ImageReadParam.java

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package javax.imageio;

import java.awt.Dimension;
import java.awt.image.BufferedImage;

/**
 * A class describing how a stream is to be decoded.  Instances of
 * this class or its subclasses are used to supply prescriptive
 * "how-to" information to instances of <code>ImageReader</code>.
 *
 * <p> An image encoded as part of a file or stream may be thought of
 * extending out in multiple dimensions: the spatial dimensions of
 * width and height, a number of bands, and a number of progressive
 * decoding passes.  This class allows a contiguous (hyper)rectangular
 * subarea of the image in all of these dimensions to be selected for
 * decoding.  Additionally, the spatial dimensions may be subsampled
 * discontinuously.  Finally, color and format conversions may be
 * specified by controlling the <code>ColorModel</code> and
 * <code>SampleModel</code> of the destination image, either by
 * providing a <code>BufferedImage</code> or by using an
 * <code>ImageTypeSpecifier</code>.
 *
 * <p> An <code>ImageReadParam</code> object is used to specify how an
 * image, or a set of images, will be converted on input from
 * a stream in the context of the Java Image I/O framework.  A plug-in for a
 * specific image format will return instances of
 * <code>ImageReadParam</code> from the
 * <code>getDefaultReadParam</code> method of its
 * <code>ImageReader</code> implementation.
 *
 * <p> The state maintained by an instance of
 * <code>ImageReadParam</code> is independent of any particular image
 * being decoded.  When actual decoding takes place, the values set in
 * the read param are combined with the actual properties of the image
 * being decoded from the stream and the destination
 * <code>BufferedImage</code> that will receive the decoded pixel
 * data.  For example, the source region set using
 * <code>setSourceRegion</code> will first be intersected with the
 * actual valid source area.  The result will be translated by the
 * value returned by <code>getDestinationOffset</code>, and the
 * resulting rectangle intersected with the actual valid destination
 * area to yield the destination area that will be written.
 *
 * <p> The parameters specified by an <code>ImageReadParam</code> are
 * applied to an image as follows.  First, if a rendering size has
 * been set by <code>setSourceRenderSize</code>, the entire decoded
 * image is rendered at the size given by
 * <code>getSourceRenderSize</code>.  Otherwise, the image has its
 * natural size given by <code>ImageReader.getWidth</code> and
 * <code>ImageReader.getHeight</code>.
 *
 * <p> Next, the image is clipped against the source region
 * specified by <code>getSourceXOffset</code>, <code>getSourceYOffset</code>,
 * <code>getSourceWidth</code>, and <code>getSourceHeight</code>.
 *
 * <p> The resulting region is then subsampled according to the
 * factors given in {@link IIOParam#setSourceSubsampling
 * IIOParam.setSourceSubsampling}.  The first pixel,
 * the number of pixels per row, and the number of rows all depend
 * on the subsampling settings.
 * Call the minimum X and Y coordinates of the resulting rectangle
 * (<code>minX</code>, <code>minY</code>), its width <code>w</code>
 * and its height <code>h</code>.
 *
 * <p> This rectangle is offset by
 * (<code>getDestinationOffset().x</code>,
 * <code>getDestinationOffset().y</code>) and clipped against the
 * destination bounds.  If no destination image has been set, the
 * destination is defined to have a width of
 * <code>getDestinationOffset().x</code> + <code>w</code>, and a
 * height of <code>getDestinationOffset().y</code> + <code>h</code> so
 * that all pixels of the source region may be written to the
 * destination.
 *
 * <p> Pixels that land, after subsampling, within the destination
 * image, and that are written in one of the progressive passes
 * specified by <code>getSourceMinProgressivePass</code> and
 * <code>getSourceNumProgressivePasses</code> are passed along to the
 * next step.
 *
 * <p> Finally, the source samples of each pixel are mapped into
 * destination bands according to the algorithm described in the
 * comment for <code>setDestinationBands</code>.
 *
 * <p> Plug-in writers may extend the functionality of
 * <code>ImageReadParam</code> by providing a subclass that implements
 * additional, plug-in specific interfaces.  It is up to the plug-in
 * to document what interfaces are available and how they are to be
 * used.  Readers will silently ignore any extended features of an
 * <code>ImageReadParam</code> subclass of which they are not aware.
 * Also, they may ignore any optional features that they normally
 * disable when creating their own <code>ImageReadParam</code>
 * instances via <code>getDefaultReadParam</code>.
 *
 * <p> Note that unless a query method exists for a capability, it must
 * be supported by all <code>ImageReader</code> implementations
 * (<i>e.g.</i> source render size is optional, but subsampling must be
 * supported).
 *
 *
 * @see ImageReader
 * @see ImageWriter
 * @see ImageWriteParam
 */
public class ImageReadParam extends IIOParam {

