java.awt.geom

Implemented Interfaces:
Cloneable, Shape
Known Direct Subclasses:

extends Object
implements Shape, Cloneable

A two-dimensional curve that is parameterized with a quadratic function.

Since:
1.2

Nested Class Summary

static class
A two-dimensional curve that is parameterized with a quadratic function and stores coordinate values in double-precision floating-point format.
static class
A two-dimensional curve that is parameterized with a quadratic function and stores coordinate values in single-precision floating-point format.

Method Summary

Object
clone()
Creates a new curve with the same contents as this one.
boolean
contains(double x, double y)
Determines whether a point is inside the area bounded by the curve and the straight line connecting its end points.
boolean
contains(double x, double y, double w, double h)
Determines whether a rectangle is entirely inside the area bounded by the curve and the straight line connecting its end points.
boolean
contains(Point2D p)
Determines whether a point is inside the area bounded by the curve and the straight line connecting its end points.
boolean
contains(Rectangle2D r)
Determines whether a Rectangle2D is entirely inside the area that is bounded by the curve and the straight line connecting its end points.
Rectangle
getBounds()
Determines the smallest rectangle that encloses the curve’s start, end and control point.
abstract Point2D
getCtrlPt()
Returns the curve’s control point.
abstract double
getCtrlX()
Returns the x coordinate of the curve’s control point.
abstract double
getCtrlY()
Returns the y coordinate of the curve’s control point.
double
getFlatness()
Calculates the flatness of this curve.
static double
getFlatness(double x1, double y1, double cx, double cy, double x2, double y2)
Calculates the flatness of a quadratic curve, directly specifying each coordinate value.
static double
getFlatness(double[] coords, int offset)
Calculates the flatness of a quadratic curve, specifying the coordinate values in an array.
double
getFlatnessSq()
Calculates the squared flatness of this curve.
static double
getFlatnessSq(double x1, double y1, double cx, double cy, double x2, double y2)
Calculates the squared flatness of a quadratic curve, directly specifying each coordinate value.
static double
getFlatnessSq(double[] coords, int offset)
Calculates the squared flatness of a quadratic curve, specifying the coordinate values in an array.
abstract Point2D
getP1()
Returns the curve’s start point.
abstract Point2D
getP2()
Returns the curve’s end point.
PathIterator
getPathIterator(AffineTransform at)
Return an iterator along the shape boundary.
PathIterator
getPathIterator(AffineTransform at, double flatness)
Return an iterator along the flattened version of the shape boundary.
abstract double
getX1()
Returns the x coordinate of the curve’s start point.
abstract double
getX2()
Returns the x coordinate of the curve’s end point.
abstract double
getY1()
Returns the y coordinate of the curve’s start point.
abstract double
getY2()
Returns the y coordinate of the curve’s end point.
boolean
intersects(double x, double y, double w, double h)
Determines whether any part of a rectangle is inside the area bounded by the curve and the straight line connecting its end points.
boolean
intersects(Rectangle2D r)
Determines whether any part of a Rectangle2D is inside the area bounded by the curve and the straight line connecting its end points.
abstract void
setCurve(double x1, double y1, double cx, double cy, double x2, double y2)
Changes the curve geometry, separately specifying each coordinate value.
void
setCurve(double[] coords, int offset)
Changes the curve geometry, passing coordinate values in an array.
void
setCurve(Point2D p1, Point2D c, Point2D p2)
Changes the curve geometry, specifying coordinate values in separate Point objects.
void
setCurve(Point2D[] pts, int offset)
Changes the curve geometry, specifying coordinate values in an array of Point objects.
void
Changes the geometry of the curve to that of another curve.
static int
Finds the non-complex roots of a quadratic equation, placing the results into the same array as the equation coefficients.
static int
Finds the non-complex roots of a quadratic equation.
static void
subdivide(double[] src, int srcOff, double[] left, int leftOff, double[] right, int rightOff)
Subdivides a quadratic curve into two halves, passing all coordinates in an array.
void
Subdivides this curve into two halves.
static void
Subdivides a quadratic curve into two halves.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Constructs a new QuadCurve2D. Typical users will want to construct instances of a subclass, such as QuadCurve2D.Float or QuadCurve2D.Double.

