/* Copyright (C) 2004, 2006  Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package java.awt.image;

import java.awt.RenderingHints;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.Arrays;

/**
 * RescaleOp is a filter that changes each pixel by a scaling factor and offset.
 *
 * For filtering Rasters, either one scaling factor and offset can be specified,
 * which will be applied to all bands; or a scaling factor and offset can be
 * specified for each band.
 *
 * For BufferedImages, the scaling may apply to both color and alpha components.
 * If only one scaling factor is provided, or if the number of factors provided
 * equals the number of color components, the scaling is performed on all color
 * components.  Otherwise, the scaling is performed on all components including
 * alpha.  Alpha premultiplication is ignored.
 *
 * After filtering, if color conversion is necessary, the conversion happens,
 * taking alpha premultiplication into account.
 *
 * @author Jerry Quinn (jlquinn@optonline.net)
 * @author Francis Kung (fkung@redhat.com)
 */
public class RescaleOp implements BufferedImageOp, RasterOp
{
  private float[] scale;
  private float[] offsets;
  private RenderingHints hints = null;

  /**
   * Create a new RescaleOp object using the given scale factors and offsets.
   *
   * The length of the arrays must be equal to the number of bands (or number of
   * data or color components) of the raster/image that this Op will be used on,
   * otherwise an IllegalArgumentException will be thrown when calling the
   * filter method.
   *
   * @param scaleFactors an array of scale factors.
   * @param offsets an array of offsets.
   * @param hints any rendering hints to use (can be null).
   * @throws NullPointerException if the scaleFactors or offsets array is null.
   */
  public RescaleOp(float[] scaleFactors,
                   float[] offsets,
                   RenderingHints hints)
  {
    int length = Math.min(scaleFactors.length, offsets.length);

    scale = new float[length];
    System.arraycopy(scaleFactors, 0, this.scale, 0, length);

    this.offsets = new float[length];
    System.arraycopy(offsets, 0, this.offsets, 0, length);

    this.hints = hints;
  }

  /**
   * Create a new RescaleOp object using the given scale factor and offset.
   *
   * The same scale factor and offset will be used on all bands/components.
   *
   * @param scaleFactor the scale factor to use.
   * @param offset the offset to use.
   * @param hints any rendering hints to use (can be null).
   */
  public RescaleOp(float scaleFactor,
                   float offset,
                   RenderingHints hints)
  {
    scale = new float[]{ scaleFactor };
    offsets = new float[]{offset};
    this.hints = hints;
  }

  /**
   * Returns the scaling factors.  This method accepts an optional array, which
   * will be used to store the factors if not null (this avoids allocating a
   * new array).  If this array is too small to hold all the scaling factors,
   * the array will be filled and the remaining factors discarded.
   *
   * @param scaleFactors array to store the scaling factors in (can be null).
   * @return an array of scaling factors.
   */
  public final float[] getScaleFactors(float[] scaleFactors)
  {
    if (scaleFactors == null)
      scaleFactors = new float[scale.length];
    System.arraycopy(scale, 0, scaleFactors, 0, Math.min(scale.length,
                                                         scaleFactors.length));
    return scaleFactors;
  }

  /**
   * Returns the offsets.  This method accepts an optional array, which
   * will be used to store the offsets if not null (this avoids allocating a
   * new array).  If this array is too small to hold all the offsets, the array
   * will be filled and the remaining factors discarded.
   *
   * @param offsets array to store the offsets in (can be null).
   * @return an array of offsets.
   */
  public final float[] getOffsets(float[] offsets)
  {
    if (offsets == null)
      offsets = new float[this.offsets.length];
    System.arraycopy(this.offsets, 0, offsets, 0, Math.min(this.offsets.length,
                                                           offsets.length));
    return offsets;
  }

  /**
   * Returns the number of scaling factors / offsets.
   *
   * @return the number of scaling factors / offsets.
   */
  public final int getNumFactors()
  {
    return scale.length;
  }

  /* (non-Javadoc)
   * @see java.awt.image.BufferedImageOp#getRenderingHints()
   */
  public final RenderingHints getRenderingHints()
  {
    return hints;
  }

  /**
   * Converts the source image using the scale factors and offsets specified in
   * the constructor.  The resulting image is stored in the destination image if
   * one is provided; otherwise a new BufferedImage is created and returned.
   *
   * The source image cannot use an IndexColorModel, and the destination image
   * (if one is provided) must have the same size.
   *
   * If the final value of a sample is beyond the range of the color model, it
   * will be clipped to the appropriate maximum / minimum.
   *
   * @param src The source image.
   * @param dst The destination image.
   * @throws IllegalArgumentException if the rasters and/or color spaces are
   *            incompatible.
   * @return The rescaled image.
   */
  public final BufferedImage filter(BufferedImage src, BufferedImage dst)
  {
    // Initial checks
    if (scale.length != 1
        && scale.length != src.getColorModel().getNumComponents()
        && (scale.length != src.getColorModel().getNumColorComponents()))
      throw new IllegalArgumentException("Source image has wrong number of "
                                         + "bands for these scaling factors.");

    if (dst == null)
      dst = createCompatibleDestImage(src, null);
    else if (src.getHeight() != dst.getHeight()
             || src.getWidth() != dst.getWidth())
      throw new IllegalArgumentException("Source and destination images are "
                                         + "different sizes.");

    // Prepare for possible colorspace conversion
    BufferedImage dst2 = dst;
    if (dst.getColorModel().getColorSpace().getType() != src.getColorModel().getColorSpace().getType())
      dst2 = createCompatibleDestImage(src, src.getColorModel());