    /**
     * <code>true</code> if this <code>ImageReadParam</code> allows
     * the source rendering dimensions to be set.  By default, the
     * value is <code>false</code>.  Subclasses must set this value
     * manually.
     *
     * <p> <code>ImageReader</code>s that do not support setting of
     * the source render size should set this value to
     * <code>false</code>.
     */
    protected boolean canSetSourceRenderSize = false;

    /**
     * The desired rendering width and height of the source, if
     * <code>canSetSourceRenderSize</code> is <code>true</code>, or
     * <code>null</code>.
     *
     * <p> <code>ImageReader</code>s that do not support setting of
     * the source render size may ignore this value.
     */
    protected Dimension sourceRenderSize = null;

    /**
     * The current destination <code>BufferedImage</code>, or
     * <code>null</code> if none has been set.  By default, the value
     * is <code>null</code>.
     */
    protected BufferedImage destination = null;

    /**
     * The set of destination bands to be used, as an array of
     * <code>int</code>s.  By default, the value is <code>null</code>,
     * indicating all destination bands should be written in order.
     */
    protected int[] destinationBands = null;

    /**
     * The minimum index of a progressive pass to read from the
     * source.  By default, the value is set to 0, which indicates
     * that passes starting with the first available pass should be
     * decoded.
     *
     * <p> Subclasses should ensure that this value is
     * non-negative.
     */
    protected int minProgressivePass = 0;

    /**
     * The maximum number of progressive passes to read from the
     * source.  By default, the value is set to
     * <code>Integer.MAX_VALUE</code>, which indicates that passes up
     * to and including the last available pass should be decoded.
     *
     * <p> Subclasses should ensure that this value is positive.
     * Additionally, if the value is not
     * <code>Integer.MAX_VALUE</code>, then <code>minProgressivePass +
     * numProgressivePasses - 1</code> should not exceed
     * <code>Integer.MAX_VALUE</code>.
     */
    protected int numProgressivePasses = Integer.MAX_VALUE;

    /**
     * Constructs an <code>ImageReadParam</code>.
     */
    public ImageReadParam() {}

    // Comment inherited
    public void setDestinationType(ImageTypeSpecifier destinationType) {
        super.setDestinationType(destinationType);
        setDestination(null);
    }

    /**
     * Supplies a <code>BufferedImage</code> to be used as the
     * destination for decoded pixel data.  The currently set image
     * will be written to by the <code>read</code>,
     * <code>readAll</code>, and <code>readRaster</code> methods, and
     * a reference to it will be returned by those methods.
     *
     * <p> Pixel data from the aforementioned methods will be written
     * starting at the offset specified by
     * <code>getDestinationOffset</code>.
     *
     * <p> If <code>destination</code> is <code>null</code>, a
     * newly-created <code>BufferedImage</code> will be returned by
     * those methods.
     *
     * <p> At the time of reading, the image is checked to verify that
     * its <code>ColorModel</code> and <code>SampleModel</code>
     * correspond to one of the <code>ImageTypeSpecifier</code>s
     * returned from the <code>ImageReader</code>'s
     * <code>getImageTypes</code> method.  If it does not, the reader
     * will throw an <code>IIOException</code>.
     *
     * @param destination the BufferedImage to be written to, or
     * <code>null</code>.
     *
     * @see #getDestination
     */
    public void setDestination(BufferedImage destination) {
        this.destination = destination;
    }

    /**
     * Returns the <code>BufferedImage</code> currently set by the
     * <code>setDestination</code> method, or <code>null</code>
     * if none is set.
     *
     * @return the BufferedImage to be written to.
     *
     * @see #setDestination
     */
    public BufferedImage getDestination() {
        return destination;
    }

