clusters loss（CCL） To replacetriplet ranking
loss. The characteristic of the loss function is to change the triple into a positive sample set and a negative sample set, And make the samples in the positive samples aggregate with each other, The negative samples are more distant from the positive samples, Thus, random selection is avoidedanchor Negative impact of samples. The specific effect of this loss function is shown in the figure below：
Finally, this paper aims at the particularity of vehicle problem, And combined with the above designcoupled clusters
loss, A hybrid network architecture is designed, And build the relevant vehicle database to provide the required training samples.
DeepFashion: Powering Robust Clothes Recognition and Retrieval with Rich
Annotations （CVPR 2016）
The final article is also published inCVPR 2016 upper, It introduces clothing recognition and search, The same task related to instance search, From the Chinese University of Hong KongZiwei
Liu The work of others. First, This article introduces a project namedDeepFashion Clothes database of. The database contains more than800K Clothes picture of,50 Fine grained categories and1000 Attributes, It also provides key points and cross posture of clothes/ Cross domain clothing relationships（cross-pose/cross-domain
pair correspondences）, Some specific examples are shown in the figure below：
Then in order to show the effect of the database, The author proposes a novel deep learning network,FashionNet—— Predict key points and attributes of clothes by combining, Learning to get more distinguishing features. The overall framework of the network is as follows：
FashionNet There are three stages in the forward calculation of： First stage, Enter a clothing picture into the blue branch of the network, To predict the visibility and location of key points of clothing. Second stage, Based on the key position predicted in the previous step, Key point pooling layer（landmark
pooling layer） Get local features of clothes. The third stage, take“fc6 global” Global characteristics and“fc6
local” Local features of“fc7_fusion”, As the final image feature.FashionNet Four loss functions are introduced, And use an iterative training method to optimize. These losses are： Regression loss corresponds to key point positioning,softmax Loss corresponds to key visibility and clothing category, Cross entropy loss function corresponding to attribute prediction and triple loss function corresponding to similarity learning between clothes. The author classifies clothes separately, Attribute prediction and clothing search, takeFashionNet Comparison with other methods, All have achieved significantly better results.
summary： When there is enough labeled data, Deep learning can learn image features and measurement functions at the same time. The idea behind it is to use a given metric function, The learning feature makes the feature have the best discrimination in this metric space. Therefore, the main research direction of end-to-end feature learning method is how to construct better feature representation and loss function form.
Be based onCNN Feature coding method of feature
The depth case search algorithm introduced in the above part of this paper, Focus on data-driven end-to-end feature learning methods and corresponding image search data sets. Next, This paper focuses on another problem： When these related search datasets are not available, How to extract effective image features. In order to overcome the shortage of domain data, A feasible strategy is toCNN Pre training model（ Training on other task data setsCNN Model, such asImageNet Image classification data set） On the basis of, Extract the feature map of one layer（feature
map）, Coding it to get image features suitable for instance search task. This part will be based on relevant papers in recent years, Introduce some main methods（ Special, All of theCNN Models are based onImageNet Pre training model of classification data set）.
Multi-Scale Orderless Pooling of Deep Convolutional Activation Features （ECCV
This article was published inECCV 2014 upper, It's from the University of North Carolina at Chapel HillYunchao Gong And the University of Illinois at Urbana ChampaignLiwei Wang The work of others.
Due to the globalCNN Feature lack of geometric invariance, Limited the classification and matching of variable scenes. The author attributes the problem to the overallCNN Features contain too much spatial information, Therefore, it is proposed thatmulti-scale
orderless pooling (MOP-CNN)—— takeCNN Characteristics and disorderVLAD Combination of coding methods.
MOP-CNN The main steps are, First of allCNN Network as“ Local feature” Extractor, Then extract the image's“ Local feature”, And adoptVLAD Put these“ Local feature” Encoded as image features on this scale, Finally, all scale image features are connected to form the final image features. The framework for feature extraction is as follows：
The author tests on two tasks: classification and instance search, As shown in the figure below, ProvedMOP-CNN Compared with generalCNN Global feature has better classification and search effect.
