2-D edge detection using snakes Project 13 – Team 6

Snakes in general Snakes or active contours are computer-generated curves that move within images to find object boundaries. Snakes or active contours are computer-generated curves that move within images to find object boundaries.

Snakes in general Internal forces (snake attribute) Internal forces (snake attribute) Prevent streching Prevent streching Prevent bending Prevent bending External forces (picture attribute) External forces (picture attribute) Guide towards the object boundaries Guide towards the object boundaries

Traditional snake Needs to be initalized close to the object to find it Needs to be initalized close to the object to find it Can not go into concavities Can not go into concavities

Gradient Vector Flow (GVF) snake Can go into concavities Can go into concavities Can be initialized anywhere, even across boundaries Can be initialized anywhere, even across boundaries

Gradient Vector Flow (GVF) snake

The team Renáta Hodován – assistance, QA Renáta Hodován – assistance, QA Ferenc Nasztanovics – homepage Ferenc Nasztanovics – homepage Julian Stottinger – MATLAB Julian Stottinger – MATLAB István Vincze – C++ István Vincze – C++ Péter Siklós – presentation Péter Siklós – presentation

Original plan Found a semi working GVF snake in MATLAB (original program by Dejan Tomazevic) Had a working C++ GUI but without any force powers (by István Vincze) Extract the snake force features from the MATLAB program, and reimplement in C++, then add some extra fetures

The C++ program Developement of the internal snake energies Developement of the internal snake energies Improvements in GUI functionality Improvements in GUI functionality Iteration and snake movement Iteration and snake movement Calculation of snake direction Calculation of snake direction Optimalization of snake energy Optimalization of snake energy Tuning internal energies Tuning internal energies Embedding the GVF funtcion Embedding the GVF funtcion

Plan B C++ program not coming along, so: Try some features in the MATLAB program Try some features in the MATLAB program Both programs use the same function to calculate GVF, so results shouldnt be so different Both programs use the same function to calculate GVF, so results shouldnt be so different Save some time experimenting in C++ Save some time experimenting in C++

MATLAB experimentation Wanted to do a snake finding the edge of the team on a group photo

MATLAB experimentation Some holes were not accessible

MATLAB experimentation Reproduced the problem on a smaller image

MATLAB experimentation Conclusion: This problem can not be solved with the traditional GVF snake Some new energies need to be introduced, to force the snake into these kind of cavities. Readjust snake using tracing quadtrees (see presentation on thermal video processing by András Hajdu) Readjust snake using tracing quadtrees (see presentation on thermal video processing by András Hajdu) Contour optimization Contour optimization Snake area minimalization? Snake area minimalization?

MATLAB experimentation Importance of parameter tuning: Small blurHigh blur

This is an ugly formula C++ program results Team photo Lung

Thank you for your attention!