Italy


In recent years, deep neural networks have achieved
state-of-the-art performance in a variety of recognition and
segmentation tasks in medical imaging including brain tumor
segmentation. We investigate that segmenting a brain tumor is
facing to the imbalanced data problem where the number of pixels
belonging to the background class (non tumor pixel) is much
larger than the number of pixels belonging to the foreground
class (tumor pixel). To address this problem, we propose a multitask
network which is formed as a cascaded structure. Our model
consists of two targets, i.e., (i) effectively differentiate the brain
tumor regions and (ii) estimate the brain tumor mask. The first
objective is performed by our proposed contextual brain tumor
detection network, which plays a role of an attention gate and
focuses on the region around brain tumor only while ignoring the
far neighbor background which is less correlated to the tumor.
Different from other existing object detection networks which
process every pixel, our contextual brain tumor detection network
only processes contextual regions around ground-truth instances
and this strategy aims at producing meaningful regions proposals.
The second objective is built upon a 3D atrous residual network
and under an encode-decode network in order to effectively segment
both large and small objects (brain tumor). Our 3D atrous
residual network is designed with a skip connection to enables the
gradient from the deep layers to be directly propagated to shallow
layers, thus, features of different depths are preserved and used
for refining each other. In order to incorporate larger contextual
information from volume MRI data, our network utilizes the
3D atrous convolution with various kernel sizes, which enlarges
the receptive field of filters. Our proposed network has been
evaluated on various datasets including BRATS2015, BRATS2017
and BRATS2018 datasets with both validation set and testing
set. Our performance has been benchmarked by both regionbased
metrics and surface-based metrics. We also have conducted
comparisons against state-of-the-art approaches

ICPR 2020

A Multi-task Contextual Atrous Residual Network for Brain Tumor Detection &amp; Segmentation

brain tumor

imbalanced data

medical imaging

segmentation

deep learning

detection

ICPR 2020 is the premier international conference on Pattern Recognition, gathering leading researchers from around the world to present their latest achievements in Pattern Analysis and Recognition, applied Artificial Intelligence and Machine Learning. The topic of the year is " Putting Artificial intelligence to work on Patterns". 
For the first time, ICPR has employed a two-round review process similar to journal submissions, with new papers allowed to be submitted in either the first or second round and papers submitted in the first round and not accepted allowed to be revised and re-submitted for second round review. 

In this edition of the **ICPR 2020** Conference, there are 1407 Oral/Poster presentations organized in five Tracks: 
- Artificial Intelligence, Machine Learning for Pattern Analysis; 
- Biometrics, Human Analysis and Behavior Understanding; Computer Vision, Robotics and Intelligent Systems; 
- Document and Media Analysis; and 
- Image and Signal Processing. 

The **ICPR 2020** Main Conference program also includes 7 Keynotes from prominent world-renowned scientists, 8 Tutorials, 28 Demos, 8 Challenges, 2 Panels, as well as an Industry/Sponsor Exhibition. In addition, 41 Workshops on a range of important current and emerging research topics complete the ICPR 2020 program. 


A Multi-task Contextual Atrous Residual Network for Brain Tumor Detection & Segmentation

poster


Multimedia Forensics experts work consists in providing answers about integrity of a specific media content and from where it comes from. Exploitation of any traces from JPEG double compressed images is often one of the main investigative path to be used for these purposes. Thus it is fundamental to have tools and algorithms able to safely estimate the first quantization matrix to further proceed with camera model identification and related tasks. In this paper, a technique based on extensive simulation is proposed, with the aim to infer the first quantization for a certain numbers of Discrete Cosine Transform (DCT) coefficients exploiting local image statistics without using any a-priori knowledge. The method provides also a reliable confidence value for the estimation which is of great importance for forensic purposes. Experimental results w.r.t. the state-of-the-art demonstrate the effectiveness of the proposed technique both in terms of precision and overall reliability

Computational Data Analysis for First Quantization Estimation on JPEG Double Compressed Images

