3,113 research outputs found
Fine-grained Discriminative Localization via Saliency-guided Faster R-CNN
Discriminative localization is essential for fine-grained image
classification task, which devotes to recognizing hundreds of subcategories in
the same basic-level category. Reflecting on discriminative regions of objects,
key differences among different subcategories are subtle and local. Existing
methods generally adopt a two-stage learning framework: The first stage is to
localize the discriminative regions of objects, and the second is to encode the
discriminative features for training classifiers. However, these methods
generally have two limitations: (1) Separation of the two-stage learning is
time-consuming. (2) Dependence on object and parts annotations for
discriminative localization learning leads to heavily labor-consuming labeling.
It is highly challenging to address these two important limitations
simultaneously. Existing methods only focus on one of them. Therefore, this
paper proposes the discriminative localization approach via saliency-guided
Faster R-CNN to address the above two limitations at the same time, and our
main novelties and advantages are: (1) End-to-end network based on Faster R-CNN
is designed to simultaneously localize discriminative regions and encode
discriminative features, which accelerates classification speed. (2)
Saliency-guided localization learning is proposed to localize the
discriminative region automatically, avoiding labor-consuming labeling. Both
are jointly employed to simultaneously accelerate classification speed and
eliminate dependence on object and parts annotations. Comparing with the
state-of-the-art methods on the widely-used CUB-200-2011 dataset, our approach
achieves both the best classification accuracy and efficiency.Comment: 9 pages, to appear in ACM MM 201
No Spare Parts: Sharing Part Detectors for Image Categorization
This work aims for image categorization using a representation of distinctive
parts. Different from existing part-based work, we argue that parts are
naturally shared between image categories and should be modeled as such. We
motivate our approach with a quantitative and qualitative analysis by
backtracking where selected parts come from. Our analysis shows that in
addition to the category parts defining the class, the parts coming from the
background context and parts from other image categories improve categorization
performance. Part selection should not be done separately for each category,
but instead be shared and optimized over all categories. To incorporate part
sharing between categories, we present an algorithm based on AdaBoost to
jointly optimize part sharing and selection, as well as fusion with the global
image representation. We achieve results competitive to the state-of-the-art on
object, scene, and action categories, further improving over deep convolutional
neural networks
CNN Features off-the-shelf: an Astounding Baseline for Recognition
Recent results indicate that the generic descriptors extracted from the
convolutional neural networks are very powerful. This paper adds to the
mounting evidence that this is indeed the case. We report on a series of
experiments conducted for different recognition tasks using the publicly
available code and model of the \overfeat network which was trained to perform
object classification on ILSVRC13. We use features extracted from the \overfeat
network as a generic image representation to tackle the diverse range of
recognition tasks of object image classification, scene recognition, fine
grained recognition, attribute detection and image retrieval applied to a
diverse set of datasets. We selected these tasks and datasets as they gradually
move further away from the original task and data the \overfeat network was
trained to solve. Astonishingly, we report consistent superior results compared
to the highly tuned state-of-the-art systems in all the visual classification
tasks on various datasets. For instance retrieval it consistently outperforms
low memory footprint methods except for sculptures dataset. The results are
achieved using a linear SVM classifier (or distance in case of retrieval)
applied to a feature representation of size 4096 extracted from a layer in the
net. The representations are further modified using simple augmentation
techniques e.g. jittering. The results strongly suggest that features obtained
from deep learning with convolutional nets should be the primary candidate in
most visual recognition tasks.Comment: version 3 revisions: 1)Added results using feature processing and
data augmentation 2)Referring to most recent efforts of using CNN for
different visual recognition tasks 3) updated text/captio
Cross-convolutional-layer Pooling for Image Recognition
Recent studies have shown that a Deep Convolutional Neural Network (DCNN)
pretrained on a large image dataset can be used as a universal image
descriptor, and that doing so leads to impressive performance for a variety of
image classification tasks. Most of these studies adopt activations from a
single DCNN layer, usually the fully-connected layer, as the image
representation. In this paper, we proposed a novel way to extract image
representations from two consecutive convolutional layers: one layer is
utilized for local feature extraction and the other serves as guidance to pool
the extracted features. By taking different viewpoints of convolutional layers,
we further develop two schemes to realize this idea. The first one directly
uses convolutional layers from a DCNN. The second one applies the pretrained
CNN on densely sampled image regions and treats the fully-connected activations
of each image region as convolutional feature activations. We then train
another convolutional layer on top of that as the pooling-guidance
convolutional layer. By applying our method to three popular visual
classification tasks, we find our first scheme tends to perform better on the
applications which need strong discrimination on subtle object patterns within
small regions while the latter excels in the cases that require discrimination
on category-level patterns. Overall, the proposed method achieves superior
performance over existing ways of extracting image representations from a DCNN.Comment: Fixed typos. Journal extension of arXiv:1411.7466. Accepted to IEEE
Transactions on Pattern Analysis and Machine Intelligenc
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