Package org.opensourcephysics.display

Class GraphicsLib

java.lang.Object
org.opensourcephysics.display.GraphicsLib
public class GraphicsLib extends Object
Library of useful computer graphics routines such as geometry routines for computing the intersection of different shapes and rendering methods for computing bounds and performing optimized drawing.
Author:
jeffrey heer

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    COINCIDENT
    Indicates intersection between shapes
    static final int
    NO_INTERSECTION
    Indicates no intersection between shapes
    static final int
    PARALLEL
    Indicates two lines are parallel

  • Constructor Summary

    Constructors
    Constructor
    Description
    GraphicsLib()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static GeneralPath
    cardinalSpline(float[] pts, float slack, boolean closed)
    Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points.
    static GeneralPath
    cardinalSpline(float[] pts, int start, int npoints, float slack, boolean closed)
    Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points.
    static GeneralPath
    cardinalSpline(GeneralPath p, float[] pts, float slack, boolean closed, float tx, float ty)
    Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points.
    static GeneralPath
    cardinalSpline(GeneralPath p, float[] pts, int start, int npoints, float slack, boolean closed, float tx, float ty)
    Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points.
    static float[]
    centroid(float[] pts, int len)
    Computes the mean, or centroid, of a set of points
    static double[]
    convexHull(double[] pts, int len)
    Computes the 2D convex hull of a set of points using Graham's scanning algorithm.
    static double[]
    convexHull(double[] pts, int len, float[] angles, int[] idx, int[] stack)
    Computes the 2D convex hull of a set of points using Graham's scanning algorithm.
    static void
    expand(Rectangle2D r, double amount)
    Expand a rectangle by the given amount.
    static void
    growPolygon(float[] pts, int len, float amt)
    Expand a polygon by adding the given distance along the line from the centroid of the polyong.
    static int
    intersectLineLine(double a1x, double a1y, double a2x, double a2y, double b1x, double b1y, double b2x, double b2y, Point2D intersect)
    Compute the intersection of two line segments.
    static int
    intersectLineLine(Line2D a, Line2D b, Point2D intersect)
    Compute the intersection of two line segments.
    static int
    intersectLineRectangle(Line2D l, Rectangle2D r, Point2D[] pts)
    Compute the intersection of a line and a rectangle.
    static int
    intersectLineRectangle(Point2D a1, Point2D a2, Rectangle2D r, Point2D[] pts)
    Compute the intersection of a line and a rectangle.
    static GeneralPath
    stackSpline(GeneralPath p, float[] pts, float epsilon, float slack, boolean closed, float tx, float ty)
    Computes a set of curves using the cardinal spline approach, but using straight lines for completely horizontal or vertical segments.
    static GeneralPath
    stackSpline(GeneralPath p, float[] pts, int start, int npoints, float epsilon, float slack, boolean closed, float tx, float ty)
    Computes a set of curves using the cardinal spline approach, but using straight lines for completely horizontal or vertical segments.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • NO_INTERSECTION

      public static final int NO_INTERSECTION
      Indicates no intersection between shapes
      See Also:

    • COINCIDENT

      public static final int COINCIDENT
      Indicates intersection between shapes
      See Also:

    • PARALLEL

      public static final int PARALLEL
      Indicates two lines are parallel
      See Also:

  • Constructor Details

    • GraphicsLib

      public GraphicsLib()

  • Method Details

    • intersectLineLine

      public static int intersectLineLine(Line2D a, Line2D b, Point2D intersect)
      Compute the intersection of two line segments.
      Parameters:
      a - the first line segment
      b - the second line segment
      intersect - a Point in which to store the intersection point
      Returns:
      the intersection code. One of NO_INTERSECTION, COINCIDENT, or PARALLEL.

    • intersectLineLine

      public static int intersectLineLine(double a1x, double a1y, double a2x, double a2y, double b1x, double b1y, double b2x, double b2y, Point2D intersect)
      Compute the intersection of two line segments.
      Parameters:
      a1x - the x-coordinate of the first endpoint of the first line
      a1y - the y-coordinate of the first endpoint of the first line
      a2x - the x-coordinate of the second endpoint of the first line
      a2y - the y-coordinate of the second endpoint of the first line
      b1x - the x-coordinate of the first endpoint of the second line
      b1y - the y-coordinate of the first endpoint of the second line
      b2x - the x-coordinate of the second endpoint of the second line
      b2y - the y-coordinate of the second endpoint of the second line
      intersect - a Point in which to store the intersection point
      Returns:
      the intersection code. One of NO_INTERSECTION, COINCIDENT, or PARALLEL.

    • intersectLineRectangle

      public static int intersectLineRectangle(Point2D a1, Point2D a2, Rectangle2D r, Point2D[] pts)
      Compute the intersection of a line and a rectangle.
      Parameters:
      a1 - the first endpoint of the line
      a2 - the second endpoint of the line
      r - the rectangle
      pts - a length 2 or greater array of points in which to store the results
      Returns:
      the intersection code. One of NO_INTERSECTION, COINCIDENT, or PARALLEL.

    • intersectLineRectangle

      public static int intersectLineRectangle(Line2D l, Rectangle2D r, Point2D[] pts)
      Compute the intersection of a line and a rectangle.
      Parameters:
      l - the line
      r - the rectangle
      pts - a length 2 or greater array of points in which to store the results
      Returns:
      the intersection code. One of NO_INTERSECTION, COINCIDENT, or PARALLEL.

