 All Implemented Interfaces:
Paint
,Transparency
public final class RadialGradientPaint extends MultipleGradientPaint
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 inbetween 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 radius of the circle will cause the rings of the gradient pattern to be centered on the point just inside the edge of the circle in the direction of the focus point. The rendering will internally use this modified location as if it were the specified focus point.
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}this will be converted to a gradient with the following keyframes:
{Color.BLUE, Color.BLUE, Color.RED, Color.RED}, {0f, .3f, .7f, 1f}
The user may also select what action the RadialGradientPaint
object
takes when it is filling the space outside the circle's radius by
setting CycleMethod
to either REFLECTION
or REPEAT
.
The gradient color proportions are equal for any particular line drawn
from the focus point. The following figure shows that the distance AB
is equal to the distance BC, and the distance AD is equal to the distance DE.
If the gradient and graphics rendering transforms are uniformly scaled and the user sets the focus so that it coincides with the center of the circle, the gradient color proportions are equal for any line drawn from the center. The following figure shows the distances AB, BC, AD, and DE. They are all equal.
Note that some minor variations in distances may occur due to sampling at
the granularity of a pixel.
If no cycle method is specified, NO_CYCLE
will be chosen by
default, which means 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 noncentered 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 noncentered focus for each of the three cycle methods:
 Since:
 1.6
 See Also:
Paint
,Graphics2D.setPaint(java.awt.Paint)

Nested Class Summary
Nested classes/interfaces declared in class java.awt.MultipleGradientPaint
MultipleGradientPaint.ColorSpaceType, MultipleGradientPaint.CycleMethod

Field Summary

Constructor Summary
Constructors Constructor Description RadialGradientPaint(float cx, float cy, float radius, float[] fractions, Color[] colors)
Constructs aRadialGradientPaint
with a defaultNO_CYCLE
repeating method andSRGB
color space, using the center as the focus point.RadialGradientPaint(float cx, float cy, float radius, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)
Constructs aRadialGradientPaint
with a defaultSRGB
color space, using the center as the focus point.RadialGradientPaint(float cx, float cy, float radius, float fx, float fy, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)
Constructs aRadialGradientPaint
with a defaultSRGB
color space.RadialGradientPaint(Point2D center, float radius, float[] fractions, Color[] colors)
Constructs aRadialGradientPaint
with a defaultNO_CYCLE
repeating method andSRGB
color space, using the center as the focus point.RadialGradientPaint(Point2D center, float radius, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)
Constructs aRadialGradientPaint
with a defaultSRGB
color space, using the center as the focus point.RadialGradientPaint(Point2D center, float radius, Point2D focus, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)
Constructs aRadialGradientPaint
with a defaultSRGB
color space.RadialGradientPaint(Point2D center, float radius, Point2D focus, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod, MultipleGradientPaint.ColorSpaceType colorSpace, AffineTransform gradientTransform)
Constructs aRadialGradientPaint
.RadialGradientPaint(Rectangle2D gradientBounds, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)
Constructs aRadialGradientPaint
with a defaultSRGB
color space. 
Method Summary
Modifier and Type Method Description PaintContext
createContext(ColorModel cm, Rectangle deviceBounds, Rectangle2D userBounds, AffineTransform transform, RenderingHints hints)
Creates and returns aPaintContext
used to generate a circular radial color gradient pattern.Point2D
getCenterPoint()
Returns a copy of the center point of the radial gradient.Point2D
getFocusPoint()
Returns a copy of the focus point of the radial gradient.float
getRadius()
Returns the radius of the circle defining the radial gradient.Methods declared in class java.awt.MultipleGradientPaint
getColors, getColorSpace, getCycleMethod, getFractions, getTransform, getTransparency