3D human pose estimation from a single 2D video is an extremely difficult task because computing 3D geometry from 2D images is an ill-posed problem. Recent popular solutions adopt fully-supervised learning strategy, which requires to train a deep network on a large-scale ground truth dataset of 3D poses and 2D images. However, such a large-scale dataset with natural images does not exist, which limits the usability of existing methods. While building a complete 3D dataset is tedious and expensive, abundant 2D in-the-wild data is already publicly available. As a consequence, there is a growing interest in the computer vision community to design efficient techniques that use the unsupervised learning strategy, which does not require any ground truth 3D data. Such methods can be trained with only natural 2D images of humans. In this paper we propose an unsupervised method for estimating 3D human pose in videos. The standard approach for unsupervised learning is to use the Generative Adversarial Network (GAN) framework. To improve the performance of 3D human pose estimation in videos, we propose a new GAN network that enforces body consistency over frames in a video. We evaluate the efficiency of our proposed method on a public 3D human body dataset.

Unsupervised 3D Human Pose Estimation in Multi-view-multi-pose Video

This paper proposes a method based on visual motion primitives to address the problem of action understanding. The approach builds in an unsupervised way a dictionary of kinematic primitives from a set of sub-movements obtained by segmenting the velocity profile of an action on the basis of local minima derived directly from the optical flow. The dictionary is then used to describe each sub-movement as a linear combination of atoms using sparse coding. The descriptive capability of the proposed motion representation is experimentally validated on the MoCA dataset, a collection of synchronized multi-view videos and motion capture data of cooking activities. 
The results show that the approach, despite its simplicity, has a good performance in action classification, especially when the motion primitives are combined over time. Also, the method is proved to be tolerant to view point changes, and can thus support cross-view action recognition. 
Overall, the method may be seen as a backbone of a general approach to action understanding, with potential applications in robotics.

Learning dictionaries of kinematic primitives for action classification

Auto encoding models have been extensively studied in recent years. They provide an efficient framework for sample generation, as well as for analysing feature learning. Furthermore, they are efficient in performing interpolations between data-points in semantically meaningful ways. In this paper, we introduce a method for generating sequence samples from auto encoders trained on flattened sequences (e.g video sample from auto encoders trained on single frames); as well as a canonical, dimension independent method for generating stochastic interpolations. The distribution of interpolation paths is represented as the distribution of a bridge process constructed from an artificial random data generating process in the latent space, having the prior distribution as its invariant distribution.

Interpolation in Auto Encoders with Bridge Processes

Event-based cameras record an asynchronous stream of per-pixel brightness changes. As such, they have numerous advantages over the standard frame-based cameras, including high temporal resolution, high dynamic range, and no motion blur. Due to the asynchronous nature, efficient learning of compact representation for event data is challenging. While it remains not explored the extent to which the spatial and temporal event "information" is useful for pattern recognition tasks. In this paper, we focus on single-layer architectures. We analyze the performance of two general problem formulations: the direct and the inverse, for unsupervised feature learning from local event data (local volumes of events described in space-time). We identify and show the main advantages of each approach. Theoretically, we analyze guarantees for an optimal solution, the possibility for asynchronous, parallel parameter update, and computational complexity. We present numerical experiments for object recognition. We evaluate the solution under the direct and the inverse problem and give a comparison with the state-of-the-art methods. Our empirical results highlight the advantages of both approaches for representation learning from event data. We show improvements of up to 9 $\%$ in the recognition accuracy compared to the state-of-the-art methods from the same class of methods.

Unsupervised Feature Learning for Event Data:
Direct vs Inverse Problem Formulation

In this work, we propose a method to simultaneously perform (i) biometric recognition (i.e., identify the individual), and (ii) device recognition, (i.e., identify the device) from a single biometric image, say, a face image, using a one-shot schema. Such a joint recognition scheme can be useful in devices such as smartphones for enhancing security as well as privacy. We propose to automatically learn a joint representation that encapsulates both biometric-specific and sensor-specific features. We evaluate the proposed approach using iris, face and periocular images acquired using near-infrared iris sensors and smartphone cameras. Experiments conducted using 14,451 images from 13 sensors resulted in a rank-1 identification accuracy of upto 99.81% and a verification accuracy of upto 100% at a false match rate of 1%.

