src.gov.nasa.worldwind.formats.dds.AlphaBlockDXT3 Maven / Gradle / Ivy

/*
 * Copyright (C) 2012 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration.
 * All Rights Reserved.
 */
package gov.nasa.worldwind.formats.dds;

/**
 * AlphaBlockDXT3 is a data structure representing the compressed alpha values in a single DXT2/DXT3 block.
 * The DXT2/DXT3 alpha block contains alpha values for 4x4 pixels, each quantized to fit into 4 bits. The alpha values
 * are tightly packed into 64 bits in the DXT file as follows, where the value aN represents the Nth alpha value in
 * hexadecimal notation:
 * 
 * | 63-56 | 55-48 | 47-40 | 39-32 | 31-24 | 23-16 | 15-8  | 7-0    |
 * | aFaE  | aDaC  | aBaA  | a9a8  | a7a6  | a5a4  | a3a2  | a1a0   |
 *
 * @author dcollins
 * @version $Id: AlphaBlockDXT3.java 1171 2013-02-11 21:45:02Z dcollins $
 */
public class AlphaBlockDXT3
{
    /**
     * The 4x4 block of 4 bit alpha values stored as a 64 bit long number.
     */
    public long alphaValueMask;

    /**
     * Creates a new DXT2/DXT3 alpha block with all alpha values set to 0.
     */
    public AlphaBlockDXT3()
    {
    }

    public AlphaBlockDXT3(long alphaValueMask)
    {
        this.alphaValueMask = alphaValueMask;
    }

    /**
     * Returns the 4x4 block of 4 bit alpha values as a 64 bit number.
     *
     * @return 4x4 block of 4 bit alpha values.
     */
    public long getAlphaValueMask()
    {
        return this.alphaValueMask;
    }

    /**
     * Sets the 4x4 block of 4 bit alpha values as a 64 bit number.
     *
     * @param valueMask 4x4 block of 4 bit alpha values.
     */
    public void setAlphaValueMask(long valueMask)
    {
        this.alphaValueMask = valueMask;
    }
}