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MultipleGradientPaintContext.java
/*
* Copyright (c) 2006, 2018, 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).
*
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package java.awt;
import java.awt.MultipleGradientPaint.CycleMethod;
import java.awt.MultipleGradientPaint.ColorSpaceType;
import java.awt.color.ColorSpace;
import java.awt.geom.AffineTransform;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.geom.Rectangle2D;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferInt;
import java.awt.image.DirectColorModel;
import java.awt.image.Raster;
import java.awt.image.SinglePixelPackedSampleModel;
import java.awt.image.WritableRaster;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.Arrays;
/**
* This is the superclass for all PaintContexts which use a multiple color
* gradient to fill in their raster. It provides the actual color
* interpolation functionality. Subclasses only have to deal with using
* the gradient to fill pixels in a raster.
*
* @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans
*/
abstract class MultipleGradientPaintContext implements PaintContext {
/**
* The PaintContext's ColorModel. This is ARGB if colors are not all
* opaque, otherwise it is RGB.
*/
protected ColorModel model;
/** Color model used if gradient colors are all opaque. */
private static ColorModel xrgbmodel =
new DirectColorModel(24, 0x00ff0000, 0x0000ff00, 0x000000ff);
/** The cached ColorModel. */
protected static ColorModel cachedModel;
/** The cached raster, which is reusable among instances. */
protected static WeakReference<Raster> cached;
/** Raster is reused whenever possible. */
protected Raster saved;
/** The method to use when painting out of the gradient bounds. */
protected CycleMethod cycleMethod;
/** The ColorSpace in which to perform the interpolation */
protected ColorSpaceType colorSpace;
/** Elements of the inverse transform matrix. */
protected float a00, a01, a10, a11, a02, a12;
/**
* This boolean specifies whether we are in simple lookup mode, where an
* input value between 0 and 1 may be used to directly index into a single
* array of gradient colors. If this boolean value is false, then we have
* to use a 2-step process where we have to determine which gradient array
* we fall into, then determine the index into that array.
*/
protected boolean isSimpleLookup;
/**
* Size of gradients array for scaling the 0-1 index when looking up
* colors the fast way.
*/
protected int fastGradientArraySize;
/**
* Array which contains the interpolated color values for each interval,
* used by calculateSingleArrayGradient(). It is protected for possible
* direct access by subclasses.
*/
protected int[] gradient;
/**
* Array of gradient arrays, one array for each interval. Used by
* calculateMultipleArrayGradient().
*/
private int[][] gradients;
/** Normalized intervals array. */
private float[] normalizedIntervals;
/** Fractions array. */
private float[] fractions;
/** Used to determine if gradient colors are all opaque. */
private int transparencyTest;
/** Color space conversion lookup tables. */
private static final int[] SRGBtoLinearRGB = new int[256];
private static final int[] LinearRGBtoSRGB = new int[256];
static {
// build the tables
for (int k = 0; k < 256; k++) {
SRGBtoLinearRGB[k] = convertSRGBtoLinearRGB(k);
LinearRGBtoSRGB[k] = convertLinearRGBtoSRGB(k);
}
}
/**
* Constant number of max colors between any 2 arbitrary colors.
* Used for creating and indexing gradients arrays.
*/
protected static final int GRADIENT_SIZE = 256;
protected static final int GRADIENT_SIZE_INDEX = GRADIENT_SIZE -1;
/**
* Maximum length of the fast single-array. If the estimated array size
* is greater than this, switch over to the slow lookup method.
* No particular reason for choosing this number, but it seems to provide
* satisfactory performance for the common case (fast lookup).
*/
private static final int MAX_GRADIENT_ARRAY_SIZE = 5000;
/**
* Constructor for MultipleGradientPaintContext superclass.
*/
protected MultipleGradientPaintContext(MultipleGradientPaint mgp,
ColorModel cm,
Rectangle deviceBounds,
Rectangle2D userBounds,
AffineTransform t,
RenderingHints hints,
float[] fractions,
Color[] colors,
CycleMethod cycleMethod,
ColorSpaceType colorSpace)
{
if (deviceBounds == null) {
throw new NullPointerException("Device bounds cannot be null");
}
if (userBounds == null) {
throw new NullPointerException("User bounds cannot be null");
}
if (t == null) {
throw new NullPointerException("Transform cannot be null");
}
if (hints == null) {
throw new NullPointerException("RenderingHints cannot be null");
}
// The inverse transform is needed to go from device to user space.
// Get all the components of the inverse transform matrix.