Exploiting Local Features from Deep Networks for Image Retrieval （CVPR 2015
This article was published inCVPR 2015 workshop upper, It's from the University of Maryland, Park CollegeJoe Yue-Hei
Ng The work of others. Many recent studies have shown that, Compared with the output of all connected layers, Characteristic map of convolution layer（feature
map） More suitable for instance search. This paper introduces how to transform the characteristic map of convolution into“ Local feature”, And useVLAD Encode it as an image feature. in addition, In addition, a series of experiments were carried out to observe the influence of the characteristic maps of different convolutions on the accuracy of case search.
Aggregating Deep Convolutional Features for Image Retrieval（ICCV 2015）
The next article is published inICCV 2015 upper, From Moscow Institute of physics and technologyArtem Babenko And Skolkovo Institute of TechnologyVictor
Lempitsky Work. As can be seen from the above two articles, Many deep case search methods use unordered coding methods. But includeVLAD,Fisher
Vector These coding methods are usually computationally expensive. To overcome this problem, This article designed a more simple, And a more efficient coding method——Sum pooing.Sum
pooling The specific definitions are as follows：
Among them is the local feature of convolution layer in spatial position（ The method of extracting local features here, Consistent with the previous article）. in usesum
pooling after, Further execution of global featuresPCA andL2 Normalize to get the final feature. Author andFisher Vector,Triangulation
embedding andmax pooling These methods are compared, Demonstratedsum pooling The method is not only simple in calculation, And it works better.
Come from Deep learning lecture https://zhuanlan.zhihu.com/p/22265265
Where to Focus: Query Adaptive Matching for Instance Retrieval Using
Convolutional Feature Maps （arXiv 1606.6811）
This paper is in《Particular object retrieval with integral max-pooling of CNN activations
》 On the basis of this, a new method is proposedReranking Method.
Before the beginning of the narrative, Let's understand convolutionFeature Map
The image above is a visualization of different convolutions, We can see,early convolutional layer Capture a major visual model, andlate
convolutional layer It's more about the representation of the object outline.
In this paperReranking Process finishing：
One Method introduction
1 productionbase regions, There are two ways：
1.1 Feature Map Pooling（FMP）
For a certain layer of convolution network, If there isD Convolution kernel, Can produceD ZhangFeature Map（FM） chart. For eachFM, We choose a non-zero response as aBase
Regions（BR）, suchBR The number ofFM Quantity. Then onBR The response value insum-pooling, Every one of themFM You get a valuefd. But for a givenImage, Quite a lotFM There's a lot of overlap, So it corresponds topooling Features, that isfd Basically the same, We haveFd Value for a cluster, Set cluster center toK.（ It can be understood hereD individualBR ClusteringK individualBR）.
sum-pooling Schema meaning（ Add the response values）
1.2 Overlapped Spatial Pyramid Pooling （OSPP）
OSPP Law and suggestionR-MAC In the paperRegions Same extraction method, Corresponding to different scales, We extract l × (l + m − 1) individualRegions, Its width= 2
min(W; H)/(l + 1), Then evenly sample outm Regions（BR region）
2 Reranking process
Paper proposesQuery Adaptive Matching（QAM） A method ofReranking, That's rightBR To merge into oneMerge
Region, And this selection process turns into an optimization problem. Use this process, For a picture, Elect andquery The most similar merge region（merge regions）
Through the above optimization process（ In fact, the last is a common quadratic programming problem） Let's take out a pictureMerge Region. Calculatedquery andMerge
region As the similarity score ofReranking OfScore, Final ranking.
Let's talk about it. I'm up thereBase region Generation process of CombinationQAM Understanding：
aboutFMP Method： Every lastFeature Map We'll get oneBase Region, therefore, adoptFMP Method, What we got in the endBase
region The number of convolution kernels in this layer. And ultimatelybase-region Representation, The paper does use onesum-pooling Way, Every one of themBase
Region Only one value will come out in the end, And in the process of optimization,Merge
Region The final representation will also become a value, It's impossible toquery The inner product of the vector of. That's what I've been wondering about this paper, If any senior（ It is better to hear Tao than to hear it） I see the problem, Please give me some advice.（ It could also be a mistake in the paper）
aboutOSPP method： Because in differentFM On different scalesBase Region Selection, So it's differentBase
Region There are different vector representations. We can easily apply itQAM YesBase Region Select.
