packedcolormodel.java

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/*
 * @(#)PackedColorModel.java	1.37 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.image;

import java.awt.Transparency;
import java.awt.color.ColorSpace;

/**
 * The <code>PackedColorModel</code> class is an abstract 
 * {@link ColorModel} class that works with pixel values which represent
 * color and alpha information as separate samples and which pack all
 * samples for a single pixel into a single int, short, or byte quantity.
 * This class can be used with an arbitrary {@link ColorSpace}.  The number of
 * color samples in the pixel values must be the same as the number of color
 * components in the <code>ColorSpace</code>.  There can be a single alpha 
 * sample.  The array length is always 1 for those methods that use a
 * primitive array pixel representation of type <code>transferType</code>.  
 * The transfer types supported are DataBuffer.TYPE_BYTE, 
 * DataBuffer.TYPE_USHORT, and DataBuffer.TYPE_INT.  
 * Color and alpha samples are stored in the single element of the array
 * in bits indicated by bit masks.  Each bit mask must be contiguous and
 * masks must not overlap.  The same masks apply to the single int
 * pixel representation used by other methods.  The correspondence of
 * masks and color/alpha samples is as follows:
 * <ul>
 * <li> Masks are identified by indices running from 0 through 
 * {@link ColorModel#getNumComponents() getNumComponents}&nbsp;-&nbsp;1.  
 * <li> The first 
 * {@link ColorModel#getNumColorComponents() getNumColorComponents} 
 * indices refer to color samples.  
 * <li> If an alpha sample is present, it corresponds the last index.  
 * <li> The order of the color indices is specified
 * by the <code>ColorSpace</code>.  Typically, this reflects the name of
 * the color space type (for example, TYPE_RGB), index 0
 * corresponds to red, index 1 to green, and index 2 to blue.  
 * </ul>
 * <p>
 * The translation from pixel values to color/alpha components for
 * display or processing purposes is a one-to-one correspondence of
 * samples to components.
 * A <code>PackedColorModel</code> is typically used with image data 
 * that uses masks to define packed samples.  For example, a 
 * <code>PackedColorModel</code> can be used in conjunction with a 
 * {@link SinglePixelPackedSampleModel} to construct a
 * {@link BufferedImage}.  Normally the masks used by the 
 * {@link SampleModel} and the <code>ColorModel</code> would be the same.  
 * However, if they are different, the color interpretation of pixel data is
 * done according to the masks of the <code>ColorModel</code>.
 * <p>
 * A single <code>int</code> pixel representation is valid for all objects 
 * of this class since it is always possible to represent pixel values 
 * used with this class in a single <code>int</code>.  Therefore, methods
 * that use this representation do not throw an 
 * <code>IllegalArgumentException</code> due to an invalid pixel value.
 * <p>
 * A subclass of <code>PackedColorModel</code> is {@link DirectColorModel}, 
 * which is similar to an X11 TrueColor visual.
 *
 * @see DirectColorModel
 * @see SinglePixelPackedSampleModel
 * @see BufferedImage
 * @version 10 Feb 1997
 */

public abstract class PackedColorModel extends ColorModel {
    int[] maskArray;
    int[] maskOffsets;
    float[] scaleFactors;

    /**
     * Constructs a <code>PackedColorModel</code> from a color mask array, 
     * which specifies which bits in an <code>int</code> pixel representation 
     * contain each of the color samples, and an alpha mask.  Color
     * components are in the specified <code>ColorSpace</code>.  The length of 
     * <code>colorMaskArray</code> should be the number of components in
     * the <code>ColorSpace</code>.  All of the bits in each mask
     * must be contiguous and fit in the specified number of least significant
     * bits of an <code>int</code> pixel representation.  If the 
     * <code>alphaMask</code> is 0, there is no alpha.  If there is alpha, 
     * the <code>boolean</code> <code>isAlphaPremultiplied</code> specifies
     * how to interpret color and alpha samples in pixel values.  If the
     * <code>boolean</code> is <code>true</code>, color samples are assumed
     * to have been multiplied by the alpha sample.  The transparency, 
     * <code>trans</code>, specifies what alpha values can be represented 
     * by this color model.  The transfer type is the type of primitive
     * array used to represent pixel values.
     * @param space the specified <code>ColorSpace</code>
     * @param bits the number of bits in the pixel values
     * @param colorMaskArray array that specifies the masks representing
     *         the bits of the pixel values that represent the color
     *         components 
     * @param alphaMask specifies the mask representing
     *         the bits of the pixel values that represent the alpha
     *         component
     * @param isAlphaPremultiplied <code>true</code> if color samples are
     *        premultiplied by the alpha sample; <code>false</code> otherwise
     * @param trans specifies the alpha value that can be represented by
     *        this color model
     * @param transferType the type of array used to represent pixel values
     * @throws IllegalArgumentException if <code>bits</code> is less than
     *         1 or greater than 32
     */
    public PackedColorModel (ColorSpace space, int bits,
                             int[] colorMaskArray, int alphaMask,
                             boolean isAlphaPremultiplied,
                             int trans, int transferType) {
        super(bits, PackedColorModel.createBitsArray(colorMaskArray,
                                                     alphaMask),
              space, (alphaMask == 0 ? false : true),
              isAlphaPremultiplied, trans, transferType);
        if (bits < 1 || bits > 32) {
            throw new IllegalArgumentException("Number of bits must be between"
                                               +" 1 and 32.");
        }
        maskArray   = new int[numComponents];
        maskOffsets = new int[numComponents];
        scaleFactors = new float[numComponents];

