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/*
* Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.awt;
import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.ColorModel;
import java.beans.ConstructorProperties;
/**
* The {@code LinearGradientPaint} class provides a way to fill
* a {@link java.awt.Shape} with a linear color gradient pattern. The user
* may specify two or more gradient colors, and this paint will provide an
* interpolation between each color. The user also specifies start and end
* points which define where in user space the color gradient should begin
* and end.
* <p>
* 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).
* <p>
* 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:<br>
* <pre>
* {Color.BLUE, Color.RED}, {.3f, .7f}
* </pre>
* this will be converted to a gradient with the following keyframes:<br>
* <pre>
* {Color.BLUE, Color.BLUE, Color.RED, Color.RED}, {0f, .3f, .7f, 1f}
* </pre>
*
* <p>
* The user may also select what action the {@code LinearGradientPaint} object
* takes when it is filling the space outside the start and end points by
* setting {@code CycleMethod} to either {@code REFLECTION} or {@code REPEAT}.
* The distances between any two colors in any of the reflected or repeated
* copies of the gradient are the same as the distance between those same two
* colors between the start and end points.
* Note that some minor variations in distances may occur due to sampling at
* the granularity of a pixel.
* If no cycle method is specified, {@code NO_CYCLE} will be chosen by
* default, which means the endpoint colors will be used to fill the
* remaining area.
* <p>
* The colorSpace parameter allows the user to specify in which colorspace
* the interpolation should be performed, default sRGB or linearized RGB.
*
* <p>
* The following code demonstrates typical usage of
* {@code LinearGradientPaint}:
* <pre>
* Point2D start = new Point2D.Float(0, 0);
* Point2D end = new Point2D.Float(50, 50);
* float[] dist = {0.0f, 0.2f, 1.0f};
* Color[] colors = {Color.RED, Color.WHITE, Color.BLUE};
* LinearGradientPaint p =
* new LinearGradientPaint(start, end, dist, colors);
* </pre>
* <p>
* This code will create a {@code LinearGradientPaint} which interpolates
* between red and white for the first 20% of the gradient and between white
* and blue for the remaining 80%.
*
* <p>
* This image demonstrates the example code above for each
* of the three cycle methods:
* <center>
* <img src = "doc-files/LinearGradientPaint.png"
* alt="image showing the output of the example code">
* </center>
*
* @see java.awt.Paint
* @see java.awt.Graphics2D#setPaint
* @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans
* @since 1.6
*/
public final class LinearGradientPaint extends MultipleGradientPaint {
/** Gradient start and end points. */
private final Point2D start, end;
/**
* Constructs a {@code LinearGradientPaint} with a default
* {@code NO_CYCLE} repeating method and {@code SRGB} color space.
*
* @param startX the X coordinate of the gradient axis start point
* in user space
* @param startY the Y coordinate of the gradient axis start point
* in user space
* @param endX the X coordinate of the gradient axis end point
* in user space
* @param endY the Y coordinate of the gradient axis end point
* in user space
* @param fractions numbers ranging from 0.0 to 1.0 specifying the
* distribution of colors along the gradient
* @param colors array of colors corresponding to each fractional value
*
* @throws NullPointerException
* if {@code fractions} array is null,
* or {@code colors} array is null,
* @throws IllegalArgumentException
* if start and end points are the same points,
* or {@code fractions.length != colors.length},
* or {@code colors} is less than 2 in size,
* or a {@code fractions} value is less than 0.0 or greater than 1.0,
* or the {@code fractions} are not provided in strictly increasing order
*/
public LinearGradientPaint(float startX, float startY,
float endX, float endY,
float[] fractions, Color[] colors)
{
this(new Point2D.Float(startX, startY),
new Point2D.Float(endX, endY),
fractions,
colors,
CycleMethod.NO_CYCLE);
}
/**
* Constructs a {@code LinearGradientPaint} with a default {@code SRGB}
* color space.
*
* @param startX the X coordinate of the gradient axis start point
* in user space
* @param startY the Y coordinate of the gradient axis start point
* in user space
* @param endX the X coordinate of the gradient axis end point
* in user space
* @param endY the Y coordinate of the gradient axis end point
* in user space
* @param fractions numbers ranging from 0.0 to 1.0 specifying the
* distribution of colors along the gradient
* @param colors array of colors corresponding to each fractional value
* @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT},
* or {@code REPEAT}
*
* @throws NullPointerException
* if {@code fractions} array is null,
* or {@code colors} array is null,
* or {@code cycleMethod} is null
* @throws IllegalArgumentException
* if start and end points are the same points,
* or {@code fractions.length != colors.length},
* or {@code colors} is less than 2 in size,
* or a {@code fractions} value is less than 0.0 or greater than 1.0,
* or the {@code fractions} are not provided in strictly increasing order
*/
public LinearGradientPaint(float startX, float startY,
float endX, float endY,
float[] fractions, Color[] colors,
CycleMethod cycleMethod)
{
this(new Point2D.Float(startX, startY),
new Point2D.Float(endX, endY),
fractions,
colors,
cycleMethod);
}
/**
* Constructs a {@code LinearGradientPaint} with a default
* {@code NO_CYCLE} repeating method and {@code SRGB} color space.
*
* @param start the gradient axis start {@code Point2D} in user space
* @param end the gradient axis end {@code Point2D} in user space
* @param fractions numbers ranging from 0.0 to 1.0 specifying the
* distribution of colors along the gradient
* @param colors array of colors corresponding to each fractional value
*
* @throws NullPointerException
* if one of the points is null,
* or {@code fractions} array is null,
* or {@code colors} array is null
* @throws IllegalArgumentException
* if start and end points are the same points,
* or {@code fractions.length != colors.length},
* or {@code colors} is less than 2 in size,
* or a {@code fractions} value is less than 0.0 or greater than 1.0,
* or the {@code fractions} are not provided in strictly increasing order
*/
public LinearGradientPaint(Point2D start, Point2D end,
float[] fractions, Color[] colors)
{
this(start, end,
fractions, colors,
CycleMethod.NO_CYCLE);
}
/**
* Constructs a {@code LinearGradientPaint} with a default {@code SRGB}
* color space.
