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/*
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* Copyright (c) 1996, 2002, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.awt.image;
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import java.awt.image.ImageConsumer;
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import java.awt.image.ColorModel;
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import java.util.Hashtable;
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import java.awt.Rectangle;
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/**
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* An ImageFilter class for scaling images using a simple area averaging
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* algorithm that produces smoother results than the nearest neighbor
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* algorithm.
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* <p>This class extends the basic ImageFilter Class to scale an existing
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* image and provide a source for a new image containing the resampled
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* image. The pixels in the source image are blended to produce pixels
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* for an image of the specified size. The blending process is analogous
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* to scaling up the source image to a multiple of the destination size
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* using pixel replication and then scaling it back down to the destination
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* size by simply averaging all the pixels in the supersized image that
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* fall within a given pixel of the destination image. If the data from
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* the source is not delivered in TopDownLeftRight order then the filter
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* will back off to a simple pixel replication behavior and utilize the
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* requestTopDownLeftRightResend() method to refilter the pixels in a
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* better way at the end.
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* <p>It is meant to be used in conjunction with a FilteredImageSource
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* object to produce scaled versions of existing images. Due to
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* implementation dependencies, there may be differences in pixel values
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* of an image filtered on different platforms.
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*
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* @see FilteredImageSource
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* @see ReplicateScaleFilter
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* @see ImageFilter
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*
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* @author Jim Graham
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*/
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public class AreaAveragingScaleFilter extends ReplicateScaleFilter {
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private static final ColorModel rgbmodel = ColorModel.getRGBdefault();
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private static final int neededHints = (TOPDOWNLEFTRIGHT
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| COMPLETESCANLINES);
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private boolean passthrough;
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private float reds[], greens[], blues[], alphas[];
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private int savedy;
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private int savedyrem;
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/**
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* Constructs an AreaAveragingScaleFilter that scales the pixels from
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* its source Image as specified by the width and height parameters.
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* @param width the target width to scale the image
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* @param height the target height to scale the image
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*/
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public AreaAveragingScaleFilter(int width, int height) {
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super(width, height);
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}
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/**
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* Detect if the data is being delivered with the necessary hints
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* to allow the averaging algorithm to do its work.
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* <p>
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* Note: This method is intended to be called by the
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* {@code ImageProducer} of the {@code Image} whose
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* pixels are being filtered. Developers using
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* this class to filter pixels from an image should avoid calling
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* this method directly since that operation could interfere
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* with the filtering operation.
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* @see ImageConsumer#setHints
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*/
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public void setHints(int hints) {
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passthrough = ((hints & neededHints) != neededHints);
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super.setHints(hints);
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}
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private void makeAccumBuffers() {
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reds = new float[destWidth];
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greens = new float[destWidth];
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blues = new float[destWidth];
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alphas = new float[destWidth];
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}
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private int[] calcRow() {
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float origmult = ((float) srcWidth) * srcHeight;
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if (outpixbuf == null || !(outpixbuf instanceof int[])) {
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outpixbuf = new int[destWidth];
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}
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int[] outpix = (int[]) outpixbuf;
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for (int x = 0; x < destWidth; x++) {
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float mult = origmult;
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int a = Math.round(alphas[x] / mult);
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if (a <= 0) {
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a = 0;
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} else if (a >= 255) {
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a = 255;
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} else {
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// un-premultiply the components (by modifying mult here, we
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// are effectively doing the divide by mult and divide by
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// alpha in the same step)
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mult = alphas[x] / 255;
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}
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int r = Math.round(reds[x] / mult);
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int g = Math.round(greens[x] / mult);
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int b = Math.round(blues[x] / mult);
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if (r < 0) {r = 0;} else if (r > 255) {r = 255;}
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if (g < 0) {g = 0;} else if (g > 255) {g = 255;}
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if (b < 0) {b = 0;} else if (b > 255) {b = 255;}
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outpix[x] = (a << 24 | r << 16 | g << 8 | b);
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}
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return outpix;
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}
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private void accumPixels(int x, int y, int w, int h,
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ColorModel model, Object pixels, int off,
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int scansize) {
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if (reds == null) {
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makeAccumBuffers();
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}
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int sy = y;
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int syrem = destHeight;
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int dy, dyrem;
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if (sy == 0) {
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dy = 0;
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dyrem = 0;
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} else {
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dy = savedy;
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dyrem = savedyrem;