        for (int i=0; i < numColorComponents; i++) {
            // Get the mask offset and #bits
            DecomposeMask(colorMaskArray[i], i, space.getName(i));
        }
        if (alphaMask != 0) {
            DecomposeMask(alphaMask, numColorComponents, "alpha");
            if (nBits[numComponents-1] == 1) {
                transparency = Transparency.BITMASK;
            }
        }
    }

    /**
     * Constructs a <code>PackedColorModel</code> from the specified
     * masks which indicate which bits in an <code>int</code> pixel 
     * representation contain the alpha, red, green and blue color samples.  
     * Color components are in the specified <code>ColorSpace</code>, which 
     * must be of type ColorSpace.TYPE_RGB.  All of the bits in each
     * mask must be contiguous and fit in the specified number of
     * least significant bits of an <code>int</code> pixel representation.  If
     * <code>amask</code> is 0, there is no alpha.  If there is alpha, 
     * the <code>boolean</code> <code>isAlphaPremultiplied</code>
     * specifies how to interpret color and alpha samples
     * in pixel values.  If the <code>boolean</code> is <code>true</code>, 
     * color samples are assumed to have been multiplied by the alpha sample.
     * The transparency, <code>trans</code>, specifies what alpha values
     * can be represented by this color model.
     * The transfer type is the type of primitive array used to represent
     * pixel values.
     * @param space the specified <code>ColorSpace</code>
     * @param bits the number of bits in the pixel values
     * @param rmask specifies the mask representing
     *         the bits of the pixel values that represent the red
     *         color component
     * @param gmask specifies the mask representing
     *         the bits of the pixel values that represent the green 
     *         color component
     * @param bmask specifies the mask representing
     *         the bits of the pixel values that represent 
     *         the blue color component
     * @param amask specifies the mask representing
     *         the bits of the pixel values that represent 
     *         the alpha component
     * @param isAlphaPremultiplied <code>true</code> if color samples are
     *        premultiplied by the alpha sample; <code>false</code> otherwise
     * @param trans specifies the alpha value that can be represented by
     *        this color model
     * @param transferType the type of array used to represent pixel values
     * @throws IllegalArgumentException if <code>space</code> is not a
     *         TYPE_RGB space
     * @see ColorSpace
     */
    public PackedColorModel(ColorSpace space, int bits, int rmask, int gmask,
                            int bmask, int amask,
                            boolean isAlphaPremultiplied,
                            int trans, int transferType) {
        super (bits, PackedColorModel.createBitsArray(rmask, gmask, bmask,
                                                      amask),
               space, (amask == 0 ? false : true),
               isAlphaPremultiplied, trans, transferType);

        if (space.getType() != ColorSpace.TYPE_RGB) {
            throw new IllegalArgumentException("ColorSpace must be TYPE_RGB.");
        }
        maskArray = new int[numComponents];
        maskOffsets = new int[numComponents];
        scaleFactors = new float[numComponents];

        DecomposeMask(rmask, 0, "red");

        DecomposeMask(gmask, 1, "green");

        DecomposeMask(bmask, 2, "blue");

        if (amask != 0) {
            DecomposeMask(amask, 3, "alpha");
            if (nBits[3] == 1) {
                transparency = Transparency.BITMASK;
            }
        }
    }

    /**
     * Returns the mask indicating which bits in a pixel 
     * contain the specified color/alpha sample.  For color 
     * samples, <code>index</code> corresponds to the placement of color
     * sample names in the color space.  Thus, an <code>index</code>
     * equal to 0 for a CMYK ColorSpace would correspond to
     * Cyan and an <code>index</code> equal to 1 would correspond to 
     * Magenta.  If there is alpha, the alpha <code>index</code> would be:
     * <pre>
     *      alphaIndex = numComponents() - 1;
     * </pre>
     * @param index the specified color or alpha sample
     * @return the mask, which indicates which bits of the <code>int</code> 
     *         pixel representation contain the color or alpha sample specified
     *         by <code>index</code>.
     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is
     *         greater than the number of components minus 1 in this 
     *         <code>PackedColorModel</code> or if <code>index</code> is
     *         less than zero
     */
    final public int getMask(int index) {
	return maskArray[index];
    }

    /**
     * Returns a mask array indicating which bits in a pixel
     * contain the color and alpha samples.  
     * @return the mask array , which indicates which bits of the