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package java.awt.image;

/**

 * This abstract class defines a lookup table object.  ByteLookupTable

 * and ShortLookupTable are subclasses, which

 * contain byte and short data, respectively.  A lookup table

 * contains data arrays for one or more bands (or components) of an image

 * (for example, separate arrays for R, G, and B),

 * and it contains an offset which will be subtracted from the

 * input values before indexing into the arrays.  This allows an array

 * smaller than the native data size to be provided for a

 * constrained input.  If there is only one array in the lookup

 * table, it will be applied to all bands.  All arrays must be the

 * same size.

 *

 * @see ByteLookupTable

 * @see ShortLookupTable

 * @see LookupOp

 */

public abstract class LookupTable {

    /**

     * Constants

     */

    int  numComponents;

    int  offset;

    int  numEntries;

    /**

     * Constructs a new LookupTable from the number of components and an offset

     * into the lookup table.

     * @param offset the offset to subtract from input values before indexing

     *        into the data arrays for this {@code LookupTable}

     * @param numComponents the number of data arrays in this

     *        {@code LookupTable}

     * @throws IllegalArgumentException if {@code offset} is less than 0

     *         or if {@code numComponents} is less than 1

     */

    protected LookupTable(int offset, int numComponents) {

        if (offset < 0) {

            throw new

                IllegalArgumentException("Offset must be greater than 0");

        }

        if (numComponents < 1) {

            throw new IllegalArgumentException("Number of components must "+

                                               " be at least 1");

        }

        this.numComponents = numComponents;

        this.offset = offset;

    }

    /**

     * Returns the number of components in the lookup table.

     * @return the number of components in this {@code LookupTable}.

     */

    public int getNumComponents() {

        return numComponents;

    }

    /**

     * Returns the offset.

     * @return the offset of this {@code LookupTable}.

     */

    public int getOffset() {

        return offset;

    }

    /**

     * Returns an {@code int} array of components for

     * one pixel.  The {@code dest} array contains the

     * result of the lookup and is returned.  If dest is

     * {@code null}, a new array is allocated.  The

     * source and destination can be equal.

     * @param src the source array of components of one pixel

     * @param dest the destination array of components for one pixel,

     *        translated with this {@code LookupTable}

     * @return an {@code int} array of components for one

     *         pixel.

     */

    public abstract int[] lookupPixel(int[] src, int[] dest);

}