path: root/libjava/classpath/javax/imageio/IIOParam.java

/* IIOParam.java --
   Copyright (C) 2004  Free Software Foundation, Inc.

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
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02110-1301 USA.

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permission to link this library with independent modules to produce an
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package javax.imageio;

import java.awt.Point;
import java.awt.Rectangle;

/**
 * An IIOParam stores parameters used when encoding or decoding image
 * streams.  ImageReadParam and ImageWriteParam extend this abstract
 * base class.
 *
 * IIOParams allow control over how source pixels converted into
 * destination pixels.  This conversion can take place between a
 * stream and in-memory image data, when an image reader is doing the
 * conversion, or a writer can be doing the conversion from an
 * in-memory source to a stream destination.
 *
 * An image reader can be restricted to only read from a given region;
 * likewise a writer can be restricted to only write output to a given
 * region.
 *
 * For image readers and writers, IIOParam supports image pixelation
 * -- where the input image is approximated by the output image using
 * larger-sized pixel blocks.  For example: FIXME
 *
 * IIOParams can control how pixels are combined into larger blocks
 * using sub-sampling matrices.  For example: FIXME
 *
 * They can also control which source bands are read and written; this
 * example reads the RGBA (red, green, blue, transparency) data from a
 * PNG image and outputs just the red and transparency bands: FIXME
 *
 * @author Thomas Fitzsimmons (fitzsim@redhat.com)
 * @author Michael Koch (konqueror@gmx.de)
 */
public abstract class IIOParam
{
  /**
   * The controller called by this IIOParam to retrieve parameters.
   */
  protected IIOParamController controller = null;

  /**
   * The default controller called by this IIOParam to retrieve
   * parameters.
   */
  protected IIOParamController defaultController = null;

  /**
   * The offset in the destination where the upper-left
   * decoded/encoded pixel should be located.
   */
  protected Point destinationOffset = new Point(0, 0);

  /**
   * Sets the output colour type when writing or the destination image
   * type when reading.
   */
  protected ImageTypeSpecifier destinationType = null;

  /**
   * An array indicating which source bands will be used or null.
   */
  protected int[] sourceBands = null;

  /**
   * The source pixel region or null.
   */
  protected Rectangle sourceRegion = null;

  /**
   * Sample every sourceXSubsampling'th pixel in the source image when
   * pixelating the destination image in the horizontal direction.
   */
  protected int sourceXSubsampling = 1;

  /**
   * Sample every sourceYSubsampling'th pixel in the source image when
   * pixelating the destination image in the vertical direction.
   */
  protected int sourceYSubsampling = 1;

  /**
   * Start sampling at this horizontal offset within the source region
   * when pixelating the destination image in the horizontal
   * direction.
   */
  protected int subsamplingXOffset = 0;

  /**
   * Start sampling at this vertical offset within the source region
   * when pixelating the destination image in the vertical direction.
   */
  protected int subsamplingYOffset = 0;

  /**
   * Indicates whether or not the controller has been explicitly set
   * to null.
   */
  private boolean no_controller = false;

  /**
   * Constructs an IIOParam object.
   */
  protected IIOParam()
  {
  }

  /**
   * Activates the parameter controller by calling its activate method
   * and passing it this IIOParam.  A true return value indicates that
   * this IIOParam's values are ready for the next read or write
   * operation.  A return value of false means that this IIOParam's
   * values have not been affected because the controller operations
   * were cancelled.
   *
   * @return true if parameters were successfully set, false if
   * parameters were not changed
   */
  public boolean activateController()
  {
    if (controller == null)
      {
	if (defaultController == null || no_controller)
	  return false;
	else
	  return defaultController.activate (this);
      }
    else
      return controller.activate(this);
  }

  /**
   * Retrieve the currently set controller if one has been set, or the
   * default controller, or null if the controller has been explicitly
   * set to null.
   *
   * @return the currently used controller or null
   */  
  public IIOParamController getController()
  {
    return controller == null ?
      (no_controller ? null : defaultController) : controller;
  }

  /**
   * Retrieve the default controller regardless of whether or not a
   * non-default controller has been set.  The default controller may
   * be null.
   *
   * @return the default controller or null
   */
  public IIOParamController getDefaultController()
  {
    return defaultController;
  }

