Texture contours........

I am trying to create an application much like a drawing program. What i want to do is to draw a loop on a document, check to see if that loop is closed. For example say you want to texture a particular area on a 3d map, i want to draw on a 2d document were i want certain textures, save the points, check to see if the loops drawn are closed loops eg like texture contours if you like. Textures will be able to overlap and i intend to use some sort of blending.