Shape recognition in image
I need help with one application, I am a beginner in programming. So I need to create a simple application that recognizes shapes in the image (rectangle, triangle, line ...) rendering them. (for an experienced programmer to be easy :D ) Here are similar projects, but I was the only one to not know much about: http://leakingmemory.wordpress.com/2012/03/17/shape-recognition-using-c-and-aforge/ and http://www.emgu.com/wiki/index.php/Shape_(Triangle,_Rectangle,_Circle,_Line)_Detection_in_CSharp Thank you very much
EDIT: Can you tell me how to portray all the polygons? Not only a triangle, circle ... but all shapes?
Answer
If you really want to attempt this, I'd suggest looking into Edge Detection to start. Both of those articles you linked to start by processing the image and finding the edges. The first article uses a Sobel filter, whereas the second uses Canny edge detection. Once you have a better understanding of this concept, you can make use of a library like AForge to handle doing it for you.
The next step would be to write the logic that will be used to detect the vertices of joined edges that were found from the previous step. With that in place you can detect triangles (3 vertices), squares (4 vertices), or any other arbitrary polygon.
Detecting a circle seems like it would be a bit more difficult (the second article looks to "detect" a circle by removing anything that's not a circle). If you've made it to this point though, I'm sure you could do a bit of googling and find some techniques that other people use to detect circles, and you can use the code you now have as a starting point to implement it.
Good luck!