    • convexHull

      public static double[] convexHull(double[] pts, int len)
      Computes the 2D convex hull of a set of points using Graham's scanning algorithm. The algorithm has been implemented as described in Cormen, Leiserson, and Rivest's Introduction to Algorithms. The running time of this algorithm is O(n log n), where n is the number of input points.
      Parameters:
      pts - the input points in [x0,y0,x1,y1,...] order
      len - the length of the pts array to consider (2 * #points)
      Returns:
      the convex hull of the input points

    • convexHull

      public static double[] convexHull(double[] pts, int len, float[] angles, int[] idx, int[] stack)
      Computes the 2D convex hull of a set of points using Graham's scanning algorithm. The algorithm has been implemented as described in Cormen, Leiserson, and Rivest's Introduction to Algorithms. The running time of this algorithm is O(n log n), where n is the number of input points.
      Parameters:
      pts -
      Returns:
      the convex hull of the input points

    • centroid

      public static float[] centroid(float[] pts, int len)
      Computes the mean, or centroid, of a set of points
      Parameters:
      pts - the points array, in x1, y1, x2, y2, ... arrangement.
      len - the length of the array to consider
      Returns:
      the centroid as a length-2 float array

    • growPolygon

      public static void growPolygon(float[] pts, int len, float amt)
      Expand a polygon by adding the given distance along the line from the centroid of the polyong.
      Parameters:
      pts - the polygon to expand, a set of points in a float array
      len - the length of the range of the array to consider
      amt - the amount by which to expand the polygon, each point will be moved this distance along the line from the centroid of the polygon to the given point.

    • cardinalSpline

      public static GeneralPath cardinalSpline(float[] pts, float slack, boolean closed)
      Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points. Cardinal splines maintain C(1) continuity, ensuring the connected spline segments form a differentiable curve, ensuring at least a minimum level of smoothness.
      Parameters:
      pts - the points to interpolate with a cardinal spline
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the cardinal spline should be closed (i.e. return to the starting point), false for an open curve
      Returns:
      the cardinal spline as a Java2D GeneralPath instance.

    • cardinalSpline

      public static GeneralPath cardinalSpline(float[] pts, int start, int npoints, float slack, boolean closed)
      Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points. Cardinal splines maintain C(1) continuity, ensuring the connected spline segments form a differentiable curve, ensuring at least a minimum level of smoothness.
      Parameters:
      pts - the points to interpolate with a cardinal spline
      start - the starting index from which to read points
      npoints - the number of points to consider
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the cardinal spline should be closed (i.e. return to the starting point), false for an open curve
      Returns:
      the cardinal spline as a Java2D GeneralPath instance.

    • cardinalSpline

      public static GeneralPath cardinalSpline(GeneralPath p, float[] pts, float slack, boolean closed, float tx, float ty)
      Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points. Cardinal splines maintain C(1) continuity, ensuring the connected spline segments form a differentiable curve, ensuring at least a minimum level of smoothness.
      Parameters:
      p - the GeneralPath instance to use to store the result
      pts - the points to interpolate with a cardinal spline
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the cardinal spline should be closed (i.e. return to the starting point), false for an open curve
      tx - a value by which to translate the curve along the x-dimension
      ty - a value by which to translate the curve along the y-dimension
      Returns:
      the cardinal spline as a Java2D GeneralPath instance.

    • cardinalSpline

      public static GeneralPath cardinalSpline(GeneralPath p, float[] pts, int start, int npoints, float slack, boolean closed, float tx, float ty)
      Compute a cardinal spline, a series of cubic Bezier splines smoothly connecting a set of points. Cardinal splines maintain C(1) continuity, ensuring the connected spline segments form a differentiable curve, ensuring at least a minimum level of smoothness.
      Parameters:
      p - the GeneralPath instance to use to store the result
      pts - the points to interpolate with a cardinal spline
      start - the starting index from which to read points
      npoints - the number of points to consider
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the cardinal spline should be closed (i.e. return to the starting point), false for an open curve
      tx - a value by which to translate the curve along the x-dimension
      ty - a value by which to translate the curve along the y-dimension
      Returns:
      the cardinal spline as a Java2D GeneralPath instance.

    • stackSpline

      public static GeneralPath stackSpline(GeneralPath p, float[] pts, float epsilon, float slack, boolean closed, float tx, float ty)
      Computes a set of curves using the cardinal spline approach, but using straight lines for completely horizontal or vertical segments.
      Parameters:
      p - the GeneralPath instance to use to store the result
      pts - the points to interpolate with the spline
      epsilon - threshold value under which to treat the difference between two values to be zero. Used to determine which segments to treat as lines rather than curves.
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the spline should be closed (i.e. return to the starting point), false for an open curve
      tx - a value by which to translate the curve along the x-dimension
      ty - a value by which to translate the curve along the y-dimension
      Returns:
      the stack spline as a Java2D GeneralPath instance.

    • stackSpline

      public static GeneralPath stackSpline(GeneralPath p, float[] pts, int start, int npoints, float epsilon, float slack, boolean closed, float tx, float ty)
      Computes a set of curves using the cardinal spline approach, but using straight lines for completely horizontal or vertical segments.
      Parameters:
      p - the GeneralPath instance to use to store the result
      pts - the points to interpolate with the spline
      start - the starting index from which to read points
      npoints - the number of points to consider
      epsilon - threshold value under which to treat the difference between two values to be zero. Used to determine which segments to treat as lines rather than curves.
      slack - a parameter controlling the "tightness" of the spline to the control points, 0.10 is a typically suitable value
      closed - true if the spline should be closed (i.e. return to the starting point), false for an open curve
      tx - a value by which to translate the curve along the x-dimension
      ty - a value by which to translate the curve along the y-dimension
      Returns:
      the stack spline as a Java2D GeneralPath instance.

    • expand

      public static void expand(Rectangle2D r, double amount)
      Expand a rectangle by the given amount.
      Parameters:
      r - the rectangle to expand
      amount - the amount by which to expand the rectangle