AffineTransform tInv;
try {
// the following assumes that the caller has copied the incoming
// transform and is not concerned about it being modified
t.invert();
tInv = t;
} catch (NoninvertibleTransformException e) {
// just use identity transform in this case; better to show
// (incorrect) results than to throw an exception and/or no-op
tInv = new AffineTransform();
}
double[] m = new double[6];
tInv.getMatrix(m);
a00 = (float)m[0];
a10 = (float)m[1];
a01 = (float)m[2];
a11 = (float)m[3];
a02 = (float)m[4];
a12 = (float)m[5];
// copy some flags
this.cycleMethod = cycleMethod;
this.colorSpace = colorSpace;
// we can avoid copying this array since we do not modify its values
this.fractions = fractions;
// note that only one of these values can ever be non-null (we either
// store the fast gradient array or the slow one, but never both
// at the same time)
int[] gradient =
(mgp.gradient != null) ? mgp.gradient.get() : null;
int[][] gradients =
(mgp.gradients != null) ? mgp.gradients.get() : null;
if (gradient == null && gradients == null) {
// we need to (re)create the appropriate values
calculateLookupData(colors);
// now cache the calculated values in the
// MultipleGradientPaint instance for future use
mgp.model = this.model;
mgp.normalizedIntervals = this.normalizedIntervals;
mgp.isSimpleLookup = this.isSimpleLookup;
if (isSimpleLookup) {
// only cache the fast array
mgp.fastGradientArraySize = this.fastGradientArraySize;
mgp.gradient = new SoftReference<int[]>(this.gradient);
} else {
// only cache the slow array
mgp.gradients = new SoftReference<int[][]>(this.gradients);
}
} else {
// use the values cached in the MultipleGradientPaint instance
this.model = mgp.model;
this.normalizedIntervals = mgp.normalizedIntervals;
this.isSimpleLookup = mgp.isSimpleLookup;
this.gradient = gradient;
this.fastGradientArraySize = mgp.fastGradientArraySize;
this.gradients = gradients;
}
}
/**
* This function is the meat of this class. It calculates an array of
* gradient colors based on an array of fractions and color values at
* those fractions.
*/
private void calculateLookupData(Color[] colors) {
Color[] normalizedColors;
if (colorSpace == ColorSpaceType.LINEAR_RGB) {
// create a new colors array
normalizedColors = new Color[colors.length];
// convert the colors using the lookup table
for (int i = 0; i < colors.length; i++) {
int argb = colors[i].getRGB();
int a = argb >>> 24;
int r = SRGBtoLinearRGB[(argb >> 16) & 0xff];
int g = SRGBtoLinearRGB[(argb >> 8) & 0xff];
int b = SRGBtoLinearRGB[(argb ) & 0xff];
normalizedColors[i] = new Color(r, g, b, a);
}
} else {
// we can just use this array by reference since we do not
// modify its values in the case of SRGB
normalizedColors = colors;
}
// this will store the intervals (distances) between gradient stops
normalizedIntervals = new float[fractions.length-1];
// convert from fractions into intervals
for (int i = 0; i < normalizedIntervals.length; i++) {
// interval distance is equal to the difference in positions
normalizedIntervals[i] = this.fractions[i+1] - this.fractions[i];
}
// initialize to be fully opaque for ANDing with colors
transparencyTest = 0xff000000;
// array of interpolation arrays
gradients = new int[normalizedIntervals.length][];
// find smallest interval
float Imin = 1;
for (int i = 0; i < normalizedIntervals.length; i++) {
Imin = (Imin > normalizedIntervals[i]) ?
normalizedIntervals[i] : Imin;
}
// Estimate the size of the entire gradients array.
// This is to prevent a tiny interval from causing the size of array
// to explode. If the estimated size is too large, break to using
// separate arrays for each interval, and using an indexing scheme at
// look-up time.
int estimatedSize = 0;
for (int i = 0; i < normalizedIntervals.length; i++) {
estimatedSize += (normalizedIntervals[i]/Imin) * GRADIENT_SIZE;
}
if (estimatedSize > MAX_GRADIENT_ARRAY_SIZE) {
// slow method
calculateMultipleArrayGradient(normalizedColors);
} else {
// fast method
calculateSingleArrayGradient(normalizedColors, Imin);
}
// use the most "economical" model
if ((transparencyTest >>> 24) == 0xff) {
model = xrgbmodel;
} else {
model = ColorModel.getRGBdefault();
}
}
/**
* FAST LOOKUP METHOD
*
* This method calculates the gradient color values and places them in a
* single int array, gradient[]. It does this by allocating space for
* each interval based on its size relative to the smallest interval in
* the array. The smallest interval is allocated 255 interpolated values
* (the maximum number of unique in-between colors in a 24 bit color
* system), and all other intervals are allocated
* size = (255 * the ratio of their size to the smallest interval).