Method Details

clone

public Object clone()
Creates a new curve with the same contents as this one.
Overrides:
clone in interface Object
Returns:
the clone.

contains

public boolean contains(double x,
double y)
Determines whether a point is inside the area bounded by the curve and the straight line connecting its end points.

The above drawing illustrates in which area points are considered “inside” a QuadCurve2D.

Specified by:
contains in interface Shape

contains

public boolean contains(double x,
double y,
double w,
double h)
Determines whether a rectangle is entirely inside the area bounded by the curve and the straight line connecting its end points.

The above drawing illustrates in which area points are considered “inside” a QuadCurve2D.

Specified by:
contains in interface Shape

contains

public boolean contains(Point2D p)
Determines whether a point is inside the area bounded by the curve and the straight line connecting its end points.

The above drawing illustrates in which area points are considered “inside” a QuadCurve2D.

Specified by:
contains in interface Shape

contains

public boolean contains(Rectangle2D r)
Determines whether a Rectangle2D is entirely inside the area that is bounded by the curve and the straight line connecting its end points.
Specified by:
contains in interface Shape

getBounds

public Rectangle getBounds()
Determines the smallest rectangle that encloses the curve’s start, end and control point. As the illustration below shows, the invisible control point may cause the bounds to be much larger than the area that is actually covered by the curve.

Specified by:
getBounds in interface Shape

getCtrlPt

public abstract Point2D getCtrlPt()
Returns the curve’s control point.

getCtrlX

public abstract double getCtrlX()
Returns the x coordinate of the curve’s control point.

getCtrlY

public abstract double getCtrlY()
Returns the y coordinate of the curve’s control point.

getFlatness

public double getFlatness()
Calculates the flatness of this curve. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the distance between C and the gray line, i.e. the length of the red line.

getFlatness

public static double getFlatness(double x1,
double y1,
double cx,
double cy,
double x2,
double y2)
Calculates the flatness of a quadratic curve, directly specifying each coordinate value. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the distance between C and the gray line, i.e. the length of the red line.

Parameters:
x1 - the x coordinate of the start point P1.
y1 - the y coordinate of the start point P1.
cx - the x coordinate of the control point C.
cy - the y coordinate of the control point C.
x2 - the x coordinate of the end point P2.
y2 - the y coordinate of the end point P2.

getFlatness

public static double getFlatness(double[] coords,
int offset)
Calculates the flatness of a quadratic curve, specifying the coordinate values in an array. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the the distance between C and the gray line, i.e. the length of the red line.

Parameters:
coords - an array containing the coordinate values. The x coordinate of the start point P1 is located at coords[offset], its y coordinate at coords[offset + 1]. The x coordinate of the control point C is located at coords[offset + 2], its y coordinate at coords[offset + 3]. The x coordinate of the end point P2 is located at coords[offset + 4], its y coordinate at coords[offset + 5].
offset - the offset of the first coordinate value in coords.

getFlatnessSq

public double getFlatnessSq()
Calculates the squared flatness of this curve. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the square of the distance between C and the gray line, i.e. the squared length of the red line.

getFlatnessSq

public static double getFlatnessSq(double x1,
double y1,
double cx,
double cy,
double x2,
double y2)
Calculates the squared flatness of a quadratic curve, directly specifying each coordinate value. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the square of the distance between C and the gray line, i.e. the squared length of the red line.