Constructor Details

RadialGradientPaint
Constructs aRadialGradientPaint
with a defaultNO_CYCLE
repeating method andSRGB
color space, using the center as the focus point. Parameters:
cx
 the X coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.cy
 the Y coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.radius
 the radius of the circle defining the extents of the color gradientfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle. Throws:
NullPointerException
 iffractions
array is null, orcolors
array is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
Constructs aRadialGradientPaint
with a defaultNO_CYCLE
repeating method andSRGB
color space, using the center as the focus point. Parameters:
center
 the center point, in user space, of the circle defining the gradientradius
 the radius of the circle defining the extents of the color gradientfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle. Throws:
NullPointerException
 ifcenter
point is null, orfractions
array is null, orcolors
array is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
public RadialGradientPaint(float cx, float cy, float radius, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)Constructs aRadialGradientPaint
with a defaultSRGB
color space, using the center as the focus point. Parameters:
cx
 the X coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.cy
 the Y coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.radius
 the radius of the circle defining the extents of the color gradientfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
 Throws:
NullPointerException
 iffractions
array is null, orcolors
array is null, orcycleMethod
is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
public RadialGradientPaint(Point2D center, float radius, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)Constructs aRadialGradientPaint
with a defaultSRGB
color space, using the center as the focus point. Parameters:
center
 the center point, in user space, of the circle defining the gradientradius
 the radius of the circle defining the extents of the color gradientfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
 Throws:
NullPointerException
 ifcenter
point is null, orfractions
array is null, orcolors
array is null, orcycleMethod
is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
public RadialGradientPaint(float cx, float cy, float radius, float fx, float fy, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)Constructs aRadialGradientPaint
with a defaultSRGB
color space. Parameters:
cx
 the X coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.cy
 the Y coordinate in user space of the center point of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.radius
 the radius of the circle defining the extents of the color gradientfx
 the X coordinate of the point in user space to which the first color is mappedfy
 the Y coordinate of the point in user space to which the first color is mappedfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
 Throws:
NullPointerException
 iffractions
array is null, orcolors
array is null, orcycleMethod
is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
public RadialGradientPaint(Point2D center, float radius, Point2D focus, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)Constructs aRadialGradientPaint
with a defaultSRGB
color space. Parameters:
center
 the center point, in user space, of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.radius
 the radius of the circle defining the extents of the color gradientfocus
 the point in user space to which the first color is mappedfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
 Throws:
NullPointerException
 if one of the points is null, orfractions
array is null, orcolors
array is null, orcycleMethod
is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
@ConstructorProperties({"centerPoint","radius","focusPoint","fractions","colors","cycleMethod","colorSpace","transform"}) public RadialGradientPaint(Point2D center, float radius, Point2D focus, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod, MultipleGradientPaint.ColorSpaceType colorSpace, AffineTransform gradientTransform)Constructs aRadialGradientPaint
. Parameters:
center
 the center point in user space of the circle defining the gradient. The last color of the gradient is mapped to the perimeter of this circle.radius
 the radius of the circle defining the extents of the color gradientfocus
 the point in user space to which the first color is mappedfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
colorSpace
 which color space to use for interpolation, eitherSRGB
orLINEAR_RGB
gradientTransform
 transform to apply to the gradient Throws:
NullPointerException
 if one of the points is null, orfractions
array is null, orcolors
array is null, orcycleMethod
is null, orcolorSpace
is null, orgradientTransform
is nullIllegalArgumentException
 ifradius
is nonpositive, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order

RadialGradientPaint
public RadialGradientPaint(Rectangle2D gradientBounds, float[] fractions, Color[] colors, MultipleGradientPaint.CycleMethod cycleMethod)Constructs aRadialGradientPaint
with a defaultSRGB
color space. The gradient circle of theRadialGradientPaint
is defined by the given bounding box.This constructor is a more convenient way to express the following (equivalent) code:
double gw = gradientBounds.getWidth(); double gh = gradientBounds.getHeight(); double cx = gradientBounds.getCenterX(); double cy = gradientBounds.getCenterY(); Point2D center = new Point2D.Double(cx, cy); AffineTransform gradientTransform = new AffineTransform(); gradientTransform.translate(cx, cy); gradientTransform.scale(gw / 2, gh / 2); gradientTransform.translate(cx, cy); RadialGradientPaint gp = new RadialGradientPaint(center, 1.0f, center, fractions, colors, cycleMethod, ColorSpaceType.SRGB, gradientTransform);
 Parameters:
gradientBounds
 the bounding box, in user space, of the circle defining the outermost extent of the gradientfractions
 numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradientcolors
 array of colors to use in the gradient. The first color is used at the focus point, the last color around the perimeter of the circle.cycleMethod
 eitherNO_CYCLE
,REFLECT
, orREPEAT
 Throws:
NullPointerException
 ifgradientBounds
is null, orfractions
array is null, orcolors
array is null, orcycleMethod
is nullIllegalArgumentException
 ifgradientBounds
is empty, orfractions.length != colors.length
, orcolors
is less than 2 in size, or afractions
value is less than 0.0 or greater than 1.0, or thefractions
are not provided in strictly increasing order


Method Details

createContext
public PaintContext createContext(ColorModel cm, Rectangle deviceBounds, Rectangle2D userBounds, AffineTransform transform, RenderingHints hints)Creates and returns aPaintContext
used to generate a circular radial color gradient pattern. See the description of thecreateContext
method for information on null parameter handling. Parameters:
cm
 the preferredColorModel
which represents the most convenient format for the caller to receive the pixel data, ornull
if there is no preference.deviceBounds
 the device space bounding box of the graphics primitive being rendered.userBounds
 the user space bounding box of the graphics primitive being rendered.transform
 theAffineTransform
from user space into device space.hints
 the set of hints that the context object can use to choose between rendering alternatives. Returns:
 the
PaintContext
for generating color patterns.  See Also:
Paint
,PaintContext
,ColorModel
,Rectangle
,Rectangle2D
,AffineTransform
,RenderingHints

getCenterPoint
Returns a copy of the center point of the radial gradient. Returns:
 a
Point2D
object that is a copy of the center point

getFocusPoint
Returns a copy of the focus point of the radial gradient. Note that if the focus point specified when the radial gradient was constructed lies outside of the radius of the circle, this method will still return the original focus point even though the rendering may center the rings of color on a different point that lies inside the radius. Returns:
 a
Point2D
object that is a copy of the focus point

getRadius
public float getRadius()Returns the radius of the circle defining the radial gradient. Returns:
 the radius of the circle defining the radial gradient
