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* accompanied this code).
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package java.awt.image;
import java.awt.image.ImageConsumer;
import java.awt.image.ColorModel;
import java.util.Hashtable;
import java.awt.Rectangle;
/**
* An ImageFilter class for scaling images using a simple area averaging
* algorithm that produces smoother results than the nearest neighbor
* algorithm.
* <p>This class extends the basic ImageFilter Class to scale an existing
* image and provide a source for a new image containing the resampled
* image. The pixels in the source image are blended to produce pixels
* for an image of the specified size. The blending process is analogous
* to scaling up the source image to a multiple of the destination size
* using pixel replication and then scaling it back down to the destination
* size by simply averaging all the pixels in the supersized image that
* fall within a given pixel of the destination image. If the data from
* the source is not delivered in TopDownLeftRight order then the filter
* will back off to a simple pixel replication behavior and utilize the
* requestTopDownLeftRightResend() method to refilter the pixels in a
* better way at the end.
* <p>It is meant to be used in conjunction with a FilteredImageSource
* object to produce scaled versions of existing images. Due to
* implementation dependencies, there may be differences in pixel values
* of an image filtered on different platforms.
*
* @see FilteredImageSource
* @see ReplicateScaleFilter
* @see ImageFilter
*
* @author Jim Graham
*/
public class AreaAveragingScaleFilter extends ReplicateScaleFilter {
private static final ColorModel rgbmodel = ColorModel.getRGBdefault();
private static final int neededHints = (TOPDOWNLEFTRIGHT
| COMPLETESCANLINES);
private boolean passthrough;
private float reds[], greens[], blues[], alphas[];
private int savedy;
private int savedyrem;
/**
* Constructs an AreaAveragingScaleFilter that scales the pixels from
* its source Image as specified by the width and height parameters.
* @param width the target width to scale the image
* @param height the target height to scale the image
*/
public AreaAveragingScaleFilter(int width, int height) {
super(width, height);
}
/**
* Detect if the data is being delivered with the necessary hints
* to allow the averaging algorithm to do its work.
* <p>
* Note: This method is intended to be called by the
* <code>ImageProducer</code> of the <code>Image</code> whose
* pixels are being filtered. Developers using
* this class to filter pixels from an image should avoid calling
* this method directly since that operation could interfere
* with the filtering operation.
* @see ImageConsumer#setHints
*/
public void setHints(int hints) {
passthrough = ((hints & neededHints) != neededHints);
super.setHints(hints);
}
private void makeAccumBuffers() {
reds = new float[destWidth];
greens = new float[destWidth];
blues = new float[destWidth];
alphas = new float[destWidth];
}
private int[] calcRow() {
float origmult = ((float) srcWidth) * srcHeight;
if (outpixbuf == null || !(outpixbuf instanceof int[])) {
outpixbuf = new int[destWidth];
}
int[] outpix = (int[]) outpixbuf;
for (int x = 0; x < destWidth; x++) {
float mult = origmult;
int a = Math.round(alphas[x] / mult);
if (a <= 0) {
a = 0;
} else if (a >= 255) {
a = 255;
} else {
// un-premultiply the components (by modifying mult here, we
// are effectively doing the divide by mult and divide by
// alpha in the same step)
mult = alphas[x] / 255;
}
int r = Math.round(reds[x] / mult);
int g = Math.round(greens[x] / mult);
int b = Math.round(blues[x] / mult);
if (r < 0) {r = 0;} else if (r > 255) {r = 255;}