Deep Image Retrieval: Learning global representations for image search. In
Address of thesis：https://arxiv.org/abs/1604.01325 <https://arxiv.org/abs/1604.01325>
extended version：end to end learning of deep visual representations for image
retrieval, in arxiv, 16.10. <https://arxiv.org/pdf/1610.07940v1.pdf>
Look at the picture and talk：
As can be seen from the figure, the overall framework of this paper：
1 Be based onpre-trained model on Imagenet（ asVGG16）
2 fromLandmarks dataset, Dig out onefull perhapsclean Data set（ Include category labels Full Datset andbounding box
3 Data setFull Daset To carry outfinetune, hisloss It's a general classificationloss; useClean
Dataset To carry outfinetune, hisloss bytriplet loss
4 Using the trained model to open data setfeature extraction,similarity measure Adopt European distance（dot product）
It is also used in the paperquery expansion Way toboost performance.
Let's focus on the above1 and3.
（ For the acquisition of dataset, In fact, I didn't understand it, Just understand that you need to provide oneclean Data set of）
1 pre-trained model And theframework.
Here we can useAlexNet,VGGNet,Resnet etc. depend on与你想要的效果（performance和speed）
对于VGGNet（如VGG16）,摘掉全连接层,取而代之的是RPN + RoI Pooling +shift + fc + L2等.
也可以看extended version的论文,将RPN彻底取代rigid grid,形成end2end的framework.
至于shift + fc的作用就是取代一般pipeline中的PCA Whitten.
Particular Object Retrieval with Integral Max-Pooling of CNN Activations. In
ICLR, 2016 <https://arxiv.org/abs/1511.05879>.)
2 MAC feature的简单介绍：（pooling可以用sum也可以用max,或者其他的）
R-MAC：一般的MAC是针对whole image的feaute map,而R-MAC的做法就是参考RoI Pooling的做法,将bounding
box 投影到feature map上,然后仅在投影在feature map上的区域进行pooling.
loss或者简单的classification,对应的数据集为Clean Dataset和Full Dataset.
（不过论文中提到用Full Dataset训练的classification的模型来初始化triplet loss的模型,效果更佳）
【CVPR 2016】faster r-cnn features for instance search 笔记
1.Image-wise pooling of activations (IPA)
2.Region-wise pooling of activations (RPA)
4.Class-Agnostic Spatial Reranking (CA-SR)
5.Class-Specific Spatial Reranking (CS-SR)
整个网络从总体上看是faster-rcnn的网络结构,上面一部分是faster-rcnn 的RPN net部分,RPN net的输出rpn
是ROI pooling 加上三个全连接层,输出是class probabilities.
Image-wise pooling of activations(IPA):
Net,并且经过了reLu层之后）,然后做pooling,具体pooling 的方法作者是借鉴另外一篇paper：《particular object
with integeral max-pooling of CNN activations》.举个例子来说：如果最后conv5_3得出的feature
为每一个卷积核卷积之后的feature map,这样对于每一个W*H的feature Map 采用max-pooling 或者sum-pooling
Region-wise pooling of activations(RPA):
就是找出region proposals 的ROI pooling,在ROI pooling层上面做max-pooling.
fine-tuning faster rcnn
fine tuning 采用两种方式：
strategy1: fine tuning ROI pooling之后的三层网络.
strategy2:fine tuning network after conv_2
fine-tuining 所使用图像为query 图像以及将其做horizontal flip之后的图像（个人感觉图像好少）.
Class-Agnostic Spatial Reranking (CA-SR):假设类别不可知,计算每一个query bounding
Class-Specific Spatial Reranking(CS-SR):使用和query相同的instances