*
* @param start the gradient axis start {@code Point2D} in user space
* @param end the gradient axis end {@code Point2D} in user space
* @param fractions numbers ranging from 0.0 to 1.0 specifying the
* distribution of colors along the gradient
* @param colors array of colors corresponding to each fractional value
* @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT},
* or {@code REPEAT}
*
* @throws NullPointerException
* if one of the points is null,
* or {@code fractions} array is null,
* or {@code colors} array is null,
* or {@code cycleMethod} is null
* @throws IllegalArgumentException
* if start and end points are the same points,
* or {@code fractions.length != colors.length},
* or {@code colors} is less than 2 in size,
* or a {@code fractions} value is less than 0.0 or greater than 1.0,
* or the {@code fractions} are not provided in strictly increasing order
*/
public LinearGradientPaint(Point2D start, Point2D end,
float[] fractions, Color[] colors,
CycleMethod cycleMethod)
{
this(start, end,
fractions, colors,
cycleMethod,
ColorSpaceType.SRGB,
new AffineTransform());
}
/**
* Constructs a {@code LinearGradientPaint}.
*
* @param start the gradient axis start {@code Point2D} in user space
* @param end the gradient axis end {@code Point2D} in user space
* @param fractions numbers ranging from 0.0 to 1.0 specifying the
* distribution of colors along the gradient
* @param colors array of colors corresponding to each fractional value
* @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT},
* or {@code REPEAT}
* @param colorSpace which color space to use for interpolation,
* either {@code SRGB} or {@code LINEAR_RGB}
* @param gradientTransform transform to apply to the gradient
*
* @throws NullPointerException
* if one of the points is null,
* or {@code fractions} array is null,
* or {@code colors} array is null,
* or {@code cycleMethod} is null,
* or {@code colorSpace} is null,
* or {@code gradientTransform} is null
* @throws IllegalArgumentException
* if start and end points are the same points,
* or {@code fractions.length != colors.length},
* or {@code colors} is less than 2 in size,
* or a {@code fractions} value is less than 0.0 or greater than 1.0,
* or the {@code fractions} are not provided in strictly increasing order
*/
@ConstructorProperties({ "startPoint", "endPoint", "fractions", "colors", "cycleMethod", "colorSpace", "transform" })
public LinearGradientPaint(Point2D start, Point2D end,
float[] fractions, Color[] colors,
CycleMethod cycleMethod,
ColorSpaceType colorSpace,
AffineTransform gradientTransform)
{
super(fractions, colors, cycleMethod, colorSpace, gradientTransform);
// check input parameters
if (start == null || end == null) {
throw new NullPointerException("Start and end points must be" +
"non-null");
}
if (start.equals(end)) {
throw new IllegalArgumentException("Start point cannot equal" +
"endpoint");
}
// copy the points...
this.start = new Point2D.Double(start.getX(), start.getY());
this.end = new Point2D.Double(end.getX(), end.getY());
}
/**
* Creates and returns a {@link PaintContext} used to
* generate a linear color gradient pattern.
* See the {@link Paint#createContext specification} of the
* method in the {@link Paint} interface for information
* on null parameter handling.
*
* @param cm the preferred {@link ColorModel} which represents the most convenient
* format for the caller to receive the pixel data, or {@code null}
* if there is no preference.
* @param deviceBounds the device space bounding box
* of the graphics primitive being rendered.
* @param userBounds the user space bounding box
* of the graphics primitive being rendered.
* @param transform the {@link AffineTransform} from user
* space into device space.
* @param hints the set of hints that the context object can use to
* choose between rendering alternatives.
* @return the {@code PaintContext} for
* generating color patterns.
* @see Paint
* @see PaintContext
* @see ColorModel
* @see Rectangle
* @see Rectangle2D
* @see AffineTransform
* @see RenderingHints
*/
public PaintContext createContext(ColorModel cm,
Rectangle deviceBounds,
Rectangle2D userBounds,
AffineTransform transform,
RenderingHints hints)
{
// avoid modifying the user's transform...
transform = new AffineTransform(transform);
// incorporate the gradient transform
transform.concatenate(gradientTransform);
if ((fractions.length == 2) &&
(cycleMethod != CycleMethod.REPEAT) &&
(colorSpace == ColorSpaceType.SRGB))
{
// faster to use the basic GradientPaintContext for this
// common case
boolean cyclic = (cycleMethod != CycleMethod.NO_CYCLE);
return new GradientPaintContext(cm, start, end,
transform,
colors[0], colors[1],
cyclic);
} else {
return new LinearGradientPaintContext(this, cm,
deviceBounds, userBounds,
transform, hints,
start, end,
fractions, colors,
cycleMethod, colorSpace);
}
}
/**
* Returns a copy of the start point of the gradient axis.
*
* @return a {@code Point2D} object that is a copy of the point
* that anchors the first color of this {@code LinearGradientPaint}
*/
public Point2D getStartPoint() {
return new Point2D.Double(start.getX(), start.getY());
}
/**
* Returns a copy of the end point of the gradient axis.
*
* @return a {@code Point2D} object that is a copy of the point
* that anchors the last color of this {@code LinearGradientPaint}
*/
public Point2D getEndPoint() {
return new Point2D.Double(end.getX(), end.getY());
}
}