    /**
     * Sets the indices of the destination bands where data
     * will be placed.  Duplicate indices are not allowed.
     *
     * <p> A <code>null</code> value indicates that all destination
     * bands will be used.
     *
     * <p> Choosing a destination band subset will not affect the
     * number of bands in the output image of a read if no destination
     * image is specified; the created destination image will still
     * have the same number of bands as if this method had never been
     * called.  If a different number of bands in the destination
     * image is desired, an image must be supplied using the
     * <code>ImageReadParam.setDestination</code> method.
     *
     * <p> At the time of reading or writing, an
     * <code>IllegalArgumentException</code> will be thrown by the
     * reader or writer if a value larger than the largest destination
     * band index has been specified, or if the number of source bands
     * and destination bands to be used differ.  The
     * <code>ImageReader.checkReadParamBandSettings</code> method may
     * be used to automate this test.
     *
     * @param destinationBands an array of integer band indices to be
     * used.
     *
     * @exception IllegalArgumentException if <code>destinationBands</code>
     * contains a negative or duplicate value.
     *
     * @see #getDestinationBands
     * @see #getSourceBands
     * @see ImageReader#checkReadParamBandSettings
     */
    public void setDestinationBands(int[] destinationBands) {
        if (destinationBands == null) {
            this.destinationBands = null;
        } else {
            int numBands = destinationBands.length;
            for (int i = 0; i < numBands; i++) {
                int band = destinationBands[i];
                if (band < 0) {
                    throw new IllegalArgumentException("Band value < 0!");
                }
                for (int j = i + 1; j < numBands; j++) {
                    if (band == destinationBands[j]) {
                        throw new IllegalArgumentException("Duplicate band value!");
                    }
                }
            }
            this.destinationBands = (int[])destinationBands.clone();
        }
    }

    /**
     * Returns the set of band indices where data will be placed.
     * If no value has been set, <code>null</code> is returned to
     * indicate that all destination bands will be used.
     *
     * @return the indices of the destination bands to be used,
     * or <code>null</code>.
     *
     * @see #setDestinationBands
     */
    public int[] getDestinationBands() {
        if (destinationBands == null) {
            return null;
        } else {
            return (int[])(destinationBands.clone());
        }
    }

    /**
     * Returns <code>true</code> if this reader allows the source
     * image to be rendered at an arbitrary size as part of the
     * decoding process, by means of the
     * <code>setSourceRenderSize</code> method.  If this method
     * returns <code>false</code>, calls to
     * <code>setSourceRenderSize</code> will throw an
     * <code>UnsupportedOperationException</code>.
     *
     * @return <code>true</code> if setting source rendering size is
     * supported.
     *
     * @see #setSourceRenderSize
     */
    public boolean canSetSourceRenderSize() {
        return canSetSourceRenderSize;
    }

    /**
     * If the image is able to be rendered at an arbitrary size, sets
     * the source width and height to the supplied values.  Note that
     * the values returned from the <code>getWidth</code> and
     * <code>getHeight</code> methods on <code>ImageReader</code> are
     * not affected by this method; they will continue to return the
     * default size for the image.  Similarly, if the image is also
     * tiled the tile width and height are given in terms of the default
     * size.
     *
     * <p> Typically, the width and height should be chosen such that
     * the ratio of width to height closely approximates the aspect
     * ratio of the image, as returned from
     * <code>ImageReader.getAspectRatio</code>.
     *
     * <p> If this plug-in does not allow the rendering size to be
     * set, an <code>UnsupportedOperationException</code> will be
     * thrown.
     *
     * <p> To remove the render size setting, pass in a value of
     * <code>null</code> for <code>size</code>.
     *
     * @param size a <code>Dimension</code> indicating the desired
     * width and height.
     *
     * @exception IllegalArgumentException if either the width or the
     * height is negative or 0.
     * @exception UnsupportedOperationException if image resizing
     * is not supported by this plug-in.
     *
     * @see #getSourceRenderSize
     * @see ImageReader#getWidth
     * @see ImageReader#getHeight
     * @see ImageReader#getAspectRatio
     */
    public void setSourceRenderSize(Dimension size)
        throws UnsupportedOperationException {
        if (!canSetSourceRenderSize()) {
            throw new UnsupportedOperationException
                ("Can't set source render size!");
        }

        if (size == null) {
            this.sourceRenderSize = null;
        } else {
            if (size.width <= 0 || size.height <= 0) {
                throw new IllegalArgumentException("width or height <= 0!");
            }
            this.sourceRenderSize = (Dimension)size.clone();
        }
    }