  /**
   * Retrieve the offset in the destination where the upper-left
   * decoded/encoded pixel should be located. (0, 0) by default.
   *
   * @return the destination offset
   */
  public Point getDestinationOffset()
  {
    return destinationOffset;
  }

  /**
   * Retrieve the currently set image-type specifier or null if none
   * has been set.
   *
   * @return the current image-type specifier or null
   */
  public ImageTypeSpecifier getDestinationType()
  {
    return destinationType;
  }

  /**
   * Retrieve the current source band values or null if source band
   * values have not been set.
   *
   * The returned array is a copy of this IIOParam's source band
   * array.
   *
   * @return the current set of source band values or null
   */
  public int[] getSourceBands()
  {
    if (sourceBands == null)
      return null;

    int[] sourceBandsCopy = new int[sourceBands.length];
    System.arraycopy (sourceBands, 0, sourceBandsCopy, 0, sourceBands.length);
    return sourceBandsCopy;
  }

  /**
   * Retrieve the source rectangle from which pixels should be read or
   * null if no source region has been set.
   *
   * @return the current source region or null
   */
  public Rectangle getSourceRegion()
  {
    return sourceRegion;
  }

  /**
   * Retrieve the number of pixel columns to advance before taking a
   * pixel sample.
   *
   * @return the horizontal sub-sampling interval
   */
  public int getSourceXSubsampling()
  {
    return sourceXSubsampling;
  }
  
  /**
   * Retrieve the number of pixel rows to advance before taking a
   * pixel sample.
   *
   * @return the vertical sub-sampling interval
   */
  public int getSourceYSubsampling()
  {
    return sourceYSubsampling;
  }

  /**
   * Retrieve the number of pixel columns to advance before taking any
   * pixel samples.
   *
   * @return the horizontal sub-sampling offset
   */
  public int getSubsamplingXOffset()
  {
    return subsamplingXOffset;
  }

  /**
   * Retrieve the number of pixel rows to advance before taking any
   * pixel samples.
   *
   * @return the vertical sub-sampling offset
   */
  public int getSubsamplingYOffset()
  {
    return subsamplingYOffset;
  }

  /**
   * Check if a non-null controller is currently available.
   *
   * @return true if getController returns a non-null value, false if
   * getController returns null
   */
  public boolean hasController()
  {
    return getController() != null;
  }

  /**
   * Sets the controller for this IIOParam.  This is the controller
   * that will be activated when activateController is called.  The
   * argument controller overrides this IIOParam's default controller.
   * If the argument is null then no controller will be set, not even
   * the default one.  To reset the default controller call
   * setController(getDefaultController()).
   *
   * @param controller the controller to set or null
   */
  public void setController(IIOParamController controller)
  {
    if (controller == defaultController)
      {
	this.controller = null;
	no_controller = false;
      }
    else
      {
	no_controller = (controller == null);
	this.controller = controller;
      }
  }

  /**
   * Set the destination image type.
   *
   * If this value is set on an image reader then its read method will
   * return a new BufferedImage of the specified destination type.  In
   * this case any destination image set using setDestination() is
   * ignored.
   *
   * If this is set on an image writer then the destination type
   * affects only the colour model of the destination image.  The
   * destination type's SampleModel is ignored.  The destination
   * type's ColorModel will override the source image's colour model.
   *
   * @param destinationType the sample and colour models of the
   * destination image
   */
  public void setDestinationType (ImageTypeSpecifier destinationType)
  {
    this.destinationType = destinationType;
  }

  /**
   * Specify the destination pixel offset.  Image writers are only
   * affected by this setting when ImageWriter.replacePixels is called
   * in which case the offset is into the region of pixels being
   * changed.
   *
   * @param destinationOffset the offset where pixel writing should
   * begin
   */
  public void setDestinationOffset(Point destinationOffset)
  {
    if (destinationOffset == null)
      throw new IllegalArgumentException("destinationOffset is null");

    this.destinationOffset = destinationOffset;
  }

  /**
   * Set the indices of the source bands to be used.  Duplicate
   * indices are not allowed.  A value of null means use all source
   * bands.  The argument array is copied and stored, so subsequent
   * updates to it will not be reflected in this IIOParam.
   *
   * @param sourceBands the array of source bands to use
   */
  public void setSourceBands(int[] sourceBands)
  {
    int[] sourceBandsCopy = new int[sourceBands.length];
    System.arraycopy (sourceBands, 0, sourceBandsCopy, 0, sourceBands.length);
    this.sourceBands = sourceBandsCopy;
  }