Parameters:
x1 - the x coordinate of the start point P1.
y1 - the y coordinate of the start point P1.
cx - the x coordinate of the control point C.
cy - the y coordinate of the control point C.
x2 - the x coordinate of the end point P2.
y2 - the y coordinate of the end point P2.

getFlatnessSq

public static double getFlatnessSq(double[] coords,
int offset)
Calculates the squared flatness of a quadratic curve, specifying the coordinate values in an array. The flatness is the distance of the control point to the line between start and end point.

In the above drawing, the straight line connecting start point P1 and end point P2 is depicted in gray. The result will be the the square of the distance between C and the gray line, i.e. the squared length of the red line.

Parameters:
coords - an array containing the coordinate values. The x coordinate of the start point P1 is located at coords[offset], its y coordinate at coords[offset + 1]. The x coordinate of the control point C is located at coords[offset + 2], its y coordinate at coords[offset + 3]. The x coordinate of the end point P2 is located at coords[offset + 4], its y coordinate at coords[offset + 5].
offset - the offset of the first coordinate value in coords.

getP1

public abstract Point2D getP1()
Returns the curve’s start point.

getP2

public abstract Point2D getP2()
Returns the curve’s end point.

getPathIterator

public PathIterator getPathIterator(AffineTransform at)
Return an iterator along the shape boundary. If the optional transform is provided, the iterator is transformed accordingly. Each call returns a new object, independent from others in use. It is recommended, but not required, that the Shape isolate iterations from future changes to the boundary, and document this fact.
Specified by:
getPathIterator in interface Shape
Parameters:
Returns:
a new iterator over the boundary
Since:
1.2

getPathIterator

public PathIterator getPathIterator(AffineTransform at,
double flatness)
Return an iterator along the flattened version of the shape boundary. Only SEG_MOVETO, SEG_LINETO, and SEG_CLOSE points are returned in the iterator. The flatness parameter controls how far points are allowed to differ from the real curve; although a limit on accuracy may cause this parameter to be enlarged if needed.

If the optional transform is provided, the iterator is transformed accordingly. Each call returns a new object, independent from others in use. It is recommended, but not required, that the Shape isolate iterations from future changes to the boundary, and document this fact.

Specified by:
getPathIterator in interface Shape
Parameters:
flatness - the maximum distance for deviation from the real boundary
Returns:
a new iterator over the boundary
Since:
1.2

getX1

public abstract double getX1()
Returns the x coordinate of the curve’s start point.

getX2

public abstract double getX2()
Returns the x coordinate of the curve’s end point.

getY1

public abstract double getY1()
Returns the y coordinate of the curve’s start point.

getY2

public abstract double getY2()
Returns the y coordinate of the curve’s end point.

intersects

public boolean intersects(double x,
double y,
double w,
double h)
Determines whether any part of a rectangle is inside the area bounded by the curve and the straight line connecting its end points.

The above drawing illustrates in which area points are considered “inside” in a CubicCurve2D.

Specified by:
intersects in interface Shape

intersects

public boolean intersects(Rectangle2D r)
Determines whether any part of a Rectangle2D is inside the area bounded by the curve and the straight line connecting its end points.
Specified by:
intersects in interface Shape

setCurve

public abstract void setCurve(double x1,
double y1,
double cx,
double cy,
double x2,
double y2)
Changes the curve geometry, separately specifying each coordinate value.
Parameters:
x1 - the x coordinate of the curve’s new start point.
y1 - the y coordinate of the curve’s new start point.
cx - the x coordinate of the curve’s new control point.
cy - the y coordinate of the curve’s new control point.
x2 - the x coordinate of the curve’s new end point.
y2 - the y coordinate of the curve’s new end point.

setCurve

public void setCurve(double[] coords,
int offset)
Changes the curve geometry, passing coordinate values in an array.
Parameters:
coords - an array containing the new coordinate values. The x coordinate of the new start point is located at coords[offset], its y coordinate at coords[offset + 1]. The x coordinate of the new control point is located at coords[offset + 2], its y coordinate at coords[offset + 3]. The x coordinate of the new end point is located at coords[offset + 4], its y coordinate at coords[offset + 5].
offset - the offset of the first coordinate value in coords.

setCurve

public void setCurve(Point2D p1,
Point2D c,
Point2D p2)
Changes the curve geometry, specifying coordinate values in separate Point objects.

