/*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.awt;
import java.awt.MultipleGradientPaint.CycleMethod;
import java.awt.MultipleGradientPaint.ColorSpaceType;
import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.ColorModel;
/**
* Provides the actual implementation for the LinearGradientPaint.
* This is where the pixel processing is done.
*
* @see java.awt.LinearGradientPaint
* @see java.awt.PaintContext
* @see java.awt.Paint
* @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans
*/
final class LinearGradientPaintContext extends MultipleGradientPaintContext {
/**
* The following invariants are used to process the gradient value from
* a device space coordinate, (X, Y):
* g(X, Y) = dgdX*X + dgdY*Y + gc
*/
private float dgdX, dgdY, gc;
/**
* Constructor for LinearGradientPaintContext.
*
* @param paint the {@code LinearGradientPaint} from which this context
* is created
* @param cm {@code ColorModel} that receives
* the <code>Paint</code> data. This is used only as a hint.
* @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 t the {@code AffineTransform} from user
* space into device space (gradientTransform should be
* concatenated with this)
* @param hints the hints that the context object uses to choose
* between rendering alternatives
* @param dStart gradient start point, in user space
* @param dEnd gradient end point, in user space
* @param fractions the fractions specifying the gradient distribution
* @param colors the gradient colors
* @param cycleMethod either NO_CYCLE, REFLECT, or REPEAT
* @param colorSpace which colorspace to use for interpolation,
* either SRGB or LINEAR_RGB
*/
LinearGradientPaintContext(LinearGradientPaint paint,
ColorModel cm,
Rectangle deviceBounds,
Rectangle2D userBounds,
AffineTransform t,
RenderingHints hints,
Point2D start,
Point2D end,
float[] fractions,
Color[] colors,
CycleMethod cycleMethod,
ColorSpaceType colorSpace)
{
super(paint, cm, deviceBounds, userBounds, t, hints, fractions,
colors, cycleMethod, colorSpace);
// A given point in the raster should take on the same color as its
// projection onto the gradient vector.
// Thus, we want the projection of the current position vector
// onto the gradient vector, then normalized with respect to the
// length of the gradient vector, giving a value which can be mapped
// into the range 0-1.
// projection =
// currentVector dot gradientVector / length(gradientVector)
// normalized = projection / length(gradientVector)
float startx = (float)start.getX();
float starty = (float)start.getY();
float endx = (float)end.getX();
float endy = (float)end.getY();
float dx = endx - startx; // change in x from start to end
float dy = endy - starty; // change in y from start to end
float dSq = dx*dx + dy*dy; // total distance squared
// avoid repeated calculations by doing these divides once
float constX = dx/dSq;
float constY = dy/dSq;
// incremental change along gradient for +x
dgdX = a00*constX + a10*constY;
// incremental change along gradient for +y
dgdY = a01*constX + a11*constY;
// constant, incorporates the translation components from the matrix
gc = (a02-startx)*constX + (a12-starty)*constY;
}
/**
* Return a Raster containing the colors generated for the graphics
* operation. This is where the area is filled with colors distributed
* linearly.
*
* @param x,y,w,h the area in device space for which colors are
* generated.
*/
protected void fillRaster(int[] pixels, int off, int adjust,
int x, int y, int w, int h)
{
// current value for row gradients
float g = 0;
// used to end iteration on rows
int rowLimit = off + w;
// constant which can be pulled out of the inner loop
float initConst = (dgdX*x) + gc;
for (int i = 0; i < h; i++) { // for every row
// initialize current value to be start
g = initConst + dgdY*(y+i);
while (off < rowLimit) { // for every pixel in this row
// get the color
pixels[off++] = indexIntoGradientsArrays(g);
// incremental change in g
g += dgdX;
}
// change in off from row to row
off += adjust;
//rowlimit is width + offset
rowLimit = off + w;
}
}
}