    // Figure out how many bands to scale
    int numBands = scale.length;
    if (scale.length == 1)
      numBands = src.getColorModel().getNumColorComponents();
    boolean[] bands = new boolean[numBands];
    // this assumes the alpha, if present, is the last band
    Arrays.fill(bands, true);

    // Perform rescaling
    filter(src.getRaster(), dst2.getRaster(), bands);

    // Copy alpha band if needed (ie if it exists and wasn't scaled)
    // NOTE: This assumes the alpha component is the last band!
    if (src.getColorModel().hasAlpha()
        && numBands == src.getColorModel().getNumColorComponents())
      {

        dst2.getRaster().setSamples(0, 0, src.getWidth(), src.getHeight(),
                                    numBands,
                                    src.getRaster().getSamples(0, 0,
                                                               src.getWidth(),
                                                               src.getHeight(),
                                                               numBands,
                                                               (int[]) null));
      }

    // Perform colorspace conversion if needed
    if (dst != dst2)
      new ColorConvertOp(hints).filter(dst2, dst);

    return dst;
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#filter(java.awt.image.Raster, java.awt.image.WritableRaster)
   */
  public final WritableRaster filter(Raster src, WritableRaster dest)
  {
    // Required sanity checks
    if (scale.length != 1 && scale.length != src.numBands)
      throw new IllegalArgumentException("Number of rasters is incompatible "
                                             + "with the number of scaling "
                                             + "factors provided.");

    if (dest == null)
      dest = src.createCompatibleWritableRaster();
    else if (src.getHeight() != dest.getHeight()
             || src.getWidth() != dest.getWidth())
      throw new IllegalArgumentException("Source and destination rasters are "
                                         + "different sizes.");
    else if (src.numBands != dest.numBands)
      throw new IllegalArgumentException("Source and destination rasters "
                                         + "are incompatible.");

    // Filter all bands
    boolean[] bands = new boolean[src.getNumBands()];
    Arrays.fill(bands, true);
    return filter(src, dest, bands);
  }

  /**
   * Perform raster-based filtering on a selected number of bands.
   *
   * The length of the bands array should equal the number of bands; a true
   * element indicates filtering should happen on the corresponding band, while
   * a false element will skip the band.
   *
   * The rasters are assumed to be compatible and non-null.
   *
   * @param src the source raster.
   * @param dest the destination raster.
   * @param bands an array indicating which bands to filter.
   * @throws NullPointerException if any parameter is null.
   * @throws ArrayIndexOutOfBoundsException if the bands array is too small.
   * @return the destination raster.
   */
  private WritableRaster filter(Raster src, WritableRaster dest, boolean[] bands)
  {
    int[] values = new int[src.getHeight() * src.getWidth()];
    float scaleFactor, offset;

    // Find max sample value, to be used for clipping later
    int[] maxValue = src.getSampleModel().getSampleSize();
    for (int i = 0; i < maxValue.length; i++)
      maxValue[i] = (int)Math.pow(2, maxValue[i]) - 1;

    // TODO: can this be optimized further?
    // Filter all samples of all requested bands
    for (int band = 0; band < bands.length; band++)
      if (bands[band])
        {
          values = src.getSamples(src.getMinX(), src.getMinY(), src.getWidth(),
                                  src.getHeight(), band, values);

          if (scale.length == 1)
            {
              scaleFactor = scale[0];
              offset = offsets[0];
            }
          else
            {
              scaleFactor = scale[band];
              offset = offsets[band];
            }

          for (int i = 0; i < values.length; i++)
            {
              values[i] = (int) (values[i] * scaleFactor + offset);

              // Clip if needed
              if (values[i] < 0)
                values[i] = 0;
              if (values[i] > maxValue[band])
                values[i] = maxValue[band];
            }

          dest.setSamples(dest.getMinX(), dest.getMinY(), dest.getWidth(),
                          dest.getHeight(), band, values);
        }

    return dest;
  }

  /*
   * (non-Javadoc)
   *
   * @see java.awt.image.BufferedImageOp#createCompatibleDestImage(java.awt.image.BufferedImage,
   *      java.awt.image.ColorModel)
   */
  public BufferedImage createCompatibleDestImage(BufferedImage src,
                                                 ColorModel dstCM)
  {
    if (dstCM == null)
      return new BufferedImage(src.getWidth(), src.getHeight(), src.getType());

    return new BufferedImage(dstCM,
                             src.getRaster().createCompatibleWritableRaster(),
                             src.isAlphaPremultiplied(), null);
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#createCompatibleDestRaster(java.awt.image.Raster)
   */
  public WritableRaster createCompatibleDestRaster(Raster src)
  {
    return src.createCompatibleWritableRaster();
  }

  /* (non-Javadoc)
   * @see java.awt.image.BufferedImageOp#getBounds2D(java.awt.image.BufferedImage)
   */
  public final Rectangle2D getBounds2D(BufferedImage src)
  {
    return src.getRaster().getBounds();
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#getBounds2D(java.awt.image.Raster)
   */
  public final Rectangle2D getBounds2D(Raster src)
  {
    return src.getBounds();
  }

  /* (non-Javadoc)
   * @see java.awt.image.BufferedImageOp#getPoint2D(java.awt.geom.Point2D, java.awt.geom.Point2D)
   */
  public final Point2D getPoint2D(Point2D src, Point2D dst)
  {
    if (dst == null)
      dst = (Point2D) src.clone();
    else
      dst.setLocation(src);

    return dst;
  }

}