RadialGradientPaint

Class Overview

The RadialGradientPaint class provides a way to fill a shape with a circular radial color gradient pattern. The user may specify 2 or more gradient colors, and this paint will provide an interpolation between each color.

The user must specify the circle controlling the gradient pattern, which is described by a center point and a radius. The user can also specify a separate focus point within that circle, which controls the location of the first color of the gradient. By default the focus is set to be the center of the circle.

This paint will map the first color of the gradient to the focus point, and the last color to the perimeter of the circle, interpolating smoothly for any in-between colors specified by the user. Any line drawn from the focus point to the circumference will thus span all the gradient colors.

Specifying a focus point outside of the circle's radius will result in the focus being set to the intersection point of the focus-center line and the perimeter of the circle.

The user must provide an array of floats specifying how to distribute the colors along the gradient. These values should range from 0.0 to 1.0 and act like keyframes along the gradient (they mark where the gradient should be exactly a particular color).

In the event that the user does not set the first keyframe value equal to 0 and/or the last keyframe value equal to 1, keyframes will be created at these positions and the first and last colors will be replicated there. So, if a user specifies the following arrays to construct a gradient:

     {Color.BLUE, Color.RED}, {.3f, .7f}
 

     {Color.BLUE, Color.BLUE, Color.RED, Color.RED}, {0f, .3f, .7f, 1f}
 

The user may also select what action the RadialGradientPaint should take when filling color outside the bounds of the circle's radius. If no cycle method is specified, NO_CYCLE will be chosen by default, which means the the last keyframe color will be used to fill the remaining area.

The colorSpace parameter allows the user to specify in which colorspace the interpolation should be performed, default sRGB or linearized RGB.

The following code demonstrates typical usage of RadialGradientPaint, where the center and focus points are the same:

     Point2D center = new Point2D.Float(50, 50);
     float radius = 25;
     float[] dist = {0.0f, 0.2f, 1.0f};
     Color[] colors = {Color.RED, Color.WHITE, Color.BLUE};
     RadialGradientPaint p =
         new RadialGradientPaint(center, radius, dist, colors);
 

This image demonstrates the example code above, with default (centered) focus for each of the three cycle methods:

It is also possible to specify a non-centered focus point, as in the following code:

     Point2D center = new Point2D.Float(50, 50);
     float radius = 25;
     Point2D focus = new Point2D.Float(40, 40);
     float[] dist = {0.0f, 0.2f, 1.0f};
     Color[] colors = {Color.RED, Color.WHITE, Color.BLUE};
     RadialGradientPaint p =
         new RadialGradientPaint(center, radius, focus,
                                 dist, colors,
                                 CycleMethod.NO_CYCLE);
 

This image demonstrates the previous example code, with non-centered focus for each of the three cycle methods:

Summary

[Expand] Inherited Constants

From interface java.awt.Transparency int BITMASK Represents image data that is guaranteed to be either completely opaque, with an alpha value of 1.0, or completely transparent, with an alpha value of 0.0. int OPAQUE Represents image data that is guaranteed to be completely opaque, meaning that all pixels have an alpha value of 1.0. int TRANSLUCENT Represents image data that contains or might contain arbitrary alpha values between and including 0.0 and 1.0.

[Expand] Inherited Methods
From class java.awt.MultipleGradientPaint final MultipleGradientPaint.ColorSpaceType getColorSpace() Returns the enumerated type which specifies color space for interpolation. final Color[] getColors() Returns a copy of the array of colors used by this gradient. final MultipleGradientPaint.CycleMethod getCycleMethod() Returns the enumerated type which specifies cycling behavior. final float[] getFractions() Returns a copy of the array of floats used by this gradient to calculate color distribution. final AffineTransform getTransform() Returns a copy of the transform applied to the gradient. final int getTransparency() Returns the transparency mode for this Paint object.
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait() Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object. final void wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed. final void wait(long timeout) Causes the current thread to wait until either another thread invokes the notify() method or the notifyAll() method for this object, or a specified amount of time has elapsed.
From interface java.awt.Paint abstract PaintContext createContext(ColorModel cm, Rectangle deviceBounds, Rectangle2D userBounds, AffineTransform xform, RenderingHints hints) Creates and returns a PaintContext used to generate the color pattern.
From interface java.awt.Transparency abstract int getTransparency() Returns the type of this Transparency.