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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.
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.
Author:
     Jim Graham
See Also:
FilteredImageSource
ReplicateScaleFilter
ImageFilter/**
 * 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.
Params:
width – the target width to scale the image
height – the target height to scale the image/**
     * 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.
 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. 
See Also:
ImageConsumer.setHints/**
     * 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} of the {@code 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.
     * @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.
 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. 
See Also:
ReplicateScaleFilter/**
     * 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} of the {@code 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.
     * @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.
 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. 
See Also:
ReplicateScaleFilter/**
     * 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} of the {@code 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.
     * @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);
        }
    }
}