Class SVGRadialGradientPaint

  • All Implemented Interfaces:
    java.awt.Paint, java.awt.Transparency

    public final class SVGRadialGradientPaint
    extends SVGMultipleGradientPaint
    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 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.

    image showing the
 distance AB=BC, and AD=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.

    image showing the
 distance of AB, BC, AD, and DE 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:

    image showing the
 output of the sameple code

    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:

    image showing the
 output of the sample code

    Since:
    1.6
    See Also:
    Paint, Graphics2D.setPaint(java.awt.Paint)
    • Constructor Summary

      Constructors 
      Constructor Description
      SVGRadialGradientPaint​(@NotNull java.awt.geom.Point2D center, float radius, @NotNull java.awt.geom.Point2D focus, float focusRadius, float[] fractions, java.awt.Color[] colors, java.awt.MultipleGradientPaint.CycleMethod cycleMethod, java.awt.MultipleGradientPaint.ColorSpaceType colorSpace, @NotNull java.awt.geom.AffineTransform gradientTransform)
      Constructs a RadialGradientPaint.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.awt.PaintContext createContext​(java.awt.image.ColorModel cm, java.awt.Rectangle deviceBounds, java.awt.geom.Rectangle2D userBounds, java.awt.geom.AffineTransform transform, java.awt.RenderingHints hints)  
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • focus

        @NotNull
        private final @NotNull java.awt.geom.Point2D focus
        Focus point which defines the 0% gradient stop X coordinate.
      • center

        @NotNull
        private final @NotNull java.awt.geom.Point2D center
        Center of the circle defining the 100% gradient stop X coordinate.
      • radius

        private final float radius
        Radius of the outermost circle defining the 100% gradient stop.
      • focusRadius

        private final float focusRadius
        Radius of the innermost circle defining the circular area of the 0% gradient stop.
    • Constructor Detail

      • SVGRadialGradientPaint

        public SVGRadialGradientPaint​(@NotNull
                                      @NotNull java.awt.geom.Point2D center,
                                      float radius,
                                      @NotNull
                                      @NotNull java.awt.geom.Point2D focus,
                                      float focusRadius,
                                      float[] fractions,
                                      java.awt.Color[] colors,
                                      java.awt.MultipleGradientPaint.CycleMethod cycleMethod,
                                      java.awt.MultipleGradientPaint.ColorSpaceType colorSpace,
                                      @NotNull
                                      @NotNull java.awt.geom.AffineTransform gradientTransform)
        Constructs a RadialGradientPaint.
        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 gradient
        focus - the point in user space to which the first color is mapped
        focusRadius - the radius around the focus defining the circle in which the first color is mapped
        fractions - numbers ranging from 0.0 to 1.0 specifying the distribution of colors along the gradient
        colors - 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 - either NO_CYCLE, REFLECT, or REPEAT
        colorSpace - which color space to use for interpolation, either SRGB or LINEAR_RGB
        gradientTransform - transform to apply to the gradient
        Throws:
        java.lang.NullPointerException - if one of the points is null, or fractions array is null, or colors array is null, or cycleMethod is null, or colorSpace is null, or gradientTransform is null
        java.lang.IllegalArgumentException - if radius is non-positive, or fractions.length != colors.length, or colors is less than 2 in size, or a fractions value is less than 0.0 or greater than 1.0, or the fractions are not provided in strictly increasing order
    • Method Detail

      • createContext

        public java.awt.PaintContext createContext​(java.awt.image.ColorModel cm,
                                                   java.awt.Rectangle deviceBounds,
                                                   java.awt.geom.Rectangle2D userBounds,
                                                   java.awt.geom.AffineTransform transform,
                                                   java.awt.RenderingHints hints)