One-shot Representational Learning for Joint Biometric and Device Authentication

Deep convolutional neural networks are widely used
to learn feature spaces for image classification tasks. We propose
cam-softmax, a generalisation of the final layer activations and
softmax function, that encourages deep feature spaces to exhibit
high intra-class compactness and high inter-class separability.
We provide an algorithm to automatically adapt the method’s
main hyperparameter so that it gradually diverges from the
standard activations and softmax method during training. We
report experiments using CASIA-Webface, LFW, and YTF face
datasets demonstrating that cam-softmax leads to representations
well suited to open-set face recognition and face pair matching.
Furthermore, we provide empirical evidence that cam-softmax
provides some robustness to class labelling errors in training
data, making it of potential use for deep learning from large
datasets with poorly verified labels.

Cam-softmax for discriminative deep feature learning

We design an interpretable network model by introducing explainable components into a Deep Neural Network (DNN). We substituted the first kernels of a Convolutional Neural Network (CNN) and a ResNet-50 with the well-known edge detecting filters such as Sobel, Prewitt, and other filters. Each filters' relative importance scores are measured with a variant of Layer-wise Relevance Propagation (LRP) method proposed by Bach et al. Since the effects of the edge detecting filters are well understood, our model provides three different scores to explain individual predictions: the scores with respect to (1) colors, (2) edge filters, and (3) pixels of the image. Our method provides more tools to analyze the predictions by highlighting the location of important edges and colors in the images. Furthermore, the general features of a category can be shown in our scores as well as individual predictions. At the same time, the model does not degrade performances on MNIST, Fruit360, and ImageNet datasets.

Color, Edge, and Pixel-wise Explanation of Predictions Based on Interpretable Neural Network Model

Facial makeup style transfer is an extremely challenging sub-field of image-to-image-translation. Due to this difficulty, state-of-the-art results are mostly reliant on the Face Parsing Algorithm, which segments a face into parts in order to easily extract makeup features. However, we find that this algorithm can only work well on
high-definition images where facial features can be accurately extracted. Faces in many real-world photos, such as those including a large background or multiple people, are typically of low-resolution, which considerably hinders state-of-the-art algorithms. In this paper, we propose an end-to-end holistic approach to effectively
transfer makeup styles between two low-resolution images. The idea is built upon a novel weighted multi-scale spatial attention module, which identifies salient pixel regions on low-resolution images in multiple scales, and uses channel attention to determine the most effective attention map. This design provides two benefits: low-resolution images are usually blurry to different extents, so a multi-scale architecture can select the most effective convolution kernel size to implement spatial attention; makeup is applied on both a macro-level (foundation, fake tan) and a micro-level (eyeliner, lipstick) so different scales can excel in extracting different makeup features. We develop an Augmented CycleGAN network that embeds our attention modules at selected layers to most effectively transfer makeup. We test our system with the FBD data set, which consists of many low-resolution facial images, and demonstrates that it outperforms state-of-the-art methods, particularly in transferring makeup for blurry images and partially occluded images.

Makeup Style Transfer on Low-Quality Images with Weighted Multi-Scale Attention

The paper addresses the problem of recognition of actions in video with low inter-class variability such as Table Tennis strokes. Two stream, "twin" convolutional neural networks are used with 3D convolutions both on RGB data and optical flow. Actions are recognized by classification of temporal windows. We introduce 3D attention modules and examine their impact on classification efficiency. In the context of the study of sportsmen performances, a corpus of the particular actions of table tennis strokes is considered. The use of attention blocks in the network speeds up the training step and improves the classification scores up to 5\% with our twin model. We visualize the impact on the obtained features and notice correlation between attention and player movements and position. Score comparison of state-of-the-art action classification method and proposed approach with attentional blocks is performed on the corpus. Proposed model with attention blocks outperforms previous model without them and our baseline.

Next from ICPR 2020

Computational Data Analysis for First Quantization Estimation on JPEG Double Compressed Images

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Offset Curves Loss for Imbalanced Problem in Medical Segmentation

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