  /**
   * Set the source region from which to read.  The number of pixels
   * sampled from the source region depends on the source sub-sampling
   * settings.  If the combination of this sourceRegion and the
   * current sub-sampling settings would result in no pixels being
   * sampled then an IllegalStateException will be thrown.
   *
   * The source region is specified in the source image coordinate
   * system which has point (0, 0) at the top-left and increases down
   * and to the right.  The argument source region is clipped to the
   * image boundaries at read-time.
   *
   * A null argument sets the source region to null meaning that the
   * whole image should be read.
   *
   * @param sourceRegion the rectangular source region
   *
   * @exception IllegalArgumentException if sourceRegion has width or
   * height <= 0 or x or y < 0
   * @exception IllegalStateException if the given sourceRegion and
   * the current sampling settings would produce zero samples
   */
  public void setSourceRegion(Rectangle sourceRegion)
  {
    if (sourceRegion != null
	&& (sourceRegion.x < 0
	    || sourceRegion.y < 0
	    || sourceRegion.width <= 0
	    || sourceRegion.height <= 0))
      throw new IllegalArgumentException("illegal source region");

    if (sourceRegion != null)
      {
	int num_rows =
	  (sourceRegion.height - subsamplingYOffset + sourceYSubsampling - 1)
	  / sourceYSubsampling;

	int num_columns =
	  (sourceRegion.width - subsamplingXOffset + sourceXSubsampling - 1)
	  / sourceXSubsampling;

	if (num_rows <= 0 || num_columns <= 0)
	  throw new IllegalStateException("zero pixels in source region");
      }

    this.sourceRegion = sourceRegion;
  }

  /**
   * Set the source sampling intervals and offsets.  Every
   * sourceXSubsampling'th pixel horizontally and
   * sourceYSubsampling'th pixel vertically will be sampled.  Sampling
   * will being a the subsamplingXOffset'th column and the
   * subsamplingYOffset'th row.
   *
   * Horizontally, the number of sampled pixels will be:
   *
   * floor((width - subsamplingXOffset + sourceXSubsampling - 1) / sourceXSubsampling)
   *
   * Vertically:
   *
   * floor((height - subsamplingYOffset + sourceYSubsampling - 1) / sourceYSubsampling)
   *
   * If the current source region setting is such that the given
   * sub-sampling arguments would produce zero pixel samples, an
   * IllegalStateException is thrown.
   *
   * The offset parameters can be used to make source regions overlap
   * when tiling across an image.  This can eliminate seams and
   * better-tile images whose width or height is not a multiple of the
   * sampling interval.
   *
   * @param sourceXSubsampling the horizontal sampling interval
   * @param sourceYSubsampling the vertical sampling interval
   * @param subsamplingXOffset the horizontal offset of the initial
   * sample
   * @param subsamplingYOffset the vertical offset of the initial
   * sample
   *
   * @exception IllegalArgumentException if either subsamplingXOffset
   * or subsamplingYOffset is < 0
   * @exception IllegalStateException if the current source region
   * combined with the given sub-sampling parameters would produce
   * zero pixel samples
   */
  public void setSourceSubsampling(int sourceXSubsampling, int sourceYSubsampling,
				   int subsamplingXOffset, int subsamplingYOffset)
  {
    if (subsamplingXOffset < 0 || subsamplingYOffset < 0)
      throw new IllegalArgumentException("subsampling offset < 0");

    if (sourceRegion != null)
      {
	int num_rows =
	  (sourceRegion.height - subsamplingYOffset + sourceYSubsampling - 1)
	  / sourceYSubsampling;

	int num_columns =
	  (sourceRegion.width - subsamplingXOffset + sourceXSubsampling - 1)
	  / sourceXSubsampling;

	if (num_rows <= 0 || num_columns <= 0)
	  throw new IllegalStateException("subsampling parameters would"
					  + " produce zero pixel samples"
					  + " in source region");
      }

    this.sourceXSubsampling = sourceXSubsampling;
    this.sourceYSubsampling = sourceYSubsampling;
    this.subsamplingXOffset = subsamplingXOffset;
    this.subsamplingYOffset = subsamplingYOffset;
  }
}