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

   1 /*
   2  * Image codec. Author: Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   3  * This project is released under Creative Commons Zero (CC0) license.
   4  */
   5 package eu.svjatoslav.imagesqueeze.codec;
   6
   7 /**
   8  * Compressed image pixels decoder.
   9  */
  10
  11 import eu.svjatoslav.commons.data.BitInputStream;
  12
  13 import java.awt.image.DataBufferByte;
  14 import java.awt.image.WritableRaster;
  15 import java.io.IOException;
  16
  17 class ImageDecoder {
  18
  19     private final int width;
  20     private final int height;
  21     private final Image image;
  22     private final byte[] decodedYRangeMap;
  23     private final byte[] decodedYMap;
  24     private final byte[] decodedURangeMap;
  25     private final byte[] decodedUMap;
  26     private final byte[] decodedVRangeMap;
  27     private final byte[] decodedVMap;
  28     private final Approximator approximator;
  29     private final BitInputStream bitInputStream;
  30     private final OperatingContext context = new OperatingContext();
  31
  32     public ImageDecoder(final Image image, final BitInputStream bitInputStream) {
  33         approximator = new Approximator();
  34
  35         this.image = image;
  36         this.bitInputStream = bitInputStream;
  37
  38         width = image.metaData.width;
  39         height = image.metaData.height;
  40
  41         decodedYRangeMap = new byte[width * height];
  42         decodedYRangeMap[0] = (byte) (255);
  43         decodedYMap = new byte[width * height];
  44
  45         decodedURangeMap = new byte[width * height];
  46         decodedURangeMap[0] = (byte) (255);
  47         decodedUMap = new byte[width * height];
  48
  49         decodedVRangeMap = new byte[width * height];
  50         decodedVRangeMap[0] = (byte) (255);
  51         decodedVMap = new byte[width * height];
  52
  53     }
  54
  55     public static int readIntegerCompressed8(final BitInputStream inputStream)
  56             throws IOException {
  57
  58         if (inputStream.readBits(1) == 0)
  59             return inputStream.readBits(8);
  60         else
  61             return inputStream.readBits(32);
  62     }
  63
  64     public void decode() throws IOException {
  65         approximator.load(bitInputStream);
  66         approximator.computeLookupTables();
  67
  68         final WritableRaster raster = image.bufferedImage.getRaster();
  69         final DataBufferByte dbi = (DataBufferByte) raster.getDataBuffer();
  70         final byte[] pixels = dbi.getData();
  71
  72         // load top-, left-most pixel.
  73         decodedYMap[0] = (byte) bitInputStream.readBits(8);
  74         decodedUMap[0] = (byte) bitInputStream.readBits(8);
  75         decodedVMap[0] = (byte) bitInputStream.readBits(8);
  76
  77         final Color color = new Color();
  78         color.y = ImageEncoder.byteToInt(decodedYMap[0]);
  79         color.u = ImageEncoder.byteToInt(decodedUMap[0]);
  80         color.v = ImageEncoder.byteToInt(decodedVMap[0]);
  81
  82         color.YUV2RGB();
  83
  84         pixels[0] = (byte) color.r;
  85         pixels[0 + 1] = (byte) color.g;
  86         pixels[0 + 2] = (byte) color.b;
  87
  88         // detect initial step
  89         int largestDimension;
  90         int initialStep = 2;
  91         if (width > height)
  92             largestDimension = width;
  93         else
  94             largestDimension = height;
  95
  96         while (initialStep < largestDimension)
  97             initialStep = initialStep * 2;
  98
  99         grid(initialStep, pixels);
 100     }
 101
 102     private void grid(final int step, final byte[] pixels) throws IOException {
 103
 104         gridDiagonal(step / 2, step / 2, step, pixels);
 105         gridSquare(step / 2, 0, step, pixels);
 106         gridSquare(0, step / 2, step, pixels);
 107
 108         if (step > 2)
 109             grid(step / 2, pixels);
 110     }
 111
 112     private void gridDiagonal(final int offsetX, final int offsetY,
 113                               final int step, final byte[] pixels) throws IOException {
 114
 115         for (int y = offsetY; y < height; y = y + step)
 116             for (int x = offsetX; x < width; x = x + step) {
 117
 118                 final int halfStep = step / 2;
 119
 120                 context.initialize(image, decodedYMap, decodedUMap, decodedVMap);
 121                 context.measureNeighborEncode(x - halfStep, y - halfStep);
 122                 context.measureNeighborEncode(x + halfStep, y - halfStep);
 123                 context.measureNeighborEncode(x - halfStep, y + halfStep);
 124                 context.measureNeighborEncode(x + halfStep, y + halfStep);
 125
 126                 loadPixel(step, offsetX, offsetY, x, y, pixels,
 127                         context.colorStats.getAverageY(),
 128                         context.colorStats.getAverageU(),
 129                         context.colorStats.getAverageV());
 130
 131             }
 132     }
 133
 134     private void gridSquare(final int offsetX, final int offsetY,
 135                             final int step, final byte[] pixels) throws IOException {
 136
 137         for (int y = offsetY; y < height; y = y + step)
 138             for (int x = offsetX; x < width; x = x + step) {
 139
 140                 final int halfStep = step / 2;
 141
 142                 context.initialize(image, decodedYMap, decodedUMap, decodedVMap);
 143                 context.measureNeighborEncode(x - halfStep, y);
 144                 context.measureNeighborEncode(x + halfStep, y);
 145                 context.measureNeighborEncode(x, y - halfStep);
 146                 context.measureNeighborEncode(x, y + halfStep);
 147
 148                 loadPixel(step, offsetX, offsetY, x, y, pixels,
 149                         context.colorStats.getAverageY(),
 150                         context.colorStats.getAverageU(),
 151                         context.colorStats.getAverageV());
 152
 153             }
 154     }
 155
 156     private int loadChannel(final byte[] decodedRangeMap,
 157                             final byte[] decodedMap, final Table table,
 158                             final int averageDecodedValue, final int index,
 159                             final int parentIndex) throws IOException {
 160         int decodedValue = averageDecodedValue;
 161
 162         final int inheritedRange = ImageEncoder
 163                 .byteToInt(decodedRangeMap[parentIndex]);
 164         int computedRange = inheritedRange;
 165
 166         final int bitCount = table.proposeBitcountForRange(inheritedRange);
 167         int computedRangeBitCount;
 168         if (bitCount > 0) {
 169
 170             final int rangeDecreases = bitInputStream.readBits(1);
 171             if (rangeDecreases != 0)
 172                 computedRange = table.proposeDecreasedRange(inheritedRange);
 173
 174             decodedRangeMap[index] = (byte) computedRange;
 175             computedRangeBitCount = table
 176                     .proposeBitcountForRange(computedRange);
 177
 178             if (computedRangeBitCount > 0) {
 179
 180                 final int encodedDifference = bitInputStream
 181                         .readBits(computedRangeBitCount);
 182
 183                 final int decodedDifference = ImageEncoder
 184                         .decodeValueFromGivenBits(encodedDifference,
 185                                 computedRange, computedRangeBitCount);
 186
 187                 decodedValue = averageDecodedValue - decodedDifference;
 188                 if (decodedValue > 255)
 189                     decodedValue = 255;
 190                 if (decodedValue < 0)
 191                     decodedValue = 0;
 192             }
 193         } else
 194             decodedRangeMap[index] = (byte) inheritedRange;
 195         decodedMap[index] = (byte) decodedValue;
 196         return decodedValue;
 197     }
 198
 199     private void loadPixel(final int step, final int offsetX, final int offsetY,
 200                            final int x, final int y, final byte[] pixels,
 201                            final int averageDecodedY, final int averageDecodedU,
 202                            final int averageDecodedV) throws IOException {
 203
 204         final int index = (y * width) + x;
 205
 206         final int halfStep = step / 2;
 207
 208         int parentIndex;
 209         if (offsetX > 0) {
 210             if (offsetY > 0)
 211                 // diagonal approach
 212                 parentIndex = ((y - halfStep) * width) + (x - halfStep);
 213             else
 214                 // take left pixel
 215                 parentIndex = (y * width) + (x - halfStep);
 216         } else
 217             // take upper pixel
 218             parentIndex = ((y - halfStep) * width) + x;
 219
 220         final int colorBufferIndex = index * 3;
 221
 222         final Color color = new Color();
 223         color.y = loadChannel(decodedYRangeMap, decodedYMap,
 224                 approximator.yTable, averageDecodedY, index, parentIndex);
 225         color.u = loadChannel(decodedURangeMap, decodedUMap,
 226                 approximator.uTable, averageDecodedU, index, parentIndex);
 227         color.v = loadChannel(decodedVRangeMap, decodedVMap,
 228                 approximator.vTable, averageDecodedV, index, parentIndex);
 229
 230         color.YUV2RGB();
 231
 232         pixels[colorBufferIndex] = (byte) color.r;
 233         pixels[colorBufferIndex + 1] = (byte) color.g;
 234         pixels[colorBufferIndex + 2] = (byte) color.b;
 235
 236     }
 237
 238 }