The curve does not keep any reference to the passed point objects. Therefore, a later change to p1, c p2 will not affect the curve geometry.

Parameters:
p1 - the new start point.
c - the new control point.
p2 - the new end point.

setCurve

public void setCurve(Point2D[] pts,
int offset)
Changes the curve geometry, specifying coordinate values in an array of Point objects.

The curve does not keep references to the passed point objects. Therefore, a later change to the pts array or any of its elements will not affect the curve geometry.

Parameters:
pts - an array containing the points. The new start point is located at pts[offset], the new control point at pts[offset + 1], and the new end point at pts[offset + 2].
offset - the offset of the start point in pts.

setCurve

Changes the geometry of the curve to that of another curve.
Parameters:
c - the curve whose coordinates will be copied.

Finds the non-complex roots of a quadratic equation, placing the results into the same array as the equation coefficients. The following equation is being solved:
eqn[2] · x2 + eqn[1] · x + eqn[0] = 0

For some background about solving quadratic equations, see the article “Quadratic Formula” in PlanetMath. For an extensive library of numerical algorithms written in the C programming language, see the GNU Scientific Library.

Parameters:
eqn - an array with the coefficients of the equation. When this procedure has returned, eqn will contain the non-complex solutions of the equation, in no particular order.
Returns:
the number of non-complex solutions. A result of 0 indicates that the equation has no non-complex solutions. A result of -1 indicates that the equation is constant (i.e., always or never zero).

double[] res)
Finds the non-complex roots of a quadratic equation. The following equation is being solved:
eqn[2] · x2 + eqn[1] · x + eqn[0] = 0

For some background about solving quadratic equations, see the article “Quadratic Formula” in PlanetMath. For an extensive library of numerical algorithms written in the C programming language, see the GNU Scientific Library.

Parameters:
eqn - an array with the coefficients of the equation.
res - an array into which the non-complex roots will be stored. The results may be in an arbitrary order. It is safe to pass the same array object reference for both eqn and res.
Returns:
the number of non-complex solutions. A result of 0 indicates that the equation has no non-complex solutions. A result of -1 indicates that the equation is constant (i.e., always or never zero).

subdivide

public static void subdivide(double[] src,
int srcOff,
double[] left,
int leftOff,
double[] right,
int rightOff)
Subdivides a quadratic curve into two halves, passing all coordinates in an array.

The left end point and the right start point will always be identical. Memory-concious programmers thus may want to pass the same array for both left and right, and set rightOff to leftOff + 4.

Parameters:
src - an array containing the coordinates of the curve to be subdivided. The x coordinate of the start point is located at src[srcOff], its y at src[srcOff + 1]. The x coordinate of the control point is located at src[srcOff + 2], its y at src[srcOff + 3]. The x coordinate of the end point is located at src[srcOff + 4], its y at src[srcOff + 5].
srcOff - an offset into src, specifying the index of the start point’s x coordinate.
left - an array that will receive the coordinates of the left half of src. It is acceptable to pass src. A caller who is not interested in the left half can pass null.
leftOff - an offset into left, specifying the index where the start point’s x coordinate will be stored.
right - an array that will receive the coordinates of the right half of src. It is acceptable to pass src or left. A caller who is not interested in the right half can pass null.
rightOff - an offset into right, specifying the index where the start point’s x coordinate will be stored.

subdivide

Subdivides this curve into two halves.

Parameters:
left - a curve whose geometry will be set to the left half of this curve, or null if the caller is not interested in the left half.
right - a curve whose geometry will be set to the right half of this curve, or null if the caller is not interested in the right half.