How to copy Path2D?

Question

Is there a way to copy Path2D to a region / other instance of path2D?

A simple example (I'm looking for something that will work in the general case, when the paths may include squares or cubes and may or may not be singular):

I have a line segment (0.10) → (30.10) that I would like to copy inside the triangle (10,0), (20,20), (20,0), a perfect line segment (15,10 ) → (20.10)

I can convert Path2D to an area using the "new area (Shape)"; and then the clip using "Area.intersect (area)", but this will return an empty area if the path is not closed.

I can crop the drawing area using "Graphics2D.clip (Shape)", but I want to have a returned shape (there are times when I want to do further operations before the actual rendering)

After processing the API documentation, I cannot find anything to do with this. Did I miss something?

Answer 1

The reason you cannot copy the path using the region is because the Path2D object has a region of zero. The width of the path is undefined. The Area class is intended for use with objects with an area.

You can crop the drawing because you have determined the stroke width, which is used to define the path area.

So, if you want to copy the path, you need to create the laid out shape from the path using Stroke.createStrokedShape (Shape)

Here is an example:

public static void main(String[] args) throws IOException {

    String imgFormat = "PNG";

    Path2D path = new Path2D.Double();
    BasicStroke pathStroke = 
        new BasicStroke( 2 );


    // Create the path to be clipped:       
    int pathPoints[] = { 0, 10, 30, 10 };
    path.moveTo( pathPoints[ 0 ], pathPoints[1] );
    for( int i = 2; i < pathPoints.length; i+=2 ) {
        path.lineTo( pathPoints[ i ], pathPoints[ i+1 ] );
    }
    // Create the shape representing the clip area
    Polygon clipShape = new Polygon();
    int triPoints[] = { 10, 0, 20, 20, 20, 0 };
    for( int i = 0; i < triPoints.length; i+=2 ) {
        clipShape.addPoint( triPoints[i], triPoints[i+1] );
    }
    // Create the path with area using the stroke
    Shape clippedPath = pathStroke.createStrokedShape( path );

    // Apply a scale so the image is easier to see
    int scale = 10;
    AffineTransform at = AffineTransform.getScaleInstance( scale, scale );
    Shape sPath = at.createTransformedShape( path );
    Shape sClip = at.createTransformedShape( clipShape );

    // Create the Area shape that represents the path that is clipped by the clipShape
    Area clipArea = new Area( sClip );
    clipArea.intersect( new Area( at.createTransformedShape( clippedPath ) ) );


    int bbox = 10;
    Rectangle rect = sPath.getBounds();
    rect.add( sClip.getBounds() );
    // Expand the drawing area      
    rect.width += bbox;
    rect.height += bbox;
    rect.x -= bbox/2;
    rect.y -= bbox/2;
    BufferedImage img = new BufferedImage( rect.width, rect.height, BufferedImage.TYPE_INT_ARGB  );
    Graphics2D g2 = img.createGraphics();

    g2.setStroke( pathStroke );
    g2.setColor( Color.black );
    g2.draw( sPath );

    g2.setColor( Color.red );
    g2.draw( sClip );

    g2.setColor( Color.green );
    g2.draw( clipArea );

    g2.finalize();

    File img1 = new File( "/tmp/img1.png" );
    ImageIO.write( img, imgFormat, img1 );
}