    /**
     * Returns the width and height of the source image as it
     * will be rendered during decoding, if they have been set via the
     * <code>setSourceRenderSize</code> method.  A
     * <code>null</code>value indicates that no setting has been made.
     *
     * @return the rendered width and height of the source image
     * as a <code>Dimension</code>.
     *
     * @see #setSourceRenderSize
     */
    public Dimension getSourceRenderSize() {
        return (sourceRenderSize == null) ?
            null : (Dimension)sourceRenderSize.clone();
    }

    /**
     * Sets the range of progressive passes that will be decoded.
     * Passes outside of this range will be ignored.
     *
     * <p> A progressive pass is a re-encoding of the entire image,
     * generally at progressively higher effective resolutions, but
     * requiring greater transmission bandwidth.  The most common use
     * of progressive encoding is found in the JPEG format, where
     * successive passes include more detailed representations of the
     * high-frequency image content.
     *
     * <p> The actual number of passes to be decoded is determined
     * during decoding, based on the number of actual passes available
     * in the stream.  Thus if <code>minPass + numPasses - 1</code> is
     * larger than the index of the last available passes, decoding
     * will end with that pass.
     *
     * <p> A value of <code>numPasses</code> of
     * <code>Integer.MAX_VALUE</code> indicates that all passes from
     * <code>minPass</code> forward should be read.  Otherwise, the
     * index of the last pass (<i>i.e.</i>, <code>minPass + numPasses
     * - 1</code>) must not exceed <code>Integer.MAX_VALUE</code>.
     *
     * <p> There is no <code>unsetSourceProgressivePasses</code>
     * method; the same effect may be obtained by calling
     * <code>setSourceProgressivePasses(0, Integer.MAX_VALUE)</code>.
     *
     * @param minPass the index of the first pass to be decoded.
     * @param numPasses the maximum number of passes to be decoded.
     *
     * @exception IllegalArgumentException if <code>minPass</code> is
     * negative, <code>numPasses</code> is negative or 0, or
     * <code>numPasses</code> is smaller than
     * <code>Integer.MAX_VALUE</code> but <code>minPass +
     * numPasses - 1</code> is greater than
     * <code>INTEGER.MAX_VALUE</code>.
     *
     * @see #getSourceMinProgressivePass
     * @see #getSourceMaxProgressivePass
     */
    public void setSourceProgressivePasses(int minPass, int numPasses) {
        if (minPass < 0) {
            throw new IllegalArgumentException("minPass < 0!");
        }
        if (numPasses <= 0) {
            throw new IllegalArgumentException("numPasses <= 0!");
        }
        if ((numPasses != Integer.MAX_VALUE) &&
            (((minPass + numPasses - 1) & 0x80000000) != 0)) {
            throw new IllegalArgumentException
                ("minPass + numPasses - 1 > INTEGER.MAX_VALUE!");
        }

        this.minProgressivePass = minPass;
        this.numProgressivePasses = numPasses;
    }

    /**
     * Returns the index of the first progressive pass that will be
     * decoded. If no value has been set, 0 will be returned (which is
     * the correct value).
     *
     * @return the index of the first pass that will be decoded.
     *
     * @see #setSourceProgressivePasses
     * @see #getSourceNumProgressivePasses
     */
    public int getSourceMinProgressivePass() {
        return minProgressivePass;
    }

    /**
     * If <code>getSourceNumProgressivePasses</code> is equal to
     * <code>Integer.MAX_VALUE</code>, returns
     * <code>Integer.MAX_VALUE</code>.  Otherwise, returns
     * <code>getSourceMinProgressivePass() +
     * getSourceNumProgressivePasses() - 1</code>.
     *
     * @return the index of the last pass to be read, or
     * <code>Integer.MAX_VALUE</code>.
     */
    public int getSourceMaxProgressivePass() {
        if (numProgressivePasses == Integer.MAX_VALUE) {
            return Integer.MAX_VALUE;
        } else {
            return minProgressivePass + numProgressivePasses - 1;
        }
    }

    /**
     * Returns the number of the progressive passes that will be
     * decoded. If no value has been set,
     * <code>Integer.MAX_VALUE</code> will be returned (which is the
     * correct value).
     *
     * @return the number of the passes that will be decoded.
     *
     * @see #setSourceProgressivePasses
     * @see #getSourceMinProgressivePass
     */
    public int getSourceNumProgressivePasses() {
        return numProgressivePasses;
    }
}