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package javax.imageio.event;

import java.awt.image.BufferedImage;
import java.util.EventListener;
import javax.imageio.ImageReader;

/**
 * An interface used by <code>ImageReader</code> implementations to
 * notify callers of their image and thumbnail reading methods of
 * pixel updates.
 *
 * @see javax.imageio.ImageReader#addIIOReadUpdateListener
 * @see javax.imageio.ImageReader#removeIIOReadUpdateListener
 *
 */
public interface IIOReadUpdateListener extends EventListener {

    /**
     * Reports that the current read operation is about to begin a
     * progressive pass.  Readers of formats that support progressive
     * encoding should use this to notify clients when each pass is
     * completed when reading a progressively encoded image.
     *
     * <p> An estimate of the area that will be updated by the pass is
     * indicated by the <code>minX</code>, <code>minY</code>,
     * <code>width</code>, and <code>height</code> parameters.  If the
     * pass is interlaced, that is, it only updates selected rows or
     * columns, the <code>periodX</code> and <code>periodY</code>
     * parameters will indicate the degree of subsampling.  The set of
     * bands that may be affected is indicated by the value of
     * <code>bands</code>.
     *
     * @param source the <code>ImageReader</code> object calling this
     * method.
     * @param theImage the <code>BufferedImage</code> being updated.
     * @param pass the numer of the pass that is about to begin,
     * starting with 0.
     * @param minPass the index of the first pass that will be decoded.
     * @param maxPass the index of the last pass that will be decoded.
     * @param minX the X coordinate of the leftmost updated column
     * of pixels.
     * @param minY the Y coordinate of the uppermost updated row
     * of pixels.
     * @param periodX the horizontal spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param periodY the vertical spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param bands an array of <code>int</code>s indicating the the
     * set bands that may be updated.
     */
    void passStarted(ImageReader source,
                     BufferedImage theImage,
                     int pass,
                     int minPass, int maxPass,
                     int minX, int minY,
                     int periodX, int periodY,
                     int[] bands);

    /**
     * Reports that a given region of the image has been updated.
     * The application might choose to redisplay the specified area,
     * for example, in order to provide a progressive display effect,
     * or perform other incremental processing.
     *
     * <p> Note that different image format readers may produce
     * decoded pixels in a variety of different orders.  Many readers
     * will produce pixels in a simple top-to-bottom,
     * left-to-right-order, but others may use multiple passes of
     * interlacing, tiling, etc.  The sequence of updates may even
     * differ from call to call depending on network speeds, for
     * example.  A call to this method does not guarantee that all the
     * specified pixels have actually been updated, only that some
     * activity has taken place within some subregion of the one
     * specified.
     *
     * <p> The particular <code>ImageReader</code> implementation may
     * choose how often to provide updates.  Each update specifies
     * that a given region of the image has been updated since the
     * last update.  A region is described by its spatial bounding box
     * (<code>minX</code>, <code>minY</code>, <code>width</code>, and
     * <code>height</code>); X and Y subsampling factors
     * (<code>periodX</code> and <code>periodY</code>); and a set of
     * updated bands (<code>bands</code>).  For example, the update:
     *
     * <pre>
     * minX = 10
     * minY = 20
     * width = 3
     * height = 4
     * periodX = 2
     * periodY = 3
     * bands = { 1, 3 }
     * </pre>
     *
     * would indicate that bands 1 and 3 of the following pixels were
     * updated:
     *
     * <pre>
     * (10, 20) (12, 20) (14, 20)
     * (10, 23) (12, 23) (14, 23)
     * (10, 26) (12, 26) (14, 26)
     * (10, 29) (12, 29) (14, 29)
     * </pre>
     *
     * @param source the <code>ImageReader</code> object calling this method.
     * @param theImage the <code>BufferedImage</code> being updated.
     * @param minX the X coordinate of the leftmost updated column
     * of pixels.
     * @param minY the Y coordinate of the uppermost updated row
     * of pixels.
     * @param width the number of updated pixels horizontally.
     * @param height the number of updated pixels vertically.
     * @param periodX the horizontal spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param periodY the vertical spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param bands an array of <code>int</code>s indicating which
     * bands are being updated.
     */
    void imageUpdate(ImageReader source,
                     BufferedImage theImage,
                     int minX, int minY,
                     int width, int height,
                     int periodX, int periodY,
                     int[] bands);

    /**
     * Reports that the current read operation has completed a
     * progressive pass.  Readers of formats that support
     * progressive encoding should use this to notify clients when
     * each pass is completed when reading a progressively
     * encoded image.
     *
     * @param source the <code>ImageReader</code> object calling this
     * method.
     * @param theImage the <code>BufferedImage</code> being updated.
     *
     * @see javax.imageio.ImageReadParam#setSourceProgressivePasses(int, int)
     */
    void passComplete(ImageReader source, BufferedImage theImage);

    /**
     * Reports that the current thumbnail read operation is about to
     * begin a progressive pass.  Readers of formats that support
     * progressive encoding should use this to notify clients when
     * each pass is completed when reading a progressively encoded
     * thumbnail image.
     *
     * @param source the <code>ImageReader</code> object calling this
     * method.
     * @param theThumbnail the <code>BufferedImage</code> thumbnail
     * being updated.
     * @param pass the numer of the pass that is about to begin,
     * starting with 0.
     * @param minPass the index of the first pass that will be decoded.
     * @param maxPass the index of the last pass that will be decoded.
     * @param minX the X coordinate of the leftmost updated column
     * of pixels.
     * @param minY the Y coordinate of the uppermost updated row
     * of pixels.
     * @param periodX the horizontal spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param periodY the vertical spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param bands an array of <code>int</code>s indicating the the
     * set bands that may be updated.
     *
     * @see #passStarted
     */
    void thumbnailPassStarted(ImageReader source,
                              BufferedImage theThumbnail,
                              int pass,
                              int minPass, int maxPass,
                              int minX, int minY,
                              int periodX, int periodY,
                              int[] bands);

    /**
     * Reports that a given region of a thumbnail image has been updated.
     * The application might choose to redisplay the specified area,
     * for example, in order to provide a progressive display effect,
     * or perform other incremental processing.
     *
     * @param source the <code>ImageReader</code> object calling this method.
     * @param theThumbnail the <code>BufferedImage</code> thumbnail
     * being updated.
     * @param minX the X coordinate of the leftmost updated column
     * of pixels.
     * @param minY the Y coordinate of the uppermost updated row
     * of pixels.
     * @param width the number of updated pixels horizontally.
     * @param height the number of updated pixels vertically.
     * @param periodX the horizontal spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param periodY the vertical spacing between updated pixels;
     * a value of 1 means no gaps.
     * @param bands an array of <code>int</code>s indicating which
     * bands are being updated.
     *
     * @see #imageUpdate
     */
    void thumbnailUpdate(ImageReader source,
                         BufferedImage theThumbnail,
                         int minX, int minY,
                         int width, int height,
                         int periodX, int periodY,
                         int[] bands);

    /**
     * Reports that the current thumbnail read operation has completed
     * a progressive pass.  Readers of formats that support
     * progressive encoding should use this to notify clients when
     * each pass is completed when reading a progressively encoded
     * thumbnail image.
     *
     * @param source the <code>ImageReader</code> object calling this
     * method.
     * @param theThumbnail the <code>BufferedImage</code> thumbnail
     * being updated.
     *
     * @see #passComplete
     */
    void thumbnailPassComplete(ImageReader source, BufferedImage theThumbnail);
}