Creating a composite Shape in Java 2D

Question

Using Java 2D I've patched several Bezier curves (CubicCurve2D) together to create a "blob". The problem I now face is how to:

1. Efficiently fill the blob with a given colour.
2. Efficiently determine whether a given point lies inside the blob.

I noticed thst CubicCurve2D implements Shape which provides numerous contains methods for determining "insideness" and that Graphics2D is able to fill a Shape via the fill(Shape) (which I believe uses Shape's getPathIterator methods to do this).

Given this I was hoping I could create a composite Shape, whereby my getPathIterator(AffineTransform) method would simply link the underlying PathIterators together. However, this is producing a NoSuchElementException once my shape contains more than one CubicCurve2D. Even if I do manage to achieve this I'm not convinced it will work as expected because a CubicCurve2D is always filled on the convex side, and my "blob" is composed of concave and convex curves. The "contains" problem is even harder as a point can legitimately lie within the blob but not within any of the individual curves.

• Am I approaching this problem in the correct way (trying to implement Shape?) or is there an idiomatic way to do this that I'm unaware of? I would have thought that the problem of compositing geometric shapes would be fairly common.
• Does anyone have any suggestions regarding how to solve this problem?

Thanks in advance.

Answer 1

I'm not sure I understand your question but composite shapes can be created with the class java/awt/geom/Area.

Answer 2

Looking to Shape for a solution is the right way to go about this. If you have a collection of curves that you are trying to assemble into a shape, I would suggest that you use a GeneralPath. Simply add your curves, or straight line segments, as required. Look to the interface to see the various append methods. Also note that you can 'complete' the shape by joining the last point to the starting point.

Once the path is closed, there are a number of different versions of contains() that can be used, please take the time to read each of their descriptions, as there are trade-offs in terms of speed and accuracy, depends on your application.

Also it is easy to get a shape from the path, and fill it, transform it, etc.