gov/nasa/worldwind/formats/nitfs/Cib2DdsCompress.java

   1 package gov.nasa.worldwind.formats.nitfs;
   2
   3 import gov.nasa.worldwind.*;
   4 /*
   5 Copyright (C) 2001, 2007 United States Government
   6 as represented by the Administrator of the
   7 National Aeronautics and Space Administration.
   8 All Rights Reserved.
   9 */
  10
  11 /**
  12  * @author Lado Garakanidze
  13  * @version $Id: Cib2DdsCompress Apr 23, 2007 10:59:01 AM lado
  14  */
  15 class Cib2DdsCompress extends AbstractRpf2DdsCompress
  16 {
  17     public DDSBlock4x4 compressDxt1Block4x4(NitfsImageBand imageBand, byte[] pixelCodes, boolean hasTransparentPixels)
  18     {
  19         int[]   grayPixels = new int[16];
  20         int minColor = Integer.MAX_VALUE;
  21         int maxColor = Integer.MIN_VALUE;
  22
  23         for(int i = 0; i < pixelCodes.length; i++ )
  24         {
  25             grayPixels[i] = imageBand.lookupGray( 0xFF & pixelCodes[i]);
  26             if(grayPixels[i] < minColor)
  27                 minColor = grayPixels[i];
  28             if(grayPixels[i] > maxColor)
  29                 maxColor = grayPixels[i];
  30         }
  31
  32         DDSBlock4x4 ddsBlock = new DDSBlock4x4(
  33             (short) DDSConverter.getPixel565( new Color( maxColor, maxColor, maxColor ) ),
  34             (short) DDSConverter.getPixel565( new Color( minColor, minColor, minColor ) ),
  35             0);
  36
  37         if(maxColor != minColor)
  38         {
  39             int[] ext = new int[] { maxColor, minColor, (2 * maxColor + minColor)/3, (maxColor + 2 * minColor)/3 };
  40             ddsBlock.bitmask = 0;
  41             for (int i = 0; i < grayPixels.length; i++)
  42             {
  43                 int closest = Integer.MAX_VALUE;
  44                 int mask = 0;
  45                 for (int j = 0; j < ext.length; j++)
  46                 {
  47                     int d = ( ext[j] >= grayPixels[i] ) ? (ext[j] - grayPixels[i]) : (grayPixels[i] - ext[j]);
  48                     if (d < closest)
  49                     {
  50                         closest = d;
  51                         mask = j;
  52                     }
  53                 }
  54                 ddsBlock.bitmask |= mask << i * 2;
  55             }
  56         }
  57         return  ddsBlock;
  58     }
  59 }