AreaAveragingScaleFilterpublic class AreaAveragingScaleFilter extends ReplicateScaleFilter | An ImageFilter class for scaling images using a simple area averaging
algorithm that produces smoother results than the nearest neighbor
algorithm.
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.
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. |
| Fields Summary |
|---|
| private static final ColorModel | rgbmodel | | private static final int | neededHints | | private boolean | passthrough | | private float[] | reds | | private float[] | greens | | private float[] | blues | | private float[] | alphas | | private int | savedy | | private int | savedyrem |
| Constructors Summary |
|---|
public AreaAveragingScaleFilter(int width, int height)Constructs an AreaAveragingScaleFilter that scales the pixels from
its source Image as specified by the width and height parameters.
super(width, height);
|
| Methods Summary |
|---|
| private void | accumPixels(int x, int y, int w, int h, java.awt.image.ColorModel model, java.lang.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;
| | 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 | makeAccumBuffers()
reds = new float[destWidth];
greens = new float[destWidth];
blues = new float[destWidth];
alphas = new float[destWidth];
| | public void | setHints(int hints)Detect if the data is being delivered with the necessary hints
to allow the averaging algorithm to do its work.
Note: This method is intended to be called by the
ImageProducer of the Image 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.
passthrough = ((hints & neededHints) != neededHints);
super.setHints(hints);
| | public void | setPixels(int x, int y, int w, int h, java.awt.image.ColorModel model, byte[] pixels, int off, int scansize)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.
Note: This method is intended to be called by the
ImageProducer of the Image
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.
if (passthrough) {
super.setPixels(x, y, w, h, model, pixels, off, scansize);
} else {
accumPixels(x, y, w, h, model, pixels, off, scansize);
}
| | public void | setPixels(int x, int y, int w, int h, java.awt.image.ColorModel model, int[] pixels, int off, int 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.
Note: This method is intended to be called by the
ImageProducer of the Image
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.
if (passthrough) {
super.setPixels(x, y, w, h, model, pixels, off, scansize);
} else {
accumPixels(x, y, w, h, model, pixels, off, scansize);
}
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