*
* This scheme expedites a speedy retrieval because the colors are
* distributed along the array according to their user-specified
* distribution. All that is needed is a relative index from 0 to 1.
*
* The only problem with this method is that the possibility exists for
* the array size to balloon in the case where there is a
* disproportionately small gradient interval. In this case the other
* intervals will be allocated huge space, but much of that data is
* redundant. We thus need to use the space conserving scheme below.
*
* @param Imin the size of the smallest interval
*/
private void calculateSingleArrayGradient(Color[] colors, float Imin) {
// set the flag so we know later it is a simple (fast) lookup
isSimpleLookup = true;
// 2 colors to interpolate
int rgb1, rgb2;
//the eventual size of the single array
int gradientsTot = 1;
// for every interval (transition between 2 colors)
for (int i = 0; i < gradients.length; i++) {
// create an array whose size is based on the ratio to the
// smallest interval
int nGradients = (int)((normalizedIntervals[i]/Imin)*255f);
gradientsTot += nGradients;
gradients[i] = new int[nGradients];
// the 2 colors (keyframes) to interpolate between
rgb1 = colors[i].getRGB();
rgb2 = colors[i+1].getRGB();
// fill this array with the colors in between rgb1 and rgb2
interpolate(rgb1, rgb2, gradients[i]);
// if the colors are opaque, transparency should still
// be 0xff000000
transparencyTest &= rgb1;
transparencyTest &= rgb2;
}
// put all gradients in a single array
gradient = new int[gradientsTot];
int curOffset = 0;
for (int i = 0; i < gradients.length; i++){
System.arraycopy(gradients[i], 0, gradient,
curOffset, gradients[i].length);
curOffset += gradients[i].length;
}
gradient[gradient.length-1] = colors[colors.length-1].getRGB();
// if interpolation occurred in Linear RGB space, convert the
// gradients back to sRGB using the lookup table
if (colorSpace == ColorSpaceType.LINEAR_RGB) {
for (int i = 0; i < gradient.length; i++) {
gradient[i] = convertEntireColorLinearRGBtoSRGB(gradient[i]);
}
}
fastGradientArraySize = gradient.length - 1;
}
/**
* SLOW LOOKUP METHOD
*
* This method calculates the gradient color values for each interval and
* places each into its own 255 size array. The arrays are stored in
* gradients[][]. (255 is used because this is the maximum number of
* unique colors between 2 arbitrary colors in a 24 bit color system.)
*
* This method uses the minimum amount of space (only 255 * number of
* intervals), but it aggravates the lookup procedure, because now we
* have to find out which interval to select, then calculate the index
* within that interval. This causes a significant performance hit,
* because it requires this calculation be done for every point in
* the rendering loop.
*
* For those of you who are interested, this is a classic example of the
* time-space tradeoff.
*/
private void calculateMultipleArrayGradient(Color[] colors) {
// set the flag so we know later it is a non-simple lookup
isSimpleLookup = false;
// 2 colors to interpolate
int rgb1, rgb2;
// for every interval (transition between 2 colors)
for (int i = 0; i < gradients.length; i++){
// create an array of the maximum theoretical size for
// each interval
gradients[i] = new int[GRADIENT_SIZE];
// get the 2 colors
rgb1 = colors[i].getRGB();
rgb2 = colors[i+1].getRGB();
// fill this array with the colors in between rgb1 and rgb2
interpolate(rgb1, rgb2, gradients[i]);
// if the colors are opaque, transparency should still
// be 0xff000000
transparencyTest &= rgb1;
transparencyTest &= rgb2;
}
// if interpolation occurred in Linear RGB space, convert the
// gradients back to SRGB using the lookup table
if (colorSpace == ColorSpaceType.LINEAR_RGB) {
for (int j = 0; j < gradients.length; j++) {
for (int i = 0; i < gradients[j].length; i++) {
gradients[j][i] =
convertEntireColorLinearRGBtoSRGB(gradients[j][i]);
}
}
}
}
/**
* Yet another helper function. This one linearly interpolates between
* 2 colors, filling up the output array.
