/*****************************************************************************
 * Copyright (C) The Apache Software Foundation. All rights reserved.        *
 * ------------------------------------------------------------------------- *
 * This software is published under the terms of the Apache Software License *
 * version 1.1, a copy of which has been included with this distribution in  *
 * the LICENSE file.                                                         *
 *****************************************************************************/

package org.apache.batik.ext.awt.image.codec;

import java.awt.image.Raster;
import java.awt.image.RenderedImage;
import java.io.IOException;
import java.io.InputStream;

/**
 * A partial implementation of the <code>ImageDecoder</code> interface
 * useful for subclassing.
 *
 */
public abstract class ImageDecoderImpl implements ImageDecoder {

    /**
     * The <code>SeekableStream</code> associcted with this
     * <code>ImageEncoder</code>.
     */
    protected SeekableStream input;

    /**
     * The <code>ImageDecodeParam</code> object associated with this
     * <code>ImageEncoder</code>.
     */
    protected ImageDecodeParam param;

    /**
     * Constructs an <code>ImageDecoderImpl</code> with a given
     * <code>SeekableStream</code> and <code>ImageDecodeParam</code>
     * instance.
     */
    public ImageDecoderImpl(SeekableStream input,
                            ImageDecodeParam param) {
        this.input = input;
        this.param = param;
    }

    /**
     * Constructs an <code>ImageDecoderImpl</code> with a given
     * <code>InputStream</code> and <code>ImageDecodeParam</code>
     * instance.  The <code>input</code> parameter will be used to
     * construct a <code>ForwardSeekableStream</code>; if the ability
     * to seek backwards is required, the caller should construct
     * an instance of <code>SeekableStream</code> and
     * make use of the other contructor.
     */
    public ImageDecoderImpl(InputStream input,
                            ImageDecodeParam param) {
        this.input = new ForwardSeekableStream(input);
        this.param = param;
    }

    /**
     * Returns the current parameters as an instance of the
     * <code>ImageDecodeParam</code> interface.  Concrete
     * implementations of this interface will return corresponding
     * concrete implementations of the <code>ImageDecodeParam</code>
     * interface.  For example, a <code>JPEGImageDecoder</code> will
     * return an instance of <code>JPEGDecodeParam</code>.
     */
    public ImageDecodeParam getParam() {
        return param;
    }

    /**
     * Sets the current parameters to an instance of the
     * <code>ImageDecodeParam</code> interface.  Concrete
     * implementations of <code>ImageDecoder</code> may throw a
     * <code>RuntimeException</code> if the <code>param</code>
     * argument is not an instance of the appropriate subclass or
     * subinterface.  For example, a <code>JPEGImageDecoder</code>
     * will expect <code>param</code> to be an instance of
     * <code>JPEGDecodeParam</code>.
     */
    public void setParam(ImageDecodeParam param) {
        this.param = param;
    }

    /**
     * Returns the <code>SeekableStream</code> associated with
     * this <code>ImageDecoder</code>.
     */
    public SeekableStream getInputStream() {
        return input;
    }

    /**
     * Returns the number of pages present in the current stream.
     * By default, the return value is 1.  Subclasses that deal with
     * multi-page formats should override this method.
     */
    public int getNumPages() throws IOException {
        return 1;
    }
    
    /**
     * Returns a <code>Raster</code> that contains the decoded
     * contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>.  Only
     * the first page of a multi-page image is decoded.
     */
    public Raster decodeAsRaster() throws IOException {
        return decodeAsRaster(0);
    }

    /**
     * Returns a <code>Raster</code> that contains the decoded
     * contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>.
     * The given page of a multi-page image is decoded.  If
     * the page does not exist, an IOException will be thrown.
     * Page numbering begins at zero.
     *
     * @param page The page to be decoded.
     */
    public Raster decodeAsRaster(int page) throws IOException {
        RenderedImage im = decodeAsRenderedImage(page);
        return im.getData();
    }

    /**
     * Returns a <code>RenderedImage</code> that contains the decoded
     * contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>.  Only
     * the first page of a multi-page image is decoded.
     */
    public RenderedImage decodeAsRenderedImage() throws IOException {
        return decodeAsRenderedImage(0);
    }

    /**
     * Returns a <code>RenderedImage</code> that contains the decoded
     * contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>.
     * The given page of a multi-page image is decoded.  If
     * the page does not exist, an IOException will be thrown.
     * Page numbering begins at zero.
     *
     * @param page The page to be decoded.
     */
    public abstract RenderedImage decodeAsRenderedImage(int page)
        throws IOException;
}