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}
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while (sy < y + h) {
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int amty;
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if (dyrem == 0) {
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for (int i = 0; i < destWidth; i++) {
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alphas[i] = reds[i] = greens[i] = blues[i] = 0f;
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}
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dyrem = srcHeight;
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}
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if (syrem < dyrem) {
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amty = syrem;
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} else {
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amty = dyrem;
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}
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int sx = 0;
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int dx = 0;
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int sxrem = 0;
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int dxrem = srcWidth;
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float a = 0f, r = 0f, g = 0f, b = 0f;
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while (sx < w) {
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if (sxrem == 0) {
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sxrem = destWidth;
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int rgb;
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if (pixels instanceof byte[]) {
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rgb = ((byte[]) pixels)[off + sx] & 0xff;
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} else {
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rgb = ((int[]) pixels)[off + sx];
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}
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// getRGB() always returns non-premultiplied components
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rgb = model.getRGB(rgb);
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a = rgb >>> 24;
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r = (rgb >> 16) & 0xff;
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g = (rgb >> 8) & 0xff;
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b = rgb & 0xff;
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// premultiply the components if necessary
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if (a != 255.0f) {
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float ascale = a / 255.0f;
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r *= ascale;
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g *= ascale;
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b *= ascale;
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}
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}
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int amtx;
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if (sxrem < dxrem) {
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amtx = sxrem;
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} else {
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amtx = dxrem;
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}
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float mult = ((float) amtx) * amty;
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alphas[dx] += mult * a;
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reds[dx] += mult * r;
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greens[dx] += mult * g;
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blues[dx] += mult * b;
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if ((sxrem -= amtx) == 0) {
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sx++;
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}
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if ((dxrem -= amtx) == 0) {
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dx++;
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dxrem = srcWidth;
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}
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}
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if ((dyrem -= amty) == 0) {
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int outpix[] = calcRow();
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do {
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consumer.setPixels(0, dy, destWidth, 1,
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rgbmodel, outpix, 0, destWidth);
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dy++;
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} while ((syrem -= amty) >= amty && amty == srcHeight);
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} else {
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syrem -= amty;
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}
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if (syrem == 0) {
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syrem = destHeight;
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sy++;
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off += scansize;
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}
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}
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savedyrem = dyrem;
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savedy = dy;
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}
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/**
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* Combine the components for the delivered byte pixels into the
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* accumulation arrays and send on any averaged data for rows of
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* pixels that are complete. If the correct hints were not
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* specified in the setHints call then relay the work to our
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* superclass which is capable of scaling pixels regardless of
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* the delivery hints.
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* <p>
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* Note: This method is intended to be called by the
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* {@code ImageProducer} of the {@code Image}
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* whose pixels are being filtered. Developers using
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* this class to filter pixels from an image should avoid calling
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* this method directly since that operation could interfere
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* with the filtering operation.
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* @see ReplicateScaleFilter
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*/
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public void setPixels(int x, int y, int w, int h,
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ColorModel model, byte pixels[], int off,
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int scansize) {
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if (passthrough) {
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super.setPixels(x, y, w, h, model, pixels, off, scansize);
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} else {
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accumPixels(x, y, w, h, model, pixels, off, scansize);
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}
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}
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/**
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* Combine the components for the delivered int pixels into the
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* accumulation arrays and send on any averaged data for rows of
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* pixels that are complete. If the correct hints were not
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* specified in the setHints call then relay the work to our
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* superclass which is capable of scaling pixels regardless of
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* the delivery hints.
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* <p>
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* Note: This method is intended to be called by the
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* {@code ImageProducer} of the {@code Image}
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* whose pixels are being filtered. Developers using
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* this class to filter pixels from an image should avoid calling
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* this method directly since that operation could interfere
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* with the filtering operation.
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* @see ReplicateScaleFilter
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*/
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public void setPixels(int x, int y, int w, int h,
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ColorModel model, int pixels[], int off,
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int scansize) {
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if (passthrough) {
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super.setPixels(x, y, w, h, model, pixels, off, scansize);
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} else {
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accumPixels(x, y, w, h, model, pixels, off, scansize);
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}
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}
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}
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