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}
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
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: