src/main/java/eu/svjatoslav/imagesqueeze/codec/Table.java

   1 /*
   2  * Imagesqueeze - Image codec optimized for photos.
   3  * Copyright (C) 2012, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public License
   7  * as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.imagesqueeze.codec;
  11
  12 import eu.svjatoslav.commons.data.BitInputStream;
  13 import eu.svjatoslav.commons.data.BitOutputStream;
  14
  15 import java.io.IOException;
  16
  17 /**
  18  * Quick lookup table.
  19  */
  20
  21 public class Table {
  22
  23     private int[] range = new int[100];
  24     private int[] switchThreshold = new int[100];
  25     private int[] bitCount = new int[100];
  26
  27     private int[] bitCountForRange = new int[256];
  28     private int[] proposedRangeForActualRange = new int[256];
  29     private int[] proposedRangeForActualRangeLow = new int[256];
  30     private int[] proposedRangeForActualRangeHigh = new int[256];
  31     private byte[] proposedDecreasedRange = new byte[256];
  32
  33     private int usedEntries = 0;
  34
  35     /**
  36      * @param switchThreshold - switch to this range when actual range in equal or below
  37      *                        this threshold
  38      */
  39     public void addEntry(int range, int switchThreshold, int bitcount) {
  40         if (range < 0)
  41             range = 0;
  42         if (range > 255)
  43             range = 255;
  44
  45         if (switchThreshold < 0)
  46             switchThreshold = 0;
  47         if (switchThreshold > 255)
  48             switchThreshold = 255;
  49
  50         if (bitcount < 0)
  51             bitcount = 0;
  52         if (bitcount > 8)
  53             bitcount = 8;
  54
  55         this.range[usedEntries] = range;
  56         this.switchThreshold[usedEntries] = switchThreshold;
  57         this.bitCount[usedEntries] = bitcount;
  58         usedEntries++;
  59     }
  60
  61     public void computeLookupTables() {
  62         int currentCheckPointer = 0;
  63
  64         for (int i = 0; i < 256; i++) {
  65
  66             if (range[currentCheckPointer] == i)
  67                 currentCheckPointer++;
  68
  69             if (currentCheckPointer > 0)
  70                 bitCountForRange[i] = bitCount[currentCheckPointer - 1];
  71             else
  72                 bitCountForRange[i] = 0;
  73
  74         }
  75
  76         for (int i = 0; i < 256; i++) {
  77
  78             int seek;
  79             seekLoop:
  80             {
  81                 for (seek = 0; seek < usedEntries; seek++)
  82                     if (switchThreshold[seek] >= i)
  83                         break seekLoop;
  84             }
  85
  86             proposedRangeForActualRange[i] = range[seek];
  87             if (seek == 0)
  88                 proposedRangeForActualRangeLow[i] = 0;
  89             else
  90                 proposedRangeForActualRangeLow[i] = switchThreshold[seek - 1] + 1;
  91             proposedRangeForActualRangeHigh[i] = switchThreshold[seek];
  92         }
  93
  94         currentCheckPointer = usedEntries - 2;
  95         for (int i = 255; i >= 0; i--) {
  96             if (range[currentCheckPointer] == i)
  97                 currentCheckPointer--;
  98
  99             if (currentCheckPointer < 0)
 100                 proposedDecreasedRange[i] = 0;
 101             else
 102                 proposedDecreasedRange[i] = (byte) (range[currentCheckPointer]);
 103         }
 104
 105     }
 106
 107     public void load(final BitInputStream inputStream) throws IOException {
 108         reset();
 109
 110         final int availableEntries = ImageDecoder
 111                 .readIntegerCompressed8(inputStream);
 112
 113         for (int i = 0; i < availableEntries; i++)
 114             addEntry(inputStream.readBits(8), inputStream.readBits(8),
 115                     inputStream.readBits(4));
 116     }
 117
 118     public int proposeBitcountForRange(int range) {
 119         if (range > 255)
 120             range = 255;
 121         if (range < 0)
 122             range = 0;
 123         return bitCountForRange[range];
 124     }
 125
 126     public int proposeDecreasedRange(int range) {
 127         if (range > 255)
 128             range = 255;
 129         if (range < 0)
 130             range = 0;
 131
 132         return ImageEncoder.byteToInt(proposedDecreasedRange[range]);
 133     }
 134
 135     public int proposeRangeForRange(final int actualRange, int inheritedRange) {
 136
 137         if (inheritedRange > 255)
 138             inheritedRange = 255;
 139         if (inheritedRange < 0)
 140             inheritedRange = 0;
 141
 142         if (proposedRangeForActualRangeLow[inheritedRange] <= actualRange)
 143             return inheritedRange;
 144
 145         return proposeDecreasedRange(inheritedRange);
 146     }
 147
 148     public void reset() {
 149         range = new int[100];
 150         switchThreshold = new int[100];
 151         bitCount = new int[100];
 152
 153         bitCountForRange = new int[256];
 154         proposedRangeForActualRange = new int[256];
 155         proposedRangeForActualRangeLow = new int[256];
 156         proposedRangeForActualRangeHigh = new int[256];
 157         proposedDecreasedRange = new byte[256];
 158
 159         usedEntries = 0;
 160     }
 161
 162     public void save(final BitOutputStream outputStream) throws IOException {
 163         ImageEncoder.storeIntegerCompressed8(outputStream, usedEntries);
 164
 165         for (int i = 0; i < usedEntries; i++) {
 166             outputStream.storeBits(range[i], 8);
 167             outputStream.storeBits(switchThreshold[i], 8);
 168             outputStream.storeBits(bitCount[i], 4);
 169         }
 170     }
 171
 172 }