Computer-vision based polyp detection in underwater images

bachelor's thesis

Kristijan Shirgoski (Author), Matej Kristan (Mentor)

Abstract

Detekcija objektov je priljubljena tematika na področjih računalniškega vida in strojnega učenja. Reševanje problemov detekcije objektov predstavlja precejšenj izziv in v literaturi obstaja veliko različnih pristopov. Pristopi se konceptualno precej razlikujejo, različne pa so tudi njihove časovne zahtevnosti. Cilj diplomske naloge je ustvariti splošen pristop za zaznavanje objektov v sliki, v našem primeru polipe meduze Aurelia aurita. Za te polipe je značilno, da se na gosto širijo preko koral. Ena od značilnih tematik pri detekciji objektov je iskanje določenih regij v sliki, ki nas zanimajo. Ponavadi iščemo regije različnih velikosti. Zato smo predlagali uporabo modela agregirane značilnice po kanalih (ACF), ki se je učil na anotaciji iz naše zbirke. Iz vsake regije moramo izluščiti podatke, na podlagi katerih posamezni regiji določimo lastnosti ali karakteristike. V tej diplomski nalogi smo to izvedli s pomočjo konvolucijske nevronske mreže (CNN), ki je bila trenirana na podatkovni zbirki MNIST. Poleg tega sta za klasifikacijo in ocenjevanje njene pravilnosti uporabljena binarni klasifikator podpornih vektorjev (SVM) z linearnim jedrom ter L2 regularizirana logistična regresija. Zelo verjetno je, da vsaki anotaciji pripada več regij, ki jih ACF predlaga. Zato je potrebno veliko teh regij odstraniti s pomočjo metode tlačenja nemaksimumov, ki se naivno osredotoča na tiste regije, ki imajo višje ocene. Algoritme, ki smo jih uporabljali, so bili učeni in preizkušeni na novi zbirki podatkov, ki je sestavljena iz skoraj 40000 pravokotnih anotacij v 35 slik. Dosegli smo zelo obetavne rezultate ter analizirali prednosti in slabosti našega pristopa.

Keywords

object detection;computer vision;machine learning;ACF;CNN;SVM;regression;non-maximum suppression;computer science;computer and information science;diploma;

Data

Language:	English
Year of publishing:	2015
Typology:	2.11 - Undergraduate Thesis
Organization:	UL FRI - Faculty of Computer and Information Science
Publisher:	[K. Shirgoski]
UDC:	004.932.72'1:004.85(043.2)
COBISS:	1536643523
Views:	972
Downloads:	150
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary title:	Computer-vision based polyp detection in underwater images
Secondary abstract:	Object detection is a popular topic in computer vision and machine learning. Numerous approaches have been proposed in literature to address the challenging task of general object detection. The approaches vary conceptually as well as in the level of computational intensity. The goal of this thesis was to develop a pipeline of state-of-the-art algorithms to detect polyps of the Aurelia aurita jellyfish, which are densely spread across corals. In object detection problems, a mandatory task is searching the image for regions of interest, preferably of several sizes. We propose a trained aggregated channel features (ACF) model to do that. In order to later classify these regions, first they need to have some features or characteristics extracted from them. In this thesis, this is performed by a convolutional neural network (CNN) trained on the MNIST dataset. Furthermore, a binary support vector machines (SVM) classifier with linear kernel and L2-regularized logistic regression is used to classify the features and determine the probability of correctly classifying them. It is very likely that several regions are proposed for each ground truth, so the regions must undergo a non-maximum suppression which uses the probability outputs from the logistic regression to group the local regions together, greedily prioritizing based on the probability distribution. The algorithms were trained and tested on 35 images consistent of nearly 40000 rectangle annotations from a newly annotated dataset. We have achieved very promising results and analyzed the strengths and weaknesses of our approach.
Secondary keywords:	detekcija objektov;računalniški vid;strojno učenje;ACF;konvolucijska nevronska mreža;metoda podpornih vektorjev;tlačenje nemaksimumov;računalništvo;računalništvo in informatika;univerzitetni študij;diplomske naloge;
File type:	application/pdf
Type (COBISS):	Bachelor thesis/paper
Study programme:	1000468
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za računalništvo in informatiko
Pages:	68 str.
ID:	9057138