2 * Imagesqueeze - Image codec optimized for photos.
3 * Copyright (C) 2012, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
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.
10 package eu.svjatoslav.imagesqueeze.codec;
13 * Compressed image pixels decoder.
16 import java.awt.image.DataBufferByte;
17 import java.awt.image.WritableRaster;
18 import java.io.IOException;
20 import eu.svjatoslav.commons.data.BitInputStream;
22 public class ImageDecoder {
27 byte[] decodedYRangeMap;
30 byte[] decodedURangeMap;
33 byte[] decodedVRangeMap;
36 Color tmpColor = new Color();
38 Approximator approximator;
39 BitInputStream bitInputStream;
41 ColorStats colorStats = new ColorStats();
42 OperatingContext context = new OperatingContext();
44 public ImageDecoder(final Image image, final BitInputStream bitInputStream) {
45 approximator = new Approximator();
48 this.bitInputStream = bitInputStream;
50 width = image.metaData.width;
51 height = image.metaData.height;
53 decodedYRangeMap = new byte[width * height];
54 decodedYRangeMap[0] = (byte) (255);
55 decodedYMap = new byte[width * height];
57 decodedURangeMap = new byte[width * height];
58 decodedURangeMap[0] = (byte) (255);
59 decodedUMap = new byte[width * height];
61 decodedVRangeMap = new byte[width * height];
62 decodedVRangeMap[0] = (byte) (255);
63 decodedVMap = new byte[width * height];
67 public void decode() throws IOException {
68 approximator.load(bitInputStream);
69 approximator.computeLookupTables();
71 final WritableRaster raster = image.bufferedImage.getRaster();
72 final DataBufferByte dbi = (DataBufferByte) raster.getDataBuffer();
73 final byte[] pixels = dbi.getData();
75 // load top-, left-most pixel.
76 decodedYMap[0] = (byte) bitInputStream.readBits(8);
77 decodedUMap[0] = (byte) bitInputStream.readBits(8);
78 decodedVMap[0] = (byte) bitInputStream.readBits(8);
80 final Color color = new Color();
81 color.y = ImageEncoder.byteToInt(decodedYMap[0]);
82 color.u = ImageEncoder.byteToInt(decodedUMap[0]);
83 color.v = ImageEncoder.byteToInt(decodedVMap[0]);
87 pixels[0] = (byte) color.r;
88 pixels[0 + 1] = (byte) color.g;
89 pixels[0 + 2] = (byte) color.b;
91 // detect initial step
95 largestDimension = width;
97 largestDimension = height;
100 while (initialStep < largestDimension) {
101 initialStep = initialStep * 2;
104 grid(initialStep, pixels);
107 public void grid(final int step, final byte[] pixels) throws IOException {
109 gridDiagonal(step / 2, step / 2, step, pixels);
110 gridSquare(step / 2, 0, step, pixels);
111 gridSquare(0, step / 2, step, pixels);
114 grid(step / 2, pixels);
117 public void gridDiagonal(final int offsetX, final int offsetY,
118 final int step, final byte[] pixels) throws IOException {
120 for (int y = offsetY; y < height; y = y + step) {
121 for (int x = offsetX; x < width; x = x + step) {
123 final int halfStep = step / 2;
125 context.initialize(image, decodedYMap, decodedUMap, decodedVMap);
126 context.measureNeighborEncode(x - halfStep, y - halfStep);
127 context.measureNeighborEncode(x + halfStep, y - halfStep);
128 context.measureNeighborEncode(x - halfStep, y + halfStep);
129 context.measureNeighborEncode(x + halfStep, y + halfStep);
131 loadPixel(step, offsetX, offsetY, x, y, pixels,
132 context.colorStats.getAverageY(),
133 context.colorStats.getAverageU(),
134 context.colorStats.getAverageV());
140 public void gridSquare(final int offsetX, final int offsetY,
141 final int step, final byte[] pixels) throws IOException {
143 for (int y = offsetY; y < height; y = y + step) {
144 for (int x = offsetX; x < width; x = x + step) {
146 final int halfStep = step / 2;
148 context.initialize(image, decodedYMap, decodedUMap, decodedVMap);
149 context.measureNeighborEncode(x - halfStep, y);
150 context.measureNeighborEncode(x + halfStep, y);
151 context.measureNeighborEncode(x, y - halfStep);
152 context.measureNeighborEncode(x, y + halfStep);
154 loadPixel(step, offsetX, offsetY, x, y, pixels,
155 context.colorStats.getAverageY(),
156 context.colorStats.getAverageU(),
157 context.colorStats.getAverageV());
163 private int loadChannel(final byte[] decodedRangeMap,
164 final byte[] decodedMap, final Table table,
165 final int averageDecodedValue, final int index,
166 final int parentIndex) throws IOException {
167 int decodedValue = averageDecodedValue;
169 final int inheritedRange = ImageEncoder
170 .byteToInt(decodedRangeMap[parentIndex]);
171 int computedRange = inheritedRange;
173 final int bitCount = table.proposeBitcountForRange(inheritedRange);
174 int computedRangeBitCount = 0;
177 final int rangeDecreases = bitInputStream.readBits(1);
178 if (rangeDecreases != 0) {
179 computedRange = table.proposeDecreasedRange(inheritedRange);
182 decodedRangeMap[index] = (byte) computedRange;
183 computedRangeBitCount = table
184 .proposeBitcountForRange(computedRange);
186 if (computedRangeBitCount > 0) {
188 final int encodedDifference = bitInputStream
189 .readBits(computedRangeBitCount);
191 final int decodedDifference = ImageEncoder
192 .decodeValueFromGivenBits(encodedDifference,
193 computedRange, computedRangeBitCount);
195 decodedValue = averageDecodedValue - decodedDifference;
196 if (decodedValue > 255)
198 if (decodedValue < 0)
202 decodedRangeMap[index] = (byte) inheritedRange;
204 decodedMap[index] = (byte) decodedValue;
208 public void loadPixel(final int step, final int offsetX, final int offsetY,
209 final int x, final int y, final byte[] pixels,
210 final int averageDecodedY, final int averageDecodedU,
211 final int averageDecodedV) throws IOException {
213 final int index = (y * width) + x;
215 final int halfStep = step / 2;
221 parentIndex = ((y - halfStep) * width) + (x - halfStep);
224 parentIndex = (y * width) + (x - halfStep);
228 parentIndex = ((y - halfStep) * width) + x;
231 final int colorBufferIndex = index * 3;
233 final Color color = new Color();
234 color.y = loadChannel(decodedYRangeMap, decodedYMap,
235 approximator.yTable, averageDecodedY, index, parentIndex);
236 color.u = loadChannel(decodedURangeMap, decodedUMap,
237 approximator.uTable, averageDecodedU, index, parentIndex);
238 color.v = loadChannel(decodedVRangeMap, decodedVMap,
239 approximator.vTable, averageDecodedV, index, parentIndex);
243 pixels[colorBufferIndex] = (byte) color.r;
244 pixels[colorBufferIndex + 1] = (byte) color.g;
245 pixels[colorBufferIndex + 2] = (byte) color.b;