Hello and welcome back. Active contours, also called snakes, are very important in image and video processing. They appear in a number of commercial products and they are very useful for numerous image and video segmentation. Let me illustrate the basic concept behind active contours. The idea is that you start from one or multiple curves. For example, I'm going to draw a curve that surrounds the flower, which is my object of interest. And the basic idea behind active contours is to design velocities that will move this curve towards the flower. Hopefully, as the curve moves, it's going to end up in the border of the flower. So, we need basically to design velocities that will move any initial contour towards the contour of interest, which is the boundary of the object of interest. Now, I can write down, the formulation for this and the equations for this, but I think it's better if we first learn the material that is coming next week, as a back ground, and that will help us to write this in a much, much elegan, form. So, this week, instead of writing down the exact weight of active counters, I'm going to just illustrate you some examples to motivate you and get you very excited to learn the background, material that we're going to learn next week. So, let's go and watch some movies with examples of active contour, inside the image processing online package and inside Adobe's Photoshop. So, let's just observe that right now. In order to illustrate one of the examples of active contours, we're going to be using, again, the image processing online website where, as we have seen before, there is many very interesting image processing algorithms implemented. And particularly, now, we are in the Chan-Vese webpage, which is an implementation of one of the approaches for active contours developed by Tony Chan and Luminita Vese. Before we show you one of the examples running actually in real time, let's just basically run the demo provided by the author of this website. So here, we see contours evolving. This is a very clear example of a contour evolving towards the segment. Here, we have another one, just look at this one. And here, we see once again, how contours are evolving and yet once again. So, that's a basic idea of active contour. This was a very fast video, just to illustrate one of the examples. But let's just run one, so we're going to have more time, to look at it. Wwe're going to run the demo online as we have done in the past for other algorithms. I'm going to pick this, example, it's just one example, I'm not going to change the parameters, we don't know exactly since we haven't discussed the technique, what this parameter means, so I'm going to just, leave the default and I'm going to run it. Remember, now is rhyming as we see here, but it's rhyming in the server wrap that is provided by the imaging processing online. The algorithm is actually much, much faster, than we can see, it actually can be run on real time, but it's run on the server. And here is the result. We see once again, the initial contours, these intial contours at the very beginning are the initial contours and then, we see the boundaries. The curves have evolved toward those boundaries. The curves have evolved to segment out the object of interest. There are some spurious objects and we are going to understand why they happen, but mostly, it has done a great job basically, in finding the boundary of the flower, which is probably the object of interest for this image. And we see once again, these contours evolving. And this is, as I say, something that we're going to learn next week. Exactly the formulas, exactly the math behind it. But this illustrates the idea. Thank you for this part of the video. It's now time to illustrate using Adobe Photoshop one implementation of active contours. In particular, we're going to be using this tool in active contours that is a selection tool and look what's going to happen. Please observe my mouse. Look how I'm moving the mouse and the contours are being automatically attracted to the boundary of the flower. You know, how I just clicked and it's basically catching the flower. I almost didn't move my mouse, I just click inside the object of interest, and we capture the flower. Let me do that again here. I'm going to just click and it's capturing this part of the flower. So, you see how we can help, and we have already learned about user interaction by doing a few clicks inside the flower. Basically, a technique related to active contours, move my clicks towards the boundaries of the object of interest. This is a very, very interesting technique, this time, implemented inside Adobe Photoshop. And this provides in our demo of active contour type of approaches. Thank you. These examples that we just saw should motivate you for the material that is coming next week. Before we go into that, we have a couple of additional and very, very exciting things to learn about video segmentation. So, I see you in the next video. Thank you.