if (g < 0) {g = 0;} else if (g > 255) {g = 255;}
if (b < 0) {b = 0;} else if (b > 255) {b = 255;}
outpix[x] = (a << 24 | r << 16 | g << 8 | b);
}
return outpix;
}
private void accumPixels(int x, int y, int w, int h,
ColorModel model, Object pixels, int off,
int scansize) {
if (reds == null) {
makeAccumBuffers();
}
int sy = y;
int syrem = destHeight;
int dy, dyrem;
if (sy == 0) {
dy = 0;
dyrem = 0;
} else {
dy = savedy;
dyrem = savedyrem;
}
while (sy < y + h) {
int amty;
if (dyrem == 0) {
for (int i = 0; i < destWidth; i++) {
alphas[i] = reds[i] = greens[i] = blues[i] = 0f;
}
dyrem = srcHeight;
}
if (syrem < dyrem) {
amty = syrem;
} else {
amty = dyrem;
}
int sx = 0;
int dx = 0;
int sxrem = 0;
int dxrem = srcWidth;
float a = 0f, r = 0f, g = 0f, b = 0f;
while (sx < w) {
if (sxrem == 0) {
sxrem = destWidth;
int rgb;
if (pixels instanceof byte[]) {
rgb = ((byte[]) pixels)[off + sx] & 0xff;
} else {
rgb = ((int[]) pixels)[off + sx];
}
// getRGB() always returns non-premultiplied components
rgb = model.getRGB(rgb);
a = rgb >>> 24;
r = (rgb >> 16) & 0xff;
g = (rgb >> 8) & 0xff;
b = rgb & 0xff;
// premultiply the components if necessary
if (a != 255.0f) {
float ascale = a / 255.0f;
r *= ascale;
g *= ascale;
b *= ascale;
}
}
int amtx;
if (sxrem < dxrem) {
amtx = sxrem;
} else {
amtx = dxrem;
}
float mult = ((float) amtx) * amty;
alphas[dx] += mult * a;
reds[dx] += mult * r;
greens[dx] += mult * g;
blues[dx] += mult * b;
if ((sxrem -= amtx) == 0) {
sx++;
}
if ((dxrem -= amtx) == 0) {
dx++;
dxrem = srcWidth;
}
}
if ((dyrem -= amty) == 0) {
int outpix[] = calcRow();
do {
consumer.setPixels(0, dy, destWidth, 1,
rgbmodel, outpix, 0, destWidth);
dy++;
} while ((syrem -= amty) >= amty && amty == srcHeight);
} else {
syrem -= amty;
}
if (syrem == 0) {
syrem = destHeight;
sy++;
off += scansize;
}
}
savedyrem = dyrem;
savedy = dy;
}
/**
* Combine the components for the delivered byte pixels into the
* accumulation arrays and send on any averaged data for rows of
* pixels that are complete. If the correct hints were not
* specified in the setHints call then relay the work to our
* superclass which is capable of scaling pixels regardless of
* the delivery hints.
* <p>
* Note: This method is intended to be called by the
* <code>ImageProducer</code> of the <code>Image</code>
* whose pixels are being filtered. Developers using
* this class to filter pixels from an image should avoid calling
* this method directly since that operation could interfere
* with the filtering operation.
* @see ReplicateScaleFilter
*/
public void setPixels(int x, int y, int w, int h,
ColorModel model, byte pixels[], int off,
int scansize) {
if (passthrough) {
super.setPixels(x, y, w, h, model, pixels, off, scansize);
} else {
accumPixels(x, y, w, h, model, pixels, off, scansize);
}
}
/**
* Combine the components for the delivered int pixels into the
* accumulation arrays and send on any averaged data for rows of
* pixels that are complete. If the correct hints were not
* specified in the setHints call then relay the work to our
* superclass which is capable of scaling pixels regardless of
* the delivery hints.
* <p>
* Note: This method is intended to be called by the
* <code>ImageProducer</code> of the <code>Image</code>
* whose pixels are being filtered. Developers using
* this class to filter pixels from an image should avoid calling
* this method directly since that operation could interfere
* with the filtering operation.
* @see ReplicateScaleFilter
*/
public void setPixels(int x, int y, int w, int h,
ColorModel model, int pixels[], int off,
int scansize) {
if (passthrough) {
super.setPixels(x, y, w, h, model, pixels, off, scansize);
} else {
accumPixels(x, y, w, h, model, pixels, off, scansize);
}
}
}