Algorithm required to determine if a rectangle is completely covered by another set of rectangles

Question

I am searching for an algorithm that will determine if a new rectangle is completely covered by a set of existing rectangles. Another way of putting the question, is does the ne

Answer 1

here is my code, as you requested:

the first method "subtracts" (returns uncovered parts) of 2 rectangles.

the second method subtracts a list of rectangles from the base rectangle.

in your case list contains existing rectangles, and the new one is base

to check if there is a full intersection the list returned from the second method should have no elements.

public static List SubtractRectangles(Rectangle baseRect, Rectangle splitterRect)
    {
        List newRectaglesList = new List();

        Rectangle intersection = Rectangle.Intersect(baseRect, splitterRect);
        if (!intersection.IsEmpty)
        {
            Rectangle topRect = new Rectangle(baseRect.Left, baseRect.Top, baseRect.Width, (intersection.Top - baseRect.Top));
            Rectangle bottomRect = new Rectangle(baseRect.Left, intersection.Bottom, baseRect.Width, (baseRect.Bottom - intersection.Bottom));

            if ((topRect != intersection) && (topRect.Height != 0))
            {
                newRectaglesList.Add(topRect);
            }

            if ((bottomRect != intersection) && (bottomRect.Height != 0))
            {
                newRectaglesList.Add(bottomRect);
            }
        }
        else
        {
            newRectaglesList.Add(baseRect);
        }

        return newRectaglesList;
    }

    public static List SubtractRectangles(Rectangle baseRect, List splitterRectList)
    {
        List fragmentsList = new List();
        fragmentsList.Add(baseRect);

        foreach (Rectangle splitter in splitterRectList)
        {
            List toAddList = new List();

            foreach (Rectangle fragment in fragmentsList)
            {
                List newFragmentsList = SubtractRectangles(fragment, splitter);
                toAddList.AddRange(newFragmentsList);
            }

            if (toAddList.Count != 0)
            {
                fragmentsList.Clear();
                fragmentsList.AddRange(toAddList);
            }
        }

        return fragmentsList;
    }