*
* @param rgb1 the start color
* @param rgb2 the end color
* @param output the output array of colors; must not be null
*/
private void interpolate(int rgb1, int rgb2, int[] output) {
// color components
int a1, r1, g1, b1, da, dr, dg, db;
// step between interpolated values
float stepSize = 1.0f / output.length;
// extract color components from packed integer
a1 = (rgb1 >> 24) & 0xff;
r1 = (rgb1 >> 16) & 0xff;
g1 = (rgb1 >> 8) & 0xff;
b1 = (rgb1 ) & 0xff;
// calculate the total change in alpha, red, green, blue
da = ((rgb2 >> 24) & 0xff) - a1;
dr = ((rgb2 >> 16) & 0xff) - r1;
dg = ((rgb2 >> 8) & 0xff) - g1;
db = ((rgb2 ) & 0xff) - b1;
// for each step in the interval calculate the in-between color by
// multiplying the normalized current position by the total color
// change (0.5 is added to prevent truncation round-off error)
for (int i = 0; i < output.length; i++) {
output[i] =
(((int) ((a1 + i * da * stepSize) + 0.5) << 24)) |
(((int) ((r1 + i * dr * stepSize) + 0.5) << 16)) |
(((int) ((g1 + i * dg * stepSize) + 0.5) << 8)) |
(((int) ((b1 + i * db * stepSize) + 0.5) ));
}
}
/**
* Yet another helper function. This one extracts the color components
* of an integer RGB triple, converts them from LinearRGB to SRGB, then
* recompacts them into an int.
*/
private int convertEntireColorLinearRGBtoSRGB(int rgb) {
// color components
int a1, r1, g1, b1;
// extract red, green, blue components
a1 = (rgb >> 24) & 0xff;
r1 = (rgb >> 16) & 0xff;
g1 = (rgb >> 8) & 0xff;
b1 = (rgb ) & 0xff;
// use the lookup table
r1 = LinearRGBtoSRGB[r1];
g1 = LinearRGBtoSRGB[g1];
b1 = LinearRGBtoSRGB[b1];
// re-compact the components
return ((a1 << 24) |
(r1 << 16) |
(g1 << 8) |
(b1 ));
}
/**
* Helper function to index into the gradients array. This is necessary
* because each interval has an array of colors with uniform size 255.
* However, the color intervals are not necessarily of uniform length, so
* a conversion is required.
*
* @param position the unmanipulated position, which will be mapped
* into the range 0 to 1
* @return integer color to display
*/
protected final int indexIntoGradientsArrays(float position) {
// first, manipulate position value depending on the cycle method
if (cycleMethod == CycleMethod.NO_CYCLE) {
if (position > 1) {
// upper bound is 1
position = 1;
} else if (position < 0) {
// lower bound is 0
position = 0;
}
} else if (cycleMethod == CycleMethod.REPEAT) {
// get the fractional part
// (modulo behavior discards integer component)
position = position - (int)position;
//position should now be between -1 and 1
if (position < 0) {
// force it to be in the range 0-1
position = position + 1;
}
} else { // cycleMethod == CycleMethod.REFLECT
if (position < 0) {
// take absolute value
position = -position;
}
// get the integer part
int part = (int)position;
// get the fractional part
position = position - part;
if ((part & 1) == 1) {
// integer part is odd, get reflected color instead
position = 1 - position;
}
}
// now, get the color based on this 0-1 position...
if (isSimpleLookup) {
// easy to compute: just scale index by array size
return gradient[(int)(position * fastGradientArraySize)];
} else {
// more complicated computation, to save space
// for all the gradient interval arrays
for (int i = 0; i < gradients.length; i++) {
if (position < fractions[i+1]) {
// this is the array we want
float delta = position - fractions[i];
// this is the interval we want
int index = (int)((delta / normalizedIntervals[i])
* (GRADIENT_SIZE_INDEX));
return gradients[i][index];
}
}
}
return gradients[gradients.length - 1][GRADIENT_SIZE_INDEX];
}
/**
* Helper function to convert a color component in sRGB space to linear
* RGB space. Used to build a static lookup table.
*/
private static int convertSRGBtoLinearRGB(int color) {
float input, output;
input = color / 255.0f;
if (input <= 0.04045f) {
output = input / 12.92f;
} else {
output = (float)Math.pow((input + 0.055) / 1.055, 2.4);
}
return Math.round(output * 255.0f);
}
/**
* Helper function to convert a color component in linear RGB space to
* SRGB space. Used to build a static lookup table.
*/
private static int convertLinearRGBtoSRGB(int color) {
float input, output;
input = color/255.0f;
if (input <= 0.0031308) {
output = input * 12.92f;
} else {
output = (1.055f *
((float) Math.pow(input, (1.0 / 2.4)))) - 0.055f;
}
return Math.round(output * 255.0f);
}
/**
* {@inheritDoc}
*/
public final Raster getRaster(int x, int y, int w, int h) {
// If working raster is big enough, reuse it. Otherwise,
// build a large enough new one.
Raster raster = saved;
if (raster == null ||
raster.getWidth() < w || raster.getHeight() < h)
{
raster = getCachedRaster(model, w, h);
saved = raster;
}
// Access raster internal int array. Because we use a DirectColorModel,
// we know the DataBuffer is of type DataBufferInt and the SampleModel
// is SinglePixelPackedSampleModel.
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